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COASTAL SEDIMENT BUDGET FOR
JUPITER INLET, FLORIDA
By
KRISTEN MARIE ODRONIEC
A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
2006
ii
ACKNOWLEDGMENTS
I greatly thank my supervisory committee, Dr. Ashish Mehta, Dr. Robert Dean, and
Dr. Andrew Kennedy, for their assistance, guidance and insight throughout this research
project. I would also like to express my gratitude to the Jupiter Inlet District for
providing the financial resources needed to carry out this project. Thanks also go to
Michael Grella of the Jupiter Inlet District for always providing prompt answers to my
many questions and requests for information.
I would also like to thank all of my fellow coastal engineering students and friends,
whose support and distraction kept me sane. Finally, my ultimate thanks go to my family
who were always there for me providing patience, understanding, encouragement and
love.
iii
TABLE OF CONTENTS page
ACKNOWLEDGMENTS .................................................................................................. ii
LIST OF TABLES............................................................................................................. vi
LIST OF FIGURES .......................................................................................................... vii
ABSTRACT....................................................................................................................... xi
CHAPTER
1 INTRODUCTION ........................................................................................................1
1.1 Problem Statement .............................................................................................1 1.2 Objective and Tasks...........................................................................................1 1.3 Outline of Chapters ............................................................................................2
2 SITE DESCRIPTION AND DATABASE...................................................................3
2.1 Site Description and Recent History.......................................................................3 2.1.1 Site Description ............................................................................................3 2.1.2 Recent History ..............................................................................................4
2.3 Beach Profile Data..................................................................................................7 2.4 Ebb Shoal Volume Data .........................................................................................9 2.5 Dredging Data.........................................................................................................9 2.6 Beach Nourishment Data......................................................................................10
2.6.1 Downdrift Beach Nourishment Volumes ...................................................10 2.6.2 Updrift Beach Nourishment Volumes ........................................................14
3 SHORELINE AND BEACH VOLUME CHANGES................................................15
3.1 Shoreline and Beach Volume Change Calculation Methods................................15 3.2 Data Limitations and Uncertainties ......................................................................16
3.2.1 Data Uncertainties ......................................................................................17 3.2.2 Corrections for Non-Closure of Profiles ....................................................18 3.2.3 Corrections for Monument Relocation.......................................................19
3.3 FDEP Intersurvey Interval: 1974-1986 ...............................................................19 3.3.1 Shoreline Changes ......................................................................................20 3.3.2 Sediment Volume Changes ........................................................................20
iv
3.4 FDEP Intersurvey Interval: 1986-2002 ...............................................................21 3.4.1 Shoreline Changes ......................................................................................21 3.4.2 Sediment Volume Changes ........................................................................22
3.5 FDEP Intersurvey Combined Interval: 1974-2002..............................................23 3.5.1 Shoreline Changes ......................................................................................23 3.5.2 Sediment Volume Changes ........................................................................24
3.6 Volume Change Sensitivity to Depth of Closure .................................................27 3.6.1 Volume Change Sensitivity to Depth of Closure: 1974 to 1986 ...............28 3.6.2 Volume Change Sensitivity to Depth of Closure: 1986 to 2002 ...............29 3.6.3 Volume Change Sensitivity to Depth of Closure: 1974 to 2002 ...............30
3.7 JID Intersurvey Interval: 1995-1996 ...................................................................31 3.7.1 Shoreline Changes ......................................................................................32 3.7.2 Sediment Volume Changes ........................................................................32
3.8 JID Intersurvey Interval: 1996-1997 ...................................................................32 3.8.1 Shoreline Changes ......................................................................................32 3.8.2 Sediment Volume Changes ........................................................................33
3.9 JID Intersurvey Combined Interval: 1995-2004..................................................33 3.9.1 Shoreline Changes ......................................................................................33 3.9.2 Sediment Volume Changes ........................................................................33
3.10 JID Intersurvey Interval: 2001-2002 .................................................................34 3.10.1 Shoreline Changes ....................................................................................34 3.10.2 Sediment Volume Changes ......................................................................34
4 SEDIMENT BUDGET...............................................................................................39
4.1 Sediment Budget Methodology ............................................................................39 4.1.1 Sediment Budget Equation .........................................................................39 4.1.2 Method for Evaluating Sediment Budget ...................................................44 4.1.3 Effect of Length of Beach on Sediment Budget Calculations....................49
4.2 FDEP Sediment Budget Components...................................................................50 4.3 JID Sediment Budget Components.......................................................................52 4.4 Sediment Budget Results......................................................................................52
5 SUMMARY AND CONCLUSIONS.........................................................................54
5.1 Summary...............................................................................................................54 5.2 Conclusions...........................................................................................................55 5.3 Recommendations for Further Work ....................................................................57
APPENDIX
A FDEP LONG BEACH PROFILES FOR MARTIN AND PALM BEACH COUNTIES.................................................................................................................58
B JID BEACH PROFILES FOR PALM BEACH COUNTY .......................................75
C STORMS NEAR JUPITER INLET, FLORIDA........................................................82
v
LIST OF REFERENCES...................................................................................................83
BIOGRAPHICAL SKETCH .............................................................................................85
vi
LIST OF TABLES
Table page 2-1 Beach profile data for Martin and Palm Beach Counties...........................................8
2-2 Jupiter Inlet ebb shoal volumes (Source: Dombrowski, 1994) .................................9
2-3 Jupiter Inlet and interior sand trap dredging volumes..............................................10
2-4 Jupiter Inlet downdrift beach nourishment volumes ................................................12
2-5 Jupiter Inlet updrift beach nourishment volumes.....................................................14
4-1 Annual mean sand volumetric transport rates in the eastern zone (Source: Patra & Mehta, 2004, p. 11) ..............................................................................................43
4-2 FDEP sediment budget components for long analysis.............................................51
4-3 FDEP sediment budget components for short analysis ............................................52
4-4 JID sediment budget components ............................................................................52
4-5 Short FDEP and JID sediment budget results ..........................................................53
C-1 Storms occurring within 150 km of Jupiter Inlet .....................................................82
vii
LIST OF FIGURES
Figure page 2-1 Jupiter Inlet connecting the Loxahatchee River forks to the Atlantic Ocean.............3
2-2 FDEP range monuments north and south of Jupiter Inlet ..........................................5
2-3 Area map of Jupiter Inlet............................................................................................6
2-4 Photograph of Jupiter Inlet showing jetties and approximate location of sand trap..............................................................................................................................6
2-5 Jupiter Inlet Management Plan recommended increase in nourishment beach length........................................................................................................................13
2-6 Sand trap and Intracoastal Waterway deposition basin from which sediment is dredged to be used as nourishment ..........................................................................13
3-1 Schematic diagram defining depth of closure, where all offshore profiles converge to a certain depth.......................................................................................18
3-2 Shoreline change rates for the period from 1976 to 1982 in Martin County and from 1974 to 1990 in Palm Beach County...............................................................24
3-3 Unit volume change rates for the period from 1976 to 1982 in Martin County and from 1974 to 1990 in Palm Beach County ........................................................25
3-4 Shoreline change rates for the period from 1982 to 2002 in Martin County and from 1990 to 2001 in Palm Beach County...............................................................25
3-5 Unit volume change rates for the period from 1982 to 2002 in Martin County and from 1990 to 2001 in Palm Beach County ........................................................26
3-6 Shoreline change rates for the combined period from 1976 to 2002 in Martin County and from 1974 to 2001 in Palm Beach County ...........................................26
3-7 Unit volume change rates for the combined period from 1976 to 2002 in Martin County and from 1974 to 2001 in Palm Beach County ...........................................27
3-8 Unit volume change rates calculated with varying depths of closure for the period from 1976 to 1982 in Martin County and from 1974 to 1990 in Palm Beach County ...........................................................................................................29
viii
3-9 Unit volume change rates calculated with varying depths of closure for the period from 1982 to 2002 in Martin County and from 1990 to 2001 in Palm Beach County ...........................................................................................................30
3-10 Unit volume change rates calculated with varying depths of closure for the combined period from 1976 to 2002 in Martin County and from 1974 to 2001 in Palm Beach County..................................................................................................31
3-11 Shoreline change rates for the period from 1995 to 1996 just south of Jupiter Inlet in Palm Beach County .....................................................................................35
3-12 Unit volume change rates for the period from 1995 to 1996 just south of Jupiter Inlet in Palm Beach County .....................................................................................35
3-13 Shoreline change rates for the period from 1996 to 1997 just south of Jupiter Inlet in Palm Beach County .....................................................................................36
3-14 Unit volume change rates for the period from 1996 to 1997 just south of Jupiter Inlet in Palm Beach County .....................................................................................36
3-15 Shoreline change rates for the combined period from 1995 to 2004 just south of Jupiter Inlet in Palm Beach County..........................................................................37
3-16 Unit volume change rates for the combined period from 1995 to 2004 just south of Jupiter Inlet in Palm Beach County .....................................................................37
3-17 Shoreline change rates for the period from 2001 to 2002 in Palm Beach County ...38
3-18 Unit volume change rates for the period from 2001 to 2002 in Palm Beach County ......................................................................................................................38
4-1 Definition diagram displaying Jupiter Inlet along with all possible components in the sediment budget equation...............................................................................42
4-2 Sediment budget components specific to Jupiter Inlet.............................................44
4-3 Plot showing measurements of Jupiter Inlet’s ebb delta volumes, highlighting the three that were chosen to construct a best-fit line ..............................................47
4-4 Jupiter Inlet ebb tidal shoal depth contours for the year 2000 .................................48
4-5 Jupiter Inlet ebb tidal shoal depth contours for the year 2001 .................................48
4-6 Jupiter Inlet ebb tidal shoal difference in depth contours (2001-2000) used for volume calculations..................................................................................................49
A-1 Profiles for Monument R-75 in Martin County .......................................................58
A-2 Profiles for Monument R-78 in Martin County .......................................................59
ix
A-3 Profiles for Monument R-81 in Martin County .......................................................59
A-4 Profiles for Monument R-84 in Martin County .......................................................60
A-5 Profiles for Monument R-87 in Martin County .......................................................60
A-6 Profiles for Monument R-90 in Martin County .......................................................61
A-7 Profiles for Monument R-93 in Martin County .......................................................61
A-8 Profiles for Monument R-96 in Martin County .......................................................62
A-9 Profiles for Monument R-99 in Martin County .......................................................62
A-10 Profiles for Monument R-102 in Martin County .....................................................63
A-11 Profiles for Monument R-105 in Martin County .....................................................63
A-12 Profiles for Monument R-108 in Martin County .....................................................64
A-13 Profiles for Monument R-111 in Martin County .....................................................64
A-14 Profiles for Monument R-114 in Martin County .....................................................65
A-15 Profiles for Monument R-117 in Martin County .....................................................65
A-16 Profiles for Monument R-120 in Martin County .....................................................66
A-17 Profiles for Monument R-123 in Martin County .....................................................66
A-18 Profiles for Monument R-126 in Martin County .....................................................67
A-19 Profiles for Monument R-1 in Palm Beach County .................................................67
A-20 Profiles for Monument R-3 in Palm Beach County .................................................68
A-21 Profiles for Monument R-6 in Palm Beach County .................................................68
A-22 Profiles for Monument R-9 in Palm Beach County .................................................69
A-23 Profiles for Monument R-12 in Palm Beach County ...............................................69
A-24 Profiles for Monument R-15 in Palm Beach County ...............................................70
A-25 Profiles for Monument R-18 in Palm Beach County ...............................................70
A-26 Profiles for Monument R-21 in Palm Beach County ...............................................71
A-27 Profiles for Monument R-24 in Palm Beach County ...............................................71
x
A-28 Profiles for Monument R-27 in Palm Beach County ...............................................72
A-29 Profiles for Monument R-30 in Palm Beach County ...............................................72
A-30 Profiles for Monument R-33 in Palm Beach County ...............................................73
A-31 Profiles for Monument R-36 in Palm Beach County ...............................................73
A-32 Profiles for Monument R-39 in Palm Beach County ...............................................74
B-1 Profiles for Monument R-10 in Palm Beach County ...............................................75
B-2 Profiles for Monument R-11 in Palm Beach County ...............................................76
B-3 Profiles for Monument R-12 in Palm Beach County ...............................................76
B-4 Profiles for Monument R-13 in Palm Beach County ...............................................77
B-5 Profiles for Monument R-14 in Palm Beach County ...............................................77
B-6 Profiles for Monument R-15 in Palm Beach County ...............................................78
B-7 Profiles for Monument R-16 in Palm Beach County ...............................................78
B-8 Profiles for Monument R-17 in Palm Beach County ...............................................79
B-9 Profiles for Monument R-18 in Palm Beach County ...............................................79
B-10 Profiles for Monument R-19 in Palm Beach County ...............................................80
B-11 Profiles for Monument R-20 in Palm Beach County ...............................................80
B-12 Profiles for Monument R-21 in Palm Beach County ...............................................81
xi
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science
COASTAL SEDIMENT BUDGET FOR JUPITER INLET, FLORIDA
By
Kristen Marie Odroniec
December 2006
Chair: Andrew Kennedy Major: Coastal and Oceanographic Engineering
Three sediment budgets have been developed for Jupiter Inlet, a tidal entrance that
connects the Atlantic Ocean to the Loxahatchee River in southeast Florida. These
budgets cover varying lengths of shoreline updrift and downdrift of the inlet and are
based on two sources of survey data.
Two of the three budgets are based on Florida Department of Environmental
Protection (FDEP) profile surveys covering periods of 1974 to 1986, 1986 to 2002, and
1974 to 2002. The third budget is based on surveys provided by the Jupiter Inlet District
(JID) and covers the period of August 2001 to October 2002. The first budget covers a
shoreline distance of approximately 26 km. The total period of 1974 to 2002 shows a net
accumulation of sediment on the 8.53 km long downdrift beach of 122,600 m3 per year.
Since the shoreline distances north and south of the inlet are not equal, this sediment
budget was believed to be the least accurate of the three. The second budget covers a
shoreline distance of 14.5 km. This budget is believed to be more accurate in the respect
xii
that it covers equal distances of north and south shorelines. It was determined that from
1974 to 2002 there has been a net accumulation of sediment on the 7.25 km long
downdrift beach of 29,500 m3 per year. The third budget covers a shoreline distance of
about 1 km, with nearly equal distances north and south of the inlet. From August 2001
to October 2002, there has been a net accumulation of sediment on the downdrift beach
of 65,600 m3 per year. Due to the variability in the available ebb tidal delta volume data,
two calculations of each of the three sediment budgets were made, one including delta
volume change estimates and one excluding these estimates. The volumes given include
the delta volume change estimates. When these changes are excluded from the
calculations, net accumulated sediment volumes on the downdrift beach are about 2,100
m3 per year higher than those given.
It is recommended that profile survey data be taken yearly for Palm Beach County
Monuments R-3 to R-21, which cover approximately equal shoreline distances updrift
and downdrift of the inlet. Also, the area that the ebb tidal delta covers should be
identified and also surveyed on a yearly basis.
1
CHAPTER 1 INTRODUCTION
1.1 Problem Statement
Tidal inlets provide navigational access from the ocean to lagoons or bays for
commercial and recreational purposes, and they also allow for the necessary exchange of
waters, thus maintaining water quality and promoting life. However, some of the
sediment that is transported along the coast often becomes trapped in the inlet channel
during the flood tide and some is jetted far offshore during the ebb tide rather than being
deposited on the shore as would normally occur in the absence of an inlet. This
interruption in the longshore sediment transport causes shoreline erosion at beaches
adjacent to the inlet (Dean and Dalrymple, 2002).
Many inlets today have maintenance and management plans that were implemented
in order to keep the channel open for navigation as well as to counteract the erosion that
occurs at adjacent beaches. Jupiter Inlet in Florida is one such inlet that has an existing
management plan due to its history of adjacent beach erosion as well as shoaling within
the channel. In this study, the area surrounding this inlet was examined in order to
determine the historical trend of beach and shoreline erosion and to assess the
management plan for its effectiveness in regulating beach erosion.
1.2 Objective and Tasks
The objectives of this study were 1) to develop a sediment budget to analyze the
effects of the beach nourishment that has been carried out adjacent to Jupiter Inlet and 2)
2
to evaluate whether or not that nourishment has been successful in keeping the downdrift
beach sufficiently nourished. The tasks undertaken for this study included:
1. Data compilation of the elements relevant to the sediment (sand) budget, including beach profiles, ebb shoal volumes, dredging volumes and nourishment volumes.
2. Determination of ebb shoal, dredging and nourishment data relevant to the locations and time periods being analyzed.
3. Calculation of the shoreline and volume change rates at the beaches adjacent to Jupiter Inlet.
4. Presentation of sediment budget equation specifically for Jupiter Inlet.
5. Assessment of the beach nourishment’s efficacy after taking all data into consideration in the sediment budget equation.
1.3 Outline of Chapters
Chapter 2 includes site description and a summary of the recent engineering history
of the Jupiter Inlet area as well as a summary of beach profile and sand volume data
compiled for use in the sediment budget analysis. Chapter 3 details methods used to
calculate shoreline and volume changes of the beaches updrift and downdrift of Jupiter
Inlet, describes the limitations of the profile data, and presents the shoreline and beach
volume changes that took place within selected periods of time. The derivation of the
sediment budget equation is given in Chapter 4, followed by the presentation of the
quantities used in the sediment budget and an explanation of the results of the sediment
budget. A summary of the study as well as conclusions and recommendations for further
work are included in Chapter 5.
CHAPTER 2 SITE DESCRIPTION AND DATABASE
2.1 Site Description and Recent History
2.1.1 Site Description
Jupiter Inlet is a natural waterway maintained by the Jupiter Inlet District. The
inlet connects the Loxahatchee River to the Atlantic Ocean, as shown in Figure 2-1.
Figure 2-1
In th
for Jupiter
surroundi
Environm
expanse o
in Martin
second an
N:
e
In
ng
en
f s
Co
aly
km
Jupiter
present
let for
the inl
tal Prot
horelin
unty a
sis cov
1 03
Inlet connecting the Loxahatchee River forks to the Atlantic Ocean
study, three separate sediment budget analyses have been conducted
varying shoreline distances. Figure 2-2 displays the shoreline
et and depicts the locations of the Florida Department of
ection’s (FDEP) range monuments. The first analysis encompasses an
e nearly 26 km in length, with the study beginning at Monument R-75
nd continuing south to Monument R-40 in Palm Beach County. The
ers a 14.5 km distance of shoreline, beginning with Monument R-112
4
in Martin County and ending just past Monument R-36 in Palm Beach County. The final
analysis encompasses a much shorter distance of shoreline of just over 1 km, beginning at
Monument R-10 in Palm Beach County just north of Jupiter Inlet and extending south to
Monument R-15. Jupiter Inlet is located between Monuments R-12 and R-13 in northern
Palm Beach County. It is approximately 26 km south of St. Lucie Inlet and about 19 km
north of Lake Worth Inlet, as shown in Figure 2-3 (Dombrowski and Mehta, 1993).
The Jupiter Inlet system consists of jetties at the north and south banks of the inlet,
a navigational channel and an interior sand trap. The jetties and the location of the sand
trap are displayed in Figure 2-4. Originally in 1922 the north and south jetties were each
120 m long and were built of rock. In 1929 both jetties were structurally strengthened
and extended. The north jetty was extended 60 m and the south jetty 25 m. In 1956 a
sheet-piled jetty 90 m long was constructed 30 m north of the pre-existing jetty. In 1967
the south jetty was extended by 30 m (Dombrowski and Mehta, 1993). Between 1996
and 1998, the seaward end of the south jetty was lengthened by 53 m with a hook in the
southeastward direction (Mehta et al., 2005). Jupiter Inlet is approximately 112 m wide
with a mean depth of 3.9 m at the jetties. Maintained through dredging, the navigational
channel varies in width from about 206 m to 247 m and is also about 3.9 m deep (Patra,
2003). The interior sand trap located approximately 305 m westward of the inlet mouth
is intended to maintain the channel, to nourish the beach downdrift of the inlet by
placement of sand dredged from the trap, and to reduce the influx of sediment into the
Loxahatchee River (Stauble, 1993).
2.1.2 Recent History
Jupiter Inlet has existed naturally for hundreds of years. Originally, it was kept
open by the flow that passed through it from the Loxahatchee River, Jupiter Sound, and
5
Lake Worth Creek, closing intermittently due to natural events such as large storms
(Grella, 1993). In more recent times, from the late 1800’s to the early 1900’s, the inlet
closed more frequently than it had in the past due to the diversion of the natural flow
caused by Lake Worth Inlet to the south and St. Lucie Inlet to the north. The inlet was
occasionally dredged and reopened during this period, but it would again close because of
the decreased flow through it (Dombrowski and Mehta, 1993).
Figure 2-2: FDEP range monuments north and south of Jupiter Inlet
0 1
km
N
6
Figure 2-3: Area map of Jupiter Inlet (Source: Buckingham, 1984, p. 3)
Figure 2-4: Photograph of Jupiter Inlet showing jetties and approximate location
trap
Sand Trap Jetties
N
of sand
km
10
7
The Jupiter Inlet District (JID) was created in 1921 for the purpose of preserving
and maintaining the inlet and the Loxahatchee River. As mentioned, the first jetties were
built in 1922 and extended in 1929. However, the inlet closed again despite these
stabilization efforts (Grella, 1993). To keep the inlet open for navigation, periodic
dredging of a sand trap to a depth of approximately 6 m below mean water level was
implemented in 1947. Since that time the inlet has remained permanently open due to
periodic dredging and maintenance of jetties. Since then, the jetties have been modified
as mentioned, and the sand trap has been enlarged in order to reduce the entrance of
littoral sediment into the inlet and to lessen the deposition of sediment further upstream
of the trap (Mehta et al., 2005).
2.3 Beach Profile Data
Two sources of data have been used to develop the three sediment budgets. The
beach profile data used to conduct the analyses described in this report as the “FDEP
Sediment Budget” were obtained from the Bureau of Beaches and Coastal Systems of the
FDEP. Six sets of surveys consisting of beach profile data were obtained for Martin
County and Palm Beach County. Three surveys within a period of nearly 30 years were
found for each county. Ideally for this type of study the years in which the surveys were
taken for each county would coincide, but matching survey dates were not available for
Martin and Palm Beach Counties. The surveys that were found to be closest in dates
were a 1976 survey for Martin County and a 1974 survey for Palm Beach County, a 1982
survey for Martin County and a 1990 survey for Palm Beach County, and a 2002 survey
for Martin County and a 2001 survey for Palm Beach County. Table 2-1 lists the survey
dates for each county as well as the beach profile type for each survey.
8
Table 2-1: Beach profile data for Martin and Palm Beach Counties County Survey Date Profile Type
1976 Wading profiles every monument; long profiles every third monument
1982 Wading profiles every monument; long profiles every third monument
Martin
2002 Wading and long profiles every monument 1974 Wading profiles every monument;
long profiles every third monument 1990 Wading and long profiles every monument Palm Beach
2001 Wading and long profiles every monument
A wading profile consists of distance and elevation measurements of the dry beach
and includes measurements as far offshore as can be reached by wading or swimming,
which typically reaches approximately 1.5 m of water depth. A long profile is taken by a
surveying vessel and consists of the offshore distance and depth measurements that
cannot be reached by wading or swimming (Dean and Dalrymple, 2002). The long
profiles have been plotted for the three survey dates for each county in Appendix A, from
Monument R-75 in Martin County to Monument R-39 in Palm Beach County.
The sediment budget analysis presented as the “JID Sediment Budget” uses beach
profile data obtained from the Jupiter Inlet District (JID). The profile data obtained from
JID were taken by Lidberg Land Surveying of Jupiter, Florida. Nine surveys were
available for the JID sediment budget analysis. The first five were taken in May 1995,
November 1995, May 1996, November 1996 and March 1997. These include Palm
Beach County Monuments R-13 to R-17, which are south of Jupiter Inlet. The next three
were taken in August 2001, June 2002 and October 2002 and include Monuments R-10
through R-21 in Palm Beach County. The last survey was taken in April 2004 and
includes Monuments R-13 through R-17 in Palm Beach County, south of the inlet. The
beach profiles based on the JID profile data have been plotted in Appendix B.
9
2.4 Ebb Shoal Volume Data
Availability of Jupiter Inlet’s ebb shoal volume measurements was limited. One
record (Dombrowski, 1994) found contained eleven volume estimates taken in various
years from 1883 to 1993. These volume measurements of the ebb shoal are presented in
Table 2-2.
Table 2-2: Jupiter Inlet ebb shoal volumes (Source: Dombrowski, 1994)
Year Volume (m3)
1883 690,000 1947 0 (inlet closed) 1957 380,000 1967 760,000 1978 310,000 1979 680,000 1980 310,000 1981 230,000 1986 690,000 1993 740,000 1993 1,530,000
A second source of ebb shoal volume data was found on the Palm Beach County
Department of Environmental Resources Management website. This source contained
survey data taken of the Jupiter Inlet ebb tidal shoal for the years 2000 and 2001. Based
on these surveys, volume changes were estimated between the two years.
2.5 Dredging Data
Jupiter Inlet has an extensive history of dredging. Even in the early 1900’s the inlet
was dredged simply to keep it open. As mentioned, since then, periodic dredging has
been implemented with the creation of the sand trap. For the time period covered in the
sediment budget analyses, the material dredged from the inlet channel and the trap has
been placed on the beach downdrift of Jupiter Inlet as nourishment. Volumes dredged
from the channel and the trap between 1974 and 2004 are presented in Table 2-3. The
10
data were obtained from Michael Grella of JID (personal communication, March 20,
2006). The dredged sediment volumes between 1974 and 2001 within the limits of the
sediment budget for Palm Beach County for the FDEP budget have an annual average
value of approximately 34,800 m3 over that total period. The dredged volumes in 2001
and 2002 within the limits of the sediment budget using the JID beach profiles have an
annual average of about 48,500 m3.
Table 2-3: Jupiter Inlet and interior sand trap dredging volumes Year Dredged Volume
(m3) 1975 75,003 1977 68,733 1979 71,104 1981 57,342 1983 45,873 1985 58,106 1986 50,078 1988 52,984 1990 64,987 1991 43,466 1993 47,030 1994 54,681 1995 55,048 1996 24,114 1998 64,987 2000 42,968 2001 63,382 2002 33,640 2004 43,580
2.6 Beach Nourishment Data
2.6.1 Downdrift Beach Nourishment Volumes
Records of downdrift nourishment events are shown in Table 2-4. The data were
obtained from Michael Grella of JID (personal communication, March 20, 2006), from
the Beach Erosion Control Project Monitoring Database Information System maintained
by the Beaches & Shores Resource Center of the Florida State University, Tallahassee
11
and from a report prepared by Taylor Engineering for Palm Beach County (Albada and
Craig, 2006). The volumes of sediment dredged from the inlet channel and the sand trap,
as shown previously in Table 2-3, are taken to be equal to the volumes of sediment
placed on the beach from the dredging, and therefore are included in the total
nourishment volumes shown in Table 2-4.
The Jupiter Inlet Management Plan, approved by JID in 1992, adopted 46,000 m3
as the minimum sand volume to be placed on the downdrift beach annually (Grella,
1993). Prior to that plan, a section of the beach about 244 m in length just south of the
jetty was used for the placement of nourishment. In order to increase the retention time
of the same volume of sand, this length of beach was doubled to approximately 488 m as
shown in Figure 2-5 (Mehta et al., 2005).
The two key sources of sediment used for beach nourishment downdrift of Jupiter
Inlet are the sand trap and the Intracoastal Waterway, as shown in Figure 2-6. The sand
stored in the sand trap is dredged nearly every year. Also, excess sand is dredged from
the Intracoastal Waterway by the U. S. Army Corps of Engineers as well as the Florida
Inland Navigation District (FIND), and a portion of the dredged sediment is placed on the
downdrift beach. The recommended plan for the nourishment of the beach is that the
dredging of the sand trap be completed before the end of April each year and placed on
the beach. If this volume is insufficient at that time, then dredging should be conducted
in November instead. It has also been recommended that the Intracoastal Waterway be
dredged and the sediment placed on the downdrift beach in April if the sand trap has been
dredged in November, or in November if the sand trap has been dredged in April (Grella,
1993).
12
Table 2-4: Jupiter Inlet downdrift beach nourishment volumes Year Time of Year of
Nourishment (If Available)
Total Nourishment
Volume (m3)
Approximate Placement of Nourishment
Source(s) of Sediment
1975 192,744 Monument R-13 to R-14 Inlet/Sand Trap, Intracoastal Waterway
1977 68,733 Monument R-13 to R-14 Inlet/Sand Trap 1979 161,933 Monument R-13 to R-14 Inlet/Sand Trap,
Intracoastal Waterway
1981 57,342 Monument R-13 to R-14 Inlet/Sand Trap 1983 45,873 Monument R-13 to R-14 Inlet/Sand Trap 1985 58,106 Monument R-13 to R-14 Inlet/Sand Trap 1986 50,078 Monument R-13 to R-14 Inlet/Sand Trap 1988 132,115 Monument R-13 to R-14 Inlet/Sand Trap,
Intracoastal Waterway
1989 8,792 Monument R-13 to R-14 Intracoastal Waterway
1990 64,987 Monument R-13 to R-14 Inlet/Sand Trap 1991 43,466 Monument R-13 to R-14 Inlet/Sand Trap 1992 106,273 Monument R-13 to R-15 Intracoastal
Waterway 1993 47,030 Monument R-13 to R-15 Inlet/Sand Trap 1994 54,681 Monument R-13 to R-15 Inlet/Sand Trap 1995
November 1995 to February 1996
139,530 Monument R-13 to R-15 Inlet/Sand Trap, Intracoastal Waterway
1995
Spring 461,635 Monument R-18 to R-19 (Carlin Park)
Ebb Tidal Delta
1996 24,114 Monument R-13 to R-15 Inlet/Sand Trap 1998 64,987 Monument R-13 to R-15 Inlet/Sand Trap 2000
Contract Award February 2000
70,171 Monument R-13 to R-15 Inlet/Sand Trap, Intracoastal Waterway
2001
Contract Award February 2001
112,948 Monument R-13 to R-15 Inlet/Sand Trap, Intracoastal Waterway
2002
Contract Award February 2002
33,640 Monument R-13 to R-15 Inlet/Sand Trap
2002
December 2001 to March 2002
477,844 Monument R-18 to R-19 (Carlin Park)
Borrow Area Approx. 3.2 km NE of Jupiter Inlet
2004
January 2004 to March 2004
127,681 Monument R-13 to R-15 Inlet/Sand Trap, Intracoastal Waterway
13
Figure 2-5: Jupiter Inlet Management Plan recommended increase in nourishment beach
length (Source: Grella, 1993, p. 247)
Figure 2-6: Sand trap and Intracoastal Waterway deposition basin from which sediment
is dredged to be used as nourishment (Source: Buckingham, 1984, p. 7)
14
2.6.2 Updrift Beach Nourishment Volumes
Some nourishment events have also occurred on the beach updrift of Jupiter Inlet
for the time period under consideration for the FDEP sediment budget analyses. The
volumes that were placed on the updrift beach are presented in Table 2-5.
Based on Aubrey and Dekimpe, 1988, all except two of the updrift nourishment
events that occurred through 1987 were placed within the bounds of Monument R-75 and
Monument R-111 of Martin County. The first 1983 nourishment as well as the 1986
nourishment are known to have been placed just north of Jupiter Inlet in Palm Beach
County, but the exact locations are uncertain. From the records obtained from the
Beaches & Shores Resource Center, the 1995/1996 nourishment is known to have been
placed between Monuments R-77 and R-106 of Martin County. A renourishment project
was scheduled for 2001 for Jupiter Island updrift of the inlet, but no indication that the
placement had occurred could be found (Tabar et al., 2002).
Table 2-5: Jupiter Inlet updrift beach nourishment volumes Year Nourishment Volume
(m3) Source of Data
1974 741,618 Aubrey and Dekimpe, 1988 1977 366,986 Aubrey and Dekimpe, 1988 1978 649,872 Aubrey and Dekimpe, 1988 1983 108,414 Michael Grella (personal communication,
March 20, 2006) 1983 764,555 Aubrey and Dekimpe, 1988 1986 116,916 Michael Grella (personal communication,
March 20, 2006) 1987 1,704,957 Aubrey and Dekimpe, 1988
1995/1996 1,330,325 Beaches & Shores Resource Center
15
CHAPTER 3 SHORELINE AND BEACH VOLUME CHANGES
3.1 Shoreline and Beach Volume Change Calculation Methods
Two main components that form the basis for the sediment budget for Jupiter Inlet
are the updrift and downdrift beach volume change rates. In order to determine these
rates, two computer programs that were developed by Dr. Robert Dean (personal
communication, June, 2005) for use in an earlier development of a sediment budget for
Sebastian Inlet, also located along the east coast of Florida (Dean, 2005), were modified
and used. The first program inputs beach profile survey data. These surveys were
obtained from the FDEP’s Bureau of Beaches and Coastal Systems database and from
records provided by the Jupiter Inlet District. The program organizes the input data for
plotting profiles at each survey monument and calculates shoreline position changes and
the unit volume (i.e., volume of sediment per unit beach width) changes for the
determined time period based on these survey data. For each monument that has a long
survey profile, the profile area between the water level (NGVD) and the sand surface
from a selected (base line) position on land to the depth of closure is estimated by the
trapezoidal rule. The change in area from one survey date to the next is then calculated in
order to find accretion or erosion that has occurred at the monument in that period. This
area change is then represented as the corresponding unit volume change for use in the
second program.
The second program analyzes the shoreline position and unit volume change
calculations that are output from the first program, and determines the average shoreline
16
and volumetric changes per year. In order to determine the volumetric change per year,
the unit volume change from an earlier survey date is subtracted from the unit volume
change from a subsequent survey date. The unit volume change is then divided by the
number of years in between the survey dates to obtain the unit volume change rate. In
order to obtain the volume change rates for the intersurvey periods analyzed, the end-area
method is used, which averages the unit volume change rates at each monument, and
multiplies this rate by the distance between each monument. The second program also
allows for the calculation of the volume change rate at user-specified points that need to
be examined closely, for example, at the north and south boundaries of the inlet. From
these two programs, the total volumetric rates of gain or loss of sediment are determined
for the beaches updrift and downdrift of the inlet. These values are then used in the
determination of the sediment budget, as described in Chapter 4.
3.2 Data Limitations and Uncertainties
There are several uncertainties to be aware of when using beach profile survey data
to calculate volumetric changes. As mentioned in Chapter 2, beach profile measurements
are taken using two surveying processes, the first being the wading survey, and the
second being the boat survey. The wading portion of the survey is conducted by a survey
crew which uses “standard land surveying equipment” to determine the elevations of the
dry beach, and as far offshore as is possible to reach by wading or swimming, typically
up to about 1.5 m of water depth. Usually, a surveying vessel is used to obtain the
offshore portion of the survey. This vessel commonly has a fathometer and a coordinate
positioning system onboard so that the vessel’s position can be correlated with depth
measurements (Dean and Dalrymple, 2002). Early surveys, however, did not have the
same level of technology that is used now, especially for the offshore portion of the
17
survey. Generally, vessels had to stay on the profile line visually by using the range
poles, so errors were more prevalent in the offshore depth measurements.
3.2.1 Data Uncertainties
Occasionally, there are discrepancies other than measurement errors in the beach
profile survey data. For example, in the survey made in 1976 in Martin County,
monument coordinates were missing for Monument R-84. It was documented in the
FDEP database that the monument had been relocated after the 1976 survey and before
the 1982 survey, so using the coordinates of Monument R-84 from the most recent
survey, which is a common way to correct such a data omission, would have been
inaccurate. Therefore, aerial photographs taken in 1972 and checked in 1975 for
accuracy were inspected, and distances were scaled from Monuments R-83 to R-84 and
from R-84 to R-85. Based on these distances, and on the coordinates of Monuments R-
83 and R-85 documented in the 1976 survey, coordinates for Monument R-84 were
obtained by interpolation. This seemed the most reliable method because of the
proximity in time between the aerials and the survey, and also because it took into
account an estimate of the distance between the monuments, rather than assuming that the
monuments were evenly spaced.
An additional uncertainty occurred in the 1982 survey at Monument R-105 of
Martin County. As mentioned, the early surveys only had long profiles recorded for
every third monument; therefore R-105 should have had long profile measurements for
each survey date. However, in 1982 the measurements were only taken to an offshore
distance of about 45.7 m, with a corresponding maximum depth of -1.6 m. Because the
depth of closure (which is the offshore limit of a volume calculation) was not reached in
the measurements, a unit volume change could not be calculated at this location. Thus,
18
for the periods from 1976 to 1982 and from 1982 to 2002 in Martin County, the beach
volume change rates had to be estimated based on unit volume changes at Monuments R-
102 and R-108 and averaged over the distance between these two monuments, which is a
longer distance than the usual every third monument distance that was normally used for
the other early survey calculations.
3.2.2 Corrections for Non-Closure of Profiles
The depth of closure is a depth at which all beach profiles from any given time
normally converge (and do not diverge significantly again beyond this depth), as
exemplified in Figure 3-1 (Dean and Dalrymple, 2002). For the calculations made in the
previously mentioned programs, the seaward distance corresponding to the depth of
closure from the shoreline was used as a limit for the volume calculations. It can be seen
from the beach profiles shown in Appendices A and B that there is non-closure of many
of the profiles. These data suggest that there was probably some error in the 1976 and
1982 surveys from Martin County, and the 1974 survey from Palm Beach County.
Figure 3-1: Schematic diagram defining depth of closure, where all offshore profiles converge to a certain depth
Local depth of closure
Shoreline
19
Because of the lack of obvious closure depth in the Martin County profiles, and
questionable closure depth in the Palm Beach County profiles, a method other than visual
inspection had to be used to determine a mean closure depth for each county. The
standard deviation of the depths at every monument was calculated separately at the
shoreline and at every 25 m distance offshore for each county. The depth of closure was
chosen at the point where the standard deviation was the least. These closure depths were
-3.66 m at a 350 m distance from the shoreline in Martin County, and -3.11 m at a 250 m
distance from the shoreline in Palm Beach County. As described later, sediment volume
analysis was extended by examining the effect of changing (increasing and decreasing)
the depth of closure. This was done in order to make a quantitative assessment of the
error introduced by selecting a particular depth of closure.
3.2.3 Corrections for Monument Relocation
After the 1976 survey for Martin County and the 1974 survey for Palm Beach
County, some of the monuments were relocated by FDEP, including Monument R-84 of
Martin County as mentioned earlier. The first of the two programs used for the beach
volume calculations accounts for monument relocation. It compares the monument
coordinates from survey to survey, and if the coordinates differ, it calculates the distance
between the monument’s old location and its new location. If this distance exceeds 0.031
m, then an appropriate shift is calculated and added algebraically to every distance
measured along the profile of the original monument.
3.3 FDEP Intersurvey Interval: 1974-1986
For the FDEP intersurvey interval of 1974 to 1986, shoreline change data were
available for every monument. However, unit volume change rates for this interval could
only be calculated for every third monument because in the earlier surveys, including the
20
1976 and 1982 surveys for Martin County and the 1974 survey for Palm Beach County,
long beach profiles were taken for only the first monument of a county and for every
third monument thereafter. Therefore, the unit volume change rates could only be found
for the long beach profiles, in which depths and distances were recorded up to the depth
of closure.
3.3.1 Shoreline Changes
Figure 3-2 displays the shoreline change rates for each monument for the period
between the 1976 and 1982 FDEP surveys in Martin County, and between the 1974 and
1990 FDEP surveys in Palm Beach County. The largest rate of accretion of the shoreline
updrift of Jupiter Inlet based on these data is almost 6.25 m per year at Monument R-84
in Martin County, and the largest rate of erosion of the updrift shoreline is nearly 4 m per
year at R-105 in Martin County. The shoreline change rates on the updrift side of the
inlet show accretion as well as erosion, with no obvious mean trend. Downdrift of
Jupiter Inlet, the highest rate of shoreline accretion observed is around 2.4 m per year at
Monuments R-25 and R-26 in Palm Beach County, and the highest rate of shoreline
erosion is just over 2 m per year at R-29 in Palm Beach County. The shoreline change
downdrift of the inlet for this time period tends to show trends of accretion with smaller
amounts of erosion interspersed.
3.3.2 Sediment Volume Changes
The unit volume change rates for each monument for the period between the 1976
and 1982 FDEP surveys in Martin County and for the 1974 and 1990 FDEP surveys in
Palm Beach County are shown in Figure 3-3. The largest volumetric rate of accretion
occurring updrift of Jupiter Inlet is about 22 m3/m per year at Monument R-84 in Martin
County, and the largest volumetric rate of erosion updrift of the inlet is nearly 30 m3/m
21
per year at R-93 in Martin County. The unit volume change rates on the updrift side of
the inlet show sections of the beach having high accretion as well as high erosion, where
neither accretion nor erosion dominates. Downdrift of the inlet, the highest volumetric
rate of accretion is almost 12 m3/m per year at Monument R-27, and the highest
volumetric rate of erosion is just over 9 m3/m per year at R-36. The unit volume change
rates downdrift of the inlet for this period show a small degree of erosion just past the
inlet, with high accretion just past the erosional stretch. Further downdrift, accretion and
erosion occur without a noticeable trend.
3.4 FDEP Intersurvey Interval: 1986-2002
For the FDEP intersurvey interval of 1986 to 2002, shoreline change data were
available for every monument. For Martin County, unit volume change rates for this
interval could be calculated for only every third monument. Although the second survey
of the interval is from 2002 and contains long beach profile data for every monument, the
first survey of the interval is from 1982, which has long beach profiles for only every
third monument. Therefore, the unit volume change could only be calculated for those
monuments which had long beach profile survey data for both years. For Palm Beach
County, the unit volume changes for this interval were calculated for every monument
because the surveys were from 1990 and 2001, each of which had long beach profile
surveys for every monument.
3.4.1 Shoreline Changes
Figure 3-4 displays the shoreline change rates for each monument for the period
between the 1982 and 2002 FDEP beach profile surveys in Martin County, and between
the 1990 and 2001 FDEP surveys in Palm Beach County. Updrift of Jupiter Inlet, the
highest rate of shoreline accretion is around 3 m per year at Monument R-10 in Palm
22
Beach County, with R-106, R-118, and R-120 having similarly high rates of accretion.
The rate of shoreline erosion is comparatively small and does not even reach 0.5 m per
year at any point. For this period, the shoreline change rate updrift of the inlet tends to be
accretive. On the shoreline downdrift of Jupiter Inlet, the highest rate of accretion is
around 5 m per year at Monument R-36 and nearly the same at R-31 in Palm Beach
County. The highest rate of erosion is around 2.75 m per year at Monuments R-14 and
R-23 in Palm Beach County. Erosion and accretion both occur up to about Monument R-
26, and past this point high accretion occurs.
3.4.2 Sediment Volume Changes
The unit volume change rates for each monument for the period between the 1982
and 2002 FDEP beach profile surveys in Martin County and for 1990 and 2001 in Palm
Beach County are displayed in Figure 3-5. Updrift of Jupiter Inlet, the highest rate of
volumetric accretion is about 20 m3/m per year at Monument R-10 in Palm Beach
County, with the next highest rate at R-120 in Martin County. These two locations
displaying high volumetric accretion rates coincide with two of the locations showing
high shoreline accretion rates. The largest rate of volumetric erosion updrift of the
shoreline occurs at Monument R-12 of Palm Beach County, with a value of about 21.75
m3/m per year. All other volumetric rates of erosion updrift of the inlet are below 8.5
m3/m per year, and few locations display erosion. For this period, similar to the shoreline
change rates updrift of the inlet, the unit volume change rates tend to be accretive.
Downdrift of the inlet, the highest volumetric rate of accretion is nearly 39 m3/m per year
at Monument R-30 in Palm Beach County. The highest volumetric rate of erosion is
nearly 20 m3/m per year at R-13 in Palm Beach County. The unit volume change rate
23
downdrift of the inlet shows drastic erosion immediately downdrift, and then it is mainly
accretive for the rest of the beach length analyzed.
3.5 FDEP Intersurvey Combined Interval: 1974-2002
For the FDEP intersurvey combined interval of 1974 to 2002, the shoreline change
rates were calculated at every monument. However, the unit volume change rates could
be calculated only for every third monument. For Martin County, the first survey for this
interval is from 1976 and contains long beach profile survey data for every third
monument, while the second survey is from 2002 and contains long beach profiles for
every monument. For Palm Beach County, the first survey is from 1974 and contains
long beach profiles for the first monument and every third monument thereafter, and the
second survey is from 2001 and contains long beach profiles for every monument.
Therefore, for both counties, unit volume change rates could be determined only for
every third monument.
3.5.1 Shoreline Changes
Figure 3-6 shows the shoreline change rates for the total time period analyzed, from
1976 to 2002 in Martin County and 1974 to 2001 in Palm Beach County. The shoreline
change rates updrift and downdrift of Jupiter Inlet mainly show trends of accretion for
this time interval. Immediately updrift and downdrift of the inlet, there is more variation,
with erosion at Monuments R-12 and R-13 in Palm Beach County, but overall the
shoreline is seen to have accreted. The highest rate of accretion updrift of the inlet is just
over 2 m per year in Martin County, and the highest rate of erosion updrift is about 1.25
m per year in Palm Beach County at Monument R-12. On the shoreline downdrift of the
inlet, the highest rate of accretion is around 2.5 m per year at Monument R-31, and the
highest rate of erosion is almost 1.4 m per year. Downdrift of the inlet, erosion only
24
occurs over two small stretches of the shoreline, with the rest of the shoreline showing
accretion.
3.5.2 Sediment Volume Changes
The unit volume change rates from 1976 to 2002 in Martin County and from 1974
to 2001 in Palm Beach County are shown in Figure 3-7. Updrift of Jupiter Inlet, there are
large stretches of volumetric accretion with one notable stretch of erosion from about
Monument R-90 to R-105. The largest unit volume change rate showing erosion updrift
of the inlet occurs at Monument R-12 in Palm Beach County and is nearly 14 m3/m per
year. Downdrift of the inlet, there is a small amount of volumetric erosion adjacent to the
inlet, at Monument R-15. Consistent with the trends that were displayed by the shoreline
change rates for this period, the unit volume change rates also display mainly trends of
accretion.
Figure 3-2: Shoreline change rates for the period from 1976 to 1982 in Martin County
and from 1974 to 1990 in Palm Beach County
25
Figure 3-3: Unit volume change rates for the period from 1976 to 1982 in Martin County
and from 1974 to 1990 in Palm Beach County
Figure 3-4: Shoreline change rates for the period from 1982 to 2002 in Martin County
and from 1990 to 2001 in Palm Beach County
26
Figure 3-5: Unit volume change rates for the period from 1982 to 2002 in Martin County
and from 1990 to 2001 in Palm Beach County
Figure 3-6: Shoreline change rates for the combined period from 1976 to 2002 in Martin
County and from 1974 to 2001 in Palm Beach County
27
Figure 3-7: Unit volume change rates for the combined period from 1976 to 2002 in
Martin County and from 1974 to 2001 in Palm Beach County
3.6 Volume Change Sensitivity to Depth of Closure
As mentioned, because the depths of closure were not obvious from the plots of the
beach profiles, the standard deviation method was used to find the mean depth of closure
for each county. Thus it was necessary to check for any significant sources of error
introduced by assuming these values of the depth of closure.
Depths of closure of -3 m and -4 m were used for computing sediment volumes to
compare with those determined using the standard deviation-derived depths of closure.
These two depths were chosen because they bracket the -3.66 m used for Martin County
and the -3.11 m used for Palm Beach County. The -3 m depth represents an 18 %
decrease from the original -3.66 m for Martin County and only a 3.5 % decrease from the
-3.11 m for Palm Beach County. The -4 m depth introduces only a 9.3 % increase for
Martin County and a 28 % increase for Palm Beach County.
28
For all time periods considered, specifically 1976 to 1982, 1982 to 2002 and 1976
to 2002 for Martin County and 1974 to 1990, 1990 to 2001 and 1974 to 2001 for Palm
Beach County, the unit volume change rate differences between the -3 m depth of closure
volumes and the standard deviation-derived depth of closure volumes were considerably
larger in Martin County than in Palm Beach County. This can be attributed to the fact
that the standard deviation-derived depth of closure of -3.11 m for Palm Beach County is
closer to -3 m than the standard deviation depth of -3.66 m for Martin County. For the
first and last time periods considered, which are 1976 to 1982 and 1976 to 2002 for
Martin County and 1974 to 1990 and 1974 to 2001 for Palm Beach County, the unit
volume change rate differences between the -4 m depth of closure volumes and the
standard deviation depth of closure volumes were larger in Palm Beach County than in
Martin County. This is because the standard deviation depth for Martin County is closer
to -4 m than for Palm Beach County. Although the unit volume change rates do differ for
each county when the depths of closure are varied, these differences are minor. This can
be seen in Figures 3-8, 3-9, and 3-10.
3.6.1 Volume Change Sensitivity to Depth of Closure: 1974 to 1986
For the first period, from 1976 to 1982 in Martin County and from 1974 to 1990 in
Palm Beach County, the unit volume change rates corresponding to all depths of closure
are displayed in Figure 3-8. On average, the unit volume change rate differences found
by subtracting the standard deviation depth volumes from the -3 m depth volumes were
approximately 1 m3/m per year and -0.56 m3/m per year, respectively. This means that
within the first period of time considered, the unit volume change rate corresponding to
-3 m is greater than the rate for -3.66 m in Martin County, and the rate for -3 m is less
than the rate for -3.11 m in Palm Beach County. For the same time period, the rate
29
differences between -4 m depth volumes and the standard deviation depth volumes were
on average about -0.68 m3/m per year and 1.68 m3/m per year for Martin County and
Palm Beach County, respectively. Therefore, the unit volume change rate corresponding
to -4 m is less than the rate for -3.66 m in Martin County and greater than the rate for
-3.11 m in Palm Beach County.
Figure 3-8: Unit volume change rates using varying depths of closure for the period from
1976 to 1982 in Martin County and from 1974 to 1990 in Palm Beach County
3.6.2 Volume Change Sensitivity to Depth of Closure: 1986 to 2002
For the second period from 1982 to 2002 in Martin County and from 1990 to 2001
in Palm Beach County, the unit volume change rates for all depths of closure are shown
in Figure 3-9. The unit volume change rate differences found by subtracting the standard
deviation depth volumes from the -3 m depth volumes were on average about 1.3 m3/m
per year and 0.2 m3/m per year, respectively. This means that the rate corresponding to
-3 m is greater than the rate for -3.66 m in Martin County and is also greater than the rate
30
for -3.11 m in Palm Beach County. The rate differences between -4 m depth volumes
and the standard deviation depth volumes were about -0.35 m3/m per year on average for
Martin County and -0.22 m3/m per year on average for Palm Beach County. This means
that rates corresponding to -4 m are less than the rates corresponding to -3.66 m in Martin
County and -3.11 m in Palm Beach County.
Figure 3-9: Unit volume change rates using varying depths of closure for the period from
1982 to 2002 in Martin County and from 1990 to 2001 in Palm Beach County
3.6.3 Volume Change Sensitivity to Depth of Closure: 1974 to 2002
The unit volume change rates for all depths of closure for the combined period
from 1976 to 2002 in Martin County and from 1974 to 2001 in Palm Beach County are
displayed in Figure 3-10. The average unit volume change rate differences found by
subtracting the standard deviation depth volumes from the -3m depth volumes were
around 1.37 m3/m per year and -0.33 m3/m per year for Martin County and Palm Beach
County, respectively. This means that the rate corresponding to -3 m is greater than the
31
rate for -3.66 m in Martin County, and that the rate for -3 m is less than the rate for -3.11
m in Palm Beach County. The unit volume change rate differences between -4 m depth
volumes and the standard deviation depth volumes were on average about -0.48 m3/m per
year for Martin County and 0.60 m3/m per year for Palm Beach County. Therefore, the
unit volume change rates corresponding to -4 m are less than the rates for -3.66 m in
Martin County and more than the rates for -3.11 m in Palm Beach County.
Figure 3-10: Unit volume change rates using varying depths of closure for the combined
period from 1976 to 2002 in Martin County and from 1974 to 2001 in Palm Beach County
3.7 JID Intersurvey Interval: 1995-1996
For the JID intersurvey interval of May 1995 to May 1996, both the shoreline and
the unit volume change rates were calculated just south of Jupiter Inlet for Monuments R-
13 to R-17.
32
3.7.1 Shoreline Changes
The shoreline change rates at each monument are displayed in Figure 3-11 for the
period between the 1995 and 1996 JID surveys in Palm Beach County. The highest
accretion rate seen on this downdrift shoreline is about 9.4 m per year at Monument R-
13. The shoreline continues to show trends of accretion until about R-15, where it begins
to be erosive. This continues to R-17 where the highest rate of erosion of 21.3 m per year
is seen.
3.7.2 Sediment Volume Changes
Figure 3-12 displays the unit volume change rates for each monument for the
period between the 1995 and 1996 JID surveys in Palm Beach County. The shoreline is
seen to accrete from Monument R-13 to R-15. The highest rate of volumetric accretion is
just over 81 m3/m per year occurring at Monument R-13. Past Monument R-15, the
shoreline is erosive, with the highest rate being 178 m3/m per year at Monument R-17.
3.8 JID Intersurvey Interval: 1996-1997
For the JID intersurvey interval of May 1996 to March 1997, both the shoreline and
the unit volume change rates were calculated for Monuments R-13 to R-17, just south of
Jupiter Inlet.
3.8.1 Shoreline Changes
Figure 3-13 displays the shoreline change rates at each monument for the period
between the 1996 and 1997 surveys in Palm Beach County. The highest rate of accretion
is seen to be just over 42 m per year at Monument R-13, just downdrift of the inlet. The
highest rate of erosion is 28.5 m per year at Monument R-15. This stretch of shoreline is
accretive directly downdrift of the inlet, starts to erode near Monument R-15, and then
begins accreting again after Monument R-16.
33
3.8.2 Sediment Volume Changes
The unit volume change rates for each monument for the period between 1996 and
1997 in Palm Beach County are displayed in Figure 3-14. The largest rate of volumetric
accretion occurs at Monument R-13, with a value of 152.3 m3/m per year. The highest
rate of volumetric erosion is 238.3 m3/m per year at Monument R-15. This stretch of
shoreline displays mostly erosion, with accretion occurring only at Monuments R-13 and
R-16.
3.9 JID Intersurvey Combined Interval: 1995-2004
For the JID intersurvey combined interval of May 1995 to April 2004, both the
shoreline and the unit volume change rates were calculated just south of Jupiter Inlet for
Monuments R-13 to R-17.
3.9.1 Shoreline Changes
Figure 3-15 displays the shoreline change rates at each monument for the period
between the 1995 and 2004 JID surveys in Palm Beach County. The only location where
accretion occurs is at Monument R-13 where the rate is about 1.3 m per year. Over the
rest of the length of shoreline there is a slightly erosive trend. The highest rate of erosion
is 5.3 m per year and occurs at Monument R-15.
3.9.2 Sediment Volume Changes
The unit volume change rates from 1995 to 2004 in Palm Beach County are shown
in Figure 3-16. Monument R-13 is the only location showing accretion, with a rate of
about 19 m3/m per year. The rest of the shoreline from Monument R-14 to R-17 shows
erosive trends. The largest rate of volumetric erosion is just over 32 m3/m per year at
Monument R-15.
34
3.10 JID Intersurvey Interval: 2001-2002
Shoreline and unit volume change rates for the JID intersurvey interval of August
2001 to October 2002 were calculated separately from the 1995, 1996, 1997 and 2004
JID data. This is because the 2001 and 2002 surveys included data for Monuments R-10
through R-21 whereas the other surveys included data only for Monuments R-13 to R-17,
south of Jupiter Inlet. For the JID intersurvey interval of August 2001 to October 2002,
both the shoreline and the unit volume change rates were calculated at every monument.
3.10.1 Shoreline Changes
Figure 3-17 displays the shoreline change rates at each monument for the period
between the 2001 and 2002 JID surveys in Palm Beach County. There are only profiles
for three monuments on the updrift side of the inlet, at which the highest rate of accretion
is approximately 3.4 m per year at Monument R-10 and the highest rate of erosion is
nearly 3.75 m per year at R-12. On the shoreline downdrift of the inlet, the highest rate
of accretion is seen to be just over 40 m per year at R-18, whereas the highest rate of
erosion, which is also the only erosion seen over the analyzed distance, is only around 7
m per year at R-20. The downdrift shoreline displays a mainly accretive trend between
2001 and 2002.
3.10.2 Sediment Volume Changes
The unit volume change rates for each monument for the period between the 2001
and 2002 JID beach profile surveys in Palm Beach County are displayed in Figure 3-18.
Updrift of Jupiter Inlet, the highest rate of volumetric accretion is almost 11 m3/m per
year at Monument R-10. The largest rate of volumetric erosion updrift of the inlet occurs
at Monument R-12, with a value of just over 25 m3/m per year. Downdrift of the inlet,
the highest volumetric rate of accretion is nearly 200 m3/m per year at Monument R-18.
35
Erosion on the downdrift side of the inlet is seen at only one monument, R-20, and is
only approximately 3.75 m3/m per year. The unit volume change rate downdrift of the
inlet shows accretion immediately downdrift, and the trend is mainly largely accretive for
the rest of the analyzed beach length as well, with only one monument showing low rates
of erosion.
Figure 3-11: Shoreline change rates for the period from 1995 to 1996 just south of
Jupiter Inlet in Palm Beach County
Figure 3-12: Unit volume change rates for the period from 1995 to 1996 just south of
Jupiter Inlet in Palm Beach County
36
Figure 3-13: Shoreline change rates for the period from 1996 to 1997 just south of
Jupiter Inlet in Palm Beach County
Figure 3-14: Unit volume change rates for the period from 1996 to 1997 just south of
Jupiter Inlet in Palm Beach County
37
Figure 3-15: Shoreline change rates for the combined period from 1995 to 2004 just
south of Jupiter Inlet in Palm Beach County
Figure 3-16: Unit volume change rates for the combined period from 1995 to 2004 just
south of Jupiter Inlet in Palm Beach County
38
Figure 3-17: Shoreline change rates for the period from 2001 to 2002 in Palm Beach
County
Figure 3-18: Unit volume change rates for the period from 2001 to 2002 in Palm Beach
County
39
CHAPTER 4 SEDIMENT BUDGET
4.1 Sediment Budget Methodology
4.1.1 Sediment Budget Equation
This section presents the development of the sediment budget methodology applied
to Jupiter Inlet. The elements included in the budget account for all possibilities of
sediment entering, leaving or being stored within the area of consideration (Rodriguez
and Dean, 2005). For Jupiter Inlet, the volumetric storage elements include the updrift
and downdrift beach systems and the ebb tidal shoal.
To fully illustrate the sediment budget methodology, the rates of volume change on
the updrift and downdrift beaches will be described using all possible volume storage
components as displayed in Figure 4-1. Later, the components that are unimportant to
Jupiter Inlet will be deleted. The rate of volume gain for the updrift beach is described in
Equation (4-1) and the rate of volume gain for the downdrift beach is described in
Equation (4-2) as follows (Dean, 2005):
UBBBUBSTUBEBBUBOSINUB
QQQQQdtdV
,,,, −−−+=⎟⎠⎞
⎜⎝⎛ (4-1)
DRNOURDBBBDBSTDBEBBDBOSOUTDB
QQQQQQQdtdV
++−−−+−=⎟⎠⎞
⎜⎝⎛
,,,, (4-2)
where:
=⎟⎠⎞
⎜⎝⎛
⎟⎠⎞
⎜⎝⎛
DBUB dtdV
dtdV or volumetric rate at which sediment is accumulated in the updrift
or downdrift beaches, respectively,
40
=OUTIN QQ or volumetric rate at which sediment enters the updrift beach or leaves the downdrift beach through littoral transport, respectively, =DBOSUBOS QQ ,, or volumetric rate at which sediment enters the updrift or downdrift
beaches through onshore transport, respectively, =DBEBBUBEBB QQ ,, or volumetric rate at which sediment is accumulated in the ebb tidal shoal from the updrift or downdrift beaches, respectively,
=DBSTUBST QQ ,, or volumetric rate at which sediment is accumulated in the interior sand trap from the updrift or downdrift beaches, respectively,
=DBBBUBBB QQ ,, or volumetric rate at which sediment is accumulated in the back bay region from the updrift or downdrift beaches, respectively,
=NOURQ annual average volumetric nourishment rate of the downdrift beach with sediment provided from outside of the system, and
=DRQ volumetric rate at which sediment is dredged from the interior sand trap.
Combining Equations (4-1) and (4-2) yields the total volumetric rate at which
sediment is stored on the updrift and downdrift beach systems:
DRNOURDBBBUBBBDBSTUBST
DBEBBUBEBBDBOSUBOSOUTINDBUB
QQQQQQ
QQQQQQdtdV
dtdV
++−−−−
−−++−=⎟⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛
,,,,
,,,, (4-3)
The sediment budget is based on the premise that, if the inlet were non-existent, the
processes along the same shoreline distance updrift and downdrift of the inlet would be
identical. Therefore, over the same longshore distances, the beaches updrift and
downdrift should be eroding or accreting at the same rate (Dean, 2005). Theoretically,
with no inlet, the volume changes on equal lengths of updrift and downdrift beaches
would be equal; that is, each would be one half of the total volume change:
( )DBOSUBOSOUTINDBUB
QQQQdtdV
dtdV
,,21
++−=⎟⎠⎞
⎜⎝⎛=⎟
⎠⎞
⎜⎝⎛ (4-4)
However, due to the presence of the inlet and sediment likely being transported into the
inlet channel, not all sediment coming from the updrift side of the inlet is transported to
the beach downdrift of the inlet. Therefore, the difference between the actual volume
41
change rate that has occurred on the downdrift beach and the theoretical volume change
rate of the downdrift beach represents the yearly excess or deficit of nourishment that has
been placed on the downdrift beach, as follows:
( )DBOSUBOSOUTINDB
DIFFERENCE QQQQdtdVQ ,,2
1++−−⎟
⎠⎞
⎜⎝⎛= (4-5)
In this context, a positive QDIFFERENCE value would indicate that there is a quantity of
sediment on the downdrift beach in excess of the amount that would be there in the
absence of the inlet, whereas a negative value would represent a deficit of sediment.
Rearranging equation (4-3), it can be seen that:
( )
⎥⎦
⎤⎢⎣
⎡−⎟
⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛
=++−
NOURBBSTEBBUBDB
DBOSUBOSOUTIN
QdtdV
dtdV
dtdV
dtdV
dtdV
QQQQ
2121
,,
(4-6)
where the following substitutions have been made for the ebb tidal shoal, sand trap, and
back bay elements:
DBBBUBBBBB
DRDBSTUBSTST
DBEBBUBEBBEBB
QQdtdV
QQQdtdV
QQdtdV
,,
,,
,,
+=⎟⎠⎞
⎜⎝⎛
−+=⎟⎠⎞
⎜⎝⎛
+=⎟⎠⎞
⎜⎝⎛
(4-7)
For Jupiter Inlet, the volume changes of the sand trap are approximated as zero
because the sediment that flows into the trap is then dredged and placed within the
system as nourishment on the beach. This means that, on average, accumulation of sand
in the trap is not counted as a loss to the beach. Consequently, the nourishment placed on
the beach from the sand trap is eliminated from the equation as well because only
42
nourishment coming from outside of the system needs to be accounted for. Also, the
backbay element is approximated to be zero because the sediment that flows into, out of,
and is stored in that region is relatively small when compared with the other elements, as
shown in the last row of Table 4-1.
Figure 4-1: Definition diagram displaying Jupiter Inlet along with all possible
components in the sediment budget equation
Records of ebb shoal volumes tend to be limited and their reliability is uncertain.
For this reason the sediment budget will be computed twice, once including the ebb shoal
volume change rate data, and once assuming the ebb shoal volume change rates to be
negligible and therefore excluding them from the equation.
With all the necessary volumetric elements being accounted for including the ebb
shoal volume change rate, the excess (positive QDIFFERENCE value) or deficit (negative
QIN
(dV/dt)UB
(dV/dt)DB
QOUT
QOS,UB
QOS,DB
QEBB,DB
QEBB,UB QST
QNOUR,DB
QNOUR,UB
QBB QDR,OFF
43
QDIFFERENCE value) of nourishment on the downdrift beach of Jupiter Inlet is found based
on the following equation:
⎥⎦
⎤⎢⎣
⎡+⎟
⎠⎞
⎜⎝⎛−⎟
⎠⎞
⎜⎝⎛−⎟
⎠⎞
⎜⎝⎛= NOUR
EBBUBDBDIFFERENCE Q
dtdV
dtdV
dtdVQ
21 (4-8)
It consists of only the volumetric rates of change occurring on the north and south
beaches and in the ebb tidal shoal, as well as the volumetric rate at which nourishment
from outside of the system is placed on the downdrift beach, as shown in Figure 4-2.
The sediment budget equation for Jupiter Inlet in which the ebb shoal volume
change rate is excluded is similar to equation (4-8) with the only difference being that it
excludes the ebb shoal term as follows:
⎥⎦
⎤⎢⎣
⎡+⎟
⎠⎞
⎜⎝⎛−⎟
⎠⎞
⎜⎝⎛= NOUR
UBDBDIFFERENCE Q
dtdV
dtdVQ
21 (4-9)
Table 4-1: Annual mean sand volumetric transport rates in the eastern zone (Source: Patra & Mehta, 2004, p. 11)
Transport from/to Volumetric rate (m3/yr)
Net southward littoral drift 176,000 Entering the channel from littoral drift 46,000 Bar-bypassed around the inlet 128,000 Bypassed by dredging from JIDa trap and ICWW
33,000
Tidally bypassed by entering and then leaving the channel
4,000
Ejected from the channel to offshore by ebb flowb
4,000
Transported offshore from drift by ebb flowb
2,000
Transported to ICWW channels north and south of inlet
4,000
Transported to central embayment 1,000 a Jupiter Inlet District. b Deposited seaward of the littoral system.
44
Figure 4-2: Sediment budget components specific to Jupiter Inlet
4.1.2 Method for Evaluating Sediment Budget
In order to determine the rate of excess or deficit of nourishment being placed on
the beach downdrift of Jupiter Inlet, several steps were followed. First, the beach profile
data were collected from records available on the Florida Department of Environmental
Protection’s website and from records kept by the Jupiter Inlet District. The FDEP data
were analyzed for two different shoreline distances updrift and downdrift of Jupiter Inlet.
The first analysis conducted focused on a distance of 17.4 km north of the inlet,
beginning at Monument R-75 in Martin County, and extending a distance of 8.53 km
south of the inlet, ending at Monument R-40 in Palm Beach County. The second distance
of shoreline that was analyzed covered equal distances of shoreline updrift and downdrift
of the inlet, beginning at Monument R-112 in Martin County, 7.25 km north of the inlet,
(dV/dt)UB
(dV/dt)DB
QEBB,DB
QEBB,UB
QNOUR,DB
45
and ending just past Monument R-36, 7.25 km south of the inlet. For each shoreline
distance analyzed, the FDEP data were examined over three periods. The average
periods were from 1974 to 1986, 1986 to 2002, and 1974 to 2002. These average periods
were determined based on the survey dates that were available for each county,
specifically 1976, 1982 and 2002 for Martin County and 1974, 1990 and 2001 for Palm
Beach County. The JID data were analyzed for a short shoreline distance within Palm
Beach County, beginning at Monument R-10 which is almost 0.56 km north of the inlet,
and ending at R-15 which is approximately 0.50 km south of the inlet. The JID data were
analyzed for one period only, from 2001 to 2002. From these beach profile data, values
of the cumulative volumetric rates of change of sediment being stored on the updrift and
downdrift beaches, UBdt
dV⎟⎠⎞
⎜⎝⎛ and
DBdtdV
⎟⎠⎞
⎜⎝⎛ , respectively, for the defined distances and
time periods were determined as described in Section 3.1.
To calculate the rates of beach nourishment, records of nourishment on the updrift
and downdrift beaches were collected. Because the sediment budget methodology is
focused on analyzing the volumetric rates of change that occur on the downdrift beach
and only accounts for changes that would occur naturally, nourishment on the updrift
beach does not appear in the final sediment budget calculation. Therefore, volumetric
rates of nourishment that had occurred on the beaches updrift of the inlet were subtracted
from the values of volumetric rates of change of sediment stored on the updrift beach.
The records of nourishment on the downdrift beaches were added into the sediment
budget equation as NOURQ in cases where the sediment used for nourishment came from
outside of the beach system. The nourishment from outside of the beach system
consisted mainly of sediment dredged from the Intracoastal Waterway deposition basin.
46
The sediment collected in this basin is believed to have come from sources other than
directly from the inlet, including the channel and the Loxahatchee River system.
Volumes dredged from the JID sand trap and from the ebb tidal delta to be used as
nourishment on the downdrift beach were not included when calculating the final rates of
nourishment in the sediment budget equation because both the sand trap and the delta
were considered to be included in the system.
Records of volume measurements of the ebb tidal shoal are scarce. Only one
compilation of volume measurements was found (Dombrowski, 1994), and this included
measurement estimations only through 1993. The early data show wide variability, and it
is uncertain if this is due to volume changes actually experienced or due to limitations in
the quality of surveys used to obtain the volumes. Three of the measurements relevant to
the study time period were used to construct a best-fit trend line, as shown in Figure 4-3.
The slope of this line displayed a slightly positive volumetric rate of change which was
used as EBBdt
dV⎟⎠⎞
⎜⎝⎛ in the sediment budget equation. Because there were very few reliable
measurements, the ebb tidal shoal volumetric rate of change was assumed to be constant
as obtained from the best-fit line for all periods analyzed in the sediment budget.
The 2000 and 2001 ebb tidal shoal survey data that were taken from the Palm
Beach County Department of Environmental Resources Management website were also
analyzed to find a volumetric rate of change estimate in order to assess the accuracy of
the above estimate. A grid was created in MATLAB, and using measurements from the
surveys, interpolations were made to find depths at each point of the grid. From this
depth-grid, contour plots were created for each year, as shown in Figures 4-4 and 4-5. As
displayed in Figure 4-6, the 2000 depth elevations were then subtracted from the 2001
47
Best-fit line with a slope of 4,285.7
depth elevations in order to find the difference in depths between the two years. As the
exact area of the ebb delta was uncertain, different areas were used to calculate the
volume changes. These areas are shown as boxes in Figure 4-6. Examining the area
contained in the large box, a volume of -52,200 m3 was estimated, implying that the delta
had eroded between 2000 and 2001. Adding together the volumes estimated from the
three smaller boxes, a total volume of +15,208 m3 was estimated, suggesting that the
delta had accreted from 2000 to 2001. Based on these calculations, it is obvious that ebb
tidal shoal volume estimates vary greatly in accordance with the assumption of the area
that is considered to constitute the ebb shoal. This could explain the variability in the
measurements that were found in Dombrowski (1994). It was also the reason that the
sediment budgets were computed both with and without the ebb shoal component.
Jupiter Inlet Ebb Delta Volumes
y = 4285.7x - 8E+06
0
100000
200000
300000
400000
500000
600000
700000
800000
1880 1900 1920 1940 1960 1980 2000
Year
Volu
me
(m^3
)
Figure 4-3: Plot showing measurements of Jupiter Inlet’s ebb delta volumes, highlighting
the three that were chosen to construct a best-fit line
48
Figure 4-4: Jupiter Inlet ebb tidal shoal depth contours for the year 2000
Figure 4-5: Jupiter Inlet ebb tidal shoal depth contours for the year 2001
49
Figure 4-6: Jupiter Inlet ebb tidal shoal difference in depth contours (2001-2000) used
for volume calculations
After deriving all of the volumetric quantities for the necessary sediment budget
components, these quantities were inserted into the sediment budget equations derived in
order to solve for DIFFERENCEQ . The sediment budget components are presented in Tables
4-2, 4-3, and 4-4 with the appropriate quantities inserted where required. As discussed in
Chapter 2, the sediment budgets that were created based on the FDEP profile data are
presented as the “FDEP sediment budgets”, and the sediment budget that was created
using the JID profile data is presented as the “JID sediment budget”.
4.1.3 Effect of Length of Beach on Sediment Budget Calculations
The result of a sediment budget equation may vary depending on the equal lengths
of updrift and downdrift shoreline that are chosen for the analysis. By selecting short
distances of shoreline updrift and downdrift of the inlet, the immediate effects on the
50
downdrift beach caused by the inlet or by recent nourishment events will be seen,
whereas selecting larger distances of shoreline will display if and how the inlet affects the
shoreline and beaches further downdrift. If the sediment budget analysis is carried out
for a distance of shoreline covering downdrift areas of shoreline where erosion is
significant, the result of the sediment budget will likely show a large deficit of sediment
on the downdrift beach if the updrift beach is not experiencing similar erosive trends.
However, if the analysis covers a distance of shoreline that displays differing amounts of
accretion and erosion, the result of the sediment budget will show a surplus or deficit of
sediment on the downdrift beach dependent on whether the accretive or erosive trends
dominate when compared with the updrift beach’s behavior.
Specifically for Jupiter Inlet, if availability of data allow, the minimum length of
beach that should be chosen for analysis is approximately 1 km updrift and downdrift of
the inlet. Since the length of the nourished beach downdrift of the inlet is nearly 0.5 km,
a 1 km shoreline distance should be a sufficient length with which to observe the effects
of the natural spreading of nourishment. Also, this shoreline distance is approximately
four times the length of the jetty that is south of Jupiter Inlet, meaning that the immediate
effects of the inlet and its jetties should be evident within this proximity.
4.2 FDEP Sediment Budget Components
As mentioned previously, two sediment budgets were developed based on the
FDEP beach profile data with the only difference between them being the length of
shoreline included in the analysis. Presented in Table 4-2 are the sediment budget
components for the long shoreline analysis which began at Monument R-75 in Martin
County and extended southward to R-40 in Palm Beach County, covering approximately
26 km of shoreline. Table 4-2 presents the volume changes per year of the beaches
51
downdrift and updrift of Jupiter Inlet, the volumetric rate of change of the ebb tidal shoal,
and the volumetric rate of nourishment placed on the downdrift beach with sediment
from outside of the system. The last two columns display the estimates of the excess or
deficit of nourishment on the downdrift beach on a yearly basis for the given period, with
the first including the ebb shoal volume estimates as in Equation (4-8) and the second
excluding the ebb shoal volume estimates as in Equation (4-9).
Table 4-2: FDEP sediment budget components for long analysis Period (dV/dt)DB
(m3/yr) (dV/dt)UB (m3/yr)
(dV/dt)EBB(m3/yr)
QNOUR (m3/yr)
QDIFFERENCE (Including ebb shoal volume
estimates) (m3/yr)
QDIFFERENCE (Excluding ebb shoal volume
estimates) (m3/yr)
1974-1986
800 -206,700 4,300 18,500 110,900 113,000
1986-2002
152,700 -142,400 4,300 24,300 157,600 159,700
1974-2002
55,300 -173,200 4,300 20,900 122,600 124,700
The second FDEP sediment budget estimate, which is the more accurate of the two
FDEP budgets, is based on the short shoreline analysis which began at Monument R-112
in Martin County and extended southward just past R-36 in Palm Beach County. This
budget is more accurate because it analyzes equal distances of shoreline updrift and
downdrift of the inlet, each 7.25 km in length, which is appropriate according to the basis
of the sediment budget equation. As stated, according to this basis, in the absence of an
inlet, the volume changes over the same distances of shoreline updrift and downdrift
should be equal. The sediment budget components for this analysis are presented in
Table 4-3 in the same order as in Table 4-2.
52
Table 4-3: FDEP sediment budget components for short analysis Period (dV/dt)DB
(m3/yr) (dV/dt)UB (m3/yr)
(dV/dt)EBB(m3/yr)
QNOUR (m3/yr)
QDIFFERENCE (Including ebb shoal volume
estimates) (m3/yr)
QDIFFERENCE (Excluding ebb shoal volume
estimates) (m3/yr)
1974-1986
6,900 1,000 4,300 18,500 10,100 12,200
1986-2002
114,300 20,900 4,300 24,300 56,700 58,900
1974-2002
47,000 4,700 4,300 20,900 29,500 31,600
4.3 JID Sediment Budget Components
The sediment budget based on the data provided by JID is presented in Table 4-4.
This analysis covers a small distance of just over 1 km of shoreline and extends from
Monument R-10 in Palm Beach County, north of the inlet, to R-15, south of the inlet.
Consistent with both of the FDEP analyses, it can be seen that the downdrift beach
volume change rate is positive.
Table 4-4: JID sediment budget components Period (dV/dt)DB
(m3/yr) (dV/dt)UB (m3/yr)
QEBB (m3/yr)
QNOUR (m3/yr)
QDIFFERENCE (Including ebb shoal volume
estimates) (m3/yr)
QDIFFERENCE(Excluding ebb shoal volume
estimates) (m3/yr)
August 2001-October 2002
83,300 -2,600 4,300 49,600 65,600 67,800
4.4 Sediment Budget Results
The equations developed in Section 4.1 provide the basis for the calculation of the
excesses or deficiencies in nourishment on the downdrift beach that prevent the balance
of the sediment budget. If the sediment budget were balanced, the value of QDIFFERENCE
53
would be equal to zero. A QDIFFERENCE value that is negative corresponds to a need for
additional nourishment whereas a value that is positive means that more sediment exists
on the downdrift beach than is needed for the volume changes on the updrift and
downdrift beaches to balance out. According to the short FDEP analysis presented in
Table 4-3, over the long-term period of 1974-2002 an excess of 29,500 m3/yr of sediment
existed on the downdrift beach when the ebb shoal volume estimates were included in the
analysis, and an excess of 31,600 m3/yr existed on the downdrift beach when the ebb
shoal volume estimates were excluded. The two shorter periods included within the total
period also display excess volumes on the downdrift beach and can be seen in the last two
columns of Table 4-3. According to the JID sediment budget analysis presented in Table
4-4, between August 2001 and October 2002 an excess of 65,600 m3/yr of sediment
existed on the downdrift beach when the ebb shoal volume estimates were included in the
analysis, and an excess of 67,800 m3/yr existed on the downdrift beach when the ebb
shoal volume estimates were excluded. These positive quantities support the results of
the FDEP sediment budget estimates. The sediment budget results are summarized in
Table 4-5.
Table 4-5: Short FDEP and JID sediment budget results
Sediment Budget QDIFFERENCE
(Including ebb shoal volume estimates)
(m3/yr)
QDIFFERENCE (Excluding ebb shoal
volume estimates) (m3/yr)
Short FDEP 29,500 31,600 JID 65,600 67,800
54
CHAPTER 5 SUMMARY AND CONCLUSIONS
5.1 Summary
Due to the shoaling of Jupiter Inlet, a tidal entrance along the southeastern coast of
Florida, and the resulting erosion of its adjacent beaches since its stabilization, there has
been an extensive history of dredging of the inlet’s sand trap and nourishment of the
downdrift beach. The implementation of a management plan in 1992 has made specific
criteria to be followed in order to control the shoaling within the inlet and to minimize
surrounding beach erosion. The objective of this study was to develop a sediment budget
taking into account sediment-storing components relevant to Jupiter Inlet in order to
assess the role of downdrift beach nourishment.
In order to perform this study, beach profile data were compiled from two sources,
the Florida Department of Environmental Protection (FDEP) and the Jupiter Inlet District
(JID). Additional data collected for the sediment budgets included dredging,
nourishment and ebb shoal data. The data collected for the FDEP sediment budgets were
examined for three time periods, covering 1974 to 1986, 1986 to 2002 and 1974 to 2002.
The JID survey data that were examined covered time periods of 1995 to 1996, 1996 to
1997, and 1995 to 2004 for Monuments R-13 to R-17 downdrift of the inlet, and a period
of 2001 to 2002 for Monuments R-10 to R-21.
From the beach profile data, shoreline changes and sediment volume changes over
the selected periods of time were calculated for the beaches updrift and downdrift of the
inlet. These calculations took into account profile data uncertainties. Volume change
55
sensitivity to the assumed depths of closure was also examined. The shoreline and
sediment volume changes were calculated for Monuments R-75 to R-127 between 1976
and 1982, 1982 and 2002, and 1976 and 2002 for Martin County and for Monuments R-1
to R-40 between 1974 and 1990, 1990 and 2001, and 1974 and 2001 for Palm Beach
County based on the FDEP profile data. The same sets of calculations were made for
Monuments R-13 to R-17, just downdrift of the inlet between May 1995 and May 1996,
May 1996 and March 1997, and May 1995 and April 2004 and for Monuments R-10 to
R-21 between August 2001 and October 2002 based on the JID profile data.
The basis of the development of the sediment budget was that volume changes over
the same distances of shoreline updrift and downdrift of the inlet would be identical in
the absence of the inlet, and therefore a sediment balance could be created based on this
principle (Dean, 2005).
5.2 Conclusions
1. Based on the shoreline change calculations made from the FDEP profile data, although both shoreline advancement and recession occur, the overall trend is seen to be shoreline advancement downdrift of the inlet.
2. Based on the volume change calculations made from the FDEP profile data, the areas of shoreline displaying volumetric accretion outnumber the areas of shoreline displaying erosion on the beach downdrift of the inlet.
3. The shoreline change rates based on the 1995, 1996, 1997 and 2004 JID profile data taken downdrift of Jupiter Inlet show varying shoreline advancement and recession for the first two intervals (1995-1996 and 1996-1997), but the shoreline changes display recession for the last interval (1995-2004). The shoreline change rates calculated based on the JID profile data between August 2001 and October 2002 display high rates of accretion on the downdrift beach, with erosion occurring only at Monument R-20.
4. The volume change rates based on the 1995, 1996, 1997 and 2004 JID profile data taken downdrift of Jupiter Inlet display mainly volumetric erosion. The volume change rates calculated based on the JID profile data between August 2001 and October 2002 display high rates of accretion on the downdrift beach, with erosion occurring only at Monument R-20.
56
5. There is substantial variability in the results of the sediment budgets depending on whether or not ebb tidal deltas are included in the calculations. When the ebb tidal delta volume changes were excluded from the calculations, the results of all sediment budgets were about 2,100 m3 per year higher than when they were included in the calculations. Also, the variability within the sediment budgets is dependent on which ebb tidal delta volume estimations are assumed to accurate and used in the calculations. As discussed in Chapter 4, depending on the area chosen as the ebb tidal delta, the volume change estimations vary greatly, ranging from high rates of accretion to high rates of erosion.
6. Volume change rates showed only slight sensitivities to the depth of closure chosen for the calculations. The largest sensitivity calculated showed an average difference between rates was 1.68 m3/m per year. Most other calculations showed average differences between rates to be less than 1 m3/m per year. These sensitivities are due to the fact that the distance to the depth of closure alters depending on the depth of closure chosen, and the distance to this depth is the seaward extent of the volume calculations.
7. For the sediment budgets developed, the consistent result was that over all time periods considered there has been an excess amount of sediment existing on the downdrift beach when compared with approximately the same shoreline distance of beach updrift of the inlet. Two of the three sediment budgets that were created are more accurate based on the fact that they analyze nearly equal distances of shoreline updrift and downdrift of the inlet. These two budgets are the short “FDEP sediment budget” and the “JID sediment budget”.
a. When ebb tidal delta volume estimates were excluded from the budget, overall excesses in sediment on the downdrift beach based on the short “FDEP sediment budget” from 1974 to 2002 were 31,600 m3/yr. Based on an average seaward distance of 250 m over a 7.25 km distance of shoreline, this result represents an average accretion rate of just 1.74 cm/yr over the entire area.
b. When ebb tidal delta volume estimates were excluded from the budget, overall excesses in sediment on the downdrift beach based on the “JID sediment budget” from August 2001 to October 2002 were 67,800 m3/yr. Based on an average seaward distance of 250 m over a 500 m distance shoreline, this result represents an average accretion rate of about 0.54 m/yr over the entire area.
c. When ebb tidal delta volume estimates were included in the budget, overall excesses in sediment on the downdrift beach based on the short “FDEP sediment budget” from 1974 to 2002 were 29,500 m3/yr. Based on an average seaward distance of 250 m over a 7.25 km distance of shoreline, this result represents an average accretion rate of only 1.63 cm/yr over the entire area.
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d. When ebb tidal delta volume estimates were included in the budget, overall excesses in sediment on the downdrift beach based on the “JID sediment budget” from August 2001 to October 2002 were 65,600 m3/yr. Based on an average seaward distance of 250 m over a 500 m distance of shoreline, this result represents an average accretion rate of about 0.53 m/yr over the entire area.
5.3 Recommendations for Further Work
In order to increase the accuracy of future sediment budget analyses, the following
recommendations should be considered:
1. Profile survey data should be taken yearly of Monuments R-3 to R-21 so that there are nearly equal shoreline distances updrift and downdrift of Jupiter Inlet. Equal shoreline distances increase sediment budget accuracy. In addition, by having survey data from each year, a more accurate rate of accretion or erosion can be determined. Also, rates that might seem unnaturally high or low could be linked to certain storm events or weather patterns that might go unnoticed when there is a much longer period of time in between surveys.
2. Regular surveys of the ebb tidal delta need to be taken yearly as well, preferably near the same time that the aforesaid profile surveys are taken. The area that the ebb tidal delta covers needs to be defined so that the yearly measurements can be taken in consistent locations, thus minimizing the resulting volume calculation discrepancies.
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APPENDIX A FDEP LONG BEACH PROFILES FOR MARTIN AND PALM BEACH COUNTIES
Figure A-1: Profiles for Monument R-75 in Martin County.
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Figure A-2: Profiles for Monument R-78 in Martin County.
Figure A-3: Profiles for Monument R-81 in Martin County.
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Figure A-4: Profiles for Monument R-84 in Martin County.
Figure A-5: Profiles for Monument R-87 in Martin County.
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Figure A-6: Profiles for Monument R-90 in Martin County.
Figure A-7: Profiles for Monument R-93 in Martin County.
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Figure A-8: Profiles for Monument R-96 in Martin County.
Figure A-9: Profiles for Monument R-99 in Martin County.
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Figure A-10: Profiles for Monument R-102 in Martin County.
Figure A-11: Profiles for Monument R-105 in Martin County.
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Figure A-12: Profiles for Monument R-108 in Martin County.
Figure A-13: Profiles for Monument R-111 in Martin County.
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Figure A-14: Profiles for Monument R-114 in Martin County.
Figure A-15: Profiles for Monument R-117 in Martin County.
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Figure A-16: Profiles for Monument R-120 in Martin County.
Figure A-17: Profiles for Monument R-123 in Martin County.
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Figure A-18: Profiles for Monument R-126 in Martin County.
Figure A-19: Profiles for Monument R-1 in Palm Beach County.
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Figure A-20: Profiles for Monument R-3 in Palm Beach County.
Figure A-21: Profiles for Monument R-6 in Palm Beach County.
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Figure A-22: Profiles for Monument R-9 in Palm Beach County.
Figure A-23: Profiles for Monument R-12 in Palm Beach County.
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Figure A-24: Profiles for Monument R-15 in Palm Beach County.
Figure A-25: Profiles for Monument R-18 in Palm Beach County.
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Figure A-26: Profiles for Monument R-21 in Palm Beach County.
Figure A-27: Profiles for Monument R-24 in Palm Beach County.
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Figure A-28: Profiles for Monument R-27 in Palm Beach County.
Figure A-29: Profiles for Monument R-30 in Palm Beach County.
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Figure A-30: Profiles for Monument R-33 in Palm Beach County.
Figure A-31: Profiles for Monument R-36 in Palm Beach County.
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Figure A-32: Profiles for Monument R-39 in Palm Beach County.
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APPENDIX B JID BEACH PROFILES FOR PALM BEACH COUNTY
Figure B-1: Profiles for Monument R-10 in Palm Beach County.
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Figure B-2: Profiles for Monument R-11 in Palm Beach County.
Figure B-3: Profiles for Monument R-12 in Palm Beach County.
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Figure B-4: Profiles for Monument R-13 in Palm Beach County.
Figure B-5: Profiles for Monument R-14 in Palm Beach County.
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Figure B-6: Profiles for Monument R-15 in Palm Beach County.
Figure B-7: Profiles for Monument R-16 in Palm Beach County.
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Figure B-8: Profiles for Monument R-17 in Palm Beach County.
Figure B-9: Profiles for Monument R-18 in Palm Beach County.
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Figure B-10: Profiles for Monument R-19 in Palm Beach County.
Figure B-11: Profiles for Monument R-20 in Palm Beach County.
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Figure B-12: Profiles for Monument R-21 in Palm Beach County.
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APPENDIX C STORMS NEAR JUPITER INLET, FLORIDA
Table C-1 contains storms that occurred within a vicinity of approximately 150 km
of Jupiter Inlet between 1974 and 2004. The storm data was obtained from the National
Oceanic and Atmospheric Administration (NOAA) website. The shoreline and volume
changes that were calculated from the profile survey data and presented in Chapter 3
showed no effects of these storms because the dates in which the storms occurred did not
correspond with the dates in which the surveys were taken. If survey data were available
from the same years that the storms occurred, then it is possible that the effects of the
storms would be noticeable in the shoreline and volume change calculations.
Table C-1: Storms occurring within 150 km of Jupiter Inlet Year Storm Name Storm Classification 1976 Dottie Tropical Storm 1979 David Hurricane 1983 Barry Hurricane 1984 Diana Hurricane 1984 Isidore Tropical Storm 1985 Bob Tropical Storm 1987 Floyd Hurricane 1988 Chris Tropical Storm 1988 Keith Tropical Storm 1991 Ana Tropical Storm 1992 Andrew Hurricane 1994 Gordon Hurricane 1995 Erin Hurricane 1995 Jerry Tropical Storm 1999 Harvey Tropical Storm 1999 Irene Hurricane 2004 Charley Hurricane 2004 Frances Hurricane 2004 Jeanne Hurricane
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LIST OF REFERENCES
ALBADA, E., and CRAIG, K., 2006. Jupiter/Carlin shore protection project, Palm Beach County, Florida 24 month monitoring report. Report for Palm Beach County, Florida.
AUBREY, D.G., and DEKIMPE, N.M., 1988. Performance of beach nourishment at Jupiter Island, Florida. Proceedings of the Beach Preservation Technology ’88 Conference, L.S. Tait (ed.), Florida Shore and Beach Preservation Association, Tallahassee, Florida, 409-420.
BUCKINGHAM, W. T., 1984. Coastal engineering investigation at Jupiter Inlet, Florida. MS thesis. Coastal and Oceanographic Engineering Department, University of Florida, Gainesville, Florida, 228p.
DEAN, R.G., 2005. Analysis of the effect of Sebastian Inlet on adjacent beach systems using DEP surveys and coastal engineering principles. UFL/COEL-2005/003, Civil and Coastal Engineering Department, University of Florida, Gainesville, Florida, 22p, plus appendices.
DEAN, R.G., and DALRYMPLE, R.A., 2002. Coastal Processes with Engineering Applications. Cambridge: Cambridge University Press.
DOMBROWSKI, M.R., 1994. Ebb tidal delta evolution and navigability in the vicinity of coastal inlets. MS thesis. Coastal and Oceanographic Engineering Department, University of Florida, Gainesville, Florida, 95p.
DOMBROWSKI, M.R., and MEHTA, A.J., 1993. Inlets and management practices: southeast coast of Florida. Journal of Coastal Research, Special Issue18, A.J. Mehta (ed.), The Coastal Education and Research Foundation, 29-57.
GRELLA, M. J., 1993. Development of management policy at Jupiter Inlet, Florida: An integration of technical analyses and policy constraints. Journal of Coastal Research, Special Issue 18, A.J. Mehta (ed.), The Coastal Education and Research Foundation, 239-256.
MEHTA, A.J.; GRELLA, M.J.; GANJU, N.K.; and PARAMYGIN, V.A., 2005. Sediment management in estuaries: The Loxahatchee, Florida. Port and Coastal Engineering, P. Bruun (ed.), The Coastal Education and Research Foundation, West Palm Beach, Florida, 276-303.
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PATRA, R.R., 2003. Sediment management in low energy estuaries: The Loxahatchee, Florida. MS thesis. Civil and Coastal Engineering Department, University of Florida, Gainesville, Florida, 116p.
PATRA, R.R., and MEHTA, A.J., 2004. Sedimentation issues in low-energy estuaries: The Loxahatchee, Florida. UFL/COEL-2004/002, Civil and Coastal Engineering Department, University of Florida, Gainesville, Florida, 40p.
RODRIGUEZ, E., and DEAN, R.G., 2005. Sediment budget analysis and management strategy for Fort Pierce Inlet, Florida. UFL/COEL-2005/004, Civil and Coastal Engineering Department, University of Florida, Gainesville, Florida, 103p, plus appendices.
STAUBLE, D.K., 1993. An overview of southeast Florida inlet morphodynamics. Journal of Coastal Research, Special Issue 18, A.J. Mehta (ed.), The Coastal Education and Research Foundation, 1-27.
TABAR, J.R.; UTKU, M.; and SPURGEON, J.R., 2002. Town of Jupiter Island, Florida, beach renourishment project performance evaluation. Proceedings 2002 National Conference on Beach Preservation Technology, L. Tait (ed.), Florida Shore and Beach Preservation Association, Tallahassee, Florida, 71-89.
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BIOGRAPHICAL SKETCH
Kristen Marie Odroniec was born in Michigan in 1982 to Karen and Stan Odroniec.
When she was ten years old, the author’s family moved to Florida, where she developed
an interest in the nearby beach and coastline. Upon completion of high school in 2000,
she moved to Gainesville, where she pursued a Bachelor of Science degree in civil
engineering at the University of Florida. Kristen graduated in December 2004, and she
entered the Coastal and Oceanographic Engineering Program at the University of Florida
in January of 2005. After obtaining her Master of Science degree in coastal engineering,
Kristen plans to join the industry as a coastal engineer.
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