coastal sediment budget for jupiter inlet, floridaufdcimages.uflib.ufl.edu › uf › e0 › 01 ›...

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.

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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

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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


ix








A-10 Profiles for Monument R-102 in Martin County .....................................................63









A-19 Profiles for Monument R-1 in Palm Beach County .................................................67




A-23 Profiles for Monument R-12 in Palm Beach County ...............................................69





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B-1 Profiles for Monument R-10 in Palm Beach County ...............................................75












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

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unty a

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1 0
3

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


2001



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


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.


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.



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.


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.


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


Figure 3-4: Shoreline change rates for the period from 1982 to 2002 in Martin County


26

Figure 3-5: Unit volume change rates for the period from 1982 to 2002 in Martin 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


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


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


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.


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.


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.


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


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.



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.


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


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.



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.



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


36

Figure 3-13: Shoreline change rates for the period from 1996 to 1997 just south of


Figure 3-14: Unit volume change rates for the period from 1996 to 1997 just south of


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


(dV/dt)EBB(m3/yr)

QNOUR (m3/yr)


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


QEBB (m3/yr)

QNOUR (m3/yr)


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.

57

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.

58

APPENDIX A FDEP LONG BEACH PROFILES FOR MARTIN AND PALM BEACH COUNTIES

Figure A-1: Profiles for Monument R-75 in Martin County.

59



60



61



62



63



64



65



66



67


Figure A-19: Profiles for Monument R-1 in Palm Beach County.

68



69



70



71



72



73



74


75

APPENDIX B JID BEACH PROFILES FOR PALM BEACH COUNTY

Figure B-1: Profiles for Monument R-10 in Palm Beach County.

76



77



78



79



80



81


82

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

83

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.

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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.

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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.

coastal sediment budget for jupiter inlet, floridaufdcimages.uflib.ufl.edu › uf › e0 › 01 ›...

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