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COASTAL CONSERVATION PROJECT

STATUS OF BEACHES AND BAYS IN TRINIDAD

(2004 – 2008)

Prepared by:

JUNIOR DARS AN Senior Research Officer

SUNI L RAMNATH Junior Research Officer

CHRIS TOP HER ALEXIS Junior Research Officer

ENVIRONMENTAL RESEARCH PROGRAMME RES EAR CH PRO JECT , MAR CH 2012

INSTITUTE OF MARINE AFFAIRS Hilltop Lane Chaguaramas or PO Box 3160, Carenage Post Office, Carenage, Trinidad and Tobago

Tel: 868-634-4291/4 Fax: 868-634-4433 Email: [email protected]

mailto:[email protected]

COASTAL CONSERVATION PROJECT STATUS OF BEACHES AND BAYS IN TRINIDAD (2004 – 2008)

Institute of Marine Affairs i

ACKNOWLEDGEMENTS

This report is a collective effort of all staff of the Geology Department and other members

of the Environmental Research Programme. Special considerations are given to the

researchers who conceptualized the Coastal Conservation Project and commenced the

coastal monitoring work.

Thanks to Mrs. Charmaine O’Brien Delpesh who headed the Environmental Research

Programme for the period under review in this report. Her expertise and knowledge of the

coastal environment of Trinidad was critical in leading and guiding research in this

department.

A special thanks to the technicians in the Environmental Research Programme,

Mr. Kevin Khan, Mr. Russell Rajnauth and Mr. Aaron Mohammed, who have collected the

beach profile and littoral data that are presented in this report. Mr. Jonathan Gomez and

Mr. Rennie Peters have also contributed to the data collection.

Thank you to Mr. Adam Jehu and Hamish Asmath for preparation of maps and Mrs.

Charmaine Pontiflette-Douglas and Ms. Lisa Chadee for formatting the document. Special

thanks are extended to Dr. Rahanna Juman for her guidance during the initial stages of this

report.


Institute of Marine Affairs ii

ABSTRACT

The shoreline monitoring component of the Coastal Conservation Project which

commenced in 1988 provides valuable insights on the dynamics of the coastline. The

scientific data are used by government and other agencies in formulating policies and plans

for the coastline. While coastlines of Trinidad and Tobago are monitored under this project,

this report presents only the research conducted in Trinidad during the period 2004 –

2008. The report focuses on the 25 beaches and bays monitored, comprising 64 beach

profiling stations. The report reveals that most of the beaches and bays in Trinidad are in a

state of dynamic equilibrium where the seasonal changes of erosion and accretion

occurring on the beaches revolve around a state of stability.

The beaches on the north coast are less prone to erosion due to the more resilient

metamorphic rocks that form these bays. However, changes in sand elevations due to

normal wave processes do occur. During the period 2004–2008 all beaches monitored on

the north coast experienced a state of dynamic equilibrium with the exception of the east

and west stations at Las Cuevas Bays and the western part of Blanchisseuse Bay.

All east coast beaches also experienced dynamic equilibrium except the southern part of

Cocos Bay. Erosion in this part of the coastline threatened to breach the roadway and

prompted government to construct a 2 km long rip rap revetment as a means of shoreline

protection. This has curbed the erosion in the protected area but to the extreme south

erosion is ongoing at a rate of 2.5 m/yr since 2005.

The beaches on the south coast experienced dynamic equilibrium except at the western

section of Guayaguayare Bay. Erosion in this part of the bay averaged 1.20 m/yr since

2004. This erosion can be attributed to both offshore and onshore open trenching for pipe

laying activities.

The west coast beaches are located within the Gulf of Paria which provides a sheltered

environment. Erosion however was observed at North Chatham which averaged 1.20 m/yr

since 2004. Erosion was also observed at the western section of Guapo Beach in Clifton Hill

during 2006 and 2007. On the south-western peninsula, while Punta del Arenal (Icacos) is

experiencing accretion, Columbus Bay is being eroded. The erosion has prompted property

owners to employ the use of coastal protection measures such as revetments and groins.

This report makes recommendations for modifying the current monitoring regime as well

as highlights further research needs.


Institute of Marine Affairs iii

T A B L E O F C O N T E N T S

Page#

ACKNOWLE DGE MEN TS .......................................................................................................... i

ABS TRACT ............................................................................................................................ ii

1 INTRODUCTION .............................................................................................................. 1

1.1 Background ............................................................................................................................................ 1

1.2 Objectives ................................................................................................................................................ 4

2 SITE DESCRIPTION ........................................................................................................... 6

2.1 North Coast ............................................................................................................................................. 6

2.2 East Coast ................................................................................................................................................ 7

2.3 South Coast ............................................................................................................................................. 8

2.4 West Coast .............................................................................................................................................. 9

3 METHODOLOGY ............................................................................................................ 10

3.1 Data Collection ................................................................................................................................... 10

3.2 Beach Profiles ..................................................................................................................................... 11

3.3 Littorals ................................................................................................................................................ 12

3.4 Grain Size Analysis ........................................................................................................................... 13

4 RESULTS AND DISCUSSION ............................................................................................ 16

4.1 North Coast .......................................................................................................................................... 16

4.1.1 Macqueripe Bay .................................................................................................................. 22

4.1.2 Maracas Bay ........................................................................................................................ 25

4.1.3 Tyrico Bay ............................................................................................................................ 39

4.1.4 Las Cuevas Bay .................................................................................................................... 44

4.1.5 Blanchisseuse Bay ............................................................................................................... 53

4.1.6 Grande Riviere Bay .............................................................................................................. 57

4.1.7 Salybia Bay (Toco) ............................................................................................................... 67

4.2 East Coast ............................................................................................................................................. 71

4.2.1 Guayamara Bay ................................................................................................................... 75

4.2.2 Saline Bay ............................................................................................................................ 79

4.2.3 Cocos Bay ............................................................................................................................ 84

4.2.4 Mayaro Bay ....................................................................................................................... 101

4.3 South Coast ........................................................................................................................................ 108


Institute of Marine Affairs iv

4.3.1 Guayaguayare Bay............................................................................................................. 112

4.3.2 Quinam Bay ....................................................................................................................... 122

4.3.3 Los Iros Bay ....................................................................................................................... 126

4.3.4 Erin Bay ............................................................................................................................. 129

4.3.5 Punta Del Arenal ............................................................................................................... 132

4.4 West Coast ......................................................................................................................................... 135

4.4.1 Columbus Bay .................................................................................................................... 140

4.4.2 Granville Bay ..................................................................................................................... 144

4.4.3 Irois Bay ............................................................................................................................. 147

4.4.4 Guapo Bay ......................................................................................................................... 153

4.4.5 Station Beach - La Brea ..................................................................................................... 169

4.4.6 Dhein’s Bay ........................................................................................................................ 176

4.4.7 Chagville Bay ..................................................................................................................... 179

5 CONCLUSION ............................................................................................................... 187

6 RECOMMENDATIONS .................................................................................................. 192

7 REFERENCES ................................................................................................................ 198


Institute of Marine Affairs v

L I S T O F F I G U R E S

page #

Figure 1: Map of the Caribbean showing the Location of Trinidad ............................................... 6

Figure 2: Coastal Classification Map of Trinidad ............................................................................ 8

Figure 3: Location of IMA Beach Monitoring Stations in Trinidad .............................................. 10

Figure 4: Cross Section of a Beach ................................................................................................. 11

Figure 5: Ternary diagram of grain size nomenclature for sediments containing gravel,

sand and mud (Source: Folk 1974) ................................................................................ 15

Figure 6: IKONOS image of Macqueripe Bay showing IMA Station location (2007) ................. 22

Figure 7: Selected beach profiles for Macqueripe Bay for the period 2004 – 2008................... 24

Figure 8: Maximum - Minimum sediment elevations along the beach profile for

Macqueripe Bay for the period 2004 – 2008 ................................................................ 24

Figure 9: IKONOS image of Maracas Bay showing Station locations (2007) .............................. 25

Figure 10: Sediment grain-size distributions for Maracas Bay Station 1 ........................................ 27

Figure 11: Selected beach profiles for Maracas Bay Station 1 (west) for the period 2004 –

2008.................................................................................................................................. 27

Figure 12: Plot of Beach Width and Volume vs. Number of days for Maracas Bay Station 1

(west) for the period February 1985 – October 2008.................................................. 28

Figure 13: Sediment grain-size distributions for Maracas Bay Station 2 ..................................... 30

Figure 14: Selected beach profiles for Maracas Bay Station 2 (central) for the period

2004 – 2008 ..................................................................................................................... 30


(central) for the period March 1985 – October 2008 ................................................... 31

Figure 16: Maximum and Minimum beach elevations for Maracas Bay Station 2 (central)

for the period 2004 – 2008 ............................................................................................. 32



2004 – 2008 ..................................................................................................................... 34


(central) for the period March 1985 – October 2008 ................................................... 35


Figure 21: Selected beach profiles for Maracas Bay Station 4 (east) for the period 2004 –

2008.................................................................................................................................. 37


(east) for the period February 1995 – October 2008 ................................................... 38

Figure 23: IKONOS Image of Tyrico Bay showing station locations (2007) ................................. 39

Figure 24: Sediment grain-size distributions for Tyrico Bay Station 1 ......................................... 41

Figure 25: Selected beach profiles for Tyrico Bay Station 1 (west) for the period 2004 –

2008.................................................................................................................................. 41

Figure 26: Sediment grain-size distributions for Tyrico Bay Station 2 ......................................... 43


Institute of Marine Affairs vi

Figure 27: Selected beach profiles for Tyrico Bay Station 2 (east) for the period 2004 –

2008.................................................................................................................................. 44

Figure 28: IKONOS image of Las Cuevas Bay showing Station locations (2007) ......................... 45

Figure 29: Sediment grain-size distributions for Las Cuevas Bay Station 1 ................................. 47

Figure 30: Selected beach profiles for Las Cuevas Bay Station 1 (west) for the period

2004 – 2008 ..................................................................................................................... 47


Figure 32: Selected beach profiles for Las Cuevas Bay Station 2 (east) for the period 2004

– 2008 ............................................................................................................................... 49

Figure 33: Plot of Beach Width and Volume vs. Number of days for Las Cuevas Bay

Station 2 (central) for the period March 1985 – October 2008................................... 50

Figure 34: Maximum and Minimum beach elevations for Las Cuevas Bay Station 2

(central) for the period 2004 – 2008 ............................................................................. 51


Figure 36: Selected beach profiles for Las Cuevas Bay Station 3 (east) for the period 2004

– 2008 ............................................................................................................................... 53

Figure 37: IKONOS image of Blanchisseuse Bay showing Station Location (2007) ..................... 54

Figure 38: Sediment grain-size distributions for Blanchisseuse Station 1 ................................... 55

Figure 39: Selected beach profiles for Blanchisseuse Bay Station 2 (west) for the period

2004 – 2008 ..................................................................................................................... 56

Figure 40: Plot of Beach Width and Volume vs. Number of days for Las Cuevas Bay

Station 2 (central) for the period March 1985 – October 2008................................... 57

Figure 41: IKONOS image of Grande Riviere Bay showing Station locations (2007) .................. 58

Figure 42: Sediment grain-size distributions for Grand Riviere Station 1 ................................... 60

Figure 43: Selected beach profiles for Grande Riviere Bay Station 1 (west) for the period

2004 – 2008 ..................................................................................................................... 60


Figure 45: Selected beach profiles for Grande Riviere Bay Station 2 (central) for the

period 2004 – 2008 ......................................................................................................... 62


Figure 47: Selected beach profiles for Grande Riviere Bay Station 3 (central) for the

period 2004 – 2008 ......................................................................................................... 65


Figure 49: Selected beach profiles for Grande Riviere Bay Station 4 (east) for the period

2004 – 2008 ..................................................................................................................... 67

Figure 50: IKONOS image of Salybia Bay showing Station location (2007) ................................. 68

Figure 51: Sediment grain-size distributions for Salybia Station 2 ............................................... 69

Figure 52: Selected beach profiles for Salybia Bay for the period 2004 – 2008 .......................... 70

Figure 53: IKONOS image of Guayamara Bay showing Station location (2007) .......................... 76

Figure 54: Sediment grain-size distributions for Guayamara Bay ................................................ 78

Figure 55: Selected beach profiles for Guayamara Bay for the period 2004 – 2008 ................... 78


Institute of Marine Affairs vii

Figure 56: Plot of Beach Width and Volume vs. Number of days for Guayamara Bay for the

period March 1985 – April 2008 .................................................................................... 79

Figure 57: IKONOS image of Saline Bay showing Station locations (2007) .................................. 80

Figure 58: Sediment grain-size distributions for Saline Bay Station 1 ......................................... 82

Figure 59: Selected beach profiles for Saline Bay Station 1 (east) for the period 2004 –

2008.................................................................................................................................. 82

Figure 60: Selected beach profiles for Saline Bay Station 2 (west) for the period 2004 –

2008.................................................................................................................................. 84

Figure 61: IKONOS image of Cocos Bay showing Station locations (2007) .................................. 85

Figure 62: Sediment grain-size distributions for Cocos Bay Station 1 .......................................... 87

Figure 63: Selected beach profiles for Cocos Station 1 (north) for the period 2004 – 2008....... 87

Figure 64: Plot of Beach Width and Volume vs. Number of days for Cocos Bay Station 1

for the period March 1985 – April 2008 ....................................................................... 88


Figure 66: Selected beach profiles for Cocos Station 2 (central) for the period 2004 –

2008.................................................................................................................................. 90


Figure 68: Selected beach profiles for Cocos Station 3 (south) for the period 2004 – 2008 ...... 93


(central) for the period February 1990 – October 2008 .............................................. 94

Figure 70: Maximum and Minimum beach elevations for Cocos Bay Station 3 (central)

2004 – 2008 ..................................................................................................................... 95


Figure 72: Selected beach profiles for Cocos Station 4 (south) for the period 2004 – 2008 ...... 97


Figure 74: Selected beach profiles for Cocos Station 5 (south) for the period 2004 – 2008. .... 100


(south) for the period January 1992 – November 2008 ............................................ 100

Figure 76: IKONOS image of Mayaro Bay showing Station locations (2007) ............................. 101

Figure 77: Selected beach profiles for Mayaro Bay Station 1 (north) for the period 2004 –

2007................................................................................................................................ 103

Figure 78: Sediment grain-size distributions for Mayaro Bay Station 2 ..................................... 104

Figure 79: Selected beach profiles for Mayaro Station 2 (central) for the period 2004 –

2008................................................................................................................................ 105

Figure 80: Plot of Beach Width and Volume vs. Number of days for Mayaro Bay Station 2

(central) for the period March 1985 – April 2008 ...................................................... 106

Figure 81: Sediment grain-size distributions for Mayaro Bay Station 3 ..................................... 107

Figure 82: Selected beach profiles for Mayaro Station 3 (south) for the period 2004 –

2008................................................................................................................................ 108

Figure 83: IKONOS image of Guayaguayare Bay showing Stations location (2007) .................. 112

Figure 84: Sediment grain-size distributions for Guayaguayare Bay Station 1 ......................... 114


Institute of Marine Affairs viii

Figure 85: Selected beach profiles for Guayaguayare Bay Station 1 (west) for the period

2004 – 2008 ................................................................................................................... 115

Figure 86: Maximum - Minimum elevations of Guayaguayare Bay Station 1 (west) for the

period 2004 – 2008 ....................................................................................................... 116

Figure 87: Plot of Beach Width vs. Number of days for Guayaguayare Bay Station 1 (west)

for the period October 1996 – October 2008 .............................................................. 116


Figure 89: Beach at Guayaguayare Bay Station 2 in the central part of the Bay ........................ 119

Figure 90: Plot of Beach Width vs. Number of days for Guayaguayare Bay Station 2

(central) for the period February 1985 – October 2008 ............................................ 119


Figure 92: Selected beach profiles for Guayaguayare Bay Station 3 (east) for the period

2004 – 2008 ................................................................................................................... 122

Figure 93: IKONOS image of Quinam Bay showing Station location (2007) .............................. 123

Figure 94: Sediment grain-size distributions for Quinam Bay .................................................... 125

Figure 95: Selected beach profiles for Quinam Bay for the period 2004 – 2008 ....................... 126

Figure 96: IKONOS image of Los Iros Bay showing Station location (2007) .............................. 127

Figure 97: Sediment grain-size distributions for Los Iros Bay .................................................... 128

Figure 98: Selected beach profiles for Los Iros Bay for the period 2004 – 2008 ....................... 129

Figure 99: IKONOS image of Erin Bay showing Station location (2007) .................................... 130

Figure 100: Sediment grain-size distributions for Erin Bay .......................................................... 131

Figure 101: Selected beach profiles for Erin Bay for the period 2004 – 2008 ............................. 132

Figure 102: IKONOS image of Punta del Arenal showing Station location (2007) ....................... 133

Figure 103: Sediment grain-size distributions for Punta del Arenal ............................................. 134

Figure 104: Selected beach profiles for Punta del Arenal for the period 2004 – 2008 ................ 135

Figure 105: IKONOS image of Columbus Bay showing Station location (2007)........................... 140

Figure 106: Sediment grain-size distributions for Columbus Bay Station 7 ................................. 142

Figure 107: Selected beach profiles for Columbus Bay for the period 2004 – 2008 .................... 143

Figure 108: Maximum - Minimum elevations of Columbus Bay for the period 2004 – 2008 ..... 144

Figure 109: IKONOS image of Granville Bay showing Station location (2007) ............................ 145

Figure 110: Sediment grain-size distributions for Granville Bay .................................................. 146

Figure 111: Selected beach profiles for Granville Bay for the period 2004 – 2008 ..................... 147

Figure 112: IKONOS image of Irois Bay showing Station location (2007) .................................... 148

Figure 113: Sediment grain-size distributions for Irois Bay Station 1b ........................................ 150

Figure 114: Selected beach profiles for Irois Bay (Cap de Ville) for the period 2004 – 2008 ..... 151

Figure 115: Selected beach profiles for Irois Bay (North Chatham) for the period 2004 –

2008................................................................................................................................ 153

Figure 116: IKONOS image of Guapo Bay showing IMA Stations locations (2007) ..................... 154

Figure 117: Sediment grain-size distributions for Guapo Bay Station 1 ....................................... 156

Figure 118: Selected beach profiles for Guapo Bay (Station 1) for the period 2004 – 2008 ....... 156

Figure 119: Sediment grain-size distributions for Guapo Bay Station 4A .................................... 158

Figure 120: Selected beach profiles for Guapo Bay (Station 4a) for the period 2004 – 2008 ..... 159


Institute of Marine Affairs ix

Figure 121: Sediment grain-size distributions for Guapo Bay Station CH1 .................................. 161

Figure 122: Selected beach profiles for Guapo Bay (Station CH 1) for the period 2004 –

2008................................................................................................................................ 161

Figure 123: Sediment grain-size distributions for Guapo Bay Station 4b ..................................... 163

Figure 124: Selected beach profiles for Guapo Bay (Station 4b) for the period 2004 – 2008..... 163

Figure 125: Sediment grain-size distributions for Guapo Bay Station 5 ....................................... 165

Figure 126: Selected beach profiles for Guapo Bay (Station 5) for the period 2004 – 2008 ....... 165

Figure 127: Plot of Beach Width vs. Number of days for Guapo Bay Station 5 for the period

June 1987 – July 2008 ................................................................................................... 166

Figure 128: Selected beach profiles for Guapo Bay (Station 5a) for the period 2004 – 2008 ..... 168

Figure 129: Plot of Beach Width and Volume vs. Number of days for Guapo Bay Station 5A

for the period March 1985 – April 2008 ..................................................................... 169

Figure 130: IKONOS image of Station Beach, La Brea showing Stations location (2007) ........... 170

Figure 131: Sediment grain-size distributions for La Brea Bay Station 2 ..................................... 172

Figure 132: Selected beach profiles for Station Beach La Brea (Station 2) for the period

2004 – 2008 ................................................................................................................... 172

Figure 133: Plot of Beach Width and Volume vs. Number of days for Station Beach, La Brea

Station 2 (central) for the period July 1991 – November 2008 ................................. 173

Figure 134: Sediment grain-size distributions for La Brea Bay Station 3 ..................................... 175

Figure 135: Selected beach profiles for Station Beach La Brea (Station 3) for the period

2004 – 2008 ................................................................................................................... 175

Figure 136: Plot of Beach Width and Volume vs. Number of days for Station Beach, La Brea

Station 3 (central) for the period January 1994 – June 2008 .................................... 176

Figure 137: IKONOS image of Dhein’s Bay showing Station location (2007) ............................... 177

Figure 138: Sediment grain-size distributions for Dhein’s Bay ..................................................... 178

Figure 139: Selected beach profiles for Dhein’s Bay for the period 2004 – 2008 ........................ 179

Figure 140: IKONOS image of Chagville Bay showing Stations location (2007) .......................... 180

Figure 141: Sediment grain-size distributions for Chagville Station 1 ......................................... 182

Figure 142: Selected beach profiles for Chagville (Station 1 - West) for the period 2004 –

2008................................................................................................................................ 183

Figure 143: Plot of Beach Width and Volume vs. Number of days for Chagville Beach

Station 1 (west) for the period February 1985 – April 2008..................................... 183

Figure 144: Sediment grain-size distributions for Chagville Station 3 ......................................... 185

Figure 145: Selected beach profiles for Chagville (Station 3 - Central) for the period 2004

– 2008 ............................................................................................................................. 186

Figure 146: Status of Coastline Map of Trinidad based on study conducted during 2004 –

2008. ............................................................................................................................... 191


Institute of Marine Affairs x

L I S T O F T A B L E S

page #

Table 1: Description of Sorting Values used in Grain Size Analysis ........................................... 14

Table 2: Description of Kurtosis Values used in Grain Size Analysis ......................................... 14

Table 3: Description of Skewness Values used in Grain Size Analysis ...................................... 14

Table 4: Summary Littoral processes for North Coast Beaches of Trinidad for the

period 2004 – 2008 ......................................................................................................... 17

Table 5: Summary Grain Size for North Coast Beaches of Trinidad .......................................... 18

Table 6: Shoreline stability status of North Coast Beaches of Trinidad for the period

2004 – 2008 ..................................................................................................................... 21

Table 7: Summary Littoral Processes for East Coast Beaches of Trinidad for the period

2004.................................................................................................................................. 72

Table 8: Summary grain size for East Coast Beaches of Trinidad .............................................. 73

Table 9: Summary Shoreline stability status of East Coast Beaches of Trinidad for the

period 2004- 2008 .......................................................................................................... 75

Table 10: Summary Littoral Processes for South Coast Beaches of Trinidad for the period

2004 – 2008 ................................................................................................................... 109

Table 11: Summary grain size for South Coast Beaches of Trinidad ......................................... 110

Table 12: Summary shoreline stability status of South Coast beaches of Trinidad for the

period 2004 – 2008 ....................................................................................................... 111

Table 13: Summary Littoral Processes for West Coast beaches of Trinidad and Tobago

for the period 2004 – 2008 ........................................................................................... 136

Table 14: Summary grain size for West Coast Beaches of Trinidad .......................................... 137

Table 15: Shoreline stability of West Coast beaches of Trinidad for the period 2004 –

2008................................................................................................................................ 139

Table 16: Beaches and Bays to be monitored Bi-annually. ......................................................... 193

Table 17: Beaches and Bays to be monitored monthly. .............................................................. 193

Table 18: Beaches and Bays to be monitored quarterly. ............................................................ 195

Table 19: New monitoring stations to be established (to be monitored quarterly)................. 196


Institute of Marine Affairs xi

L I S T O F P L A T E S

page #

Plate 1: Beach at Macqueripe Bay showing recently constructed seawall (April 2008) ........ 23

Plate 2: Maracas Bay Station 1 easterly view showing berm (July 2008) ................................ 26

Plate 3: Maracas Bay Station 2 (July 2008) ................................................................................. 29

Plate 4: Maracas Bay Station 3 showing wide gently sloping beach (July 2008)..................... 33

Plate 5: Beach at Maracas Bay Station 4 (July 2008) ................................................................. 36

Plate 6: Tyrico Bay Station 1 west showing cobble cuspates and a gently sloping beach

(September 2007) ........................................................................................................... 40

Plate 7: Eastern Section of Tyrico Bay showing accumulation of cobbles forming

cuspates (September 2007) ........................................................................................... 42

Plate 8: West section of Las Cuevas Bay (Station 1) showing the wide berm

(September 2007) ........................................................................................................... 46

Plate 9: Beach at the central section of Las Cuevas Bay (Station 2) showing eroding

scarp (September 2007) ................................................................................................. 48

Plate 10: Las Cuevas Bay Station 3 east showing wide gently sloping beach (July 2008) ........ 51

Plate 11: West section of Blanchisseuse Bay (Station 2) showing the wide berm

(September 2007) ........................................................................................................... 54

Plate 12: West section of Grande Riviere Bay (Station 1) showing rocky backshore and

narrow berm. (September 2007) ................................................................................... 59

Plate 13: West section of Grande Riviere Bay (Station 2) showing moderately sloping

beach (September 2007) ................................................................................................ 61

Plate 14: Beach at Grande Riviere showing well developed berm and river outflow

channel (September 2007) ............................................................................................. 63

Plate 15: Grande Riviere Bay Station 4 showing wide beach and distinct berm crest

(September 2007) ........................................................................................................... 65

Plate 16: Beach at Salybia Bay, Toco (October 2007) .................................................................. 68

Plate 17: Guayamara Bay, showing wide berm (October 2007) ................................................. 77

Plate 18: Beach at Saline Bay Station 1 (October 2007) .............................................................. 81

Plate 19: Beach at Saline Bay Station 2 (October 2007) .............................................................. 83

Plate 20: Cocos Bay Station 1 North, showing eroding backshore (August 2007) .................... 86

Plate 21: Cocos Bay Station 2 Central, showing wide gently sloping beach (August 2007) ..... 89

Plate 22: Cocos Bay Station 3 Central, showing wide gently sloping beach covered with

shells along the upper-mid beach (August 2007)......................................................... 91

Plate 23: Beach at Cocos Bay Station 4 showing Rip Rap revetment and gently sloping

beach (April 2008) .......................................................................................................... 96

Plate 24: Beach at Cocos Bay Station 5 showing fallen coconut trees as a result of

erosion. (April 2008) ...................................................................................................... 98

Plate 25: Beach at North Mayaro Bay Station 1, (September 2004) ......................................... 102

Plate 26: Mayaro Bay Station 2, showing gently sloping wide berm (February 2007) ........... 103


Institute of Marine Affairs xii

Plate 27: Mayaro Bay Station 3, showing gently sloping wide berm (February 2007) ........... 106

Plate 28: Beach at Guayaguayare Bay Station 1 showing beach face and coconut tress

falling over due to erosion at the base (February 2007) ........................................... 113

Plate 29: Guayaguayare Bay Station 2, showing gently sloping beach (July 2007) ................. 117

Plate 30: Guayaguayare Bay Station 3, showing gently sloping beach (July 2007) ................. 120

Plate 31: Westerly view of beach at Quinam Bay showing eroding cliffs west of car park

(February 2008) ............................................................................................................ 124

Plate 32: Easterly view of beach at Los Iros Bay showing wide gently sloping beach

(October 2007) .............................................................................................................. 127

Plate 33: Westerly view of beach at Erin Bay showing sand spit (February 2007) ................ 130

Plate 34: Punta del Arenal showing vegetation and wide gently sloping beach (February

2006) .............................................................................................................................. 133

Plate 35: Southerly view of Columbus Bay (February 2007) .................................................... 141

Plate 36: Granville Bay showing gently sloping beach and backshore cliff (January

2008) .............................................................................................................................. 145

Plate 37: Easterly view of Irois Bay Station 1b at Cap de Ville showing rubble in the

backshore as coastal protection (July 2007) ............................................................... 149

Plate 38: Westerly view of Irois Bay Station 10 at North Chatham showing wide berm

and eroding backshore cliffs, inset shows close up of eroding cliffs. (July 2007) .... 152

Plate 39: Station 1 Guapo Bay showing low gradient beach and low wave energy

environment (July 2008) .............................................................................................. 155

Plate 40: Station 4a Guapo Bay showing low topography of backshore and gently

sloping beach (July 2008) ............................................................................................. 157

Plate 41: Station CH 1 at Guapo Bay showing gently sloping beach (February 2007) ............ 160

Plate 42: Station 4b Guapo Bay showing gently sloping beach and backshore vegetation

(February 2007) ............................................................................................................ 162

Plate 43: Guapo Beach Station 5, Clifton Hill showing gently sloping beach (July 2007) ....... 164

Plate 44: Westernmost on Guapo Beach, Clifton Hill showing offshore breakwater (July

2007) .............................................................................................................................. 167

Plate 45: Station Beach, La Brea, (Station 2) showing flat backshore and wide beach

(July 2007) ..................................................................................................................... 171

Plate 46: Station 3 (west) Station Beach, La Brea showing wide beach (January 2007) ........ 174

Plate 47: Dhein’s Bay, showing narrow cobble/pebble beach (July 2007) .............................. 177

Plate 48: Chagville Bay Station 1, showing narrow beach and low backshore cliff Station

3 (July 2007) .................................................................................................................. 181

Plate 49: Chagville Bay Station 3, showing (July 2007) ............................................................. 184


Institute of Marine Affairs 1 | P a g e

1 INTRODUCTION

1.1 BACKGROUND

The coastal environment, also called littoral zone, can be defined as the area lying at the

interface between the land and the sea. Beaches occur along the interface between land and

sea within the coastal zone. Beaches and coastal dunes constitute the most significant

accumulations of sub-aerially exposed sediment along coasts. While beaches are composed

of material ranging from fine sand to boulders, most consist of sand, shingle or sand-

shingle mixed beaches. They are dynamic coastal features which respond to storms, wind,

waves, currents and tides differently dependent on its geology. For example, where the

coastal geology is resistant to wave attack, erosion may occur at a reduced rate and where

it is more susceptible, it may be eroded at a faster rate (Van Rijn, 1998).

Beaches are natural resources which have great aesthetic appeal and recreational value.

The natural resources of beaches and bays serve a variety of uses, such as;

1. Biotic and abiotic resources e.g. marine life and sand

2. Recreation

3. Coastal protection buffers

4. Economic value (IMA, 2004).

Notwithstanding the protection by reefs, beaches are generally the primary defenses for

any coastal development. Beaches however are damaged by sand removal, improper

building of coastal protection structures and any activity that prevents new sediment

sources from replenishing them (Reeve et al, 2004).

Factors that affect the ability of the coastal region to resist the erosive effects of wind,

waves and surface run-off are the presence of coastal vegetation, offshore reefs, sea grass

beds and mangroves (Cambers, 1998). Areas consisting of unconsolidated sediment will be

more susceptible to erosion than those where the beach is backed by more resistant rocks

(Saunders, 1998).

As the beach is eroded, littoral drift transports the sediment either along or across the

shoreline. Sediment transported along the shoreline may change the orientation of the bay.

Sediment transported across the shoreline may either form sand bars or may be deposited

over the continental slope. Sediment which is deposited over the slope cannot return to

the beach and sediment forming the sandbars may or may not return with seasonal

changes (Van Rijn, 1998).



Generally, shorelines can be swash or drift aligned. Most shorelines naturally align

themselves parallel to the predominant wave direction although other factors are

contributory. Shorelines form and orient themselves based on the movement of sediment

within the system; either alongshore or cross-shore. On swash dominated coastlines, the

shoreline is oriented near parallel to the oncoming wave crests. On drift-aligned coasts, the

shoreline is oriented near parallel to the line of dominating longshore sediment transport

which is induced by obliquely incident waves (Reeve et al, 2004).

The general activity of waves varies seasonally. Wave activity is greater during the winter

period from November to April which results from intense mid-latitude storms in the

North Atlantic Ocean generating swell waves. These swell waves have higher energy,

increased breaker heights, shorter wave periods. These swell waves affect the north, east

and west coasts of the Caribbean islands (Cambers, 1998).

During the summer season (May–October) the beach undergoes accretion due to the lower

wave energy and longer wave periods, but in the winter season (November–April) higher

wave energy and shorter wave periods erode the beach (Cambers, 2004). However, this

seasonal beach response to external forcing mechanisms is not a fixed phenomenon on the

east coast beaches of Trinidad (Darsan, 2012). When these two cycles of erosion and

accretion occur without any long term deleterious effects on the beach, a state of dynamic

equilibrium (DE) is said to exist. Dynamic Equilibrium or a state of relative stability is also

achieved when the shorelines have adjusted (become parallel) to the prevailing pattern of

the waves (Reeve et al, 2004).

Beaches can either be classified as being in a state of erosion, accretion or dynamic

equilibrium (D.E.). Erosion can occur either horizontally where the backshore recedes

landward or vertically where the sand elevation decreases along the beach face. Cocos Bay

for example experiences high rates of coastal erosion both horizontally and vertically,

being exposed to the high energy environment of the Atlantic Ocean (Darsan, 2005a,

2005b, 2012). Accretion however occurs where there is an increase in sediment on the

beach face which can extend the beach horizontally increasing the width of the beach

(Van Rijn, 1998). Beaches undergo both erosion and accretion cycles during the rise and

fall of the tides, changes in the moon cycles between spring and spring phases, and during

the summer and winter seasons.

Coastal land is of great value and in high demand. Stable beaches have no net loss of

sediment although their profiles change during the year (Cambers, 1998). In addition to

this, other beaches may be accreting or eroding where there is net gain or net loss of

sediment respectively. These beaches which accrete and erode are not yet stable. Beaches

naturally configure themselves to wave approach where littoral drift becomes minimal or

nil (Reeve et al, 2004).



Trinidad and Tobago together with other Small Island Developing States (SIDS) have

limited land space. Their coasts have been and are subjected to erosion whether natural or

human induced. Coastal erosion is a major problem experienced in many areas of the

world. Erosion undermines shoreline structures whether commercial, residential or even

coastal defenses. It can remove coastal agricultural land and destroy recreational areas and

habitats (Cambers, 1998). Localized tectonic events and land subsidence may result in

accelerated erosion rates especially during hurricane periods (Sharp and Hill, 1995). This

can be further exacerbated by sea level rise as the waves travel with increased energy and

break further inland. The Intergovernmental Panel on Climate Change (IPCC) reported that

sea level rise may be 0.06 m/yr in the twenty-first century (IPCC, 2007).

Beaches are the sites of natural and anthropogenic activities some of which impact the

country’s economy. A natural activity which occurs on some beaches is that of turtles

nesting. Nesting of leatherback turtles (Dermochelys coriacea) occur along the north, north-

east and east coasts of Trinidad. Turtle nesting contribute significantly to the eco-tourism

product in Trinidad.

Another natural process impacting beaches is that of heavy seas or storm conditions. Under

these conditions the beach is impacted by waves with increased energy and as a result,

they remove sediment from the shoreline. This sediment may be transported offshore to be

re-deposited when normal conditions resume (Didenkulova et al, 2006). Such an event

occurred in October 2005 at Maracas Bay.

Anthropogenic activities on beaches include recreation, trenching and pipe laying which is

associated with the oil and gas industry (IMA, 2003), landing of telecommunication

network cables (IMA 1993) and the construction of coastal protection structures. The

positioning of these pipelines and cables is important. It has been determined that the safe

depth for the burial of these pipelines and cables is at least 2 m below the lowest elevation

of the sand, so that in the event of storms or hurricanes they have a reduced probability of

being exposed (IMA, 1993).

In some instances coastal protection structures are needed for the shoreline. Numerical

models can be used to compare the wave regime pre and post pipeline to determine if any

changes in the coastal processes would impact the shoreline morphology positively

(accretion) or negatively (erosion). In addition to beach profiling, it is recommended that

bathymetric surveys be undertaken to determine if the area has achieved equilibrium with

the coastal processes (IMA, 2003).

Hard coastal protection structures have been utilized to mitigate erosion in some areas in

Trinidad and Tobago. One such area is La Brea where a seawall was constructed to protect

the land from the erosive force of the waves (IMA, 1993a). IMA found that waves

converged at a point along this bay, resulting in erosion of bluffs. The study determined

that the depth of the foundation of the seawall should be lower than the lowest elevation of



the sand, so that it would be protected from wave reflection off the seawall and the

corresponding scour effect.

Although coastal protection structures are designed to prevent erosion, some poorly

designed structures exacerbate the effects of erosion, e.g. four groins constructed within

Los Iros Bay to prevent erosion caused rip currents to develop which transported sediment

offshore and resulted in reduction of the beach width (George, 1986)

Early erosion studies by Deane (1971) investigated coastal erosion from Point Fortin to Los

Gallos based on the geological outcroppings on the coastline. Erosion rates between Los

Gallos and Fullerton were found to be negligible where the Morne L’Enfer sandstone

outcrops on the coastline. Erosion was observed at Cedros Point, Punta del Morro and

Point Rouge where there were porcellanite outcroppings and this was mainly attributed to

abrasion from normal wave conditions.

Between Point Fortin and Point Ligoure, erosion was observed within the Cruse Formation.

Erosion was also observed between Point Ligoure and Cap de Ville. The outcropping

between Fullerton and Bonasse village consists of the Morne L’Enfer silt and clay, and has

been experiencing long term erosion. Extremely high erosion rates were observed at

Columbus Bay due to the complexity of the wave current patterns at this bay. Deane (1971)

recommended that a revetment together with short groynes be constructed at Cap de Ville,

and a long groyne at Columbus Bay. He also suggested the formulation of a policy for the

construction of coastal protection measures for the entire south western region of the

country.

1.2 OBJECTIVES

The IMA has been monitoring beaches and bays in Trinidad and Tobago since 1988 under

the Coastal Dynamics Component of the Coastal Conservation Project. The goals of this

project are:-

To determine coastal stability trends for Trinidad and Tobago in term of its

erosion/accretion rates.

To assess the effects of coastal development on the shorelines of Trinidad and

Tobago.

To compile a database of sediment properties in terms of its grain size for beaches

monitored.



The data generated from this monitoring project have been used to advise both public and

private interests on shoreline stability, setbacks for coastal development and on selection

of appropriate coastal protection structures. Data is also provided to students undertaking

undergraduate and graduate research.

This report assesses the status and trends of 23 beaches and bays around Trinidad for the

period 2004-2008. It highlights the dynamic nature of the beaches and provides

recommendations for improving this monitoring programme.



2 SITE DESCRIPTION

2.1 NORTH COAST

The north coast of Trinidad is open to the Caribbean Sea and exposed to the Northeast

Trade Winds and Mid-Atlantic storm swells and surges (Figure 1). The bays on the

northern coastline are exposed to moderate to high wave energy where breaker heights

can exceed 0.80 m (IMA, 2004). This sometimes results in beach erosion taking place at the

larger sandy beaches at Maracas, Tyrico and Las Cuevas Bays. The backshores have

relatively low gradient topography and in the case of the larger bays they consist of recent

alluvium deposits (Saunders, 1998). Some bays are more indented than others and have

more pronounced headlands. These are mostly backed by steep cliffs consisting of low-

Figure 1: Map of the Caribbean showing the Location of Trinidad

Source: Institute of Marine Affairs (2012)



medium grade metamorphic rocks that have near parallel faults passing through them in a

northwest–southeast trend (Saunders, 1998). There are various geomorphological features

along this coastline such as wave cut platforms, caves, stacks and blowholes (Figure 2). The

geology of the north coast makes the bays less susceptible to coastline erosion where the

bay is backed by these metamorphic rocks. Even though no cliff recession may be observed,

reduction in beach sediment volume can be very evident at some locations.

2.2 EAST COAST

The east coast is a high energy wave environment and is exposed to the Atlantic Ocean and

the Northeast Trade Winds (Figure 1). This coastline is varied in its geomorphology and

geology (Figure 2). The northern section is rugged and more resistant to the forces of

erosion due to the geology, as metamorphic rocks back this section of the coastline (IMA,

2004). There are high cliffs, indented bays, wave cut platforms, caves and other coastal

geomorphological features formed from the marine erosive forces. The central section

extending from Matura to Point Galeota, which encompasses Cocos and Mayaro Bays, are

low lying and separated by the steep cliffs at Point Radix. These bays are backed by

extensive stretches of coconut plantations. The open coastline is subjected to coastal

processes that have resulted in significant erosion at certain locations over the years

(Saunders, 1998; Darsan 2005a, 2012). Fallen coconut trees and a receding shoreline at

north and south Cocos bay attest to this occurrence. At the Nariva River mouth in central

Cocos, lies the Cocal sand spit which is an area that is accreting (Darsan, 2012). Several

rows of spilling breakers are characteristic of these east coast bays. In some areas along

this shoreline, coastal erosion has prompted the construction of various coastal defense

structures such as seawalls, rip rap revetments and coconut tree trunks lined on the low

cliffs of the shoreline (IMA, 2004).



Figure 2: Coastal Classification Map of Trinidad

Source: Redrawn from Institute of Marine Affairs (1983)

2.3 SOUTH COAST

The southern coast consists of an alternating irregular series of low and high cliffs, coastal

plains and small emergences of wetlands at Morne Diablo, Erin and Icacos. These

outcroppings are easily eroded and subjected to landslides and slumping. The geology of

this area is that of weak unconsolidated silts and clays which provide little resistance to

wave attack (Saunders, 1998). As a result of continuous exposure to these waves, there are

cliffs along the southern coast (Figure 2). The murky waters along this coastline are

indicative of the high sediment discharge from the rivers of the South American mainland,

particularly the Orinoco. One of these impacts is that the southern coast has accumulated

silt as a result of this river’s discharge; an effect that is more pronounced in the wet season.



2.4 WEST COAST

The west coast faces the Gulf of Paria (Figure 2). It is varied in its coastal classification;

rugged outcrops in the northern section, mangroves and mud flats in the central section

and low to moderate high cliffs in the southern region (Georges, 1993). The southern cliffs

are more easily eroded due to their geological composition. The geology of this coastline

consists of weak unconsolidated silts, clays and sandstones (Saunders, 1998). The beaches

along this coastline are gently sloping. Wave energy is moderate because of the sheltered

Gulf of Paria. Murky waters along this coastline are indicative of the high sediment

discharge from the rivers of the South American mainland, particularly the Orinoco. There

is extensive urban and industrial development along the west coast, and the existence of

mangroves and mud flats limits beach environments.



3 METHODOLOGY

3.1 DATA COLLECTION

Primary data collected include beach profiles, littoral processes and beach sediment grain

size. The dynamic configuration of the shoreline was determined by conducting beach

profiling at regular intervals along the coast. Littoral processes data such as; wave

approach, wave height, breaker height and near shore currents were collected at each

profile location (Figure 3).

Figure 3: Location of IMA Beach Monitoring Stations in Trinidad

Source: Institute of Marine Affairs (2012)



3.2 BEACH PROFILES

Beach profiles are cross sectional traces, perpendicular to the shoreline, taken along a

transect which extends from a fixed mark in a stable area (the benchmark) of the

backshore to the near shore zone (Figure 4). Each profile was obtained with the use of a

Sokkia survey level, measuring tape, survey staff and a compass. Each benchmark was

marked by a concrete encased PVC pipe capped with a 2” brass plate. The measuring tape

was extended from the benchmark along the transect to the lower beach. The survey level

was mounted on the survey tripod and set up over the tape measure in a stable area of the

beach. Readings were first taken off the staff at the benchmark and then at fixed distances

along the transect, usually every 4 m, or where there were distinct changes in the gradient.

Figure 4: Cross Section of a Beach

(Source: http://www.springerlink.com/content/u477gx630260l207/)

Readings were also taken at the vegetation line, high water mark, at the water line and

extended into the water to a depth of approximately 1.5 m. Beach profiles were conducted

at low tide conditions which allowed the maximum transect distance to be captured. For

Trinidad, beach profiles were conducted quarterly during the months of January, April, July

and October. However, for some beaches beach profiles were conducted on a monthly

basis. These beaches included areas with coastal development or areas of particular

research interest.

Some beach profiling stations are referenced to Mean Sea Level (MSL) where The MSL

elevations for these stations were transferred from Land and Surveys tertiary benchmarks.

For profiles not referenced to MSL, a local datum, usually a value of 10 m was assigned to

Breakers



the benchmark. Selected beach profiles have been plotted to be representative of the

reporting period. Both summer and winter month profiles were selected from each of the

year under consideration.

Even though this report presents data for 2004 – 2008, a more systematic methodology

was applied to beach profile data collected as far back in the 1980’s to determine whether

they are stable, eroding or accreting. Beach profiles were analyzed to determine the

changes in the horizontal beach width and beach volume, and these are presented in the

form of charts. Best fit lines were plotted to derive the underlying trend and both

regression line equation and coefficient stated.

For stations that are tied in to MSL, the horizontal beach width is the distance between the

benchmark and the position where the profile attains a value of 0.0 m elevation. This is

usually an interpolated distance value from the beach profile. The beach volume is the area

under the curve up to the profile-MSL intercept. In cases where the benchmark was set

back due to erosion, the beach volume could not be determined for previous years. It would

have been inaccurate to add the volume below the profile between the new and old

benchmark since it is not a constant value. For stations not tied into MSL, the beach width

and beach volume could not be derived and assessment of the beach dynamics were based

on the profile data only.

3.3 LITTORALS

Wind speed was collected using a digital anemometer and was measured in meters per

second (m/s) while the direction was obtained with a Brunton direct pointing compass.

Wave height was measured with a 7.6 m extendable survey staff in the zone immediately

behind the breakers and was taken as the height between the crest and trough of the

waves. The breaker heights were measured in similar method as the wave heights but,

were measured in the breaker zone. Wave approach was measured from the shoreline with

a Brunton direct pointing compass. The compass was pointed perpendicularly toward the

oncoming waves and the direction noted.

Longshore speed was measured when a floating object was thrown into the water within

the breaker zone. The researcher then aligned himself on the shoreline with the object and

marked the sand. The movement of the object was timed for a period of one minute with a

stop watch (the researcher always kept in alignment with the object). At the end of one

minute another mark was made on the sand. The distance moved by the object was then

measured. Longshore current speed was calculated in centimeters per second (cm/s). The

direction in which the object moved was obtained with a Brunton direct pointing compass.

The compass was pointed in the direction of the object along the shoreline from the mid-

beach area. This direction was converted into a cardinal bearing and given as the longshore

drift direction.



3.4 GRAIN SIZE ANALYSIS

Sediment samples were collected from the upper beach, mid-beach and lower beach at

each profiling station. Grain size analysis was conducted using a method provided by Folk

(1974). Wet samples were dried in 500 ml aluminum dishes at 105oC for 24 hours. The

oven-dried samples were placed in an incubator to cool at room temperature. A random

sample was obtained for analysis using a sample splitter. Using an analytical balance,

approximately 120 g from the split random sample was weighed. All weights were

recorded to four decimal places. The weighed sample was transferred to the sieve pans

and placed in sieve shaker to separate into individual grain size. Sediments was sieved

using U.S Standard sieves at ½-phi () unit intervals ranging from -4.0 (16 mm) to 4.0

(0.0625 mm). Sediment passing through the 4.0 sieve was collected in a pan and was

classified as mud. The bank of sieves was agitated in a shaker for at least 20 minutes. Each

sieve fraction is then weighed using the analytical balance.

[Phi () = -log2d, where d is diameter of the particle size in millimetres]

Grain size distribution graphs were plotted using “Grapher” software. Folk and Ward’s

(1957) statistical parameters such as mean, median, sorting, skewness and kurtosis were

calculated using data extracted from the graphs. Sorting, kurtosis and skewness

descriptions based on the calculated values are presented in Table 1, 2 and 3 respectively.

Sorting of sediments is a measure of the uniformity of the grain sizes present in the

sediment. Sediments with a smaller range of particle sizes or greater quantities of specific

sizes are better sorted than those with more ranges. The kurtosis value is a measure of the

peakedness of the sediment size distribution. The skewness value is an indication whether

the sediment distribution tails off at the finer or coarser grain size (Folk 1974). The sample

is also classified according to Folk and Ward’s system of classification (Figure 5) based

upon the percentage composition of Gravel (>2.0 mm), Sand (0.0625 mm – 2.00 mm) and

Mud (<0.0625 mm).



Table 1: Description of Sorting Values used in Grain Size Analysis

Sorting Value () Description

< 0..35 Very well sorted

0.35 - 0.50 Well sorted

0.50 – 0.71 Moderately well sorted

0.71 - 1.00 Moderately sorted

1.00 - 2.00 Poorly sorted

2.00 - 4.00 Very poorly sorted

>4.00 Extremely poorly sorted

Table 2: Description of Kurtosis Values used in Grain Size Analysis

Kurtosis Value Description

< 0.67 Very Platykurtic

0.67 - 0.90 Platykurtic

0.90 - 1.11 Mesokurtic

1.11 - 1.50 Leptokurtic

1.50 - 3.00 Very Leptokurtic

>3.00 Extremely Leptokurtic

Table 3: Description of Skewness Values used in Grain Size Analysis

Skewness Value () Description

-0.30 to -1.00 Strongly Coarse Skewed

-0.10 to -0.30 Coarse Skewed

+0.10 to -0.10 Near Symmetrical

+0.10 to +0.30 Fine skewed

+0.30 to +1.00 Strongly Fine Skewed



Figure 5: Ternary diagram of grain size nomenclature for sediments containing gravel, sand and mud (Source: Folk 1974)



4 RESULTS AND DISCUSSION

4.1 NORTH COAST

A summary of the littoral processes occurring on north coast beaches and bays is presented

in Table 4. A summary of the grain size parameters is presented in Table 5, while shoreline

erosion/accretion processes for the period 2004 – 2008 is presented in Table 6.

All monitored beaches along the north coast are in dynamic equilibrium (DE) except for the

eastern and western regions of Las Cuevas Bay and the western section of Blanchisseuse

Bay. Macqueripe Bay is backed by a seawall that protects the backshore from being eroded.

At Maracas and Tyrico Bays, there were variation in the sand elevations but recession on

the low backshore cliff was not observed. At Las Cuevas Bay, the areas of the beach that

experienced erosion were the regions that were not backed by the metamorphic cliffs.

These areas also experienced changes to the sand elevations along the beach face, and are

more susceptible to erosion from storm surges.

The beach at Blanchisseuse experienced erosion from wave action, weathering and

slumping of the low backshore cliff. Grande Riviere is backed in the central and western

regions by metamorphic rocks and therefore fairly resistant to wave erosion. At the eastern

section of the bay, the berm is wide and buffers wave energy which reduces erosion of the

backshore cliff. The berm however is very dynamic and experiences distinct changes

during the summer and winter periods. The reef at Salybia is fairly efficient in reducing

wave energy that would otherwise erode the low backshore cliff. However, the storm event

experienced in October 2005 allowed wave energy to pass over the reef and resulted in

erosion.



Table 4: Summary Littoral processes for North Coast Beaches of Trinidad for the period 2004 – 2008

Beach/Bay Station

Location

Wind Speed

Wind Direction

Significant Wave Height Breaker Height Breaker Period Longshore Current Speed

Current Direction

(s) (cm/s)

Mean Range

STD Mean

Range

STD Direction Mean Range

STD Mean Range STD Mean Range STD

Macqueripe Central 2.03 0.00 – 3.1 0.68 NE 0.44 0.25-0.60 0.11 NW 0.5 0.35 - 0.60 0.08 7.1 0.0 - 11.6 1.63 4.4 0.0 -8.5 3.3 SW

Maracas West 2.5 1.5 - 3.6 0.66 NE 0.54 0.45-1.00 0.22 NE 0.62 0.50 - 1.50 0.33 8.3 6.0 - 11.0 1.76 11 5.3-19.8 4.63 W

Central (old

profile) 2.8 1.5-5.1 1.66 NE 0.8 0.5-1.20 0.42 NE 0.83 0.55-1.2 0.42 7.7 7.0 - 9.0 3.16 19.08 12.4 - 26.8 9.28 NW

Central 3 2.0 - 4.2 0.78 NE 0.81 6.6-8.2 0.27 SE 0.85 0.5-1.20 0.24 7.34 6.3 - 8.7 0.61 15.37 5.7 - 22.7 2.22 NW

East 2.46 0.3 - 4.2 0.82 NE 0.69 0.40-1.20 0.27 NE 0.77 0.30 - 1.50 0.35 8.2 6.9 - 12.0 2.08 12.4 1.2 - 22.2 5.93 NW

Tyrico West 3.4 0.8 - 11.0 4.3 E 0.46 0.30-0.70 0.2 NNE 0.55 0.30 - 0.90 0.3 8 7.4 - 8.5 0.5 7.9 4.5 - 12.8 3.2 W

East 1.4 0.0 - 2.4 0.8 E 0.46 0.10-0.75 0.2 SE 0.54 0.10 - 0.90 0.3 7.7 7.1 - 8.6 0.7 7.7 3.4 - 10.7 2.3 W

Las Cuevas East 1.5 0.0 - 3.0 0.98 ENE 0.51 0.30-1.20 0.27 SW 0.6 0.20 - 1.50 0.36 9.08 7.5 - 22.0 3.99 13.1 1.2 - 32.9 7.66 SW

Central 2.44 1.3 - 5.1 1.36 NE 0.71 0.40-1.00 0.17 SE 0.77 0.50 - 1.20 0.17 7.15 6.6-8.3 0.48 16 10.2 - 26.8 10.27 SW

West 2.5 0.0 - 5.0 1.57 NE 0.44 0.30-0.70 0.13 SE 0.61 0.20 - 0.80 0.21 7.18 6.60 - 9.80 1.11 12.4 2.3 -28.0 7.63 SW

Blanchisseuse West 2.1 0.0 - 5.1 1.19 ENE 0.97 0.50-2.00 0.5 NE 1.2 0.50 - 3.00 0.74 7.37 6.40 - 8.60 0.58 20.1 10.2 - 30.0 7.43 SW

Grande Riviere West 2.1 0.7 - 3.1 0.87 E 1 0.50-1.00 0.23 NE 1.1 0.70 - 1.50 0.24 7.13 6.20 - 8.40 0.75 13.2 8.50 - 23.30 5.46 NW

Central(2) 2.43 0.7 - 7.9 2.33 E 0.96 0.70-1.50 0.25 NE 1.1 0.70 - 2.0 0.39 7.58 6.70 - 8.40 0.58 10.8 4.3 - 17.0 4.18 NW

Central (3) 2.07 1.3 - 2.8 1.3 E 0.94 .70-1.5 0.27 NE 1.13 0.70 - 2.0 0.4 6.8 6.0 - 7.4 0.48 13.01 4.30 - 26.80 6.92 NW

East 2.1 0.7 - 3.7 0.97 E 0.8 0.50-1.50 0.32 NE 1 0.50 - 2.00 0.45 7.4 6.70 - 8.70 0.65 11.1 8.5 - 14.73 2.03 NW

Salybia West 4.5 0.0 - 17.1 5.73 E 0.4 0.10-0.80 0.26 NE 0.47 0.10 - 1.00 0.31 7.6 7.10 - 9.40 0.8 38.5 21.3 - 65.7 14.67 SW



Table 5: Summary Grain Size for North Coast Beaches of Trinidad

BEACH/BAY STATION DESCRIPTION SAMPLE

LOCATION

GRAPHIC MEAN MEDIAN SORTING SKEWNESS KURTOSIS

PERCENTAGE COMPOSITION CLASSIFICATION (FOLK & WARD) mm mm mm REMARKS

GRAVEL >2.0mm

SAND (0.0625 - 2.0 mm)

MUD < 0.0625mm

Maracas Bay 1 West

UB 2.30 0.20 2.30 0.20 0.40 0.76 Well sorted 0.00 1.00 0.13 99.87 0.00 Slightly Gravelly

SAND

MB 2.01 0.25 2.01 0.25 0.47 0.72 Well sorted 0.00 1.00 0.08 99.90 0.02 Slightly Gravelly

SAND

LB 1.14 0.45 1.90 0.27 1.65 0.32 Poorly sorted -0.69 1.00 14.45 85.54 0.02 Gravelly SAND

Maracas Bay 2 Central


SAND


SAND

LB 1.45 0.37 1.45 0.37 0.56 0.68 Well sorted 0.00 1.00 0.97 99.03 0.00 Slightly Gravelly

SAND

Maracas Bay 3 Central

UB 1.89 0.27 1.89 0.27 0.39 0.76 Well sorted 0.00 1.00 0.00 99.95 0.05 SAND


SAND


SAND

Maracas Bay 4 East

UB 1.06 0.48 1.37 0.39 1.26 0.42 Poorly sorted -0.41 0.88 9.43 90.57 0.00 Gravelly SAND

MB 1.29 0.41 1.41 0.38 0.96 0.51 Moderately

sorted -0.23 0.85 1.10 98.78 0.12

Slightly Gravelly SAND


SAND

Tyrico Bay 1 West

UB 2.55 0.17 2.55 0.17 0.28 0.82 Very well

sorted 0.00 1.00 0.03 99.92 0.05


MB 2.17 0.22 2.29 0.20 0.67 0.63 Moderately well sorted

-0.45 2.28 1.60 98.37 0.03 Slightly Gravelly

SAND

LB 2.12 0.23 2.24 0.21 0.76 0.59 Moderately

sorted -0.45 2.33 3.51 96.49 0.00


Tyrico Bay 2 East

UB 2.48 0.18 2.48 0.18 0.24 0.85 Very well sorted 0.00 0.99 0.18 99.73 0.08 Slightly Gravelly

SAND

MB 2.38 0.19 2.38 0.19 0.47 0.72 Well sorted -0.22 1.78 0.80 99.15 0.05 Slightly Gravelly

SAND

LB 2.41 0.19 2.41 0.19 0.31 0.80 Very well sorted 0.00 1.00 0.53 99.47 0.00 Slightly Gravelly

SAND

Las Cuevas Bay

3 East


SAND

MB 2.35 0.20 2.35 0.20 0.34 0.79 Very well sorted -0.13 1.38 1.17 98.73 0.10 Slightly Gravelly

SAND

LB 2.28 0.21 2.28 0.21 0.46 0.73 Well sorted -0.28 1.91 2.00 97.98 0.02 Slightly Gravelly

SAND



Table 5: Summary Grain Size for North Coast Beaches of Trinidad, Cont’d.


LOCATION



GRAVEL >2.0mm

SAND (0.0625 - 2.0 mm)

MUD < 0.0625mm

Las Cuevas Bay

2 Central


SAND


SAND


SAND

Las Cuevas Bay

1 West


SAND


SAND


SAND

Blanchisseuse Bay

2 West

UB 1.17 0.45 1.22 0.43 0.84 0.56 Moderately

sorted -0.17 0.79 0.40 99.52 0.08


MB 0.41 0.75 0.13 0.91 0.94 0.52 Moderately

sorted 0.44 1.13 2.43 97.53 0.03


LB -0.11 1.08 -0.10 1.07 0.69 0.62 Moderately well

sorted 0.13 1.40 5.13 94.82 0.05 Gravelly SAND

Grande Riviere

1 West

UB 1.25 0.42 1.25 0.42 0.65 0.64 Moderately well

sorted 0.00 1.00 0.43 99.57 0.00


MB 1.24 0.42 1.24 0.42 0.76 0.59 Moderately

sorted 0.00 1.00 0.30 99.69 0.01



Grande Riviere

2 Central


sorted 0.02 1.04 0.61 99.39 0.00


MB 0.99 0.50 0.99 0.50 0.67 0.63 Moderately well

sorted -0.10 1.27 2.72 97.27 0.01



Grande Riviere

3 Central


sorted 0.16 1.13 0.88 99.12 0.00



sorted -0.07 1.13 0.62 99.36 0.02


LB -0.53 1.44 -0.53 1.44 1.17 0.45 Poorly sorted -0.03 1.07 33.25 75.79 0.01 Sandy GRAVEL

Grande Riviere

4 East


sorted -0.06 1.10 2.07 97.91 0.02


MB 1.08 0.47 1.08 0.47 0.78 0.58 Moderately

sorted 0.00 1.00 0.62 99.37 0.01





Table 5: Summary Grain Size for North Coast Beaches of Trinidad, Cont’d.


LOCATION



GRAVEL >2.0mm

SAND (0.0625 - 2.0 mm)

MUD < 0.0625mm

Salybia Bay Toco East


SAND


SAND

LB -0.73 1.66 -0.42 1.34 1.01 0.50 Poorly sorted -0.48 1.07 27.26 72.74 0.00 Gravelly SAND



Table 6: Shoreline stability status of North Coast Beaches of Trinidad for the period 2004 – 2008

Beach/Bay IMA’s Beach Monitoring Station Location

Shoreline Stability Status

(+Net Annual Accretion (m);

-Net Annual Erosion (m);

DE Dynamic Equilibrium)

2004 2005 2006 2007 2008

Macqueripe Central DE DE DE DE DE

Maracas West DE DE DE DE DE

East of River DE DE DE DE DE

Central DE DE DE DE DE

East DE DE DE DE DE

Tyrico West BM not yet established

DE DE DE DE

East BM not yet established

DE DE DE DE

Las Cuevas East BM not yet established

-0.65 -0.20 -0.20 -0.05

Central DE -3.50 DE DE DE

West BM not yet established

-4.00 DE -2.30 -1.80

Blanchisseuse West -0.20 -1.35 DE -0.40 -0.30

Grande Riviere West DE DE DE DE DE


West of Ferdinand River

DE DE DE DE DE

East DE DE DE DE DE

Salybia West DE -0.80 DE DE DE



4.1.1 Macqueripe Bay

Macqueripe Bay is approximately 120 m long and bounded by two very prominent

headlands. Figure 6 is an IKONOS (2007) image of Macqueripe Bay showing the location of

the IMA station. The beach is gently sloping except for a distinct plunge point that quickly

deepens. Failure of the seawall and platform within recent years has prompted the

construction of a new seawall extending from the eastern to western end of the bay

(Plate 1).

Figure 6: IKONOS image of Macqueripe Bay showing IMA Station location (2007)



Plate 1: Beach at Macqueripe Bay showing recently constructed seawall (April 2008)

Wind approaches from the northeast with an average speed of 2.03 m/s (+/-0.68 m/s).

Waves (surging breakers) in this bay approach from the northwest due to refraction. Mean

significant wave height is 0.44 m (+/-0.11 m) with a period of 7.10s (+/-1.63 s) while the

breaker height is 0.50 m (+/-0.08 m) (Table 4). Mean longshore current averages 4.4 cm/s

(range 0.0–8.5 cm/s, +/-3.3 cm/s) and flows in a predominantly south-westerly direction.

Waves are reflected off the seawall at this southern end of the bay, and as a result, the

beach profiles underwent more changes than on the northern end of the bay. It is expected

that at high tide the wave and breaker heights will exceed the values reported here.

Beach profiles conducted during the period 2004 – 2008 indicate that there were no major

changes occurring on the upper beach, but changes in sediment levels were noticed in the

surf zone region. These sediments are either transported to an offshore bar or alongshore

due to the longshore currents present. The highest beach elevation during this period was

obtained in April 2007 (Figure 7).

Macqueripe Bay is very dynamic beach that shows seasonal variation. There is a cyclic

trend that is clearly observed during the summer and winter periods. The beach tends to

have higher elevations of sediment with a lower swash zone gradient in the summer

months and lower elevations with a steeper profile during the winter months (Figure

7Figure 7). The sediment is transported offshore during the winter months and is returned

gradually during the summer months.



Figure 7: Selected beach profiles for Macqueripe Bay for the period 2004 – 2008

Erosional factors that may affect this bay include storm surges, wave action, and to a lesser

extent landslides and sea level rise. The beach is stable even though there is variation in

sediment elevations within the near shore zone (Figure 8).

Figure 8: Maximum - Minimum sediment elevations along the beach profile for Macqueripe Bay for the period 2004 – 2008

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60

Distance from Benchmark (m)

Ele

va

tio

n (

m)

2004 03 2004 05

2005 08 2006 02

2007 04 2007 10

2008 07

Macqueripe Bay

Selected Profiles 2004 - 2008

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

0 5 10 15 20 25 30 35 40

Maximum

Minimum

Average

MAX IMUM AND MINIMUM E L E VAT IONS

MAQUE R IP E B AY

2004 - 2008

EL

EV

AT

ION

(m)

D IS T ANC E (m)

ME AN S E A L E VE L



4.1.2 Maracas Bay

Maracas Bay is approximately 1800 m long and bounded by two very prominent headlands

and dissected at the western end by the Maracas River. The entire bay is gently sloping and

cuspates are normal sediment features along the bay. Figure 9 is an IKONOS (2007) image

of Maracas Bay showing the location of the four IMA stations along this bay.

Figure 9: IKONOS image of Maracas Bay showing Station locations (2007)

Station 1:

The beach at Station 1 (Plate 2) is in dynamic equilibrium (Table 6). Little variation is seen

in the profile with the exception of October 2005 (Figure 11). This change in beach volume

is attributed to the storm surge which occurred resulting in the inundation of the entire

backshore area (Figure 12). The storm surge inundated the road and car-park in the central

section of the bay. This station’s profile however recovered in subsequent months.

1

3

2

4



Plate 2: Maracas Bay Station 1 easterly view showing berm (July 2008)

Littoral data indicates that wind speed averages 2.5 m/s (+/-0.66 m/s) and ranges between

1.5 – 3.6 m/s approaching from the northeast. Waves approach from the east-northeast

with a mean significant wave height of 0.54 m (+/-0.22 m) and a period of 8.3 s (+/- 1.76 s)

while the breaker height (plunging breaker) is 0.62 m (+/- 0.33 m). Mean longshore

current averages 11.0 cm/s (range 5.3-19.8 cm/s, +/- 4.63 cm/s) and flows to the

northwest (Table 4).

In Table 5 it can be seen that the upper beach sediment sample is classified as Slightly

Gravelly SAND with a mean and median grain size of 0.20 mm. The sample consists of

0.13% Gravel (>2.0 mm), 99.87% Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The

sample is well sorted, Near Symmetrical and Mesokurtic.

The mid-beach sample is classified as Slightly Gravelly SAND with a mean and median grain

size of 0.25 mm. The sample consists of 0.08% Gravel (>2.0 mm), 99.9% Sand

(0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The beach sediment is well sorted, Near

Symmetrical and Mesokurtic.

The lower beach sample is classified as Gravelly SAND with a mean grain size of 0.45 mm

and median grain size of 0.27 mm. The sample consists of 14.45% Gravel (>2.0 mm),

85.54% Sand (0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The beach sediment is

poorly sorted, Strongly Coarse Skewed and Mesokurtic. The poor sorting of this sediment

was due to the gravel content possibly from the nearby Maracas River (Figure 10).



Figure 10: Sediment grain-size distributions for Maracas Bay Station 1

Beach profiles for selected months where changes were observed on this bay are presented

in Figure 11. The selections were made to represent at least one summer and one winter

profile for each year 2004 - 2008, where available, or where there were distinct changes in

a particular month. With the exception of the western section, the bay has a relatively

extensive backshore.

Figure 11: Selected beach profiles for Maracas Bay Station 1 (west) for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Maracas Bay Station 1 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)

Sediment Size in (Phi )

Sediment Histogram for Maracas Station 1

UB

MB

LB

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120


Ele

va

tio

n (

m)

2004 03 2004 11

2005 10 2006 04

2006 07 2007 10

2008 01 2008 10

Maracas Bay Station 1

2004 - 2008

BM



A plot of the beach width and volume against number of days elapsed since the first

monitoring was conducted shows variations in both parameters (Figure 12). These

variations can be explained as a result of both seasonal and cyclic trends. A decline in beach

width usually reflects a change in volume. This is however not always the case, as

redistribution of sediment along the profile transect can result in a greater beach width but

a decrease in volume. At this beach however, both changes to beach width and volume

suggest that this beach is stable, as evidenced by the near parallel trend lines (Figure 12).

Significant negative deviations are usually the result of storm waves generated by tropical

depressions, hurricanes passing to the north as was the event in October 2005. In the

months following these events, however, the beach has shown to recover. At this station,

there has been a gradual, yet steady increase in beach width and volume with time

(Figure 12).

Figure 12: Plot of Beach Width and Volume vs. Number of days for Maracas Bay Station 1 (west) for the period February 1985 – October 2008

y = 0.0004x + 4.7626R² = 0.0118

y = 0.0006x + 4.1205R² = 0.0226

-20

-15

-10

-5

0

5

10

15

20

25

30

35

-20

-15

-10

-5

0

5

10

15

20

25

30

35

0

50

0

10

00

15

00

20

00

25

00

30

00

35

00

40

00

45

00

50

00

55

00

60

00

Change in Beach Width

Change in Beach Volume

Linear (Change in Beach Width)

Linear (Change in Beach Volume)

MARACAS BAY - Station 1Changes in Beach Widths and Volumes

February 1995 - October 2008

Be

ach

Wid

th(m

)

Be

ach

Vo

lum

e (

m3 )

Number of Days (Units)

Storm surge – October 2005



Station 2:

The beach at Station 2 (Plate 3) on the eastern side of the Maracas River also exhibits

dynamic equilibrium (Table 6). The storm surge of October 2005 is reflected in the profile

(Figure 14). Recovery of the beach was observed six months after the event.

Plate 3: Maracas Bay Station 2 (July 2008)


Waves in this station approaches from the northeast. Mean significant wave height is

0.54 m (+/-0.22 m) with a period of 7.7s (+/-3.16 s) while the breaker height (plunging

breaker) is 0.83 m (+/- 0.42 m). Mean longshore current averages 19.08 cm/s (range 12.4-

26.8 cm/s, +/- 9.28 cm/s) and flows west-northwest (Table 4).

From Table 5 it is shown that the upper beach sediment sample is classified as Slightly


0.05% Gravel (>2.0 mm), 99.85% Sand (0.0625 - 2.0 mm) and 0.1% Mud (<0.0625 mm).

The beach sediment is well sorted, Near Symmetrical and Mesokurtic.


size of 0.26 mm. The sample consists of 0.1% Gravel (>2.0 mm), 99.88% Sand (0.0625 -

2.0 mm) and 0.02% Mud (<0.0625 mm). The mid-beach sediment is well sorted, Near




The lower beach sample is classified as Slightly Gravelly SAND with a mean and median

grain size of 0.37 mm. The sample consists of 0.97% Gravel (>2.0 mm), 99.03% Sand

(0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The lower beach sediment is moderately

well sorted, Near Symmetrical and Mesokurtic (Figure 13).



2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)


UM

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4P

erce

nta

ge (

%)



UB

MB

LB

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120


Ele

va

tio

n (

m)

2004 03 2004 12

2005 10 2006 04

2006 07 2007 10

2008 01 2008 10


2004 - 2008

BM



At this beach location, both changes to beach width and volume suggest that this beach is

fairly stable (Figure 15). The long term trend shows a stable beach width but small

negative decline in beach volume. This can be explained by a flattening of the beach with

sediment from the backshore but non-preservation of the re-distributed sediment resulting

in smaller volumes along the transect. The impact of the tropical storm surge of October

2005 is reflected in the plot by the sharp decline in beach width and volume. Successive

months after these events however indicate positive recovery to the beach.

Figure 15: Plot of Beach Width and Volume vs. Number of days for Maracas Bay Station 2 (central) for the period March 1985 – October 2008

Figure 16 shows the maximum and minimum elevations of the beach at this station as well

as the dynamic nature of this bay at the central section. The minimum elevation of this

station was greatly influenced by the storm surge of October 2005. At 60 m from the

benchmark, there is an approximate 1.5 m variation in beach elevation, which displays the

dynamism at this station.

y = 0.0003x + 3.0145R² = 0.0064

y = -0.0007x + 5.1629R² = 0.0275

-30

-25

-20

-15

-10

-5

0

5

10

15

20

25

30

-30

-25

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-15

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-5

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30

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50

0

10

00

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55

00

60

00

65

00

70

00

75

00

80

00

85

00

90

00






March 1985 - October 2008

Ch

ange

in B

eac

h W

idth

(m)

Ch

ange

in B

eac

h V

olu

me

(m

3 )




Figure 16: Maximum and Minimum beach elevations for Maracas Bay Station 2 (central) for the period 2004 – 2008

Station 3:

The central section of Maracas Bay (Station 3) shown in Plate 4 also exhibits dynamic

equilibrium (Table 6). Selected beach profile data (Figure 18) shows the changes occurring

at this station .Reduction in beach elevation was also observed after the storm surge of

October 2005; however, recovery was reported in subsequent months.

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64

MAXIMUM

MINIMUM

AVE R AGE


MAR AC AS B AY - S T AT ION 2

2004 - 2008

EL

EV

AT

ION

(m

)

D IS T ANC E (m)




Plate 4: Maracas Bay Station 3 showing wide gently sloping beach (July 2008)

Wind speed averages 3.0m/s (+/-0.78 m/s) and ranges between 2.0-4.2 m/s approaching

from the northeast. Waves approach from the northeast with a mean significant wave

height of 0.81 m (+/-0.27 m) and a period of 7.34 s (+/- 0.61 s) while the breaker height

(plunging breaker) is 0.85 m (+/- 0.24 m). Mean longshore current averages 15.37 cm/s

(range 5.7-22.7 cm/s, +/- 2.22 cm/s) and flows to the west-northwest (Table 4).

From Table 5 it is shown that the upper beach sediment sample is classified as SAND with a

mean and median grain size of 0.27 mm. The sample consists of 0% Gravel (>2.0 mm),

99.95% Sand (0.0625 - 2.0 mm) and 0.05% Mud (<0.0625 mm). The upper beach sediment

is well sorted, Near Symmetrical and Mesokurtic.

The mid-beach sample is classified as Slightly Gravelly SAND with a mean grain size of

0.25 mm and median grain size of 0.26 mm. The sample consists of 0.03% Gravel

(>2.0 mm), 99.95% Sand (0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The mid-beach

sediment is well sorted, Near Symmetrical and Mesokurtic.



(0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The lower beach sediment is moderately

well sorted, Near Symmetrical and Mesokurtic (Figure 17).




Figure 18: Selected beach profiles for Maracas Bay Station 3 (central) for the period 2004 – 2008

At this station changes to both beach width and volume suggest that this beach is stable, as

reflected by the minor positive trend line gradients (Figure 19). The impact of the tropical

storm surge of October 2005 is also reflected in the plot by the sharp decline in beach

width and volume. Successive months after these events however indicate positive

recovery to the beach. Plate 4 shows the wide beach at this station approximately 3 years

after the storm surge event.

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)


UM

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)



UB

MB

LB

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120


Ele

va

tio

n (

m)

2004 03 2004 12

2005 10 2006 04

2006 07 2007 10

2008 01 2008 10


2004 - 2008

BM



Figure 19: Plot of Beach Width and Volume vs. Number of days for Maracas Bay Station 3 (central) for the period March 1985 – October 2008

Station 4:

Station 4 at the eastern side of Maracas Bay (Plate 5) also exhibits dynamic equilibrium

(Table 6). The storm surge of October 2005 did not impact this section of the bay as much

as the other stations along this bay (Figure 21).

y = 0.0004x + 4.7626R² = 0.0118

y = 0.0006x + 4.1205R² = 0.0226

-20

-15

-10

-5

0

5

10

15

20

25

30

35

-20

-15

-10

-5

0

5

10

15

20

25

30

35

0

50

0

10

00

15

00

20

00

25

00

30

00

35

00

40

00

45

00

50

00






February 1995 - September 2008

Be

ach

Wid

th(m

)

Be

ach

Vo

lum

e

(m3 )

Number of Days (from base date)



Plate 5: Beach at Maracas Bay Station 4 (July 2008)


Waves at this station approach from the northeast. Mean significant wave height is 0.69 m

(+/-0.22 m) with a period of 7.7 s (+/-3.16 s) while the breaker height (plunging breaker)

is 0.83 m (+/- 0.42 m). Mean longshore current averages 12.4 cm/s (range 1.2-22.2 cm/s,

+/- 9.28 cm/s) and flows west (Table 4).

From Table 5 it is shown that the upper beach sediment sample is classified as Gravelly

SAND with a mean grain size of 0.48 mm and median grain size of 0.39 mm. The sample

consists of 9.43% Gravel (>2.0 mm), 90.57% Sand (0.0625 - 2.0 mm) and 0% Mud

(<0.0625 mm). The upper beach sediment is poorly sorted, Strongly Coarse Skewed and

Platykurtic.


0.41 mm and median grain size of 0.38 mm. The sample consists of 1.1% Gravel (>2.0 mm),

98.78% Sand (0.0625 - 2.0 mm) and 0.12% Mud (<0.0625 mm). The mid-beach sediment is

moderately sorted, Coarse Skewed and Platykurtic.

The lower beach sample is classified as Sample is classified as Slightly Gravelly SAND with a

mean and median grain size of 0.31 mm. The sample consists of 0.05% Gravel (>2.0 mm),

99.88% Sand (0.0625 - 2.0 mm) and 0.07% Mud (<0.0625 mm). The lower beach sediment

is well sorted, Near Symmetrical and Mesokurtic (Figure 20).




At Maracas bay the trend observed is that there is a fining of the sediments towards the

east on the lower beach while the upper beach samples become progressively coarser.

Aeolian processes can account for the coarser sediments on the upper beach as fine dried

sediments are transported to the backshore area of the beach by sea breeze.

Figure 21: Selected beach profiles for Maracas Bay Station 4 (east) for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)


UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)

Sediment size (Phi)


UB

MB

LB

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120


Ele

va

tio

n (

m)

2004 03 2004 12

2005 10 2006 04

2006 07 2007 10

2008 01 2008 10


2004 - 2008

BM



At this station both seasonal and cyclic changes to beach width and volume were observed.

The best fit lines suggest that this beach is stable as reflected by the minor positive trend

line gradients (Figure 22). Here, the impact of the tropical storm surge of October 2005 is

not as prominently reflected in this beach profile as at other stations. The trends at this

beach are not only indicative of the sensitivity to erosion from storm surges but to the

ability for recovery within a short period of time, as in this case, approximately 3–4

months. It also indicates the predominant cross-shore sediment transport during extreme

events, possibly forming offshore bars, whose sediment will return to the beachface during

subsequent normal wave conditions.

Figure 22: Plot of Beach Width and Volume vs. Number of days for Maracas Bay Station 4 (east) for the period February 1995 – October 2008

y = 0.0014x - 1.5628R² = 0.0786

y = 0.0010x - 0.8268R² = 0.0510

-15

-10

-5

0

5

10

15

20

25

30

35

-15

-10

-5

0

5

10

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35

0

50

0

10

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15

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20

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25

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30

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35

00

40

00

45

00

50

00







Be

ach

Wid

th(m

)

Be

ach

Vo

lum

e (

m3 )




4.1.3 Tyrico Bay

Tyrico Bay is located east of Maracas Bay and is actually an extension of this bay separated

by a small eroding headland comprising of phyllitic rocks. Figure 23 is an IKONOS (2007)

image of Tyrico Bay showing the location of the two IMA stations along this bay.

Figure 23: IKONOS Image of Tyrico Bay showing station locations (2007)

Station 1:

At the western section of this bay (Station 1) the beach is gently sloping with a wide beach

(Plate 6) that is in dynamic equilibrium (Table 6). Figure 25 shows selected profiles at this

station during 2004 – 2008.

1 2



Plate 6: Tyrico Bay Station 1 west showing cobble cuspates and a gently sloping beach (September 2007)

Wind speed averages 3.4 m/s (+/-4.3 m/s) and ranges between 0.8-11.0 m/s approaching

from the east. Waves approach from the north-northeast with a mean significant wave

height of 0.46 m (+/-0.2 m) and a period of 8.0 s (+/- 0.5 s) while the breaker height

(plunging breaker) is 0.55 m (+/- 0.3 m). Mean longshore current averages 7.9 cm/s (range

4.5-12.8 cm/s, +/- 3.2 cm/s) and flows to the west (Table 4).

The upper beach sediment sample is classified as Slightly Gravelly SAND with a mean and

median grain size of 0.17 mm. The sample consists of 0.03% Gravel (>2.0 mm), 99.92%

Sand (0.0625 - 2.0 mm) and 0.05% Mud (<0.0625 mm). The upper beach sediment is Very

well sorted, Near Symmetrical and Mesokurtic.




moderately well sorted, Strongly Coarse Skewed and Very Leptokurtic.

The lower beach sample is classified as Slightly Gravelly SAND with a mean grain size of


(>2.0 mm), 96.49% Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The lower beach

sediment is moderately sorted, Strongly Coarse Skewed and Very Leptokurtic (Figure 24).



Figure 24: Sediment grain-size distributions for Tyrico Bay Station 1

Figure 25: Selected beach profiles for Tyrico Bay Station 1 (west) for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Tyrico Bay Station 1 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)


Sediment Histogram for Tyrico Station 1

UB

MB

LB

4.0

5.0

6.0

7.0

8.0

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Ele

va

tio

n (

m)

2005 10 2007 10

2008 01 2008 06

2008 09

Tyrico Bay Station 1

2004 - 2008

BM

The Profile at this station is not tied in to the

National Vertical Framework, i.e., Mean Sea

Level



Station 2:

At this eastern station, cobble cuspates become more prominent along the mid-beach

region (Plate 7). These particle sizes are however not reflected in the grain size analysis

due to the absence of this feature at the time of sampling. These cobbles possibly originate

from a combination of the eroding backshore and the river on the eastern of the bay.

Plate 7: Eastern Section of Tyrico Bay showing accumulation of cobbles forming cuspates (September 2007)

At the eastern section of Tyrico Bay (Station 2), wind speed averages 1.4 m/s (+/-0.8 m/s)

and ranges between 0.0 -2.4 m/s approaching from the east. Waves approach from the

north-northeast with a mean significant wave height of 0.46 m (+/-0.2 m) and a period of

7.7 s (+/- 0.7 s), while the breaker height (plunging breaker) is 0.54 m (+/- 0.3 m). Mean

longshore current averages 7.7 cm/s (range 0.4-10.7 cm/s, +/- 3.2 cm/s) and flows to the

west (Table 4).







2.0 mm) and 0.05% Mud (<0.0625 mm). The mid-beach sediment is well sorted, Coarse

Skewed and Very Leptokurtic.





(0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The sediment is Very well sorted, Near

Symmetrical and Mesokurtic (Figure 26).

Figure 26: Sediment grain-size distributions for Tyrico Bay Station 2

Profile changes occurring at Tyrico Bay Station 2 (east) are shown in Figure 27 inclusive of

the impact of the October 2005 storm surge. Recovery of the beach at this station was

reported up until June 2008, however, loss in sediment was observed in September 2008.

Continued profiling will determine whether this station re-establishes equilibrium or

continues to erode. The sediment removed may have been transported offshore or

alongshore.

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by

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Sediment size (Phi)

Tyrico Bay Station 2 Sediment

UM

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Per

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Sediment Histogram for Tyrico Station 2

UB

MB

LB



Figure 27: Selected beach profiles for Tyrico Bay Station 2 (east) for the period 2004 – 2008

4.1.4 Las Cuevas Bay

Las Cuevas Bay is approximately 2.2 km long and is the longest bay on the north coast. The

bay is dissected in the centre by the Curaguate River, which changes its course seasonally

due to an extensive east-west trending spit, diverting the flow to the west. This often

results in the erosion of the low backshore bluff. The well defined berm however offers

some resistant to the oncoming waves. Figure 28 is an IKONOS (2007) image of Las Cuevas

Bay showing the location of the three IMA stations.

4.0

5.0

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8.0

9.0

10.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120


Ele

va

tio

n (

m)

2005 10 2006 04

2006 07 2007 10

2008 01 2008 06

2008 10

Tyrico Bay Station 2

2004 - 2008

BM

The Profile at this station is not tied in to the

National Vertical Framework, i.e., Mean Sea

Level



Figure 28: IKONOS image of Las Cuevas Bay showing Station locations (2007)

Station 1:

Erosion of the backshore cliffs at the western section of Las Cuevas Bay (Figure 28) is

dominated by the east-west flowing Curaguate River exiting in close proximity to the IMA’s

benchmark. This section of the bay usually has a wide berm (Plate 8). The backshore area

at this location consists mainly of weakly consolidated alluvium (Saunders 1998) and

hence very susceptible to erosion (Table 4).

1

3

2



Plate 8: West section of Las Cuevas Bay (Station 1) showing the wide berm (September 2007)

Wind approaches this station from the northeast with an average speed of 2.5 m/s

(+/-1.57 m/s). Waves in this station approaches from the northwest. Mean significant wave

height is 0.44 m (+/-0.13 m) with a period of 7.18s (+/-1.11 s) while the breaker height

(plunging breaker) is 0.61 m (+/- 0.21 m). Mean longshore current averages 12.4 cm/s

(range 2.3-28.0 cm/s, +/- 7.63 cm/s) and flows southwest.







(0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The sediment is well sorted, Near




(0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The lower beach sediment is well sorted,

Near Symmetrical and Mesokurtic (Figure 29).



Figure 29: Sediment grain-size distributions for Las Cuevas Bay Station 1

Figure 30: Selected beach profiles for Las Cuevas Bay Station 1 (west) for the period 2004 – 2008

Although the recession at this station is measured with respect to the cliff, the river channel

becomes in-filled and the berm migrates making the backshore very erratic in its profile

(Figure 30). It is assumed that both cross-shore and longshore transport processes occur at

this station where the sediment moved from the region returns during the accretionery

summer period (April – October). Since 2005, there has been approximately 7.10 m

landward recession of this cliff (Table 6).

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Las Cuevas Station 1 Sediment

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MB

LB

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-2 -1 0 1 2 3 4

Per

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Sediment Histogram for Las Cuevas Station 1

UB

MB

LB

-3.0

-2.0

-1.0

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Ele

va

tio

n (

m)

2005 04 2005 06

2007 10 2008 01

2008 06 2008 09

Las Cuevas Bay Station 3

2004 - 2008 BM




Station 2:

At the central section of Las Cuevas Bay (Station 2) the bay is generally in a state of

dynamic equilibrium (Table 6). Plate 9 shows the beach at this region of the beach. The

storm surge of October 2005 caused a 3.5 m landward recession (Table 6) and created a

low backshore scarp.

Plate 9: Beach at the central section of Las Cuevas Bay (Station 2) showing eroding scarp (September 2007)


Waves in this station approaches from the northeast. Mean significant wave height is

0.71 m (+/-0.17 m) with a period of 7.15 s (+/-0.48 s) while the breaker height (plunging

breaker) is 0.77 m (+/- 0.17 m). Mean longshore current averages 16.0 cm/s (range 10.2-

26.8 cm/s, +/- 10.27 cm/s) and flows west-southwest (Table 4).

The upper beach sediment sample is classified as Sample is classified as Slightly Gravelly

SAND with a mean and median grain size of 0.2 mm. The sample consists of 0.08% Gravel

(>2.0 mm), 99.88% Sand (0.0625 - 2.0 mm) and 0.03% Mud (<0.0625 mm). The sediment

is Very well sorted, Near Symmetrical and Mesokurtic.



(0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The sediment is well sorted, Near




(0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The sediment is Very well sorted, Near

Symmetrical and Mesokurtic (Figure 31).




Selected profiles verify the seasonality and dynamic nature of this section of coastline

(Figure 32). Even though recession of the backshore cliff was observed during the 2004 –

2008 period, the long term trend at this region of the beach indicates that the beach is

actually accreting (Figure 33).

Figure 32: Selected beach profiles for Las Cuevas Bay Station 2 (east) for the period 2004 – 2008

0

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-4 -3 -2 -1 0 1 2 3 4

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%)

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Sediment size (Phi)


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Per

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(%

)

Sediment Size in Phi Units

Sediment Histogram for Las Cuevas Station 2

UB

MB

LB

-3.0

-2.0

-1.0

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Ele

va

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n (

m)

2004 03 2004 12

2005 08 2007 10

2008 01 2008 08


2004 - 2008

BM



Although evident cyclic and seasonal trends are observed, the beach width has over time

become wider with a corresponding increase in beach volume. This accretionary material

is possibly supplied from the eroding backshore cliffs on the western region of the bay in

addition to new sediments from the Curaguate River.

The dynamics of this section of Las Cuevas Bay is also supported by the maximum-

minimum elevations during 2004 – 2008 (Figure 34). The average cross section of the bay

however is closely related to the maximum elevation. An off shore bar is located between

60 – 76 m seaward of the IMA benchmark (Figure 34).

Figure 33: Plot of Beach Width and Volume vs. Number of days for Las Cuevas Bay Station 2 (central) for the period March 1985 – October 2008

y = 0.0009x + 7.8355R² = 0.0441

y = 0.0019x + 13.8236R² = 0.1211

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LAS CUEVAS BAY - Station 2Changes in Beach Widths and Volumes


Be

ach

Wid

th(m

)

Be

ach

Vo

lum

e (

m3 )




Figure 34: Maximum and Minimum beach elevations for Las Cuevas Bay Station 2 (central) for the period 2004 – 2008

Station 3:

At the eastern section of Las Cuevas Bay (Station 1) the low bluff is slowly eroding

(Table 6). The bay however is dynamic and exhibits seasonal changes in sediment elevation

(Figure 36). The beach at this station is fairly wide and gently sloping (Plate 10).

Plate 10: Las Cuevas Bay Station 3 east showing wide gently sloping beach (July 2008)

-2

-1

-1

0

1

1

2

2

3

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80

MAXIMUM

MINIMUM

AVE R AGE


L AS C UE VAS B AY - S T AT ION 2

2004 - 2008

EL

EV

AT

ION

(m

)

D IS T ANC E (m)




Wind approaches from the east-northeast with an average speed of 1.5 m/s (+/-0.98 m/s).

Waves at this station approaches from the north-north east. Mean significant wave height

is 0.51m (+/-0.27 m) with a period of 9.08s (+/-3.99 s), while the breaker height (plunging

breaker) is 0.6 m (+/- 0.36 m). Mean longshore current averages 13.1 cm/s

(range 1.2-32.9 cm/s, +/- 7.66 cm/s) and flows predominantly to the west.

The upper beach sediment sample is classified as Slightly Gravelly SAND with a mean grain

size of 0.19 mm and median grain size of 1 mm. The sample consists of 0% Gravel

(>2.0 mm), 0% Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The upper beach

sediment is Very well sorted, Near Symmetrical and Very Platykurtic.

The mid-beach sample is classified as Slightly Gravelly SAND with a mean grain size and

median grain size of 0.2 mm. The sample consists of 1.17% Gravel (>2.0 mm), 98.73% Sand

(0.0625 - 2.0 mm) and 0.1% Mud (<0.0625 mm). The mid-beach sediment is Very well

sorted, Coarse Skewed and Leptokurtic.


grain size of 0.21 mm. The sample consists of 2% Gravel (>2.0 mm), 97.98% Sand (0.0625 -

2.0 mm) and 0.02% Mud (<0.0625 mm). The lower beach sediment is well sorted, Coarse

Skewed and Very Leptokurtic (Figure 35).


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ve (

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Sediment size (Phi)


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-2 -1 0 1 2 3 4

Per

cen

tage

(%

)

Sediment Size in Phi Units

Sediment Histogram for Las Cevas Station 3

UB

MB

LB



Figure 36: Selected beach profiles for Las Cuevas Bay Station 3 (east) for the period 2004 – 2008

4.1.5 Blanchisseuse Bay

Blanchisseuse Bay is approximately 1.4 km long and is bounded on its eastern and western

ends by prominent steep-cliffed headlands of low grade metamorphic rocks. The Marianne

River exits at the eastern end of the bay. The low cliff at this station is undergoing relatively

slow land recession, mainly influenced by slumping (Plate 11). Figure 37 is an IKONOS

(2007) image of Blanchisseuse Bay showing the location of the IMA station on this bay.

-3.0

-2.0

-1.0

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1.0

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Ele

va

tio

n (

m)

2005 04 2005 10

2007 10 2008 01

2008 08


2004 - 2008 BM




Figure 37: IKONOS image of Blanchisseuse Bay showing Station Location (2007)

Plate 11: West section of Blanchisseuse Bay (Station 2) showing the wide berm (September 2007)



Wind speed at this location averages 2.1 m/s (+/-1.19 m/s) and ranges between

0.0 -5.1 m/s approaching from the northeast. Waves approach from the northeast with a

mean significant wave height of 0.97 m (+/-0.5 m) and a period of 7.37 s (+/- 0.58 s), while

the breaker height (plunging breaker) is 1.2 m (+/- 0.74 m). Mean longshore current

averages 20.1 cm/s (range 10.2-30.0 cm/s, +/- 7.43 cm/s) and flows to the west-southwest

(Table 4).


size of 0.45 mm and median grain size of 0.43 mm. The sample consists of 0.4% Gravel


is moderately sorted, Coarse Skewed and Platykurtic.



(>2.0 mm), 97.53% Sand (0.0625 - 2.0 mm) and 0.03% Mud (<0.0625mm). The sediment is

moderately sorted, Strongly Fine Skewed and Leptokurtic.

The lower beach sample is classified as Sample is classified as Gravelly SAND with a mean

grain size of 1.08 mm and median grain size of 1.07 mm. The sample consists of 5.13%

Gravel (>2.0 mm), 94.82% Sand (0.0625 - 2.0 mm) and 0.05% Mud (<0.0625 mm). The

lower beach sediment is moderately well sorted, Fine Skewed and Leptokurtic. The coarse

sediment grain size at this beach is reflective of the high wave energy environment and the

moderately steeply sloping beach (Figure 38).

Figure 38: Sediment grain-size distributions for Blanchisseuse Station 1

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-4 -3 -2 -1 0.0 1 2 3 4

Cu

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ve (

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by

Wei

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Sediment size (Phi)

Blanchisseuse Station 2 Sediment

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MB

LB

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Per

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Sediment Histogram Blanchisseuse Station 2

UB

MB

LB



During the period 2007 – 2008 recession has been measured to be 0.40 m and 0.30 m

respectively (Table 6). The bay is relatively stable with noticeable changes occurring in the

surf zone (Figure 39). A distinct plunge point exists at this bay which often results in an

east – west trending channel. This gives rise to strong longshore and cross shore currents

which sometimes manifests as rip currents. A well defined offshore sandbar is usually

present at this station but is not seen in the following profiles.

Although recession of the backshore cliff was observed during the 2007 – 2008 period, the

long term trend at this region of the beach indicates that the beach is stable as evidenced by

the changes in beach width and volumes over a long term period (Figure 40). Periods of

erosion and accretion are observed but the overall trend is dynamic equilibrium.

Figure 39: Selected beach profiles for Blanchisseuse Bay Station 2 (west) for the period 2004 – 2008

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Ele

va

tio

n (

m)

2004 03 2004 11

2005 10 2006 07

2007 10 2008 01

2008 09

Blanchisseuse Bay

2004 - 2008 BM



Figure 40: Plot of Beach Width and Volume vs. Number of days for Las Cuevas Bay Station 2 (central) for the period March 1985 – October 2008

4.1.6 Grande Riviere Bay

Grande Riviere Bay is approximately 970 m long and arcuate in shape with varying beach

widths. The beach at the eastern section is much wider than at the western region with a

well defined berm and low backshore topography. The gradient at this section has a

relatively gentle backshore with a moderate to steep beach face, while the central to

western regions has a moderate slope and are backed by steep cliffs.

Four monitoring stations were established on this beach in 2000 as part of a project to

investigate the beach dynamics and risk posed to the leatherback egg clutches during the

nesting season (IMA, 2002). Figure 41 is an IKONOS (2007) image of Grande Riviere Bay

showing the location of the four IMA stations at this bay.

y = 0.0005x - 0.7166R² = 0.0921

y = 0.0002x + 0.1766R² = 0.0072

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BLANCHISSEUSE BAY - Station 2Changes in Beach Widths and Volumes

March 1989 - September 2008

Ch

ange

in B

eac

h W

idth

(m)

Ch

ange

in B

eac

h V

olu

me

(m

3 )




Figure 41: IKONOS image of Grande Riviere Bay showing Station locations (2007)

Station 1:

At the western section of Grande Riviere Bay (Station 1) the beach is in dynamic

equilibrium (Table 6). The backshore area is very stable due to the resistant metamorphic

rocks (Plate 12). The berm however, is very dynamic and experiences changes in sediment

elevations. There is also steepening of the seaward side of the berm as it migrates

landward (Figure 43).

1

3 2

4



Plate 12: West section of Grande Riviere Bay (Station 1) showing rocky backshore and narrow berm. (September 2007)

Wind approaches from the east with an average speed of 2.1 m/s (+/-0.87 m/s). Waves at

this station approaches from the northeast. Mean significant wave height is 1.0 m


is 1.1 m (+/- 0.24 m). Mean longshore current averages 13.2 cm/s (range 8.50 -23.30 cm/s,

+/- 5.46 cm/s) and flows northwest (Table 4).



Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The upper beach sediment is

Moderately well sorted, Near Symmetrical and Mesokurtic.

The mid-beach sample is classified as Sample is classified as Slightly Gravelly SAND with a



Moderately sorted, Near Symmetrical and Mesokurtic.

The lower beach sample is classified as Sample is classified as Sample is classified as

Gravelly SAND with a mean grain size of 0.72 mm, median grain size of 0.53 mm. The

sample consists of 21.72% Gravel (>2.0 mm), 78.28% Sand (0.0625 - 2.0 mm) and 0% Mud

(<0.0625 mm). The lower beach sediment is Poorly sorted, Strongly Coarse Skewed and

Platykurtic. The beach sediment at this station is predominantly coarse grained

(Figure 42).



Figure 42: Sediment grain-size distributions for Grand Riviere Station 1

Figure 43: Selected beach profiles for Grande Riviere Bay Station 1 (west) for the period 2004 – 2008

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Sediment size (Phi)

Grande Riviere Station 1 Sediment

UB

MB

LB

0

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-3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 pan

Per

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(%

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Sediment Histogram Grande Riviere Station 1

UB

MB

LB

4.0

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Ele

va

tio

n (

m)

2004 03 2006 04

2007 05 2007 10

2008 01 2008 04

Grande Riviere Bay Station 1

2004 - 2008

BM

The Profile at this station is not tied in to the National

Vertical Framework, i.e., Mean Sea Level



Station 2:

At the central region of the bay (Station 2) the beach is less dynamic and fairly stable

(Table 6; Figure 45). Movement and changing sediment levels on the beach face were not as

significant as observed in other stations on this bay. Erosion of the backshore cliffs was not

observed. Recession in the backshore cliff was not noted due to the geological composition

of the rocks. Plate 13 shows the beach at this region of the bay.

Plate 13: West section of Grande Riviere Bay (Station 2) showing moderately sloping beach (September 2007)


this station approaches from the northeast. Mean significant wave height is 0.96 m


is 1.1 m (+/- 0.39 m). Mean longshore current averages 10.8 cm/s (range 4.3-17.0 cm/s, +/-

4.18 cm/s) and flows in a predominantly northwesterly direction.

The upper beach sediment sample is classified as Sample is classified as Slightly Gravelly

SAND with a mean and median grain size of 0.50mm. The sample consists of 0.61% Gravel

(>2.0 mm), 99.39% Sand (0.0625 - 2.0 mm) and 0.0% Mud (<0.0625 mm). The upper beach

sediment is Moderately well sorted, Near Symmetrical and Mesokurtic.




moderately well sorted, Coarse Skewed and Leptokurtic.



The lower beach sample is classified as Sample is classified as Sample is classified as



lower beach sediment is Poorly sorted, Near Symmetrical and Mesokurtic. The beach

sediment at this station is predominantly coarse grained (Figure 44).


Figure 45: Selected beach profiles for Grande Riviere Bay Station 2 (central) for the period 2004 – 2008

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-3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 pan

Per

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(%

)


Sediment Histogram Grande Rivere Station 2

UB

MB

LB

3.0

4.0

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Ele

va

tio

n (

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2004 03 2006 06

2007 05 2007 10

2008 01 2008 04


2004 - 2008

BM

The Profile at this station is not tied

in to the National Vertical

Framework, i.e., Mean Sea Level



Station 3:

Dynamic equilibrium is exhibited at Station 3 (Table 6) also located in the central section of

the bay. The beach maintains a moderate to steep gradient. An offshore bar was observed

at this station in October 2007 (Figure 47). High wave energy makes it difficult to profile

this station beyond the near shore zone; therefore the profiles presented here represent

mainly the beach face. Plate 14 shows the beach at Grande Riviere at this region of the bay.

Plate 14: Beach at Grande Riviere showing well developed berm and river outflow channel (September 2007)

Wind speed at this location averages 2.07 m/s (+/-1.3 m/s). Waves in this station

approaches from the north-northeast. Mean significant wave height is 0.94 m (+/-0.27 m)

with a period of 6.8 s (+/-0.48 s) while the breaker height (plunging breaker) is 1.13 m

(+/- 0.4m). Mean longshore current averages 13.01 cm/s (range 4.3-26.30 cm/s,

+/- 6.92 cm/s) and flows northwest (Table 4).


size of 0.77 mm, median grain size of 0.81 mm. The sample consists of 0.88% Gravel

(>2.0 mm), 99.12% Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The upper beach

sediment is moderately well sorted, Fine Skewed and Leptokurtic.






moderately well sorted, Near Symmetrical and Leptokurtic.

The lower beach sample is classified as Sample is classified as Sample is classified as Sandy

GRAVEL with a mean and median grain size of 1.44 mm. The sample consists of 33.25%


beach sediment is poorly sorted, Near Symmetrical and Mesokurtic. The sediment at this

station is predominantly coarse grained but very coarse in the lower beach region. The

high gravel component in the lower beach is possibly from sediments brought down from

the hillside by the river outflow immediately adjacent to the profile (Figure 46).


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Sediment size (Phi)


UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 pan

Per

cen

tage

(%

)



UB

MB

LB



Figure 47: Selected beach profiles for Grande Riviere Bay Station 3 (central) for the period 2004 – 2008

Station 4:

At the eastern section of Grande Riviere Bay (Station 4) the berm is widest (Plate 15).

Plate 15: Grande Riviere Bay Station 4 showing wide beach and distinct berm crest (September 2007)

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68


Ele

va

tio

n (

m)

2006 06 2007 05

2007 10 2008 01

2008 04


2004 - 2008 BM





Wind speed at this location averages 2.1 m/s (+/-0.97 m/s). Waves at this station

approaches from the north- northeast. Mean significant wave height is 0.8 m (+/-0.32 m)

with a period of 7.4 s (+/-0.65 s) while the breaker height (plunging breaker) is 1.0 m

(+/- 0.45 m). Mean longshore current averages 11.1 cm/s (range 8.5-14.73 cm/s,

+/- 2.03 cm/s) and flows northwest.

From Table 5 it is shown that the upper beach sediment sample is classified Slightly

Gravelly SAND with a mean and median grain size of 0.55mm. The sample consists of


The upper beach sediment is moderately well sorted, Near Symmetrical and Mesokurtic.



(0.0625 - 2.0 mm) and 0.01% Mud (<0.0625 mm). The mid-beach sediment is moderately

sorted, Near Symmetrical and Mesokurtic.

The lower beach sample is classified as Sample is classified as Gravelly SAND with a mean

and median grain size of 0.91 mm. The sample consists of 24.2% Gravel (>2.0 mm), 66.75%

Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The lower beach sediment is Poorly

sorted, Near Symmetrical and Platykurtic. The sediment at this station is predominantly

coarse grained. The gravel component in the lower beach possible originating from the

Grande Riviere River which empties further east of the profile (Figure 48).


0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)


UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 pan

Per

cen

tage

(%

)



UB

MB

LB



Figure 49: Selected beach profiles for Grande Riviere Bay Station 4 (east) for the period 2004 – 2008

The changing flow of the Grande Riviere River sometimes traverses parallel to the

shoreline dissecting this profile. This occasionally results in stagnation of the river flow due

to berm development during the accretionary cycle of the bay in the months April –

October. The beach face is almost always steeply sloping with a low positive gradient from

the backshore to the berm crest. A distinct plunge point is also a feature of this profile

(Figure 49). An offshore bar creates a near shore channel that strongly influences

longshore currents.

4.1.7 Salybia Bay (Toco)

Salybia Bay is located on the north eastern tip of Trinidad and is approximately 700 m long.

Figure 50 is an IKONOS (2007) image of Salybia Bay showing the location of the IMA

station on this bay and the waves breaking over the reef. The beach has a moderate slope

(Plate 16) and contains bio-lithics (coral fragments and shells) which originates from the

action of the waves on the reef. Plunging breakers break on the reef crest, after which

surging breakers develop in the lagoon which has little uprush.

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100


Ele

va

tio

n (

m)

2004 03 2006 06

2007 05 2007 10

2008 01 2008 04


2004 - 2008 BM

River

channel





Figure 50: IKONOS image of Salybia Bay showing Station location (2007)

Plate 16: Beach at Salybia Bay, Toco (October 2007)



Wind speed at this location averages 4.5 m/s (+/-5.73 m/s) and ranges between

0.0 -17.1 m/s approaching from the east. Waves approach from the northeast with a mean

significant wave height of 0.4 m (+/-0.26 m) and a period of 7.6 s (+/- 0.8 s) while the

breaker height (surging breaker) is 0.47 m (+/- 0.31 m). Mean longshore current averages

38.5 cm/s (range 21.3-65.7 cm/s, +/- 14.67 cm/s), and flows to the southwest (Table 4).



Sand (0.0625 - 2.0 mm) and 0.01% Mud (<0.0625 mm). The upper beach sediment is well




2.0 mm) and 0% Mud (<0.0625 mm). The mid-beach sediment is well sorted, Near




72.74% Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The lower beach sediment is

poorly sorted, Strongly Coarse Skewed and Mesokurtic (Figure 51).

Figure 51: Sediment grain-size distributions for Salybia Station 2

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Salybia Station 2 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 pan

Per

cen

tage

(%

)


Sediment Histogram for Salybia

UB

MB

LB



Figure 52: Selected beach profiles for Salybia Bay for the period 2004 – 2008

Un-even seabed morphology (which includes reefs) creates strong southwesterly

longshore currents. This bay is generally in dynamic equilibrium (Figure 52) but

experienced a 0.80 m cliff recession during 2004 (Table 6) which may have been as a result

of a high wave energy event.

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 128 136 144 152 160 168 176 184


Ele

va

tio

n (

m)

2004 03 2005 05

2007 02 2008 01

2008 04

Salybia Bay

2004 - 2008

BM

Reef





4.2 EAST COAST

The east coast of Trinidad extends from Galera Point in the north to Galeota Point in the

South.

Table 7 summarizes the littoral processes occurring on beaches and bays along this

coastline, Table 8 presents data on the sediment grain size properties while Table 9

presents data on shoreline erosion/accretion processes for the period 2004 – 2008.

The beaches on the east coast are generally in a state of dynamic equilibrium. The

northernmost station, Guayamara Bay is a high wave energy environment with a steep

beach face and low cliff. The gradient of this beach face is in equilibrium with the oncoming

wave energy, and as such, erosion was not experienced during 2004 – 2008. The northern

to central sections of Cocos Bay also did not experience any erosion during 2004 – 2008.

However, erosion was observed in the southern section of Cocos Bay. The beach at Cocos

Bay is part of a barrier-beach system which impounds the Nariva Swamp. The coastline

therefore has a very gentle gradient and is composed of weakly consolidated backshore

sands that are very easily eroded. The proximity of the shoreline to the main access road

(Manzanilla-Mayaro road) and the continued erosion in this region of the bay resulted in

the construction of a rip rap revetment in 2006. The benchmark at IMA’s station at north

Mayaro did not indicate any erosion although cliff recession was observed on the cliffs

further north of this station. The south station experienced undercutting at the base of the

cliffs and subsequent slumping, resulting in erosion.



Table 7: Summary Littoral Processes for East Coast Beaches of Trinidad for the period 2004

Beach/Bay Station

Location

Wind Speed

Wind Direction


Current Direction

(s) (cm/s)

Mean Range STD

Mean RANGE STD

Direction Mean Range STD

Mean Range STD Mean Range STD

Guayamara Northeast 3.7 1.90-9.8 2.54 SE 0.78 0.5-1.1 0.19 NE 0.88 0.4-1.25 0.32 6.79 5-7.8 0.79 18.6 4-50.2 13.34 SE

Saline West 3.68 1-11.9 3.76 SE 0.24 0.1-0.3 0.07 SW 0.26 0.1-0.3 0.07 7.01 5.3-8.1 0.94 21.62 9.07-46.67 12.58 W

East 3.1 1.0-10.0 2.69 E 0.3 0.2-0.5 0.12 SW 0.32 2.0-0.55 0.12 7.3 6.2 - 8.10 0.67 15.05 6.80-24.5 6.23 W

Cocos 1- North 3.81 2.7-6.8 1.32 E 0.48 0.3-0.65 0.12 E 0.57 0.3-0.9 0.19 7.35 6.0-8.5 0.81 13.79 5.67-29.17 6.57 SE

2- Central 3.96 2.7-8.0 1.61 E 0.54 0.3-0.85 0.15 E 0.63 0.3-1.0 0.2 7.78 6.7-9.0 0.75 17.11 8.53-35.0 8.63 SW

3 3.65 1.5-9.1 1.62 E 0.54 0.3-1.2 0.22 E 0.63 0.4-1.3 0.25 7.42 6.1-9.7 0.85 13.65 8.17-25.67 5.11 SW

4a 4.8 2.1-10.4 2.47 E 0.49 0.3-0.8 0.18 E 0.6 0.3-1.0 0.25 7.24 6.2-8.5 0.82 12.33 6.8-19.2 3.8 SW

5-South 3.25 1.6-6.0 1.17 E 0.5 0.3-.75 0.15 NE 0.59 0.3-1.0 0.22 7.44 6.3-8.5 0.72 14.78 4.27-39.47 9.66 SW

Mayaro North 2.9 1.5-5.0 1.17 E 0.47 0.3-0.8 0.16 SE 0.51 0.4-0.8 0.16 7.9 6.5-10.6 1.46 11.57 4.7-21.0 5.39 SW

Central 3.04 1.9-6.0 1.02 E 0.74 0.3-1.0 0.23 E 0.84 0.3-1.0 0.25 7.64 6.5-10.4 0.93 16.93 9.6-29.87 6.4 SE

South 3.1 2.0-5.0 0.9 E 0.75 0.4-1.20 0.24 E 0.85 0.45-1.25 0.26 8 6.30-11.50 1.19 16.3 2.1-40.0 8.47 SE



Table 8: Summary grain size for East Coast Beaches of Trinidad


LOCATION



GRAVEL >2.0mm

SAND (0.0625 - 2.0 mm)

MUD < 0.0625mm

Guayamara Bay


SAND


SAND


SAND

Saline Bay 1 East

UB 1.10 0.47 1.10 0.47 0.75 0.59 Moderately

sorted 0.00 1.00 0.55 99.45 0.00


MB 1.18 0.44 1.18 0.44 1.09 0.47 Poorly sorted -0.05 0.90 2.19 97.78 0.03 Slightly Gravelly

SAND


Cocos Bay 1 North

UB 1.82 0.28 1.82 0.28 0.73 0.60 Moderately

sorted -0.15 1.40 1.85 98.13 0.02



sorted 0.00 1.00 0.96 98.94 0.10


LB 1.78 0.29 1.78 0.29 0.72 0.61 Moderately well

sorted 0.00 1.00 0.32 99.58 0.10


Cocos Bay 2 Central (Spit)

UB 2.80 0.14 2.80 0.14 0.31 0.81 Very well sorted 0.00 1.00 0.00 99.83 0.17 Gravelly SAND

MB 2.67 0.16 2.67 0.16 0.33 0.79 Very well sorted 0.00 1.00 0.45 99.55 0.00 Slightly Gravelly

SAND


SAND

Cocos Bay 3 Central


sorted -0.18 1.55 1.64 98.31 0.05


MB 1.49 0.36 2.00 0.25 1.40 0.38 Poorly sorted -0.56 2.27 11.50 88.43 0.07 Slightly Gravelly

SAND


Cocos Bay 4 South

(Rip Rap)


SAND


sorted -0.21 1.73 3.31 96.67 0.02



Cocos Bay 5 South

UB 2.76 0.15 0.00 1.00 0.00 1.00 Very well sorted 0.00 0.00 0.00 0.00 0.00 SAND


SAND


SAND



Table 8: Summary grain size for East Coast Beaches of Trinidad Cont’d.


LOCATION



GRAVEL >2.0mm

SAND (0.0625 - 2.0 mm)

MUD < 0.0625mm

Mayaro Bay 2 Central

UB 2.23 0.21 2.23 0.21 0.49 0.71 Well sorted 0.00 1.00 0.02 99.97 0.02 Slightly Gravelly SAND

MB 2.50 0.18 2.50 0.18 0.47 0.72 Well sorted 0.00 1.00 0.35 99.58 0.07 Slightly Gravelly SAND

LB 2.56 0.17 2.56 0.17 0.37 0.77 Well sorted 0.00 1.00 0.93 99.07 0.00 Slightly Gravelly SAND

Mayaro Bay 3 South

UB 2.23 0.21 2.24 0.21 0.55 0.68 Well sorted -0.19 1.58 2.08 97.92 0.00 Slightly Gravelly SAND

MB 2.13 0.23 2.13 0.23 0.57 0.67 Well sorted 0.00 1.00 0.47 99.47 0.07 Slightly Gravelly SAND

LB 2.33 0.20 2.33 0.20 0.42 0.75 Well sorted 0.00 1.00 1.93 98.00 0.07 Slightly Gravelly SAND



Table 9: Summary Shoreline stability status of East Coast Beaches of Trinidad for the period 2004- 2008

Beach/Bay IMAs Beach

Monitoring Station

Location





2004 2005 2006 2007 2008

Guayamara Northeast DE DE DE DE DE

Saline East DE DE DE DE DE

West DE DE DE DE DE

Cocos North DE DE DE DE DE


South (77km mark) DE -1.00 DE DE DE

South (79km mark) -0.40 -3.20 Riprap

South (82km mark) DE -1.20 -1.15 -1.15 -4.80

Mayaro North DE DE DE DE DE


South DE -0.50 -0.50 DE DE

4.2.1 Guayamara Bay

Guayamara Bay is located on the north eastern coastline of Trinidad. It is a very high

energy bay with steep beach gradients. There is a large rock approximately 150 m offshore

at the central section of the bay (Plate 17). Waves approaching from the Atlantic refract

around this rock from the north-eastern and south-western ends creating an environment

of strong currents. Figure 53 is an IKONOS (2007) image of Guayamara Bay showing the

location of the IMA station at this bay.



Figure 53: IKONOS image of Guayamara Bay showing Station location (2007)



Plate 17: Guayamara Bay, showing wide berm (October 2007)


this bay approach from the east. Mean significant wave height is 0.78 m (+/-0.19 m) with a

period of 6.79 s (+/-0.79 s) while the breaker height (plunging breaker) is 0.88 m

(+/- 0.32 m). Mean longshore currents are strong, averaging 18.6 cm/s

(range 4.0-50.2 cm/s, +/- 13.34 cm/s) and flows south (Table 7).




The beach sediment is well sorted, Near Symmetrical and Mesokurtic.



99.08% Sand (0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The beach sediment is

moderately well sorted, Coarse Skewed and Leptokurtic.



99.18% Sand (0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The beach sediment is well

sorted, Near Symmetrical and Mesokurtic (Figure 54).



Figure 54: Sediment grain-size distributions for Guayamara Bay

The high wave energy is buffered by the steep gradient and as such, the beach at this

station is in dynamic equilibrium (Table 9). The beach profiles conducted for 2004 – 2008

illustrate the dynamics of the elevation of sediment at this bay which occurs mainly in the

lower beach region (Figure 55).

Figure 55: Selected beach profiles for Guayamara Bay for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0.0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Guayamara Bay Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)


Sediment Histogram for Guayamara

UB

MB

LB

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64

Ele

va

tio

n (

m)


2004 03

2005 05

2007 02

2008 01

2008 04

Guayamara Bay

2004 - 2008

BM



Figure 56: Plot of Beach Width and Volume vs. Number of days for Guayamara Bay for the period March 1985 – April 2008

Although recession of the backshore cliff was observed during the 2007 – 2008 period, the

long term trend at this region of the beach indicates that the beach is stable as evidenced by

the fairly horizontal trend lines in beach width and volumes over a long-term period

(Figure 56). While periods of erosion and accretion are observed, the overall trend is

dynamic equilibrium.

4.2.2 Saline Bay

Saline Bay is located on the north eastern coastline of Trinidad and is 2.1 km long. A rocky

platform about 4 m high with some coral communities is located approximately 2 km

offshore. The rocky reef is oriented approximately parallel to the coastline and trends SW-

NE. The reef reduces wave energy as it approaches the coastline (IMA, 1999). Figure 57 is

an IKONOS (2007) image of Saline Bay showing the location of the two IMA stations on this

bay.

y = -0.0000x + 0.1507R² = 0.0035

y = -0.0000x - 2.3436R² = 0.0001

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10.00.10.20.30.40.50.60.70.80.91.0

0

50

0

10

00

15

00

20

00

25

00

30

00

35

00

40

00

45

00

50

00

55

00

60

00

65

00

70

00

75

00

80

00

85

00





GUAYAMARA BAYChanges in Beach Widths and Volumes

March 1985 - April 2008

Bea

ch W

idth

(m)

Bea

ch V

olu

me

(m

3)




Figure 57: IKONOS image of Saline Bay showing Station locations (2007)

Station 1:

Plate 18 shows the beach at the northern section of the bay (Station 1). The shore face is

moderately sloping with a gentle surf zone (Plate 18). Recession in the backshore cliff was

not observed (Figure 59), and the bay exhibited dynamic equilibrium during the study

period (Table 9).

2 1



Plate 18: Beach at Saline Bay Station 1 (October 2007)

Wind speed averages 3.1 m/s (+/-2.69 m/s) and ranges between 1.0–10.0 m/s

approaching from the east-southeast. Waves approach from the southeast with a mean

significant wave height is 0.30 m (+/-0.12 m) and a period of 7.3 s (+/- 0.67 s), while the


15.05 cm/s (range 6.80-24.5 cm/s, +/- 6.23 cm/s) and flows to the west (Table7).




upper beach sediment is moderately sorted, Near Symmetrical and Mesokurtic.



2.0 mm) and 0.03% Mud (<0.0625 mm). The mid-beach sediment is poorly sorted, Near

Symmetrical and Platykurtic.



85.94% Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The lower beach sediment is

poorly sorted, Coarse Skewed and Platykurtic (Figure 58).



Figure 58: Sediment grain-size distributions for Saline Bay Station 1

Figure 59: Selected beach profiles for Saline Bay Station 1 (east) for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0.0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Saline Bay Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)


Sediment Histogram for Saline Bay

UB

MB

LB

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 128 136 144 152 160 168 176 184


Ele

va

tio

n (

m)

2004 03 2005 05

2006 06 2008 01

2008 04

Saline Bay Station 1

2004 - 2008

BM



Station 2:

Station 2 is located in the vicinity of the fishing depot (Plate 19). Selected profiles for this

section of the beach indicate that the beach is in dynamic equilibrium (Figure 60). There is

little variation in the sand elevation at this profile. The maximum variation is observed at

28-36 m from the benchmark. The beach at this station has a relatively gentle to moderate

slope. While no sediment data was available for this station, the sediment at Station 1 gives

representative sediment characteristics for this section of the bay.

Plate 19: Beach at Saline Bay Station 2 (October 2007)

Wind speed averages 3.68 m/s (+/-3.76 m/s) and ranges between 1.0–11.9 m/s

approaching from the east-southeast. Waves approach from the southeast with a mean

significant wave height is 0.24 m (+/-0.07 m) and a period of 7.01 s (+/- 0.94 s) while the


21.62 cm/s (range 9.07 – 46.67 cm/s, +/- 12.58 cm/s) and flows to the west (Table 7).



Figure 60: Selected beach profiles for Saline Bay Station 2 (west) for the period 2004 – 2008

4.2.3 Cocos Bay

Cocos Bay is located on the eastern coast of Trinidad between Manzanilla Point and Radix

Point. The bay is backed by the Nariva Swamp and three rivers empty in the northern,

central and southern parts of the bay. The L’Ebranche River is located in the northern end

of the bay, Nariva River in the central region and Ortoire River in the southern end. The

Manzanilla beach in Cocos Bay is a barrier beach with the Cocal spit in the central section.

Figure 61 is an IKONOS (2007) image of Cocos Bay showing the location of the five IMA

stations on this bay.

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100


Ele

va

tio

n (

m)

2004 03 2005 05

2007 02 2008 01

2008 04

Saline Bay Station 2

2004 - 2008

BM



Figure 61: IKONOS image of Cocos Bay showing Station locations (2007)

Station 1:

Station 1 at Cocos Bay is located south of the Manzanilla Bay facilities (Plate 20). During

2004 – 2008 this section of the bay exhibited dynamic equilibrium (Table 9) with subtle

changes to the profile transects (Figure 63).

1

2

3

4

5



Plate 20: Cocos Bay Station 1 North, showing eroding backshore (August 2007)


this station approach from the east. Mean significant wave height is 0.48 m (+/-0.12 m)

with a period of 7.35 s (+/-0.81 s) while the breaker height (spilling breaker) is 0.57 m


+/- 6.57 cm/s) and flows south (Table 7).




The sediment is moderately sorted, Coarse Skewed and Leptokurtic.



2.0 mm) and 0.1% Mud (<0.0625 mm). The sediment is moderately well sorted, Near




(0.0625 - 2.0 mm) and 0.1% Mud (<0.0625 mm). The sediment is moderately well sorted,




Figure 62: Sediment grain-size distributions for Cocos Bay Station 1

The long term trend of changes in beach width and volume at this region of the beach

indicate that the beach is in a state of erosion as determined by the negative gradient of the

best fit line (Figure 64). Due to erosion, the benchmark was set back and as such, volume

changes could not have been determined. Since February 1985 both cyclic and seasonal

trends are observed in the time-series plot. However, fairly steady declines in the beach

width over 23 years inarguably indicate the state of erosion of this beach. Erosion of the

low cliff is occurring further north of this site up to the L’Ebranche River Mouth.

Figure 63: Selected beach profiles for Cocos Station 1 (north) for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Cocos Bay Station 1 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)


Sediment Histogram for Cocos Station 1

UB

MB

LB

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120 124


Ele

va

tio

n (

m)

2004 02 2004 10

2005 08 2006 02

2006 07 2007 10

2008 01 2008 10

Cocos Bay Station 1

2004 - 2008

BM



Figure 64: Plot of Beach Width and Volume vs. Number of days for Cocos Bay Station 1 for the period March 1985 – April 2008

Station 2:

Station 2 is located on the Cocal Spit north of the Nariva River mouth in the central section

of the bay. The beach at this region of the bay has a very low gradient and backed by beach

runners and a dense coconut plantation (Plate 21). During 2004 – 2008 this beach

exhibited dynamic equilibrium (Table 9) reflected by the subtle variations in the profile

transects (Figure 66).

y = -0.0017x + 2.8210R² = 0.2693

y = -0.0013x + 4.806R² = 0.2422

-25

-20

-15

-10

-5

0

5

10

15

20

-25

-20

-15

-10

-5

0

5

10

15

200

50

0

10

00

15

00

20

00

25

00

30

00

35

00

40

00

45

00

50

00

55

00

60

00

65

00

70

00

75

00

80

00

85

00

90

00





COCOS BAY - Station 1Changes in Beach Widths and Volumes

February 1985 - November 2008

Be

ach

Wid

th(m

)

Be

ach

Vo

lum

e (

m3 )




Plate 21: Cocos Bay Station 2 Central, showing wide gently sloping beach (August 2007)



with a period of 7.78 s (+/-0.75 s), while the breaker height (spilling breaker) is 0.63 m


+/- 8.63 cm/s) and flows southeast (Table 7).

From Table 8 it is shown that the upper beach sediment sample is classified as Gravelly

SAND with a mean and median grain size of 0.14 mm. The sample consists of 0% Gravel

(>2.0 mm), 99.83% Sand (0.0625 - 2.0 mm) and 0.17% Mud (<0.0625 mm). The upper

beach sediment is Very well sorted, Near Symmetrical and Mesokurtic.


size of 0.16mm. The sample consists of 0.45% Gravel (>2.0 mm), 99.55% Sand (0.0625 - 2.0

mm) and 0% Mud (<0.0625 mm). The mid-beach sediment is Very well sorted, Near




(0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The lower beach sediment is Very well

sorted, Near Symmetrical and Mesokurtic. The mean and median grain sizes at this region

of the bay along the transect line indicate that the sediment is generally fine grained

(Figure 65).




Figure 66: Selected beach profiles for Cocos Station 2 (central) for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)


UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)



UB

MB

LB

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120 124


Ele

va

tio

n (

m)

2004 02 2004 10

2005 08 2007 10

2008 01 2008 10

Cocos Bay Station 2

2004 - 2008

BM





Station 3:

Station 3 is located north of the Nariva River mouth and approximately 4 km south of

Station 2 in the central section of the bay. The beach at this region of the bay has a low

gradient and usually covered with shell fragments along the upper to mid region and is

backed by the coconut plantation and a low eroding cliff (Plate 22). Cuspates consisting of

fragmented and disarticulated shells (mainly bivalves) are characteristic of this stretch of

coastline.

Plate 22: Cocos Bay Station 3 Central, showing wide gently sloping beach covered with shells along the upper-mid beach (August 2007)

Wind speed approaches from the east and averages 3.96 m/s (+/-1.61 m/s). Waves at this

station approach from the east. Mean significant wave height is 0.54 m (+/-0.15 m) with a

period of 7.78 s (+/-0.75 s), while the breaker height (spilling breaker) is 0.63 m






The upper beach sediment is moderately well sorted, Coarse Skewed and Very Leptokurtic.




sediment is Poorly sorted, Strongly Coarse Skewed and Very Leptokurtic.




and median grain size of 0.27 mm. The sample consists of 8.28% Gravel (>2.0mm), 91.71%

Sand (0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The lower beach sediment is poorly

sorted, Strongly Coarse Skewed and Very Leptokurtic. The gravel components in the grain

size are attributed to the shell fragments in the sediment. The sediment at this beach

however is predominantly medium grained sand (Figure 67).


In September 2005, a temporary benchmark was established landward of the permanent

station (Figure 68). During 2004 – 2008 the beach at this region of the bay exhibited

dynamic equilibrium with the exception of a 1.0 m recession in the backshore cliff. Changes

to the beach width from February 1990 – October 2008 show that the beach is in dynamic

equilibrium even though seasonal declines in the beach volumes are observed (Figure 69).

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)


UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)



UB

MB

LB



Figure 68: Selected beach profiles for Cocos Station 3 (south) for the period 2004 – 2008

Figure 70 shows the maximum and minimum elevations of the sand levels during the

period 2004 – 2008. Maximum change in elevation of 0.60 m was observed at 36 m from

the benchmark. The average profile elevation indicates the dynamic equilibrium at this

section of the coastline (Figure 70).

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

-44 -36 -28 -20 -12 -4 4 12 20 28 36 44 52 60 68 76 84 92 100 108 116


Ele

va

tio

n (

m)

2004 02 2004 10

2005 08 2007 10

2008 01 2008 10

Cocos Bay Station 3

2004 - 2008

BM



Figure 69: Plot of Beach Width and Volume vs. Number of days for Cocos Bay Station 3 (central) for the period February 1990 – October 2008

y = 0.0002x + 0.6481R² = 0.0057

y = -0.0021x - 5.9719R² = 0.4085

-25

-20

-15

-10

-5

0

5

10

15

20

-25

-20

-15

-10

-5

0

5

10

15

200

50

0

10

00

15

00

20

00

25

00

30

00

35

00

40

00

45

00

50

00

55

00

60

00

65

00

70

00







Ch

ange

in B

each

Wid

th(m

)

Ch

ange

in B

eac

h V

olu

me

(m

3 )




Figure 70: Maximum and Minimum beach elevations for Cocos Bay Station 3 (central) 2004 – 2008

Station 4:

Further south of the Nariva River and as far south as the Ortoire River, erosion has been an

ongoing phenomenon. Station 4 is located just north of the Ortoire River. Erosion over the

years threatened to breach the main road and wave run up on the swash zone had already

begun to encroach onto the roadway. Response from government agencies was almost

immediate as solutions were investigated to retard the erosion. The problem exacerbated

in the early 2000’s, and in 2004 and 2005, recession of the low cliff was reported to be

-0.40 and -3.20 m respectively (Table 9). Imminent threat to the main road prompted the

Ministry of Works Drainage Division to construct a limestone rip rap revetment in 2006

(Plate 23).

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84

MAXIMUM

MINIMUM

AVE R AGE


C OC OS B AY, S T AT ION 3

2004 - 2008

EL

EV

AT

ION

(m

)

D IS T ANC E (m)




Plate 23: Beach at Cocos Bay Station 4 showing Rip Rap revetment and gently sloping beach (April 2008)

The revetment which spans a length of approximately 2.2 km is now being extended

further south with a gap in between of almost 1 km. From initial construction to 2008, the

revetment has remained relatively stable but subsequently started showing signs of

displacement at the base. Flanking at the northern and southern ends of the revetment is

evident. It is envisaged that the structure will have to be extended further south to close

the gap that exists, which ultimately will erode if left unprotected.



with a period of 7.24 s (+/-0.82 s), while the breaker height (spilling breaker) is 0.6 m






upper beach sediment is well sorted, Near Symmetrical and Mesokurtic.



2.0 mm) and 0.02% Mud (<0.0625 mm). The mid-beach sediment is moderately well

sorted, Coarse Skewed and Very Leptokurtic.






sorted, Strongly Coarse Skewed and Platykurtic. The gravel component at this station is

also attributed to the shell fragments in the sediments. The beach sand is predominantly

medium grained (Figure 71).


Figure 72: Selected beach profiles for Cocos Station 4 (south) for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)


UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)



UB

MB

LB

6.0

6.5

7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120


Ele

va

tio

n (

m)

2005 08 2006 02

2007 10 2008 01

2008 04 2008 10

Cocos Bay Station 4

2004 - 2008 BM





Figure 72 shows the selected profiles at Station 4 which is located almost at the centre of

the revetment. The beach has maintained a gentle slope and there is insignificant variation

in its dynamics after the wall was constructed from 2006 – 2008. The anomaly at this

station is that the longshore currents flow predominantly in a northerly direction possibly

due to the effect of the discharge from the Ortoire River which lies to the south of the

station, or a bathymetric feature in the near shore zone.

Station 5:

The southern end of the bay terminates at the Ortoire River and Point Radix. Station 5 is

located at approximately 400 – 500 m north of the Ortoire River Mouth. This part of the

coastline has been eroding continuously over the past 4 years as evidenced by the fallen

coconut trees on the upper and mid-beach zones (Plate 24).

Plate 24: Beach at Cocos Bay Station 5 showing fallen coconut trees as a result of erosion. (April 2008)

The wind at this station approaches from the east with an average speed of 3.25 m/s

(+/-1.17 m/s). Waves approach from the east-northeast with a significant wave height of

0.5m (+/-0.15 m). Wave period averages 7.44s (+/-0.72 s), while the breaker height

(spilling breaker) is 0.59 m (+/- 0.22 m). Mean longshore current averages 14.78 cm/s

(range 4.27-39.47 cm/s, +/- 9.66 cm/s) and flows southeast (Table 7).



From Table 8 it is shown that the upper beach sediment sample is classified as SAND with a

mean and median grain size of 0.15 mm. The sample consists of 0% Gravel (>2.0 mm),

98.85% Sand (0.0625 - 2.0 mm) and 1.15% Mud (<0.0625 mm). The upper beach sediment

is Very well sorted, Near Symmetrical and Very Platykurtic.



2.0 mm) and 1.09% Mud (<0.0625 mm). The mid-beach sediment is moderately well


The lower beach sample is classified as Slightly Gravelly SAND with a median grain size of

0.15 mm. The sample consists of 0.03% Gravel (>2.0 mm), 99.3% Sand (0.0625 - 2.0 mm)

and 0.67% Mud (<0.0625 mm). The lower beach sediment is well sorted, Near Symmetrical

and Mesokurtic. The beach sediment at this station is predominantly fine grained

(Figure 73).


During 2005-2007 the erosion rate was 1.20m/yr and in 2008 a rate of 4.80m/yr was

observed. Over the study period, 2004 was the only year when no erosion of the backshore

cliff was observed (Table 9). Figure 74 shows selected profiles at this station and the

receding coastline. This trend is supported by the long term changes to beach width trend

at this station as evidenced by the negative best fit line (Figure 75). Even though some

increases are seen in the beach width due to seasonal trends, since 1992 the data shows a

general decrease in beach width and beach volume at this station. This data indicates that

this section of the bay is in a state of erosion.

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)


UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 pan

Per

cen

tage

(%

)



UB

MB

LB



Figure 74: Selected beach profiles for Cocos Station 5 (south) for the period 2004 – 2008.

Figure 75: Plot of Beach Width and Volume vs. Number of days for Cocos Bay Station 5 (south) for the period January 1992 – November 2008

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120 124


Ele

va

tio

n (

m)

2004 02 2004 10

2005 08 2006 02

2007 10 2008 01

2008 10

Cocos Bay Station 5

2004 - 2008

BM

y = -0.0013x - 5.7232R² = 0.4055

y = -0.004x - 5.5707R² = 0.8227

-35

-30

-25

-20

-15

-10

-5

0

5

-35

-30

-25

-20

-15

-10

-5

0

5

0

50

0

10

00

15

00

20

00

25

00

30

00

35

00

40

00

45

00

50

00

55

00

60

00

65

00

Ch

ange

in B

eac

h W

idth

(m

)






January 1992 - November 2008


Ch

ange

in B

each

Vo

lum

e (

m3)



4.2.4 Mayaro Bay

Mayaro bay is approximately 17 km long extending from Point Radix in the north to Point

Galeota in the south. In the extreme northern region, the bay is backed by the high cliffs of

Point Radix. The central section consists of low cliffs and a coastal plain which develop into

steeper and higher cliffs in the southern part of the bay. Figure 76 is an IKONOS (2007)

image of Mayaro Bay showing the location of the three IMA stations on this bay.

Figure 76: IKONOS image of Mayaro Bay showing Station locations (2007)

1

2

3



Coconut palms are the main vegetation together with low shrubs and grasses (Plate 25). In

the central part of the bay most residential properties are located just beyond the high

water mark, but in some instances within the active littoral zone.

Station 1:

In the northern part of this bay (Station 1) erosion has been occurring. The beach is backed

by a coconut plantation and a low cliff (Plate 25). The beach maintains a gentle gradient

and rows of spilling breakers are characteristic of this bay.

Plate 25: Beach at North Mayaro Bay Station 1, (September 2004)


this station approach from the east-southeast. Mean significant wave height is

0.47 m (+/-0.16 m) with a period of 7.9 s (+/-1.46 s), while the breaker height (plunging


(range 4.7-21.0 cm/s, +/- 5.39 cm/s) and flows predominantly southwest (Table 7).

Recession of the backshore cliff was not observed; however, lowering of the sand levels is

noted. The seasonal changes occurring on this section of the bay in relation to sediment

elevation still classifies this region being in dynamic equilibrium. Figure 77 shows selected

profiles for this bay. Due to access restrictions, this station has not been monitored since

November 2007, and no sediment data was available for the study period.



Figure 77: Selected beach profiles for Mayaro Bay Station 1 (north) for the period 2004 – 2007

Station 2:

The central part of the bay (Station 2) also exhibits a low gradient and is backed by very

low cliffs and residential properties (Plate 26). This region of the bay is relatively stable

and is in dynamic equilibrium (Table 7).

Plate 26: Mayaro Bay Station 2, showing gently sloping wide berm (February 2007)

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120


Ele

va

tio

n (

m)

2004 01 2004 02

2004 03 2004 04

2004 10 2006 10

2007 11

Mayaro Bay Station 1

2004 - 2008

BM





The wind at this station approaches from the east and averages 3.04 m/s (+/- 1.02 m/s).

Waves approach from the east with a mean significant wave height of 0.52 m (+/-0.18 m)

and a period of 4.87s (+/-3.44 s), while the breaker height (plunging breaker) is 0.74 m


+/- 6.4 cm/s) and flows south (Table 7).




The upper beach sediment is well sorted, Near Symmetrical and Mesokurtic.



(0.0625 - 2.0 mm) and 0.07% Mud (<0.0625 mm). The mid-beach sediment is well sorted,

Near Symmetrical and Mesokurtic.



(0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The sediment is well sorted, Near

Symmetrical and Mesokurtic. The beach sediment at this region is predominantly fine

grained (Figure 78).

Figure 78: Sediment grain-size distributions for Mayaro Bay Station 2

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Mayaro Bay Station 2 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)


Sediment Histogram for Mayaro Station 2

UB

MB

LB



Although the two profiles conducted in 2008 show lower elevations, the profile is expected

to show recovery which will be ascertained by further monitoring. Generally, there is little

fluctuation in the sand elevations at this station (Figure 79). The beach has a very gentle

slope and is relatively wide during low tide conditions. Strong longshore and cross shore

currents are normal at this bay.

Long term beach width trend analysis, spanning nearly 23 years of data, for this region of

the bay indicates that the beach is stable (Figure 80). The trend shows that the changes to

volume are fairly constant while the beach width has a small positive gradient in the best-

fit line.

Figure 79: Selected beach profiles for Mayaro Station 2 (central) for the period 2004 – 2008

-2.0

-1.0

0.0

1.0

2.0

3.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120 124


Ele

va

tio

n (

m)

2004 01 2005 01

2005 08 2006 10

2007 10 2008 01

2008 06


2004 - 2008 BM



Figure 80: Plot of Beach Width and Volume vs. Number of days for Mayaro Bay Station 2 (central) for the period March 1985 – April 2008

Station 3:

Station 3 is located north of the Palmiste River (locally referred to as Indian Bay) and the

beach is relatively wide at low tide (Plate 27). The beach has a gentle slope and strong

southerly longshore currents. Rip currents are also characteristic of this area.

Plate 27: Mayaro Bay Station 3, showing gently sloping wide berm (February 2007)

y = 0.0012x - 5.9319R² = 0.0737

y = 0.0002x + 0.1826R² = 0.0022

-25

-20

-15

-10

-5

0

5

10

15

20

25

30

35

40

-25

-20

-15

-10

-5

0

5

10

15

20

25

30

35

40

0

50

0

10

00

15

00

20

00

25

00

30

00

35

00

40

00

45

00

50

00

55

00

60

00

65

00

70

00

75

00





MAYARO BAY - Station 2Changes in Beach Widths and Volumes


Be

ach

Wid

th(m

)

Be

ach

Vo

lum

e (

m3 )





this station approaches from the east. Mean significant wave height is 0.75 m (+/-0.24 m)

with a period of 8.0 s (+/-1.19 s), while the breaker height (plunging breaker) is 0.85 m


+/- 8.47 cm/s) and flows predominantly south (Table 7).




upper beach sediment is moderately well sorted, Coarse Skewed and Very Leptokurtic.




well sorted, Near Symmetrical and Mesokurtic


grain size of 0.20 mm. The sample consists of 1.93% Gravel (>2.0 mm), 98% Sand

(0.0625 - 2.0 mm) and 0.07% Mud (<0.0625 mm). The lower beach sediment is well sorted,

Near Symmetrical and Mesokurtic. The gravel components in these sediments are

attributed to shell fragments in the sediment which is predominantly fine grained

(Figure 81).

Figure 81: Sediment grain-size distributions for Mayaro Bay Station 3

During 2004 – 2005, the profile at this station showed much higher sand levels (Figure 82).

From January 2005 to October 2006 there was significant loss in sediment seaward of the

44 m mark from the benchmark. Since then, the beach has remained in dynamic

equilibrium maintaining a fairly constant gentle gradient. The sediment lost from the beach

face usually migrates to an offshore sand bar during the winter months. During the summer

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Mayaro Bay Station 3 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)


Sediment Histogram for Mayaro Station 3

UB

MB

LB



months, the sand stored in this offshore bar gradually returns and re-establishes the

elevation on the beach (Figure 82). However, this was not observed at this station from the

profiles after January 2005. It is possible that the sand may have been transported further

offshore or longshore drift dominated the coastal processes transporting the sediment

further south along the bay.

Figure 82: Selected beach profiles for Mayaro Station 3 (south) for the period 2004 – 2008

4.3 SOUTH COAST

Five bays are monitored along this coastline. These include Guayaguayare, Quinam, Los

Iros, Erin and Punta del Arenal.

Table 10 summarizes the littoral processes occurring on these beaches and bays for this

coastline. Table 11 presents grain size sediment data while Table 12 summarizes the data

on erosion/accretion rates.

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120 124


Ele

va

tio

n (

m)

2004 01 2005 01

2006 10 2007 10

2008 01 2008 06


2004 - 2008 BM





Table 10: Summary Littoral Processes for South Coast Beaches of Trinidad for the period 2004 – 2008

Beach/Bay Station

Location

Wind Speed

Wind Direction


Current Direction

(s) (cm/s)

Mean Range STD Mean RANGE STD Direction Mean Range STD Mean Range STD Mean Range STD

Guayaguayare East 2.99 1.7-5.0 0.78 SE 0.32 0.1-0.5 0.7 SE 0.36 0.15-0.50 0.08 7.7 6.0-12.6 1.32 17.03 7.47-42.0 9.05 SW

Central 2.72 1.0-5.5 1.04 E 0.38 0.2-0.5 0.09 SE 0.43 0.2-0.6 0.12 7.57 6.6-11.5 0.99 15.55 5.8-27.73 6.3 SW

West 3.12 10.0-5.5 1.08 ESE 0.47 0.3-0.6 0.07 SE 0.53 0.35-0.70 0.1 7.4 6.0-11.0 1.01 19.93 1.2-53.7 10.27 SW

Quinam Car Park 2.58 1.5-4.3 0.87 SE 0.5 0.2-0.75 0.16 S 0.51 0.2-0.85 0.18 7.34 6.0-8.8 0.82 22.48 7.93-39.7 11.29 W

Los Iros End of Road 2.73 0.0-6.6 1.86 SE 0.42 0.2-0.8 0.22 S 0.44 0.20-0.70 0.19 7.53 6.7-8.5 0.6 24.29 7.93-49.0 15.48 W

Erin Car Park 2.24 0.5-3.5 1.06 SE 0.35 0.2-0.6 0.13 SW 0.39 0.2-0.55 0.12 7.53 6.1-9.0 0.79 17.95 5.67-10.25 10.25 NW

Punta del Arenal

1 km South of Corral Pt. 2.04 1.3-2.8 0.57 SE 0.37 0.3-0.5 0.07 WNW 0.43 0.3-0.50 0.09 7.9 6.8-9.4 0.98 19.03 6-44.3 12.02 SE



Table 11: Summary grain size for South Coast Beaches of Trinidad


LOCATION



GRAVEL >2.0mm

SAND (0.0625 - 2.0 mm)

MUD < 0.0625mm

Guayaguayare Bay 3 East


SAND


SAND

LB 2.29 0.20 2.39 0.19 0.84 0.56 Moderately

sorted -0.36 2.00 3.20 96.64 0.17


Guayaguayare Bay 2 Central

UB 2.18 0.22 2.24 0.21 0.75 0.59 Moderately

sorted -0.25 1.60 1.35 98.58 0.07


MB 1.90 0.27 2.27 0.21 1.26 0.42 Poorly sorted -0.51 1.42 6.42 93.33 0.25 Gravelly SAND


sorted -0.20 1.72 1.70 98.10 0.20


Guayaguayare Bay 1 West

UB 0.81 0.57 0.81 0.57 0.92 0.53 Moderately

sorted 0.00 1.00 3.53 96.47 0.00



LB 1.66 0.32 1.66 0.32 0.87 0.55 Moderately

sorted -0.09 1.21 1.80 98.18 0.02


Quinam Bay

Car Park

UB 0.10 0.93 0.51 0.70 2.34 0.20 Very poorly

sorted -0.24 0.59 36.46 63.50 0.03 Sandy GRAVEL


SAND

LB 2.34 0.20 2.48 0.18 0.84 0.56 Moderately

sorted -0.42 2.12 2.95 96.98 0.07


Los Iros Bay


SAND


SAND

LB 2.00 0.25 2.28 0.21 1.11 0.46 Poorly sorted -0.50 1.84 4.73 95.17 0.10 Slightly Gravelly

SAND

Erin Bay


SAND


SAND


sorted -0.15 1.50 1.05 98.68 0.27


Punta del Arenal


SAND


SAND

LB 1.27 0.41 1.70 0.31 1.22 0.43 Poorly sorted -0.48 1.02 5.75 94.25 0.00 Gravelly Sand



Table 12: Summary shoreline stability status of South Coast beaches of Trinidad for the period 2004 – 2008

Beach/Bay IMAs Beach

Monitoring

Station Location





2004 2005 2006 2007 2008

Guayaguayare East DE DE DE DE DE


West -0.75 -1.50 -2.20 -0.50 -1.00

Quinam Car Park DE DE DE DE DE

Los Iros End of Los Iros

Bay Road

DE DE DE DE DE

Erin Car Park DE DE DE DE DE

Punta del

Arenal

1km South of

Corral Pt.

N/A 0.16 DE DE DE

Beaches on the south coast are in dynamic equilibrium with the exception of the western

region of Guayaguayare Bay. This area of the bay was the site chosen for the laying of the

gas pipelines where trenching occurred both in the backshore and offshore regions. The

trenching activities increased the wave energy in the bay and this resulted in erosion of the

backshore cliff. At Quinam Bay, the beach is backed by a seawall at IMA’s monitoring

station and erosion was not observed during 2004 – 2008. However, slope failure is

occurring east and west of the benchmark resulting in erosion. The spit at Erin Bay buffers

the wave action from eroding the low backshore cliff. Punta del Arenal is the only bay in the

region that experienced accretion. This bay has been experiencing accretion for more than

a century.



4.3.1 Guayaguayare Bay

Guayaguayare Bay is located on the eastern end of Trinidad’s south coast. At the eastern

section of the bay is a seawall that protects the road that runs parallel to the coast.

Three monitoring stations exist on this bay at the eastern, central and western sections.

The eastern station is located west of the Lizard River, the central station at the

approximate centre of the bay, and the western station just east of the Lawai River.

Figure 83 is an IKONOS (2007) image of Guayaguayare Bay showing the location of the

three IMA stations on this bay.

Figure 83: IKONOS image of Guayaguayare Bay showing Stations location (2007)

3

2

1



Station 1:

The western region of the bay (Station 1) has been the site for the landing of a number of

gas pipelines inclusive of the 56” pipeline leading from Galeota to Atlantic LNG in Pt. Fortin.

Offshore trenching through the reef, horizontal directional drilling and backshore

trenching to accommodate these pipelines have made significant impact on this part of the

coastline (Plate 28).

Plate 28: Beach at Guayaguayare Bay Station 1 showing beach face and coconut tress falling over due to erosion at the base (February 2007)

Wind approaches from the east-southeast with an average speed of 3.12 m/s

(+/-1.08 m/s). Waves at this station approach from the southeast. Mean significant wave

height is 0.47 m (+/-0.07 m) with a period of 7.4 s (+/-1.01 s), while the breaker height

(spilling breaker) is 0.53 m (+/- 0.10 m). Mean longshore current averages 13.93 cm/s

(range 1.2-53.7 cm/s, +/- 10.27 cm/s) and flows southwest (Table 10).




sediment is moderately sorted, Near Symmetrical and Mesokurtic.

The mid-beach sample is classified as Gravelly SAND with a mean grain size of 0.58mm and


Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The sediment is poorly sorted, Coarse

Skewed and Platykurtic.





(0.0625 - 2.0 mm) and 0.02% Mud (<0.0625 mm). The sediment is moderately sorted, Near

Symmetrical and Leptokurtic. The gravel component in these samples is attributed to

sediment from the trenching and backfill activities of the pipe laying works. Overall the

predominant grain size at this station consists of coarse grained sediment (Figure 84).

Figure 84: Sediment grain-size distributions for Guayaguayare Bay Station 1

During 2004 – 2008, landward recession was observed each year (Table 12), with the most

severe in 2006, when 2.20 m of the cliff was eroded; and this coastline continues to erode.

This erosion was a direct result of the pipeline laying activities as well as the changing of

the coastal processes occurring within the bay. The topography to the east of the station is

low coastal plains, but to the west are the high cliffs of Gran Calle Point. The backshore is

vegetated with coconut palms, low shrubs and grasses. The upper region of the beach is

moderately sloping but gradually tapers to a gentle slope in the surf zone (Plate 28). There

are minimal seasonal changes in the elevations of the sediment at this station. Figure 85

shows selected profiles at this station for 2004 - 2008. The profiles indicate distinct

changes at this station since 2004 with regards to sediment volume and cliff recession.

With the exception of 2006, there has been continuous loss of sediment along this beach

area; the lowest elevation observed in June 2008.

Figure 86 shows the maximum and minimum beach elevations of at this station. It is clear

that distinct variation exists, especially in the swash zone, between 6 – 32 m from the

benchmark. Also noticeable is that the average profile closely relates to the minimum

elevation. It is uncertain as to how long it will take for this section of the beach to recover

and re-establish equilibrium status.

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Figure 85: Selected beach profiles for Guayaguayare Bay Station 1 (west) for the period 2004 – 2008

Changes to the beach width between October 1996 and October 2008 reflect the eroding

beach (Figure 87). The sharp decrease in beach width after 3500 days began in 2006 with

additional pipe laying works. This beach continues to erode and made it necessary to have

the benchmark set back further inland on two occasions.

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Guayaguayare Bay Station 3

2004 - 2008

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Figure 86: Maximum - Minimum elevations of Guayaguayare Bay Station 1 (west) for the period 2004 – 2008

Figure 87: Plot of Beach Width vs. Number of days for Guayaguayare Bay Station 1 (west) for the period October 1996 – October 2008

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MAX IMUM

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G UAY AG UAY AR E B AY - S T AT ION 3MAX IMUM AND MINIMUM E L E VAT IONS

2004 - 2008

EL

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D IS T ANC E (m)


y = -0.0024x - 2.7970R² = 0.1832

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GUAYAGUAYARE BAY - Station 1Change in Beach Widths

October 1996 - October 2008

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Station 2:

The central region of the bay (Station 2) is backed by a coastal plain vegetated with coconut

palms, low shrubs and grasses. . The bay is also very gently sloping (Plate 29) and is in

dynamic equilibrium (Table 12).

Plate 29: Guayaguayare Bay Station 2, showing gently sloping beach (July 2007)


(+/-1.04 m/s). Waves approach from the southeast with a mean significant wave height of

0.38 m (+/-0.09 m) and a period of 7.57 s (+/-0.99 s) while the breaker height (spilling


(range 5.8-27.73 cm/s+/- 6.3 cm/s) and flows southwest (Table 10).


Gravelly SAND with a mean grain size of 0.22 mm and median grain size of 0.21 mm. The

sample consists of 1.35% Gravel (>2.0 mm), 98.58% Sand (0.0625 - 2.0 mm) and 0.07%

Mud (<0.0625 mm). The upper beach sediment is moderately sorted, Coarse Skewed and

Very Leptokurtic.

The mid-beach sample is classified as Gravelly SAND with a mean grain size of 0.27 mm and


Sand (0.0625 - 2.0 mm) and 0.25% Mud (<0.0625 mm). The mid-beach sediment is poorly

sorted, Strongly Coarse Skewed and Leptokurtic.




well sorted, Coarse Skewed and Very Leptokurtic (Figure 88).




There are minimal seasonal changes in the elevations of the sediment at this station.

Figure 89 shows selected profiles at this station. Minor erosion is occurring to the east and

west of this station but it is not reflected in the profiles at this station.

Long term trend analysis of the changes to the beach width indicates that over the past 23

years there has been an overall reduction in width (Figure 90). Though not drastic, the

changes were sufficient to have the benchmark set back on at least two occasions during

this time.

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Figure 89: Beach at Guayaguayare Bay Station 2 in the central part of the Bay

Figure 90: Plot of Beach Width vs. Number of days for Guayaguayare Bay Station 2 (central) for the period February 1985 – October 2008

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2004 - 2008

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y = -0.0005x - 2.6509R² = 0.0721

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GUAYAGUAYARE BAY - Station 2Change in Beach Widths


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Station 3:

Station 3 (east) is backed by low cliffs, an outcropping of weakly consolidated sandstone

and a low beach gradient (Plate 30). The beach profiles show a very gently sloping beach

and suggests that it is in dynamic equilibrium (Table 12).

Plate 30: Guayaguayare Bay Station 3, showing gently sloping beach (July 2007)

Wind speed at this station approaches from the southeast with an average speed of

2.99 m/s (+/-0.78 m/s). Waves approach from the southeast with a mean significant wave

height of 0.32 m (+/-0.7 m). Wave period averages 7.7 s (+/-0.1.32 s) while the breaker

height (spilling breaker) is 0.36 m (+/- 0.7 m). Mean longshore current averages

17.03 cm/s (range 7.47-42.0 cm/s, +/- 9.05 cm/s) and flows southwest (Table 10).


Gravelly SAND with a mean and median grain size of 0.18mm. The sample consists of 0.3%


upper beach sediment is moderately well sorted, Near Symmetrical and Mesokurtic.




well sorted, Coarse Skewed and Very Leptokurtic.






is moderately sorted, Strongly Coarse Skewed and Very Leptokurtic (Figure 91).


There is seasonal fluctuation in the elevations of the sediment but equilibrium is attained

(Figure 92). The profile is influenced by the discharge of the Lizard River and the near

shore sediment is predominantly mud deposited by the river.

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Figure 92: Selected beach profiles for Guayaguayare Bay Station 3 (east) for the period 2004 – 2008

4.3.2 Quinam Bay

Quinam Bay is located on the western side of the southern coastline. The bay is 1.6 km long

and has a gentle slope. A wide beach is exposed during low tide conditions. The cliff at the

eastern headland is steeply sloping, densely vegetated and eroding due to undercutting at

the base. Figure 93 is an IKONOS (2007) image of Quinam Bay showing the location of the

IMA station on this bay. The beach at this station however experienced dynamic

equilibrium during the reporting period (Table 12).

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2004 - 2008

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Figure 93: IKONOS image of Quinam Bay showing Station location (2007)

The bay had it highest elevation in October 2004 and lowest in May 2005 (Figure 95). Since

then the bay has been in dynamic equilibrium with accretion occurring on the upper beach

in April 2008 (Figure 95). The backshore cliff in the immediate vicinity of the IMA’s

benchmark is stable and has not experienced any recession, but the cliffs to the west are

experiencing erosion (Plate 31).



Plate 31: Westerly view of beach at Quinam Bay showing eroding cliffs west of car park (February 2008)

Wind approaches from the southeast with an average speed of 2.58 m/s (+/-0.87 m/s).

Waves at this bay approach from the south. Mean significant wave height is 0.5 m

(+/-0.16 m) with a period of 7.34 s (+/-0.82 s), while the breaker height (spilling breaker)

is 0.51 m (+/- 0.18 m). Mean longshore current averages 22.48 cm/s

(range 7.93-39.7 cm/s, +/- 11.29 cm/s) and flows west (Table 10).

From Table 11 it is shown that the upper beach sediment sample is classified as Sandy

GRAVEL with a mean grain size of 0.93 mm and median grain size of 0.70mm. The sample

consists of 36.46% Gravel (>2.0 mm), 63.5% Sand (0.0625 - 2.0 mm) and 0.03% Mud

(<0.0625 mm). The upper beach sediment is Very poorly sorted, Coarse Skewed and Very

Platykurtic.


size of 0.15 mm. The sample consists of 1% Gravel (>2.0 mm), 98.95% Sand


well sorted, Coarse Skewed and Very Leptokurtic.






is moderately sorted, Strongly Coarse Skewed and Very Leptokurtic. The high gravel

component in the upper beach sample originates from the eroding cliffs to the east and

west of the benchmark (Figure 94).

Figure 94: Sediment grain-size distributions for Quinam Bay

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Sediment Histogram for Quinam

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Figure 95: Selected beach profiles for Quinam Bay for the period 2004 – 2008

4.3.3 Los Iros Bay

Los Iros is located on the southern coast of Trinidad between Erin and Taparo Points. The

bay is approximately 2 km long and the low cliff comprised of mud flow deposits.

Significant erosion occurred on this beach during 1957 – 1971 which resulted in the

construction of a series of groins in 1975 to remediate the problem and to preserve the

recreational importance of this bay (Bachew et al, 1983). Shoreline retreat still continued

due to the ineffectiveness of the groins and today only remnants of the engineering

structure remain visible. Detached breakwaters were suggested to combat the erosion but

were never constructed. Figure 96 is an IKONOS (2007) image of Los Iros Bay showing the

location of the IMA station on this bay. The beach has a gentle gradient and fairly wide

during low tide conditions (Plate 32).

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Quinam Bay

2004 - 2008

BM





Figure 96: IKONOS image of Los Iros Bay showing Station location (2007)

Plate 32: Easterly view of beach at Los Iros Bay showing wide gently sloping beach (October 2007)



Littoral data collected indicates that wind approaches from the southeast with an average

speed of 2.73 m/s (+/-1.86 m/s). Waves in this bay approach from the south. Mean

significant wave height is 0.42 m (+/-0.22 m) with a period of 7.53 s (+/-0.6 s), while the

breaker height (spilling breaker) is 4.4 m (+/- 0.19 m). Mean longshore current averages

24.29 cm/s (range 7.93-49.0 cm/s, +/- 15.48 cm/s) and flows to the west (Table 10).




The upper beach sediment is Very well sorted, Near Symmetrical and Very Platykurtic.



(0.0625 - 2.0 mm) and 0.1% Mud (<0.0625 mm). The mid-beach sediment is well sorted,




(>2.0 mm), 95.17% Sand (0.0625 - 2.0 mm) and 0.1% Mud (<0.0625 mm). The lower beach

sediment is poorly sorted, Strongly Coarse Skewed and Very Leptokurtic. The sediment at

this beach is predominantly fine grained (Figure 97).

Figure 97: Sediment grain-size distributions for Los Iros Bay

Erosion is occurring at the eastern end and the western parts of the bay, but at IMA’s

benchmark station, the beach is in dynamic equilibrium (Table 12). Figure 98 shows the

selected profiles during 2004 – 2008. The profile in April 2008 represents the highest

elevation during the survey period.

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Figure 98: Selected beach profiles for Los Iros Bay for the period 2004 – 2008

4.3.4 Erin Bay

Erin Bay extends from Punta Blanca in the east to Islote Point in the west. The eastern part

of the bay consists of sandstone while the central to western limits consist of high cliffs.

Porcellanite sediments (gravel and cobbles) are seen on the beach toward the central part

of the bay. Figure 99 is an IKONOS (2007) image of Los Iros Bay showing the location of the

IMA station on this bay. The Erin River exits in the eastern end forming the Erin spit (Plate

33), which trends in an east – west direction.

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Los Iros Bay

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Figure 99: IKONOS image of Erin Bay showing Station location (2007)

Plate 33: Westerly view of beach at Erin Bay showing sand spit (February 2007)



Littoral data collected during 2004 – 2008 indicates that the wind approaches from the

southeast with an average speed of 2.24 m/s (+/-1.06 m/s). Waves in this bay approach

from the southwest with a mean significant wave height of 0.35m (+/-0.13 m). Wave period

averages 7.53 s (+/-0.79 s) while the breaker height (plunging breaker) is 0.39 m


+/- 10.25 cm/s) and flows predominantly northwest (Table 10).








well sorted, Near Symmetrical and Leptokurtic.




well sorted, Coarse Skewed and Leptokurtic (Figure 100).

Figure 100: Sediment grain-size distributions for Erin Bay

During the reporting period the bay exhibited dynamic equilibrium (Table 12). Selected

profiles for Erin bay indicate the beach is in dynamic equilibrium (Figure 101). The spit is

more pronounced in the profile of February 2004. Seaward of the spit the beach has a

gentle gradient. The spit is very dynamic and changes seasonally. Although there have been

changes in beach elevations, no shoreline retreat has been observed during 2004 – 2008.

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Figure 101: Selected beach profiles for Erin Bay for the period 2004 – 2008

4.3.5 Punta Del Arenal

Punta del Arenal is located on the south western tip of Trinidad. It is the only bay in

Trinidad that is accreting. This part of the coastline is oriented in a north-south trend and

influenced by the flow of the Orinoco River within the Serpent’s mouth. Figure 102 is an

IKONOS (2007) image of Punta del Arenal showing the location of the IMA station on this

bay. The bay is backed by recent alluvium and vegetated with coconut palms and low

shrubs. The backshore is of low topography with a gentle gradient beach (Plate 34).

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Erin Bay

2004 - 2008

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Figure 102: IKONOS image of Punta del Arenal showing Station location (2007)

Plate 34: Punta del Arenal showing vegetation and wide gently sloping beach (February 2006)



Littoral data indicate that the wind approaches from the southeast with an average speed

of 2.04 m/s (+/-0.57 m/s). Mean significant wave height is 0.37 m (+/-0.07 m) with a

period of 7.9 s (+/-0.98 s), while the breaker height (spilling breaker) is 0.43 m

(+/- 0.09 m) approaching from the west-northwest. Mean longshore current averages

19.03 cm/s (range 6.0-44.3 cm/s, +/- 12.02 cm/s) and flows to the south (Table 10).


Gravelly SAND with a mean and median grain size of 0.16mm. The sample consists of

0.12% Gravel (>2.0mm), 99.78% Sand (0.0625 - 2.0mm) and 0.10% Mud (<0.0625mm).



size of 0.19mm. The sample consists of 0.20% Gravel (>2.0mm), 99.65% Sand (0.0625 -

2.0mm) and 0.15% Mud (<0.0625mm). The mid-beach sediment is moderately well sorted,


The lower beach sample is classified as Gravelly Sand with a mean grain size of 0.41mm

and median grain size of 0.31mm. The sample consists of 5.75% Gravel (>2.0mm), 94.25%

Sand (0.0625 - 2.0mm) and 0% Mud (<0.0625mm). The lower beach sediment is poorly

sorted, Strongly Coarse Skewed and Mesokurtic (Figure 103).

Figure 103: Sediment grain-size distributions for Punta del Arenal

Figure 104 shows selected profiles for this station. At 12 m from the benchmark, there has

been approximately 0.50 m increase in sediment levels from 2004 to 2008, building up the

berm. The rest of the beach remains in dynamic equilibrium (Table 12).

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Figure 104: Selected beach profiles for Punta del Arenal for the period 2004 – 2008

4.4 WEST COAST

The west coast of Trinidad is varied in its coastal classification. The southern cliffs are more

easily eroded due to their composition. The beaches along this coastline are gently sloping

and exposed to moderate wave energy. The murky waters along this coastline are

indicative of the high sediment discharge from the rivers of the South American mainland,

particularly the Orinoco, as well as the local rivers that drain into the Gulf of Paria.

Table 13 summarizes the littoral processes occurring along the selected beaches and bays

for this coastline for the period 2004 – 2008. Table 14 presents the sediment grain size

parameters. Table 15 presents the rate of erosion/accretion or state of dynamic

equilibrium for the selected bays on this coastline.

Erosion is occurring at a phenomenal rate at Corral Point and the north eastern section of

Columbus Bay. The central section of Columbus Bay however is stable and erosion was not

observed during 2004 – 2008. At Granville Bay, erosion was not observed at the IMA’s

monitoring station, but it was observed at the eastern and western regions of the bay. All

other beaches along this coastline are in dynamic equilibrium with the exception of North

Chatham. The beach here has a low gradient and an erodible backshore clayey cliff. The cliff

experiences undercutting at the base, which eventually slump over resulting in erosion. At

Guapo Bay, the beach at Clifton Hill is protected by a rip rap revetment, seawall and an

offshore breakwater. Erosion was not observed at IMA’s stations along this coastline.

Beachwidth trends are highlighted for stations at Guapo Bay, Station Beach (La Brea) and

Chagville Bay.

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2004 05

2007 10

2008 01

2008 04

Punta del Arenal

BM



Table 13: Summary Littoral Processes for West Coast beaches of Trinidad and Tobago for the period 2004 – 2008

Beach/Bay Station

Location

Wind Speed

Wind Direction


Current Direction

(s) (cm/s)

Mean Range STD Mean Range STD Direction Mean Range STD Mean Range STD Mean Range STD

Columbus Bay Central 1 0.0-2.1 0.83 NE 0.36 0.3-0.5 0.08 NW 0.41 0.30-0.65 0.13 7.8 6.9-8.6 0.62 8.04 2.3-19.2 5.59 SW

Granville End of Access Road to Bay 1.53 0.0-2.3 0.9 E 0.28 0.2-0.35 0.05 WNW 0.33 0.25-0.40 0.07 6.8 50.7.8 1.08 9.3 4.7-16.3 3.81 W

Irois Chinkit Trace 1.68 10-2.2 0.47 SE 0.21 0.05-0.3 0.06 SW 0.24 0.05-0.4 0.09 6.8 5.3-7.8 0.81 9.1 3.0-20 4.89 SW

North Chatham 1.79 0.3-5.0 1.03 E 0.26 0.4-0.1 0.08 S 0.3 0.15-0.5 0.08 7.04 5.10-9.10 0.88 12.11 5.80-32.67 6.07 W

Guapo Vessigny 1.9 0.0-4.20 1.18 SE 0.1 0.05-0.15 0.04 NW 0.12 0.05-0.2 0.05 7.6 5.5-9.4 1.16 5.9 1.07-21.0 5.85 SE

West of Guapo River 2.07 1.3-2.9 0.53 E 0.19 0.1-0.3 0.07 SE 0.24 0.15-0.45 0.11 7.49 6-8.4 0.78 12.2 4.67-19.83 4.5 SW

CH1 2.14 0.0-4.0 1.21 NE 0.22 0.1-0.4 0.08 NE 0.24 0.1-0.4 0.08 7.42 5.0-10.30 1.52 12.26 3.5-19.20 4.43 W

BG Pipeline 2.42 1.5-4.0 0.81 NE 0.22 0.1-0.35 0.08 SE 0.25 0.1-0.35 0.08 7.55 6.0-9.1 0.86 12.1 4.27-18.67 3.77 W

5 2.16 0.0-5.0 1.4 E 0.19 0.05-0.35 0.08 SW 0.21 0.05-0.40 0.09 7.65 5.0-9.2 1.16 14.79 3.4-29.17 6.66 W

5A 2.7 1.5-3.7 0.8 E 0.2 0.2-0.4 0.1 SE 0.3 0.2-0.4 0.1 6.3 0.0-8.5 2.7 15 0.0-23.3 7.3 SW

La Brea (Station Beach) STN 2-Carpark 2.56 0.8-4.0 0.97 E 0.23 0.15-0.7 0.12 SW 0.25 0.15-0.7 0.12 7.2 4.0-8.9 1.18 13.07 21.3-28.0 6.3 W

STN 3 2.53 0.5-4.1 1.02 E 0.23 0.15-0.7 0.11 SW 0.25 0.15-0.70 0.11 7.5 4.5-10.7 1.49 14.29 4.3-32.7 7.39 SW

Dhein’s Bay Central 2.67 2.3-3.0 0.29 SE 0.2 0.1-0.3 0.08 S 0.27 0.05-0.25 0.18 7.07 5.3-8.3 1.28 8.27 7.47-9.33 0.79 W

Chagville 1-West 1.48 0.7-2.1 0.53 SE 0.15 0.05-0.35 0.11 SE 0.2 0.05-0.45 0.14 7.36 7.0-8.3 0.48 6.83 0-12.8 4.61 WSW

3-Central 3.1 1.3-4.5 1.21 ESE 0.22 0.1-0.3 0.07 SSE 0.27 0.1-0.4 0.11 6.98 5.0-8.0 1.07 8.83 3.20-17.50 4.89 SW



Table 14: Summary grain size for West Coast Beaches of Trinidad


LOCATION

GRAPHIC MEAN MEDIAN SORTING

SKEWNESS KURTOSIS


GRAVEL >2.0mm

SAND (0.0625 - 2.0 mm)

MUD < 0.0625mm

Columbus Bay 7 IMA's

Original BM


SAND


SAND


SAND

Granville Bay


SAND


sorted -0.13 1.94 1.49 98.35 0.17



Irois Bay 9a Point Ligoure

Seawall

UB 1.90 0.27 1.90 0.27 0.43 0.74 Well sorted 0.00 1.00 0.05 99.92 0.03 Slightly Gravely

SAND


SAND


sorted -0.09 1.39 1.22 98.08 0.70


Irois Bay 1b Chinkit Trace

(River)

UB 2.23 0.21 2.06 0.24 0.78 0.58 Moderately

sorted 0.11 2.02 1.85 98.15 0.00


MB 2.18 0.22 2.18 0.22 0.46 0.73 Well sorted 0.00 1.00 0.80 99.20 0.00 Slightly Gravely

SAND

LB 2.26 0.21 2.26 0.21 0.42 0.75 Well sorted 0.00 1.00 0.77 99.23 0.00 Slightly Gravely

SAND

La Brea 2 Car Park


SAND

MB 2.28 0.21 2.28 0.21 0.33 0.80 Very well sorted 0.00 1.00 0.00 99.98 0.02 SAND


La Brea 3 Seawall


SAND


SAND


SAND

Guapo Bay 1 Vessigny


SAND


SAND


SAND



Table 14: Summary grain size for West Coast Beaches of Trinidad Cont’d.


LOCATION

GRAPHIC MEAN MEDIAN SORTING

SKEWNESS KURTOSIS


GRAVEL >2.0mm

SAND (0.0625 - 2.0 mm)

MUD < 0.0625mm

Guapo Bay 4a West


SAND


SAND


SAND

Guapo Bay CH 1

UB 2.57 0.17 2.57 0.17 0.44 0.74 Well sorted 0.00 1.00 0.00 99.93 0.07 SAND


SAND


SAND

Guapo Bay 4b Pipeline

UB 2.37 0.19 2.37 0.19 0.80 0.57 Moderately

sorted -0.27 2.26 4.66 95.28 0.05

Slightly Gravely SAND


SAND

LB 2.40 0.19 2.43 0.19 0.72 0.61 Moderately

sorted -0.29 2.02 2.96 96.99 0.05


Guapo Bay 5 Old Golf Course


SAND


SAND


SAND

Dhein's Bay


sorted -0.18 1.57 1.17 98.65 0.18



LB -1.04 2.05 -

1.70 3.25 2.38 0.19

Very poorly sorted

0.32 0.56 56.29 43.68 0.03 Gravelly SAND

Chagville Beach

1 West


sorted

-0.06 1.18 1.36 98.62 0.02 Slightly Gravelly

SAND MB -0.22 1.16 0.22 0.86 2.08 0.24 Very poorly

sorted

-0.25 0.72 35.38 64.54 0.08 Sandy GRAVEL


SAND

Chagville Beach

3 Central


SAND MB 0.72 0.61 1.31 0.40 1.74 0.30 Poorly sorted -0.43 0.81 20.46 79.41 0.13 Slightly Gravelly

SAND LB 2.76 0.15 2.76 0.15 0.47 0.72 Well sorted -0.01 1.01 0.00 98.87 1.13 Gravelly SAND



Table 15: Shoreline stability of West Coast beaches of Trinidad for the period 2004 – 2008

Beach/Bay IMAs Beach Monitoring Station Location


(+Net Annual Accretion (m); -Net Annual Erosion (m);


2004 2005 2006 2007 2008

Columbus Bay


Granville End of Access Road to Bay

DE DE DE DE DE

Irois Chinkit Trace Revetment

North Chatham -0.65 -0.75 -0.20 -1.70 -1.50

Guapo 1 - Vessigny DE DE DE DE DE

4A - West of Guapo River

DE DE DE DE DE

CH1 DE DE DE DE DE

4B BG Pipeline DE DE DE DE DE

5 DE DE -0.64 -0.71 DE

5A DE DE DE -2.95 Construction

La Brea (Station Beach)

Carpark DE DE DE DE DE

Seawall DE DE DE DE DE

Dhein’s Bay Central DE DE DE DE DE

Chagville West DE DE DE DE DE




4.4.1 Columbus Bay

Columbus bay is a 4 km stretch of beach oriented in a NE – SW trend. It is bounded by Los

Gallos and Corral Points in the northeast and southwest respectively. Figure 105 is an

IKONOS (2007) image of Columbus Bay showing the location of the IMA station on this bay.

The station is located in the approximate central part of the bay. The bay is backed by the

coconut plantation and has a wide fairly gently sloping beach (Plate 35).

Figure 105: IKONOS image of Columbus Bay showing Station location (2007)



Plate 35: Southerly view of Columbus Bay (February 2007)

Littoral data collected indicates that wind approaches from the south east with speeds

averaging 1.0 m/s (+/- 0.83 m/s). Waves approach from the northwest with a mean

significant wave height of 0.36 m (+/- 0.08 m), a period of 7.8 s (+/- 0.62 s) and a breaker

height (plunging breaker) of 0.4 m (+/- 0.13 m). Mean longshore current averages

8.04 cm/s (range 2.3 – 19.2 cm/s, +/- 5.59 cm/s) flowing predominantly in a southwesterly

direction (Table 13).


Gravelly SAND with a mean and median grain size of 0.24 mm. The sample consists of 0.7%


sediment is Very well sorted, Near Symmetrical and Mesokurtic.



(0.0625 - 2.0 mm) and 0.05% Mud (<0.0625 mm). The sediment is Very well sorted, Near





is Very well sorted, Fine Skewed and Leptokurtic. The sediment at this beach is

predominantly fine grained (Figure 106).



Figure 106: Sediment grain-size distributions for Columbus Bay Station 7

Selected profiles indicate that this section the bay is in dynamic equilibrium (Figure 107).

During 2004 – 2008 there has not been any significant retreat in the shoreline, but the bay

continues to lose sediment along beach face. The loss of sediment along the beach face has

not been sufficiently extensive to cause erosion on the backshore by wave uprush.

However, the length of this beach coupled with the depth of sediment removed results in a

voluminous amount of sediment being removed. This volume of sediment eroded however

is not reflected in accretion down drift of the bay since Corral Point is eroding severely.

Erosion rates are not available for Corral Point but visible signs are present to indicate its

severity. Such indicators include shoreline recession, fallen trees and destruction of coastal

residential properties.

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Columbus Bay Station 7 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Pre

cen

tage

(%

)

Sediment size(Phi)

Sediment Histogram for Columbus Station 7

UB

MB

LB



Figure 107: Selected beach profiles for Columbus Bay for the period 2004 – 2008

Further studies need to be conducted to determine where this sediment is being

transported and finally deposited. The maximum and minimum elevations of this bay

(Figure 108) were not as prolific as the accretion taking place at Punta del Arenal. The

swash zone clearly experiences changes in beach volume up to 40 m from the benchmark.

The beach face undergoes changes however, not being tied into MSL limits the analysis of

the beach width trends. Currently, studies are being drafted to undertake extensive

research into the hydrological and oceanographic conditions of this bay and to possibly

suggest methods for reducing or alleviating the erosion occurring at this bay.

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100


Ele

va

tio

n (

m)

2004 02 2004 05

2007 02 2007 10

2008 01 2008 04

2008 09

Columbus Bay

2004 - 2008

BM





Figure 108: Maximum - Minimum elevations of Columbus Bay for the period 2004 – 2008

4.4.2 Granville Bay

Granville bay is located between Cedros Point in the west to Punta del Morro in the east.

Figure 109 is an IKONOS (2007) image of Granville Bay showing the location of the IMA

station on this bay. The low cliffs that back this region of the bay are stable, but there is

undercutting at the base of the cliffs. Eventually, slumping will occur and a recession of this

cliff will be observed. However, recession of this cliff was not observed during the

reporting period. A storm drain is located immediately east of the profile which can easily

contribute to sediment removal during heavy rainfall and peak discharge. The beach is

fairly wide with a very gentle gradient and backed by a fenced private property (Plate 36).

3

4

5

6

7

8

9

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84

MAXIMUM

MINIMUM

AVE R AGE


C OL UMB US B AY

2004 - 2008E

LE

VA

TIO

N (

m)

D IS T ANC E (m)



Figure 109: IKONOS image of Granville Bay showing Station location (2007)

Plate 36: Granville Bay showing gently sloping beach and backshore cliff (January 2008)




Waves in this bay approach from the north-northwest. Mean significant wave height is

0.28 m (+/-0.05 m) with a period of 6.8 s (+/-1.08 s) while the breaker height (spilling


(range 4.7- 16.3 cm/s, +/- 3.81cm/s) and flows west-southwest (Table 13).




The upper beach sediment is Very well sorted, Near Symmetrical and Leptokurtic.




sediment is moderately well sorted, Coarse Skewed and Very Leptokurtic.




sorted, Strongly Coarse Skewed and Very Platykurtic. The sediment at this beach is

predominantly fine grained with coarser grains at the lower beach (Figure 110).

Figure 110: Sediment grain-size distributions for Granville Bay

Selected profiles indicate that this section of the bay is in dynamic equilibrium (Table 15).

The beach profiles reflect the stable backshore cliff and upper beach with the gentle slope

with a near shore zone that is almost flat (Figure 111). Minor changes in beach elevations

are observed for this region of the bay.

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Granville Bay Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Pre

cen

tage

(%

)

Sediment size(Phi)

Sediment Histogram for Granville Bay

UB

MB

LB



Figure 111: Selected beach profiles for Granville Bay for the period 2004 – 2008

4.4.3 Irois Bay

Irois Bay is 10 km long and extends from Point Ligoure in the east to Point Rouge in the

west. The Cap de Ville River exits at the eastern region of the bay. Figure 112 is an IKONOS

(2007) image of Irois Bay showing the location of the two IMA stations on this bay. The bay

has a low gradient and is backed by low to moderate cliffs that are composed of weakly

resistant clays and mudstones, similar to Granville Bay. The cliffs are being undermined at

the base by wave attack. They are slumping by becoming water saturated and losing

cohesion and therefore eroding. At the central to western cliff regions of the bay, this

occurrence is most prominent. The exposed cliffs are further reduced due to sub-aerial

processes. The eastern section of the bay has undergone severe erosion during and after

the construction of the Atlantic LNG Plant. This erosion is continuing even up to present

day. This erosion is not reflected in IMA’s monitoring station but evident from field

observations. The smaller eastern bays within this larger bay such as Hollywood and

Sunset beaches were completely filled in with silt from the dredging and reclamation

activities from LNG Plant. Further west at Cap de Ville, significant erosion is observed

immediately east of the river. At North Chatham, a monitoring station was established to

serve as a control station for the LNG Plant activities.

5.0

6.0

7.0

8.0

9.0

10.0

11.0

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 128 136 144 152 160


Ele

va

tio

n (

m)

2004 02 2004 05

2007 10 2008 01

2008 04 2008 09

Granville Bay

2004 - 2008

BM

The Profile at this station is not

tied in to the National Vertical




Figure 112: IKONOS image of Irois Bay showing Station location (2007)

Cap De Ville – Station 1b

This station is located immediately east of the Cap de Ville River mouth (Plate 37). After the

construction of the Atlantic LNG Plant, elevated rates of erosion and threat to the private

property at this station resulted in the construction of a rubble structure in the latter part

of 2004. Erosion was retarded at this station but increased to the east of the benchmark.

One of IMA’s monitoring stations located in this region was lost due to erosion. Sediment

brought down by the river is deposited in the near shore zone resulting in a very gentle

gradient composed of very fine silts.

1b

10



Plate 37: Easterly view of Irois Bay Station 1b at Cap de Ville showing rubble in the backshore as coastal protection (July 2007)

The wind approaches from the northeast with an average speed of 1.68 m/s (+/-0.47 m/s).

Waves at this station approach from the north. Mean significant wave height is 0.21 m

(+/-0.06m) with a period of 6.8 s (+/-0.81s), while the breaker height (spilling breaker) is

0.24 m (+/- 0.09 m). Mean longshore current averages 9.1 cm/s (range 3.0-20.0 cm/s,

+/- 4.89cm/s) and flows predominantly to the west (Table 13).


Gravelly SAND with a mean grain size of 0.21 mm and median grain size of 0.24 mm. The

sample consists of 1.85% Gravel (>2.0 mm), 98.15% Sand (0.0625 - 2.0 mm) and 0.0% Mud

(<0.0625 mm). The sediment is moderately sorted, Fine Skewed and Very Leptokurtic.

The mid-beach sample is classified as Slightly Gravely SAND with a mean and median grain




The lower beach sample is classified as Slightly Gravely SAND with a mean and median



Symmetrical and Mesokurtic. Fine grained sediment is predominant along the transect line

at this station (Figure 113).



Figure 113: Sediment grain-size distributions for Irois Bay Station 1b

The changing course of the river often results in channelization at the base of the rubble

structure, and often a sand bar is observed. A small mangrove system east of this station

has also succumbed to the forces of erosion. Since the construction of the rubble seawall in

2004, there has been no further shoreline retreat in the vicinity of the benchmark. The

profile plot (Figure 114) shows the eroding beach and the gentle sloping nearshore. The

area is now in dynamic equilibrium (Table 13) and significantly influenced by the river

outflow and flooding events. Erosion is however taking place to the east and west of this

monitoring station.

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Irois Bay station 1b Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Pre

cen

tage

(%

)

Sediment size(Phi)

Sediment Histogram for Irois Bay Station 1b

UB

MB

LB



Figure 114: Selected beach profiles for Irois Bay (Cap de Ville) for the period 2004 – 2008

North Chatham – Station 10

This station was established as a control station for the monitoring plan for the Atlantic

LNG Project. It was assumed that the erosion would not have extended this far west as a

result of the plant’s construction. However, signs of erosion eventually became obvious and

since October 1996 the bay has been eroding. On two occasions, the IMA’s benchmark had

to be set back further inland due to erosion of the cliffs that backs the bay. Between

October 1996 and January 2003 the bay was eroding at an average rate of 1.2 m/yr. At

IMA’s benchmark cliff recession has been occurring every year during 2004 – 2008

(Table 8) and the average erosion rate is 0.96 m/yr. The area is backed by low to moderate

high cliffs that are eroding (Plate 38). The clayey composition of the cliffs makes it

susceptible to weathering and water saturation which results in slope failure and erosion.

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 128 136 144 152 160 168 176 184 192 200 208


Ele

va

tio

n (

m)

2004 03 2004 07

2005 01 2005 05

2008 01 2008 06

2008 07

Irois Bay - Station 1b

2004 - 2008 BM





Plate 38: Westerly view of Irois Bay Station 10 at North Chatham showing wide berm and eroding backshore cliffs, inset shows close up of eroding cliffs. (July 2007)


Mean significant wave height is 0.26 m (+/-0.08 m) with a period of 7.04 s (+/-0.88 s),

while the breaker height (spilling breaker) is 0.3 m (+/- 0.08 m) approaching from the

north. Mean longshore current averages 12.11 cm/s (range 5.80- 32.67 cm/s,

+/- 6.07 cm/s) and flows west (Table 13).

Selected profiles of this station indicate that this beach is eroding (Figure 115). The beach

maintains a low gradient and undercutting at the base of the cliff leads to slumping and

shoreline retreat. For this period approximately 5.0 m of cliff recession was observed

(Table 15). Changes in the dynamics of this beach may be as a result of changing coastal

processes due to offshore works, reclamation or the dredging of the turning basin at the

Atlantic LNG plant.



Figure 115: Selected beach profiles for Irois Bay (North Chatham) for the period 2004 – 2008

4.4.4 Guapo Bay

Guapo Bay extends from Point Rouge in the east to Point Fortin in the west and is

approximately 6 km long. The central section of the bay is backed by sandstone cliffs with

heights of up to 7 m. Two rivers flow into this bay, the Vessigny River on the eastern end

and the Guapo River on the eastern boundary of Guapo Beach. Figure 116 is an IKONOS

(2007) image of Guapo Bay showing the location of the IMA station on this bay.

The construction of the Atlantic LNG plant impacted significantly on this beach resulting in

erosion at Guapo and Clifton Hill beaches. Subsequent to the construction, pipe laying

works in the backshore from the 56” Cross Island Pipeline Project and the 36” British Gas

Pipeline from the North Coast added further stresses to the beach environment resulting in

erosion.

At Clifton Hill, with the onset of the erosion, various methods were employed to retard the

recession. Initially, octagonal concrete piles were aligned along the coastline. When these

failed, concrete blocks held in place by plastic pegs were used to create a moderately

sloping lattice seawall which extended for the entire length of Clifton Hill Beach. This began

failing from dislodgment of the holding pins and blocks, subsidence and scouring.

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120


Ele

va

tio

n (

m)

2004 03 2004 07

2005 01 2005 05

2006 03 2006 10

2007 10

Irois Bay - Station 10

2004 - 2008 BM

The Profile at this station is not

tied in to the National Vertical




After the storm surge of hurricane Lenny in November 1999, huge sections of the wall were

damaged and displaced. To protect the backshore pipeline, a more suited effective method

was needed and eventually a rip rap revetment was constructed to replace the lattice

structure. This wall now extends well east of Clifton Hill. A detached offshore breakwater is

also located aligned with the eastern terminal end of the seawall. This study period reports

on (5) stations monitored by the IMA.

Figure 116: IKONOS image of Guapo Bay showing IMA Stations locations (2007)

Station 1:

At Guapo Bay Station 1, Vessigny beach is very dynamic and experiences distinct changes to

the berm while maintaining an extremely low gradient nearshore (Figure 118). The

gradient of the beach slope is gentle which then flattens in the near shore zone (Plate 39).

These changes can be as a result of the influence of the Vessigny River and the longshore

currents which exist within the bay.

4

3a

1

CH1 4b 5a 5

4a



Plate 39: Station 1 Guapo Bay showing low gradient beach and low wave energy environment (July 2008)

Wind approaches from the east to southeast with an average speed of 1.9 m/s

(+/-1.18 m/s). Waves at this beach approach from the northwest. Mean significant wave

height is 0.1 m (+/-0.04 m) with a period of 7.6 s (+/-1.16 s), while the breaker height

(spilling breaker) is 0.12 m (+/- 0.05 m). Mean longshore current averages 5.9 cm/s (range

1.07-21.0 cm/s, +/- 5.85 cm/s), and flows southeast (Table 13).




The upper beach sediment is well sorted, Near Symmetrical and Very Platykurtic.

The mid-beach sample is classified as Slightly Gravelly SAND with a mean median grain size

of 0.18 mm. The sample consists of 0.03% Gravel (>2.0 mm), 99.88% Sand

(0.0625 - 2.0 mm) and 0.08% Mud (<0.0625 mm). The mid-beach sediment is Very well




(0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The lower beach sediment is well sorted,

Near Symmetrical and Mesokurtic. The sediment at this station is predominantly fine

grained along the transect line (Figure 117).



Figure 117: Sediment grain-size distributions for Guapo Bay Station 1

Figure 118: Selected beach profiles for Guapo Bay (Station 1) for the period 2004 – 2008

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Guapo Bay Station 1 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

Per

cen

tage

(%

)


Sediment Histogram for Guapo Station 1

UB

MB

LB

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 128 136 144 152 160


Ele

va

tio

n (

m)

2004 01 2004 10

2005 01 2005 10

2006 01 2007 08

2008 09

Guapo Bay - Station 1

2004 - 2008 BM



Station 4a:

The Station west of Guapo River (Station 4a) was in dynamic equilibrium from 2004 – 2008

(Table 15). This region of the beach has an extensive low topography backshore and wide

low gradient beach (Plate 40).

Plate 40: Station 4a Guapo Bay showing low topography of backshore and gently sloping beach (July 2008)

Wind approaches from the east-southeast with an average speed of 2.07 m/s (+/-0.53m/s).



north-northeast. Mean longshore current averages 12.2 cm/s (range 4.67-19.83cm/s,

+/- 4.5 cm/s) and flows predominantly in a westerly direction (Table 13).




The upper beach sediment is well sorted, Near Symmetrical and Leptokurtic.




sediment is well sorted, Fine Skewed and Leptokurtic.






Near Symmetrical and Mesokurtic. The sediment at this region of the beach is

predominantly fine sand (Figure 119).

Figure 119: Sediment grain-size distributions for Guapo Bay Station 4A

During the Cross Island Pipeline Project, the benchmark at this station was destroyed on

two occasions and new ones had to be re-established. The dynamics of the berm at this

station and the distinct changes occurring are shown in Figure 120. Recession of the

backshore cliff was not observed but there were sediment losses during 2005 – 2007 along

the beach face. The lowest elevation was observed in February 2007, but by January 2008,

the beach recovered from the sediment losses. These changes can be as a result of the

influence of the Guapo River depositing sediment within the region or from cross-shore

movement of the sediment.

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Guapo Bay Station 4a Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4P

erce

nta

ge (

%)


Sediment Histogram for Guapo Station 4a

UB

MB

LB



Figure 120: Selected beach profiles for Guapo Bay (Station 4a) for the period 2004 – 2008

Station CH1:

Station CH1 lies approximately 150 m east of Station 4b and was determined to be in

dynamic equilibrium during 2004 – 2008 (Table 15). Seasonal variation is exhibited at this

station and although the beach is observed to be the lowest in July 2008, it is anticipated

that there will be recovery in subsequent months. The beach is backed by a low gradient

backshore and moderately sloping vegetated cliff (Plate 41).

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Guapo Bay - Station 4a

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Plate 41: Station CH 1 at Guapo Bay showing gently sloping beach (February 2007)


(+/-1.21 m/s). Waves at this station approach from the north-northeast. Mean significant

wave height is 0.22 m (+/-0.08 m) with a period of 7.426 s (+/-1.52 s), while the breaker


13.26 cm/s (range 3.5-19.20 cm/s, +/- 4.43 cm/s) and flows west (Table 13).

From Table 14 it is shown that the upper beach sediment sample is classified as SAND with

a mean and median grain size of 0.17 mm. The sample consists of 0% Gravel (>2.0 mm),

99.93% Sand (0.0625 - 2.0 mm) and 0.07% Mud (<0.0625 mm). The sediment is well




2.0 mm) and 0.0% Mud (<0.0625 mm). The sediment is Well sorted, Near Symmetrical and

Mesokurtic.



(0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The sediment is Well sorted, Near

Symmetrical and Mesokurtic. The sediment at this station is predominantly fine grained

(Figure 121).



Figure 121: Sediment grain-size distributions for Guapo Bay Station CH1

The dynamics of the berm at this station and the distinct changes occurring are shown in

Figure 122. Recession of the backshore cliff was not observed, however, there was a filling-

in of sediment at the base of the low cliff where a shallow gully once existed. Sediment

losses were observed during 2006 – 2008 along the beach face. The changes observed on

this station can be as a result of the sediment transport system within this bay.

Figure 122: Selected beach profiles for Guapo Bay (Station CH 1) for the period 2004 – 2008

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Guapo Bay - Station CH1

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Station 4b:

This station is located at the site of the landing of the British Gas Pipeline. It is located

approximately 50 m east of Station 5. The beach has a low gradient and is backed by a

moderately sloping hill that was reshaped after the landing of the Gas Pipeline in 2004. The

original benchmark was lost during the construction phase and hence long term analysis of

the beach widths and volume could not be investigated. The beach now at this station is

fairly wide and has a gentle slope (Plate 42).

Plate 42: Station 4b Guapo Bay showing gently sloping beach and backshore vegetation (February 2007)

The wind approaches this station from the east-southeast with an average speed of

2.42 m/s (+/-0.81 m/s). Waves approach from the north, with a mean significant wave

height of 0.22 m (+/-0.08 m). Wave period averages 7.56 s (+/-0.86 s) while the breaker


12.10 cm/s (range 4.27-18.67cm/s, +/- 3.77 cm/s) and flows predominantly to the west

(Table 13).


Gravely SAND with a mean and median grain size of 0.19 mm. The sample consists of


The upper beach sediment is moderately sorted, Coarse Skewed and Very Leptokurtic.



(0.0625 - 2.0mm) and 0.05% Mud (<0.0625mm). The mid-beach sediment is well sorted,







sorted, Coarse Skewed and Very Leptokurtic. The sediment at this station is predominantly

fine grained (Figure 123).

Figure 123: Sediment grain-size distributions for Guapo Bay Station 4b

From 2004 – 2008 the bay has been in dynamic equilibrium with changes in the sediment

levels along the entire transect from the backshore to the near shore zone (Figure 124).

This can be as a result of longshore and cross shore movement of sediment along the

coastline.

Figure 124: Selected beach profiles for Guapo Bay (Station 4b) for the period 2004 – 2008

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Sediment Histogram Guapo Station 4b

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Guapo Bay - Station 4b

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Station 5:

Station 5 is located approximately 100 m east of Station 5a and is the longest standing

monitoring station on Guapo Beach. The low gradient wide beach is backed by a low cliff at

this station (Plate 43).

Plate 43: Guapo Beach Station 5, Clifton Hill showing gently sloping beach (July 2007)

The wind approaches from the east-southeast with an average speed of 2.16 m/s

(+/-1.40 m/s). Waves at this station approach from the north. Mean significant wave height

is 0.19 m (+/-0.08 m) with a period of 7.56 s (+/-1.16 s), while the breaker height (spilling


(range 3.4-29.17 cm/s, +/- 6.66 cm/s) and flows predominantly to the west (Table 13).




The sediment is Well sorted, Near Symmetrical and Mesokurtic.

The mid-beach sample is classified as Slightly Gravely SAND with a mean grain size of



is well sorted, Near Symmetrical and Mesokurtic.

The lower beach sample is classified as Slightly Gravely SAND with a mean grain size of


99.67% Sand (0.0625 - 2.0 mm) and 0% Mud (<0.0625 mm). The sediment is Well sorted,




Figure 125: Sediment grain-size distributions for Guapo Bay Station 5

Selected profiles for this station from 2004 – 2008 (Figure 126) indicates that although

distinct changes in the nearshore and offshore regions are observed, the beach is generally

in dynamic equilibrium (Table 15).

Figure 126: Selected beach profiles for Guapo Bay (Station 5) for the period 2004 – 2008

However, Figure 127 shows that for 21 years during the period June 1987 to July 2008, the

beach width at this station increased. These changes were not constant but fluctuated in

response to anthropogenic activities. The increases to beach width commenced subsequent

to dredging activities for the Atlantic LNG plant as heavy mineral sediment (magnetite)

accumulated on the beach (and at this station). This sediment can still be seen at this beach

in the upper beach areas.

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Guapo Bay - Station 5

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Figure 127: Plot of Beach Width vs. Number of days for Guapo Bay Station 5 for the period June 1987 – July 2008

Station 5a:

The westernmost station on Guapo Beach (Station 5a) is located landward of the rubble

mound breakwater (Plate 44). The cliff at this station has been modified to a uniform

moderate sloping gradient.

y = 0.0019x - 2.1543R² = 0.3004

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GUAPO BAY - Station 5Change in Beach Widths

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Plate 44: Westernmost on Guapo Beach, Clifton Hill showing offshore breakwater (July 2007)

Wind approaches from the east-southeast with an average speed of 2.70 m/s (+/-0.8 m/s).

Mean significant wave height is 0.2 m (+/-0.1 m) with a period of 6.3 s (+/-2.7 s), while the

breaker height (spilling breaker) is 0.3 m (+/- 0.1 m) approaching from the north. Mean

longshore current averages 15 cm/s (range 0.0-23.3 cm/s, +/- 7.3 cm/s) and flows to the

west (Table 13).

During the period 2004 – 2006, the beach at this station was in dynamic equilibrium

(Table 15). Construction activities in this region of the bay resulted in 2.89 m shoreline

retreat in 2007 (Table 15). The location of the breakwater resulted in accumulation of

sediment in the leeward side of the structure forming either tombolos or salients. The

lowest elevation at this region of the bay was obtained in January 2006 while April 2008

saw the highest beach elevations (Figure 128).



Figure 128: Selected beach profiles for Guapo Bay (Station 5a) for the period 2004 – 2008

A plot of change in beach widths and volume between October 1999 and April 2008 shows

a decrease in both parameters until 2006, when a sharp increase was observed

(Figure 129). Due to construction works in the vicinity of this station, monitoring was not

performed again until August 2007. During that time, re-shaping of the backshore,

construction of the seawall to the west and the breakwater resulted in a significant

increase in the beach width. This change in both width and volume is reflected in

Figure 129. Over time, it is expected that beach stability will be attained in this region of

the bay.

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2006 01 2006 10

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Guapo Bay - Station 5a

2004 - 2008 BM



Figure 129: Plot of Beach Width and Volume vs. Number of days for Guapo Bay Station 5A for the period March 1985 – April 2008

4.4.5 Station Beach - La Brea

This is a small beach approximately 1.6 km long located east of Brighton Port. There were

originally four stations along this bay. The eastern station was covered up and became

overgrown with vegetation while the western station was destroyed during construction

activities of the new port. Figure 130 is an IKONOS (2007) image of Station Beach, La Brea

showing the location of the two remaining IMA stations on this bay.

y = -0.0024x - 2.4538R² = 0.1477

y = -0.005x + 0.3259R² = 0.4429

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GUAPO BAY - Station 5AChange in Beach Widths

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Figure 130: IKONOS image of Station Beach, La Brea showing Stations location (2007)

Station 2:

The central section of the bay (Station 2) is backed by low topography with a gently sloping

wide beach (Plate 45). Dynamic equilibrium was exhibited at this station during the period

2004 – 2008 (Table 15).

2 3



Plate 45: Station Beach, La Brea, (Station 2) showing flat backshore and wide beach (July 2007)

Littoral data collected during 2004 – 2008 at this site indicates that wind approaches from

the north east with speeds averaging 2.56 m/s (+/- 0.97 m/s). Waves approach from the

north-northwest with a mean significant wave height of 0.23 m (+/- 0.12 m), a period of

7.2 s (+/-1.18 s) and a breaker height (spilling breaker) of 0.25 m (+/- 0.12 m). Mean

longshore current averages 13.07 cm/s (range 2.13 – 28.0 cm/s, +/- 6.30 cm/s) flowing

predominantly in a westerly direction (Table 13).





The mid-beach sample is classified as SAND with a mean and median grain size of 0.21 mm.

The sample consists of 0.0% Gravel (>2.0 mm), 99.98% Sand (0.0625 - 2.0 mm) and 0.02%

Mud (<0.0625 mm). The mid-beach sediment is Very well sorted, Near Symmetrical and

Mesokurtic.

The lower beach sample is classified as Gravelly SAND with a mean and median grain size

of 0.19 mm. The sample consists of 6.57% Gravel (>2.0 mm), 93.29% Sand

(0.0625 - 2.0 mm) and 0.13% Mud (<0.0625 mm). The lower beach sediment is poorly

sorted, Strongly Coarse Skewed and Very Leptokurtic (Figure 131).



Figure 131: Sediment grain-size distributions for La Brea Bay Station 2

Selected profiles indicate the changes that occurred at this station (Figure 132). The major

changes in elevation along this profile were observed between 48 – 72 m from the

benchmark within the surf zone. Variation in the sediment levels along the beach face were

also observed although not as distinct as in the surf zone.

A plot of changes in beach width and volume from July 1991 to November 2008 showed

dramatic increases (Figure 133). There were proportional increases in both width and

volumes. These increases may be attributed to sediment movement from the reclamation

activities of the new port at Brighton by waves that would refract around the new artificial

headland.

Figure 132: Selected beach profiles for Station Beach La Brea (Station 2) for the period 2004 – 2008

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La Brea Station 2

2004 - 2008 BM



Figure 133: Plot of Beach Width and Volume vs. Number of days for Station Beach, La Brea Station 2 (central) for the period July 1991 – November 2008

Station 3:

Station 3 is located along the seawall at Station Beach. This section of the bay has a fairly

wide beach that slopes gently to the nearshore (Plate 46). The beach is in dynamic

equilibrium (Table 15) even though distinct changes to the beach face are observed. When

the berm in front of the river is built up, the river to the east of the seawall occasionally

flows along the base of the seawall resulting in erosion. For the most part however, the

berm is wide and well developed.

y = 0.0035x - 5.1341R² = 0.7374

y = 0.0042x - 3.8489R² = 0.8076

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Station Beach - Station 2Changes in Beach Widths and Volumes

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Plate 46: Station 3 (west) Station Beach, La Brea showing wide beach (January 2007)


Waves approach from northwest with a mean significant wave height is 0.23 m

(+/-0.11 m). Wave period averages 7.5 s (+/-1.49 s), while the breaker height (spilling


(range 4.3-32.7 cm/s, +/- 7.39 cm/s) and flows west (Table 13).




upper beach sediment is well sorted, Near Symmetrical and Mesokurtic.



2.0 mm) and 0.05% Mud (<0.0625 mm). The mid-beach sediment is well sorted, Near





Near Symmetrical and Mesokurtic. The sediment sizes along this region of the bay are

predominantly fine grained (Figure 134).



Figure 134: Sediment grain-size distributions for La Brea Bay Station 3

Selected profiles for this station indicate the changes along this transect which tapers at

80 m from the benchmark (Figure 135). Beach width and volume changes between January

1994 and June 2008 show a distinct increase in both factors (Figure 136). It is very evident

that sedimentation has been occurring on this beach as illustrated by the positive gradients

of the best-fit lines.

Figure 135: Selected beach profiles for Station Beach La Brea (Station 3) for the period 2004 – 2008

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La Brea Station 3

2004 - 2008 BM



Figure 136: Plot of Beach Width and Volume vs. Number of days for Station Beach, La Brea Station 3 (central) for the period January 1994 – June 2008

4.4.6 Dhein’s Bay

Dhein’s Bay is a very small bay located on the southern side of the north western peninsula

of Trinidad. Figure 137 is an IKONOS (2007) image of Dhein’s Bay showing the location of

the IMA station on this bay. To the east and west of the bay is a low seawall. The beach is

narrow and consists of coarse grained sediments (Plate 47).

y = 0.0061x - 1.4793R² = 0.6919

y = 0.0052x - 0.3194R² = 0.7002

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Figure 137: IKONOS image of Dhein’s Bay showing Station location (2007)

Plate 47: Dhein’s Bay, showing narrow cobble/pebble beach (July 2007)



Littoral data collected during 2004 – 2008 at this site indicates that wind approaches from

the southeast with an average speed of 2.67 m/s (+/-0.29 m/s). Waves at this bay approach

from the south. Mean significant wave height is 0.2 m (+/-0.08 m) with a period of 7.07 s

(+/-1.28 s), while the breaker height (spilling breaker) is 0.27 m (+/- 0.18m). Mean

longshore current averages 8.27 cm/s (range 7.47-9.33 cm/s, +/- 0.7.9 cm/s), and flows

west (Table 13).




The upper beach sediment is moderately well sorted, Coarse Skewed and Very Leptokurtic.

The mid-beach sample is classified as Gravelly SAND with a mean grain size of 0.39 mm and

median grain size of 0.29 mm. The sample consists of 9.74% Gravel (>2.0 mm), 90.2% Sand

(0.0625 - 2.0 mm) and 0.07% Mud (<0.0625 mm). The mid-beach sediment is poorly

sorted, Strongly Coarse Skewed and Leptokurtic.




is Very poorly sorted, Strongly Fine Skewed and Very Platykurtic (Figure 138).

Figure 138: Sediment grain-size distributions for Dhein’s Bay

This beach is in dynamic equilibrium (Table 15). Wave energy at this bay is predominantly

too low to effect any drastic changes to the beach. Changes to this profile during the period

2004 – 2008 are shown in Figure 139. Accumulation of cobbles and pebbles along the

beach face is responsible for the higher elevation in July 2008 possibly due to reclamation

material immediately west of the IMA’s station.

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Figure 139: Selected beach profiles for Dhein’s Bay for the period 2004 – 2008

4.4.7 Chagville Bay

Chagville Bay lies within the larger Carenage Bay. The Cuesa River exits at the eastern end

and a storm drain at the west. Figure 140 is an IKONOS (2007) image of Chagville Bay

showing the location of the two IMA stations monitored on this bay.

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Dhein's Bay

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Figure 140: IKONOS image of Chagville Bay showing Stations location (2007)

Station 1:

At station 1 on the western end of the bay, the beach is fairly narrow with a low backshore

cliff (Plate 48).

1

3



Plate 48: Chagville Bay Station 1, showing narrow beach and low backshore cliff Station 3 (July 2007)

Littoral data collected during 2004 – 2008 indicates that wind approaches from the

southeast with an average speed of 1.48 m/s (+/-0.53 m/s). Waves at this station approach

from the southeast. Mean significant wave height is 0.15 m (+/-0.11 m) with a period of

7.36 s (+/-0.48 s), while the breaker height (spilling breaker) is 0.2 m (+/- 0.14 m). Mean

longshore current averages 6.83 cm/s (range 0-12.8 cm/s, +/- 4.61 cm/s) and flows in a

west- southwesterly direction (Table 13).

From Table 14 it is shown that the upper beach sediment sample is classified Slightly



The sediment is moderately well sorted, Near Symmetrical and Leptokurtic.

The mid-beach sample is classified as Sandy GRAVEL with a mean grain size of 1.16 mm


64.54% Sand (0.0625 - 2.0 mm) and 0.08% Mud (<0.0625 mm). The sediment is Very

poorly sorted, Coarse Skewed and Platykurtic.

The lower beach sample is classified Slightly Gravelly SAND with a mean grain size of



is well sorted, Near Symmetrical and Platykurtic (Figure 141).



Figure 141: Sediment grain-size distributions for Chagville Station 1

At Station 1 on the western end of the bay (Plate 48) the beach is in dynamic equilibrium

(Table 15). There were no major changes observed at this profile during the period 2004 –

2008 (Figure 142). An offshore bar was observed in May 2004 between 64-80 m from the

benchmark. The low backshore cliff is stable and the beach has a very gentle slope that

extends into the near shore environment. Changes to the beach width and volume for the

period February 1985 – July 2008 shows that the beach is eroding (Figure 143). Both

parameters show negative trend-line gradients. The two significant negative spikes in the

data set are attributed to changes in the beach after storm surge events.

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Figure 142: Selected beach profiles for Chagville (Station 1 - West) for the period 2004 – 2008

Figure 143: Plot of Beach Width and Volume vs. Number of days for Chagville Beach Station 1 (west) for the period February 1985 – April 2008

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y = -0.0011x + 1.7879R² = 0.6636

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Chagville Beach - Station 1Changes in Beach Widths and Volumes

February 1985 - July 2008

Bea

ch W

idth

(m)

Be

ach

Vo

lum

e (

m3 )




Station 3:

At Station 3 in the central section of the bay the beach is narrow with cobbles in the upper

region and sand in the mid – lower beach (Plate 49). The beach also exhibits dynamic

equilibrium (Table 15) but there is more variation in the sediment elevation as compared

to the western station (Figure 145). This part of the beach is artificially nourished as it is an

important recreational site. Plans have been drafted to protect this coastline by

constructing a series of offshore breakwaters.

Plate 49: Chagville Bay Station 3, showing (July 2007)

Wind approaches from the southeast with an average speed of 3.1 m/s (+/-1.21 m/s).



southeast. Mean longshore current averages 8.83 cm/s (range 3.20-17.50cm/s,

+/- 4.89cm/s) and flows west-southwest (Table 13).







The mid beach sample is classified as Slightly Gravelly SAND with a mean grain size of



sediment is poorly sorted, Strongly Coarse Skewed and Platykurtic.

The lower beach sample is classified as Gravelly SAND with a mean and median grain size

of 0.15 mm. The sample consists of 0% Gravel (>2.0 mm), 98.87% Sand (0.0625 - 2.0 mm)

and 1.13% Mud (<0.0625 mm). The lower beach sediment is well sorted, Near Symmetrical

and Mesokurtic. The sediment at the upper and lower beach is fine grained while the mid

beach is coarse grained. The coarse grained sediment at this station is mainly coral

fragments and pebbles (Figure 144).

Figure 144: Sediment grain-size distributions for Chagville Station 3

0

10

20

30

40

50

60

70

80

90

100

-4 -3 -2 -1 0 1 2 3 4

Cu

mu

lati

ve (

%)

by

Wei

ght

Sediment size (Phi)

Chagville Station 3 Sediment

UB

MB

LB

0

10

20

30

40

50

60

70

80

90

100

-3 -2 -1 0 1 2 3 4

Per

cen

tage

(%

)


Sediment Histogram for Chagville Station 3

UB

MB

LB



Figure 145: Selected beach profiles for Chagville (Station 3 - Central) for the period 2004 – 2008

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104


Ele

va

tio

n (

m)

2004 02 2004 05

2007 05 2007 06

2007 10 2008 07

Chagville - Station 3

2004 - 2008 BM





5 CONCLUSION

Most of the beaches and bays monitored by the IMA between 2004 and 2008 were in

dynamic equilibrium (Figure 146). The north coast beaches are predominantly stable and

in dynamic equilibrium. Although this coastline is backed by the more resistant

metamorphic rocks, erosion was observed on the sandy beaches where there was a

lowering of sand elevations and not as a result of cliff recession. At Macqueripe Bay,

erosion of the backshore area resulted in the re-construction of the seawall that backed this

bay. The seawall however was extended to protect the entire length of the bay. During

2004 - 2008, only sections of Las Cuevas and Blanchisseuse Bays were eroding. Changes to

beach width and volume at Maracas Bay indicated that the bay is stable, very dynamic and

susceptible to impacts from storm surges. The bay however rapidly recovers and

restoration can be observed within 4-6 months of the event. The central section of Las

Cuevas Bay showed an increase in both beach width and volume. The eastern and western

sections however are experiencing erosion. This bay also is very dynamic and susceptible

to storm surges with recovery taking approximately 4-6 months. At Blanchisseuse Bay,

minor increases were observed in both the width and volume and the beach is considered

stable and very dynamic.

On the Eastern coastline, the long term trend of the changes to beach width and volume at

Guayamara Bay showed that the beach is extremely dynamic but stable. Significant

seasonal fluctuations take place at this high energy beach. At Cocos Bay, the investigation of

beach width and volume showed that significant erosion is occurring at the northern and

southern sections at stations 1 and 5, while the central region of the bay is dynamic but

stable. These sections of coastline experienced the most erosion of all bays monitored,

although the bay is backed by extensive coconut palms and other low shrubs. The presence

of this vegetation is not sufficient to combat the erosive forces of the Atlantic waves. Profile

data at the Cocal spit and at the rip rap revetment also indicated stable beaches. Other

sections which were experiencing erosion were stabilized using hard engineering

structures. Field observations indicate that the northern section of Mayaro Bay is eroding

as evidenced by fallen coconut trees and slumping of the cliffs in this region of the bay. The

profile data however did not reflect this during this period. The central section of the bay is

dynamic but stable and showed a small increase in changes to beach width and volume

over the long term. The southern region of the bay experienced erosion during 2004 –

2005 but was in dynamic equilibrium until 2008.

All south coast beaches monitored exhibited dynamic equilibrium during 2004 -2008 with

the exception of the western region of Guayaguayare Bay and Punta del Arenal. Long term

analysis of changes to beach width and volume at Guayaguayare Bay however, indicate that



the beach is eroding in the central section as well. The erosion is much more pronounced in

the western section of the bay. This erosion was triggered by the laying of gas pipelines

which involved trenching in the offshore and backshore areas in this region of the bay.

Punta del Arenal was the only beach in the study that experienced accretion. This accretion

however was not a seaward extension of the beach but a vertical increase in the beach

elevation.

The west coast beaches were predominantly in dynamic equilibrium with the exception of

North Chatham in Irois Bay and at the western section of Guapo Beach. Erosion in North

Chatham was experienced every year of the study period and doubled during 2007 – 2008.

The region at west Guapo Beach was in dynamic equilibrium for the years 2004 – 2006.

Construction activities however resulted in erosion in 2007. At Station 5a, changes to the

beach width and volume in the early years indicated significant erosion occurring.

However, with the construction of the breakwater, the beach started showing signs of

accretion in the lee of the breakwater. Further east of the breakwater at Station 5, accretion

is evident. This accretion began soon after the dredging activities for the construction of

the Atlantic LNG plant. Mafic (dark) coloured offshore fine grained sediment (Magnetite)

became a prominent feature of the beach sediment in this region of the bay as the beach

accreted. Up to 2008, the beach continued to be stable and in dynamic equilibrium. At

Station Beach, La Brea, both stations in the central region of the bay experienced significant

accretion with respect to changes in beach width and volume. Expansion of the Port at

Brighton to the west, may have resulted in this accretion from reclamation sediments

deposited by the oncoming northerly approaching waves. Field observations also indicate

that significant accretion is occurring on the western end of the bay adjacent to the

reclamation site.

In the north western peninsula, the western region of Chagville beach showed erosion in

both beach width and volume. Cliff recession was not observed but migrating sediment due

to longshore transport resulted in lower sand elevations at this region of the bay. The

central section of the bay exhibited fluctuations in elevations but for most part appeared to

be in dynamic equilibrium.

The main factors driving erosion are the aspect or configuration of the bay, geology of the

backshore, hydrography, oceanography and sediment supply. For most bays in Trinidad,

erosion is a naturally occurring process caused by nearshore processes acting on soft or

unconsolidated coastlines. Other natural forces that exacerbate erosion include storm

surges, weathering, wind and surface run off. Coastal development, construction and

offshore activities such as offshore dredging or construction in the near shore zone also

have severe environmental impacts on the coastline interfering with the natural coastal

processes. Any disturbance to this natural equilibrium can alter wave energy and longshore

drift, often resulting in erosion.



On the north coast of Trinidad the erosion is predominantly a natural phenomenon. The

relatively straight east-west trending coastline is composed of crenulated, indented and

pocket bays which are exposed to the north swells of the Atlantic Ocean. In October 2005,

the effects of such extreme wave events give an indication of the severity to beach

morphology. The metamorphic rocks of the backshore cliffs in the north coast resists

erosion and therefore limits landward recession. There has been very little development

along the north coast to create any erosion due to anthropogenic factors.

The east coast beaches being exposed to the Atlantic Ocean experiences erosion on the low

topographical unconsolidated back shore. Storm surges also severely impact on these

beaches. Hard engineering structures in the form of seawalls and rip rap revetments have

been constructed to arrest the coastal erosion at some sections of Cocos Bay. Coastal

development along this coast has been restricted mainly to residential housing where

properties are located just behind the high water line. This exposes these properties to

coastal flooding in the event of storm surges.

The south coast is more sheltered than the north and east coast but the geology of the

backshore makes is very susceptible to erosion. Unconsolidated sands and clays succumb

to weathering, undercutting at the base from wave action and results in erosion. Laying of

pipelines and trenching in the near shore zone have resulted in increased rates of erosion

and relocation of one village at Guayaguayare Bay.

Most coastal development in Trinidad however is along the west coast. Industrial,

commercial and residential development extends from Point Fortin to Point Lisas and

Sealots to the north western peninsula. Natural erosion at the south west peninsula at

Columbus Bay and Corral Point has been occurring for decades. Various methods have

been unsuccessfully used to arrest the erosion. Until further studies are conducted to have

a comprehensive understanding of the coastal processes occurring in this region,

construction of any hard engineering structures would be ill-advised and most likely fail.

Seawalls have been built at Point Ligoure, Point Fortin, Clifton Hill and La Brea. An

extensive rip rap revetment and breakwater is located at Clifton Hill Beach to replace the

failed lattice type structure that previously existed. Other areas of this coastline on the

west coast are currently undergoing erosion. Most of these areas, for example, Columbus

Bay, Fullerton, Granville and North Chatham do not threaten life or property and as such

there has been no haste to construct coastal defence structures.

Hard engineering structures can arrest the erosion problems but, studies on the near shore

wave dynamics and coastal processes have to be conducted before any decision can be

made in selecting the most effective and appropriate method of coastal defence. The coastal

environment varies both spatially and temporally and therefore designs are site specific.

Usually long term wave offshore and nearshore wave data are needed to make accurate

predictions and inform optimum structure design. Factors such as cost, availability of raw



material, availability of scientific data for competent design, aesthetics, maintenance and

other resources play an integral part in the decision making process. Other factors such as

physical, biological, cultural, and safety for the general public also need to be taken into

consideration when deciding on hard engineering coastal defence solutions. Options to

remediate and arrest the erosion using hard engineering structures can range from

seawalls, rip rap revetments, groynes and breakwaters. Soft engineering methods such as

artificial beach nourishment, re-vegetation or even re-location can also be used. Regardless

of the method chosen, sound scientific studies must be conducted to inform the decision

making process.



Figure 146: Status of Coastline Map of Trinidad based on study conducted during 2004 – 2008.



6 RECOMMENDATIONS

The Coastal Conservation Project at the IMA provides valuable insight into the status of the

coastlines of Trinidad and Tobago. Monitoring of the beaches and bays around the

country’s coastline are generally well covered. Beaches currently not monitored are

primarily due to limitations of access and the general nature of the coastline, such as the

mud flats on the west coast. The findings of the research during 2004 – 2008 presented in

this report indicate that most beaches are in dynamic equilibrium. There are however some

beaches that are being eroded. Monitoring of beaches is generally conducted quarterly

whilst some are monitored monthly. There is a cost factor to the collection of data under

this project and hence decisions have to be made on the frequency in which these beaches

and bays are monitored. For stable beaches that are monitored monthly it can be

recommended that monitoring be conducted on a quarterly basis. Similarly, eroding

beaches that are monitored quarterly can be monitored monthly.

Within recent times new stations have been added at Erin Bay west (South Chatham), Galfa

Point in the south coast and Cedros Bay (Bonasse) in the south west peninsula. There are

however, other areas along the coastline that are not monitored but accessible such as;

specific parts of the wider Carenage Bay in the north west peninsula; Balandra and

Mathura Bays in the north east coast and San Souci Bay in the north coast. For the longer

bays such as, Cocos, Mayaro, Guayaguayare, Icacos, Granville, Las Cuevas and Blanchisseuse

bays, additional stations may be necessary to capture the erosion taking place since it is not

always reflected in the current IMA monitoring stations. Tables 16 to 19 presents a revised

monitoring programme based upon the findings of this research.



Table 16: Beaches and Bays to be monitored Bi-annually.

BEACH STATION NUMBER

/LOCATION REMARKS

To be monitored bi-annually (April - End of the winter season; October - End of the Summer Season). This would also allow

the preservation and maintenance of the benchmarks in the event of coastal

development or to provide advise to the Government or in the event of coastal

development or to provide advise to the Government or Government agencies

Salybia (Toco) Central

Guayamara Bay North

Saline Bay 2 - West (Fishing Depot)

Station Beach, La Brea

1A - West 2 - Car Park 3 - Seawall

Table 17: Beaches and Bays to be monitored monthly.


/LOCATION REMARKS

Maracas Bay

1 - West (Fishing Depot) 2 – Central

3 - Central (Life Guard Station) 4 - East

National Plan to develop this beach with major changes to the site layout. Important to have continuum of data set.

Tyrico 1 – West

2 - EAST (Life Guard Station)

Continue to monitor to pick up any change in the event of development at Maracas Bay

Cocos Bay

1 – North 2 – Spit

3 - Central (77km) 4 - Central (79km)

5 - South(81km)

Erosion along this bay and within recent times the construction and possibility of addition or further extension of hard engineering coastal protection structures. Additional Station to be added on the northern end of the bay where erosion is very prominent.

Mayaro Bay 2 - Central 3 - South

History of erosion and its dynamics. Additional Station to be added on the northern region of the bay where erosion is ongoing.



Table 17: Beaches and Bays to be monitored monthly cont’d.

Guayaguayare Bay

1 - East 2 – Central

3 - West

Much development over the past 15 years has changed the face of this bay with the landing of multiple Gas pipelines. Currently, construction of the new Fish Landing site and Marina may have adverse effects on this bay and regular monitoring is necessary.

Columbus Bay

1 - East 2 3 4 5

7 - IMA Original BM 8 - WEST

1B - Chinkit Trace

To maintain continuum of data for the proposed new research project and the interest which have been brought to the National fore in recent times.

Guapo Bay

1 – Vessigny 3A 4

4A CH 1

4B - BG Landing Site 5 - Old Golf Course

5A- Breakwater

Continued monitoring of this bay to determine changes from recently constructed hard engineering coastal protection structures.

Irois Bay 10 - North Chatham 1B - Chinkit Trace

Continues to experience significant erosion with threat to residential property.



Table 18: Beaches and Bays to be monitored quarterly.


/LOCATION REMARKS

Macqueripe Bay Central Monitoring of the dynamics of the beach as it adjusts to the recently constructed seawall.

Las Cuevas Bay 1 – West (River)

2 – Central 3 - East

Very dynamic beach with substantial changes taking place.

Blanchisseuse Bay 2 - West (Car Park) Dynamic beach. Private development currently taking place at this bay.

Grand Riviere

1 – West 2 – Central 3 – Central

4 – East (Hotel)

A popular turtle nesting beach, and should be monitored to inform management.

Moruga

Only cliff retreat measured at the moment.

Quinam Bay Central

High water line is at base of cliff resulting in erosion and eventual possible threat to the seawall at the southern boundary of the Car Park.

Los Iros Bay Central

High water mark is at base of recently constructed concrete fencing as well as to monitor the impacts of the recently constructed groyne East of the benchmark.

Erin Bay

1 - Fishing village To continue monitoring the dynamics of the spit and the impacts of the river outflow.

2 - South Chatham Recently established monitoring station to monitor the dynamics of this bay

Punta Del Arenal, Icacos

One of the very few beaches in Trinidad that is in a state of accretion. Support data for Columbus Bay Study

Cedros Bay (Bonasse)

1 - EAST 2 - CENTRAL

3 - WEST

Recently established monitoring station to monitor the dynamics of this bay.



Table 18: Beaches and Bays to be monitored quarterly Cont’d.


/LOCATION REMARKS

Granville Bay New benchmark established at this bay.

Dhein’s Bay

Preservation and maintenance of the benchmarks in the event of coastal development or to provide advise to the Government or in the event of coastal development or to provide advise to the Government or Government agencies

Chagville Bay

1 – West 3 - Central

William’s Bay Car Park

Galfa Bay Recently established monitoring station to monitor the dynamics and the erosion of the mangroves that backs this bay.

Table 19: New monitoring stations to be established (to be monitored quarterly).


/LOCATION REMARKS

Matura Bay End of access road to

bay

A popular turtle nesting beach, and should be monitored to inform management.

Balandra Bay At the seawall To monitor the effectiveness of the seawall.

Cocos Bay Northern end of bay Erosion reported at this section of the bay.

Mayaro Bay Northern region of bay Erosion reported at this section of the bay.

Irois Bay

Two (2) additional stations to be

established. One at Sunset Beach and the other west of the Cap-

de-Ville River

Significant erosion reported at this bay.



Also, the IMA has the technology and the capability to broaden its research capacity in

shoreline monitoring. The changing coastline can be mapped through remote sensing using

satellite imagery (IKONOS) and images obtained from Google maps. This data can be

ground truthed by conducting shoreline monitoring studies at areas that show signs of

erosion. Coupled with the current research at the IMA, a policy framework for building line

setbacks for the management of coastal development can be drafted. This can be used to

advise government on enacting laws for any coastal development based on location and

other influencing factors. This data will form a critical and integral part of the Integrated

Coastal Zone Management process.

The IMA has a wealth of data from research conducted over the years that has not been

analyzed to develop trends and models for the changing coastline. It is recommended that

the IMA procure specialists in the relevant fields who can statistically analyze and model

the voluminous amount of data stored in the archives using specialized software. The

findings of these studies can be made available to the public in the form of reports and

published works in journals. There also exists a need for greater collaboration among other

government agencies and academic institutions in coastal monitoring and protection to

avoid duplication of research, resources, and to build capacity.



7 REFERENCES

Bachew, S and Hudson, D. 1986. Evaluation of Coastal Erosion Processes for Recreational

Facility at Granville Bay, South Trinidad. Institute of Marine Affairs. Document prepared

for the Town and Country Planning Division, Ministry of finance and Planning.

Bachew, S, Hudson, D and Gerrard, A. 1983. An analysis of the Coastal Erosion Problem at

Los Iros Trinidad, West Indies. Institute of Marine Affairs. Document prepared for the

Town and Country Planning Division, Ministry of Finance and Planning.

Bachew, S, Joseph, P and Hudson, D. (nd). Hydrographic and Marine Geological Surveys of

Los Iros Bay, southern Trinidad. Institute of Marine Affairs..

Bertrand, Diane and Lewis, Neil. 1989. Beaches handbook of Trinidad. Institute of Marine

Affairs.

Cambers, J. 1998. Coping with beach erosion. UNESCO Coastal Management Sourcebooks 1,

UNESCO, 117 pp.

Chadwick. A, D. Reeve, C. Reeve. 2004. Coastal Engineering: Processes, Theory and Design

Practice. SPON.

Chrzastowski, Michael J. . 2005. Beach Features. In Encyclopedia of Coastal Science.

Springer Netherlands. Pp 145-147

Darsan, J. 2005a. A comparative study of the coastal geomorphology of Cocos Bay and Las

Cuevas Bay, Trinidad. Caribbean Geography 14(2): 116-132.

Darsan, J. 2005b. A comparative study of the coastal geomorphology of Manzanilla and Las

Cuevas Bays, along the eastern and north-western coasts of Trinidad. Unpublished BA

Thesis., Department of Geography and Geology, University of the West Indies, Mona

Campus, Kingston, Jamaica.

Darsan, J. 2012. An analysis of the coastal geomorphology and evolution of Cocos Bay

(Manzanilla), Trinidad. Unpublished PhD Thesis., Department of Geography and

Geology, University of the West Indies, Mona Campus, Kingston, Jamaica.

Deane, C. 1971. Coastal Erosion Point Fortin to Los Gallos. Second Interim Report. 1971.

Government of Trinidad and Tobago, Ministry of Planning and Development and

Ministry of Works.

Didenkulova, I., A. V. Slunyaev, E. N. Pelinovsky, and C. Kharif. 2006. Freak Waves in 2005.

Nat. Hazards Earth Syst. 6, 1007–1015, 2006.

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Georges, C. (nd). The Physical Characteristics of Salybia, Vessigny and Los Iros Beaches.

Institute of Marine Affairs. Technical Report.

Georges, C., Hudson, D. and Bachew, S. 1986. The dynamics of the Erin Spit south Trinidad.

In Transaction of 11th Caribbean Geological Conference, Barbados.

Institute of Marine Affairs 1993a. Final Report: Coastal Erosion Protection Project, Station

Beach, La Brea, Trinidad.

Institute of Marine Affairs 1993b. Draft Final Report: Environmental Impact

Assessment/Feasibility Study for the Laying and Landing of Project Oxygen Submarine

cables in Saline Bay. Document prepared for the Telecommunication Services of

Trinidad and Tobago.

Institute of Marine Affairs 1999. Final Report: Environmental Impact Statement for the

Americas 1 Submarine Cable Project, Macqueripe Bay, Trinidad.

Institute of Marine Affairs 2002. Risks Posed to Leatherback Turtle Egg Clutches at Grand

Riviere Beach, Trinidad

Institute of Marine Affairs 2003. Final Report: Monitoring of Beach Stability and Sediment

Quality at Guapo Bay, Trinidad.

Institute of Marine Affairs Research Projects, 1995.

Institute of Marine Affairs, 2004. A Guide to Beaches and Bays of Trinidad and Tobago. Yara

Trinidad Ltd.

Kenny, J. S. 1995. The Changing Coastline of the Cedros Peninsula, Trinidad. In Living

World, J Trinidad and Tobago Field Naturalist Club, 2002. 6pp.

Kenny, J. S. 1998. Trinidad and Tobago – Sinking or Swimming. Alternative explanation of

some natural coastal phenomena. Open Lecture Series University of the West Indies, St.

Augustine. 7pp.

Oostdam. B, 1984. Coastal egression and Transgression at the Junction of Serpent’s Mouth

and the Gulf of Paria Trinidad. Proc. 10th Carib. Geol. Confer., Cartagena, Colombia, p.

318-329

Saunders, J.B., 1998. Trinidad and Tobago Geological Map.

Sharp, J. M. Jr. and D. W. Hill. 1995. Land subsidence along the northeastern Texas Gulf

coast: Effects of deep hydrocarbon production. Environmental Geology. Springer Berlin

/ Heidelberg. Volume 25, Number 3 April, 1995. pp 181 – 191.

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