Sustainable Solutions for Coastal Zone Management of Lowland and

River Delta Coastlines

By

Nabil M. Ismail1, M.ASCE, Robert L. Wiegel2, Hon. M.ASCE

1] Prof. of Coastal Engineering, Maritime Academy, Miami, Alexandria, Egypt;

Director, Costamarine Technologies, Davis, CA, USA, nbismail@usa.net

2] Prof. Emeritus, Dept. of Civil and Environmental Eng., University of

California, Berkeley, CA., USA

Background • In recent years, the impacts of natural disasters are more and more severe

on coastal lowland areas and barrier islands. Furthermore the impact of anthropogenic modifications produce coupled coastal problems. In the future, the impact of global warming and climate change (sea level rise, storm surges, coastal floods) will become more critical. People are increasingly occupying low-lying areas that are exposed to flooding, thus exacerbating their vulnerability to extreme events. The importance and scale of coastal defense structures will increase accordingly, and thus potentially generating greater environmental adverse impacts.

• At a global scale, effects of accelerated climate changes was demonstrated in autumn 2010 when the storm Becky reached the Santander Bay, Spain with a peak of nearshore (significant) wave height of about 8 m, and a storm surge reached 0.6m. On the Nile Delta Coast, effects of intense winter storms on Alexandria coastline and its adjacent shores appeared in the last decade to be more progressive in 2003, 2006 and recently in December 2010. The latest storm in December 2010, which hit the Nile Delta showed that generated surges, up to 1.0m as well as a maximum of 7.5m in the offshore presented a major natural hazard in coastal zones. The recent adverse impact of Super Sandy hurricane in late October 2012 on the east cost of the US is living example of progressive global climate changes.

Presentation Outline A. Status of World’s River Delta Coastlines, Barrier

Islands and Lowland Coastlines under Global

Climatic Changes.

Objectives and Methodology

B. Case Studies; California-Pacific Ocean and France

– Gulf of Lions.

C. Coastal Processes at Rosetta Headland and

Seawall-Beach Interaction.

D. Prediction of Large Scale Shoreline Modifications,

Nile Delta Coastline and Wave Overtopping.

E. Conclusions & Recommendations.

Location of case studies in the Gulf of Lions, France and the Gulf of Mexico, California, USA

Mississippi River Delta USA

before 2005

River

Véran Seawall

2005

Ventura River Delta

Monterey

USA

California

Ventura

Pacific Ocean

Véran Seawall - France

N

Site location and survey

Lighthouse

GI 17

GI 18

GI 16

GI 15 GI 14

GI 15`

Véran Seawall

500 m

St Anne Graude a Dent

A. Status of World’s River Delta Coastlines,

Barrier Islands and Lowland Coastlines under

Global Climatic Changes

Nile Delta, Egypt, as revealed by Satellite Imagery 1980

1900

1964

1971

1988

1990

1991

1996

2000

East Seawall

1989 - 1990 West Seawall

1989 - 1990

Rosetta promontory * 1800 to 1909 Shoreline Advance (3.5 km) 25 m/yr (E), 20 m/yr (W) * 1900 to 1996 Shoreline retreat 50 m/yr (4.8 km in 96 years) * Operation of Aswan High Dam 1965

Coastal Retreat of Rosetta Headland (1900 to 2000) and M. Ali Seawall

Wave Dominated Nile Delta Deltaic barriers Islands ~parallel to shore

Beach erosion at barrier

islands, Delaware, USA,

(Galgano, 2007)

Subsidence at Po river delta,

Italy (Syvitski, 2008)

Beachfront road and boardwalk damaged by Hurricane Jeanne ( Sept. 2004)

Damaged boats

in a marina

Impact of Global Climate Change on U.S Eastern Coastline

Damages by Super Hurricane Sandy (Oct. 2012)

Brilliance of the Seas Cruise Ship Faces Heavy Mediterranean Weather, Alexandria, Dec. 13, 2010

Mohamed Ali Seawall

Beach segment after 2010 storm

Abu Qir Bay

Restaurants Complex, Alexandria Coastal

Road , Dec. 2010

Alexandria Coastal Road , Dec. 2010

Flooding

Flooding at Mohamed Ali

Seawall, Dec. 2010

Objectives & Methodology Assess the impact of anthropogenic modifications, such as the absence

of river flow on coastal morphology of Deltas.

Evaluate impact of recent storm surge and wave overtopping on

upgrading of seawalls.

The second aim is to highlight the opportunities to use coastal soft

defense measures.

Clarify literature controversial impact of the effectiveness of seawalls to

slow, mitigate or increase coastal erosion at retreating shorelines.

The derivation of the results is based on the examination of field data

collected on the Nile Delta Rosetta seawalls, constructed in 1990, after

the operation of the Aswan High Dam in 1965, as well as field data on

seawalls in France and the USA.

Use has been made of recent satellite remote sensing data for the

Rosetta headland in 2007, 2008 and 2012, the numerical prediction of

GENESIS, and scale analysis of the governing equations of the wave-

river flow to obtain the length scale for reshaping of the Nile Delta

coastline at Rosetta. Laboratory data are used for verification.

B. Seawall Case Studies

Essential Methodology

Review of previous case studies of field monitoring

of coastal morphology modifications at two seawalls

located in Monterey Bay, CA, one seawall located at

Ventura river mouth, CA, USA and one seawall

located at the Rhone river mouth, the Gulf of Lions,

French Mediterranean coast.

CASE STUDIES I - USA Seasonal and Storm Erosion Patterns

Interaction of Seawalls and Monterey Beach, Calif., USA

Wave refraction analysis:

for Monterey Bay, California

(From Johnson, O’Brien, and Isaacs, 1948 : Wiegel 1964)

USA California

Monterey

Ventura

Eight Years of Field Monitoring (1986-1995) Gary Griggs, UC Santa Cruz, USA

Seawall Location 41a,

Monterey Calif.

Winter Storm 10/97

Monterey

Seawall, after

Repair 4/98

Ventura River Delta, California, USA (November 1999)

River Mouth

Parking Lot and Bike Path Near the Mouth of the

Ventura River (1995)

Shoreline Erosion at Revetment, Surfer’s Point,

December 1996.

Revetment

Sketch of Original Design at

Surfer’s Point.

Managed Retreat and Restoration

for Surfer’s Point.

Bke Path

Dunes

Water

Rock

Cobble

Sand

Bke Path

Dunes

Water

Rock

Cobble

Sand

Fairgrounds

River Levee

Concrete Barriers

Dunes

Erosion

Rip Rap

Revetment

Groin

Ventura

River

Mouth

Fairgrounds

Beach Access Walks

Dunes Restoration Area

Cobble Field 100 0 100 200

100 0 100 200

CASE STUDY II – France Seawall and Longshore Beach Erosion (Véran site, Gulf of Lions, France,

Mediterranean), Samat Olivier et al, 2005

Site Location and Survey

1 2 N

3

Rhone River

FRANCE

Lighthouse

Cross Shore Depth Variation of the Inner

Trough in front of Véran Seawall (Since 1988)

Shoreline Retreat along Véran Seawall

in the Long Term (1872-2004)

Morphological Changes at Rosetta Promontory Headland

Essential Methodology

Analysis of the extensive field data collected by the

Coastal Research Institute in Alexandria, Egypt and

Coastal Protection Authority, Cairo, on the coastal

changes astride Rosetta Branch, Nile Delta Coast. Use

has been made of the numerical prediction of GENESIS to

confirm the measured rates of long shore and offshore

sediment transport in the vicinity of the Rosetta Western

Seawall. A wave-current momentum index was used to

estimate the length scale of the coastline reshaping.

Evolution of Cross Shore Beach Profiles at the Western Seawall

Section W1 Section W2

WEST SEAWALL

1.5 km

EAST SEAWALL

3.5 km

Bathymetric Sea Bottom Contours (October 2002)

Astride Rosetta Headland (CRI / CPA)

Water Depth (m) - MSL

Scale

1

2 3

4

5

Predominant Waves NW/W –

NW

3 <(m) sH < ½

8.5 <(s) PT

Rhythmic Sea Bottom Patterns:

Length at the Seawalls = 270 m

0 1 2 3 km

Rhythmic Sea Bottom Patterns:

Length = 800 m

West Seawall

N

E

S

W

W1

W2

6 m

3m

2m

1m 0m

4m 5m

W1, W2 locations of cross shore profiles

N

E

S

W

MEDITERRANEAN SEA

Average

shoreline

Average

shoreline

Rhythmic Sea Bottom Bathymetry Patterns at Rosetta Seawall

(Ismail and El-Sayed, 2007)

Sediment Transport Rate (Genesis) along the Shoreline, West of

Rosetta Headland for One Year Period (2003 – 2005 Wave Data)

Distance along the Shoreline (m)

NET Transport Rate

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500

800

600

400

200

0

-200

-400

-600

-800

Sed

imen

t T

ran

sport

Rate

(1000 m

3)

0.28x106m3/yr

(Offshore) 0.28x106m3/yr

(North)

0.56x106m3/yr

(South)

Test 2

Test 1

Spit

Fluorescent Tracer

Experiment

Rosetta Western Seawall

Theoretical Offshore Transport

Rate 0.3x106 m3/year

Major Results

Mediterranean Sea

Western Revetment

Spit Eastern Revetment

Erosion

Accretion

Accretion

N

Comparison of Shoreline Changes over the

Period 1988-95 for Rosetta Promontory

D. Prediction of Large Scale

Shoreline Modifications

Erosion

2 0

S 0 g

2

0

0

1 La g C

2 h / U w

(C U)

Rsm

WAVES

JET OUTLET WIDTH, WO

BOTTOM

UC

UC = 0.6 UC

WAVES PHASE

SPEED. C WAVE

LENGTH, L

JET

VELOCITY UC

UC

h

Velocity and length scales of wave-current system

Characterization of Relative Strength of Wave

Momentum Thrust to Jet Momentum Flux, Rsm

Flow Visualization of

Wave Induced Mass Transport Pattern (Ismail, 1980)

Effects of Wave & Current Interaction on Coastal Circulation

Flow Visualization of

Momentum Jet in the Absence of Waves (Ismail, 1980)

Flow Visualization of

Momentum Jet in the presence of Waves (Ismail, Wegel 1981)

Wave and River

dominated delta Wave dominated delta

Shoreline

JET

Long shore

currents

S

Offshore

Waves

Dyed Flow

Shoreline

Waves & Jet

0.0 0.5 1.0 1.5 2.0 2.5 3.0

o

Rsm; Ratio of Wave Momentum Flux to Initial Jet Momentum Flux

*

Stagnation zone Rosetta

headland before

1964

Onshore

currents

Alo

ng

sho

re a

ccre

tio

n l

eng

th /

riv

er o

utl

et

ha

lf-w

idth

Alo

ng

sho

re e

rosi

on

len

gth

/ r

iver

ou

tlet

ha

lf-w

idth

Correlation between Wave-jet Relative Momentum

Thrust and Length Scale of the Alongshore Zone of

Accretion and Erosion

70

60

50

40

30

20

10

Jet

70

60

50

40

30

20

10

Major Results

Experimental Data (1980, 1981)

o

*

Western

Seawall (1990)

Eastern Seawall

(1990) Groins Set 5 (2003)

Mediterranean Sea

Rashid

Sand

Spit

Western

Seawall

Eastern

Seawall

Groin Set (5) More

Erosion

Flanking

Erosion

Mediterranean Sea

Rashid

(2007)

(2005)

offshore currents

Comparison of satellite

images of Rosetta

headland and coastal

zone in the years 2005 &

2007 (Google Earth).

N. Ismail

Major Results Satellite Images of Rosetta Seawalls & the Extent of Coastal Erosion Down-drift the Headland

Western

Seawall (1990)

Eastern Seawall (1990) Groins Set 5 (2003)

Mediterranean Sea

Mediterranean Sea offshore currents

N. Ismail

Major Results Satellite Images of Rosetta Seawalls & the Extent of Coastal Erosion Down-drift the

Headland (2012)

3.5 Km

1.5 Km

Wave height is denoted by the color scale in meters and wave direction by arrows.

165500 166000 166500

167000

167500

168000 168500 169000 169500 170000

3461500

3462000

3462500

3463500

3463500

3464000

3464500

Wave height (m)

Abu Quir Bay

El Tarh

El Amia Drain

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Seawall

ImSed Tran-2D model (2005)

D1. Wave Distribution across Abu Qir Bay with the Future Sea Level Rise

and the Maximum Yearly Wave Condition (Wave overtopping analysis)

MSL (0.0)

(-2.00m)

Crest

Boundary Wall

H. Tide (+0.5) H. Tide + storm surge (+1.0)

H. Tide + storm surge + wave height (+2.5m)

H. Tide + storm surge + wave height+ Run-up (+4.26)

L/s/m 2.0-6.0

Interaction between Abu Qir seawall and the sea in the current worst scenario.

Interaction between Abu Qir seawall and the sea in the future worst scenario due to sea level rise after 50 years.

-2.0 -3.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

0.0 1.0

3.0 4.0 5.0

-1.0

2.0 1.705 1.445

1.525

2.42

1.775

2.4 2.22 2.195 2.02

55.0 45.0 40.0 50.0

Seawall Land Profile No.(18)

2011

2.255 2.115 2.885

1.005 1.335

1.935 2.535

0.065 -0.375

New Cross Section of Seawall in 2011

Ele

va

tio

n, m

Sea bottom

MSL (0.0)

(-2.11 ml)

Crest

Boundary Wall

H. Tide (+0.5) H. Tide + storm surge (+1.0)

H. Tide + storm surge + wave height+ SLR (+3.45m)

H. Tide + storm surge + SLR+ wave height+ Run-up (+5.37) 18.0 -20.0 L/s/m

Plus SLR (+0.5)

Sea bottom

(Euro- Overtopping Manual 2008)

(de Waal &Van der Meer 1992)

(Van der Meer & Janssen 1995)

(Euro- Overtopping Manual 2008)

(de Waal &Van der Meer 1992)

(Van der Meer & Janssen 1995)

Overtopping

Overtopping

2 tons

E. Conclusions & Recommendations

Modifications of bottom morphology in front of and astride seawalls

depend on local wave climate and current conditions and sea level

variations. Further, the increased rate of longshore sediment

transport is strongly influenced by the cross-shore location of the

seawall in the surf zone.

Wave reflection and the generated wave patterns in front of seawalls

enhance the rate of offshore sediment transport as well as the

alongshore rate. This trend of increase was confirmed by the results

of fluorescent tracer experiments at Rosetta Western Seawall as well

as the reported results for seawalls located in France and UK.

“Interaction of waves and seawalls influences coastal processes in

front of the seawall”.

The rate of scour in front of Rosetta Western Seawall appears to be

diminishing currently after reaching a quasi-steady cross-shore

beach profiles. The continuation of collecting field data at Rosetta

headland is highly recommended to provide reliable basis for future

coastal zone management of the Nile Delta coastline.

The results show that current climatic changes and human

interference require the improvement of existing coastal defense

structures by upgrading, i.e. by elevating the top level of the rubble

mound/armor revetments and seawalls as demonstrated from the

analysis of the case study of Mohamed Ali seawall, Abu Quir.

Further, it is becoming necessary to improve the stability of the

cross shore-beach segment to create wave overtopping resistance

conditions under future storm conditions.

Despite the fact that low crested breakwaters proved to be

successful in some coastal locations, the shoreline response to their

placement needs to be identified. The results show that integrated-

innovative systems, composed of hard and soft structures, should

be explored to achieve the required level of coastal resilience.

Selection of soft protection alternatives for coastal zone

management should be considered if the use of hard

structures is proved to be adverse to the sustainability of

the coastal zone.

The soft engineering alternatives are such as beach

nourishment, stabilized sand dunes and sustainable barrier

islands and coastal lagoons. These natural systems would

act as a buffer zone to defend main land. The sustainability

of the integrated natural systems would require (1) barrier

island with shoreline restoration and (2) quality

management of hydrologic and vegetation restoration of

coastal lagoons.

Schematic of groundwater and surface

water flow paths and discharge locations

at a coastal lagoon

Highlights on Sustainability of Coastal Lagoons

Mediterranean

N

E

S

W

Mar Menor

Wetlands,

Spain

Future Outlook Passion for Coastal Regions

“Make no little plans: they have no magic to stir men’s blood and probably themselves will not be realized. Make big plans; aim high in hope and work, remembering that a noble, logical diagram once recorded will never die, but long after we are gone will be a living thing, asserting itself with ever growing insistency. Remember that our sons and daughters are going to do things that would stagger us. Let your watchword be order and your beacon beauty.”

- Daniel Hudson Burnham (1846-1912)

Architect for the 1893 World’s Columbian Exposition held at Chicago and lead author of the 1909 Plan of Chicago, USA.