• TABLE OF CONTENTS
HIDE
 Front Cover
 Title Page
 Acknowledgement
 Table of Contents
 List of Figures
 List of Tables
 Abstract
 Introduction
 Approach
 Methodology
 Project application and result...
 Conclusions
 Bibliography
 Biographical sketch






Group Title: UFL/COEL (University of Florida. Coastal and Oceanographic Engineering Laboratory) ; 89/008
Title: Performance prediction of beach nourishment projects
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Permanent Link: http://ufdc.ufl.edu/UF00076145/00001
 Material Information
Title: Performance prediction of beach nourishment projects
Series Title: UFLCOEL
Physical Description: ix, 93 leaves : ill. ; 28 cm.
Language: English
Creator: Phlegar, W. Samuel, 1961-
University of Florida -- Coastal and Oceanographic Engineering Laboratory
Publication Date: 1989
 Subjects
Subject: Shore protection -- Florida   ( lcsh )
Coast changes -- Florida   ( lcsh )
Coastal and Oceanographic Engineering thesis M.S
Coastal and Oceanographic Engineering -- Dissertations, Academic -- UF
Genre: bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis (M.S.)--University of Florida, 1989.
Bibliography: Includes bibliographical references (leaves 90-92).
Statement of Responsibility: by W. Samuel Phlegar III.
General Note: Typescript.
General Note: Vita.
Funding: This publication is being made available as part of the report series written by the faculty, staff, and students of the Coastal and Oceanographic Program of the Department of Civil and Coastal Engineering.
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Bibliographic ID: UF00076145
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 21983253

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Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Acknowledgement
        Acknowledgement
    Table of Contents
        Table of Contents 1
        Table of Contents 2
    List of Figures
        List of Figures 1
        List of Figures 2
    List of Tables
        List of Tables
    Abstract
        Abstract 1
        Abstract 2
    Introduction
        Page 1
        Page 2
        Page 3
    Approach
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
    Methodology
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
    Project application and results
        Introduction
            Page 29
        Delray Beach
            Page 29
            Page 30
            Page 31
            Page 32
            Page 33
        Cape Canaveral
            Page 34
            Page 35
            Page 36
            Page 33
            Page 37
            Page 38
            Page 39
            Page 40
            Page 41
            Page 42
            Page 43
        Indialantic Beach
            Page 44
            Page 45
        Jupiter Island
            Page 45
            Page 46
            Page 47
            Page 48
            Page 49
            Page 50
            Page 51
            Page 52
            Page 53
            Page 54
        Ft. Pierce
            Page 55
            Page 56
            Page 57
        Hillsboro
            Page 58
            Page 57
            Page 59
            Page 60
            Page 61
        Pompano Beach
            Page 62
            Page 63
            Page 64
            Page 65
            Page 66
        Hollywood/Hallandale
            Page 67
            Page 68
            Page 69
            Page 66
            Page 70
            Page 71
            Page 72
        Treasure Island
            Page 73
            Page 74
            Page 75
            Page 76
            Page 77
            Page 72
        Captiva Island
            Page 78
            Page 79
            Page 80
            Page 81
            Page 77
            Page 82
            Page 83
    Conclusions
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
    Bibliography
        Page 90
        Page 91
        Page 92
    Biographical sketch
        Page 93
Full Text




UFL / COEL-89 / 008


PERFORMANCE PREDICTION
OF BEACH NOURISHMENT
PROJECTS









by


W. Samuel Phlegar IlI


1989
























PERFORMANCE PREDICTION OF BEACH NOURISHMENT PROJECTS


By

W. SAMUEL PHLEGAR III




















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


1989


















ACKNOWLEDGEMENTS


To begin, I would like to sincerely thank my advisor and supervisory committee chair-

man, Dr. Robert G. Dean, for his insight, direction, guidance, and support throughout this

project. I consider it a true honor to have worked under his patient leadership. I would also

like to thank Dr. Max Sheppard and Dr. Ashish J. Mehta for their contribution during the

important editing and finalizing stages.

The Florida Sea Grant Program and the National Park Service provided the sponsorship

upon which this research is based and this support is greatly appreciated.

Thanks go to Lillien Pieter for the drafting of many of the figures and for her patience in

times of ultimate crisis. The personal conversations with Kim Beachler of Coastal Planning

and Engineering and detailed reports found in the excellent Coastal Engineering Archives

provided important background information. Also, the work of Don Stauble in the mon-

itoring aspects of coastal projects and the summary of past projects is acknowledged and

appreciated.

Many thanks, and my future, go to Miss Kathy L. Hammock, soon to be Mrs. Kathy

Phlegar, for her smiles, patience, love, and finally for not deciding to purchase a handgun

and end her "headache" during and after the thesis preparation days. I must thank my

parents, Bo and Joanne Phlegar, most of all for their ultimate support throughout my life

and for giving me the wonderful ability to smile and laugh through most situations. If we

couldn't laugh, we would all go insane.

Finally, thanks to those who know who they are: Jimmy B., Wesley, Victim, Easton,

Issac N., Gusty, Aggie Douglas, Peener, Therapy Too, Mr. B., Jeffy, Billy, and B.J.























TABLE OF CONTENTS


ACKNOWLEDGEMENTS .....


LIST OF FIGURES .........


LIST OF TABLES .........


ABSTRACT .............


CHAPTERS


1 INTRODUCTION ........


1.1 Purpose of Study ......


1.2 Project Selection ......


2 APPROACH ...........


2.1 Review of Methodologies .


2.2 Relevant Parameters ...


2.2.1 Introduction ...


2.2.2 Wave Characteristics


2.2.3 Background Erosion


2.2.4 Local Conditions .


3 METHODOLOGY .......


3.1 Governing Equations ..


3.1.1 Continuity Equation


3.1.2 Dynamic Equation


3.1.3 Combined Equation


3.2 Analytic Solution ......


3.3 Numerical Solution . .


S . . . . . ii


. . . .


. . ..





. . ..





. . . .


. . . .


. . . .


. . . .


. . . .


. . . .


. . . .
...o.o













. . . .


. . . .


. . . .
o. o .


....o...o













. o. .










3.4 Wave Parameters ...............

3.5 Remaining Parameter Summary . .

3.5.1 Wave Refraction . . .

3.5.2 Sediment Size . . . .

3.6 Model Summary ...............

4 PROJECT APPLICATION AND RESULTS .

4.1 Introduction ..................

4.2 Application and Results for Each Location.

4.2.1 Delray Beach . . . .

4.2.2 Cape Canaveral . . .

4.2.3 Indialantic Beach . . .

4.2.4 Jupiter Island . . . .

4.2.5 Ft. Pierce ...............

4.2.6 Hillsboro ...............

4.2.7 Pompano Beach . . .

4.2.8 Hollywood/Hallandale . .

4.2.9 Treasure Island . . .

4.2.10 Captiva Island . . .

5 CONCLUSIONS ..................

5.1 Summary of Investigation . . .

5.1.1 Prediction Analysis . . .

5.1.2 Parameter Sensitivity . .

5.1.3 Application Limitations . .

5.1.4 Nourishment Monitoring Importance

5.2 Recommendations for Future Work .....

BIBLIOGRAPHY ...................

BIOGRAPHICAL SKETCH . . . .
















LIST OF FIGURES


2.1 Location of coastal data network stations maintained by the Coastal and
Oceanographic Engineering Department at the University of Florida. 7

2.2 Three possible boundary condition applications: 1) open coastline. 2)
structure on beach with minimal net longshore transport. 3) inlet with
a dominant transport direction . . . . . ... 11

3.1 Profile displacement in response to accretion or erosion . ... 15

3.2 Sketch showing shoreline orientation and parameter explanation . 17

3.3 Shoreline evolution for initially rectangular fill, I = miles, H = 2ft.,
Width = 100ft. (from Dean, 1988) ..................... 19

3.4 Proportion, M(t), of fill remaining within original project limits. .... 19

3.5 Schematic representation of shoreline for numerical application ... 21

3.6 Plot of sediment diameter and the k value (after Dean, 1988) . 27

4.1 Location of beach nourishment projects to be studied. . ... 30

4.2 Delray Beach area and project locations . . . ..... 34

4.3 Delray Beach area background erosion: shoreline change plotted at DNR
monuments for 1945 -1970 .......................... 35

4.4 Delray Beach: model prediction and survey volumes . . ... 36

4.5 Delray Beach: parameter variance plot; contours of variance calculations
X 1010. . . . . . . . . .... 37

4.6 Delray Beach: k parameter variance with constant (h, + B) =24.0 38

4.7 Delray Beach: refraction effects on prediction of evolution ...... .. 39

4.8 Cape Canaveral: project and borrow area locations. (after Stauble,
1985) . . . . . . . . . 42

4.9 Cape Canaveral: survey volumes and resulting model volumetric changes
for two cases of varying transport rate. . . . . ... 43












4.10 Indialantic Beach: project location and borrow site. (after Stauble, 1985) 46

4.11 Indialantic Beach: bar diagram of planform and grid cell network after
fill . . . . .. . . . ... 47

4.12 Indialantic Beach: model and analytical prediction showing survey vol-
um es. ................ ............ ....... .. .. 48

4.13 Indialantic Project: erosion rate sensitivity, +2 to 5 ft/yr. ... 49

4.14 Jupiter Island: project locations for multiple nourishments. (Modified
from Aubrey, 1988) .... .. .................... 52

4.15 Jupiter Island: model volumes and indication of possible survey variance. 53

4.16 Jupiter Island: erosion rate sensitivity, 0 to 8 ft/yr range. . . 54

4.17 Ft. Pierce: project and inlet location . . . . .. 58

4.18 Background erosion rates for St. Lucie County shorelines. .. .. 59

4.19 Ft. Pierce: model predicted volumetric changes . . .... 60

4.20 Hillsboro Beach: nourishment project area . . . ... 63

4.21 Hillsboro Beach: survey volumes and model prediction . ... 64

4.22 Pompano Beach: project locations for 1970 and 1983 beach fills . 67

4.23 Hillsboro Inlet: jetty construction history and impoundment basin loca-
tion . . .. .. . . . ... .. .. 68

4.24 Pompano Beach: model predictions and survey results . ... 69

4.25 Hollywood/Hallandale: project and borrow area locations. .. .. 73

4.26 Hollywood/Hallandale: survey, analytical, and model volume results 74

4.27 Hollywood/Hallandale: sensitivity to background erosion rate, 2 ft/yr
and 4 ft/yr . . . . . . . ... . 75

4.28 Treasure Island: nourishment project areas and proximity to Blind Pass
and John's Pass. ......... ... ................. 78

4.29 Treasure Island: survey volumes and model prediction through a two
year period .. .... .. .. ... .. .. .. ... ..... .. 79

4.30 Captiva Island beach nourishment project and borrow area locations. 82

4.31 Captiva Island Model and Survey Losses . . . . 83














LIST OF TABLES


2.1 "Present" Wave Gage Stations and Locations, Spring 1989 . 6

3.1 Wave Height Information For Cape Canaveral, Indialantic, and Ft. Pierce.
Units of H2 and (H/2)0. are (ft)5/ and ft, respectively. These data
obtained by interpolation from adjacent CDN stations . ... 24

3.2 Wave Height Information For Jupiter Island, Delray Beach, and Hills-
boro Beach. Units of H'-2 and (H/2)o.4 are (ft)5/2 and ft, respectively.
These data obtained by interpolation from adjacent CDN stations 25

3.3 Wave Height Information For Pompano Beach and Hollywood/Hallandale.
Units of H5/2 and (H/2)0.4 are (ft)5/2 and ft, respectively. These data
obtained by interpolation from adjacent CDN stations . ... 25

4.1 Delray Beach Nourishment History . . . ...... 32

4.2 Jupiter Island Nourishment Summary. Multiple Reported Volume Per
Year Signifies Placement in Multiple Segments . . .... 51

4.3 Hillsboro Beach: Percent Remaining of Original Volume . ... 61

4.4 Hillsboro Beach: Cumulative Volumes of Erosion Components . 62

4.5 Hollywood/Hallandale: Profile Volume Changes With Time Between
Survey Events ................... ............ 71

4.6 Cumulative Component Percentage of Total Erosion . . 76

4.7 Captiva Cumulative Volume Change . . . ..... 81

5.1 Sensitivity of k Parameter Compared to Dean Relationship Value, ka 85















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

PERFORMANCE PREDICTION OF BEACH NOURISHMENT PROJECTS

By-

W. SAMUEL PHLEGAR III

August 1989

Chairman: Dr. Robert G. Dean
Major Department: Coastal and Oceanographic Engineering

There is a definite need for improved interpretive and predictive capabilities for the

performance of beach nourishment projects. Currently available analytical and numerical

modeling procedures allow such predictions with one approach based on Pelnard Considere's

theory which linearizes the governing equations. This theory, a combination of a continuity

(sediment conservation) equation and a linearized dynamic (littoral transport) equation,

results in a heat conduction analogy for the evolution of a shoreline planform which is out

of equilibrium. This is a one-line approach with basic assumptions of profile equilibrium

and parallel bottom contours; shoreline changes are thus represented by a single contour

taken here as mean sea level.

Two linearized approaches are utilized to evaluate the performance of a beach nour-

ishment project. An analytical approach presents the proportion of sand remaining in the

region placed after any given time period and is based on an initially rectangular planform.

The second method utilizes a finite difference solution which allows for much greater flex-

ibility in representing actual project conditions at the various locations. The methodology

is illustrated and evaluated by application to a total of ten projects around the State of

Florida. The selection of projects was based on two factors including distribution around

the State and most importantly, adequate monitoring information. Nourishment projects










included here and the respective dates of nourishment are Delray Beach (1973, 1978, 1984),

Jupiter Island (1973, 1974, 1977, 1978, 1983, 1987), Indialantic Beach (1981), and Cap-

tiva Island (1981), Hollywood/Hallandale (1979), Pompano Beach (1983), Ft. Pierce Beach

(1971), Hillsboro (1972), Treasure Island (1969), and Cape Canaveral (1975).

Each of these projects is analyzed with numerical modeling methods, and comparisons

are made with actual measured volumetric changes. Analytical techniques are applied and

compared on certain project locations. Results are encouraging, particularly for projects

with accurate and ample monitoring information. The lack of follow-up information restricts

the application as well as the interpretation on several projects. The need for improvement

in monitoring procedure and archiving of obtained information is paramount for analysis

of predictive capabilities. Sensitivity of the predictive performance is high with sediment

information, ambient erosion rates, and wave characteristics. In light of the limitations

in the methodology introduced, the results reflect an adequate procedure for prediction of

shoreline evolution.
















CHAPTER 1
INTRODUCTION



1.1 Purpose of Study

This thesis applies current capabilities to predict the performance of beach nourishment

projects around the State of Florida. Significant work has been accomplished in analytical

studies and numerical modeling in relation to beach nourishment projects. The focus here

is on the adequacy of predictive capabilities in regard to nourishment and renourishment

efforts based on application to actual projects. Much of the previous work has been based on

Pelnard Considere's theory based on linearization of the governing equations which will be

the general direction taken and foundation upon which the present study is based. Project

performance data have been assembled to serve as a basis for evaluating the analytical and

numerical modeling techniques.

Of the many nourishment projects over the past twenty years, few have been monitored

to a satisfactory level for detailed analysis and evaluation of prediction methodology. How-

ever, the assessment of prediction methods requires adequately detailed comparison over

the years after placement. Projects included in this study have at least a minimum level of

performance information. The actual monitoring results are thus compared to the predicted

performance to provide a measure of our prediction capabilities.

Nourishment is becoming the method of choice in coastal erosion control in Florida.

The Florida Department of Natural Resources (FDNR) shows an accounting of $ 115.6 mil-

lion spent toward nourishment during the period 1965-1984. From 1970 through 1984, there

has been approximately 62 million cubic yards of sand placed on Florida's beaches. FDNR

is currently asking the 1989 Legislature to appropriate $45 million for beach management

projects for 1989-1990 fiscal year alone. Of this, $28 million is for new beach restoration and








2

another $10 million for renourishment. A demonstrated capability to predict adequately

the performance of a potential beach nourishment project would therefore contribute sig-

nificantly to the engineering, economic, and environmental assessment of the project. From

the engineering aspect, the volumetric movement of sand from the project area and the

associated time frames would be understood further. Coastal protection to properties and

structures from the changing sand volumes both within and adjacent to the project area

could be better evaluated. This would also enable more precise decisions concerning re-

nourishment intervals, sand bypassing frequency, and maintenance placement. Sensitivity

to sediment parameters might actually preclude the use of particular borrow sediments and

reduce choices of sediment characteristics. Economically, overfills due to the planning now

employed could be more accurately determined and thus significantly decrease the initial ap-

plication costs. Proper advance planning would improve the economics involved with future

renourishments as well as improve permitting/approvement delays. Finally, improvement in

the understanding of the movement of the nourished material would allow greatly improved

environmental assessment of the project area and adjacent areas.

This study is not intended to provide a highly advanced modeling capability in beach

evolution, albeit a useful and effective one-line model will be discussed and demonstrated.

The goal here is to analyze and assess our abilities to predict the performance of beach

nourishment projects using existing technology. Modeling and applicable research in this

dynamic area is exciting and due to the complex and variable "forces" caused by waves, a

numerical approach is essential to realistic prediction.

1.2 Project Selection

Project sites to be studied were selected from many documented cases around Florida's

coastline. Published information on many projects is severely limited to tabulated results

which are inadequate for evaluation once again reinforcing the need for increased monitoring

information. Thus, projects were chosen based on adequate construction information and

monitoring results.









3
Adequate project information is centered around four specific information areas; con-

struction, sediments, waves, and surveys. Construction placement density in planform is

rarely in the idealized rectangular planform. It is important to represent the actual dis-

tribution of nourishment densities along the shoreline. In general, detail of distribution

of sediments placed is sketchy yet significant to project performance. Beginning and com-

pletion dates, and construction delays, need to be reported and subsequently included in

any analysis. Adequate information on the distribution, sorting, and size characteristics for

both native and borrow sediment is necessary for increased understanding of results and

performance. Wave forces are the key to shoreline change, and the analysis and representa-

tion of the wave climate at an area is very important. Adequate representation of the wave

climate requires proper transformation to the breaking zone. Post project surveys provide

the information to allow comparisons with predictions and need to be adequate in extent,

planform density, and frequency following construction. Profiles should extend seaward to

the limit of sediment motion for accurate volume determinations. The projects chosen vary

greatly in all of these items, and each will be highlighted in its availability or absence.

Projects to be analyzed on the Florida east coast include Delray Beach, Palm Beach

County; Jupiter Island, Martin County; Indialantic Beach, Brevard County; Hillsboro

Beach, Pompano Beach, and Hollywood/Hallandale, Broward County; Cape Canaveral,

Brevard County; and Ft. Pierce,St. Lucie County, and on the Florida west coast: Treasure

Island, Pinellas County; and Captiva Island, Lee County.
















CHAPTER 2
APPROACH



2.1 Review of Methodologies

Both the analytical approach and numerical modeling serve as the theoretical back-

ground for prediction of planform evolution. There are no known solutions of any signifi-

cance to the full equations of sediment transport and continuity. Pelnard Considere (1956)

introduced the one-line theory utilized here in which the basic equations of sediment trans-

port and continuity have been linearized and combined. This is the basic methodology

followed in this study. This theory has been applied and researched extensively since its

introduction and has proven an effective approximation to many shoreline applications.

The basic underlying assumption is one of profile equilibrium and associated constant

beach profile shape. Complex conditions which exist at all locations are approximated and

included in the solutions when possible; however, one-line theory requires some detailed

limitations in application. Many analytical solutions have been developed for the combined

equations, one of which will be highlighted subsequently. The limitations which exist in

the analytical application limit its validity and acceptance in nourishment prediction. On

several of the projects studied, however, the analytical results will be calculated and included

in the performance comparison.

The numerical model basically represents the governing differential equations for shore-

line response by their finite difference approximation. Parameters are adapted from each

location to quantify nourishment attributes. The key here is to obtain realistic parameters

for each specific location and include as many as possible in the numerical application.

The procedure is basically as follows: grid network establishment over the computational

domain, finite difference approximation of the governing differential equation, and solution









5

based on initial and boundary conditions. This equation is then solved repeatedly thereby

advancing the solution forward in time. The "as constructed" project conditions serve as

initial conditions for the computations which are then continued to times of available survey

data used in the comparison.

The combined equations will be solved utilizing an explicit approach, as described

in a subsequent section. The numerical model provides greater flexibility to more truly

represent actual conditions. For example, known background erosion rates and repetitive

and segmented nourishment events can be accounted for appropriately, as well as a more

complete picture of construction and associated planform intricacies.

2.2 Relevant Parameters

2.2.1 Introduction

Relevant parameters unique to particular locations include the depth of limiting motion,

characteristics of native and borrow sediments, wavelength, local boundary conditions, local

initial conditions, and background erosion information as determined by FDNR. Each of

these parameters plays an important role in understanding the problem setting as well as in

application of existing methodology. The approach to quantifying the relevant parameters

is presented in the following paragraphs.

2.2.2 Wave Characteristics

A dominant term in the shoreline evolution is wave height, and any general choice of an

average wave height without regard to season would be inadequate. Waves arriving from

deep water are affected by many factors including refraction, shoaling, reflection, diffrac-

tion, friction effects and others. Topography, currents, and general specific bathymetry

complicate matters as well and all together create a formidable system to model. Shoaling

effects caused by wave propagation into shallow water are included here as well as a limited

treatment of refraction.

The Coastal Data Network (CDN) wave data collected by the University of Florida are

utilized (see Figure 2.1). Currently, eight stations around the coast of Florida table 2.2.2












Table 2.1: "Present" Wave Gage Stations and Locations, Spring 1989

STATION DEPTH(ft) LOCATION
JACKSONVILLE 31.2 30 18' 00" N
81 22' 55" W
MARINELAND 32.8 29 40' 03" N
81 12' 17" W
CAPE CANAVERAL 26.2 28 24' 42" N
nearshoree) 80 34' 36" W
VERO BEACH -. 24.6 27 40' 30" N
80 21' 15" W
WEST PALM BEACH 29.5 26 42' 07" N
80 01' 42" W
MIAMI BEACH 21.3 25 46' 06" N
80 07' 23" W
CLEARWATER 16.4 27 58' 44" N
82 51' 00" W
VENICE 23.6 27 04' 26" N
82 27' 23" W


collect wave data at approximately six hour intervals. Included in this analysis are the

relative depth of the gage, significant wave height, wave period, and percent wave energy

distribution within various period bands. The initial wave information for the various

project locations has been compiled from both CDN data reports and a 25-year nearshore

wave evaluation published by CERC (Thompson, 1977). Currently, over three years of CDN

data are retained on computer files at the University of Florida and are accessed for this

evaluation. The wave data are represented by month, by location, and by spatial interpo-

lation between data measurement stations. The significant wave height measurements are

manipulated to obtain an effective breaking wave height at the shoreline, which serves as an

important factor in the shoreline evolution. The seasonal effects are therefore included due

to the monthly application. Wavelengths are summarily calculated at each of the project

location from the dispersion equation utilizing the measured data. Nothing could substitute

for actual wave data collected at the individual project locations; however, the CDN data

allow actual data in the general vicinity to be interpolated to each site.































\ S/SANTA K I JACKO
ROS A I .
( AL .. ;j ,---. SOs Au St. Mary's Entrance
90 Y, I* *. "I ; 0| \ 1983
"<. ---,Iy! ISON, l "<
I'-- 8E1TY WAKULLA A ; BKEi
!8ULF~ AN L TAYLOR -
sulF FiANK1'UJ i' n "
I I I Marineland 7,

LEVY O1-
GULF -A a

" ICITUS' ,L'K E ,,
cus ', rE ';
A IHERNANDb I '-
I IOCANCEO
/sco i L ----- Cape Kennedy
,-- I OsscEoiA \ 1977
N N I "
Clearwater ,/ u r TNUI Vero Beach
A1978 A* ----i---A RE 1980
9 HI LA- I I LUCIE
VBnic T-'- 07- C MO T-'l
'4 LCLACEYHG '
S1 OKEECOf- --

LLL 'HE NDRIY FLLII iLACHI Palm Beach
S----- 1979
COLL:EI i BHOr.AH

-- *Miami
bnROnt 1977









Figure 2.1: Location of Coastal Data Network Stations maintained by the Coastal and
Oceanographic Engineering Department at the University of Florida.








8

Simply stated, a general effect of wave action on a shoreline is the movement of sedi-

ment. Under circumstances particular to each location, the shoreline profile evolves toward

an equilibrium shape. Under normal conditions, this shape is maintained through recov-

ery processes in response to seasonal effects and storm activity not unusually severe. The

shape is dependent primarily upon the wave climate and sediment particle size. Significant

alterations in these factors force an attempt to reach a new equilibrium profile. When a

nourishment event occurs, the beach is altered and thus set into motion to obtain equi-

librium. This attempt is made in profile as well as the spreading out (diffusion) effects in

the longshore direction. The effects of waves and currents drive the evolution toward the

unaltered "straight" equilibrium shoreline. In the linear interpretation, the resulting plan-

form is symmetric about the center point of the fill. This will be discussed in detail later.

Essentially, the erosional problem after a nourishment event is due to a combination of these

diffusion losses and natural underlying erosion present before the shoreline pertubation.

2.2.3 Background Erosion

An erosional problem is characterized by a background erosion rate; to a first ap-

proximation this erosion component will continue at the same rate superimposed on the

"spreading out" losses due to the nourishment. Historical shoreline change can be caused

by many factors and can also be accelerated or decreased over a period of years. Wave

action is the ultimate cause of shoreline change; however, interaction with coastal struc-

tures, particularly jetties, provide the greatest effects on the Florida east coast. Inlet jetties

and dredged navigational channels cause interruptions to the flow of sediment downdrift.

Therefore, sediment that would have been transferred down the coast is removed from the

sand sharing system. In areas with significant net directional littoral drift, this effect is of

greatest significance. The downdrift shorelines then feel the effects of the volume deficit.

Sea level changes over time will also cause shoreline alterations. A good approximation of

the underlying rate of sand removal from a shoreline is a very important consideration, for

without a background erosion, there would be no need for nourishment. The system con-








9

tinues to respond to the effects of this background rate after the nourishment application.

Thus, the separation of background erosion effects from diffusion effects is a very important

element in complete understanding of the shoreline's response to nourishment.

Historical shoreline positions have been digitized and compiled by FDNR for much of

the coast of Florida. This information has been organized and combined from aerial pho-

tographs, maps and charts, and hydrographic and beach surveys, with information starting

in the mid to late 1800's. Thus a long term background erosion rate or short term, should

a change such as cutting an inlet or installing a coastal structure become involved, may

be obtained. The data are referenced to FDNR monuments and further to State Plane

Coordinates. Ground survey data are provided by FDNR, U.S. Corps of Engineers, U.S.

Coastal and Geodetic Survey, state, county, city agencies, and others.

Seasonal shoreline fluctuations in Florida can be as great as 60 ft., complicating some-

what attempts to analyze the data and select an appropriate background erosion rate.

Recognition of scatter and noise in the reported survey data within the project areas is

important. Seasonal variations in the data may be compounded by unusual conditions

associated with storm events. Other background rates will be referenced and applied to

supplement the compiled data where considered appropriate. With the importance of an

accurate background rate, sensitivity toward this factor is highlighted in many areas where

the historical data are questionable or in contrast to other sources. Accuracy of the FDNR

survey data is reasonable for the ground survey data with plus or minus ten feet the norm,

while the aerial photos introduce a possible error of plus or minus 30 feet. In this light, the

aerial survey data will not be included in determining the shoreline change. A long term

rate is thus extracted from the data taking into account the possible sources of error and

the limitations introduced by shoreline construction at inlets.

2.2.4 Local Conditions

Local conditions in the form of boundary and initial conditions provide the specifics

of the model application. Each segment of coastline around the state of Florida is unique








10

in many ways. Several miles separating two areas can provide different sets of parameter

application including differences in sediment characteristics, background erosion rates, and

coastal structures. Numerical application is a powerful tool in this aspect in comparison to

the analytical approach which is severely limited in its inclusion of many of these factors.

Initial conditions on each project significantly affect the resulting performance with domi-

nant factors including; length, volume, and the subtle effects of construction distribution in

planform.

Boundary conditions provide projects with a certain uniqueness which must be ad-

dressed. The following discussion is based on figure 2.2 illustrating the various boundary

conditions to be handled in the application section. Open coast beaches without structures,

inlets or anomalies are the most adaptable to the basic methodology. The idealized condi-

tion for both numerical and analytical application is a straight shoreline with a rectangular

beach fill extending into the ocean a distance Yo, with longshore length 1. Also in this the-

oretical approach the shoreline is considered to be infinite in length with no interruptions.

This is the idealized case upon which the analytical approximation is based. This is sketched

in case 1 of figure 2.2. Erosion following nourishment in this case is equal to the sum of the

background rate and the effects of planform evolution outside of the project limits. This

case is well understood numerically by easy manipulation of the boundary conditions. The

domain ends are far enough away from the affected area to not "feel" any effects and the

shoreline displacements at the ends are set equal to zero. In reality however, a particular

project may have features which differ substantially from those described above.

Shorelines requiring nourishment are in a state of erosion caused by many factors, both

man made and natural. Also, constructed projects rarely approach the rectangular ex-

tension of beach. The current understanding of model application with regard to certain

boundary conditions is limited. Utilizing a one-line model increases this lack of confidence

in application. The introduction of littoral barriers such as groins, jetties at trained nav-

igational inlets, or sinks such as the end of a barrier island all cause increased challenges










Wave Direction


Wave Direction


F- Jetty


Idealized Limits


Wave Direction




a QBP


Imax


I Project Limits I

a) QBP= 0
b) 0 QBP< 1

Figure 2.2: Three Possible Boundary Condition Applications: 1) Open coastline. 2) Struc-
ture on beach with minimal net longshore transport. 3) Inlet with a dominant transport
direction


'I
Case 1


Imax


Case 2
Case 2


imax


Case 3









12
in interpretation and prediction. However, limited treatment in specific cases proves ade-

quate. Specifically, figure 2.2 illustrates two cases requiring a different approach than the

"ideal" case 1. There are two components of losses in this case, spreading out losses and

interruption of the longshore sediment transport due to the presence of a jetty.

Case 2 is representative of a location without a dominant direction or significant volume

of longshore transport. Transport through the jetty is assumed zero and the fill spreads

in the direction away from the structure. At this end of the computational domain, the

maximum grid cell is placed similarly to case 1, sufficient distance from the nourishment to

assure zero transport into the cell. This results in an effective project length of twice that

of the actual project. This approach will be utilized at Captiva Island and Treasure Island,

both locations on the west coast. These areas are noted for the absence of a dominant

transport direction and less wave intensity.

The third case illustrates the application to locations with natural or mechanical by-

passing. The east coast of Florida is predominantly under the influence of a significant

southerly net direction of sediment transport. The mechanics will be examined in chapter

three, in the section on the numerical solution. The approach however is one of determin-

ing the bypassing quantity of sediment, QBP. A quantity of sediment is drained from the

system and the shoreline approaches a normal angle to the incoming wave angle adjacent

to the jetty. The transport deficit caused by the existence of the jetty forces this angle

immediately downdrift of the downdrift jetty to be parallel to the incoming wave attack.

The sediment erosion is the difference between the net longshore drift for the area minus

the bypassed quantity. Two situations exist in this case. First, a bypass rate of zero indi-

cates a deficit to the system of the entire ambient transport drift. The second option is the

bypassing of a fraction of the nominal transport rate. As 22 approaches unity, the case is

similar to case 2.

Initial conditions must also be prescribed, allowing representation of actual sediment

placement in planform as well as sediment differences between the native sediment and the








13
borrow material. Sediment characteristics are a very important factor in any nourishment

analysis or prediction. Median grain sizes and the sorting through distribution are included

where the information is available. The information for both native sediment and bor-

row material is ultimately important in the resulting performance. Each project requires

thorough analysis in this area, yet the records for most are severely lacking.

Finally, with the large scale of this analysis and the associated lack of highly detailed

project information, it has proven instructive to look at parameter application in both a

prognostic and diagnostic light. Thus, an attempt is made to first, learn from nature the

attributes of the parameters and second, see if we can predict back to quantify an actual

application.

The diagnostic approach will be centered around parameter sensitivity and the attempt

to minimize deviation from the actual results. On the other hand, a prognostic approach is

of value in the planning stage of any future project. Several parameters can be controlled

and optimized while others are completely under nature's control. A more complete under-

standing of the variability due to an individual parameter will enable a more complete and

confident plan for beach nourishment. Site specific local conditions in the form of initial

and boundary conditions are therefore the basis for any approach.

















CHAPTER 3
METHODOLOGY



3.1 Governing Equations

The two governing equations are the sediment transport and continuity equations. The

background of each is essential to the understanding of the subsequent manipulation and

application. As noted before, the theory was introduced in 1956 by Pelnard Considere. The

methodology begins by introduction of the two basic equations of sediment conservation

and sediment transport.

3.1.1 Continuity Equation

The continuity equation is a basic statement of sediment conservation where a gradient

must be manifested by a change in the cross-sectional area of sand in the profile.

aQ aA
a + A= 0 (3.1)

The change in sand area, AA, due to a profile displacement, Ay, active over a vertical

dimension (h, + B) is depicted in figure 3.1. The assumption is therefore, in response to

an accretion or erosion, a change in area is produced by a displaced profile and may be

expressed as:

AA = Ay(h, + B) (3.2)

This simple statement will serve as the first step in the method of calculation of nourishment

volumes, both remaining and placed. This is followed by multiplication by the alongshore

distance of interest. Thus the equation of sediment conservation results in:


ay 1 8Q
S = 0 (3.3)
at (h, + B) 8a
Sediment is therefore conserved through the area of concern.














Ay






-AA


Depth of Closure







Figure 3.1: Profile Displacement In Response to Accretion or Erosion

3.1.2 Dynamic Equation

The second equation is the dynamic or sediment transport equation. Bagnold (1963)

related available power in the surf zone to the total immersed weight transport rate. Intro-

ducing a relationship to the volumetric rate of transport, Q, and solving the relationship

for Q, a sediment transport rate can be defined in terms of the energy flux in the longshore

direction. It can be shown, by inducing breaking conditions of linear wave theory including

utilizing the spilling breaker assumption,


Hb = ihb (3.4)

that the one dimensional transport equation is:


kH/2 j sin 2(P ab)
Q = (3.5)
16(1 p)(s- 1)
where, in reference to figure 3.2,


* = breaking wave criteria constant (0.78)










16
s = p/p,,: P, = mass density of sediment, p, =mass density of water;s=2.65

p = porosity (0.3 0.4)

g =gravity constant (32.2 ft/sec2)

Hb = breaking wave height at shoreline

p = azimuth of outward normal to shoreline

p/ = azimuth of the shoreline's general orientation defined by the baseline

ab = azimuth from which breaking wave originates

k = transport coefficient (depends on sediment size)


3.1.3 Combined Equation

The combination of the continuity and sediment transport equations provide the frame-

work for further solution. First, equation 3.5 is differentiated and the result linearized along

with the equation for p. Assumptions for linearization include: uniform wave height dis-

tribution along the shore, small gradients of the shore planform, 2 and a small wave

approach angle (3 ae).

,r (, ay
8= p tan- ( 2 (3.6)
2 ax 2 ax

which, when combined with equation 3.3, becomes the partial differential equation governing

the planform evolution:
ay 2y
ay G a2 (3.7)
Tt 822
This equation is seen as the typical form of the "heat conduction" equation, and is the

combined linearized equation for which many analytical solutions exist (Larson 1987). The

term G is described as an alongshore diffusivity term and depends strongly on the breaking

wave height,
kH/521/2
G = (3.8)
= (s 1)(1 p)(h. + B)
















N J



0
\k 4-







-Shorel
Reference r'
Base Line


OI
+Qs


Figure 3.2: Sketch showing shoreline orientation and parameter explanation








18
This single term includes several significant parameters including wave height, sediment

characteristics, and closure depth. Resulting evolution is strongly associated with this term

justifying the "alongshore diffusivity" terminology.

3.2 Analytic Solution

One of the most valuable solutions to the diffusion equation in coastal engineering is

that for an initially rectangular nourishment project. The resulting analytic solution for

this case can be expressed with y(x,t) being the displacement offshore and a function of

alongshore distance, x, and time, t:

Yo I 12x\1 ri 22
y(x, t)= erf + 1 -erf (3.9)
2 4-f 14 1 I

Here "erf" denotes the error function which can be found tabulated in standard mathematical

references, (e.g. CRC, 1984), and is defined as:


erf(z) = f exp(-u2)du (3.10)

The term I is the length of the project in the shoreline direction, and Yo is the initial shoreline

displacement resulting from the nourishment extension seaward. The evolution of such an

initial case is shown in Figure 3.3. The following parameter establishes similitude between

two projects.

S((3.11)

Thus two projects with the same parameter shown above, will exhibit similarity in evolution

and the resulting percentage volume changes.

Based on equation 3.7 it is possible to develop an expression representing the proportion

of sand remaining in the location placed, M(t), as:

M = -- (exp -(1/2V/)2- ) + erf (1/2v/t)) (3.12)


From Figure 3.4, proportions of the fill remaining in front of the original location placed can

be established based on the dominant similitude term, equation 3.11. Similarly, a solution














DISTANCE FROM ORIGINAL
SHORELINE, y (ft)


Planform
After 3 Months


7 Years


Pre-Nourished
Shoreline


6 4 2 0 2 4 6 8
ALONGSHORE DISTANCE, X (miles)




Figure 3.3: Shoreline evolution for initially rectangular fill, I = miles, H = 2ft., Width
= 100ft. (from Dean, 1988)


LLu.

O1.0







o"o
z 0



Ow 0
0. 0.


Figure 3.4: Proportion, M(t), of fill remaining within original project limits.


'-. I i i i i I i I I I I I i I i I I i I i i I
t = Time After Placement
G= Alongshore DIffuslvlty Initial
\ Fill
Asymptote Planform -
1 11 =1 I '- -



1 1I- I


IGt/ -e








20

can be developed for the situation of a project located downdrift of a partial or complete

littoral barrier. Several examples of this application exist on Florida's east coast.

1iVG / i \(11,fG-t 1) (1- F)Q,t
M2(t) = (exp + erf 1/vt) (3.13)

The percentage of the longshore transport, Qo, bypassed is F with (0 < F < 1). The

original volume placed is represented by Vo.

3.3 Numerical Solution

Solutions developed numerically allow much greater flexibility in comparison to the

above due to the ability to include numerous process parameters. The numerical solution

is structured with a finite difference representation of equation 3.7. This results in the

following explicit form:

GAt
y+l = y? + Tz- (yi1 2y? + y ) (3.14)

Where the superscripts denote time level (n+1 is the next time step) and the subscripts

represent the grid in the network illustrated in Figure 3.5.

Boundary conditions representing the individual projects are specified and incorporated

into the solution. Introduced in Chapter 2 and illustrated in figure 2.2, the explicit method

of solution utilized in this study allows basically two types of boundary conditions. The

first is where the value of the shoreline at the project ends is specified and either held fixed

or allowed to vary with time in a prescribed manner. As an example, ymaz and yo on

an open coast project without protruberances would be set equal to zero and selected at

sufficiently large distances from the fill that the evolution would not be affected by the zero

flow condition.

Many projects in Florida are, however, affected by the presence of a jetty. When this

condition exists, the flow of sediment is restricted it that particular location and must

be treated accordingly. This second type utilizes the procedure of imposing a sediment

transport rate, Q, at the boundaries. Examples here would be a zero transport due to a

total littoral barrier and a low or "leaky" jetty which allows a certain amount of sediment




















N










Reference Baseline
for Shoreline


Figure 3.5: Schematic representation of shoreline for numerical application.








22
movement through the structure. For purposes of further exploring this boundary condition,

one of the assumptions listed earlier of assuming negligible wave approach angles must be

modified. Also, the approach angle is retained in a sine term and not a cosine term which

would approach unity with small angles. Equation 3.5 and equation 3.8 can be reduced to

sin 2(f ab)
(Q QBP) = G(h. + B) s 2 (3.15)

The left side of equation 3.15 allows the alteration of the sediment deficit due to the amount

bypassed, QBP. Should the approach angle be zero, the equation would reduce to Q equaling

QBP and the approach would be to follow case 2 of figure 2.2. The method followed in

modeling of this case would be to double the computational domain and simply sum over

one half its length. This forces the no transport condition at the jetty, the midway point.

Other physical conditions that could require representation include: groin location, natural

inlets, and ends of a barrier island. Each of these cases will be discussed in detail as the

need arises for their application.

The defense posture of the beach orientation alluded to earlier is simply due to the

shoreline's attempt to reach equilibrium and meet the condition of zero flow through the

jetty. To achieve zero transport, Qo = 0, the sine term must vanish, therefore ab equals f

and the shoreline orientation is parallel to the wave crests or at a ninety degree angle with

the wave rays.

A limitation is noted here due to the neglect of two very important terms, wave diffrac-

tion around the coastal structure and seasonal reversals in dominant wave direction and

associated longshore transport direction. It would be optimal to include procedures for the

diffraction effect as well as the prediction of planform changes due to reversals.

3.4 Wave Parameters

A description of the various wave parameters and associated determination is necessary.

The CDN wave gage network collects data from relatively shallow water submerged gages.

To obtain a wave climate representative of that at the coastline, the following procedure is

used.










23
The equation for conservation of wave energy flux (Dean and Dalrymple, 1985) with

the subscript b denoting breaking depth conditions is

[EC, cos(6 a)] = [ECg cos(p a)b (3.16)

with the energy term defined by
1
E= -pgH2 (3.17)

The flux expression is equated at the breaking depth and at the depth of the CDN

station. Again assuming unity for the cosine terms and applying the shallow water approx-

imation for wave celerity, shown subsequently, as well as the spilling breaker assumption,

equation 3.4, the resulting expression is equation 3.19.

C = vgh (3.18)


H/2- H'CO
H (3.19)

where
C 2kh 1
C = [ 1 + 2kh (3.20)
2 = sinh 2kh
Here, Cg is the group velocity at the offshore reference location. Longuet-Higgons (1952)

showed that waves in nature are represented well by the Rayleigh Probability Distribution.

Equation 3.19 can be rewritten as

H 2= F(T,)H2 (3.21)

where

F(Tn) = C (3.22)

By applying a Rayleigh wave height distribution relationship, the following sequence is
followed for solution of the resulting breaking wave height;

= p(H)F(T,4)HdH (3.23)
00
= F(Tn,) H'p(H)dH (3.24)

= F(T,)H2 (3.25)











Table 3.1: Wave Height Information For Cape Canaveral, Indialantic, and Ft. Pierce. Units
of and (H 2)0.4 are (ft)6/2 and ft, respectively. These data obtained by interpolation
from adjacent CDN stations

MONTH CANAVERAL INDIALANTIC FT. PIERCE
0.5/2 52o. ((/ 52/.4. (0 5/2 0.4
JAN 5.97 2.04 8.95 2.40 12.51 2.75
FEB 4.96 1.90 7.85 2.28 9.77 2.49
MAR 10.59 2.57 14.62 2.92 16.80 3.09
APR 3.66 1.68 4.84 1.88 5.91 2.04
MAY 4.32 1.80 6.14 2.07 8.61 2.37
JUN 2.52 1.45 2.96 1.54 3.37 1.63
JUL 1.44 1.16 1.88 1.29 2.13 1.35
AUG 2.73 1.49 2.75 1.50 2.32 1.40
SEP 4.48 1.82 3.96 1.73 2.78 1.51
OCT 10.45 2.56 11.63 2.67 15.19 2.97
NOV 8.53 2.36 11.56 2.66 13.29 2.81
DEC 9.15 2.42 11.18 2.63 12.71 2.76



We know through the distribution and resulting relationships with Hrm, and H, that


H, = 1.416 [H]1/2 (3.26)


Substituting for H2 and averaging over the data collection period t, results in

72 n=1 FTn2 At"
Hb= 0.496 =1 F(TE)H At (3.27)
2 n= 1 Atn

and H,, denotes the significant wave height over the nth time increment, At, The data

are read from files and analyzed based on the time between records. Therefore, for each

record taken (usually every 6 hours), F(Tn) is calculated and inputted along with Hn into

equation 3.27.

Tables 3.4, 3.4, and 3.4 present the developed effective wave heights from the above

analysis at each of the east coast sites. The data are listed by month and from north to

south along the eastern coast.

















Table 3.2: Wave Height Information For Jupiter Island, Delray Beach, and Hillsboro Beach.
Units of H;2 and (H5/2)04 are (ft)5/2 and ft, respectively. These data obtained by inter-
polation from adjacent CDN stations

MONTH JUPITER ISLAND DELRAY BEACH HILLSBORO BEACH
____b (__2_0__ Hb (H72)0o4 Hb (b')
JAN 12.30 2.73 10.02 2.51 8.47 2.35
FEB 6.69 2.14 3.67 1.68 3.38 1.63
MAR 11.58 2.66 6.68 2.14 6.34 2.09
APR 5.19 1.93 3.72 1.69 3.07 1.57
MAY 9.06 2.41 7.55 2.25 6.15 2.07
JUN 3.15 1.58 2.54 1.45 2.23 1.38
JUL 1.57 1.20 0.97 0.99 0.87 0.95
AUG 1.47 1.17 0.72 0.88 0.71 0.87
SEP 1.77 1.26 0.83 0.93 0.78 0.91
OCT 19.16 3.26 17.22 3.12 13.26 2.81
NOV 9.52 2.46 5.50 1.98 4.91 1.89
DEC 10.89 2.60 7.97 2.29 6.94 2.17


Table 3.3: Wave Height Information For Pompano Beach and Hollywood/Hallandale. Units
of and (H52)0.4 are (ft)5/2 and ft, respectively. These data obtained by interpolation
from adjacent CDN stations

MONTH POMPANO BEACH HOLLYWOOD/HALLANDALE
______ (H72)0.4 Hb2 (HF2)0.4
JAN 8.02 2.30 5.88 2.03
FEB 3.29 1.61 2.89 1.53
MAR 6.25 2.08 5.78 2.02
APR 2.89 1.53 2.00 1.32
MAY 5.75 2.01 3.80 1.71
JUN 2.14 1.36 1.71 1.24
JUL 0.85 0.94 0.71 0.87
AUG 0.70 0.87 0.69 0.86
SEP 0.76 0.90 0.68 0.86
OCT 12.13 2.71 6.67 2.13
NOV 4.74 1.86 3.92 1.73
DEC 6.64 2.13 5.22 1.94








26

3.5 Remaining Parameter Summary

3.5.1 Wave Refraction

It can be shown that direct application of the linearized equation 3.7 overestimates the

transport losses due to the neglect of wave refraction. Specifically, the factor G in equa-

tion 3.8 should be modified by multiplication by a term R presented below. In estimating

an effect due to refraction we implement Snell's Law to determine a ratio between the wave

celerity at the location of the depth of closure and at the effective breaking depth.


sin(p ab) = Cb/C.sin(P a.) (3.28)

R = Cb/C* (3.29)

Here, C. is the wave celerity at the depth of profile closure and Cb that at breaking.

This modification to the diffusivity factor will be applied to both analytical and numerical

applications.

Closure depth, defined as the limiting depth beyond which no sediment transport occurs,

is difficult to establish precisely. Representative values of 18 and 10 ft. for the Atlantic coast

and Gulf coast respectively are assumed initially. These will be altered where information

at a particular project suggests otherwise. Volume calculations depend highly on this term

since we assumed a uniform profile movement.

3.5.2 Sediment Size

Dry beach width gained per unit volume of nourishment material is directly related

to borrow sediment size. A coarser fill sediment will result in greater beach width than

smaller sediment sizes, and more of a finer nourishment sand will be required to fill out

the offshore milder associated slopes. Additionally, greater amounts of sediment transport

will occur for finer than coarser sediment. Relationships exist which are developed by

analytic models suggesting relationships between k and sediment properties. The Army

Corps of Engineers presents a relationship of k with the sediment fall velocity parameter. A

relationship between sediment size and k values has been suggested by field studies (Dean,










2.0

\ *




1
0 1.o -,





0 I -I I
0 0.5 1.0
DIAMETER, D (mm)


Figure 3.6: Plot of sediment diameter and the k value (after Dean, 1988)

1988), and is utilized in estimating a first approximation to the k value. This relationship is

shown in figure 3.6. Where inadequate sediment information exists, the constant, k =0.77,

will be applied (Komar and Inman, 1970). These guidelines are followed for initial constant

application and both k and the closure depth will be studied by sensitivity analysis in several

situations where indicated by data.

3.6 Model Summary

The model is a basic one-line numerical iteration based on input of site specific pa-

rameters. The computational domain is chosen based on the project initial conditions and

boundary conditions. The resulting planform following construction is overlaid onto the

domain and allowed to evolve based on the methodology above. It can be seen that the sig-

nificant parameter in the numerical application is the following term seen in equation 3.14:

GAt
r =G (3.30)

In this simple term, we have most of the major "movers" of sediment following a nourishment

event. It can be shown that in order for numerical stability, F <0.5.










28
The model is set up to churn through the months based on the changing wave conditions

as well as days in the month. The time increment At is set at 86,400 seconds or one

day. Thus, the model acts on the material placed on the previously "straight" shoreline

in intervals of one day. At times of interest, the model outputs volumes remaining within

original project limits.

The grid is laid out according to figure 3.5 and set up with applicable grid widths

ranging from 400 to 1000 ft. in the longshore direction. Wave heights are transferred to

an applicable breaking height appropriate for our analysis (equation 3.27). The informa-

tion calculated at each CDN location is interpolated to the project location of interest.

Background nourishment information is input at known locations in reference to monument

location and interpolated to the grid location for the model. These values are then allowed

to act on the remaining volume and output is provided at the various times of interest.

Multiple nourishments are handled by adding the renourishment amounts from the new

construction to the existing "remains" from the action on the previous nourishments. It

is therefore a cumulative process of determining the final resulting planform. Volumes are

calculated by multiplication of the sums of the extended beach lengths (seaward) times

the grid width, and finally by the depth of closure. Again, the assumption of a uniform

movement in profile is utilized.

The total erosion from the nourishment fill area will be the sum of the background

erosion rate and the spreading out losses due to planform evolution. In the same analogy,

the total littoral transport rate is due to the addition of the localized littoral transport and

the rate due to the nourishment. The principle of superposition holds due to the linearity

of the model.

Finally, sensitivity information is collected by allowing the important parameters to vary

over the life of the project to obtain their influence and effect on the projected volumes.

Results from the model volume calculations and sensitivity analysis will be reported for

each project.
















CHAPTER 4
PROJECT APPLICATION AND RESULTS



4.1 Introduction

Figure 4.1 shows the location of each of the ten projects evaluated here. Each project

will be summarized below including specific nourishment characteristics, local conditions,

historical shoreline changes, and parameter evaluation. Finally the actual versus predicted

volumetric changes will be presented as well as appropriate sensitivity analyses.

4.2 Application and Results for Each Location

4.2.1 Delray Beach

Delray Beach is located in Palm Beach County on the southeast coast of Florida ap-

proximately 50 miles north of Miami (Figure 4.2). Five miles to the north is South Lake

Worth Inlet while Boca Raton Inlet is 6.7 miles south. The city began an erosion control

program in 1973. A reduced littoral drift environment exists at Delray Beach due to South

Lake Worth Inlet in combination with shoreline defense structures just north (updrift).

Vertical seawalls, concrete block revetments, and coral rip rap were installed in the 1960's

to prevent further damage and erosion. Erosional pressure was thus simply being forced

further south. Background erosion rates from DNR data range from an erosion of 5.8 ft/yr

to an accretion of 1.4 ft/yr. These data are average changes over a 25 year period prior to

nourishment 1945-1970, and are shown graphically in figure 4.3. The location of the DNR

monuments are located in the grid network for the project and the associated shoreline

change rate inserted with a running average of 5 points used to determine each grid point

rate. The average rate of the period is approximately 1.5 ft/yr of erosion in the project

limit domain. Variation of the background rate for approximately 4 1/2 miles north and
















CHAPTER 4
PROJECT APPLICATION AND RESULTS



4.1 Introduction

Figure 4.1 shows the location of each of the ten projects evaluated here. Each project

will be summarized below including specific nourishment characteristics, local conditions,

historical shoreline changes, and parameter evaluation. Finally the actual versus predicted

volumetric changes will be presented as well as appropriate sensitivity analyses.

4.2 Application and Results for Each Location

4.2.1 Delray Beach

Delray Beach is located in Palm Beach County on the southeast coast of Florida ap-

proximately 50 miles north of Miami (Figure 4.2). Five miles to the north is South Lake

Worth Inlet while Boca Raton Inlet is 6.7 miles south. The city began an erosion control

program in 1973. A reduced littoral drift environment exists at Delray Beach due to South

Lake Worth Inlet in combination with shoreline defense structures just north (updrift).

Vertical seawalls, concrete block revetments, and coral rip rap were installed in the 1960's

to prevent further damage and erosion. Erosional pressure was thus simply being forced

further south. Background erosion rates from DNR data range from an erosion of 5.8 ft/yr

to an accretion of 1.4 ft/yr. These data are average changes over a 25 year period prior to

nourishment 1945-1970, and are shown graphically in figure 4.3. The location of the DNR

monuments are located in the grid network for the project and the associated shoreline

change rate inserted with a running average of 5 points used to determine each grid point

rate. The average rate of the period is approximately 1.5 ft/yr of erosion in the project

limit domain. Variation of the background rate for approximately 4 1/2 miles north and









30



















r THOLM iTcES i N
A I I I- -
o CwIN, AI A UDSDf -
GULF HAMILONi









O c o -Y J
S--iBERTY WAUIULLA' I
I F LOR"UL KNI IA 1 ,

'- CHRIST J JOH
'u IE I 4 ALACJ P U 114 LUCU'E
SLEVYOKEECHO
I' A RO A 1 BE f
GULF o ,Delray


va HERERNADbEYIOt I c C
I I ORA IIE ape
oL ASCO Canaveral
N PU L LK 1A





.-1 .Hollywood/
SIc I Indialantic

Treasure/A - oKE O R Ft. Pierce
Wsland %,.- r%"^ r66!^
CIEIII rSOT ),,A H, iJupiter
\ i F :1 E I H rE ":4 1ST.U
I OxCHO-- island
A \ --01 -,Delray
Captiva.^^ y L." jr '_m "uI mui LIcA < Beach
Island ------ Hillsboro
COLLIER" BHOIvA.o j- Pompano
.Hollywood/
-i1 Hallandale


--
a-


Figure 4.1: Location of beach nourishment projects to be studied.










31
south of the construction limits is also seen in the figure. A severe littoral environment thus

existed and a long range solution was needed to replace the "quick fix" solutions. A long

term beach nourishment solution was selected and an adequate sediment supply for borrow

material was located directly offshore.

The erosion control program at Delray Beach thus began in 1973 with 1,634,513 cubic

yards (CY) of borrow material placed on a project length of 13,850 feet. Following the

rule of thumb in which 1 square foot of change in beach area equals 1 CY of sediment,

the shoreline should be extended an average of 118 feet. Placement of sediment was not

attempted as a rectangular (in planform) shape, and the actual volume addition distribution

at each grid coordinate was replicated in the model (Arthur V. Strock & Associates (AVS),

1975). Initial design called for adequate profile monitoring and renourishment intervals with

the original nourishment completed in August of 1973.

The first renourishment was undertaken from February through July of 1978 to increase

storm protection and recreational benefits to those of the original nourishment. Approx-

imately 70% of the original nourishment was found by survey to remain in the project

area. A quantity of 701,266 CY of sand was placed in two site specific areas: One near the

southern end of the city and one near the north, both within the original project limits (see

Figure 4.2). This fill was estimated as essentially rectangular for modeling purposes (per

conversation with Coastal Planning and Engineering, Inc.).

A second renourishment was constructed in September and October 1984 within the

original nourishment construction limits. A volume of 1,311,006 CY of offshore material

was pumped to the approximate 14,000 ft project length. A major storm on Thanksgiving

Day, one month after completion, caused major damage along Florida's east coast. Effects

on the upland beach and facilities at Delray were minimal due to this continued erosion

control program. From the outset of the initial nourishment, 14 profile surveys have been

performed and reported. This project monitoring effort far exceeds the normal program

attempts. Detailed reports for the various monitoring studies are provided by Coastal












Table 4.1: Delray Beach Nourishment History
DATE QUANTITY (CY) LENGTH (ft.)

8/73 1,634,513 13,850
7/78 701,266 6,746
2,225
8/84 1,311,006 13,850



Planning and Engineering (CPE). Table 4.2.1 is a summary of the Delray nourishment

history.

Wave height information is interpolated from CDN data stations off West Palm Beach

and Miami. The resulting effective wave height is 1.99 feet with an average period of 6.4

seconds. The model boundaries are maintained at sufficient distances from the projects so

that the fixed shoreline boundary conditions do not affect predictions, following the case 1

description presented in chapter two (figure 2.2).

Figure 4.4 is a comparative plot showing model and survey volumes over a 14 year

period from 1973 until 1987. This format will be utilized in most of the project result

presentations, with cubic yards remaining on the y-axis versus increasing time from original

sand placement of the x-axis. Each of the subsequent renourishments are easily seen in

the figure by both model predictions and actual survey data. The closure depth has been

reported as 15 feet for the Delray Beach area which relates to a value of 24 feet for (h, + B).

Borrow material was much finer and slightly poorer in sorting than the native sediment

with a reported size in the range of Ds0 = .23mm. The k factor used is therefore 1.3. This

combination of parameter input resulted in a standard deviation of 242,000 CY, a value

quite favorable for a 14 year period with multiple nourishments.

Sensitivity of model prediction performance in regard to the two parameters k and

(h, + B), is plotted in figure 4.5. This is a contour plot showing, for ranges of k and

(h. + B) values, the resulting variance. A minimum standard deviation of 90,000 CY and

thus the "best fit" over the study period resulted from a k factor of 1.3 and a (h, + B) value








33
of 27 feet. With a prescribed (h, + B) value of 24 ft., the minimum variance occurred at a

k value of 0.6. The model results data point shows the comparative variance due to model

values of (h, + B) = 24 and k = 1.3. This data point and the minimum variance point are

marked in the figure. The plot clearly shows a "valley" of variance values, beyond which

the variance increases. To explore this sensitivity measure one step further, the variance

is plotted versus the k parameter alone, figure 4.6, keeping (h. + B) constant at 27. The

minimum variance results from k = 0.6 and the figure illustrates the resulting increase in

prediction deviation away form this k value. It is interesting however, that with an increase

to 27 for (h, + B) (which is considered an average value for the east coast of Florida) the

minimum k is precisely that predicted by the relationship in figure 3.6. This diagnostic

approach could be very important in future nourishments at this area.

Finally, ignoring refraction effects results in a much over- estimated volume depletion

for the 14 year period. This is seen in figure 4.7 and is the basis for introducing a refraction

application into the modeling scheme.

4.2.2 Cape Canaveral

The Cape Canaveral Project area is on the Atlantic Coast of Florida just south of the

southern jetty at Port Canaveral (figure 4.8). This area was in a state of accretion until

construction of the inlet in 1951 and associated training jetties from 1951-1954. Studies of

the littoral environment suggest the existence of the jetties create a near complete littoral

barrier for any southward sand movement (Hunt, 1980). The area south of the inlet eroded

at an average rate of 5 feet annually from 1954 to 1965 (USAE, 1967). A nourishment

project was begun in June of 1974 and completed in March, 1975 to alleviate the erosional

stress on the area. Also indicated in figure 4.8 are approximate shoreline changes through

seven years taken from aerial photographs (from Stauble, 1984)

The nourishment sediment was taken from the Trident Submarine turning basin, sam-

pled adequately at appropriate intervals, and analyzed by standard sieving. Pre-construction

and borrow material phi sizes are 2.00 and 1.59 respectively corresponding to .25 mm and


I Ak
















S North
City Limit









Atlantic Ave.


City of
Delray Beach


South


North Limit
S1984 + 1973
.. Construction



1978 North
Construction

R-180




0
0

R-185


S1978 South
* Construction

South Limit
R-189 1984 + 1973
Construction






scale
0 1
mile


Figure 4.2: Delray Beach area and project locations
























DELRAY BEACH ARER BACKGROUND EROSION


10


8

aC


.-

4
Z-
LLI
LO
z






c-c
LI
Z


UJ
-6


-6



-B



-10


GRID COORDINATE BACK EROS


Figure 4.3: Delray Beach area background erosion: shoreline change plotted at DNR mon-
uments for 1945 -1970























DELRrY BEACII PROJECI: MODEL & SURVEY
2800000
MODEL
...................... SURVEY
2520000 _
Project completion date Initial design volume CY)
8/1973 1,634,13
7/1978 701,266
2240000 8/1984 1,311,006


1960000


S1680000


S1400000 /. ...






840000 -


560000 Iffective wave eight 1.99 ft.
Sediment size : 0.23 mm
(h.+B): +24 ft.
LU








280000 -

1073 1978 1984

0 12 2 36 8 0 7A2 8 96 108 120 132 144 156 68
MONTHS AFTER INITIAL PLACEMENT


Figure 4.4: Delray Beach: model prediction and survey volumes








33
of 27 feet. With a prescribed (h, + B) value of 24 ft., the minimum variance occurred at a

k value of 0.6. The model results data point shows the comparative variance due to model

values of (h, + B) = 24 and k = 1.3. This data point and the minimum variance point are

marked in the figure. The plot clearly shows a "valley" of variance values, beyond which

the variance increases. To explore this sensitivity measure one step further, the variance

is plotted versus the k parameter alone, figure 4.6, keeping (h. + B) constant at 27. The

minimum variance results from k = 0.6 and the figure illustrates the resulting increase in

prediction deviation away form this k value. It is interesting however, that with an increase

to 27 for (h, + B) (which is considered an average value for the east coast of Florida) the

minimum k is precisely that predicted by the relationship in figure 3.6. This diagnostic

approach could be very important in future nourishments at this area.

Finally, ignoring refraction effects results in a much over- estimated volume depletion

for the 14 year period. This is seen in figure 4.7 and is the basis for introducing a refraction

application into the modeling scheme.

4.2.2 Cape Canaveral

The Cape Canaveral Project area is on the Atlantic Coast of Florida just south of the

southern jetty at Port Canaveral (figure 4.8). This area was in a state of accretion until

construction of the inlet in 1951 and associated training jetties from 1951-1954. Studies of

the littoral environment suggest the existence of the jetties create a near complete littoral

barrier for any southward sand movement (Hunt, 1980). The area south of the inlet eroded

at an average rate of 5 feet annually from 1954 to 1965 (USAE, 1967). A nourishment

project was begun in June of 1974 and completed in March, 1975 to alleviate the erosional

stress on the area. Also indicated in figure 4.8 are approximate shoreline changes through

seven years taken from aerial photographs (from Stauble, 1984)

The nourishment sediment was taken from the Trident Submarine turning basin, sam-

pled adequately at appropriate intervals, and analyzed by standard sieving. Pre-construction

and borrow material phi sizes are 2.00 and 1.59 respectively corresponding to .25 mm and


I Ak















VFRIRNCE PLOT


0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7
K VLIJES


Figure 4.5: Delray Beach: parameter variance plot; contours of variance calculations X1010.






















DELRAT BERCH: K FACTOR SENSITIVITY

Pro i ct completion dt Initial desil voltme (CY)
73 1,34,613
r T 7917 I 2I


S 8/1984 1,311,006
Effective wave height : 1.ft.
S\dimeat ie il: 0.28 mm
(h. + B) : 4 ft.


30.0


27.0


24.0


21.0


18.0


15.0


12.0


9.0


6.0


3.0


0.0


0.2 0.41 0.6 0.8 1.0 1.2 1. 1.6 1.8 2.0 2.2 2.1 2.6 2.8
K VALUES


Figure 4.6: Delray Beach: k parameter variance with constant (h. + B) =24.0


/


3.0 3.2


[,.- -,- ,llht, I ,.... I
|lledlmeat iIl|e : I Oll mm|
l(h" +B): Is4- I


























DELRAY BERCH: REFRACTION EFFECT

_I-MODEL W/REFR
............ ......... SURVE
... .. MODEL I/0 REFR .


Project completion date Initial design volume (CY
8/1973 1,634,513
7/1978 701,266
8/1984 1,311,006


/
/
N.,
I
N.,
N.,j


N-^
N._


'N..


N.

N,

'N,


Effective wave heiglh : 1.99 ft.' "
SSediment sie : 0.23 mm
(h. + B) : 24 ft.


1984


1 24 36 S 60 72 B 98 6 108 120 132 1 4 I6 1E68

MONTHS AFTER INITIAL PLACEMENT


Figure 4.7: Delray Beach: refraction effects on prediction of evolution


2800000



2520000


2210000



1960000-


CD
S1680000-

Z
"i--


cc 1400000 -


m 1120000 -








560000 -


280000


1973


u










40
.33 mm. The borrow sediment size relates to a k factor of 1.1. The project length extended

2.1 miles south of the inlet. Approximately 2,300,000 CY of sediment was pumped onto

the project area with a majority located near the jetty end, the northern limit of the com-

putational grid. Average wave heights of 2.01 feet affect the coastline with effects due to

the large shoal of the Cape not taken into effect. The approximate size of the shoal is 100

million CY and is certainly capable of introducing refraction and diffraction effects. The

CDN station offshore of the Cape provided thewave characteristics.

The boundary condition applied here is categorized by the case 3 example in chapter 2,

figure 2.2, in response to the inlet and jetties. An approximation to the longshore transport

rate is necessary for this application. Estimates of net longshore sediment transport rates

range from 250,000 CY/yr (Walton, 1976) to 360,000 CY/yr (Army Corps of Engineers)

both in a southward net direction. A subsequent forced slope immediately south of the jetty

follows from the boundary condition illustrated earlier. An evaluation of erosion data (Dean

and O'Brien, 1987) can be interpreted to show a volumetric rate of erosion south of the

inlet of approximately 200,000 CY/yr. It will therefore be assumed here that (Q QBP) =

200,000 CY/yr. This results in an average wave angle of 5.8 degrees also indicating the

resulting defensive posture angle of the shoreline south of the jetty. Calculations based on

a drift rate of 350,000 CY/yr result in an approach angle of 9.3 degrees.

The responsiveness of the model to these two approach angles is illustrated in figure 4.9.

The difference in prediction of volumes remaining at 12 months is 104,749 CY and at 72

months is 622,724 CY. An accurate littoral transport rate is obviously a key parameter in

project application near structures.

Project profiles were taken before and after construction at project specific profiling

locations tied into DNR monuments. Results of four monitoring efforts were presented over

the course of the first six years after project completion. These are seen in figure 4.9 and can

easily be compared with the prediction results of model application. The first monitoring

volume at two months following placement only included the volume change above mean


1








41
water. It therefore reflects the initial sorting and movement offshore of finer material.

The offshore volume change must be included for comparison in this analysis. The second

monitoring report at eleven months reported a volume loss of 269,000 CY. Variance from the

"5.8 degree" modeling prediction is 94,000 CY or approximately four percent of the original

placement. Aerial photography and survey results at 66 months following completion show

68 and 60 percent respectively of the material placed remaining as shown on the figure.

The survey results reflect a much greater volume remaining within the project limits. A

difference of over 600,000 CY between prediction, "5.8 degree", and survey volumes results

in the 66 month period following placement. It is possible, yet not incorporated, in the

numerical application that an over-prediction would result if the nourishment volume does

not replicate the original shoreline. Should the seaward extension be less, the fill would

assume a more advanced state of evolution and thus less erosion compared to a fill out to

the pre-inlet shoreline. Improvement in the modeling of this possibility is needed.

The erosion during the six year monitoring study was concentrated in the center half

of the project boundaries which could be due to the sheltering effect of the Cape's offshore

shoals. This can not be represented in the modeling effort, but introduces possibilities for

future research. Sources of survey error were introduced in the 12 month survey report

from -10 to -20 ft. depth. Volumes reported are therefore only calculated out to a depth

of 10 ft. The model assumption is a profile shift out to the depth of closure, assumed here

to be -18 feet. Should a positive volume exist in the error range of depths, the 12 month

deviation could conceivably diminish.

Analytical prediction is also shown in figure 4.9. Close agreement with the 5.8 degree

case is due to the introduction of an F factor of .33 and an ambient transport of 300,000

CY in to the analytical expression. Analytical results should reflect the finite difference

predictions in cases where there are no additional nourishments. The variances shown in

the figure are inherent due to the initial non-rectangular nourishment scheme with placement

of larger volumes near the jetty.














Borrow
Area


'Ii
I


C Port


High Water Lines
----2/14/43 Historical I
- 7/17/73 Pre-Nourishment m
-*-1/9/75 Post-Nourishment..
---9/30/80 7 Years After i



III/

I c
m
*, I -r


c_


It
i1 m




I: r
..1



I:
scale .
0 1 I
mile
.-- R 016
r Canaveral
Pier


SCanaveral




oop
^"b

0
0


Figure 4.8: Cape Canaveral: project and borrow area locations. (after Stauble, 1985)





















CAPE CANAVERAL VOLUME PREDICTION
2SP 0 -00
t____t___ NMODEL 5.8 DEG
........ ........ODEL 7.9 DEC Project completion date: 3/1976
2250001 ..... .nNL TTICRL VOLU Initial design volume: 2,300,000 CY
Project length : 11,088 ft.
Effective wave height : 2.01 ft.
SSediment size : 0.33 mm
2000001 (h. +- B) : 27 ft.
,.- QOr : 200,000 CY
U( '.. 350,000 CY
""- Approach angle : 5.8 deg.
S1750001 "9.8 deg.


CD
Z I50000"ooon
Z
50 150000
z

S1250000'.



C I Or r U

- 750000S
0





250000




0 12 24 36 '8 60 72 80

MONTHS AFTER INITIAL PLACEMENT


Figure 4.9: Cape Canaveral: survey volumes and resulting model volumetric changes for
two cases of varying transport rate.










4.2.3 Indialantic Beach

Indialantic Beach is located on the Atlantic Coast in Brevard County approximately 30

miles south of Cape Canaveral (Figure 4.10). The nourishment project started in October

of 1980 and was completed by January, 1981. A total of 255,139 CY of sediment was placed

on a project length of 2.17 miles. The material was obtained from the Port Canaveral

submarine turning basin for use during the Cape Canaveral beach nourishment project in

1974, and had a similar mean size but a poor sorting in relation to the natural sand. A

reported sediment size of D50 = .4 mm translates to a k factor of 0.9. The planform deviated

significantly from a rectangle and original input information varied over the five fill "zones"

(5 to 43 ft of beach width increase, see figure 4.11). This figure typifies the model setup used

throughout the thesis in regard to grid layout and beach extension. Indialantic construction

volume is very low in comparison to the other projects in both dry beach extension and

volume/ft of project length (Stauble, 1986).

Three project profile lines and two control profiles outside of construction limits were

established for the monitoring effort. Post construction profiles were taken twenty-four

hours after placement of fill segments, whereas most nourishment projects are surveyed

following the entire fill placement. This difference allows calculation of the initial sorting

losses per fill zone. Also, the surveys extended seaward only to depths of 5 to 10 feet. These

two effects introduce problems in the analysis of the resulting performance. The remaining

volume of sediment located in the zone from the end of the profiles to the closure depth is

not known and therefore cannot be taken into account.

Boundary conditions were similar to Delray Beach in that the computational area was

set large enough so that there would be no influence within the construction limits. Results

from Cape Canaveral and Vero Beach CDN included a representative wave height of 2.22

ft. and a period of 8.11 seconds. Figure 4.12 includes plots of the predicted model volumes

and analytical volume results against the survey data at the various time periods. The large

variance from the predicted results are assumed to be created by the unaccounted volume











45
beyond the profile survey depths and a poorly known background erosion rate. Erosion rate

is set at zero for the project length in figure 4.12.

Stauble (1986) suggests a shoreline retreat rate of 5 ft/yr before 1960, and a relatively

stable shoreline thereafter, while (DNR) rates for Brevard County vary significantly over

this area of the coast. The background erosion effect is heightened on low construction

volume projects in regard to the total loss calculations. A look at the sensitivity of this

parameter is therefore warranted. To understand the importance of the background erosion

rate with this small project volume, figure 4.13 plots model results produced with varying

rates (+2, 0, -2, and -5 ft/yr). A significant variance results with a relatively small change

of 2 ft/yr, while a change of 7 ft./yr. (+2 to -5 ft) results in a difference at 6 years of 500,000

CY (roughly twice the initial project volume). It also brings the prediction closer to the

survey data; however they should never theoretically meet due to the neglect of sediment

in depths greater than the survey extent.

4.2.4 Jupiter Island

Jupiter Island is located on the Atlantic Coast in Martin County approximately 80 miles

north of Miami (Figure 4.14). The Town of Jupiter Island is 6 miles to the south of St.

Lucie Inlet and has experienced significant erosion over the past one hundred years. Aubrey

(1988) notes that the narrowing of the continental shelf in this region coupled with the lack

of sheltering from the Bahama banks create a higher erosion potential than areas to the

north (wider shelf) and south (sheltering). This is also reflected from the tabulated effective

wave heights in chapter 2. Beginning in the mid-1950's, attempts were begun to stabilize

the beach and have included some 8 million CY of sediment along with miles of seawalls,

revetments, and groins. The first attempt at beach nourishment was completed in 1957.

Material was pumped to the beach from Hobe Sound intermittently from 1957 through

1963. The sediment quality was suspect as bay sand is normally of poorer quality, smaller

size, and contains higher organic and fine contents compared to other sources. Median grain

size of the natural beach sand prior to 1963 was .29 mm.











45
beyond the profile survey depths and a poorly known background erosion rate. Erosion rate

is set at zero for the project length in figure 4.12.

Stauble (1986) suggests a shoreline retreat rate of 5 ft/yr before 1960, and a relatively

stable shoreline thereafter, while (DNR) rates for Brevard County vary significantly over

this area of the coast. The background erosion effect is heightened on low construction

volume projects in regard to the total loss calculations. A look at the sensitivity of this

parameter is therefore warranted. To understand the importance of the background erosion

rate with this small project volume, figure 4.13 plots model results produced with varying

rates (+2, 0, -2, and -5 ft/yr). A significant variance results with a relatively small change

of 2 ft/yr, while a change of 7 ft./yr. (+2 to -5 ft) results in a difference at 6 years of 500,000

CY (roughly twice the initial project volume). It also brings the prediction closer to the

survey data; however they should never theoretically meet due to the neglect of sediment

in depths greater than the survey extent.

4.2.4 Jupiter Island

Jupiter Island is located on the Atlantic Coast in Martin County approximately 80 miles

north of Miami (Figure 4.14). The Town of Jupiter Island is 6 miles to the south of St.

Lucie Inlet and has experienced significant erosion over the past one hundred years. Aubrey

(1988) notes that the narrowing of the continental shelf in this region coupled with the lack

of sheltering from the Bahama banks create a higher erosion potential than areas to the

north (wider shelf) and south (sheltering). This is also reflected from the tabulated effective

wave heights in chapter 2. Beginning in the mid-1950's, attempts were begun to stabilize

the beach and have included some 8 million CY of sediment along with miles of seawalls,

revetments, and groins. The first attempt at beach nourishment was completed in 1957.

Material was pumped to the beach from Hobe Sound intermittently from 1957 through

1963. The sediment quality was suspect as bay sand is normally of poorer quality, smaller

size, and contains higher organic and fine contents compared to other sources. Median grain

size of the natural beach sand prior to 1963 was .29 mm.


































) Cape Canaveral

I BORROW AREA




7


Melbourne


Figure 4.10: Indialantic Beach: project location and borrow site. (after Stauble, 1985)


-- --






















INDIALANTIC


421'


23j.


91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110


Ax-600' ALONGSHORE DIRECTION, X (Computation Cell Numbers)

Figure 4.11: Indialantic Beach: bar diagram of planform and grid cell network after fill


229





















INDIRLANTIC PROJECT:


300000




250000


Li

200000





150000

LU
Cc
LLU
S100000
-J
ED


50000


MODEL & RNRLYTICAL


MONTHS AFTER PROJECT


Figure 4.12: Indialantic Beach: model and analytical prediction showing survey volumes.




























INDIALH-N IC PROJECT: EROSION HIITES


*2 FT Project completion date: 1/1981
. 0 FT Initial design volume : 255,139 CY
2 FT Effoctlve wave height : 2.22 ft.
SSediment ize : 0.4 mm
h.+B) 27ft..







N .........
-- --- -- '- C + B ) : __----------- f









N^ N .


1981
1221 --- ...--
12 2 36 118 60

MONTHS RFTER PROJECT


Figure 4.13: Indialantic Project: erosion rate sensitivity, +2 to 5 ft/yr.


00000 -





300000



>-
() 200000



C3
Z
.- 100000 -
2"

CE
--
LL
Cc

0-


--J -100000-
Ti


-200000




-300000 -
0


12 8t








50
Drag scraper operations began in 1963 and continued through the late sixties with

little beneficial effects. Borrow pits were located very near shore and the sand simply

refilled within a few months (Walton, 1976). The first major nourishment efforts with

offshore sediment were begun in 1973 and have continued with the most recent occurring

in 1987. Table 4.2.4 summarizes the different projects by listing volume placements and

length segments all within a large overall project area.

Sediment size from the offshore borrow area is small in comparison to the native sand

with a median size of 0.12 0.15 mm. This sediment size is significantly smaller than

all other project borrow materials analyzed in this study. Excess fine material is quickly

worked off the shoreface and transported away from the fill area. A k factor of 1.5 was

input along with an h. + B of 27 feet. CDN wave data interpolated between Vero Beach

and West Palm Stations in conjunction with CERC data at West Palm result in an effective

wave height of 2.26 ft and an average period of 7.5 seconds. Average background erosion

from DNR over the project study limits show an average of 2.61 feet of erosion per year

with significantly higher erosion in the northern segments of the Jupiter coastline. Quoted

rates by Stauble and others range from 0 to 8 ft/yr. Input for the model will be the DNR

reported rates varying with distance within the project construction limits (some 35,000

ft.), and associated with the model grid points.

The complexity of the resulting nourishment planforms, along with actual volumes

placed in particular grid elements created a formidable system to analyze. With multiple

nourishment events, of which Jupiter Island is a prime example, analytical methods are

inadequate. Table 4.2.4 highlights the history of nourishment events which served as model

input.

Figure 4.15 presents model results for the planform evolution. The value of using a

higher quality borrow sediment can be illustrated in reference to Figure 4.15 and analysis of

the 1981 monitoring profiles (Strock 1981). Twenty six profiles were reported with volume

calculations. Profiles 2 through 24 showed a significant variance between the depth of the












Table 4.2: Jupiter Island Nourishment Summary.
Signifies Placement in Multiple Segments


Multiple Reported Volume Per Year


1973 profiles and the monitoring depths of 1981. Nineteen of the profiles did not reach

adequate closure for effective and meaningful comparison. The twenty three profiles taken

in 1981 showed average shoaling of 1.7 ft over depths of 10 to 14 ft indicating large volumes

of sediment had shifted offshore. This could conceivably result in an underestimate of

1,500,000 to 2,000,000 CY which lay offshore beyond the survey limits. Shown on Figure 4.15

is the associated range of possible error for the 1981 survey and its proximity to the model

predicted curve.

Projects of long shoreline length show significant sensitivity to the erosion rate param-

eter input. Figure 4.16 plots model predictions based on uniform rates of 0, 5, and 8 feet

of erosion per year in comparison to the DNR fluctuating rate (average of 2.6 ft/yr). The

variation of predicted cubic yards remaining in the project limits at 15 years is 4.25 million

CY. From the DNR data run to the maximum 8 ft/yr erosion the variance is approximately

2.75 million CY. This large effect on total erosion from the ambient rate is due to the 35,000

ft. project area. At 2.6 ft/yr, the erosion would equate to 91,000 CY/yr. An opportunity

to study the effects of the background erosion rate as well as a chance to prove increased

longevity from improved sediment characteristics is lost due to the lack of frequent and

accurate profile surveys.


DATE QUANTITY (CY) LENGTH (ft.)

1973 2,519,362 17,821
1974 969,400 9,200
1977 267,000 2,588
213,066 3,600
1978 847,223 7,650
1983 594,000 5,850
406,000 3,150
1987 375,000 3,125
1,395,000 10,833
461,000 3,542

























































Figure 4.14: Jupiter Island: project locations for multiple nourishments. (Modified from
Aubrey, 1988).














JUPITER ISLAND PROJECT: MODEL PREDICTION


MONTHS AFTER INITIAL PLACEMENT


Figure 4.15: Jupiter Island: model volumes and indication of possible survey variance.


























JUPITER ISLAND: EROSION RRTE SENSITIVITY

-2.6 Fr DNR
............. ........ F0 F t.
..-.- .. ... -5 FI
------ --8 Fr
iProject completion date initial dait volume (CY)
1 97s 2,519,362
1974 969,400
1977 480,080
1978 847,223
1983 1,000,000
1987_ 2,231,000


S(dlm.nt il e: 0.11 0.15 mm
(h. + B) : 27 ft.


..........j .......

"'- l "- -- ,



NJI





S1977 1978 1983 1'1987
-. -



2X 36 48 B 7 8 96 10 120 132 1 16 [s

MONTHS RFTER INITIAL PLACEMENT


Figure 4.16: Jupiter Island: erosion rate sensitivity, 0 to 8 ft/yr range.


7000000


6510000


6nnnnnn


>-
55000n00


C3 5000000
z
i-

Z 115000001

(c
3 '000000
X: 4000000
IU
:D
3500000
LU

3 3000000
-J
0





1500000



1000000


-


-


-


""-'--
"""--
""'
"""--------......~~
""'------..!


I


i












4.2.5 Ft. Pierce

Fort Pierce is located on Florida's east coast in St. Lucie County, approximately 70

miles south of Cape Canaveral (figure 4.17). Ft. Pierce inlet was cut and jetties built

in 1921 with jetty reconstruction in 1926-1927. Beach erosion just south of the inlet has

plagued the region since the 1930's with an average recession of 4.3 ft/yr (U.S. Army Corps

of Engineers, 1984). The nourishment area consisted of a segment of beach immediately

south of Ft. Pierce Inlet's southern jetty. The project construction lasted one year from

May 1970 through May 1971 and consisted of 718,000 cubic yards of sand placed on 1.2

miles of shoreline.

An interesting placement method was used here and consisted of an experimental un-

derwater hydraulic dredge which had never been attempted previously. Problems forced

the return to normal dredging practice after the first 60,000 cubic yards was pumped. A

floating hydraulic pipeline dredge was used for the remainder of the sediment operating at

a capacity of 20,000 CY per day. There is no data for the sediment characteristics of the

borrow material.

Input for the data will simply be the assumption of .77 for the k value. Native material

was in the range of .15 to .25 mm median grain diameter. The average wave height at this

location is interpolated from the Vero Beach and West Palm Beach stations and resulted in

an average wave height of 2.39 ft and an average period of 8.23 seconds. Background erosion

rates were taken from St. Lucie County data compiled by DNR. The background rate in St.

Lucie County is calculated for two time periods. The first is the 17 year period immediately

following inlet construction, 1928-1945. The second period is a span of 22 years, 1945-1967.

Figure 4.18 illustrates the erosion rate for the entire county shoreline. The location of the

inlet at approximately monument R-34 is highlighted by the accretional area north, and the

associated erosional area south of the inlet jetties. Recovery is evident farther downshore.

The rates for the later time period are applied for model input to allow for the sharp change

associated with the years closest to the inlet construction to equilibrate. The average erosion


I








56
rate over the beach nourishment area is 6.2 ft/yr (average of approximately 40,000 CY/yr of

erosion). Of the 3.2 million CY dredged for inlet navigation improvements from 1930-1985,

2.7 million CY were dumped at sea, (Dean and O'Brien, 1987), and a mere 33,000 CY onto

the beach south of the inlet.

Post construction profiling was carried out by the U.S. Army Corps of Engineers,

(USAE), and was summarized in a four year study (USAE, 1975). Five post construc-

tion surveys covered this period and are compared to a pre-nourished profile. Methods

employed preclude the use of the majority of the survey results. The pre and post con-

struction surveys extended only 500 ft seaward of the baseline. Report analysis is suspect

due to the fact that the later surveys extend to 1,000 and then to 1,500 ft off the baseline

and direct comparisons are made to the 500 ft surveys. However, the volume change over

a two year period, 1973-1975, is apparently of similar origin and extent. The volumes are

calculated out to 10,000 ft south of the inlet or 3,500 ft past the nourishment limit.

Due to the absence of reliable data, a comparison is made between two boundary

condition applications. The first application assumes normal wave approach and a grid

network similar to case 2 (chapter 2). The St. Lucie erosion data discussed above provide

the ambient erosion rate information. The second assumes QBP =0.0 and calculation is

made of the associated shoreline angle downdrift of the jetty (case 3, chapter 2). A littoral

transport rate of approximately 200,000 CY/yr acts at this area with a reported range of

140,000 CY/yr to 225,000 CY/yr (Dean and O'Brien, 1987). The resulting approach angle

is 2.28 degrees. Figure 4.19 illustrates the predictions of the resulting volume. The plots

include a placement of 33,000 CY dredged from the inlet and placed on south beach in 1974.

Results of the different boundary condition applications shown in figure 4.19 reflect a large

difference in performance prediction. The first method is suspect in boundary application,

while method 2 agrees well with the analytical prediction until the introduction of the

miscellaneous sediment at the three year time level.











57
The report of the two year period of erosion, (1973-1975), listed a loss of 222,000 CY

out to 1,500 ft from the baseline while the model predicted 220,000 CY. The relative change

is in good agreement. However, a figure of 27% is reported for the volume lost during the

first 48 months, while model prediction results in 75%. Any conclusion is suspect due to

the method of data collection utilized in the monitoring effort.

4.2.6 Hillsboro

The Hillsboro Beach project is located in northern Broward County approximately 45

miles north of Miami. The project site lies within a 27,000 ft. stretch of coast bounded

north by Boca Raton Inlet and south by Hillsboro Inlet (figure 4.20). This is a small volume

and length project compared to the others included in this study. Approximately 385,400

cubic yards of sediment were dredged from offshore sites and pumped over a project length

of approximately 5000 feet. Fill operations were initiated on August 16, 1972 and completed

September 18, 1972.

Basically, the project area was divided into 12 cells alongshore, each 400 ft. wide along

the project baseline. Strock reports (1973, 1974, 1975) present the data in volume per

lineal foot per quadrant, based on establishment of 18 profile lines covering the project

area and adjacent areas. Borrow sediment median grain diameter is .6 mm relating to

a k of 0.55. Sediment studies performed in 1974, two years post nourishment revealed

a beach composite sand size smaller than the borrow material, .4 mm. Two incidental

sediment additions occurred after the initial nourishment in 1972. Hurricane Gilda (1973)

introduced approximately 4,000 CY of material stockpiled near the northern project limit.

Also, 16,000 CY were placed in the northern project reaches at Port De Mar (Strock, 1975).

Background erosion rates are determined by DNR survey reports over a 42 year period

(1928-1970). For all Broward County Projects, wave height and period calculations were

determined by interpolation between the West Palm and Miami CDN stations and CERC

data from West Palm Beach. At Hillsboro, the average effective wave height is 1.87 ft and

average period 6.3 seconds.






























*: Fort Pierce Inlet



= Borrow
S/ Area


0)
-H


1 Mile











0 Scale 1

Miles


Figure 4.17: Ft. Pierce: project and inlet location.











57
The report of the two year period of erosion, (1973-1975), listed a loss of 222,000 CY

out to 1,500 ft from the baseline while the model predicted 220,000 CY. The relative change

is in good agreement. However, a figure of 27% is reported for the volume lost during the

first 48 months, while model prediction results in 75%. Any conclusion is suspect due to

the method of data collection utilized in the monitoring effort.

4.2.6 Hillsboro

The Hillsboro Beach project is located in northern Broward County approximately 45

miles north of Miami. The project site lies within a 27,000 ft. stretch of coast bounded

north by Boca Raton Inlet and south by Hillsboro Inlet (figure 4.20). This is a small volume

and length project compared to the others included in this study. Approximately 385,400

cubic yards of sediment were dredged from offshore sites and pumped over a project length

of approximately 5000 feet. Fill operations were initiated on August 16, 1972 and completed

September 18, 1972.

Basically, the project area was divided into 12 cells alongshore, each 400 ft. wide along

the project baseline. Strock reports (1973, 1974, 1975) present the data in volume per

lineal foot per quadrant, based on establishment of 18 profile lines covering the project

area and adjacent areas. Borrow sediment median grain diameter is .6 mm relating to

a k of 0.55. Sediment studies performed in 1974, two years post nourishment revealed

a beach composite sand size smaller than the borrow material, .4 mm. Two incidental

sediment additions occurred after the initial nourishment in 1972. Hurricane Gilda (1973)

introduced approximately 4,000 CY of material stockpiled near the northern project limit.

Also, 16,000 CY were placed in the northern project reaches at Port De Mar (Strock, 1975).

Background erosion rates are determined by DNR survey reports over a 42 year period

(1928-1970). For all Broward County Projects, wave height and period calculations were

determined by interpolation between the West Palm and Miami CDN stations and CERC

data from West Palm Beach. At Hillsboro, the average effective wave height is 1.87 ft and

average period 6.3 seconds.













ST.LUCIE BACKGROUND EROSION RRTES


DNR MONUMENT NUMBER


Figure 4.18: Background erosion rates for St. Lucie County shorelines.





























FORT PIERCE V LIUJME PR[1 I CT IONS


MODEL METHOD I
.................M.... MODEL METHOD 2
. .. .... INAL TICA.







N\'
N\\
N\\
N\^
N^
N-
N\'
N'
N'


700000-

650000-

600000-

550000

500000-

450000 -

100000-

3500011

300000-

250000-

200000-

150000-

100000-

50000 -

0

-50000

-100000


-150001 .1------ ----
0 12


4/1971
718,000 CY
6,340 ft.
2.39 ft.
77 mm
27 ft.
100,000 CY
2.28 deg.


N
N--


N


N
N
N
N
N'
N


N
N
N


--- r6--- ---- r
24 36 18 60 72

MONTHS flFTtER INI rRI PlI FnC MENT


Figure 4.19: Ft. Pierce: model predicted volumetric changes.


750000


Project completion date:
Initial design volume :
Project length :
Effective wave height :
Sediment sie :
(h. + B) :
ro Q an :
Approach angle:








61


Table 4.3: Hillsboro Beach: Percent Remaining of Original Volume
MONTHS ANALYTICAL MODEL SURVEY
4 84.1 80.1 78.9
12 71.5 72.7
15 67.4 66.2 74.9
24 55.7 59.5
28 50.5 59.4 69.1
36 40.1 53.1
48 26.9 45.8


The erosion rate decreases from a maximum of 2.23 ft/yr in the northern project area

to 0.29 ft/yr in the southern reaches. This decrease could be connected with a long term

buildup north of Hillsboro Inlet (12,000 ft south of the southern project limit). Boundary

conditions of the infinite beach variety are assumed here with sufficient distances beyond

the project in the model grid network. This assumption may be questionable due to the

proximity of Hillsboro Inlet to the south. However, the project predictions only extend

three years, not enough time for the spreading losses to reach 12,000 ft south.

Volume calculations from three monitoring efforts are reported and subsequently com-

pared back to model predictions. The analytical and numerical results are seen in table 4.2.6

based on percent of original volume placed. The differences between the analytical and nu-

merical results are due to the inability of the analytical method to incorporate the volume

additions following the nourishment. This might not cause significant problems in a larger

fill, yet these later additions amount to 6 percent of the original nourishment. Hillsboro is

the second smallest volume project and significantly the shortest in length.

Figure 4.21 illustrates the two prediction attempts plotted along with the survey vol-

umes. Model prediction at fifteen months showed a deviation of 32,000 CY and at 28

months of 35,000 CY in comparison with the survey results. Both of these are under 10%

of the original nourishment volume. Sources of variance here include the unknown length

of survey extent seaward. As illustrated in a previous section, this can introduce significant















Table 4.4: Hillsboro Beach: Cumulative Volumes of Erosion Components

TIME AFTER
NOURISHMENT BACKGROUND EROSION DIFFUSION EROSION
(months) (CY) (CY)
12 5,544 103,349
24 11,088 139,349
36 16,632 157,135
48 22,176 177,804



variances. Each of the projects studied in Broward county have been set up with a known

h. value of 12 feet. Offshore of Broward County, the depth of closure is assumed to be 12

feet ((h, + B) =21)in contrast to 18 for a (h, + B) =27. This is due to a large expanse of

rock further offshore from this depth and associated minimal sediment transport.

If the survey closure did not reach a minimum of 12 ft, volume misrepresentations can

occur. This unknown must be evaluated properly in future projects to assure closure and

more representative volume calculations. Table 4.2.6 separates the nourishment erosion

into background rates and diffusion effects. The volumes listed are cumulative and can be

evaluated similar to the Hollywood/Hallandale summary. The diffusion effects are seen to

decelerate over time with 103,000 CY of sediment in the first 12 months reducing to 20,700

CY in the 12 month period from the third year to the fourth. The background effects

remain constant at 5,500 CY of erosion per year within the project limits.

4.2.7 Pompano Beach

Pompano Beach is located in Broward County immediately south of Hillsboro Inlet

approximately 30 miles north of Miami (see figure 4.22). Hillsboro Inlet, figure 4.23 is a

natural tidal inlet improved with a northern jetty built on a natural reef in 1966. A gap

in this section acts as a weir with a deposition basin immediately inside the jetty and an a

dedicated dredge which pumps material from the basin to the south beach (Jones, 1977).

It is estimated that prior to 1985 the bypassing rate averaged 60,000 to 80,000 CY and

after improvements in the system increased the volume to approximately 100,000 CY per












Palm Beach County

Broward County


Deerfield Beach


Fairlawn


R12


Pompano
Beach Highlands


North Pompano Be


1 Construction Limit




)ro Beach


Construction Limit







0


Hillsboro Inlet


Pompano


Figure 4.20: Hillsboro Beach: nourishment project area


scale
Sle
mile










64




















So~ 0
>1r u


cn

_J ir Qi-






Ioi 0
2: 0




LU-* ,/ -
U-



. -- I- 0






'o N ,x iwwO
- I I I3






o i CF





o, 0 N I 0 0A
'f n N in C











65
year. Erosion problems were first addressed by an initial project undertaken from May to

October 1970 covering three miles of coastline. The fill length of 16,800 ft was nourished

with 1,033,000 CY of sediment from offshore borrow areas located in 30 to 65 ft depths

and in three separate areas (Walton, 1977). The natural beach material was listed as a

median grain size of .92 mm from surface sand samples due to a high shell content. Wave

characteristics at this location interpolated from West Palm and Miami CDN data indicate

an average yearly wave height of 1.8 feet with an average period of 5.8 seconds.

A major nourishment was again required due to severe erosional problems and was

completed in August of 1983. The construction extended south from Hillsboro Inlet ap-

proximately 5.3 miles and included placement of 1,909,184 cubic yards of offshore sediment

(CPE). The southern construction limit concluded immediately south of Lauderdale-by-the-

Sea. The mean reported sediment size is 0.31 mm and a pre-construction beach median size

of 0.59 mm. The resulting k factor is 1.2.

The major complication in predicting performance of the project and erosion/accretion

of the area in general is due to the introduction of sand bypassing material at irregular

times and often without record. DNR erosion data for this section of Broward County is

unreliable due to the unaccountable volume introduction. Case 3 from chapter 2 is followed

in model application. For comparison, the results presented include two approaches. Both

include grid setup immediately south of a jetty, and an ambient transport rate, Qo, of

200,000 CY/yr. The first approach assumes a zero rate of sediment bypassing, QBP =0.0,

and the introduction to the system of the bypassing quantity, 70,000 CY/yr before 1985 and

100,000 CY/yr after. This is treated by implementing a "nourishment" event each 6 months

of half of the yearly bypass rate in the closest cell to the jetty. Qo QBP =200,000 CY/yr

and the resulting wave approach angle is 5.25 degrees. Alternatively, the second approach

assumes a bypassing rate of 100,000 CY/yr in the calculation of the defensive posture and

results in (f/ ab) =1.21 degrees. Essentially the methodology is sound in both cases and

the results are shown in figure 4.24. Model 12N stands for the "nourishment" approach,









66

the first discussed above. The timing of the increased bypassing amount occurs after 24

months of evolution resulting in the abrupt slope change. The second approach follows the

more strict interpretation of the boundary condition. Analytical results are also plotted on

figure 4.24 and are shown to mask the second approach.

Monitoring of the second project included 28 construction limit profile surveys as well

as two control profiles south of the project, all utilizing DNR monuments. The 12 month

survey, performed by CPE reflects an exact correlation with the second modeling case as

well as the analytic prediction. A loss of 159,000 CY is predicted and realized. A five year

survey performed by the County from the baseline to the 12 ft contour shows a cumulative

erosion of only 82,700 CY. Method two predicts a loss of approximately 650,000 CY. The

survey volume is suspect due to the time interval and minimal loss. Without other survey

information, the success of the 12 month prediction can not be confirmed.

4.2.8 Hollywood/Hallandale

The Hollywood/Hallandale beach area is located in the southern reaches of Broward

County approximately 15 miles north of Miami (figure 4.25). The effects of Port Everglades

Inlet, 3 miles to the north provide the dominant causes of an erosion problem which has

existed for many years. The inlet was opened in 1928 and training for navigation was

completed in 1931. Background erosion rates drawn from DNR survey data over a 37 year

period reflect variable erosional and accretional regions in part due to the movement and

subsequent closure of Dania Inlet by 1944. The inlet migrated 5,000 ft from 1927 to 1936

and was located at that time 10,000 ft south of Port Everglades Inlet. The remaining data

do not allow a calculation of change rate over a time period of anything greater than nine

years. From a 1978 county report, the Army Corps of Engineers lists a rate of 2 ft/yr for

an average yearly ambient shoreline recession. In a 1972 report on Port Everglades Harbor,

a 5 feet per year erosion rate was listed for the shoreline south of the inlet which is again 3

miles to the north. The historical rate of 2 ft/yr from the county summary report is used

for model input. The county report as well as the monitoring results were obtained from









67





N
























F-

Us
353
CD.
00
03 r0


0










46














0 1
mile


Figure 4.22: Pompano Beach: project locations for 1970 and 1983 beach fills






















N






0 500

Scale in Feet






Impoul
Ba

South Jetty Constructed
In 1952 & Modified In 196
Spoil Are.


A-1-A Bridge





:North


Constructed
1930



Weir Section


North Jetty Final
Construction 1965


Figure 4.23: Hillsboro Inlet: jetty construction history and impoundment basin location













































0i













1~















~~: /







/1 /


/:


> L

0
O

o
0
1












II
0
C- I



!


n- 0./


-~ c-.N .-. 0 ia


= = CN -


a
o
0
Q
a


'-2N









66

the first discussed above. The timing of the increased bypassing amount occurs after 24

months of evolution resulting in the abrupt slope change. The second approach follows the

more strict interpretation of the boundary condition. Analytical results are also plotted on

figure 4.24 and are shown to mask the second approach.

Monitoring of the second project included 28 construction limit profile surveys as well

as two control profiles south of the project, all utilizing DNR monuments. The 12 month

survey, performed by CPE reflects an exact correlation with the second modeling case as

well as the analytic prediction. A loss of 159,000 CY is predicted and realized. A five year

survey performed by the County from the baseline to the 12 ft contour shows a cumulative

erosion of only 82,700 CY. Method two predicts a loss of approximately 650,000 CY. The

survey volume is suspect due to the time interval and minimal loss. Without other survey

information, the success of the 12 month prediction can not be confirmed.

4.2.8 Hollywood/Hallandale

The Hollywood/Hallandale beach area is located in the southern reaches of Broward

County approximately 15 miles north of Miami (figure 4.25). The effects of Port Everglades

Inlet, 3 miles to the north provide the dominant causes of an erosion problem which has

existed for many years. The inlet was opened in 1928 and training for navigation was

completed in 1931. Background erosion rates drawn from DNR survey data over a 37 year

period reflect variable erosional and accretional regions in part due to the movement and

subsequent closure of Dania Inlet by 1944. The inlet migrated 5,000 ft from 1927 to 1936

and was located at that time 10,000 ft south of Port Everglades Inlet. The remaining data

do not allow a calculation of change rate over a time period of anything greater than nine

years. From a 1978 county report, the Army Corps of Engineers lists a rate of 2 ft/yr for

an average yearly ambient shoreline recession. In a 1972 report on Port Everglades Harbor,

a 5 feet per year erosion rate was listed for the shoreline south of the inlet which is again 3

miles to the north. The historical rate of 2 ft/yr from the county summary report is used

for model input. The county report as well as the monitoring results were obtained from











70

Coastal Planning & Engineering. The average significant wave height acting in this area

from interpolated CDN data is 1.62 ft with an average period of 5.56 seconds. Depth of

closure is assumed equal to 21 ft for all projects in Broward County.

A high volume, yet short length, project was completed in September of 1971 with

360,308 CY of sand/shell placed over 4,000 ft with sediment in the range of .2 to .46 mm

median diameter. No monitoring studies were performed on this original project resulting

in a lack of understanding of project performance. By the late 1970's, the erosion problem

was severe over a much greater length of coastline. To combat this problem, the two cities

chose beach nourishment for a long stretch of beach on the southern portion of the county.

This nourishment project was begun July 31, 1979 over a project length of over five

miles, 27,760 ft The southern construction limit lies on the county line between Dade and

Broward Counties. The initial plan called for sediment to be trucked into the area; however,

adequate supplies of suitable material were found offshore. Seven borrow areas eventually

contributed to the project, all located between 5,000 and 10,000 ft directly offshore of the

project limits (Suboceanic Consultants, 1980). The sediment was noted as "somewhat

smaller" than the natural sediment. Adequate analysis of the native sand resulted in a

median grain size of 0.35 mm with good sorting. Overfill ratios were determined for each

of the borrow composites and ranged from 1.00 to 1.30 with an average of 1.09. This shows

the slightly finer borrow material in comparison to the natural beach. A k factor minimum

was thus set at 1.05 and after further investigation, a final factor of k = 1.15 was used as

model input.

The original design volume for the fill included the following: design fill, loss of fines,

and a five year advance nourishment. The resulting volume was 2,035,500 cubic yards of

material. Dredging was completed on November 14, 1979 by the cumulative work of three

dredges to avoid the associated delays due to rough weather of the coming winter. The

pumped volume was approximately 97 percent of the design, a placement of 1,980,685 cubic

yards. The distribution across the planform was far from uniform and is approximated in












Table 4.5: Hollywood/Hallandale: Profile Volume Changes With Time Between Survey
Events
DATE MONTHS AFTER VOLUMETRIC CHANGE (CY)
INITIAL PLACEMENT
11/79 0
-175,879
5/80 6
-100,445
7/81 20
-146,162
9/82 34
-235,791
10/83 47
-118,124
12/84 61
-363,213
1/86 74



the model application. This ranged from a 125 ft extension of dry beach to a mere 30 ft

advance.

Monitoring was accomplished by profiling at 1,000 ft intervals after completion of con-

struction from the upland limit of fill to the intersection of the offshore depth and the

pre-construction survey profiles. Six months after completion, a volume of 1,804,806 cubic

yards was calculated as remaining in the project area. This relates to a loss of 9 percent of

the original volume. Further profiling was accomplished and is summarized in table 4.2.8.

Volumetric change in CY is listed between the survey dates and is not cumulative. For

example, 100,445 CY of material left the project area between 6 and 20 months following

completion. The resulting volumes found provide the survey input for comparison to the

model prediction.

In the numerical application, this area is treated as an open coast project with no direct

influence from coastal features (see case 1 discussion earlier. A projection for the following

7 year period is included and shown in figure 4.26 along with the survey volumes. A good

correlation results between the model prediction and survey volumes, particularly through








72

36 months. During this period the largest deviation was approximately 40,000 CY with

very close agreement throughout. The average deviation through this period is 29,053 CY

in contrast to the average deviation for the entire 6 years of 196,407 CY. The ability to

predict within 3 years at an error of 29,000 CY is considered highly successful. Correlation

decreases with time past the 3 year period and falls far off with the last survey at 74 months,

showing a difference in volume of 424,000 CY. Also included in figure 4.26 are the analytical

results through the same time period. Very close agreement between the model and analytic

predictions is illustrated through the six year study. The deviation at 74 months is 45,384

CY.

Sensitivity to the background erosion rate is presented in figure 4.27. The 2 ft/yr rate

was used in the results discussed above and is compared here to an increase to 4 ft/yr. A

significant improvement resulted in prediction success. With the 4 ft/yr rate, the standard

deviation decreases to 126,235 CY from 196,407 CY. Therefore, a simple adjustment of 2

ft in erosion along the project baseline improves the prediction "confidence" by 70,000 CY.

This improvement is significant in areas where the erosion rate is undefined. An interesting

approach in analysis is to differentiate between the erosion losses due to background erosion

and those due to spreading out losses. Table 4.2.8 lists the percentages of each along with the

total erosion loss in cubic yards. As expected it is shown that the diffusion loss percentage

will decrease with time for the perturbation of the shoreline is spreading out and erosion is

acting on a straighter and longer shoreline. The associated erosion percentage increase is

misleading. This loss is constant on a yearly basis and is 65,333 CY at Hollywood/Hallandale

yet becomes greater than 50% of the total erosion after only 4 years.

4.2.9 Treasure Island

Treasure Island is located in Pinellas County on a Gulf Coast west of Tampa Bay. The

3.5 mile long barrier island is typical of many west coast barrier island configurations and

is bounded to the north by John's Pass and Blind Pass to the south (figure 4.28). The area

has documented erosion from the mid 1800's to the present; however, the presence of the









73




N

jPort Everglades




SDania Cut Off Canal


Dania -"4,
4\;4-





Hollywood 0 I 0
Hollywooc [ i :- .
m
Beach z S =. -



-- I----
Hallandale


Golden Beach




S* Nautical Miles
1 1/2 0
Scale


Figure 4.25: Hollywood/Hallandale: project and borrow area locations.























HIOLLYNOOD/HfLLRNDRI E MODEL RND SURVEY


---- --


. A-*1


12 2- 3
12 2t 36


2000000



1 800000



1600000 -
>--
U
S11I00000


C3
1200000



S1000000 -

LL
800000 -
LLI
:-
600000



400000



2[00000


___ODEL
...................N... ALYT ICRL
-...-- .. SUVEfr


Figure 4.26: Hollywood/Hallandale: survey, analytical, and model volume results


Project completion date: 1i1/1979
Initial design volume : 1,980,685 CY
Project length : 27,760 ft.
Effective wave height : 1.62 ft.
Sediment sie : <.0.35 mm
h.+B: -___ 2 ft._



48 60 72 84


MONTHS AFTER PLACEMENT


a




































I .- I i -
I I 0 3






"Ii -


C I
/ -= 0



0
wLU ,' / / i Z






/ / "-L
= /ii w-_ =+



I // r


W I I 0 )
CI I
CC0


c I

o 0 0 /.**'










o o o o 0= a


..- .,- O, N C


1l L


I =














Table 4.6: Cumulative Component Percentage of Total Erosion
ELAPSED TIME TOTAL EROSION PERCENTAGE
(months) (CY) background [ spreading
3 87,579 19% 81%
6 130,584 25 75
12 191,199 34 66
24 312,699 42 58
36 418,684 47 53
48 516,529 51 49
60 609,332 54 46


two passes causes significant problems in determining an erosion rate with any confidence.

Wave data from the Clearwater location in the Gulf indicate an average wave height of 1.28

feet.

Initial restoration began with placement of emergency fill on the project site of 120,000

CY following Hurricane Gladys in October of 1968 is the first documented nourishment

attempt. This was followed with 673,000 CY placed from April to July of 1969. This first

project thus consisted of a total of 783,000 CY over a beach segment of 1.7 miles. The

northern limit of this project was more than a mile south of John's Pass which at the time

of improvement had a small southern jetty. The fill material came from offshore and from

the shoals of Blind Pass, with the majority from the offshore site immediately gulfward of

the project, 86%. A median grain size of 0.24 mm was determined from a weighted average

of the three project reports and relates to a k factor of 1.3. The assumption on the west

coast is a (h. + B) value of 15 ft.

A different approach at boundary conditions for this location is required due to the

termination of the barrier island at two passes. The northern end of the island is treated as

an application of a case 2 boundary condition with a zero transport northward of the island

termination. This assumption is based on the beach protruding in the northern reaches of

the island and enclosing O'Brien's Lagoon (Mehta et al., 1976). This effectively causes a no

flow condition. The southern end of the project, northern side of Blind Pass, was armoured








77

with a very short jetty and was improved with a jetty extension in 1976. Effectively the

boundary condition assumed here is a sediment sink into the pass. This is accomplished by

forcing the first grid cell to zero for the duration of the prediction.

The University of Florida performed the monitoring profiles shown in figure 4.28 on

similar lines of the 1969 pre- construction survey performed by the Corps. Results from 15

and 20 months following placement are recorded and are shown along with model predictions

in figure 4.29. The two model predictions are based on different background erosion rates.

Hobson (1981) referenced a background erosion in the nourishment area of 27,000 m3/yr,

equating to 35,300 CY/yr. This is approximated as an average of 3.84 ft/year of erosion.

To study the sensitivity to this approximation, the rate was doubled and the results plotted

alongside the plot labelled "3.84 FT ERO" in figure 4.29.

A volume remaining at 15 months of 546,000 CY is reported comparing to a predic-

tion of 606,407 CY (3.84 ft run) and 579,740 CY (7.68 ft run). At 20 months, the survey

reported 546,500 CY remaining compared to 583,271 CY and 547,715 CY for the two pre-

diction results. The results are encouraging and could possibly indicate a higher background

erosion rate than that previously reported. Uncertainties are introduced however due to the

boundary conditions at the site. Six months after the 20 month survey, a renourishment

of 76,000 CY placed sediment in an are just north of the original northern construction

limits. A second renourishment was completed in 1972 placing 150,000 CY on a 1,400 ft

stretch in the lower limits of the original nourishment area. The multiple nourishments are

not included in the analysis due to the absence of any monitoring data after the 20 month

report of 1971. The extension of the jetty in 1976 creates a boundary condition similar to

either case 2 or case 3. Improved representation of boundary condition applications may

enable an improved performance prediction.

4.2.10 Captiva Island

Captiva Island is a barrier island located off the west coast of Florida approximately

100 miles southeast of Tampa Bay (Figure 4.30). The Lee County island is bounded to








72

36 months. During this period the largest deviation was approximately 40,000 CY with

very close agreement throughout. The average deviation through this period is 29,053 CY

in contrast to the average deviation for the entire 6 years of 196,407 CY. The ability to

predict within 3 years at an error of 29,000 CY is considered highly successful. Correlation

decreases with time past the 3 year period and falls far off with the last survey at 74 months,

showing a difference in volume of 424,000 CY. Also included in figure 4.26 are the analytical

results through the same time period. Very close agreement between the model and analytic

predictions is illustrated through the six year study. The deviation at 74 months is 45,384

CY.

Sensitivity to the background erosion rate is presented in figure 4.27. The 2 ft/yr rate

was used in the results discussed above and is compared here to an increase to 4 ft/yr. A

significant improvement resulted in prediction success. With the 4 ft/yr rate, the standard

deviation decreases to 126,235 CY from 196,407 CY. Therefore, a simple adjustment of 2

ft in erosion along the project baseline improves the prediction "confidence" by 70,000 CY.

This improvement is significant in areas where the erosion rate is undefined. An interesting

approach in analysis is to differentiate between the erosion losses due to background erosion

and those due to spreading out losses. Table 4.2.8 lists the percentages of each along with the

total erosion loss in cubic yards. As expected it is shown that the diffusion loss percentage

will decrease with time for the perturbation of the shoreline is spreading out and erosion is

acting on a straighter and longer shoreline. The associated erosion percentage increase is

misleading. This loss is constant on a yearly basis and is 65,333 CY at Hollywood/Hallandale

yet becomes greater than 50% of the total erosion after only 4 years.

4.2.9 Treasure Island

Treasure Island is located in Pinellas County on a Gulf Coast west of Tampa Bay. The

3.5 mile long barrier island is typical of many west coast barrier island configurations and

is bounded to the north by John's Pass and Blind Pass to the south (figure 4.28). The area

has documented erosion from the mid 1800's to the present; however, the presence of the
















Johns Pass eC







1971 Fill Areal


Boca Ciega
Bay


1969 Fill Area


1972 Fill


Blind Pass


0 Scale 1
Nautical Mile


Figure 4.28: Treasure Island: nourishment project areas and proximity to Blind Pass and
John's Pass.


0C'CO


0-1V
























I III-fSIlr I (HNI MOnH I- fINn SIJHiV Y


111111111010

7500(0

700000

650000

SG0000 -

55(000

3 0000 -

q50000

100000

350000

300000




200000

150000

100000

500(0

0


Project completion date: 7/1969
Initial design volume : 783,000 CY
Project length : 9,000 ft.
Effective wave height : 1.28 ft.
Sediment size : 0.24 tutm
(h. t hi) 15 ft.


12

RFTEH PLfCEMENT 168f I..l;
............... .SURVEY
....... ... .. SURVEY


Figure 4.29: Treasure Island: survey volumes and model prediction through a two year

period.


MO1N IIS







80
the north by Redfish Pass and to the south by Blind Pass. Captiva Island has experienced

high rates of erosion throughout the years with documented erosion rates from as early as

1876. Redfish Pass was formed by a hurricane in 1926 and has remained relatively stable

since that time unlike Blind Pass which has a history of closure and southern migration.

The original nourishment project was completed in October, 1981 with a design volume of

765.M00 CY. Actual placement volume was reportedly greater over the northern 10,000 ft.

of coastline. A short terminal structure was built at the time of the 1981 nourishment. The

original design for the project was based on an average annual sediment erosion rate of 5

CY/'ft/year (Barnett 1988).

The inlet ebb tidal shoal of Redfish Pass provided high quality material and construction

began in July, 1981. A reported median sediment size of Dso = .44 mm results in a k value

of 0.82. Monitoring information was adequate; however, some problems in the use of these

data exist due to nonstandard baseline survey locations. Wave details include an effective

wave height of 1.44 ft. and an average period of 4.7 seconds. Background erosion rates

from DNR range from 1 to 30 feet/year. A long term uniform rate of 3 ft/yr is used in the

modeL

Near inlets such as Redfish Pass which do not have ideal structures, the boundary

conditions are not clearly defined. Here, the large ebb tidal shoal provides a substantial

sheltering effect for particular wave directions. In contrast, Redfish Pass can act as a total

sediment sink. Thus, the appropriate boundary conditions to be used at this site are not

evident. Basically, the boundary condition applied here is one of forcing a zero transport

northward of the project limit. As noted previously, this is equivalent to an effective project

length of twice the actual length, case 2 in figure 2.2. Table 4.2.10 presents the survey dates

and cumulative volumetric changes (erosion (-)).

Figure 4.31 presents a plot of projected model cumulative volume losses against the

ac;zz survey losses in the project area. The correlation through the first 12 months is

outstanding with a deviation of less than 5,000 CY, or less than half of one percent of the










Table 4.7: Captiva Cumulative Volume Change
Months after project Cumulative
completion Volumetric change (CY)
12 -68872
18 -120,560
41 -164,560
46 -109,260
52 -169,760
58 -196,760
65 I -202,075


original volume. An over-prediction of loss by approximately 20,000 CY at 24 months is

followed by a converging loss prediction. At 41 months, a survey calculated loss of 164.500

CY is comparable to a predicted loss of 164,000 CY. Following this high correlation, the

survey of 46 months reflects a significant accretion in the profiles with a gain of over 50,000

CY. This could be explained by profile error due to a varying baseline or by a reflection of

storm recovery due to a short term event. However, the validity of the model is verified from

this time forward ending in a difference of less than 25,000 CY at 65 months, less than 3%

of the original placement volume. These results are certainly encouraging particularly for

the application of "case 2" project boundary conditions. The predicted volume loss remains

a good approximation throughout the life of the project. An overall standard deviation of

31,693 CY results from placement through 65 months. This reflects a prediction ability

capable of error of less than 4% of the original volume.

The lack of accuracy in boundary condition application with the proximity of the natrh-

ern project boundary to the inlet, introduces uncertainties. Also, a high reported shell

content in the pumped sediment could significantly reduce the sediment parameter, k. A

measure of wave height sensitivity, by increasing and decreasing the effective wave height

by 20% resulted in a uniform 3% deviation in prediction results.

A major renourishment is currently underway at Captiva, extending further south than

the 1981 southern construction limit.








77

with a very short jetty and was improved with a jetty extension in 1976. Effectively the

boundary condition assumed here is a sediment sink into the pass. This is accomplished by

forcing the first grid cell to zero for the duration of the prediction.

The University of Florida performed the monitoring profiles shown in figure 4.28 on

similar lines of the 1969 pre- construction survey performed by the Corps. Results from 15

and 20 months following placement are recorded and are shown along with model predictions

in figure 4.29. The two model predictions are based on different background erosion rates.

Hobson (1981) referenced a background erosion in the nourishment area of 27,000 m3/yr,

equating to 35,300 CY/yr. This is approximated as an average of 3.84 ft/year of erosion.

To study the sensitivity to this approximation, the rate was doubled and the results plotted

alongside the plot labelled "3.84 FT ERO" in figure 4.29.

A volume remaining at 15 months of 546,000 CY is reported comparing to a predic-

tion of 606,407 CY (3.84 ft run) and 579,740 CY (7.68 ft run). At 20 months, the survey

reported 546,500 CY remaining compared to 583,271 CY and 547,715 CY for the two pre-

diction results. The results are encouraging and could possibly indicate a higher background

erosion rate than that previously reported. Uncertainties are introduced however due to the

boundary conditions at the site. Six months after the 20 month survey, a renourishment

of 76,000 CY placed sediment in an are just north of the original northern construction

limits. A second renourishment was completed in 1972 placing 150,000 CY on a 1,400 ft

stretch in the lower limits of the original nourishment area. The multiple nourishments are

not included in the analysis due to the absence of any monitoring data after the 20 month

report of 1971. The extension of the jetty in 1976 creates a boundary condition similar to

either case 2 or case 3. Improved representation of boundary condition applications may

enable an improved performance prediction.

4.2.10 Captiva Island

Captiva Island is a barrier island located off the west coast of Florida approximately

100 miles southeast of Tampa Bay (Figure 4.30). The Lee County island is bounded to












































0 7
Sae---------Scale In MIAs







:'a Uimits of Beach Fill
//////f Limits of Borrow Site

1.000 0 1,000

Scale In Yards


Scale In Yards


Figure 4.30: Captiva Island beach nourishment: r:jec: azd borrow area locations.


I



















CRPT IVI PROJ.ILE : MOD(L[ & i-lHVlli YS

MODEL
........ ...........- SUHVET


Project completion date: 11/1981--
Initial design volume: 765,000 CY
Effective wav, height : 1.44 ft.
Sediment sti : 0.44 mnin
(h. + B) : 15ft.









,.-/^ ./


T .. ..- ..
211 3b '11

MONTHS FOI.I.OCIH NG f'PRHI LCI


Figure 4.31: Captiva Island Model and Survey Losses


JbO000 -


250000
200000










150000




111110000




50000 -


12
12




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