• TABLE OF CONTENTS
HIDE
 Front Cover
 Title Page
 Acknowledgement
 Table of Contents
 List of Tables
 List of Figures
 Abstract
 Introduction
 Theory
 Literature review of previous aragonite...
 Laboratory experiments
 Analysis and discussion of laboratory...
 Summary and conclusion
 Beach nourishment experiment survey...
 Sediment transport experiment survey...
 List of references
 Biographical sketch














Group Title: UFLCOEL-2000004
Title: Evaluation of the suitability and efficacy of aragonite sand for beach nourishment
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00091058/00001
 Material Information
Title: Evaluation of the suitability and efficacy of aragonite sand for beach nourishment
Series Title: UFLCOEL-2000004
Physical Description: xii, 148 leaves : ill. ; 28 cm.
Language: English
Creator: Altman, David, 1974-
Publisher: Coastal & Oceanographic Engineering Program, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 2000?
 Subjects
Subject: Beach nourishment -- Florida   ( lcsh )
Sediment transport -- Florida   ( lcsh )
Aragonite -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis (M.S.)--University of Florida, 2000.
Bibliography: Includes bibliographical references (leaves 142-147).
Statement of Responsibility: by David Altman.
 Record Information
Bibliographic ID: UF00091058
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 49506071

Table of Contents
    Front Cover
        Front Cover
    Title Page
        Page i
    Acknowledgement
        Page ii
    Table of Contents
        Page iii
        Page iv
        Page v
    List of Tables
        Page vi
    List of Figures
        Page vii
        Page viii
        Page ix
        Page x
    Abstract
        Page xi
        Page xii
    Introduction
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
    Theory
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
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        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
    Literature review of previous aragonite studies
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
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        Page 56
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        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
    Laboratory experiments
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
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        Page 69
        Page 70
        Page 71
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        Page 73
        Page 74
        Page 75
        Page 76
    Analysis and discussion of laboratory results
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
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        Page 118
        Page 119
    Summary and conclusion
        Page 120
        Page 121
        Page 122
        Page 123
        Page 124
        Page 125
    Beach nourishment experiment survey contour plots
        Page 126
        Page 127
        Page 128
        Page 129
        Page 130
        Page 131
        Page 132
    Sediment transport experiment survey contour plots
        Page 133
        Page 134
        Page 135
        Page 136
        Page 137
        Page 138
        Page 139
        Page 140
        Page 141
    List of references
        Page 142
        Page 143
        Page 144
        Page 145
        Page 146
        Page 147
    Biographical sketch
        Page 148
Full Text



UFL/COEL-2000/004


EVALUATION OF THE SUITABILITY AND EFFICACY
OF ARAGONITE SAND FOR BEACH NOURISHNMENT







by




David Altman




Thesis


2000














EVALUATION OF THE SUITABILITY AND EFFICACY OF ARAGONITE SAND
FOR BEACH NOURISHMENT









By

DAVID ALTMAN


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


2000














ACKNOWLEDGMENTS


I began my studies in the Coastal and Oceanographic Engineering Department at

the University of Florida in August, 1998. First and foremost, I would like to express my

heartfelt thanks to my advisor and supervisory committee chairman, Dr. Robert G. Dean;

his relentless commitment and enthusiasm has been paramount to my success. My thanks

are also extended to Dr. Daniel M. Hanes and Dr. Robert J. Thieke for serving on my

committee and for their support and encouragement throughout the duration of this study.

In addition, I would also like to thank the Office of Beaches and Coastal Systems of the

Florida Department of Environmental Protection for the funding provided for this study.

I would like to extend a most sincere thank you to the staff at the Coastal and

Oceanographic Engineering Laboratory, in particular, Sidney Schofield and Jim Joiner.

The time and effort they each provided are extremely appreciated. In addition, I would like

to thank James MacMahan, Cris Weber, Sean Mulcahy, and Al Browder for their

encouragement and technical assistance during the course of this study.

I would like to extend the warmest of thanks to my parents for their love and

support throughout my college career. They have instilled in me the drive to succeed in all

of my pursuits. Finally, I would like to thank Julie Verona for helping me to realize my

goals in life. Her unwavering love, support, and confidence has been the guiding light in

inspiring me to achieve my aspirations, and has motivated me to strive for new ones.















TABLE OF CONTENTS



ACKNOWLEDGMENTS............................................................................................ii

LIST O F TA B LES...................................................................................................... vi

LIST O F FIGU RES.................................................................................................... vii

A B STR A C T ................................................................................................................ xi

CHAPTERS

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

1.1 General Description..........................................................................................1
1.2 Quantifying Sediment Transport Characteristics............................... ..............3
1.3 Previous Studies of Beach Nourishment Performance........................ ............ 8
1.4 Theoretical Predictions of Beach Nourishment Planform Evolution................ 11
1.5 Scope of This Thesis......................................................................................13

2 THEORY..............................................................................................................15

2.1 Introduction..................................................................................................... 15
2.2 Governing Equations......................................................................................15
2.3 Analytical Solutions.......................................................................................19
2.4 Numerical Solutions.......................................................................................25
2.5 Effects of Fall Velocity on Transport of Aragonite and Quartz Sediment............29
2.5.1 Shape Factor......................................................................................... 30
2.5.2 Determination of A-Values........................ ...........................................31
2.5.3 Specific Gravity.................................................................................31
2.5.4 Including Both Shape Factor and Specific Gravity.................................33

3 LITERATURE REVIEW OF PREVIOUS ARAGONITE STUDIES.....................35

3.1 Introduction.........................................................................................................35
3.2 Composition and Origin of Aragonite................................................................35








3.3 Coastal Engineering Issues........................................................................... 37
3.3.1 Coastal Engineering Properties Relating to Aragonite................................37
3.3.2 Suitability Studies Based on Previous Field and Laboratory Experiments..41
3.3.3 Fisher Island Project.............................................. ............................. 46
3.4 Environm mental Issues....................................................................................... 52
3.4.1 Impacts to Sea Turtles......................................................................... 52
3.4.2 Impacts to Infauna Communities.............................................................55
3.4.3 Implications to the Bahamian Environment.......................................56
3.5 Political Issues................................................................................................57
3.5.1 U.S. Protectionist Legislation............................................................. 57
3.5.2 State and Local Political Concerns.........................................................59
3.5.3 Bahamian Political Issues.................................................................. 59
3.6 Summary and Conclusion............................................................................61

4 LABORATORY EXPERIMENTS.................................................................... 63

4.1 Introduction.....................................................................................................63
4.2 Experimental Equipment...............................................................................64
4.2.1 W ave B asin.......................................................................................... 64
4.2.2 W ave G age........................................................................................... 66
4.2.3 Survey Technique....................................................... .......................67
4.3 Test Preparation and Design......................................................................... 68
4.4 Experimental Procedures..............................................................................70
4.4.1 Beach Nourishment Performance Experiment...................................... 70
4.4.2 Sediment Transport Experiment.............................................................74
4.4.3 Rapid Sand Analyzer Experiment...........................................................75
4 .5 R esults...................................................................................................... ......76

5 ANALYSIS AND DISCUSSION OF LABORATORY RESULTS........................77

5.1 Introduction..................................... ..................... ................................... .. ...........77
5.2 Beach Nourishment Experiment............................................ 77
5.2.1 Shoreline Evolution and Volumetric Density Changes............................78
5.2.2 Average Profile Evolution................................................................. 84
5.2.3 Proportion of Sand Remaining............................ ..... ............88
5.2.4 Quantifying the Sediment Transport Coefficient............................. ..91
5.2.5 Discussion of Beach Nourishment Experiment....................................96
5.3 Sediment Transport Experiment....................... ............................... ...97
5.3.1 Average Profile Evolution...................... ......................................99
5.3.2 Volum etric Density Evolution............................................ ..... .............103
5.3.3 Quantifying the Sediment Transport Rate................................ .. 106
5.3.4 Quantifying the Sediment Transport Coefficient............................... 109
5.4 Rapid Sand Analyzer Experiment............................................................ 111
5.5 Comparison Between Laboratory Experiments............................. ...............117








6 SUMMARY AND CONCLUSION...................................................................120

6.1 Summary of Investigation..........................................................................120
6.2 C onclusions.....................................................................................................121
6.2.1 Beach Nourishment Experiment.............................................................121
6.2.2 Sediment Transport Experiment...........................................................122
6.2.3 Rapid Sand Analyzer Experiment........................................................123
6.3 Suggestions for Future Research........................... ..........................................124

APPENDICES

A BEACH NOURISHMENT EXPERIMENT SURVEY CONTOUR PLOTS..........126

B SEDIMENT TRANSPORT EXPERIMENT SURVEY CONTOUR PLOTS.........133

LIST OF REFEREN CES.........................................................................................142

BIOGRAPHICAL SKETCH..................................................................................148















LIST OF TABLES


able Page

5.1 Percent Remaining After 60 Minute Testing Cycle......................................88

5.2 K Values Obtained Through Theoretical Methods for the Quartz Beach...........10

5.3 K Values Obtained Through Theoretical Methods for the Aragonite Beach.......110

5.4 Summary of Comparative Quartz/Aragonite Grain Size Analysis.....................14

5.5 Shape Factor Effects on Fall Velocity To Determine A Quartz Equivalent......... 115

5.6 Equivalent Quartz Diameter Including Shape Factor and Specific Gravity.........116















LIST OF FIGURES


Figure Page

1.1 Relationship Between the Longshore Component of Wave Energy Flux
and the Immersed Weight of Longshore Transport for both Field and
Laboratory Studies, After Komar and Inman (1970)........................................ 6

2.1 Non-dimensional Shoreline Evolution for a Rectangular Beach
Nourishment Planform, After Dean and Dalrymple (1999)..................................21

2.2 Percentage of Material Remaining in Fill Area Versus Dimensionless
Time, After Dean and Dalrymple (1999).........................................................22

2.3 Initially Trapezoidal Planform on a Long Straight Beach...................................23

2.4 Schematic Diagram for DNRBS Numerical Model, After Dean and
D alrym ple (1999)............................................................................................26

2.5 Definition of Terms Used in the DNRBS Numerical Model Formulation
With Perturbed Contours, After Dean and Yoo (1991).......................................27

2.6 Definition Sketch for Effect of Beach Nourishment on Contours......................28

2.7 Relationship Between Mean Grain Size Diameter and Settling Velocity
For Varying Shape Factors.............................................. ............................. 30

2.8 Relationship Between Drag Coefficient and Reynolds Number.........................32

4.1 Schematic Layout of the Wave Basin and the Initial Test Conditions at
the University of Florida Coastal and Oceanographic Engineering
Laboratory........ ......................................... .....................................................65

4.2 Particle Grain Size Distribution for Quartz Sediment Used Throughout the
Duration of this Study............................................................ .......................66

4.3 Average Equilibrium Beach Profile of the Quartz Sediment..............................68

vii








4.4 Schematic of the Quartz/Aragonite Equilibrium Beach Profile Templates..........69

4.5 Schematic Layout of the Beach Nourishment Performance Experiment
and the Associated Fill Design........................................... .......................... 71

4.6 Sand Size Distribution of Aragonite and Quartz Fill............................................73

4.7 Schematic Layout of the Wave Basin for the Sediment Transport
Experim ent...................................................................................................... 74

5.1 Shoreline Evolution of Quartz Nourishment After 0, 5, 9, 20, 40, and 60
M minutes of W ave A ctivity................................................................................ 78

5.2 Shoreline Evolution ofAragonite Nourishment After 0, 5, 9, 20, 40, and 60
M minutes of W ave Activity................................. ................. ...........................79

5.3 Comparison of Change in Dry Beach Width After 60 Minutes of Wave
Activity for Quartz and Aragonite Test Nourishments.................................80

5.4 Change in Quartz Volumetric Density After 0, 5, 9, 20, 40, and 60 Minutes
of W ave A ctivity............................................................................................. 81

5.5 Change in Aragonite Volumetric Density After 0, 5, 9, 20, 40, and 60
M minutes of W ave A ctivity......................................................................... ... ....82

5.6 Comparison of Loss in Volumetric Density After 60 Minutes of Wave
Activity for Quartz and Aragonite Test Nourishments.................................83

5.7 Quartz Test Nourishment Average Profile Evolution After 0, 5, 9, 20, 40,
and 60 M minutes of W ave Activity........................................................................85

5.8 Aragonite Test Nourishment Average Profile Evolution After 0, 5, 9, 20, 40,
and 60 M minutes of W ave Activity........................... ..........................................86

5.9 Comparison of Average Equilibrated Beach Profile of Aragonite and Quartz
Test Nourishments After 60 Minutes of Wave Activity.....................................87

5.10 Percent Plan Area Remaining Over Time for Aragonite and Quartz Test
Nourishm ent Sections.................................... ................ ...............................89

5.11 Percent Volume Remaining Over Time for Aragonite and Quartz Test
Nourishm ent Sections.................................... ................ ...............................90

5.12 Determination of Sediment Transport Coefficient for Quartz Nourishment
Based on Percent Volume Remaining.................................................................92

viii








5.13 Determination of Sediment Transport Coefficient for Aragonite Nourishment
Based on Percent Volume Remaining................................................................93

5.14 DNRBS Simulation of Equilibrated Shoreline After 0, 5, 10, 20, 40, and 60
Minutes of Wave Activity Based on K Value Obtained (1.47) for Quartz
Nourishment Percent Volume Remaining........................................................94

5.15 DNRBS Simulation of Equilibrated Shoreline After 0, 5, 10, 20, 40, and 60
Minutes of Wave Activity Based on K Value Obtained (1.20) for Aragonite
Nourishment Percent Volume Remaining..........................................................95

5.16 Sediment Transport Experiment Grain Size Distribution for Aragonite and
Q uartz Sands................................................................................................... 98

5.17 Average Profile Evolution of the Quartz Beach After 0, 30, 60, 90, 120, 180,
240, and 360 Minutes of Wave Activity............................................................99

5.18 Average Profile Evolution of the Aragonite Beach After 0, 30, 60, 90, 120, 180,
240, and 360 Minutes of Wave Activity.........................................................100

5.19 Total Average Profile Evolution for the Quartz Beach.....................................101

5.20 Total Average Profile Evolution for the Aragonite Beach................................102

5.21 Volumetric Density Evolution of the Quartz Beach After 0, 30, 60, 90, 120,
180, 240, and 360 Minutes of Wave Activity...............................................104

5.22 Volumetric Density Evolution of the Aragonite Beach After 0, 30, 60, 90, 120,
180, 240, and 360 Minutes of Wave Activity.............................................105

5.23 Longshore Sediment Transport Rate Evolution for the Quartz Test Section......107

5.24 Longshore Sediment Transport Rate Evolution for the Aragonite Test Section.108

5.25 Average Sediment Transport Rate Occurring Over Time for the Quartz and
Aragonite Test Sections................................. ................. ............................109

5.26 Comparison of the Settling Velocities for Varying Sand Diameters of Quartz
Quartz and Aragonite Sediment........................... ...................................113

A.1 Quartz Nourishment Survey Contour Plots After; a) 0 and b) 5 Minutes of
W ave A ctivity................................................................................................127

A.2 Quartz Nourishment Survey Contour Plots After; a) 9 and b) 20 Minutes of
W ave A ctivity................................................................................................128

ix








A.3 Quartz Nourishment Survey Contour Plots After; a) 40 and b) 60 Minutes of
W ave A ctivity...............................................................................................129

A.4 Aragonite Nourishment Survey Contour Plots After; a) 0 and b) 5 Minutes of
W ave A ctivity...............................................................................................130

A.5 Aragonite Nourishment Survey Contour Plots After; a) 9 and b) 20 Minutes of
W ave A ctivity....................................................................................................131

A.6 Aragonite Nourishment Survey Contour Plots After; a) 40 and b) 60 Minutes
of W ave Activity...................................... ..................................... ...... 132

B.1 Quartz Sediment Transport Survey Contour Plots After; a) 0 and b) 30
M minutes of W ave A ctivity................................................................................. 134

B.2 Quartz Sediment Transport Survey Contour Plots After; a) 60 and b) 90
M minutes of W ave Activity..................................................... ..................... 135

B.3 Quartz Sediment Transport Survey Contour Plots After; a) 120 and b) 180
M minutes of W ave A ctivity................................................................................. 136

B.4 Quartz Sediment Transport Survey Contour Plots After; a) 240 and b) 360
Minutes of Wave Activity..........................................................................137

B.5 Aragonite Sediment Transport Survey Contour Plots After; a) 0 and b) 30
Minutes of Wave Activity.................................................................................138

B.6 Aragonite Sediment Transport Survey Contour Plots After; a) 60 and b) 90
M minutes of W ave A ctivity............................................................................... 139

B.7 Aragonite Sediment Transport Survey Contour Plots After; a) 120 and b) 180
M minutes of W ave A ctivity............................................................................... 140

B.8 Aragonite Sediment Transport Survey Contour Plots After; a) 240 and b) 360
M minutes of W ave A ctivity............................................................................... 141















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


EVALUATION OF THE SUITABILITY AND EFFICACY OF ARAGONITE SAND
FOR BEACH NOURISHMENT

By

David Altman

August, 2000


Chairperson: Dr. Robert G. Dean
Major Department: Civil and Coastal Engineering

With the increasingly common use of beach restoration, this study was prompted

by the scarcity of quality offshore borrow areas and increased environmental concerns

associated with offshore dredging, primarily along the South Florida coast, and the possible

use of alternate materials and methods for beach nourishment. Aragonite is formed from

calcium carbonate deposits and exists in abundance approximately 60 miles offshore of

Florida's lower east coast in the Carribean, and is considered an excellent candidate as a

material for beach nourishment.

After conducting an extensive literature review of all pertinent information relating

to previous studies involving the use of aragonite for beach nourishment, a series of

laboratory experiments was designed to compare the evolution and transport characteristics

of quartz and aragonite sediments. The three main experiments discussed in this study

xi








include the beach nourishment experiment, the sediment transport experiment, and the

rapid sand analyzer test.

The results were analyzed using several approaches and revealed that the average

profile, shoreline, and volumetric density equilibration of aragonite nourishments are

comparable with, and somewhat superior to, compatible quartz nourishments. The

proportion of fill material remaining within project limits was determined to be, on average,

10% higher for the aragonite nourishment section. Analysis of the sediment transport

experiment revealed the longshore sediment transport for aragonite was substantially lower

than that for quartz, and the direction of cross-shore sediment transport was found to be

landward for the aragonite and seaward for the quartz test sections, respectively. These

results were attributed primarily to an initial aragonite slope which was considerably milder

than the quartz test section, and increased fall velocities of the aragonite sediment

associated with a slightly larger grain size (0.30 mm) than that of quartz (0.25 mm)

resulting in less suspension times. Based on the settling velocity measurements, aragonite

was determined to perform as a comparable quartz equivalent that is 1.11 times its initial

diameter.

The results of the laboratory experiments conducted during this study demonstrated

that aragonite is comparable to quartz sand and is suitable for future use in beach

nourishment projects. The effectiveness and the ability of aragonite to perform as a

nourishment material has been established and should exceed somewhat the predictions of

nourishments employing comparable quartz fills.















CHAPTER 1
INTRODUCTION



1.1 General Description



The use of beach nourishment materials as a viable resource in stabilizing and

controlling beach erosion is fast becoming the preferred solution in the long term beach

erosion control program in the State of Florida. Beach restoration requires the delivery of

large quantities of good quality sand to the eroded shoreline in a cost effective manner,

while minimizing environmental and social impacts. Typically, in the past, this has been

achieved by either the transfer of sand from: 1) an offshore borrow area or to a much lesser

extent from 2) an inland source. However, in many places in the State of Florida, the

availability of such materials is limited. In areas where there are offshore deposits of

materials, the sediment grain size characteristics may be finer than the native, resulting in

poor nourishment performance. In addition, the dredging of fine grained materials

produces heavy siltation which in turn increases the amount of turbidity in the water. This

can pose a potential threat to nearby coral reefs and other sensitive offshore resources. In

particular, this concern appears to be more prevalent along the South Florida coast, i.e.

Dade and Broward Counties, where the availability of good quality sand has been reduced

and potential environmental impacts are of prime concern.








2

Due to the lack of nearby sand resources for beach nourishment in South Florida,

the possibility of transporting sand from remote areas is considered a feasible solution.

One alternate material which is currently under consideration is aragonite sand. Aragonite,

which exists in large abundance in the Carribean, appears to be of an excellent grain size

distribution and could potentially have other physical characteristics which would make it

a superior material for beach nourishment.

Oolitic aragonite is defined as small, round calcareous grains by the American

Heritage Dictionary (Second Edition). For the purposes of this thesis, the deposits in the

Bahamas and elsewhere will be referred to as either oolitic aragonite or simply aragonite,

although they may contain substantial quantities of shell and coral. Monroe (1969)

describes oolitic aragonite as being composed of pure calcium carbonate crystalized in the

orthorhombic crystal system, exhibiting a smooth, spherical to ellipsoidal shape, and a

distinct nucleus. In addition, the distribution of aragonite sands tends to be moderately to

well sorted, meaning a large proportion of a sand sample would have similar sizes

(Campbell, 1983). Typical quartz sand grains, on the other hand, are of irregular shape and

may have a poorly sorted distribution. In this study the relative effects of the differing

physical characteristics between aragonite and quartz sands on sediment transport and

beach nourishment evolution will be explored.

In December of 1990, construction began on the first full-scale beach restoration

project to utilize imported Bahamian aragonite sand in the United States. Fisher Island,

located in Dade County and situated south of Miami Beach, was the recipient of the

nourishment material. Prior to the nourishment, Fisher Island's 620 meters of shoreline

was chronically eroding at a rate of 4 ft/yr due to the long south jetty of Government Cut








3

which prevented sediment transport from reaching Fisher Island. Studies performed nine

months after construction concluded that the approximately 23,000 m3 of aragonite which

was placed on the shoreline remained within the project area and the shoreline subsequently

stabilized, exhibiting no net retreat. Despite the fact that the use of structures was

employed in the design of this project, the nourishment, in all respects, exceeded

expectations. Characteristically, beach restoration projects performed in a relatively small

project area do not fare well. The main hypotheses behind the success of this project are

threefold, a combination of 1) the structures designed to protect the nearshore seagrass

communities also acted to stabilize and hold the material in place, 2) the aragonite sand is

of superior physical and hydrodynamic characteristics which allow it to maintain a higher

threshold to sediment movement and less time in suspension, and/or 3) some combination

of the two aforementioned hypotheses. The present study will test the relevance of the

second hypothesis in order to obtain a better understanding of the sediment transport

processes associated with aragonite sand.


1.2 Quantifying Sediment Transport Characteristics



Quantifying and comparing the sediment transport associated with aragonite and

comparable quartz sand grains is extremely important in establishing the relative suitability

of aragonite sands for beach nourishment. Sediment transport is defined as the movement

of sediment in the nearshore region. Transport may occur in either the cross-shore

direction, perpendicular to the beach face, or alongshore, parallel to the beach face. The

transport which is directed parallel to shore is known as littoral drift or longshore sediment








4

transport. Littoral drift is due to, in large part, obliquely incident waves. These waves

propagate and shoal towards the coastline at an angle resulting in a current directed

alongshore. When the turbulence of the breaking waves suspends the sediment, the

longshore current carries the suspended sediment downdrift. The durability and life

expectancy of any beach restoration project is improved by the ability of the nourishment

sands to both be more stable in the presence of wave breaking and to minimize suspension

times once incipient motion has occurred. There have been numerous laboratory and field

studies conducted throughout the past century to quantify the sediment transport of quartz

sands in the nearshore ocean environment. Several of these results will be discussed in this

section.

Early efforts to quantify sediment transport relate the amount of longshore energy

flux of a wave, when arriving at the shoreline, as the direct mechanism causing sand

transport. This theory is known as the 'Wave Energy Flux Method'. Perhaps the most

noted study in this area is that of Inman and Bagnold (1963) where they theorized that the

immersed weight longshore sediment transport rate It, in units of energy flux, is directly

related to the longshore energy flux factor PI,, resulting in:


It=KPI, (1.1)



where K is known as the dimensionless sediment transport coefficient. Castanho (1966)

developed a formula for littoral drift including the dual effects of current velocity and

waves. In his representation of the energy flux factor, he includes the influence of wave

steepness at the break point, the ratio of the breaking wave height to the breaking wave








5

length Hb/Lb, beach slope m, and bottom roughness c,. In addition, Castanho (1966)

distinguishes between the transport due to bed load from that due to sediment suspension.

The final formula he proposed for the volumetric littoral transport rate Q, is:


S
Q,- Pt
y,(1 -p)tanO (1.2)



where y, is the submerged specific weight of the sand grains, p is the in-place porosity

usually taken to be as approximately 0.35 for quartz sand grains, 0 is the natural angle of

repose for the sediment, and s is a function dependent upon the three breaker types, i.e.

plunging, spilling, and surging. The immersed weight longshore sediment transport I,, and

the volumetric transport rate Q, are related using the following expression:


'I=Y,(1 -P)Q, (1.3)


which is seen to be of equivalent form to Equation 1.1.

Komar and Inman (1970) simultaneously measured wave parameters and sediment

transport at both El Moreno Beach in Mexico, and Silver Strand Beach on the California

coast. Based on an array of remote sensors placed in the nearshore, detailed measurements

of the direction and magnitude of wave energy flux were obtained. By compiling the data

and comparing the results with those of Watts (1953) and Caldwell (1956) to Equation 1.1,

they found that the field data best represented a value of 0.77 for the sediment transport

coefficient, K. See Figure 1.1.
















SW tIs (1953)
S 10 Coldwell (1956)
E Komor and Inman (1970)
*o El Moreno Beoch <
S Silver Strand Beach "

106

$ i
0 LABORATORY
1 o Krumbein (1944)
Soville (1950)
S3 a Shay and Johnson(1951)
S Sauvoge and Vincent (1954)
So- '"26

i a * b 4. C






Figure 1.1 Relationship Between the Longshore Component of Wave
Energy Flux and the Immersed Weight of Longshore Transport for both
Field and Laboratory Studies, After Komarge and Inman hi(1959-1970)












The variability in the data presented in Figure 1.1 indicates that the use of one

specific number for K may be inappropriate. In actuality, K values can differ by an order

of magnitude. In Figure 1.1, it is evident that the K values obtained through laboratory
studies are significantly lower than those found in the field. Tomlihe reason for this is subject
I ...,&,. I 1 I I I
103 1o4 10s IO6 1o7 1o8 io9
q (ECn)b sin a. cos cc erg/sec cm












to much debate; however, re 1.1 Relatione possibility is an intrinsiween the Longshore Component of Waveta due to

scaling effects. When the model studies are scaled up to prototype size the beach sands

used are usually abormally large (Studies, After Komar and Inman (1970).
The variability in the data presented in Figure 1.1 indicates that the use of one

specific number for K may be inappropriate. In actuality, K values can differ by an order

of magnitude. In Figure 1.1, it is evident that the K values obtained through laboratory

studies are significantly lower than those found in the field. The reason for this is subject

to much debate; however, one possibility is an intrinsic error in the laboratory data due to

scaling effects. When the model studies are scaled up to prototype size the beach sands

used are usually abnormally large (Dean and Dalrymple, 1999).








7

More recent studies of sediment transport were conducted by Dean et al. (1982) and

Kamphuis, Davies, Nairn, and Sayao (1986). Dean et al. (1982) found from studying

various field experiments that there is an inverse relationship of the sediment transport

coefficient, K, with median sediment grain size, D50 Therefore, it may be argued that larger

grain sizes can be associated with a net decrease in sediment transport. Building off this

work Kamphuis et al. (1986) utilized dimensional analysis to determine an energy related

sediment transport expression, resulting in:

7/2
mHbs
Q,=1.28 sin2a (1.4)
Dso

In this formula the sediment transport Q, in kg/s, is related to the breaking wave height Hbs,

breaking wave angle abs, beach slope m defined as the ratio of depth of breaking over the

distance from the still water shoreline to the breakpoint, and the constant (1.28) is related

to the S.I.. system and assumes salt water. From this expression, the sediment transport

coefficient is calculated by:


0.01y112mH
DK 0 Hb]K (1.5)
D50



where K is taken to be the constant of 0.77 after Figure 1.1. In 1991, Kamphuis modified

Equation 1.4 was to:


Q ,=2.27 2 1.5 075 -0.25 06^2
Q,==2.27HTP'/ Mb, D50 sin 2ab,


(1.6)








8

Here the influence of the wave period T, is included. This more recent representation of

Equation 1.4 is based on an extensive, coherent set of laboratory experimental data. This

expression has been found to correctly predict sediment transport over a wide range of

grain sizes and for various field studies. Kamphuis (1991) found the scale effects for

determining sediment transport to be rather small since the laboratory effects of beach

slopes and grain sizes have a tendency to cancel each other out; however, aragonite is

known to have differing hydraulic characteristics than quartz. The extent to which these

new hydraulic characteristics would affect flow separation in the boundary layer of the

smooth spherical particles has not been investigated as of yet. As a result, scaling effects

associated with aragonite in the laboratory are expected, but the magnitudes are unknown

at this time.


1.3 Previous Studies of Beach Nourishment Performance



Beach Nourishment is defined as the placement of large quantities of good quality

sand on the foreshore and nearshore regions of a beach to advance the shoreline seaward.

With decreasing usage of stabilizing structures, such as jetties and groins, beach restoration

is fast becoming the method of choice to address chronic erosion problems on the

coastlines. The earliest documented beach nourishment project was constructed in 1922

in Coney Island, New York. From 1922 to 1950 approximately 71 more projects were

constructed in the United States. However, due to relatively little to no monitoring studies

of these projects, limited knowledge was gained. A detailed overview of each project and

its performance may be found in Hall (1952). This section is intended to address the








9

conclusions regarding basic nourishment parameters with respect to sand characteristics

and placement region established over the past 50 years of beach nourishment.

In 1968, Berg and Duane studied the effects of particle size and distribution on the

stability of an artificially filled beach along a recurved spit on the northern shore of Lake

Erie, Pennsylvania. This was a small scale project, approximately 1000 feet in length,

nourished with 17,000 cubic yards of sediment which was coarser than the native sands.

Prior to the nourishment, the Peninsula was migrating downdrift and the shoreline was

retreating landward at a rapid rate, resulting in a loss of high value property. The beach

restoration project was commissioned in an attempt to either slow down or halt these

processes. As a result of their monitoring studies, Berg and Duane (1968) found that the

nourished region underwent minimal material loss and maintained a relatively stable

profile. On the basis of these findings several conclusions were made. First, beaches

composed of coarse sediment are more stable over time and tend to exhibit a decrease in

erosion rates. Therefore, nourishing a beach with sediment with larger grain sizes than

those existing on the beach results in a decrease in the erosion rate and a more stable

profile. More recently, this finding has been investigated by Dean and Yoo (1992) and

Donahue (1998), where they were able to both substantiate and, to some extent, quantify

the positive effects of utilizing fill sand coarser than the native. Although these theories

have withstood the test of time, and are widely accepted today, the effects of changing the

hydraulic and physical characteristics of the sediment, while maintaining a uniform grain

size distribution, on beach nourishment has not been studied adequately.

The performance of a beach nourishment project based on placement location has

also been an area of interest. For the most part, beach nourishments are placed on the








10

foreshore from the berm to a designated specification for initial dry beach width and then

tapered seaward in the cross-shore direction until the nourishment toe meets the natural

bathymetry. Typically, the initial placement geometry is steeper than the equilibrium

profile, resulting in a reduction of dry beach width during the equilibration and stabilization

process. Obviously, aesthetically speaking, most clients and beach patrons would prefer

to see the nourishment on the dry beach; however, there has been a considerable amount

of time and effort devoted to the study of profile or "mound" nourishment. Profile

nourishment is the placement of sand in the nearshore at some specified depth, within the

active profile, with the hopes that through the constructive forces of wave action, the placed

sand will eventually migrate landward and stabilize on the foreshore. Hall and Herron

(1950), Browder and Dean (1997), Otay (1994), and Hands and Allison (1991) all studied

the migration patterns of underwater sea mounds. Although Hall and Herron (1950) and

Browder and Dean (1997) found no significant migration either landward or seaward of the

sea mounds, Hands and Allison (1991) studied several mounds ranging in depth from 2.1

to 21.3 meters and were able to identify some movement characteristics. There findings

indicated that sea mounds located in shallower depths in the nearshore have a significantly

better chance of migrating landward than those located further offshore; however, the

benefits associated with profile nourishment could not be quantitatively identified. To date,

standard industry practice is to nourish the foreshore and allow for a recession due to

equilibration in the design, rather than nourish the profile in the hopes that the material will

eventually result in an additional dry beach width. One advantage of offshore placement

is that sands of lesser quality may be employed resulting in decreased project costs.










1.4 Theoretical Predictions of Beach Nourishment Planform Evolution



A number of investigators have studied the evolution of beach nourishment projects

in order to develop predictive techniques for the evolution and longevity of the project.

Most notably, Pelnard-Considere (1956) applied the heat conduction equation to develop

a one-line analytical planform model to describe the diffusive processes of beach

nourishments. The heat conduction equation can be expressed as:


dy G d2y
dt dx2 (1.7)



where y is the cross-shore coordinate to the anomalous beach, x is the longshore coordinate,

t is time, and G is known as the longshore diffusivity coefficient and is defined as:


KH5/2g
8(s -1)(1 -p)(h,+B) (8)



where K is the sediment transport coefficient shown in Figure 1.1, Hb is the breaking wave

height, g is the acceleration of gravity, K is the ratio of breaking wave height to water depth,

s is the specific gravity of the nourished material, p is the porosity, h. is the depth of

closure, and B is the berm height. Dean (1983) found, on the basis of Equation 1.7 and

Equation 1.8, that the longevity (t), or the expected life span, of any beach nourishment can

be expressed as:











toc-
H5/K (1.9)



where 1 represents the total length of the project area. Equation 1.9 basically states that the

performance of any project increases rapidly with an increase in project length.

Inspecting Equation 1.8, it is evident from the s and p terms that the hydraulic

characteristics of the nourishment sands have a direct relationship to the diffusive

characteristics of the nourishment. The grain size characteristics are also related to the

diffusive nature of the nourishment and, as stated earlier, are a function of the sediment

transport coefficient. Beach nourishment predictions on the basis of sediment compatibility

have been investigated by Krumbein and James (1965), James (1974), and Dean (1974) and

a brief explanation of their findings will be offered in this section; however, previous

studies on the effectiveness of beach nourishment on the basis of varying the hydraulic

components of the sediment are limited.

Krumbein and James (1965) presented a method to compare the fill material with

the native material through the respective log-normal grain size distributions in 4 units.

They defined the relative compatibility of nourishment material on the basis of the percent

of the borrow material which was common to the native sands. This approach is reasonable

in that it neglects the finer fraction of the borrow material which may eventually be washed

offshore; however, their method neglects the coarser borrow material which is larger than

the native sands. Based on this work Dean (1974) adjusted the sediment distributions to

account for the benefits associated with coarser than native material, and developed an

overfill factor, K, to represent the amount of fill material required in cubic meters to be








13

placed on a beach to be equivalent to one cubic meter of native sands. Therefore,

minimizing the proportion of fine sands in the fill material and maximizing the coarser than

native sands will ultimately result in a decrease in the overfill factor keeping project costs

to a minimum. James (1974) developed a numerical comparison of the borrow material to

determine if the overfill ratio would result in either a stable or unstable beach. In addition,

James (1974) predicted relative retreat rates of the nourishment based on his stability

criterion. As stated earlier, it is widely accepted today throughout the field of coastal

engineering that the evolution and associated benefits of beach nourishment projects are

directly related to the compatibility and suitability of the fill material.


1.5 Scope of This Thesis



The goal of this thesis is to investigate and qualify the effectiveness and hydraulic

suitability of utilizing aragonite sand for beach nourishment. A basic overview of the

concepts associated with sediment transport and beach nourishment performance and

evolution has been detailed within this chapter. Chapter 2 reviews existing theory

including the governing equations and the analytical and numerical solutions which will

be employed during the analysis section of this report. In addition, this chapter will include

a further investigation into the effects of fall velocity on sediment transport. Chapter 3 will

provide an extensive literature survey of previous applications and studies of aragonite in

the field of coastal engineering. An outline of the experimental apparatus, procedures, and

test conditions applied in the laboratory will be presented in Chapter 4. Chapter 5 will

address the results based on the findings in Chapter 4 and will include a brief discussion








14

on all pertinent information found herein. Chapter 6 concludes and summarizes the study,

and identifies potential areas of future research.















CHAPTER 2
THEORY



2.1 Introduction



This chapter presents the various theoretical concepts which will be utilized to both

implement and analyze all laboratory testing procedures throughout this study. Section 2.2

of this chapter presents the governing equations related to equilibrium profile geometry and

conservation of sand. Furthermore, how these solutions may be applied to planform and

beach nourishment evolution through sediment transport analysis will also be discussed.

Sections 2.3 and 2.4 of this chapter address both the analytical and numerical solutions for

beach nourishment evolution under wave action, respectively. The final section of this

chapter examines the effects of fall velocity on transport of aragonite and quartz sediment.


2.2 Governing Equations



The basis for all equations governing the planform evolution of both regular and

nourished shorelines includes the concept of an equilibrium beach profile. A profile is the

cross sectional shape of a beach as it would look peering across the beach face. Typically,

profiles are represented as a line in two dimensions with the elevation, displayed as the

elevation difference from mean water to the bed, plotted versus the cross-shore distance,

15








16

directed positive offshore. A profile which is said to be in equilibrium is one in which the

shape of the beach has reached a quasi uniform state as a direct result of the natural forces

acting on the sand comprising the beach. Bruun (1954) and Dean (1977) studied various

beach profiles along the coastal United States and Denmark and found an appropriate

representation of a natural equilibrium beach profile of the form:


h(y) =Ay2/3 (2.1)


where h is the depth of the water at any cross-shore position, y, (taken positive seaward),

and A is the non-dimensional profile scale parameter based on sediment size or fall

velocity. Although this equation has limitations, most notably in representing bars, for the

most part, it has been proven and is widely accepted throughout the field of coastal

engineering as an acceptable description of equilibrium beach profiles.

One assumption which is usually made to aid in the formulation of sediment

transport along beach systems is that cross-shore equilibration of the beach profile occurs

rather rapidly, allowing the bulk of effort in examining evolution scenarios to be focused

on the longshore direction. As a result, the three dimensional problem is simplified and the

scope to investigate the transport associated with planform evolution is lessened. The next

step in the formulation of planform evolution is the conservation of sand equation, or

commonly referred to as the continuity equation. The continuity equation is:


dV_ dQ (2.2)
dt dx


where V denotes the volume density, the volume per unit width of beach, and Q is the net








17

longshore transport. By assuming both equilibrium beach profiles and the conservation of

sediment in the system, a one-line relationship is established between the change in the

shoreline position and the change in volume for each profile, as follows:


ddy (h, +B) (2.3)
dt dt


By canceling out the time dependence on the left and right side of Equation 2.3 and

substituting into Equation 2.2, the change in shoreline position may be represented as a

function of the gradient in transport, as follows:


1dQ
Ay = I dO At
(h, +B) dx (2.4)



where in this case Q is taken to be positive to the right as an observer looks seaward.

Therefore a positive gradient in transport will result in a loss of dry beach width while the

form of the beach profile is maintained constant. On the other hand, a negative gradient

in transport will result in a deposition on the beach face while again maintaining the form

of the beach profile.

Referring to Chapter 1, the transport rate Q has been studied and characterized in

many ways. For purposes of this study, all sediment transport will be expressed in terms

of deep water wave characteristics. By first representing the transport rate as a function of

the breaking wave conditions, assuming straight and parallel contours, and neglecting

energy losses in deep water this transformation may be completed as follows after Dean

and Dalrymple (1999):











K(EC cossinO)b

pg(s-)(1 -p) (2.5)



where b denotes breaking wave conditions. Applying the conservation of energy equation

and Snell's law to rewrite the breaking conditions in terms of deep water conditions we

have:


(ECgCosO)b =(ECgcos) 0 (2.6)


and


sinO =sinO
Cb C (2.7)



where 'o' denotes deep water wave conditions, 0 represents the approaching wave angle,

and C is the wave celerity. In order to express the remaining Cb term in the form of deep

water conditions, various shallow water limits may be applied: Cb = (g h1b)2, Hb = K h, and

Lo = gT2/27 to obtain the depth of breaking, hb. By reinserting this expression into the

equation for Cb:


H0TcosQog3 0.2
Cb=( ) (2.8)
47ncos6bK2




Approximating the cosine of the breaking wave angle to be unity, the final transport

equation based solely on deep water wave conditions is:











KH2.4 0.6T0.2cos1.20 sio
Q 0 0 (2.9)
8(s-1)(1 -p)21.40.2K0.4 (2.9)


The Pelnard-Considere (1956) heat conduction equation, Equation 1.7, is obtained by

assuming small shoreline orientation changes in Equation 2.5 or Equation 2.9 and

combining the result with the continuity equation yields an approximate relationship

between the gradient in transport and the longshore diffusivity G, as follows:




dQ d 2y
Q--G(h,+B)
dx dx2 (2.10)



where G is defined in Equation 1.8. The governing equations presented in this section will

provide the reader with the necessary background to understanding the various analytical

and numerical solutions for beach nourishment and planform evolution, due to sediment

transport, presented in the next two sections of this chapter, respectively.


2.3 Analytical Solutions



Commencing with the governing equations established in the preceding section,

namely the Pelnard-Considere equation, various analytical solutions can be applied to

examine the efficacy and evolution of both a rectangular beach fill design and a trapezoidal

beach fill design, which is essentially a rectangular design including end tapers. Since most

beach nourishment projects may be approximated by a rectangular design, the linear








20

solution to Equation 1.7 becomes the superposition of many point solutions throughout the

length of the project area. The solution for the change in shoreline position of an initially

rectangular nourishment project as a function of longshore position x, and time t, becomes:

Y 1 2x 1 2x
y(x,t) =-(erf[ (- +1)]-erf -(--1)]) (2.11)
2 4G l 4Gt


where 1 and Y are the initial project length and width of the project, respectively and 'erf

[]' is known as the error function and is defined as:




erf(z) f e U du (2.12)




where u is considered to be a dummy of integration. For a normal rectangular beach

nourishment with no structures present, the solution can be shown to be symmetric about

the centroid of the nourished area. A diagram demonstrating the shoreline evolution for

a rectangular planform over a non-dimensional time period may be seen in Figure 2.1.

















1 = 1.0
: \\
\\
S = 4.0 \



S= 16.0
---- =160


t =0
-t =0.04
S,-t 0.11


fZ


Note:
, Shoreline Positions are
Symmetric About x/(//2) = 0

--~-- --:-

\ "" -- .I-


0 1 2 3
x/(f/2)
Figure 2.1 Non-dimensional Shoreline Evolution for a Rectangular Beach
Nourishment Planform, After Dean and Dalrymple (1999)


By evaluating the solution for a rectangular planform given in Equation 2.11, it is possible

to obtain an analytical expression for the expected longevity of the project. For this

specified case the proportion of sand M(t), remaining within the project area may be

represented as:




M(=t) -12y(x,t)dy (2.13)
M't










Integrating this yields:



M(t)= ( -(e 1)+erf(llA)
IM = (2.14)



This solution is presented in Figure 2.2 where the proportion of fill, M(t), remaining is

plotted versus dimensionless time, (Gt)/12/1.



i/tle
Y 1.0 0 5 1.0
8 t=Time After Placement Ayo
Sa- G=Along shore Diffusivity Initial
Asymplote11 Fi
S 0.5- "-- M '2 "'t Planform :



a. 0 1 2 3 4 5 6

Figure 2.2 Percentage of Material Remaining in Fill Area Versus
Dimensionless Time, After Dean and Dalrymple (1999)






From Figures 2.1 and 2.2 it is clear that initially there is a large net loss to the original

rectangular planform, resulting in a decrease in the designed dry beach width; however, the

loss rate reduces over time resulting in an average lower loss rate over the project life.

The Pelnard-Considere (1956) equation may also be applied to an initial trapezoidal

planform on a long straight beach. As stated earlier and as illustrated in Figure 2.3, a

trapezoidal nourishment is an initially rectangular planform with end tapers placed at both

longshore limits of the project area.
















-b 0 a b x
Figure 2.3 Initially Trapezoidal Planform on a
Long Straight Beach





The analytical solution for the planform evolution of the trapezoidal beach fill is given by

Walton (1994) as:


Y
y(x,t) = [(A -AX)erf(AX-A) -(A +AX)er/(AX+A)
2(B-A)


(2.15)


+(B +AX)erf(AX+B) -(B -AX)erf(AX-B)

+ 2-[e -(A 2+B2)cosh(2AXB) e -( 22+A2)cosh(2A 2X)]]






where A = a/2(Gt)/2; B = b/2(Gt)1/2; X=x/a



Similar to the methodology used with the rectangular planform geometry, a solution to

determine the proportion of material remaining, M(t), within the project area may be

obtained,


1 1
141, 1











M(t) 1[erf(AX+A) -erf(AX-A)]
2 (2.16)

+1 B-AX)[erf(AX-A) -erflAX-B)]
2 B-A

+--( )[erf(AX-A) -erf(AX+B)]
2 B-A
1 B+AX
+-( )[erA(AX+A) -er/(AX+B)]
2 B-A


+ -exp[-(AX-B)2] -exp[-(AX-A)2]
21\F(B -A)


+ -exp[ -(AX+B)2] -exp[-(AX+A)2]
2 (B -A)



where A, B, and X are defined as above.

The solution to Equation 2.16 is similar to that of Equation 2.14; however, the effects of

the tapered ends result in an increase in the longevity of the nourishment project.

The rate at which a beach nourishment project spreads is directly related to the

longshore diffusivity term G, and the inverse of the square of the project length 1. For the

case of a rectangular nourishment it may be shown, via Figure 2.2, that the half-life, M(t)

= 0.5, of any given project occurs for a dimensionless time term of 0.46. Therefore, a half-

life t0o, can be defined as:


12 12
ts5=(0.46)2 =0.21-
G G (2.17)



All analytical solutions show that the determination of the efficacy of a beach nourishment

project is dominantly due to the project length, 1. Since most nourishment projects are








25

designed for a given length of beach, this parameter usually remains somewhat fixed.

Building off of this concept, for the purposes of this study, the project length of all

laboratory experiments will remain constant while a determination is made as to how

utilizing aragonite versus quartz sediment affects the longshore diffusivity term and

ultimately changes the longevity and the efficacy of a nourishment project.


2.4 Numerical Solutions



Various numerical models have been developed to predict the planform evolution

of beach nourishment projects. In this section, the rationale and solution for the DNRBS

(Department of Natural Resources, Beaches and Shores) model will be employed.

Although there are many models of greater complexity, this program is the main predictive

technique used throughout the duration of this study. Therefore, this model will be

described in greater detail, rather than describe other models which are not used in this

investigation.

The DNRBS model developed by Dean and Grant (1989) is a one line model which

is based on the diffusion equation and incorporates both the sediment transport equation

and the continuity equation. A schematic diagram of the setup for the numerical model is

presented in Figure 2.4. Figure 2.4 shows each grid cell location with the transport

quantities, Q,, defined at the grid lines and the nourishment shoreline displacement, y,

defined at the grid mid-points. The transport and continuity equations are then solved

explicitly as follows. The y values are considered to be fixed while the Q values are

calculated as:












i+1
QI =Cqjsif2(P" -ccX)








KHbq gi1
16s- )I p


(2.18)


(2.19)


(2.20)


S=p---tan-(,i -Y(-))
2 Ax









N









Reference Baseline
For Shoreline \


Figure 2.4 Schematic Diagram for DNRBS Numerical Model,
After Dean and Dalrymple (1999)


where









27

where the terms in Equation 2.18 through 2.20 are defined in Figure 2.5. Figure 2.6

demonstrates the pre-and-post nourishment profiles.


North


\ -I

Shoreline
i








A

Region Influenced
by Beach Nourishment










x


hzh*
I hihh


Deep Water
Contour
N

' o'


Figure 2.5 Definition of Terms Used in the DNRBS Numerical Model
Formulation with Perturbed Contours, After Dean and Yoo (1991)

















b) Profile Through A-A

Figure 2.6 Definition Sketch for Effect of Beach Nourishment on
Contours






The subscripts in Equations 2.18 through 2.20 signify the grid locale while the superscripts

are indicative of the time increment of wave activity, corresponding to t = nAt. The next

step in the formulation is to update all Q`+1 values and hold them fixed while the new y

values are calculated as follows:


n+l n At n+1 n+
YA =Yti (Qi+l -Q 1
Ax(h, +B) (2.21)



The stability criterion for this explicit method of solution is expressed in terms of the time

step, At. This requires that the time step used in the program satisfy the following:


At< 2 (2.22)
2G


where G is defined in Equation 1.8.

Of course, as with all numerical models, appropriate boundary conditions must be

set, namely: number and length of structures, long open coastline or a small island-like








29

coastline bordered by two inlets, or some combination of the aforementioned situations

which requires the formulation of adequate boundary and initial conditions. All of the

testing procedures and pertinent boundary conditions associated with predicting the

planform evolution using DNRBS will be described further in Chapter 4 of this report.



2.5 Effects of Fall Velocity on Transport of Aragonite and Quartz Sediment



The settling velocity, op is the maximum speed that a particle can fall in a fluid

under the action of gravity. This is an extremely relevant parameter in determining the

effectiveness of potential nourishment materials because the amount of sediment suspended

in a water column is directly dependent on the settling velocity. The faster a material can

settle under the forces of wave activity and gravity, the less likely the sediment is to be

transported by the dominant longshore and cross-shore currents, resulting in a net reduction

in transport and erosion in the area in question. The theoretical concepts examined in this

section consider the settling velocity as a function of two parameters. The first is the actual

shape of the sediment and will be discussed in terms of the sediment shape factor after

Vanoni (1975). The second is the ratios of the specific gravities of the respective sediments

which is based on the work conducted by Rouse (1937). Once these parameters are

quantified, the determination of the associated A-values can be calculated through the

relationship found by Dean (1987; 1999) and used to determine an equivalent quartz

diameter for aragonite sediment.









30

2.5.1 Shape Factor

The shape factor of a given sediment refers to the relative sphericity of the material.

For example a sediment with a shape factor (s.f.) of 1.0 would be a perfect sphere, while

an s.f. of 0.5 would be indicative of an irregular shaped grain. Figure 2.7, after work

conducted by Vanoni (1975), demonstrates the relationship between mean grain size

diameter, shape factor, and settling velocity for naturally worn quartz sand particles falling

in distilled water at varying temperatures. Investigation of Figure 2.7 demonstrates that an

increase in the shape factor, results in an increase in the settling velocities.












0. i- --- -i -----*------- --- -- ----------- __



Shpe actor 0.

0 1 0, 10 SO 1
h l~,t Shl.* C O ,0

Figure 2.7 Relationship Between Mean Grain Size Daimeter and
Settling Velocity for Varying Shape Factors







This phenomenon is due to the fact that the drag coefficient is higher for irregularly shaped

grains which maintains them suspended in the water column for longer periods of time than

a uniform spherical particle. Since aragonite is known to be fairly uniform and spherical








31

in shape, first it is assumed that the specific gravities of both substances is the same, and

Figure 2.7 is used to calculate the settling velocities for quartz particles which have a shape

factor which is 0.9 or nearly spherical. By allowing these velocities to be comparable to

those consistent with aragonite, an equivalent quartz grain size may be calculated and

normalized in order to determine the percentage increase due to shape factor alone.

2.5.2 Determination of A-Values

The determination of the associated A-values may be calculated through the

relationship found by Dean (1987; 1999) which relates the sediment profile scale

parameter, A, to the settling velocity,

0.44
A =0.0670f4 (2.23)


This relationship has been utilized to calculate the profile scale factor for nearly spherical

quartz grains after determining the settling velocity. Once the A-value has been determined

the associated mean diameter can be found by linearly interpolating the "Summary of

RecommendedA Values (m 13)" found in Dean (1999). By normalizing the mean diameters

to aragonite, the percentage increase of the diameters based on the shape factor, % ., may

be calculated.

2.5.3 Specific Gravity

The specific gravity of quartz sands is approximately 2.65, while the average of the

various specific gravities for aragonite, based on published results, is 2.90. Specific gravity

is defined as the ratio of the density of a substance divided by the density of water.

Therefore, the greater relative density of aragonite should result in both an increase in

settling velocities and an increase and an associated ability to withstand the motion induced









32

by currents. This can be explored further through the investigation of Figure 2.8, after

work conducted by Rouse (1937), which is a plot of the resistance (drag) coefficient versus

Reynolds Number.





-, 1 I I I 1 I I I I .111 1 -I -.
. i i l /


.. j --.-, -. _--- -



i :t s ; ,i i i i ; --ii.2 1

i.. I.. I---
I i" :* i i s I!_ "- ^- 1



Figure 2.8 Relationship Between Drag Coefficient and Reynolds
Number







The drag force FD, and the immersed weight of the assumed spherical sediment particle Ws,

are:


C 2
Cpxd2 o (2.24)
FD=------



and



W, =(p,-p)g d (2.25)
6








33

Equating Equation 2.24 and Equation 2.25 and solving for settling velocity, of, yields:





( (-)gd (2.26)
W_ 4 p
3 CD



Assuming the drag coefficient, CD, to be the same for quartz and aragonite sands, the ratio

of the settling velocities may be written in terms of their respective specific gravities:


0y p -1
O p-1 (2.27)
1 P, 1




Letting pa=2.90 and p,=2.65 yields:



-1.08 (2.28)



2.5.4 Including Both Shape Factor and Specific Gravity

Multiplying the percentage change in equivalent diameter due to specific gravity

by the percentage change due to the shape factor (i.e. CD) will yield the total percentage

change of the equivalent diameter. For example, defining the normalized quartz grain

diameter for aragonite as the percentage change due to the shape factor alone, %,,, (which

assumed constant specific gravity), then,











%totar=%s.%.g. (2.29)


substituting,


totala =(1.12)(1.08)=1.21 (2.30)



or the equivalent calculated quartz diameter is 1.21 times that of the original aragonite

median diameter.

The applications of calculating an aragonite/quartz equivalent grain size is twofold.

First, quantifying a quartz equivalent grain size, provides a better overall understanding as

to the predictive nature of the evolution of an aragonite nourished project. Most previous

studies of beach nourishment performance have been carried out on quartz sand beaches,

thus yielding considerable knowledge. Therefore, an aragonite/quartz equivalent enables

researchers to apply the lessons learned in previous studies. Second, the process of

identifying the settling velocities of aragonite and quartz sands of a compatible grain size

will yield some insight into the different hydrodynamic characteristics between the two

sediments and will allow for better performance predictions. The next chapter in this report

will discuss all of the characteristics of aragonite sand and will include some previous

studies which have been performed with the material to attempt to quantify the potential

benefits, if any, of utilizing aragonite sand for fill material.















CHAPTER 3
LITERATURE REVIEW OF PREVIOUS ARAGONITE STUDIES



3.1 Introduction



The scarcity of nearshore nourishment materials, increased dredging costs, and a

growing concern for environmental impacts caused by beach restoration has prompted this

study to determine the potential use of aragonite sand as an effective alternative for beach

nourishment material. The purpose of this chapter is to provide a comprehensive review

of pertinent literature regarding the use of aragonite sand for beach nourishment. This

survey will include all information relating the engineering, environmental, and political

issues regarding the utilization and implementation of aragonite sand for beach restoration,

as well documenting previously examined field studies and nourishment projects.


3.2 Composition and Origin of Aragonite



As stated earlier in Chapter 1, Monroe (1969) describes oolitic aragonite as being

composed of pure calcium carbonate crystalized in the orthorhombic crystal system,

exhibiting a smooth, spherical to ellipsoidal shape, and a distinct nucleus. Although the

formation of oolitic aragonite is uncertain, several theories have been advanced. The

organic theory suggests that aragonite originates through the precipitation of calcium

35








36

carbonate from seawater during periods of increased bacteriological activity. The

occurrence of shell and shell fragments of various marine pelecypods and gastropods along

with fragments of tubes made by burrowing marine worms known as Chaetopterus found

in aragonite deposits tends to lend credence to this hypothesis (Monroe, 1969). Traditional

inorganic theory suggests that aragonite forms where colder oceanic waters flow onto warm

shallow waters precipitating the calcium carbonate around nuclei of various sorts (Monroe,

1969). This theory is also plausible considering that these conditions exist over the

Bahama Banks, where extensive deposits of oolitic aragonite are found. Typically, these

Bahamian deposits are generally made up of smooth, rounded, moderately sorted particles

(CPE, 1997; USACE, 1987).

Deposits containing approximately 40-75 billion cubic yards of aragonite, located

50 miles from Miami, Florida, have been leased by the Bahamian government to Marcona

Ocean Industries since the 1960's. Marcona constructed an eighty-five acre island, Ocean

Cay, as their base of operations, and promptly began commercially mining the aragonite

(Slatton, 1986). The operations at Ocean Cay consist of dredging the material with a

cutterhead suction dredge, screening for rocks and impurities, stockpiling on Ocean Cay,

and eventually loading and transporting the aragonite by ship to the U.S. mainland, where

Marcona has holdings at various ports along the Florida coast (Steve Dowd-Marcona

representative, personal communication, 1999). Although the use of aragonite for beach

restoration has been limited, it is widely employed in various industrial applications,

including the manufacture of Portland cement and glass, agricultural lime, a filtration

media, fine aggregate, flue gas desulferization, and as an additive for animal and poultry

feed (Slatton, 1986).










3.3 Coastal Engineering Issues



Although aragonite has been proven to possess numerous beneficial qualities and

uses to the industrial field, the use of Bahamian aragonite for purposes of beach

nourishment is limited. This section will explore the engineering issues regarding oolitic

aragonite and its potential to perform as a quality beach nourishment material. This will

include a discussion of the coastal engineering properties of aragonite and its suitability to

perform as a nourishment material based on previous laboratory and field studies. In

addition, this section will incorporate a review of the Fisher Island project, which to date

is the only beach nourishment project in Florida to employ the use of oolitic aragonite sand.


3.3.1 Coastal Engineering Properties Relating to Aragonite

There are several advantageous characteristics aragonite possesses which lead to its

consideration of the sediment as a beach nourishment material. These properties will be

detailed in the following section.

Grain Size

The average grain size of aragonite sand is generally larger than that of quartz sand,

native to Florida beaches. Average aragonite grain sizes are approximately 0.30 mm, while

quartz sand is usually in the vicinity of 0.20 mm for most South Florida beach sands and

fill materials (Cunningham, 1966). Although data which explicitly relate grain size with

beach face slope of aragonite beaches are not available, this increase in grain size will

provide a steeper, more stable slope, and accompanying foreshore, when placed on a beach

composed of finer grained material. Settling tube analyses indicate that aragonite behaves








38

as a hydraulically coarser material than quartz grains of equivalent geometric size

(Campbell, 1983). Further studies suggest that aragonite performs as quartz sand with an

equivalent grain size which is 1.36 times coarser than that measured by sieve analysis

(Olsen and Bodge, 1991). Coarser sediments tend to either be able to withstand the

destructive forces to a greater extent than finer grained sands, or the constructive forces

have a larger positive effect (Dean, 1999). This has been documented by the Beach Erosion

Board in 1933, which found steeper New Jersey beaches were comprised of coarser grained

materials, and was subsequently observed by Bascom (1951), who positively correlated

beach face slope with grain size for California beaches. On the basis of this parameter

alone, less volume of beach fill is needed to provide a desired design dry beach width of

a nourishment project, ultimately, reducing construction costs (Slatton, 1986).

Grain Shape

As stated earlier, aragonite is generally smoother and more rounded to elliptical in

shape than quartz sand. This higher sphericity has been expected to result in less sediment

transport based on settling velocity. To date, measurements of sand shape are not included

in coastal engineering analyses due to the difficulties in predicting the transport of sand;

however, through a qualitative assessment, it is evident that a more angular sediment (such

as quartz) will encounter more friction after suspension, causing it to settle slower than a

smooth rounded material (such as aragonite). Obviously, the associated transport should

also be increased because the longer a sediment remains in suspension the further the sand

grain is displaced (Dean, 1999). Therefore, according to this theory, aragonite should

experience less time in free suspension, which should reduce the transport rates.










Specific Gravity

The specific gravity of oolitic aragonite Bahamian sands has an average value of

2.90 (ranging from 2.88 to 2.92 in the literature), while the specific gravity of quartz is

approximately 2.65. Specific gravity is defined as the ratio of the density of a substance

divided by the density of water. Therefore, the greater relative density of aragonite should

result in an increase in settling velocities and a greater ability of the sediment to withstand

the motion due to currents. (Cunningham, 1966). As proven by Inman and Bagnold

(1963), and followed by Dean's (1973) sediment transport models which show that the

longshore sediment transport rate is inversely proportional to the specific gravity of the

material which, ultimately, should increase the life of the nourishment project due to a

reduction in end losses (Dean, 1999).

Natural Adhesion

Aragonite has been observed to possess a natural adhesive quality. The compaction

of the sediment is greater than that of sand; however, it remains soft enough to permit

digging by hand (Slatton, 1986). No evidence of concretion has been observed in the

stockpiles at Ocean Cay, and it seems rather unlikely that aragonite would form beach rock

(Beachler, 1995; USACE, 1985). Although the genesis of this adhesive quality is

uncertain, it is assumed that this unique characteristic should provide a greater resistance

to erosion while permitting sea water to infiltrate the foreshore of the swash zone

(Cunningham, 1966). This hypothesis has yet to be explored, prompting further

exploration in the laboratory. In addition, environmental issues regarding the ability of sea

turtles to nest in adhesive aragonite sand is of prime concern and will be discussed later in

this chapter.










Gradation

Aragonite sand, as stated earlier, is moderately sorted, which means that the

sediment exhibits a moderate spread in its grain size distribution curve. It is extremely high

in quality and contains small quantities of pebbles, silts, and/or clays (Cunningham, 1966).

In addition, the Marcona operation at Ocean Cay includes a screening and washing

procedure to remove any foreign objects or rocks which may have been dislodged by the

dredge, and also eliminates most silt size grains (Slatton, 1986). This is a desirable

property in any beach restoration project. First, the community receives a uniform, safe,

rock free beach. Secondly, the removal of silts and clays is expected to reduce turbidity

related impacts near offshore reefs and in the surf zone (Beachler, 1995). The placement

of the sand would produce turbidity; however, the amount and duration would be

significantly less than dredging from an offshore borrow site (CPE, 1985). This can be

attributed to aragonite's low concentration of silts, on the order of 0.5 to 2%, when

compared to that of quartz sand in the vicinity of Broward County, which generally

contains from 3% to 10% silts in certain places (CPE, 1985). Moreover, eliminating the

need to dredge from an offshore site, drastically reduces the potential to harm offshore reef

communities (Beachler, 1995). Finally, the moderately sorted grain size distribution allows

the engineer to predict, with some certainty, how the design will perform over time since

in traditional nourishments fine grains of sand could be carried offshore, resulting in

unforeseen losses.

Color

Aragonite sand is bright white in color and is the main reason the Bahamas are

known for their "beautiful white sand beaches". Aesthetically, nourishing with aragonite









41

would result in an attractive beach and could help bolster tourism for that municipality.

However, the white sand reflects solar radiation more than quartz resulting in cooler

temperatures (Cunningham 1966). There has been some concern as to whether this could

adversely affect the ability of loggerhead sea turtles to reproduce, which will be addressed

in Section 4 of this chapter.


3.3.2 Suitability Studies Based on Previous Field and Laboratory Experiments

A number of laboratory and field studies conducted to test the suitability of

aragonite as a beach nourishment material date back to the mid 1960's. The purpose of this

section is to review these studies and their findings in detail to assess both the

effectiveness of the aragonite sand and to determine appropriate areas for future research.

Pepper Park Beach Field Study

In 1965-66 the first small scale prototype study designed to test the effectiveness

of oolitic aragonite as a beach nourishment material was conducted in Pepper Park Beach

in St. Lucie County, Florida by the Union Carbide Corporation (Monroe, 1969). Pepper

Park Beach is located approximately two miles north of the Fort Pierce Inlet. This

particular test site was chosen because of the favorable prevailing stability in the foreshore

slope and the compatibility of the grain size distribution, at mid-tide level, with that of

aragonite (Cunningham, 1966). The basis for this experiment assumed that over the span

of a few years beaches tend to exhibit either accretional or erosional trends; however,

shorter time cycles exist which induce both deposition and erosion allowing for the

assessment of the performance of the test material to these prevailing processes of the

environment (Cunningham, 1966). Pepper Park beach was observed to accrete from








42

September to February, when the dominant net littoral transport is from the south, and

erode slightly over the remainder of the year when the swell direction and associated

transport is from the north (Cunningham, 1966).

The procedure consisted of placing 1,000 tons (approximately 588 cy, using a

conversion factor of 1.7 tons per cy as proposed by CPE, 1997) of aragonite sand, of 0.30

mm mean grain size diameter over a beach length of 200 ft, and an equivalent volume of

native sand from the adjacent backshore at comparable locations on the foreshore of Pepper

Park Beach. The materials to be tested were placed, in equal increments, at the top of the

foreshore, thereby allowing the uprush of successive high tides to naturally disperse the

sediment which provided space to place the next load. The slopes of the test beaches were

not artificially graded, enabling the natural wave activity to shape the respective profiles

of both test beaches. The experiment was designed to commence at the beginning of the

erosional cycle in order to observe and compare the relative erosion rates of both the

aragonite test beach and the native nourishment beach. (Cunningham, 1966).

The monitoring of the experiment consisted of daily inspections of estimated

breaking wave height, period of breaking waves, distance in feet below lowest berm of the

mean high water line, wind velocity and direction, precipitation in the previous 24 hours,

and general appearance of the test beaches (i.e. ridges, troughs, shell deposits, sand mixing,

etc.) (Cunningham, 1966). Profile and sampling surveys were conducted every seven days

and were carried out to the 5 foot depth contour every 14 days (Cunningham, 1966). This

schedule was to continue until adequate information regarding the utility of aragonite as

a beach nourishment material could be satisfactorily ascertained (Cunningham, 1966).








43

Unfortunately, the results of this experiment were inconclusive. Due to an

unusually low tidal cycle over the course of the experiment, the test materials were forced

to be moved 15 feet closer to the ocean than originally planned (Cunningham, 1966).

However, Cunningham did find the aragonite nourishment test site remained slightly more

stable than the native sand site over a six month investigation period. Nonetheless, due to

the small amount of fill material and inadequate controls, the results proved inconclusive

in determining the effectiveness of aragonite as a nourishment material (Olsen and Bodge,

1991).

Oolitic Aragonite and Quartz Sand: Laboratory Comparison Under Wave Action

Prompted by the aforementioned field study, the Coastal Engineering Research

Center (CERC) began investigating the potential of new sources of suitable beach fill

material for use in beach nourishment purposes, specifically for the South Florida coast.

CERC conducted saltwater wave tank tests whereby both a quartz sand beach and an

aragonite beach were tested simultaneously under wave action (Olsen and Bodge, 1991).

This laboratory test setup and procedure described by Monroe (1969), consisted of

a 96 foot long, 18-inch wide flume partitioned in the center by a separating wall in order

to simultaneously test the aragonite and quartz sand beaches under similar wave activity

using artificial sea water. The mean grain size diameter of the aragonite was 0.27 mm and

was comparable to the grain size diameter of the quartz material. The profiles of both

beaches were initially scraped to establish the same initial equilibrium conditions, and were

subjected to differing wave heights ranging from 0.18 to 0.53 feet. The wave periods

varied from 1.19 to 5.06 seconds. After all runs were complete, a final test was conducted








44

simulating beach nourishment. Throughout the test series, profiles were measured

periodically and graphed comparatively.

The analysis of the experimental results consisted of the calculation and graphical

comparison of the cross-shore sediment transport for both materials. The profiles of both

beaches were found to maintain a similar shape and the calculated transport rates based on

profile analysis were comparable. The results of the experiment generally indicate that,

from a hydraulic standpoint, the aragonite material is as good a beach material as quartz

sand, if the wave climate of the beach to be nourished does not require sand sizes outside

of the range of oolitic aragonite available (Monroe, 1969). Thus, beaches with native

quartz grain sizes comparable to aragonite may be considered as potential candidates for

future aragonite nourishment. In addition, Monroe states that future nourishment projects

employing aragonite sediment depend on the ability to place the sediment at a cost

competitive with traditional sand sources. Furthermore, since the materials used had

prototype size characteristics and were tested in a small-scale laboratory setting, no

accurate correlation to a prototype wave climate could be established (Monroe, 1969).

Evaluation of Oolite Araganite for Beach Nourishment in South Florida, USACE 1985

In 1985, the U.S. Army Corps of Engineers conducted laboratory tests to further

explore the suitability of aragonite sand for beach nourishment in South Florida. These

experiments included abrasion evaluation, wet/dry testing in fresh and sea water,

dissolution testing to simulate acid rain conditions, detailed microscopic constituent

determination, x-ray diffraction analysis, bulk specific gravity, and absorption (Olsen and

Bodge, 1991).








45

The abrasion tests were performed in a split wave tank. After representing

approximately two years in nature, the Corps found some breakdown of shell fragments and

cemented oolitic aragonite. However, the amount of material that was abraded was

relatively small, and no difference was observed between the aragonite-only side of the

flume and the aragonite-quartz (equal volume) side (Beachler, 1995).

The possibility that aragonite could dissolve when subjected to the conditions

found on Florida's beaches was also of concern. There have been speculations that acid

rain and/or freshwater discharges from adjacent inlets could result in an increase in acidic

conditions that could act to chemically dissolve and remove the calcium from the calcite

particles, which make up aragonite (CPE, 1985; USACE, 1985; Beachler 1995). This

prompted the USACE (1985) to perform wet/dry testing of aragonite in fresh and sea water,

and solution testing of aragonite for acidic rain conditions with a ph of 4.6. The results of

this experiment demonstrated that no apparent dissolution of the aragonite occurred for any

of the prescribed conditions (Beachler, 1995).

The USACE concluded from these experiments that aragonite "appears to be

suitable for beach renourishment material" (Olsen and Bodge, 1991). Moreover, these tests

showed that aragonite's physical characteristics are superior to those of quartz sand which

should correlate to an increase in nourishment performance and resulting longevity (Olsen

and Bodge, 1991).

Abrasion Testing

The Mohs hardness of aragonite sand ranges from (3.5 to 4.0) while the hardness

of quartz sand is classified as 7.0 (Beachler, 1995). This difference between the two

materials has led to some concern regarding the relative durability and resistance of the








46

aragonite to abrasion when in contact with the harder more angular shaped quartz sand.

Dean (1989), following the Corps study in 1985, found that aragonite in a quartz/aragonite

sand mixture, subjected to artificial tumbling in a salt water solution, abraded more rapidly

than just a pure aragonite sample. However, the aragonite demonstrated an ability to

"season" rapidly, such that most of the abrasion occurred during the initial tumbling of the

sample, with subsequent minimal abrasion occurring thereafter. One plausible conclusion

to this experiment is that the abrasion of the aragonite may be minimized by nourishing

beaches made up of less native quartz sediment, or in areas of high native calcium

carbonate concentrations (Olsen and Bodge, 1991). In addition, if this abrasion factor can

be quantified, in the future an allowance could be provided in the design of any

nourishment project from inception, to account for this loss of sediment.


3.3.3 Fisher Island Project

Background

In December of 1990, construction began on the first full-scale beach restoration

project to utilize imported Bahamian aragonite sand in the United States. Fisher Island,

located in Dade County and situated south of Miami Beach, was the location of the

nourishment project. Fisher Island was created in 1904 when the southern tip of what is

now known as Miami Beach was breached to provide a navigation channel, known as

Government Cut (Olsen and Bodge, 1991). After the channel was created, jetties were

placed on the south end of Miami Beach and on the north end of Fisher Island, isolating the

island from the predominantly southerly littoral drift, resulting in a net loss of sediment

supply to the system. Records indicate that since the completion of the navigation project








47

in 1904, the island's Atlantic coastal shoreline has retreated an average of about 4 ft/yr

(Olsen and Bodge, 1991).

Fisher Island, today, is a well developed, private residential and resort community

consisting primarily of large upscale condominium complexes. Naturally, the community

and owner of the resort facilities recognized the need to nourish the beach to prevent the

on-going erosion and to enhance the area. Olsen Associates, Inc. (1991) investigated

several options that would best suit all involved. Due to the scarcity of offshore borrow

areas, the environmental concerns regarding utilizing upland sources, the owner's

enthusiasm to create a tropical beachfront atmosphere, and the minimal volume

requirements needed to support the project (when compared to typical beach nourishment

projects) made the use of imported Bahamian aragonite sand an excellent candidate (Olsen

and Bodge, 1991).

Detailed Site Characteristics

As a result of the isolation of Fisher Island from the net littoral drift, created by the

Government Cut jetties, the island's southern border eroded 600 to 850 feet before it was

stabilized by a revetment and terminal jetty in the early 1980's (Olsen and Bodge, 1991).

In contrast to most of Fisher Island's shoreline, the northern 250 feet of shoreline has

remarkably remained stable over the past 90 years and has produced a small downdrift

fillet. This is due to a shadow effect that is caused by wave sheltering by Government

Cut's south jetty, which is consistent with the predominant northeast wave direction.

Further grid-based wave refraction analysis, conducted by Bodge (1989), suggests that the

shadow effect results in a nodal point, approximately 500 to 1500 feet south of the southern

jetty. This results in a small net northerly littoral drift to the north of the nodal point, and








48

a rapid increase in the southerly drift to the south of the nodal point. This rapid increase

in southerly drift has been estimated to be on the order of 120,000 cy/yr at the south end

of Fisher Island. The pre-project dry beach width ranged from 20 to 46 feet along the

southern 250 feet of shoreline, and less than 10 feet along the south-central 850 feet of

shoreline (Olsen and Bodge, 1991). Although the southern terminal groin is successful in

retaining some of the net southerly littoral drift, sand does bypass into Norris Cut, to the

south, where it is eventually lost to ebb and flood tidal currents. The shadow effect causes

sand to be transported northward where it becomes impounded at the base of the southern

Government Cut jetty and eventually recirculates around clockwise where it returns to the

shoreline approximately 1500 feet downdrift. These littoral drift scenarios result in Fisher

Island representing its own littoral cell (Olsen and Bodge, 1991). Olsen Associates,

Inc.(1992) found seagrass beds about 130 feet seaward of the mean high water line in the

southern half of the island, and in scattered clusters 50 to 90 feet seaward from MHWL on

the northern half. They determined that for environmental safety, precautions were

required in order to prevent encroachment of the nourishment material on the seabeds.

Project Design

The project was designed to nourish the Fisher Island shoreline with Bahamian

aragonite sand, while both protecting the natural seagrass beds and the integrity of the

nourishment itself. Olsen and Associates (1991) solved this problem through the use of

"tuned" structures. Tuned structures, basically, refer to structures designed to force the

beach planform to equilibrate to a shape that it would not have otherwise. The "tuned"

structures consisted of 6 T-head groins spanning the length of the project, approximately

620 m, to create classical pocket beaches bounded by artificial headlands. The structures








49

shape and size were mainly determined by the location of the seabeds, and the orientation

was "tuned" to the incident wave direction to increase fill stability (Olsen and Bodge,

1991). The expected benefits of this design were threefold. First and foremost, the

artificial headlands would prevent the encroachment of the aragonite on the seagrass beds;

secondly, they would act to stabilize the actual nourishment itself; and finally, from an

aesthetics point of view, the beaches would resemble the stabilized beaches of the

Mediterranean, which worked nicely with the upland structures architecture (Olsen

Associates, Inc., 1992).

Project Construction

Construction began in December 1990 and was completed by March 1991. Once

the rock structures were in place, the beach fill placement phase of the project commenced.

The aragonite was barged approximately 60 miles (one-way) to the site in 2000 short ton

loads (1178 cy) from Marcona Ocean Industries base of operations in Ocean Cay, Bahamas

(Olsen Associates, Inc., 1992). The aragonite was offloaded by a conveyer and directly

transferred into dump trucks at a berthing location on the north side of the island where it

was then transported to the project area and subsequently placed (Olsen Associates, Inc.,

1992).

Specifics regarding the placed aragonite and its characteristics according to Olsen

Associates Inc. (1992) include:

S Compaction- The computed post-construction in place volume of aragonite at the

site was 25,000 cy, 42,950 short tons were imported, including a 6% moisture

content, which Marcona assumes to correspond to 0.74 cy/ton in a natural, non-

compacted state. From this estimation, approximately 31,800 cy are estimated to










have been placed on Fisher Island, which correlates to a compaction of 21.4%.

* Turbidity- The greatest turbidity occurred during the construction of the T-head

groins; however, turbidity 150 m offshore never exceeded the critical value of 29

NTU. Relatively small levels of turbidity from the placed aragonite resulted in

nearshore white cloudiness of the water, but disappeared completely within hours

after the cell was filled.

* Grain Size- The median grain size of the placed aragonite was 0.27 mm with 3%

finer than 0.107 mm and less than .5% finer than 0.074 mm (i.e. minimal amounts

of silts and clays). This sediment is slightly coarser than the native median grain

sizes ranging from 0.21 to 0.24 mm.

* Beach Slope- Olsen Associates assumed that the aragonite would perform 1.36

times its mean diameter which converted to a 0.37 mm quartz equivalent. Utilizing

equilibrium beach face relationships (Bascom, 1951), this value yields beach slopes

ranging from 1:7.4 to 1:10 for low to moderate wave energies. Field studies

conducted at the site measured an average post-project beach slope of 1:9.0 on the

foreshore. This measurement did not include the beach profiles directly adjacent

to the structures which would have yielded non-representative results.

Project Performance

Monitoring of the project included both physical engineering performance statistics

as well as the impact of the project on the environment. To date, performance results for

both categories appear to be extremely positive.

In October 1991, approximately 9 months after construction was complete,

observations conducted by Olsen Associates, Inc. indicated there was no net shoreline








51

retreat anywhere within the project area. This is extremely positive because typically, due

to profile equilibration, one would expect beach recession. The data for the first six months

of the project indicate some apparent losses at the southern end; however these losses were

comparable to gains found on the northern end. This net northward shift of the planform

is indicative of a net northerly littoral drift, which, as of yet, remains unexplained. Overall,

the project performed as anticipated, and the results of the 3 year monitoring study found

that there was no apparent loss of net volume. This was determined to be due, in large part,

to the stabilizing structures constructed at the site (Olsen Associates, Inc., personal

communication).

Environmental impact studies, conducted post-construction, were performed to

determine the effects of the use of aragonite on sea turtle nesting (specifically loggerhead

sea turtles native to the region) and the potential implications of the project on the benthic

and infaunal communities. Results of a joint three year study, conducted by Wetlands and

Ecological Services and the Department of Biological Sciences at Florida Atlantic

University, indicate that aragonite sand temperatures were approximately 20 C cooler than

traditional native Florida quartz sands, which extended incubation times by 5 or 6 days and

may have altered the natural sex ratios of the sea turtles. Sex determination of sea turtles

is known to be temperature dependent. Average temperatures in the observed hatcheries,

on Fisher Island, ranged from 27-310C and could result in a preponderance of male

loggerhead hatchlings. However, the study also found that gas exchange, oxygen and

carbon dioxide levels, water potentials, and grain size distribution were similar between the

aragonite and the quartz hatcheries. Although, the beach eventually became more

compacted, sea turtles continued to nest on the beach and no significant differences were








52

found in hatchling mass and carapace size between nesting sands despite the difference in

incubation periods. In addition, no significant differences were found in hatchling success,

mortality, or emergence success between the two hatcheries. Therefore, the study

concluded that aragonite sand beach nourishment had no significant impact on sea turtle

nesting; however, additional studies on the impact of aragonite on nest temperatures would

be beneficial (Milton, et. al., 1995).

Sediment characteristics which affect benthic and infaunal communities include

grain size distribution, organic content, and silt/clay content. The similarity between

aragonite and quartz sand properties should ensure a suitable substrate for the native

Florida benthic and infaunal environment (Cummings and Fisher, 1995). Moreover,

studies at Fisher Island indicate that similar species compositions exist between both the

aragonite beach and adjacent quartz sand beaches (Cummings and Fisher, 1995; CSA, 1992

and 1993).

3.4 Environmental Issues



The possible environmental effects of utilizing Bahamian aragonite sand for beach

restoration in South Florida are substantial. Specific areas of concern include the

ramifications on sea turtles native to the Florida Coast, infaunal communities, and the

potential implications to the Bahamian environment.


3.4.1 Impacts to Sea Turtles

There are five different species of sea turtles that nest on southeast Florida beaches;

however, for the purposes of this report, the emphasis will be on loggerhead turtles since








53

they represent 95-97% of all nests on Florida's beaches annually (Flynn, 1992; CPE, 1994).

The main emphasis will be on the effects of sediment characteristics on sea turtle

populations, and the effects of aragonite on nesting and hatching success rates.



Effects of Sediment Characteristics on Sea Turtle Populations

A viable sea turtle population is dependent upon the ability of the sediment to foster

a "good nesting beach." A "good" nesting beach allows for adequate gas exchange, has a

proper moisture content, and suitable grain size to permit successful chamber construction

(Cummings and Fisher, 1995; Mortimer, 1982). In addition, other positive characteristics

include a low silt/clay content, low salinity, low levels of organic carbon, high sphericity

of the sand grains, and proper compaction properties to permit successful nest building

(Cummings and Fisher, 1995).

Proper gas exchange is required for the development of sea turtle embryos. The

developing embryos depend on gas diffusion to obtain oxygen and lose carbon dioxide.

The amount of gas diffusion in the sediment depends on several factors. These include the

amount and size of spaces between adjacent sand grains, temperature, and moisture content

(Cummings and Fisher, 1995). Compacted sands have a higher moisture content which

results in lower gas diffusion rates, and increased temperatures result in higher gas

diffusion rates (Lutz et al., 1991). The optimum moisture content to induce successful

hatching and embryonic growth is 25% (McGehee, 1990). Sufficient moisture content is

necessary because if the sediment is too dry the eggs will be dehydrated, while increased

moisture is detrimental, as well (Kraemer and Bell, 1980).








54

Studies have shown that incubation temperatures affect the hatching success, the

rate of embryonic development, and the sex of the hatchlings (Cummings and Fisher,

1995). During early stages of embryonic development the incubation temperature is related

to the net radiation at the surface of the beach, and the heat capacity and conductance of the

sand (Packard and Packard, 1988). The ability to absorb and radiate heat is influenced by

the sediment's color, texture, composition, water content, and the relative depth of the nest

(Cummings and Fisher, 1995). The optimal temperatures for producing healthy loggerhead

turtles ranges from 26-32C with mortality rates increasing drastically for values outside

this range (Cummings and Fisher, 1995). Incubation temperatures also affect the

development rate of the embryos. Lower temperatures tend to slow down development

resulting in longer incubation periods, while higher temperatures act to accelerate

embryonic development, hence shortening incubation periods (Cummings and Fisher,

1995). Incubation temperatures are also widely believed to determine the sex of sea turtles

(Lillycrop and Howell, 1996). Higher temperatures tend to produce more females, while

lower temperatures tend to primarily produce males (Mrosovsky, 1988). Due to this

apparent phenomena, a pivotal temperature has been established at 29-300C, at which a 1:1

male/female sex ratio is established (Lillycrop and Howell, 1996). It is important to

mention that the study of temperature dependent sex ratio hatchlings in loggerhead sea

turtles is still in the developmental stages and a definitive range has yet to be reached.

Some studies have found that the sex determination is related to the time of year of

incubation- whether the eggs were laid early or late in the season. In addition, there seems

to be some uncertainty whether the male/female ratios are a function of environmental or

genetic predisposition.










Effects of Aragonite on Nesting and Hatching Success Rates

All studies indicate that aragonite appears to be a suitable material for successful

sea turtle nesting and incubation. The median grain size, moderate sorting, and the low

silt/clay content of aragonite all fall well within the limits of optimal nesting and hatching

success rates (Olsen and Bodge, 1991). Aragonite appears to have no effect on embryonic

development or hatching success when compared to native Florida sands. In addition, the

similarity in the grain size distributions between aragonite and quartz sands yields

negligible differences in gas diffusion and moisture content (Miller-Way et al., 1987).

Moreover, aragonite does not adversely affect the hatchling's ability to successfully

emerge from the nest, or subsequently hinder the crawl back to the sea (Cummings and

Fisher, 1995). However, aragonite has been proven to affect the temperatures and resultant

durations of the sea turtle incubation periods. This could potentially alter the sex ratios of

the loggerhead sea turtle population native to South Florida (Cummings and Fisher, 1995).

To date, definitive results from studies which compare the sex ratios of the hatchlings

incubated on an aragonite beach with those incubated on a comparable native Florida beach

have not been attained.


3.4.2 Impacts to Infauna Communities

Sediment characteristics which affect infaunal communities include grain size

distribution, organic content, and silt/clay content (Cummings and Fisher, 1995). All

studies show that the aragonite characteristics are comparable to those of native Florida

beaches, suggesting that aragonite will be a suitable material for the native Florida infauna.

In addition, studies revealed that many of the species of infauna found in the Bahamas are








56

native to Florida, as well (CSA, 1992 and 1993). The potential for the introduction of

foreign born exotics entering through the use of aragonite is expected to be minimal. This

may be due to the fact that the Gulf Stream reaches both areas, carrying similar larvae along

it's path, oolitic aragonite already exists in South Florida in minimal quantities, and the

climatic, geologic, and geographic conditions are practically the same for both areas

(USACE, 1987).


3.4.3 Implications to the Bahamian Environment

Several precautions have already been taken by Marcona Ocean Industries in order

to protect the Bahamian environment. Prior to mining, a buffer zone was created to

conserve offshore natural resources, and a large settling basin was constructed to limit the

amounts of suspended material from the stockpiling operations at Ocean Cay. Moreover,

frequent biological surveys are conducted in the area to assess and monitor the impacts of

the mining facility on the environment. Based on these studies it appears that the mining

operations at Ocean Cay have minimal effects on the Bahamian fauna. Studies of the

surrounding seagrass beds, coral reefs, anemones, and filter feeding bivalves adjacent to

the dredging operations yielded no visible signs of siltation, burial, or sediment related

decline (Cummings and Fisher, 1995). Observations of excavated sites revealed the

presence of seagrass and algae which was not present prior to excavation (Rehrer, 1977).

In addition, the mining operations do not appear to impact the sea turtle or shore bird

nesting sites on adjacent islands (Rehrer, 1977). Due to the relatively strong tidal currents

surrounding the aragonite deposits, elevated turbidities and siltations associated with the








57

dredging operations were confined to within a half mile west of Ocean Cay (Rehrer, 1977;

Cummings and Fisher, 1995).


3.5 Political Issues



The potential use of aragonite as a beach nourishment material for South Florida

is dependent upon the successful resolution of various political concerns involving both the

Local, State, and Federal U.S. Governments and the Bahamian Government. This section

will introduce these political issues in an attempt to stimulate thought as to plausible

solutions.



3.5.1 U.S. Protectionist Legislation

The delivery and utilization of imported aragonite sand for purposes of beach

nourishment is subject to U.S. laws regarding international shipping and trade. These laws,

which include the Buy American Act (41 U.S.C. Section 10b), the Jones Act (46 U.S.C.

Section 292), and the Shipping Act (46 U.S.C. Section 883), are designed to protect U.S.

industries from unfair competition from foreign businesses; however, in actuality, there are

provisions in these laws which could pose a serious threat to the use of aragonite in South

Florida (Higgins, 1995).

The Buy American Act was amended in the Water Resources Development Act of

1986 to allow the acquisition of foreign beach fill only if domestic sources are unavailable

for environmental or economic reasons (Higgins, 1995). This means that aragonite could

technically be used in nourishment projects if all other offshore deposits are exhausted, or








58

pose adverse environmental impacts which make the aragonite a more economic solution.

Environmental pressure, of late, to provide increased buffer zones to limit the dredge's

operational capacity around reefs, and growing dissatisfaction with marginal beach

nourishment performance of projects which used small grain sizes, has acted to increase

dredge travel distances, thus increasing the costs. When the economics favor importing

Bahamian aragonite compared to U.S. owned dredging operations, the Buy American Act

will allow the importation of aragonite. Therefore, economics appears to be the key to

permitting aragonite's use.

Both the Jones and Shipping Acts prohibit foreign owned vessels from engaging

in U.S. coastwise commerce, which may be interpreted as not allowing a foreign owned

dredge to transport materials to the U.S. for beach nourishment (Higgins, 1995). The

implications of this are extremely important in determining the economics of aragonite

beach restoration projects. The allowance of foreign owned dredges to fairly compete for

the acquisition and transportation of Bahamian aragonite to South Florida beaches could

drastically reduce project costs (Higgins, 1995). If competition is not allowed then

aragonite, most likely, will not be considered an economic alternative until all offshore

borrow areas have been either completely exhausted or until the regulatory agencies pass

bills prohibiting dredging around reefs.

In addition, environmental concerns regarding the use of aragonite have forced

regulatory agencies to take a stance against the use and implementation of aragonite until

more study results are available. These environmental issues which were discussed earlier

include sea turtle nesting and hatching and potential infauna impacts. As preliminary

environmental studies begin to cast the impacts of aragonite's use in a beneficial light, it








59

is assumed that these regulatory agencies will take a less restrictive stance with respect to

aragonite (Higgins, 1995).


3.5.2 State and Local Political Concerns

Florida has one of the most proactive, comprehensive beach management programs

in the nation (Higgins, 1995). The Florida Department of Environmental Protection, which

is authorized to request state and federal appropriations for beach and inlet projects, is

responsible for maintaining stable beaches. For this reason it is believed that political

concerns, on state and local levels, mainly address economic and environmental

considerations. If the use of aragonite becomes economically feasible and environmentally

sound, then the State would welcome the use of aragonite for beach nourishment (Higgins,

1995). In addition, pressure at the local level to seriously consider aragonite for beach

nourishment is mounting due to jurisdictional disputes regarding the lack of suitable and

economic offshore resources (Higgins, 1995).


3.5.3 Bahamian Political Issues

The mining and exportation of aragonite sand is controlled by the Bahamian

Government. The sale of the aragonite must not only serve the best interests of the U.S.

and Florida, but the Bahamas as well. Higgins (1995) outlines several issues, with respect

to the Bahamian Government, that must be met before the Bahamas regards the sale of

aragonite as in their best interests. First, the dredging operations must not adversely affect

their environment. Secondly, the importation of Bahamian aragonite by the U.S. must

result in significant monetary benefit to the Bahamas. Finally, and possibly most








60

important, the export of aragonite to benefit Florida beaches and tourism must not come

at the expense of Bahamian tourism.

Environmental concerns are important for both the U.S. and the Bahamas, but the

Bahamian Government will undoubtedly demand that assurances be granted that the mining

of aragonite sand will not be harmful to commercially important species of fish and lobster

as well as seagrass beds, coral reefs, and infaunal communities.

Concessions for the sale of aragonite are expected to provide a substantial

economic benefit to the Bahamian Government. The Bahamians will probably charge a

severance tax on the aragonite by the cubic yard (Higgins, 1995). This issue could affect

the economic viability of aragonite's use for beach nourishment.

Tourism is the main source of income for the Bahamas. If the Bahamians consider

that selling aragonite to preserve and enhance Florida beaches will result in decreased

tourism to the Bahamas, it is unlikely that they would agree to selling. The U.S. and

Florida should assure the Bahamian Government that the resulting "white sand beaches"

on the Florida shores will act as an advertisement for Bahamian beaches, that could actually

serve to bolster tourism both in Florida and the Bahamas.

The aragonite deposits located on the Great Bahama Banks are owned by the

Bahamian Government. The use of aragonite as beach fill for Florida shores is contingent

upon the consent of the Bahamians. Higgins (1995) stresses the importance of high-level

discussions with Bahamian Government officials to address and ease their concerns, and

to initiate pertinent studies to quantify these issues.










3.6 Summary and Conclusion



Bahamian oolitic aragonite appears to be a suitable material for beach nourishment

in South Florida. However, its utilization is dependent upon several issues which must be

resolved before any major projects can be constructed. The issues regarding the application

of aragonite include the engineering capabilities, environmental impacts, and political

concerns associated with the use of the sediment.

From an engineering standpoint, studies have indicated that beach nourishment

experiments employing aragonite sand have typically performed as well as or better than

native quartz sands. Cunningham (1966) and Monroe (1969) found that aragonite and

quartz sand beaches subjected to wave activity performed similarly. In addition, Olsen and

Bodge (1991) found that aragonite performs as quartz sand with an equivalent grain size

that is 1.36 times coarser. This is significant since coarser sediments tend to withstand

destructive forces to a greater extent than finer ones allowing for the maintenance of steeper

beach slopes. In addition, coarse sediments can resist sediment motion resulting in

decreased sediment transport rates. Although some laboratory studies have been conducted

to test the efficacy of aragonite as a beach nourishment material, studies to quantify the

relative transport rates of aragonite sand have been limited. Ideally, information regarding

the comparison of sediment transport rates of aragonite and quartz sand beaches could

prove extremely beneficial in predicting the potential benefits of aragonite beach restoration

projects.

Based on available environmental data, aragonite appears to be a suitable material

for the nourishment of South Florida beaches. Aragonite has been proven to not adversely








62

affect sea turtle nesting sites, hatching success, or emergence success. Studies have also

shown that aragonite is a suitable sediment for Florida native infauna, and the introduction

of foreign species to the Floridian ecosystem is expected to be minimal. In addition, the

mining operations at Ocean Cay have resulted in negligible turbidity effects, and in some

areas, have increased and induced seagrass growth where there was none prior to

excavation. Moreover, turbidity levels associated with placed aragonite pose a significantly

less threat to offshore coral reefs and seagrass communities. Although aragonite was

shown to decrease incubation temperatures resulting in increased incubation periods, it is

not known to what extent this affected the sea turtle populations or gender ratios. By all

accounts, biologists concede this is an area of study that warrants further investigation;

however, the overall impact to sea turtles appears to be minimal.

Political concerns related to the importation of aragonite for beach nourishment

purposes need to be addressed. Assurances need to be provided to the Bahamian

Government that the mining and utilization of aragonite for Floridian beach restoration

projects will not negatively impact the Bahamian environment nor Bahamian tourism.

Secondly, the U.S. needs to relax restrictions regarding foreign competition in dredging and

transportation operations in order to reduce the current economic burden of replenishing

beaches with aragonite. Finally, as jurisdictional disputes over diminishing offshore

borrow areas become more significant, it is believed that local pressures will influence the

State and Federal Governments to relax these restrictions, thereby allowing imported

Bahamian aragonite for nourishment of Florida's shores at a reasonable cost.















CHAPTER 4
LABORATORY EXPERIMENTS



4.1 Introduction



The results of the literature survey have prompted a laboratory study to compare the

relative beach nourishment properties and longshore sediment transport characteristics of

sediment native to Florida beaches with those of aragonite. All experimental studies

utilized a typical quartz sand of uniform grain size to provide a basis for transport and

compatible sediment along South Florida beaches. The first experiment conducted was a

beach nourishment performance test where quartz fill sediment compatible to the native

was compared to a similar grain size aragonite fill on an adjacent beach under wave

activity. Both nourishment sections were tested for their longevity and plan area remaining

at various time intervals throughout the life of the project. In addition, the DNRBS

numerical model was employed to try and predict the eventual equilibrium planform of the

nourishment region. This experiment allowed for detailed conclusions to be drawn

regarding the effectiveness and suitability of nourishing native Floridian beaches with

aragonite sediment. The second experiment conducted was designed to obtain a better

understanding of the transport characteristics of aragonite sand and how those qualitative

and quantitative values compare with those for quartz sand under similar wave action. The








64

conclusions drawn from this experiment should aid in determining the basic effective

spreading losses of any nourishment project employing aragonite sand, and should yield

some information as to how the equilibrated aragonite beach and associated profile will

continue to perform over time. All tests were conducted in the three dimensional wave

basin in the Coastal and Oceanographic Engineering Laboratory at the University of

Florida.


4.2 Experimental Equipment



4.2.1 Wave Basin

The wave basin dimensions are: 17.5 m wide, 15 m long, and 26 cm deep. The

basin is equipped with a snake-like wavemaker consisting of 88 paddles and is capable of

producing oblique monochromatic wave trains. To minimize lateral wave diffraction, two

artificial wave guides consisting of concrete blocks were placed on either side of the wave

paddles and extended landward. The guides perform as artificial wave rays, and the guide

on the west (updrift) side of the beach was sealed to ensure no loss of sediment to the

littoral cell and thus performed as a perfect littoral barrier. In addition, a sealed concrete

groin was placed in the center of the beach extending from the beach seaward to a depth

of -26 cm to act as a partition between adjacent beaches for all experiments. The angle of

the groin was such that it was facing directly into the incoming waves to minimize the

interaction of the waves with the structure. A schematic layout of the wave basin is

presented in Figure 4.1. Initially, shoreward of the wave maker, a sandy beach is located

consisting of uniform quartz sediment of 0.25 mm median grain size diameter. See Figure









65

4.2 for the quartz grain size distribution which will be used throughout the duration of all

experiments. A constant water level of 26 cm was maintained within 0.3 cm by a float

triggered pump during all testing.








SNAKE WAVE MAKER

\WAVE RAY
\ WAVE GUIDE
-- -- -----3-^-- -' -
I
I *



SI WAVE GUIDE


s- I I
LITTORAL BARRIER U




SInitial Quartz Sand
I '
*

4II Initial Quart Sand


west-side east-side
LITTORAL CELL LITTORAL CELL
Figure 4.1 Schematic Layout of the Wave Basin and the Initial Test Conditions at
the University of Florida Coastal and Oceanographic Engineering Laboratory










66



100
I I -- breaker line
I iII I I waterline/berm zone
o - - - - - - - -- ,

80-- --- -- - ---- --




c redi n di meter = 0 25 nim
1 110----1 1 -- ---


0
















Figure 4.2 Particle Grain Size Distribution for Quartz Sediment Used Throughout the
40 -- - - - - ... - - - - -- -_ _ -l


















wave heights. The gage was calibrated by measuring the gage output at two known still


















water levels. The wave measurements were then taken at an intermediate distance from the
20------------ --------- -- - - ------ ----------












softwaigure 4.2 Partile laborain Size Disttory, which ran for approximately twSedimenty minutes collecting datahe























bcontinuous. Once pacoles te the maximm and minimm voltage es were ironve aint


software in the laboratory, which ran for approximately twenty minutes collecting data


continuously. Once complete, the maximum and minimum voltages were converted into








67

wave heights. The laboratory results document that the waves were a period, T, of 1.13

seconds, deep water wave height, Ho, of 3.35 cm, breaking wave height of 5.5 cm, and a

deep water obliqueness, ao, of 150. These conditions were maintained throughout the

duration of all experiments.


4.2.3 Survey Technique

Upon the conclusion of each incremental time period of wave activity, the water

level is raised from 26 cm to 30 cm, which is the maximum berm elevation, and a dark

string is placed along the waterline over the entire beach width. This line represents the +4

cm contour. The water level is then lowered by 2 cm, representing the +2 cm contour.

Followed by the +1 cm contour and the mean water line elevation contour line. Then these

contours are mirrored below the mean water line resulting in contours of-1 cm, -2 cm, and

-4 cm. This process is then continued as the water is lowered every 2 cm until the water

level reaches a depth of 8 cm. Finally, the last contour line, -26 cm which is the basin

floor, is documented during the analysis of the survey. The result is a field of sand

contours at elevations of+4 cm, +2 cm, +1 cm, 0 cm, -1 cm, -2 cm, -4 cm, -6 cm, -8 cm,

-10 cm, -12 cm, -14 cm, -16 cm, -18 cm and -26 cm. Once the survey is complete, a Kodak

digital camera is used to photograph the contour lines to import into Surfer software where

it is digitized for later analysis.













4.3 Test Preparation and Design


After the establishment of uniform wave conditions, the wave maker was activated


for 8 hours. The resulting beach was surveyed along three profiles and assumed to be in


equilibrium with the aforementioned wave characteristics. Analysis of the survey and the


resulting beach profiles across the width of the beach yielded an average profile. Figure


4.3 represents the equilibrium beach profile of the quartz sediment.











oI II
- Profile
-\ -- Profile 2
2--------- - ---- ---------- - - - - --- - - - - ---- ------ ----0 Profile3


-2--------- --






S-------- --........--- --- ------ ---------..........
S-2---- ------------- --- ----------



ET -8 - - - ^ - \ - - - - -- - - - - -- - - - - -_


-4- -------------- -- ---,------- ------------- ----


S\ -
W
-12 --------


--- - - - ---


S0.5 1 1.5 2 2.5
Cross-Shore Distance, Y[m]


Figure 4.3 Average Equilibrium Beach Profile of the Quartz Sediment










69

The existing beach was then returned to its initial state by standard scraping techniques, and


molded to the equilibrium condition established during the first stage of this procedure.


The process of scraping clean the bed forms followed by molding the beach to the


aforementioned equilibrium beach profile was performed at the end of each experiment,


namely the beach nourishment experiment and the sediment transport experiment, thereby


providing the initial conditions for the next testing procedure. The molded template was


constructed out of standard half inch plywood and consists of both an upper (onshore) and


lower (offshore) profile section. Each section was manually fitted with a carpenter level


to ensure proper vertical elevations. Figure 4.4 is a diagram of the quartz/aragonite


equilibrium beach profile templates.


5 -
4 Onshore Section Offshore Section






-2 Water Line


N

-0 6


9 Breaker Line
-10 -
-11
-12
-13
-14 --distance from control line
-15
-16 L L I I L I
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3
Cross-Shore Distance, y[m]


Figure 4.4 Schematic of the Quartz/Aragonite Equilibrium Beach Profile Templates










4.4 Experimental Procedures


4.4.1 Beach Nourishment Performance Experiment

The beach nourishment performance test has been designed to develop a better

understanding of the relative longevity of nourishment projects employing aragonite vs.

quartz sediments. Utilizing the wave basin in a confined laboratory environment, affords

the opportunity to test both a quartz fill section, compatible with the native, alongside an

aragonite fill section of comparable grain size characteristics. The beach was divided by

a complete littoral barrier into two separate sections to prevent any mixing of sediments,

see Figure 4.1. After the beach was scraped and molded with the templates, the wave

maker was activated for 3 hours to allow the initial prenourished beach to be in complete

equilibrium with the incoming wave direction. Contrary to actual field nourishment

designs, the test fill was designed specifically to induce sediment transport. This is

achieved by exaggerating the angle between the tapered ends of the shore parallel fill and

the initial dry beach, while reducing the length of the fill section. The signal that is

produced by instituting this type of design and subjecting it to monochromatic wave

activity should be large enough such that relative correlations may be drawn between the

transportability of nourishment projects implementing quartz fill compatible with the native

with that of aragonite fill. Figure 4.5 is a schematic layout of the beach nourishment

performance experiment and associated fill design.











SNAKE WAVE MAKER
-r --------------- '-= -
I \& WAVE RAY
, WAVE GUIDE
'
*



CD \WAVE GUIDE 1
S s
FL I i
LITTORAL BARRIER S
I S I ------------------------
SQUARTZ SAND FILL
ARAGONITE FILL Q




west-side east-side
LmTTORAL CELL LITTORAL CELL
Figure 4.5 Schematic Layout of the Beach Nourishment Performance Experiment
and the Associated Fill Design






The total project area of the design was 3 m for each fill. The maximum berm elevation

of the nourishment was made to conform with the existing +4 cm berm height. The center

rectangular section was 1.5 m long with two 0.75 m tapers on either side. The berm, and

associated dry beach width of the nourishment, extended seaward to the 6 cm depth

contour, a distance of 0.64 m. From that point the toe of the fill was configured to meet the

bed at a 2:1 horizontal to vertical slope. The total extension seaward of the entire

nourishment, including the toe, was to approximately the -8 cm depth contour line, a

distance of 0.85 m.

The placement of the nourishment was conducted in such a manner as to not

adversely affect the preexisting beach platform. This was performed by inserting 3/4 inch








72

dowels at each intersection point, i.e. all of the comers, through the beach and down to the

floor of the basin. The berm height was then established by using a rotating laser. Once

complete, the dowels were cut at the proper height and fitted with 2x2 inch ribbing which

acted as the basic skeleton of the nourishment. After the form was in place, the fill material

was placed inside the project area with a moisture content of approximately 25 percent.

Compaction was performed by rudimentary techniques and the final form of the

nourishment was smoothed by running a piece of plywood over the ribbing. Finally, the

outer mold was dismantled and fill material was compacted into the holes left by the

dowels.

Based on sieve analysis, it was found that the aragonite sediment obtained from

Marcona Ocean Industries had a mean grain size of 0.30 mm. Before the aragonite could

be placed in the nourishment section, the sediment was manually sieved, removing a

portion of the coarser sediments. The resulting grain size distributions of the aragonite and

the quartz nourishment fill size distribution are presented in Figure 4.6. From Figure 4.6,

it is evident that the mean diameter of the aragonite sands is slightly larger than that of the

quartz. This was intentional to account for the larger percentage of finer material in the

aragonite. Due to the larger portion of fines in the aragonite, it is assumed that the small

increase in the mean diameter will result in these two nourishment materials being

approximately comparable in size characteristics.











73




100
Aragonite
0 '0 -- I -0 Quartz
90 11111 -I I--- j I
0-- -- - - - - - - -.... ....- .
I I i , lI ii Pil I 1 11111




I I I 1 1 1 1 I I I 11 I I I
0 - - - - - - - 1 I I

C..
II I I I I I I I I I 1 1 I I 1




40 -- - - - - - - --- - - -- -- --


( 5 ..0 -.- - - - - - - - - - - - - - -,- - - - - -, ,-
20 I I -

I I I I I Ii 1 111111 I I I i I
I I I I I I I I I I








10- 2 10- 100 10

Grain Size [mm]


Figure 4.6 Sand Size Distribution of Aragonite and Quartz Fill










The testing procedure commenced with a pre-nourishment survey followed by a post


nourishment survey at time, t, equal to 0 minutes. Monochromatic waves, of the


aforementioned characteristics, were then run over time intervals of 5, 9, 20, 40, and 60


minutes with post surveys conducted after each time period. The interpretations of the


results of these surveys will be presented in Section 4.5 of this report and the analysis of


these results will be presented in Chapter 5.











4.4.2 Sediment Transport Experiment

The sediment transport experiment was performed to understand the relative

differences and similarities between the transport properties of quartz and aragonite sands.

Basically, both beaches are prepared to be initially out of equilibrium with the oblique

incoming wave activity. By monitoring the beaches over time, the respective transport

characteristics of each sediment can be determined as the beaches evolve and equilibrate.

Figure 4.7 represents the layout of the wave basin for this experiment. From Figure 4.7,

it is evident that the basic setup was maintained throughout all testing procedures; however,

the quartz sand in the eastern most compartment was completely removed and filled with

aragonite. This formed two distinct beaches, one composed of quartz sediment and the

other of aragonite, separated by the center littoral barrier.







SNAKE WAVE MAKER

\g WAVE RAY
WAVE GUIDE



\WAVE GUIDE \
I


g LITTORABARRIER
Quartz Sand I Aragonite Sand





west-side east-side
LITrORAL CELL LITTORAL CELL
Figure 4.7 Schematic Layout of the Wave Basin for the Sediment Transport Experiment








75

After the aragonite was placed, the basin was filled to allow the aragonite to saturate

and eventually settle. Once the aragonite was compacted to a similar state as the quartz

beach, both beaches were raked to remove any preexisting bed forms and configured with

the profile templates shown in Figure 4.4. Testing commenced with an initial survey

immediately after the beaches were molded at time, t, equal to 0 minutes with subsequent

surveys conducted after 30, 60, 90, 120, 180, and 240 minutes of monochromatic waves.

The interpretations of the results of these surveys will follow in Section 4.5 of this report

and the analysis of these results will be presented in Chapter 5.



4.4.3 Rapid Sand Analyzer Experiment

A Rapid Sand-Analyzer (RSA) was utilized to obtain the settling velocity

characteristics of quartz and aragonite sands of the same diameter. The Rapid Sand

Analyzer, located at the University of Florida's Coastal and Oceanographic Engineering

Laboratory, is a large settling tube which is 254 cm in length and approximately 30 cm in

diameter. The tube was filled with fresh water at 200C. The bottom of the tube is fitted

with a pan which collects the sediment. This pan is supported by three thin wires attached

to an electronic scale which measures the cumulative weight of the material as a function

of time. The sample is placed in a holding compartment at the top portion of the tube

which automatically opens when testing begins. The quartz and aragonite samples were

also sieved through Standard Sieve Numbers 30, 40, 50, 60, 80, 100, 120, 140, and 160.

The proportion of material remaining on each sieve was then separated and saturated for

24 hours to remove any air pockets which would hinder the settling of the samples. Once

complete, each sample was placed into the RSA and the average settling velocity for each








76

size range was calculated. The results and analysis of this experiment will be presented in

Chapter 5 of this report.


4.5 Results



Analysis of the beach nourishment experiment and the sediment transport

experiment will be conducted in a similar manner. Once all testing procedures were

complete, the digitized Surfer plots of each survey were analyzed to calculate the sediment

transport rates and the proportion of nourishment material remaining after each time period

for each respective beach. This was accomplished by calculating the volumetric changes

under the initial survey from each subsequent profile which produced an average estimate

of the transport characteristics over time. If all the sand in the littoral cell was conserved

then all of the positive changes should equal all of the negative changes. Similar methods

are employed to evaluate the relative compatibility of each experiment such that

quantitative comparisons may be drawn for the two sediments. Analysis of these

experiments, presented in Chapter 5, are based on the various survey plots presented in

Appendix A of this thesis.

The rapid sand analyzer test results will be analyzed by plotting the settling

velocities of each sediment of known grain size against one another such that a correlation

between the two can be reached. The values obtained to determine a proper quartz

equivalent grain size for aragonite will be determined and compared to those values found

through theory outlined in Chapter 2. In addition, these values will also be compared to

the quartz equivalent found by Olsen and Bodge (1991) for aragonite sediment.















CHAPTER 5
ANALYSIS AND DISCUSSION OF LABORATORY RESULTS



5.1 Introduction



The objective of this chapter is to present and discuss the results of the laboratory

experiments. The main features of interest are the determination of the relative

effectiveness of aragonite with respect to quartz sands include profile and planform

evolution, volumetric changes, sediment transport rates and characteristics, and the effects

of settling velocity on these parameters. Section 5.2 presents the results of the beach

nourishment experiment. The results from the sediment transport experiment and the

settling velocity experiment follows in Sections 5.3 and 5.4, respectively.


5.2 Beach Nourishment Experiment



The beach nourishment experiment was conducted to determine the potential

effectiveness of nourishing a native quartz beach with compatible aragonite sediment. The

evolution of two similar nourishment sections were compared, each consisting of

compatible quartz and aragonite sands. The project areas were each evaluated by

comparing the shoreline evolution and volumetric density changes within the nourishment

region, associated profile evolution, proportion of fill material remaining over time, and

77










78

DNRBS simulations to quantify the sediment transport coefficient, K, for both the quartz


and aragonite nourished beaches.



5.2.1 Shoreline Evolution and Volumetric Density Changes


Figures 5.1 and 5.2 present the shoreline evolution of the quartz and aragonite


nourishment sections, respectively. These plots were generated by interpolating the


digitized shoreline data collected for each survey conducted throughout the course of the


experiment.








hitia Shcmline
-- PostNouishmert, t=0min
t = 5 minutes
t= 9 minutes
St = 20 minutes
0.8 - - - - - - t=40minutes
t = 60 minutes


06 --- -- --- --- - - -- --- --I - I -


/ I ,
I N
0 - - -- :- - - T - -




0).2 -----------I F-------i--T-i -- -----------------I----------








1 2 3 4 5 6 7 8
Longshore Distance, X[m]


Figure 5.1 Shoreline Evolution of Quartz Nourishment After 0, 5, 9, 20, 40, and 60
Minutes of Wave Activity
Minutes of Wave Activity































02 II I





Longshore Distance, X[m]
0 .4 - - - . . - - - - -.. . .- -,-- -















Figure 5.2 Shoreline Evolution ofAragonite Nourishment After 0, 5, 9, 20, 40, 60
Minutes of Wave Activity





Examination of Figures 5.1 and 5.2, reveals interesting details regarding the beach

nourishment shoreline evolution of aragonite and quartz sands. First, it is interesting to

note that in the evolution of each nourishment, initial perturbations in the design tend to be

maintained throughout the life of the project. Secondly, the resulting dry beach width

initially decreases rather rapidly, but tends to stabilize over time for each nourishment.

Finally, the resulting total change in dry beach width for the quartz and aragonite









80

nourishments is remarkably similar. This is evident in Figure 5.3 which denotes the change

in dry beach width over the 60 minute duration of the experiment for each test section.






-e Aragoite Nourishment
Quartz Nourishmert
0.1 --L Projet-Ae --



SShoreline

-01 ----


-0.2 -sac -. . - Ar.-------------------- -----


F u -0.3 -om parison- of"--- - - W idth - ........... - --
3 -0.4- - - - - - -- - - - - - - - - -- - - --- - - - - -- -- - - --- -








Activity for Quartz and Aragonite Test Nourishments













The average recession for the aragonite and quartz nourishments occurring within

the 1.5 m center rectangular design section was -0.44 m and -0.46 m, respectively. The

associated dry beach recession within the tapered regions of the projects were also
l)"05 -T-- - -. .... . .- "- - - - -^ : - --"-



_0 3 3.5 4 4.5 5 5.5
Longshore Distance Within the Project Area, X[m]

Figure 5.3 Comparison of Change in Dry Beach Width After 60 Minutes of Wave
Activity for Quartz and Aragonite Test Nourishments








The average recession for the aragonite and quartz nourishments occurring within

the 1.5 m center rectangular design section was -0.44 m and -0.46 m, respectively. The

associated dry beach recession within the tapered regions of the projects were also








81

comparable for each sediment, as is evident in the correlation of the curves below 3.5 m

and above 5 m in Figure 5.3.

The changes in volumetric density for the quartz and aragonite nourishments is

presented in Figures 5.4 and 5.5, respectively. These figures were generated by summing

the volumes across each profile line for every survey and referencing them to the initial pre-

nourishment conditions of each beach. There are a total of 182 profile lines across each test

beach with an approximate longshore spacing of 0.05 m between profiles.


Alorshore Distarce, Xfm]


Figure 5.4 Change in Quartz Volumetric Density After 0, 5, 9, 20, 40, and 60 Minutes
of Wave Activity



































0 1 2 3 4 5 6 7 8
Alongshore Distance, X[m]

Figure 5.5 Change in Aragonite Volumetric Density After 0, 5, 9, 20, 40, and 60
Minutes of Wave Activity






An evaluation of Figures 5.4 and 5.5 to determine the total loss of volumetric

density within the rectangular region of the nourishment planforms is presented in Figure

5.6. Calculating the average maximum loss of volumetric density, AV [m3/m], for the

aragonite and quartz nourishments over the 60 minute duration of the experiment yields

values of -0.0342 and -0.0371 m3/m, respectively.



































S 3 3.5 4 4.5 5 5.5
Longshore Distance Wthin Project Area, X[m]

Figure 5.6 Comparison of Loss in Volumetric Density After 60 Minutes of Wave
Activity for Quartz and Aragonite Test Nourishments


Although the shoreline recession shows a higher correlation than the change in

volumetric density between the quartz and aragonite nourishment sections, similar trends

exist, as is evident in Figures 5.1 through 5.6. In both cases each nourishment first

exhibited a rapid recession which eventually stabilized after approximately 40 minutes of

wave activity. The magnitudes of these recessions, occurring after each time interval for

both test beaches, were also comparable. In addition, the fact that initial perturbations in








84

the nourishment design were maintained throughout the testing procedure, for each beach,

was evident in both the change in shoreline position and volumetric density.


5.2.2 Average Profile Evolution

The average profile evolution of both the quartz and aragonite test nourishments

will be presented in this section. The profiles were generated by averaging each profile line

within the rectangular portion of the nourishment section over each time interval. As stated

in Chapter 4, the rectangular portion of the project length was 1.5 m. The spacing between

profile lines was approximately 0.05 m resulting in 31 profile lines across the length of the

rectangular nourishment. Figures 5.7 and 5.8 present the average profile evolution for the

quartz and aragonite test nourishments, respectively.

The evolution of the nourishment profiles, for both test sections, demonstrate the

initial rapid equilibration of the nourished profile, followed by a general stabilization which

occurred after approximately 40 minutes of wave activity. The relative similarity in the

steepness of the foreshore slope is also evident. The equilibrated aragonite and quartz

profiles occurring after 60 minutes of wave activity are presented in Figure 5.9. From

Figure 5.9, it is interesting to note the foreshore slopes, from the berm elevation, B of 4 cm

to the depth of closure, h, of approximately -8 cm, of each profile is practically identical;

however, at a depth, z of-2 cm, the aragonite profile maintains a slightly steeper slope.













































-2- i- -- .


-201 2-------- --- -- ------ ---------- --










-28I i I I I
0 50 100 150 200 250 300 350 400 450
Cross-Shore Distance, Y[cm]


Figure 5.7 Quartz Test Nourishment Average Profile Evolution After 0, 5, 9, 20, 40, and
60 Minutes of Wave Activity














































Cross-Shore Distance, Y[cm]

Figure 5.8 Aragonite Test Nourishment Average Profile Evolution After 0, 5, 9, 20, 40,
and 60 Minutes of Wave Activity
























0 1 -1 ------ -8- -"-- - -
20 -12




-2 ------------------ ----------------




-25
0 50 100 150 200 250 300 350 400 450 500
Cross-Shore Distance, Y[cm]

Figure 5.9 Comparison of Average Equilibrated Beach Profile of Aragonite and Quartz
Test Nourishments After 60 Minutes of Wave Activity







Analysis of the evolution of the quartz and aragonite profiles indicates that the

stabilization times and the steepness of the foreshore slopes between the two sediments is

similar. Furthermore, upon careful review of Figures 5.7 and 5.8, the aragonite profile

appears to be slightly more stable at depths, z ranging from -3.75 cm to -6.0 cm. Further

analysis of the proportion of sand remaining within each project area, which will be

presented in Section 5.2.3, and the determination of the associated sediment transport

coefficient for each nourishment is still necessary in order to ascertain a thorough

hypothesis as to the complete efficacy and suitability of the aragonite nourishment section.




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