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Recommendations for placement of dredged sand on Perdido Key Gulf Islands National Seashore

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Title:
Recommendations for placement of dredged sand on Perdido Key Gulf Islands National Seashore
Series Title:
UFLCOEL
Creator:
Dean, Robert G ( Robert George ), 1930-
University of Florida -- Coastal and Oceanographic Engineering Dept
United States -- National Park Service
Place of Publication:
Gainesville Fla
Publisher:
Coastal and Oceanographic Engineering Dept., University of Florida
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English
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51 leavles : ill. ; 28 cm.

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Subjects / Keywords:
Shore protection -- Florida ( lcsh )
Dredging spoil -- Florida ( lcsh )
Gulf Islands National Seashore (Fla. and Miss.) ( lcsh )
Coastal and Oceanographic Engineering thesis M.S
Coastal and Oceanographic Engineering -- Dissertations, Academic -- UF
Genre:
non-fiction ( marcgt )

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General Note:
"January 12, 1988."
General Note:
Prepared for: National Park Service.
Funding:
This publication is being made available as part of the report series written by the faculty, staff, and students of the Coastal and Oceanographic Program of the Department of Civil and Coastal Engineering.
Statement of Responsibility:
by Robert G. Dean.

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UFL/COEL-88/016

RECOMMENDATIONS FOR PLACEMENT OF DREDGED SAND ON PERDIDO KEY GULF ISLANDS NATIONAL SEASHORE
By
Robert G. Dean

January 12, 1988
Prepared for: National Park Service 75 Spring Street, SW Atlanta, GA 30303




RECOMMENDATIONS FOR
PLACEMENT OF DREDGED SAND ON PERDIDO KEY
GULF ISLANDS NATIONAL SEASHORE
January 12, 1988
Prepared For:
National Park Service 75 Spring Street, SW
Atlanta, GA 30303
Prepared By:
Robert G. Dean
Coastal and Oceanographic Engineering Department
University of Florida
336 Weil Hall
Gainesville, FL 32611




EXECUTIVE SUMMARY
This study has evaluated the volumes of beach quality material available from the dredging planned for the deepening of the Pensacola Bay Entrance Channel. Recommendations have been made for volumes and configurations of placement on portions of the Perdido Key Unit of Gulf Islands National Seashore.
The historical shoreline changes and behavior of the 1985 beach
nourishment have been analyzed to provide an improved basis for developing recommendations for and predictions of the evolution of any future nourishment. The following summarize the results and recommendations.
1. The dominant sand transport direction along Perdido Key is from east to
west and in a natural state; the sand supply to the eastern end of Perdido
Key was from Santa Rosa Island across a relatively shallow outer bar.
2. Dredging of the Pensacola Bay Entrance commenced in the 1880's. This
previous deepening has caused an erosional stress on the eastern end of Perdido Key. Florida Department of Natural Resources data from 1974 to
1984 document erosion rates on the order of 5 ft. per year amounting to at
least 250,000 cubic yards per year. This erosional effect is typical of
shorelines located downdraft of modified entrances.
3. Based on analysis of limited shoreline change data collected by Rutgers
University, it appears that the 1985 nourishment project is performing in an expected manner with erosion of sand in the region placed, and material
transported to and deposited on adjacent beaches.
4. Results from analysis of aerial photographs are consistent with 2 and 3
above.
5. Based on a field trip and analysis of sediment samples, there do not
appear to be any significant adverse effects as a result of the 1985
nourishment project, with the nourished region revegetating naturally.




6. Based on an analysis of Vibrocore data along the entrance channel, the
material quantities and qualities have been determined as presented in
Tables III and IV.
7. It is recommended that consideration be given to placement of
approximately 5,000,000 yd3 of sand distributed over a beach segment length of 4.5 miles. After the beach profile has equilibrated, this should advance the shoreline gulf ward by a maximum of approximately
270 ft. This material is of high to excellent quality.
8. In some areas of the dredging, the distribution of high quality material
was not adequately defined by the cores. In these areas it will be
necessary to monitor carefully the dredging operations. If this level of
field vigilance is not considered practical, it is recommended that the
3
volume placed be reduced to 3,600,000 yd
9. The recommended initial planform of the placed material is presented in
Figure 12 for a volume of 5,000,000 yd The anticipated evolution is
shown in Figure 13.
10. It is recommended that the results of this project be monitored and if the
results document losses in the placed area and transport to the west as
expected, consideration should be given to placing all future maintenance dredging of good quality material on the eastern end of Perdido Key so as to reinstate the sediment transport that existed under natural conditions.
A preliminary monitoring plan is presented as Appendix I.




TABLE OF CONTENTS
EXECUTIVE SUMMARY ................... ...........**.......................... 2
LIST OF FIGURES .......................................................... 6
LIST OF TABLES ............................................................ 7
INTRODUCTION ............................. ..... .......................... 8
OBJECTIVES AND CRITERIA ................................................... 8
Objectives............................................................ 8
Criteria ................................***...... **** ** ** **................** ... 8
CHARACTERISTICS OF CHANNEL DEEPENING PROJECT AND OTHER RELEVANT INFORMATION* ************************...................................... 8
METHODS...........................,....................................... 11
Sand Quality and Quantity.............. .. ..... ....... ........ ....... 13
Amount of Acceptable Material Available............. .............. 15
Station 207+60N to Station 107+90N............................ 15
Station 107+90N to Station 61+50No........................... 15
Core 26........................................ .......... ..... 15
Stations 61+50N through Station 23+60N ............. 00 ............. 19
Stations 23+60N through Station 7+60S..,.... .......... ........ 19
Station 7+60S to 41+50S............................ .... ......... 19
Station 41+50S to Station 92+50S...... ............................... 19
Station 92+50S to Station 112+60S................................ 20
Station 112+60S to Station 196+50S.............................. 20
Summary of Available Material Quality...................... .......... 20
HISTORICAL SHORELINE CHANGES......... ................ .. .................. 21
Florida Department of Natural Resources (1974-1984) ................... 21
Beach Restoration, Summer 1985............. ..... ............ .......... 21
Shoreline Changes................................ ............. ........ 24
Aerial Photography....... ................. ............................ 26
SEDIMENT ANALYSIS......................................................... 30
RECOMMENDED INITIAL PROJECT CHARACTERISTICS AND EVOLUTION OF THE PLANFORM.......................... .. .. .................... ........... 35
Initial Planform**********************************************......... 35 Planform Evolution. ..... .. ...................... ........... ...... 36
Beach Profile. ............................................... ...... .. 36
BIOLOGICAL CONSIDERATIONS.............. .. .............................. .. ... 36
Emerita Talpoida (Mole Crabs)................. ........................ 40
Donax (Coquina Clams).... ........................... .. .............. ..... 41
Ocypode Quadrata (Ghost Crabs).......................... .. ........ 41




Panama City Studies. ...... .. ... ....... .. .. .. .. .. .. ... ... .... 42
Summary Regarding Biological Effects of Beach Nourishment ............ 43
APPENDICES
I Preliminary Monitoring Program to Quantify Physical Effects
of Beach Nourishment on Perdido Key............................... 46
TI Governing Equations for Beach Planform Evolution ................. 50




LIST OF FIGURES

FIGURE
1. Channel Layout Showing Three Dredging Reaches..................... 10
2. Interior and Gulf Channel Cross-sectional Characteristics......... 12
3. Locations of Vibrocores........................................... .... 14
4. Distribution of Required Total Dredging Pensacola Homeport.
Includes Advance and Allowable Overdepth Dredging Quantities...... 16
5. Distribution of Required Total Dredging Pensacola Homeport and
Quality of Material. Includes Advance and Allowable Overdepth
Dredging Quantities ............................................... 17
6. Shoreline Change Rates for Escambia County, January 1974 to
October 1984. Based on Florida DNR Surveys. Note Shoreline
Change Rates Shown Have Been Smoothed by a Five Point Running
Average ........................................................... 22
7. Locations of DNR Monuments and Segment Nourished in 1985.......... 23
8. Example of Evolution of Initially Rectangular Beach Planform
on a Long Uninterrupted Shoreline..............o ...... .......... 25
9. Average Shoreline Changes Over DNR Ranges 61-64 Encompassing
Shoreline Segment of 1985 Nourishment.... ..................... 28
10. Shoreline Position as Determined from Aerial Photography
Analysis.......................................................... 31
11. Shoreline Changes in Vicinity of 1985 Beach Nourishment. Based
on Analysis of Aerial Photographs................................. 32
12. Location and Characteristics of Recommended Beach Nourishment..... 37
13. Calculated Evolution of Recommended Nourishment Planform for
Stable and Eroding Beaches........................................ 38
14. Recommended Characteristics of Nourished Profile. Illustrated
for DNR Monument No. 48... ............................... ..... ... 39
I-I. Recommended 31 Profile Locations and Location of Directional
Wave Gage ......................................................... 48




LIST OF TABLES

TABLE PAGE
I Chronology of Pensacola Bay Entrance Channel Dimensions ............. 11
II History of Maintenance Dredging Pensacola Entrance Channel
1975-1987 .............................. ............ o ............. ...... 13
III Summary of Available Material Quality and Quantity Pensacola Bay
Channel Deepening .... o..... .. .................................. o.... 18
IV Overall Summary of Material Quantities and Qualities ............... 20
V Shoreline Change Data Furnished by Rutgers (Distances in Meters) .... 27
VI Plan Area Changes Associated with 1985 Nourishment.................. 29
VII Characteristics of Aerial Photography Used in this Report........... 29
VIII Summary of Sediment Size and Calcium Carbonate Characteristics ...... 34 IX Characteristics of Sediment Samples Inside and Outside of 1985
Nourishment Limitsao ...... i c........................................ 35
X Initial Planform Characteristics. ...... ........................ o.... 36




RECOMMENDATIONS
FOR PLACEMENT OF DREDGED SAND ON PERDIDO KEY GULF ISLANDS NATIONAL SEASHORE
INTRODUCTION
Perdido Key is one of a series of barrier islands along the
Florida/Alabama coastline. Under natural conditions the sediment supply for these islands was maintained by transport from the east and the sand was moved across channel entrances by waves and currents acting on broad relatively shallow outer bars of sand. As needs for deeper and more stable navigational channels developed, these channels were deepened and in some cases stabilized by jetties which served to train the tidal flows. These modifications interrupted the natural sediment transport pathway noted above with a resulting erosion of the downdraft shorelines. This scenario applies to the eastern end of Perdido Key, where measurements conducted by the Florida Department of Natural Resources over the 1974-1984 period document rather severe erosion extending more than 8 miles from the eastern island end. The forthcoming deepening of the entrance channel to Pensacola Bay to serve as a homeport for the aircraft carrier Kitty Hawk may further alter natural processes but also provides the opportunity to compensate for past losses through placement of fairly large quantities of good quality sand on the eastern end of Perdido Key. This would be a one-time placement through sand available from channel deepening. Additionally, based on experience, it is likely that good quality maintenance material will be available periodically to serve to reinstate the natural sediment supply. It is important to the quality of Perdido Key to identify the appropriate amounts and placement locations of the sand available from the channel deepening and maintenance dredging. The criterion, consistent with National Park Service policy, is to reinstate, in as natural a manner as possible, the longshore sand flow to the island and to regain a reasonable amount of the sand eroded due to past modifications and dredging practices in the entrance channel.




OBJECTIVES AND CRITERIA
Objectives
The objectives of the present study are:
(1) To review the shoreline change history at the eastern end of Perdido Key.
(2) To quantify that portion of shoreline changes associated with past
channel maintenance and sand management practices.
(3) Consistent with National Park Service policy, to develop recommendations
for the amounts and placement locations of sand resulting from: (a) the
channel deepening, and (b) periodic maintenance dredging.
Criteria
The broad criteria employed in approaching the objectives above are:
(1) To utilize an appropriate amount of the forthcoming channel deepening
material to reestablish the island in the condition that would have
prevailed if the long-term dredging had not occurred.
(2) Within existing constraints, to reinstate the natural sand transport
quantities in the vicinity of the eastern end of Perdido Key. This
criterion would apply primarily to the maintenance dredging.
CHARACTERISTICS OF CHANNEL DEEPENING PROJECT AND OTHER RELEVANT INFORMATION
The Pensacola Bay Entrance Channel has been a Federally authorized channel since 1881. Table I presents the dates associated with various authorized and excavated channel depths and widths.
The channel associated with the Kitty Hawk homeporting extends from the
berthing docks inside Pensacola Bay westward then southward around the western end of Santa Rosa Island and finally south-southwest to a natural water depth of 48 ft. As presented in Figure 1, the total channel length is approximately
7.7 miles and extends an approximate distance of 4 miles gulfward of the Perdido Key shoreline. Two channel cross-sections are incorporated into the design. From the berthing area to slightly east of the western tip of Santa




Figure 1.

Channel Layout Showing Three Dredging Reaches




TABLE I
CHRONOLOGY OF PENSACOLA BAY ENTRANCE CHANNEL DIMENSIONS
Channel Dimensions Authorized
Year Depth (ft.) Width (ft.) or Actual
1881 24 80 Authorized
1885 22.5 80 Actual
1890 24 120 Actual
1896 30 300 Authorized
1902 30 500 Authorized
1935 32 500 Authorized
1959 37 800 Actual
Present 44 800 Authorized
Rosa Island, the nominal depth is 42 ft below MLW; for the remainder of the channel length to its Gulf terminus, the nominal depth is 44 ft. The actual dredged depths will include an additional 2 ft for "advance maintenance" and an additional 2 ft for "allowable overdredging". Thus, as presented in Figure 2a and 2b the dredged depths for the two cross-sections will be 46 ft and 48 ft. The total anticipated dredging for the project is in excess of 13.3 million cubic yards. It is anticipated that the deepening project will commence in October 1988 and continue through 1990. A maintenance dredging project of approximately 200,000 yd 3 was conducted in November-December, 1987 with offshore placement. Table IT presents the history of maintenance dredging over the period 1975 to 1987.
METHODS
The overall methods included a site visit, review and analysis of prior studies in the area including data collected by Rutgers, and computations of the behavior and effects of sand placement. The detailed methodology employed and results obtained are presented in the following sections of this report.




Ambient Bottom
(Varies in Elevation)
............................. .........
7LIU 800 ft ~:j
5. 5
- --------------------------- 42 ft Project Depth
--. 44 ft Includes 2 ft Advance Maintenance Dredging :- 46 ft Including 2 ft Allowable Overdredging
a) Interior Channel Characteristics
[10
0
.......,.....:. ...- -' '
0 200
_ fJ /:1" IHorizontal and 800 t1 Vertical Scales
5- 5
---- Project Depth
-46 ft Includes 2 ft Advance Maintenance Dredging ... ... ,.......... .. .............. --48 ft Including 2 ft Allowable Overdredging
b) Gulf Channel Characteristics

Figure 2. Interior and Gulf Channel Cross-sectional Characteristics.




TABLE II
HISTORY OF MAINTENANCE DREDGING
PENSACOLA ENTRANCE CHANNEL
197 5-1987
Year Volume Dredged Type Dredge Disposal Area
(yd3)
1975 1,100,000 Hopper Gulf Disposal
1981 647,000 Hopper Gulf Disposal
1983 114,000 Hopper Gulf Disposal
1984 917,000 Hopper Gulf Disposal
1985 2,433,000 Pipeline Perdido Key
1987 200,000 Hopper Gulf Disposal
(approx.)
Sand Quality and Quantity
As a first determinant of the amount of sand to be placed during the
channel deepening phase, an effort was carried out to quantify the amount of good quality sand available which could feasibly be placed on Perdido Key. This would represent the upper limit of material to be recommended. Sand quality as used here is based on grain size and visual evidence, primarily color which is a good indicator of organic content.
The bases for determination were the vibrocore data and quantities to be dredged. Figure 3 presents the overall layout of the channel and the locations of the vibrocores. The quality of material in each of the cores was defined by: (a) logs or general description from visual inspections of the cores, (b) size analyses at several depths along the cores, and (c) color photographs along the entire length of the cores. The latter proved to be invaluable.
Prior to discussing available sand characteristics, it is relevant to note that, as shown in Figure 1, the entrance channel had been defined in three reaches, with the central reach, Reach 2, as that reach which could provide sand to Perdido Key. The boundary between Reach 1 and Reach 2 had been established earlier based on material quality, reportedly in discussions with the State of Florida. The boundary between Reach 2 and Reach 3 was based on economic considerations, i.e. seaward of this juncture it is considered to




Figure 3. Locations of Vibrocores.
14




be less costly to transport sand seaward than to Perdido Key. Figure 4 presents an estimate of the volumetric distribution of sand dredging required as a function of position along the channel.
Amount of Acceptable Material Available
As described briefly previously, the amount of acceptable quality
material expected to be available for placement on the beach was developed primarily through examination of vibrocore information at the 48 locations
shown in Figure 3.
As might be expected, it would always be helpful to have more information to define completely the distribution of acceptable material in the planned dredge area. However, it is believed that with the data presently available it is possible to identify sufficient quantities of good quality sand to meet the objectives of this study. In those limited areas where uncertainties remain, it will be necessary to maintain flexibility in the field operations with special monitoring during dredging. If the Corps/Navy is unwilling to maintain this flexibility and field vigilance, it will be recommended that these areas of uncertainty be deleted from further consideration.
Figure 5 is an annotated version of Figure 4 and includes description of the quality of the material. Several areas can be grouped as presented below and summarized in Table III.
Station 207+60N to Station 107+-90N The material characteristics within these stations are described by cores 1-19 and although there is some good material in this area, the locations of acceptable material are somewhat spotty and it is recommended that all of this material in this segment be regarded as unacceptable. It is noted that this length of undesirable material is greater than previously identified as Reach 1.
Station 107+90N to Station 61+50N The quality of material within this 4,640 ft segment is defined by Vibrocores 20 through 25. The material contained in these cores is uniformily good down to an elevation of -48 ft which is the greatest dredging depth considered in this segment. The amount of material expected to be dredged in this segment is 1,250,000 yd3
Core 26 This vibrocore was taken on the westerly side of the
navigational channel and is uniformily very poor. Referring to Figure 4, it




U-.1
5J0 CC.Z
O
500-

200 100 0 100 200

Station South
K -'Reach 3

Station North

Reach 2

F"

Distribution of Required Total Dredging Pensacola Homeport. Includes Advance and Allowable Overdepth Dredging Quantities.

Pensacola Naval Air Station 240( '

Perdido Key

Reach 3

Sta. 199+50S

Figure 4.

Reach 1




-J
0 500-

All Acceptable ve Elevation: 41 ft

Unacceptable (Core 26)

200 100 0 100 200
Station South Station North

Reach 2

Reach 1

Distribution of Required Total Dredging Pensacola Homeport and Quality of Material. Includes Advance and Allowable Overdepth Dredging Quantities.

Pensacola Naval Air Station
24W0 Sta 25+6N
Reach

Island

Reach 3

Sta. 196+50S

K- Reach 3

Figure 5.

F B




TABLE III
SUMMARY OF AVAILABLE MATERIAL QUALITY AND QUANTITY
PENSACOLA BAY CHANNEL DEEPENING

Stations Material Quality Volumes of Material
Defined by Cores in Segment (yd3) Comments
From To From To Total Acceptable

4,540,000
1,250,000 330,000 1,070,000
1,490,000 1,000,000 1,590,000 470,000 270,000 220,000 220,000
70,000 negligible

0
1,250,000
0
1,070,000 600,000 1,000,000 1,590,000 260,000 270,000 160,000 220,000
0
negligible

All material unacceptable. Segment limits expand those previously defined for unacceptable material. All material uniformily good. All material unacceptable. Limits not well-established. All material acceptable. Only material above -41 ft elevation recommended for beach placement. All material of good quality. All acceptable. Material above elevation -44 unacceptable, remainder acceptable. All of good quality, but probably too localized for beach placement. Top 2 ft of poor quality, rest acceptable.
Good quality.
All of poor quality. Top 7 ft of acceptable quality, remainder unacceptable.

207+60N 107+90N
61+50N 23+60N
7+60S 41+50S 92+50S
112+60S

107+90N
61+5 ON
23+6 ON 7+60S 41+50S 92+50S
112+60S
196+50S




is seen that this core corresponds to an area of maximum dredging. For purposes of estimation at this location, one-half of the material has been considered as characterized by Core 26 and one-half by Cores 25 A and B. This is an area where better definition would be desirable and it will be necessary to recognize that a portion of the material in this section of the channel will be acceptable and a portion will not be suitable for placement on the beach. With the definition allowed by the present cores, this determination must be made in the field. This will require special consideration and field care in this area; if it is not practical to retain this flexibility, it is recommended that the material in this segment be deleted from consideration for beach placement.
Stations 61+50N through Station 23+60N The material in this segment as defined by Vibrocores 27 through 28 is consistently good. It is estimated that 1,070,000 yd 3of material, all suitable fo r beach placement, will be yielded in this segment.
Stations 23+60N through Station 7+60S The material in this segment is described by Vibrocores 29 through 32. The material in the upper portions of each of these four cores is of good quality but that below elevations ranging from -41 ft to -45 ft is unacceptable. Two possibilities are present here. The first would be to place that material above the -41 ft horizon on the beach and to dispose of the additional material elsewhere. The alternative would be to place none of this material on the beach. It is estimated that 600,000 yd3 of good quality sand could be produced above the -41 ft horizon.
Station 7+60S to 4 1+50S Vibrocores 33 36 define the material
characteristics in this segment. All of this material is acceptable. The southerly limit of this segment was defined by the earlier established boundary between Reach 2 and Reach 3. It is recalled that this had been determined as the break-point south of which it would be more economical to dispose of the material at sea. The estimated quantity of good quality material in this segment is 1,000,000 yd3
Station 41+50S to Station 92+50S -The material characteristics in this segment are described by Vibrocores 37 -41 and are uniformily good down to the base channel elevation. It is estimated that 1,590,000 yd 3 of high quality material are available in this segment.




Station 92+50S to Station 112+60S The material characteristics in this segment are defined by Vibrocores 42 and 43. There is a top layer of poor quality material underlain by good sand. The elevation of the interface ranges between -42 to -44 ft and for this situation, it would be feasible to remove the top layers, say down to -44 ft, with disposal offshore and place the underlying material on the beach. It is estimated that the volume of acceptable material is 260,000 yd.
Station 112+60S to Station 196+50S The total quantity of material in this segment is relatively small (760,000 yd3) and is fairly irregular in quality. In particular, all of Core 44 is of good quality. The top 2 ft of Core 45 is of poor quality yet the remaining material is acceptable. Core 46 appears good, Core 45 is all of poor quality, Core 48 is of good quality for the top 7 ft and poor for the underlying layers and finally Core 48 appears uniformily bad. It is recommended that none of this material be placed on Perdido Key.
Summary of Available Material Quality
Table III presents a summary of material quality along the channel and Table IV provides additional summarized information.

TABLE IV
OVERALL SUMMARY OF MATERIAL QUANTITIES AND

QUALITIES

Description of Material Characteristics Total Volume (yd )
Total volume to be dredged 13,300,000
Total volume acceptable 6,420, 000
Total volume acceptable within Reach 2 3,920,000
Total volume acceptable in Reach 2 without
special care 3,320,000
Total volume acceptable if extend limits of
Reach 2 to 92+50S 5,510,000
Total volume acceptable without special care if extend
limits of Reach 2 to 92+50S 3,660,000




HISTORICAL SHORELINE CHANGES

This section reviews various sources of data from which one can infer historical rates of shoreline change.
Florida Department of Natural Resources (1974-1984)
The Division of Beaches and Shores of the Florida Department of Natural Resources maintains a monumented baseline along those 24 counties in Florida which have predominantly sandy shorelines. The monuments are at nominal spacings of 1,000 ft and provide an excellent base from which to conduct repetitive measurements of shoreline position. In Escambia County, complete sets of measurements have been conducted in 1974 and 1984. The results are presented for the eastern end of Perdido Key in terms of annual rates of shoreline changes in Figure 6. The monument locations along Perdido Key and Santa Rosa Island are presented in Figure 7. The results, which have been smoothed, show an average erosion rate on the order of 4 to 5 ft. per year decreasing toward the west. Near DNR monument 64, there is an area where accretion had occurred during the 10 year period. This area is located in the vicinity of Caucus Shoals and it is believed that this is an anomalous feature. Within the seven mile region shown in Figure 6, the loss in plan area is approximately 150,000 ft 2/year, which using a conventional "rule for thumb" suggests an approximate volumetric loss of 150,000 cubic yards annually. Although not shown in Figure 6, the additional loss rate west of DNR monument 30 is at least 100,000 cubic yards per year. This is consistent with prevailing estimates of the net annual longshore sediment transport in this area at approximately 20.0,000 yd3/year toward the west.
Beach Restoration, Summer 1985
In July, 1985, in conjunction with maintenance dredging, approximately 2.4 million cubic yards of generally good quality sand was placed along the eastern end of Perdido Key. Placement occurred over approximately 4,000 ft of shoreline length. At the time of placement, the eastern end of Perdido Key was in a fairly advanced state of erosion as a result of the impact of interruption of the natural littoral transport from the east by dredging of the navigational channel. Unfortunately, there has been no concerted effort to document the performance of this project; however, in conjunction with




+5.0

-5.0

30 40 50 60

FLORIDA DNR MONUMENT NUMBER

Shoreline Change Rates for Escambia County, January 1974 to October 1984. Based on Florida DNR Surveys. Note Shoreline Change Rates Shown Have Been Smoothed by a Five Point Running Average.

Figure 6.




Np
.Seoglodes
- .. "T O
.. 40
- oo g 4X\C O
o oBeach Segm
RIO 0 Nourished in
Figure 7. Locations of DNR Monuments and Segment Nourished in 1985.




their National Park Service responsibilities, investigators from Rutgers have conducted limited measurements, the analysis of which will be discussed in later paragraphs. Hurricane Elena occurred in September, 1985, shortly after completion of the project. Although the effects of this hurricane on Perdido Key were substantial, it is believed that the eastern end of Perdido Key would have suffered much more degradation if the restoration project had not been in place.
Shoreline Changes Information provided by Rutgers included shoreline position measurements at 33 locations of monuments maintained by the Florida Department of Natural Resources. These monuments are numbered 34 through 66 and are approximately 1,000 ft apart; see Figure 7. The 1985 restoration segment encompassed Monuments 61 through 64. Rutgers provided survey information for the following dates
October 1984
April 1985 (Pre-nourishment)*
September 1985 (Post-nourishment and post Hurricane Elena)
May 1986
September 1986
February 1987
July 1987
(*Note: Nourishment occurred in July 1985)
Prior to presenting the analysis of the Rutgers results, a brief
presentation will be made of the expected behavior of an idealized beach restoration project on a long straight shoreline. Figure 8 presents as a bold line an idealized initial rectangular planform distribution of a nourishment project. For the idealized case of an infinitely long coastline, a simplified solution (summarized in Appendix II) is available for the evolution of this planform. An example of the solution is presented as the additional lines in Figure 8. It is seen that the sand spreads laterally, nourishing the adjacent beaches as a result of sand transported out of the nourished area. The rate at which this evolution occurs depends on the wave height raised to the 2.5 power, and inversely on the project length. As mentioned, actual project behavior deviates from the idealized results presented above; however, the idealized treatment provides a framework against which to evaluate actual




O C
0
M
- 0-1. 00
ALONGSHORE DITAC (mies y10ft) -M0 0 a
= D0
z
-~ 0
0 C
20
-2.0 -1.0 0 1.0 2.0
ALONGSHORE DISTANCE (miles)

Figure 8. Example of Evolution of Initially Rectangular Beach Planform on a Long Uninterrupted Shoreline.




performance. Detailed results from the idealized solution will be used to evaluate the 1985 nourishment project.
The Rutgers' tabulated results for shoreline position are presented as Table V. Prior to analyzing these data, several features are noted. The positions are presented for the NGVD (National Geodetic Vertical Datum) contour, which is approximately the mean sea level contour. All positions are relative to April, 1985. Although a separate column is not presented for the April survey, if it were, all entries would be zeros, since these are the reference values.
It is evident, examining the September 1985 survey, that the nourishment took place over DNR monuments 61-64 a distance of approximately 4,000 ft.
As a visual indication of the evolution of the beach fill over time, the average shoreline change over FDNR ranges 61-64 has been plotted in Figure 9. It is seen that the shoreline eroded an average of about 82 ft from October 1984 to April 1985, followed by an increase of approximately 525 ft due to the nourishment project. During the subsequent 1.8 years (September 1985 to July 1987), the shoreline within Ranges 61-64 eroded approximately 197 ft.
An additional simple and informative result is obtained by establishing the percentage loss of sediment within the area placed. Considering sand to have been placed in the area represented by FDNR range monuments 61-64, the results presented in Table VI-are obtained.
Based on the results of Table VI, by July 1987 approximately 35% of the material present in September 1985 was transported out of the nourished segment. Using results from the idealized analysis described in Appendix 11, an effective wave height of approximately 1.1 ft can be determined as a mobilizing agent for the placed sand. This effective wave height will be useful in later calculations of evolution of a nourishment project.
Aerial Photography
Aerial photography of the area was provided by the U.S. Army Corps of
Engineers for the periods 1969, 1976, 1985 and 1986. In addition for purposes of this study, additional black and white and color photography was flown in October, 1987. The dates, scales and other information relevant to this photography are presented in Table VII.




TABLE V

SHORELINE CHANGE DATA
(Distances

FURNISHED BY RUTGERS in Meters)

ngvd change Apr 85 (datum) ,
DNR
monume :nt oct 84 sep 85 may 86 sep 86 feb 87 jul 87

34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

8.390
-8.800
-20.470
-1.910
-17.720
-3.920
-0.340
-6.300
-20.650
-3.350
-12.880
-2.490
-2.840
-17.430
-8.880
-5.250
-0.650
-7.620 7.540 9.080 19.790 5.860 4.880 13.760
-2,480 16.660 25.690 33.020 30.220
-9.990 15.620

-2.840 4.130
-10.850
-9.400
-7.030
-10.470 0.300
-0.010
-0.160
-2.530
-1.690
-3.270
-5.660
-9.390
-8.030
-9.310 17.720
-20.260
-8.070
-3.200
-8.000
-5.520
-21.470
-19.150 11.650 53.260 117.560 169.810 186.070 175.740
-0.580
-9.910

-19.320
-14.220
-21.550
-18.150
-18.790
-14.780
-14.950
-8.650
-19.590
-16.620
-27.090
-22.900
-13.060
-22.760
-25.190
-17.940
-21.540
-19.890
-15.480
-12.880
-25.590
-5.890 18.240 40.680 101.080 131.900 148.530 129.620

-16.110
-10.160
-18.750
-22.550
-9.520
-15.280
-14.340
-3.120
-19.200
-14.140

-13.320
-9.870
-12.000
-27.280
-21.030
-22.620
-23.130
-10.750
-13.80
-9.9100.960 33.420 68.000 132.970 143.430 146.980 121.080
-1.080 20.140

-1.660
-8.150
-21.130
-11.890
-18.100
-3.910
-7.350
-10.030
-23.460
-15.000
-24.650
-17.420
-21.670
-22.370
-4.370
-12.380
-5.070
-11.060 10.850 7.160
-4.280
-1.410
-9.130
-8.580 18.700 45.780 97.300 107.770 107.090 119.640
2.750

-12.85
-12.61
-22.73
-19.11
-20.72
-13.01
-8.25
-12.12 3.61
-8.31
-7.43
-3.87

-3.17
-7.42
-1.81
-14.2 ,
-11.71
-31.38
-11.06
-8.91
-5.8
-3.07
-8.95
3.51 28.32 54.71 97.36 114.70 113.37 94.09
-12.56




It
(0~.
wE
OCn
2o cc 2
,40

600 500
400
300
200 100

0

S100
a

Hurricane
Elena
.C
Il 0
0
_o --...
z
I

- i

200J F MAMJ J ASO ND J FMA MJ J ASOND J FM AMJ J AS ONDJ FMA MJ J AS
1984-4 1985 1986 @0< 1987
5r19884- I-1 98
Figure 9. Average Shoreline Changes Over DNR Ranges 61-64 Encompassing Shoreline Segment of 1985
Nourishment.

1 1 1 I I 1 I I 1 1 1 1 I I I I I I I I I I I I I I I I I I I I I I I I I I I

1

m




TABLE VI
PLAN AREA CHANGES ASSOCIATED WITH 1985 NOURISHMENT
Dates Plan Area Changes (ft2)
April 1985 to September 1985 + 2,128,400 ft2
September 1985 to July 1987 753,400 ft2

TABLE VII
CHARACTERISTICS OF AERIAL PHOTOGRAPHY USED IN

THIS REPORT

Photography Date Scale Type Comments
April 1969 1:12000 Black and White Eastern 8,000 ft of
Island Not Covered
March 1977 1:24000 Color All of Park System
Covered
September 1985 1: 12000 Black and White All of Park System
Covered
March 1986 1: 12000 Color All of Park System
Covered
October 1987 1: 24000 Black and White All of Park System
Covered
October 1987 1: 12000 Color All of Park System
Covered




The aerial photographs were digitized, adjusted to a common scale, plotted and are presented in Figure 10. The correct alignment of the photographs is critical to an accurate determination of shoreline changes and for this purpose a road intersection was used on the western end of the region of interest and an identifiable feature on Fort McRee was used on the eastern end. As noted in Table VI, the 1969 photography did not include the eastern 8,000 ft of the island. This has resulted in less confidence in the photography alignment, with these uncertainties greatest toward the east. Additionally, the generally small scale of all but the 1987 aerial photography results in relatively low confidence in quantitative shoreline changes.
The aerial photographs were analyzed to determine the shoreline changes
in the vicinity of the 1985 beach nourishment. These results are presented in Figure 11 for the time intervals 1977 to 1985 and 1985 to 1987. The first time period includes the 1985 nourishment and Hurricane Elena. It is seen that the ambient erosion over the 1977 to 1985 period (8.5 years) is on the order of 150-200 ft., part of which may be attributed to the erosional trend in this area and part due to the impact of Hurricane Elena. The nourishment has spread out beyond the limits where it was placed and also more than compensates for the erosion in the placement area. During the 1985 to 1987 interval, erosion has occurred in the nourished area and the adjacent shoreline has been relatively stable. This time interval (2.1 years) is too short to develop quantitative results; however, it is clear that a portion of the nourished area has eroded and appears to be of benefit to the adjacent shorelines. In summary, the results of the aerial photography analysis are in qualitative agreement with the more reliable survey data of Florida DNR and Rutgers.
SEDIMENT ANALYSIS
During the field visit, 32 sediment samples were taken both within and outside of the 1985 nourished area. These samples generally extended across the beach profile and included material from the dune, berm, beach face and offshore bar. These samples were subsequently analyzed by Thompson Engineering Testing, Inc. (Job #1666-A87670, Report No. 1) for size distribution and calcium content. It had been reported that the calcium carbonate (shell) content of the nourishment material was significantly higher




Escambia County, Perdido Key Sacle: 1"=4000ft.
.- .
I IIIIII I 1 11 1 I I1 I II11 1 I1 I I I I I /
1969/04 Photos
+ = Locations of Florida DNR Monuments 1975/09 Photos
1986/03 Photos
FLORIDA DNR MONUMENT NUMBER 1987/10 Photos
I I I II I I I I I I I I I I I I I I I I I I I I I I I I I

Figure 10. Location and Characteristics of Recommended Beach Nourishment.




West

Approximate Limits IS 1985 NourishmeLt"

March 1977 to Sept. 1985 (includes 1985 Nourishment and Hurricane Elena)

\ N --Sept. 1985 to October 1987

/
~ -

1I 1 Mile -1

II I I I I I I I I I I I

DNR RANGE MONUMENT NUMBER

Figure 11.

Shoreline Changes in Vicinity of 1985 Beach Nourishment. Based on Analysis ot Aerial Photographs.

+500r

-500




than the native material and therefore quantification of this parameter was of interest. The locations of the samples and the median size and calcium carbonate content are presented in Table VIII. Column 4 indicates whether or not the sample was located in the 1985 nourishment area. The samples RX-1,2,3 were located adjacent to the Park Headquarters.
In order to determine whether or not the nourished material was
significantly different than the native properties (median diameter and calcium carbonate), these properties were averaged for common positions across the beach profile for areas within and outside of the 1985 nourishment limits. These results are presented in Table IX.
Prior to discussing the averages, it should be noted that there is
significant variability in some of the individual parameters, especially the calcium carbonate content. Returning to Table IX, the only significant differences in diameter are for "Near the Dune Line". Presumably the reason is that outside the fill area, these sediments have been transported by wind; as a result only the smaller grains have been transported to and deposited in this area. The similar grain sizes on the beach face could be the result of the relatively high transport activity in this region. Although the diameters "midway across the berm" within the fill limits are slightly coarser than outside, it is somewhat surprising that these differences are not greater. The diameters at the five foot depth, usually on the bar, are essentially the same inside and outside of the fill limits. This is due to offshore transport of the finer material, leaving the coarser material on the more energetic beach face. With the exception of the beach face and five foot depth, the average calcium content is substantially higher within the fill limits. This is consistent with (1) the active transport on the beach face, and (2) the selective transport of the finer materials offshore and the tendency for the shells to be coarser than the sand.
In summary, although the sediment properties did exhibit some differences within andoutside of the fill limits, they are not so large as to be regarded negatively. Moreover, with the beach system exposed to a wider range of storm and normal wave processes, it is anticipated that any noticeable differences will tend to diminish with time.




TABLE VIII

SUMMARY OF SEDIMENT SIZE AND CALCIUM CARBONATE CHARACTERISTICS
Sample Percent Median In 1985 Comments
Designation Calcium Size, D50 Nourishment
Carbonate (mm) Area?
R61-1 2.2 0.49 Yes Near Old Dune Line
R61-2 2.8 0.38 Yes Midway on Fill to Water
R61-3 4.5 0.51 Yes Beachface
R61-4 < 0.2 0.31 Yes Bar Crest, Approx. 5 ft
Depth
R62.5-1 0.3 0.49 Yes Near Old Dune Line
R62.5-2 0.5 0.41 Yes Midway on Fill to Water
R62.5-3 5.2 0.50 Yes Beachface
R62.5-4 0.4 0.31 Yes Bar Crest, Approx. 5 ft
Depth
R64-1 0.2 0.33 Yes Near Old Dune Line
R64-2 0.2 0.33 Yes Midway on Fill to Water
R64-3 3.9 0.54 Yes Beachface
R64-4 0.2 0.32 Yes Bar, Approx. 5 ft Depth
R64-5 < 0.2 0.30 Yes Natural Dune
R67-1 < 0.2 0.33 No Near Dune Line
R67-2 < 0.2 0.37 No Midway from Dune to Water
R67-3 1.0 0.33 No Beachface
R67-4 < 0.2 0.37 No Approx. 5 ft Depth, No
Bar
R65-1 < 0.2 0.30 No Near Dune LIne
R65-2 < 0.2 0.31 No Midway from Dune to Water
R65-3 5.4 0.35 No Beachface
R65-4 < 0.2 0.25 No Approx. 5 ft Depth, No
Bar
R57-1 < 0.2 0.36 No Near Dune Line
R57-2 < 0.2 0.37 No Midway from Dune to Water
R57-3 3.3 0.45 No Beachface
R57-4 0.2 0.30 No Outer Bar Crest, Approx.
5 ft Depth
R55-1 < 0.2 0.36 No Near Dune Line
R55-2 < 0.2 0.32 No Midway from Dune to Water
R55-3 4.2 0.50 No Beachface
R55-4 0.2 0.30 No Outer Bar Crest, Approx.
5 ft Depth
RX-1 0.2 0.37 No Beach, No Dune
RX-2 1.9 0.45 No Beachface
RX-3 0.4 0.29 No Outer Bar Crest, Approx.
5 ft Depth




TABLE IX
CHARACTERISTICS OF SEDIMENT SAMPLES
INSIDE AND OUTSIDE OF 1985 NOURISHMENT LIMITS
Beach Profile Median Diameter (mm) Calcium Carbonate Percentage
Feature Inside Fill Limits Outside Inside Fill Limits Outside
Near Dune Line 0.44 0.34 0.9 < 0.2
Midway Across Berm 0.37 0.35 1.17 < 0.2
Beach Face 0.44 0.42 3.3 3.2
Bar Crest or Five
Foot Water Depth
if Bar Not
Present 0.31 0.30 0.3 0.2
RECOMMENDED INITIAL PROJECT CHARACTERISTICS AND EVOLUTION OF THE PLANFORM Initial Planform
The most relevant parameters of the initial planform are the length, k, the width, w, and the transition characteristics at the end of the project. Using accepted procedures, the additional width, w, for various lengths and nourishment quantities are presented in Table X. To provide a basis for comparison, the average shoreline advancement associated with the 1985 nourishment was approximately 525 ft.
TABLE X
INITIAL PLANFORM CHARACTERISTICS

Project Additional Beach
Volume Placed Length Width
(yd3) (miles) (ft)
4 95 ft
2,000,000 6 60 ft
4 180 ft
4,000,000 6 120 ft
4 285 ft
6,000,000 6 180 ft
5,000,000 4.5 270 ft*
(with tapered ends)
*Recommended Plan




Planform Evolution
Considering the nourishment to occur over a beach segment encompassed by FDNR Ranges 40 through 64 (4.5 miles), the recommended planform is presented in Figure 12 and the anticipated evolution is presented in Figure 13. Figure 13a presents the planform at 2, 5 and 10 years for an otherwise stable shoreline and Figure 13b presents the planform at the same time periods for the more realistic case of a shoreline eroding at 5 ft. per year. In Figure 13, the shoreline has been drawn straight for convenience rather than curved. Also, the jetty at the northeastern end of Perdido Key (near DNR monument 67 is included).
Beach Profile
The planform characteristics presented in the preceding section and in
Table X have been based on the consideration that one cubic yard of sand along one foot of beach length will cause a shoreline advancement of one foot. Thus, this one cubic yard (27 cubic feet) is distributed such that it causes a uniform profile advancement of one foot over a vertical portion of the profile of 27 ft. The placement options include placing the material to a shallower depth which means that the shoreline advancement must be greater. With this placement strategy, the waves will ultimately redistribute the sand to greater depths to yield the one foot shoreline advancement per cubic yard of sand per unit length of beach. Figure 14 shows these two options and the recommended profile shoreward of the equilibrated position of the initial shoreline. The purpose of the lower berm (4 to 5 ft.) compared to the natural berm height (approximately 6 ft.) is to allow the wind and water processes to exert their respective shaping processes, thereby yielding a more natural profile.
BIOLOGICAL CONSIDERATIONS
No specific studies have been conducted to determine the effect of the 1985 beach nourishment on the biology of Perdido Key. However, monitoring studies have been conducted of other projects and these results allow the probable impact to be inferred.
The information below is drawn primarily from an excellent review by
Nelson (1985) of the effects of beach nourishment on the nearshore biota. The primary focus will be on three common nearshore organisms: (1) Emerita talpoida (mole crabs), (2) Donax (coquina clams), and (3) Ocypode (ghost crabs).




0 5
I I I I

Scale(miles)

Project Characterists

Recommended Nourishment in Connection with Channel Dredging
{ Volume: 5 Million Cu. Yds. Length: 4.5 Miles Additional Beach Width: 270 Ft.

Figure 12. Location and Characteristics of Recommended Beach Nourishment.




.-0
30( LU
0
z I
-n

Scale (miles)

40 50 60
DNR MONUMENT NUMBER a) Calculated Evolution of Recommended Nourishment If Shoreline Were Stable.

West

Jetty

U
co 03.

Initial

40 50 60 Jetty
DNR MONUMENT NUMBER
b) Calculated Evolution of Recommended Nourishment on a Shoreline Eroding at a Rate of
Five Feet Per Year.

Figure 13. Calculated Evolution of Recommended Nourishment Planform for Stable and Eroding
Beaches.

Initial




20
O 1 0 Natural Berm Elevation 6 +ft
S+5ft +4ft
z
,,, 28_o+t4
0
.0 0
z
O Recommended
P" Nourishment Profile
< 10
> -10 DNR Profile
W Measured October 31,1984
w
-20
I I I I I I I
0 300 600 900 1200 1500 1800
DISTANCE GULFWARD FROM DNR MONUMENT R-48 (ft)

Recommended Characteristics of Nourished Profile. Illustrated for DNR Monument No. 48

Figure 14.




Emerita Talpoida (Mole Crabs)

This organism is a filter feeder that burrows in the lower foreshore of the beach and can be very abundant, although the densities tend to be very irregular. The highly energetic swash zone appears to be the preferred environment for E. Talpoida probably enhancing the food supply. Densities in excess of 3,700 animals per square meter have been reported (Bowman, 1981). The animals tend to be in greatest abundancies in Florida in December to January.
E. Talpoida are very mobile and apparently have the capability to avoid being buried by beach nourishing by leaving an area. In a project in which 956,000 m 3 sand was placed on the Cape Hatteras beach, Hayden and Dolan (1974) found no dead animals and they concluded that the affected areas recovered in less than two weeks. The sand used in this nourishment project was quite comparable to the native sand. A second project of similar quantity (904,000 m 3) at Fort Macon, N.C., was monitored by Reilly and Bellis (1978, 1983); however the sand was taken from dredged harbor sediments and was not compatible in size characteristics. Additionally the sediment was from a reducing enviornment. The monitoring indicated that the E. Talpoida populations were nonexistent in the project area during material placement but recolonized rapidly several months later during the spring recruitment period. A delay of one month during the recruitment period was evident. The summer after the commencement of nourishment (the preceding December), the. animal densities were the same on the nourished and control beaches. However, there were significant differences in the size classes with the nourishment containing exclusively juveniles. The investigators concluded that the adult mole crabs in the vicinity of the nourished site were killed by turbidity and that the juvenile animals had populated the area from the adjacent beaches. Nelson (1985) has suggested that the liberated hydrogen sulfide in the nourished sediments may also have contributed to the mortality of adult animals.
In summary of the impact of beach nourishment on E. Talpoida, it is
concluded that these animals are very mobile and are able to vacate an area unsuitable for their physiology. Moreover, with the return of favorable conditions, they rapidly recolonize the area. If the material placed is compatible with that originally on the beach, effects are of quite short




duration. If poor quality sediment is used, recovery is slower, but still relatively rapid, probably due to the high motility of these animals and the longshore currents on the beachface.
Donax (Coquina Clams)
This genus of bivalves has two species that have been reported to be
found in the Florida panhandle area. The documented range of Donax Variabilis is from Virginia Beach, VA to Mississippi. Also Donax Texasianus has been found in the Florida panhandle.
Most Donax Variabilis migrate up and down the beach with the tide,
presumably to be in the active swash zone where the high velocities ensure ample quantities of moving water from which these filter feeders obtain nourishment. However some studies have reported populations that do not migrate with the tide. The life of Donax is generally 2-3 years with one or two spawning periods per year. Primary spawning occurs in February and in Florida a second spawning may occur in June. The peak seasonal abundance tends to occur in June and July. Maximum densities of Donax Texasianus in Panama City, Florida was 2,050 animals/m2.
Few studies are available documenting the effects of beach nourishment on Donax. Reilly and Bellis (1978, 1983), reporting on the effects of nourishment on a North Carolina Beach found that following a December nourishment event, Donax were not found in the nourished area until the following July. These were young believed to be transported in by the longshore currents and it was suggested that the adults were killed by burial in the offshore area.
Ocypode Quadrata (Ghost Crab)
These animals burrow in the dry beach although they do lay their eggs in the water. The older crabs tend to burrow higher on the beach than the young animals. Their diet varies from dead plant and animal material to live Donax and Emerita. Although seen frequently during the daytime, they are primarily nocturnal.
Only the studies of Reilly and Bellis (1978, 1983) have evaluated the effects of beach nourishment on ghost crab populations. Their limited data




indicated that the summer following nourishment, there was a 50% lower population. Their interpretation was that, since the material was placed below a level that would cause direct burial and since the crabs could probably burrow up through placed sand, it is likely that the reduced population was a result of emigration of the crabs due to a reduced food supply.
Panama City Studies
Saloman (1976), Culter and Mahadevan (1982) and Saloman, et.al. (1982) have reported on extensive biological studies in conjunction with the 1976 nourishment of some 300,000 cubic meters along the beaches of Panama City.
Saloman (1976) conducted a pre-nourishment baseline study in 1974-1975 and documented the effects of Hurricane Eloise (September, 1975) on the biota. It was found that there was no decline in the abundance of intertidal animals following the hurricane.
Culter and Mahadevan (1982) conducted studies in 1979-1980 to examine long-term effects of the 1976 nourishment. They concluded
"No long-term adverse environmental effects as a
result of beach nourishment could be detected within the nearshore zone of the Panama City beaches. There
were also no adverse or stressful conditions present
at the borrow sites."
Saloman, et.al. (1982) carried out a study analyzing data collected
between April 1976 and November 1977. The purpose of the study was to examine short-term effects of offshore dredging on the benthic community. It was concluded that there was an immediate decline in the benthic community; however, the populations rapidly recovered and were virtually at preconstruction levels within one year. It was noted that the borrow pits were relatively small and no more than 5 m of sand (vertically) was removed from each pit. The pits were located in water depths of 6 to 9 m. Initially the pits filled with material finer than on the adjacent bottom; however, these differences tended to diminish with further filling.




Summary Regarding Biological Effects of Beach Nourishment

Based on a comprehensive review of published information, Nelson (1985) has concluded that the intertidal beach organisms are well adapted to this high energy environment including times of significant erosion and accretion and fluctuations in turbidity. During and immediately following storms, massive erosion and deposition occur over segments of beaches long in comparison to nourishment projects. Thus any adverse effects of beach nourishment carried out with compatible sand tend to be short-lived as the animals can either survive the event or are adapted to rapid lateral decolonization. Nelson notes that although the available evidence indicates minimal and short-lived biological effects, the present level of understanding is such that biological monitoring programs are necessary to further document the quantitative impacts of beach nourishment projects.
RECOMMENDATIONS
The following recommendations are made based on the results of this study. In conjunction with the construction dredging of the Kitty Hawk channel, it is recommended that up to a total of 5,000,000 cubic yards of material be pl ced along a 4.5 mile segment along the eastern end of Perdido Key as presented in Figure 12. Based on historical erosion data, implementation of this recommendation would still fall short of restoring the shoreline to the condition that would prevail if channel deepening projects had not interfered with the natural processes. Based on Florida Department of Natural Resources shoreline change data, this nourishment project would reinstate the shoreline to its approximate condition some 20 years ago. Moreover, this project should fill in and "arrest" to some extent the shoreline erosional wave which is now moving to the west.
Soon after placement of the material, it is recommended that sea oats and possibly other natural vegetation be planted to enhance dune formation and early return to a more natural condition.
It is recommended that the above project be monitored to determine the physical evolution and biological effects. A preliminary description of a monitoring programto document the physical effects is presented in Appendix 1; it is recommended that the monitoring program continue for at least five years.




If the project performs as expected with erosion of material in the
region placed and transport to and deposition in the beach segments adjacent to the placement area, it is recommended that during future channel maintenance, all beach quality sand up to 300,000 yd3/year be placed on the beach. The most appropriate placement locations will be established as a result of the monitoring efforts.
REFERENCES
Bowman, M.L. (1981) "The Relationship of Emerita Talpoida to Beach
Characteristics," M.S. Thesis, University of Virginia, Charlottesville,
Virginia, 106 pp.
Culter, J.K. and Mahadevan, S. (1982) "Long-Term Effects of Beach Nourishment
on the Benthic Fauna of Panama City Beach, Florida," Miscellaneous Report
No. 82-2, U.S. Army Corps of Engineers, Coastal Engineering Research
Center, Fort Belvoir, VA.
Dean, R.G. (1983) "Principles of Beach Nourishment," in Handbook of Coastal
Processes and Erosion, CRC Press, p. 217-231.
Hayden, B. and Dolan, R. (1974) "Impact of Beach Nourishment on Distribution
of Emerita Talpoida, the Common Mole Crab," Journal Waterways, Harbors
and Coastal Engineering Division, ASCE, Vol. 100, WW2, p. 123-132. Nelson, W.G. (1985) "Guideline for Beach Restoration, Part I: Biological
Guidelines," Report No. 76, Florida Sea Grant College.
Rutgers University (Undated) "Measurements of Shoreline Positions Along
Perdido Key, 1985-1987".
Reilly, F.J. and Bellis, V.J. (1978) "A Study of the Ecological Impact of
Beach Nourishment with Dredged Materials on the Intertidal Zone,"
Institute for Coastal and Marine Resources, East Carolina University,
Technical Report No. 4.
Reilly, F.J. and Bellis, V.J. (1983) "The Ecological Impact of Beach
Nourishment with Dredged Materials on the Intertidal Zone at Bogue Banks,
North Carolina," U.S. Army Corps of Engineers, Coastal Engineering
Research Center, Miscellaneous Report No. 83-3.
Saloman, C.H. (1976) "The Benthic Fauna and Sediments of the Nearshore Zone
Off Panama City, Florida," Miscellaneous Report No. 76-10, U.S. Army
Corps of Engineers, Coastal Engineering Research Center, Fort Belvoir,
VA.




Saloman, C.H., Naughton, S.P. and Taylor, J.L. (1982) "Benthic Community
Response to Dredging Borrow Pits, Panama City Beach, Florida,"
Miscellaneous Report No. 82-3, U.S. Army Corps of Engineers, Coastal
Engineering Research Center, Fort Belvoir, VA.
Thompson Engineering Testing, Inc. (1987) "Grain Size Distribution and Calcium
Carbonate Analyses of Sediment Samples," Contract N62467-85-C-0593,
Amendment/Modification No. P00009, Mobile, Alabama.




APPENDIX I
PRELIMINARY MONITORING PROGRAM TO QUANTIFY PHYSICAL EFFECTS OF BEACH NOURISHMENT ON PERDIDO KEY
INTRODUCTION
The purpose of the monitoring program described below is to establish the physical effects of beach nourishment on Perdido Key. The results of this program will serve to quantify the performance of the nourishment project and to establish optimum quantities and location of material placement in future maintenance programs. The results will be used also to evaluate/improve methods of predicting performance of such projects, an objective of importance to both the Corps of Engineers and the National Park Service. Finally, of special importance will be the evolution of the upper portions of the beach profile (presented in Figure 14) toward more natural vegetation, profile and grain size characteristics than would occur otherwise. The biological monitoring plan will be developed and submitted separately.
MONITORING PROGRAM ORGANIZATION
In accordance with the objectives of the monitoring to be able to
document and predict the performance of the nourishment project, the program is organized into Past, Present and Future components.
Past
This component comprises a historical study to document the changes that have occurred to Perdido Key and the modifications of the large scale "forces", predominantly dredging at the Pensacola Channel and the occurrence of major storms. The effects of recent storms (Camille, 1969; Frederic, 1979; Elena, 1985) have been documented rather well and will serve to assist in quantifying shoreline effects that should be associated with earlier major storms for which the shoreline effects have not been documented.
Present
This component would concentrate on documenting pre-nourishment conditions and the effects of the nourishment project.




Future
Results from the Past and Present programs will be combined to predict evolution of the nourishment project farther into the future. Also the monitoring results will serve as a basis for evaluating and refining present prediction calculation methodology. The revised methodology will be used to evaluate various scenarios for maintenance material placement and through this process, recommendations developed.
PROGRAM DURATION AND ELEMENTS
The recommended duration of the recommended monitoring program is five years with one complete set of measurements carried out prior to commencement of the nourishment project.
The recommended monitoring elements are
(1) Beach and Offshore Profiles All profiles would be carried out at DNR
monument locations. Profiles would be taken at a total of 31 monuments
with:
5 Profiles, Monuments 27-35, Alternate Monuments
10 Profiles, Monuments 36-45, Every Monument
6 Profiles, Monuments 47-57, Alternate Monuments
10 Profiles, Monuments 58-67, Every Monument
These profiles would be taken twice yearly (spring and fall) and after
major storms, extending offshore 1,000 m or to the 8 m contour on the
Gulf side, across the island to wading depth on the bay side. The
wayside profiles need only be conducted during the first survey period
and after storms which affect the dunes and cause washover deposits.
The locations of the profiles are presented in Figure I-1.
2. Sand Sample Collection Samples will be collected in conjunction with
the profiling described above. The samples shall be taken at
representative positions of the profile including: dune, berm, beach face, depths of I m, 2 m, 5 m, 8 m, 10 m on the Gulf side and at the shoreline and at 1 m and 2 m on the bay side. Samples will be taken
with each set of profiles.




4,

0 1 2
Ii ii i l I
Scale(miles)

R-55

Approximate Westerly Park Boundary

I I t i ii i i II I I I II I I I I I I I I I I I I
Possible Location of Directional Wave Gage

I I I
I I I I

I Il t "Z
I ~ I IjO V I 1 1 1 1 1 I I
I'I
Recommended Beach Nourishment

NOTE:
R-40 is Florida Department of Natural Resources Monumented "Range 40"

Figure I-1. Recommended 31 Profile Locations and Location of Directional Wave Gage

R-30




3. Aerial Photographs Black and white and color photography shall be
taken in conjunction with the fall profiling and provided at scales of
1:12,000 (Color) and 1:2400 (Black and White).
4. Directional Wave Gage It is recommended that a directional wave gage
be located in a water depth of approximately 10 m, see Figure I-1.
5. Weather Station A weather station should be installed. The primary
components of the station are: rain gage, recording anemometer (wind
speed and direction) and recording barometric pressure.
6. Ground Photographs Approximately 40 locations of special interest
relative to vegetation growth or shoreline change will be identified
initially and will be photographed on a bimonthly basis.
PROJECT COST
It is envisioned that the physical component of the monitoring program as described herein would cost approximately $200,000 per year for a total of $1,000,000. It is planned that where advantageous to understanding and interpretation, the biological and physical field collection components will be coordinated.




APPENDIX II
GOVERNING EQUATIONS FOR BEACH PLANFORM EVOLUTION
It can be shown that beach profile evolution along a straight shoreline is approximately in accord with the following linear partial differential equation:
ay = B 2y (II-i)
at ax2
in which y is the shore-perpendicular distance from a baseline to a particular contour (which in this case will be mean sea level), x is the alongshore distance, t is time and B is an "activity" coefficient related to breaking or shallow water conditions as:
Breaking Wave K Hb 5/2g1 cos(B-ab)
Conditions: B = (11-2)
8 (S 1) (1 p) (h* + G) (12
2
Deep Water KH gT cos(O a )
Conditions: B = 32w (S I) (1 p) (h,+ G) (1-3)
in which K is a sediment transport coefficient, usually taken as 0.77, H and T represent the wave height and period, respectively, g is the gravitational constant, K is the spilling breaker constant (= 0.8), S is the ratio of sediment density to water density, p is the porosity, (h* + G) is the vertical dimension of the portion of the profile partipating in the profile response, a is the azimuth of the outward shore normal, a is the azimuth of the direction from which the waves originate and the subscripts "o" and "b" denote conditions at deepwater and breaking, respectively.
Considering a nourishment project of uniform width, w, over a length, L, forming a rectangular planform, it can be shown that the solution to Eq. (II-1) is
wL 2x L 2x
y(x,t) = {erf[- ( + i)] erf[-- (- I (11-4)
2 4B L 4YB/
in which "erf" is a mathematical function called the "error function".




The fraction, F, of the fill removed from the region placed due to
longshore sediment transport can be shown to be approximated for early time, t, by
F = '[Bt(11-5)
7rr L
in which t is the time during which the fill is lost.
Considering that 35% of the fill was transported out of the area placed in a period of 10 months (September, 1985 to July, 1987, Table VI), an effective breaking wave height, Hb, can be determined as
L2 F2
B --F
4t
= (4000)2(.35)2 0 2
T (685 x 24 x 3600) 0.026 ft2IS and, from Eq. (1-2)
8B(S 1)(1 p) (h*+ G) 0.4 Kvg-/K cos( ab)
H b [8(.026)(1.65)(.65)(27)] = 1.1 ft
0.77 f32.2/0.78 1
in which the approximation cos(a cb) = 1.0 has been made.
51




Full Text

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UFL/COEL-88/016 RECOMMENDATIONS FOR PLACEMENT OF DREDGED SAND ON PERDIDO KEY GULF ISLANDS NATIONAL SEASHORE By Robert G. Dean January 12, 1988 Prepared for: National Park Service 75 Spring Street, SW Atlanta, GA 30303

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RECOMMENDATIONS FOR PLACEMENT OF DREDGED SAND ON PERDIDO KEY GULF ISLANDS NATIONAL SEASHORE January 12, 1988 Prepared For: National Park Service 75 Spring Street, SW Atlanta, GA 30303 Prepared By: Robert G. Dean Coastal and Oceanographic Engineering Department University of Florida 336 Weil Hall Gainesville, FL 32611

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EXECUTIVE SUMMARY This study has evaluated the volumes of beach quality material available from the dredging planned for the deepening of the Pensacola Bay Entrance Channel. Recommendations have been made for volumes and configurations of placement on portions of the Perdido Key Unit of Gulf Islands National Seashore. The historical shoreline changes and behavior of the 1985 beach nourishment have been analyzed to provide an improved basis for developing recommendations for and predictions of the evolution of any future nourishment. The following summarize the results and recommendations. 1. The dominant sand transport direction along Perdido Key is from east to west and in a natural state; the sand supply to the eastern end of Perdido Key was from Santa Rosa Island across a relatively shallow outer bar. 2. Dredging of the Pensacola Bay Entrance commenced in the 1880's. This previous deepening has caused an erosional stress on the eastern end of Perdido Key. Florida Department of Natural Resources data from 1974 to 1984 document erosion rates on the order of 5 ft. per year amounting to at least 250,000 cubic yards per year. This erosional effect is typical of shorelines located downdrift of modified entrances. 3. Based on analysis of limited shoreline change data collected by Rutgers University, it appears that the 1985 nourishment project is performing in an expected manner with erosion of sand in the region placed, and material transported to and deposited on adjacent beaches. 4. Results from analysis of aerial photographs are consistent with 2 and 3 above. 5. Based on a field trip and analysis of sediment samples, there do not appear to be any significant adverse effects as a result of the 1985 nourishment project, with the nourished region revegetating naturally. 2

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6. Based on an analysis of Vibrocore data along the entrance channel, the material quantities and qualities have been determined as presented in Tables III and IV. 7. It is recommended that consideration be given to placement of approximately 5,000,000 yd3 of sand distributed over a beach segment length of 4.5 miles. After the beach profile has equilibrated, this should advance the shoreline gulfward by a maximum of approximately 270 ft. This material is of high to excellent quality. 8. In some areas of the dredging, the distribution of high quality material was not adequately defined by the cores. In these areas it will be necessary to monitor carefully the dredging operations. If this level of field vigilance is not considered practical, it is recommended that the volume placed be reduced to 3,600,000 yd3 9. The recommended initial planform of the placed material is presented in Figure 12 for a volume of 5,000,000 yd3.The anticipated evolution is shown in Figure 13. 10. It is recommended that the results of this project be monitored and if the results document losses in the placed area and transport to the west as expected, consideration should be given to placing all future maintenance dredging of good quality material on the eastern end of Perdido Key so as to reinstate the sediment transport that existed under natural conditions. A preliminary monitoring plan is presented as Appendix I. 3

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TABLE OF CONTENTS EXECUTIVE SUMMARY .... ............ .. ...........2.......................... 2 LIST OF FIGURES ............................................ 6 LIST OF TABLES ............................................................ 7 INTRODUCTION........................ ....... ......... ...................... 8 OBJECTIVES AND CRITERIA... .............. ......... ......................... 8 Objectives............................................................ 8 Criteria ........................ ...... ...... .. ...... .......... ....... 8 CHARACTERISTICS OF CHANNEL DEEPENING PROJECT AND OTHER RELEVANT INFORMATION ....................... .......... ............................. 8 METHODS................... .......... ................................. ..... 11 Sand Quality and Quantity.. .............. ...... ........ .... ........... 13 Amount of Acceptable Material Available............................. 15 Station 207+60N to Station 107+90N.............................. 15 Station 107+90N to Station 61+50N................................ 15 Core 26.. .................. ........................... .... .15 Stations 61+50N through Station 23+60N......................... 19 Stations 23+60N through Station 7+60S.......................... 19 Station 7+60S to 41+50S. .......................... .............. 19 Station 41+50S to Station 92+50S................................. 19 Station 92+50S to Station 112+60S................................. 20 Station 112+60S to Station 196+50S.............................. 20 Summary of Available Material Quality........................ ......... 20 HISTORICAL SHORELINE CHANGES.................................. ......... 21 Florida Department of Natural Resources (1974-1984)................... 21 Beach Restoration, Summer 1985....................... ... ............... 21 Shoreline Changes. ....... ............. .. ...... ................ .24 Aerial Photography...................... ............................. 26 SEDIMENT ANALYSIS. ... ...... ...... ....... .......... ..... ...... ............. 30 RECOMMENDED INITIAL PROJECT CHARACTERISTICS AND EVOLUTION OF THE PLANFORM. .............. ................. ............... ................... 35 Initial Planform........................................... .......... 35 Planform Evolution .. ................................................ 36 Beach Profile................................................. ...... .36 BIOLOGICAL CONSIDERATIONS............. ...... ...... .... ....... ........ .... 36 Emerita Talpoida (Mole Crabs)....................................... 40 Donax (Coquina Clams). ...................... ........................ 41 Ocypode Quadrata (Ghost Crabs)....................................... 41 4

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Panama City Studies .............. .... ............................ .42 Summary Regarding Biological Effects of Beach Nourishment............. 43 RECOMMENDATIONS........................................................... 43 REFERENCES................................................................ 44 APPENDICES I Preliminary Monitoring Program to Quantify Physical Effects of Beach Nourishment on Perdido Key.............................. 46 II Governing Equations for Beach Planform Evolution................. 50 5

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LIST OF FIGURES FIGURE 1. Channel Layout Showing Three Dredging Reaches..................... 10 2. Interior and Gulf Channel Cross-sectional Characteristics......... 12 3. Locations of Vibrocores............................. ........... 14 4. Distribution of Required Total Dredging Pensacola Homeport. Includes Advance and Allowable Overdepth Dredging Quantities...... 16 5. Distribution of Required Total Dredging Pensacola Homeport and Quality of Material. Includes Advance and Allowable Overdepth Dredging Quantities............................................... 17 6. Shoreline Change Rates for Escambia County, January 1974 to October 1984. Based on Florida DNR Surveys. Note Shoreline Change Rates Shown Have Been Smoothed by a Five Point Running Average .................... ......... ........................... 22 7. Locations of DNR Monuments and Segment Nourished in 1985.......... 23 8. Example of Evolution of Initially Rectangular Beach Planform on a Long Uninterrupted Shoreline................................ 25 9. Average Shoreline Changes Over DNR Ranges 61-64 Encompassing Shoreline Segment of 1985 Nourishment........................... 28 10. Shoreline Position as Determined from Aerial Photography Analysis............................. ..... ...................... .31 11. Shoreline Changes in Vicinity of 1985 Beach Nourishment. Based on Analysis of Aerial Photographs................................. 32 12. Location and Characteristics of Recommended Beach Nourishment..... 37 13. Calculated Evolution of Recommended Nourishment Planform for Stable and Eroding Beaches. ....................... ............. .38 14. Recommended Characteristics of Nourished Profile. Illustrated for DNR Monument No. 48... ............. ............................ 39 I-1. Recommended 31 Profile Locations and Location of Directional Wave Gage......................................................... 48 6

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LIST OF TABLES TABLE PAGE I Chronology of Pensacola Bay Entrance Channel Dimensions............. 11 II History of Maintenance Dredging Pensacola Entrance Channel 1975-1987.................... ............... ................ ...... .13 III Summary of Available Material Quality and Quantity Pensacola Bay Channel Deepening.................... .............................. 18 IV Overall Summary of Material Quantities and Qualities................ 20 V Shoreline Change Data Furnished by Rutgers (Distances in Meters).... 27 VI Plan Area Changes Associated with 1985 Nourishment................. 29 VII Characteristics of Aerial Photography Used in this Report........... 29 VIII Summary of Sediment Size and Calcium Carbonate Characteristics...... 34 IX Characteristics of Sediment Samples Inside and Outside of 1985 Nourishment Limits.................................................. 35 X Initial Planform Characteristics.................................... 36 7

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RECOMMENDATIONS FOR PLACEMENT OF DREDGED SAND ON PERDIDO KEY GULF ISLANDS NATIONAL SEASHORE INTRODUCTION Perdido Key is one of a series of barrier islands along the Florida/Alabama coastline. Under natural conditions the sediment supply for these islands was maintained by transport from the east and the sand was moved across channel entrances by waves and currents acting on broad relatively shallow outer bars of sand. As needs for deeper and more stable navigational channels developed, these channels were deepened and in some cases stabilized by jetties which served to train the tidal flows. These modifications interrupted the natural sediment transport pathway noted above with a resulting erosion of the downdrift shorelines. This scenario applies to the eastern end of Perdido Key, where measurements conducted by the Florida Department of Natural Resources over the 1974-1984 period document rather severe erosion extending more than 8 miles from the eastern island end. The forthcoming deepening of the entrance channel to Pensacola Bay to serve as a homeport for the aircraft carrier Kitty Hawk may further alter natural processes but also provides the opportunity to compensate for past losses through placement of fairly large quantities of good quality sand on the eastern end of Perdido Key. This would be a one-time placement through sand available from channel deepening. Additionally, based on experience, it is likely that good quality maintenance material will be available periodically to serve to reinstate the natural sediment supply. It is important to the quality of Perdido Key to identify the appropriate amounts and placement locations of the sand available from the channel deepening and maintenance dredging. The criterion, consistent with National Park Service policy, is to reinstate, in as natural a manner as possible, the longshore sand flow to the island and to regain a reasonable amount of the sand eroded due to past modifications and dredging practices in the entrance channel. 8

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OBJECTIVES AND CRITERIA Objectives The objectives of the present study are: (1) To review the shoreline change history at the eastern end of Perdido Key. (2) To quantify that portion of shoreline changes associated with past channel maintenance and sand management practices. (3) Consistent with National Park Service policy, to develop recommendations for the amounts and placement locations of sand resulting from: (a) the channel deepening, and (b) periodic maintenance dredging. Criteria The broad criteria employed in approaching the objectives above are: (1) To utilize an appropriate amount of the forthcoming channel deepening material to reestablish the island in the condition that would have prevailed if the long-term dredging had not occurred. (2) Within existing constraints, to reinstate the natural sand transport quantities in the vicinity of the eastern end of Perdido Key. This criterion would apply primarily to the maintenance dredging. CHARACTERISTICS OF CHANNEL DEEPENING PROJECT AND OTHER RELEVANT INFORMATION The Pensacola Bay Entrance Channel has been a Federally authorized channel since 1881. Table I presents the dates associated with various authorized and excavated channel depths and widths. The channel associated with the Kitty Hawk homeporting extends from the berthing docks inside Pensacola Bay westward then southward around the western end of Santa Rosa Island and finally south-southwest to a natural water depth of 48 ft. As presented in Figure 1, the total channel length is approximately 7.7 miles and extends an approximate distance of 4 miles gulfward of the Perdido Key shoreline. Two channel cross-sections are incorporated into the design. From the berthing area to slightly east of the western tip of Santa 9

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Pensacola Naval Air Station ,' lZ Dredge to 48' MLW New Navy Turning Basin .; W 1 Existing Navy Turning Basin redge to -46 MLW 4 pENSACOLA BAY S. anta Rnosa Island Reach 1: Sta. 125+60N to Sta. 207+60N Reach 2: Sta. 41+50S to Sta. 125+60N Reach 3: Sta. 41+50S to Sta. 196+50S 50 Dredge to -46'MLW: Sta. 82+60N to Sta. 207+60N s\a Dredge to -48'MLW: Sta. 82+60N to Sta. 196+50S FLORIDA *96_ v Dredging Depth Include 2' Advanced Maintenance and 2' Allowable Overdepth Figure 1. Channel Layout Showing Three Dredging Reaches 10

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TABLE I CHRONOLOGY OF PENSACOLA BAY ENTRANCE CHANNEL DIMENSIONS Channel Dimensions Authorized Year Depth (ft.) Width (ft.) or Actual 1881 24 80 Authorized 1885 22.5 80 Actual 1890 24 120 Actual 1896 30 300 Authorized 1902 30 500 Authorized 1935 32 500 Authorized 1959 37 800 Actual Present 44 800 Authorized Rosa Island, the nominal depth is 42 ft below MLW; for the remainder of the channel length to its Gulf terminus, the nominal depth is 44 ft. The actual dredged depths will include an additional 2 ft for "advance maintenance" and an additional 2 ft for "allowable overdredging". Thus, as presented in Figure 2a and 2b the dredged depths for the two cross-sections will be 46 ft and 48 ft. The total anticipated dredging for the project is in excess of 13.3 million cubic yards. It is anticipated that the deepening project will commence in October 1988 and continue through 1990. A maintenance dredging project of approximately 200,000 yd3 was conducted in November-December, 1987 with offshore placement. Table II presents the history of maintenance dredging over the period 1975 to 1987. METHODS The overall methods included a site visit, review and analysis of prior studies in the area including data collected by Rutgers, and computations of the behavior and effects of sand placement. The detailed methodology employed and results obtained are presented in the following sections of this report. 11

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Ambient Bottom (Varies in Elevation) 7LU -800 ft j 5 5 --.---------------------------------42 ft Project Depth S--44 ft Includes 2 ft Advance Maintenance Dredging :. ..:. -46-..... -...:.-.-ft Including 2 ft Allowable Overdredging a) Interior Channel Characteristics 10................. ..... 0 i1 J 0 200 t I I |Horizontal and S80 1 Vertical Scales In feet 5 5 ~1----------------------------------1' 4 f rjc et -------------------------------------44ftProject Depth -46 ft Includes 2 ft Advance Maintenance Dredging S. ...: ..: ... ..--48 ft Including 2 ft Allowable Overdredging b) Gulf Channel Characteristics Figure 2. Interior and Gulf Channel Cross-sectional Characteristics.

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TABLE II HISTORY OF MAINTENANCE DREDGING PENSACOLA ENTRANCE CHANNEL 1975-1987 Year Volume Dredged Type Dredge Disposal Area (yd3) 1975 1,100,000 Hopper Gulf Disposal 1981 647,000 Hopper Gulf Disposal 1983 114,000 Hopper Gulf Disposal 1984 917,000 Hopper Gulf Disposal 1985 2,433,000 Pipeline Perdido Key 1987 200,000 Hopper Gulf Disposal (approx.) Sand Quality and Quantity As a first determinant of the amount of sand to be placed during the channel deepening phase, an effort was carried out to quantify the amount of good quality sand available which could feasibly be placed on Perdido Key. This would represent the upper limit of material to be recommended. Sand quality as used here is based on grain size and visual evidence, primarily color which is a good indicator of organic content. The bases for determination were the vibrocore data and quantities to be dredged. Figure 3 presents the overall layout of the channel and the locations of the vibrocores. The quality of material in each of the cores was defined by: (a) logs or general description from visual inspections of the cores, (b) size analyses at several depths along the cores, and (c) color photographs along the entire length of the cores. The latter proved to be invaluable. Prior to discussing available sand characteristics, it is relevant to note that, as shown in Figure 1, the entrance channel had been defined in three reaches, with the central reach, Reach 2, as that reach which could provide sand to Perdido Key. The boundary between Reach 1 and Reach 2 had been established earlier based on material quality, reportedly in discussions with the State of Florida. The boundary between Reach 2 and Reach 3 was based on economic considerations, i.e. seaward of this juncture it is considered to 13

PAGE 15

NAS PENSACOLA SF T O PICKEN3 S-" .. .. ..." S L A N O ORT 0 14 GO 14

PAGE 16

be less costly to transport sand seaward than to Perdido Key. Figure 4 presents an estimate of the volumetric distribution of sand dredging required as a function of position along the channel. Amount of Acceptable Material Available As described briefly previously, the amount of acceptable quality material expected to be available for placement on the beach was developed primarily through examination of vibrocore information at the 48 locations shown in Figure 3. As might be expected, it would always be helpful to have more information to define completely the distribution of acceptable material in the planned dredge area. However, it is believed that with the data presently available it is possible to identify sufficient quantities of good quality sand to meet the objectives of this study. In those limited areas where uncertainties remain, it will be necessary to maintain flexibility in the field operations with special monitoring during dredging. If the Corps/Navy is unwilling to maintain this flexibility and field vigilance, it will be recommended that these areas of uncertainty be deleted from further consideration. Figure 5 is an annotated version of Figure 4 and includes description of the quality of the material. Several areas can be grouped as presented below and summarized in Table III. Station 207+60N to Station 107+90N -The material characteristics within these stations are described by cores 1-19 and although there is some good material in this area, the locations of acceptable material are somewhat spotty and it is recommended that all of this material in this segment be regarded as unacceptable. It is noted that this length of undesirable material is greater than previously identified as Reach 1. Station 107+90N to Station 61+50N -The quality of material within this 4,640 ft segment is defined by Vibrocores 20 through 25. The material contained in these cores is uniformily good down to an elevation of -48 ft which is the greatest dredging depth considered in this segment. The amount of material expected to be dredged in this segment is 1,250,000 yd3 Core 26 -This vibrocore was taken on the westerly side of the navigational channel and is uniformily very poor. Referring to Figure 4, it 15

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Pensacola Naval Air Station .. 2400" >+GON St&207+60N 240 Sta125*60N Sa74 Reach 2 Reach 1 '' \ \Reach 1 T Pensacola Bay 0 Q Perddo Santa Rosa Island 0 Perdido Key Sta.41+50os N Reach 3 i 0 500 SSta. 19+50S I I aI I I 200 100 0 100 200 Station South Station North -Reach 3 --Reach 2 -Reach 1 Figure 4. Distribution of Required Total Dredging Pensacola Homeport. Includes Advance and Allowable Overdepth Dredging Quantities.

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Pensacola Naval Air Station .L 2400.:'Sta207+60N 24W Sta 125+60N Reach 2 Reach 1 Pensacola Bay 0 Z W U= Santa Rosa Island 0 Perdido Key st. 41+sos 3 All Acceptable S/Above Elevation: -41 ft Reach 3 O SUnacceptable 500 (Core 26) Sta. 196+50S Top SAcceptable Unacceptable Variable Acceptable ----Acceptable -Acceptable Quality 200 100 0 100 200 Station South Station North L -Reach 3 14 Reach 2 1 Reach 1 Figure 5. Distribution of Required Total Dredging Pensacola Homeport and Quality of Material. Includes Advance and Allowable Overdepth Dredging Quantities.

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TABLE III SUMMARY OF AVAILABLE MATERIAL QUALITY AND QUANTITY PENSACOLA BAY CHANNEL DEEPENING Stations Material Quality Volumes of Material Defined by Cores in Segment (yd3) Comments Comments From To From To Total Acceptable 207+60N 107+90N 1 19 4,540,000 0 All material unacceptable. Segment limits expand those previously defined for unacceptable material. 107+90N 61+50N 20 25 1,250,000 1,250,000 All material uniformily good. 26 26 330,000 0 All material unacceptable. Limits not well-established. 61+50N 23+60N 27 28 1,070,000 1,070,000 All material acceptable. 23+60N 7+60S 29 32 1,490,000 600,000 Only material above -41 ft elevation recommended for beach placement. 7+60S 41+50S 33 36 1,000,000 1,000,000 All material of good quality. 41+50S 92+50S 37 41 1,590,000 1,590,000 All acceptable. 92+50S 112+60S 42 43 470,000 260,000 Material above elevation -44 unacceptable, remainder acceptable. 44 44 270,000 270,000 All of good quality, but probably too localized for beach placement. 112+60S 196+50S 45 45 220,000 160,000 Top 2 ft of poor quality, rest acceptable. 46 46 220,000 220,000 Good quality. 47 47 70,000 0 All of poor quality. 48 48 negligible negligible Top 7 ft of acceptable quality, remainder unacceptable.

PAGE 20

is seen that this core corresponds to an area of maximum dredging. For purposes of estimation at this location, one-half of the material has been considered as characterized by Core 26 and one-half by Cores 25 A and B. This is an area where better definition would be desirable and it will be necessary to recognize that a portion of the material in this section of the channel will be acceptable and a portion will not be suitable for placement on the beach. With the definition allowed by the present cores, this determination must be made in the field. This will require special consideration and field care in this area; if it is not practical to retain this flexibility, it is recommended that the material in this segment be deleted from consideration for beach placement. Stations 61+50N through Station 23+60N -The material in this segment as defined by Vibrocores 27 through 28 is consistently good. It is estimated that 1,070,000 yd3 of material, all suitable for beach placement, will be yielded in this segment. Stations 23+60N through Station 7+60S -The material in this segment is described by Vibrocores 29 through 32. The material in the upper portions of each of these four cores is of good quality but that below elevations ranging from -41 ft to -45 ft is unacceptable. Two possibilities are present here. The first would be to place that material above the -41 ft horizon on the beach and to dispose of the additional material elsewhere. The alternative would be to place none of this material on the beach. It is estimated that 600,000 yd3 of good quality sand could be produced above the -41 ft horizon. Station 7+60S to 41+50S -Vibrocores 33 -36 define the material characteristics in this segment. All of this material is acceptable. The southerly limit of this segment was defined by the earlier established boundary between Reach 2 and Reach 3. It is recalled that this had been determined as the break-point south of which it would be more economical to dispose of the material at sea. The estimated quantity of good quality material in this segment is 1,000,000 yd3 Station 41+50S to Station 92+50S -The material characteristics in this segment are described by Vibrocores 37 -41 and are uniformily good down to the base channel elevation. It is estimated that 1,590,000 yd3 of high quality material are available in this segment. 19

PAGE 21

Station 92+50S to Station 112+60S -The material characteristics in this segment are defined by Vibrocores 42 and 43. There is a top layer of poor quality material underlain by good sand. The elevation of the interface ranges between -42 to -44 ft and for this situation, it would be feasible to remove the top layers, say down to -44 ft, with disposal offshore and place the underlying material on the beach. It is estimated that the volume of acceptable material is 260,000 yd3 Station 112+60S to Station 196+50S -The total quantity of material in this segment is relatively small (760,000 yd3) and is fairly irregular in quality. In particular, all of Core 44 is of good quality. The top 2 ft of Core 45 is of poor quality yet the remaining material is acceptable. Core 46 appears good, Core 45 is all of poor quality, Core 48 is of good quality for the top 7 ft and poor for the underlying layers and finally Core 48 appears uniformily bad. It is recommended that none of this material be placed on Perdido Key. Summary of Available Material Quality Table III presents a summary of material quality along the channel and Table IV provides additional summarized information. TABLE IV OVERALL SUMMARY OF MATERIAL QUANTITIES AND QUALITIES Description of Material Characteristics Total Volume (yd3) Total volume to be dredged 13,300,000 Total volume acceptable 6,420,000 Total volume acceptable within Reach 2 3,920,000 Total volume acceptable in Reach 2 without special care 3,320,000 Total volume acceptable if extend limits of Reach 2 to 92+50S 5,510,000 Total volume acceptable without special care if extend limits of Reach 2 to 92+50S 3,660,000 20

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HISTORICAL SHORELINE CHANGES This section reviews various sources of data from which one can infer historical rates of shoreline change. Florida Department of Natural Resources (1974-1984) The Division of Beaches and Shores of the Florida Department of Natural Resources maintains a monumented baseline along those 24 counties in Florida which have predominantly sandy shorelines. The monuments are at nominal spacings of 1,000 ft and provide an excellent base from which to conduct repetitive measurements of shoreline position. In Escambia County, complete sets of measurements have been conducted in 1974 and 1984. The results are presented for the eastern end of Perdido Key in terms of annual rates of shoreline changes in Figure 6. The monument locations along Perdido Key and Santa Rosa Island are presented in Figure 7. The results, which have been smoothed, show an average erosion rate on the order of 4 to 5 ft. per year decreasing toward the west. Near DNR monument 64, there is an area where accretion had occurred during the 10 year period. This area is located in the vicinity of Caucus Shoals and it is believed that this is an anomalous feature. Within the seven mile region shown in Figure 6, the loss in plan area is approximately 150,000 ft2/year, which using a conventional "rule for thumb" suggests an approximate volumetric loss of 150,000 cubic yards annually. Although not shown in Figure 6, the additional loss rate west of DNR monument 30 is at least 100,000 cubic yards per year. This is consistent with prevailing estimates of the net annual longshore sediment transport in this area at approximately 200,000 yd3/year toward the west. Beach Restoration, Summer 1985 In July, 1985, in conjunction with maintenance dredging, approximately 2.4 million cubic yards of generally good quality sand was placed along the eastern end of Perdido Key. Placement occurred over approximately 4,000 ft of shoreline length. At the time of placement, the eastern end of Perdido Key was in a fairly advanced state of erosion as a result of the impact of interruption of the natural littoral transport from the east by dredging of the navigational channel. Unfortunately, there has been no concerted effort to document the performance of this project; however, in conjunction with 21

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+5.0 Area of 1985 -Approximate Western Nourishment SI |Park Boundary SI -| I I Mile -U 0 > 30 40 50 60 FLORIDA DNR MONUMENT NUMBER Figure 6. Shoreline Change Rates for Escambia County, January 1974 to October 1984. Based on Florida DNR Surveys. Note Shoreline Change Rates Shown Have Been Smoothed by a Five Point Running Average. ) o 30 40 50 60 FLORIDA DNR MONUMENT NUMBER Figure 6. Shoreline Change Rates for Escambia County, January 1974 to October 1984. Based on Florida DNR Surveys. Note Shoreline Change Rates Shown Have Been Smoothed by a Five Point Running Average.

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2k SR 2988 ,-,i f 7 1PENSOLA NAVAL' .\ v/V AI R S TATION .-) | R50 I G Figure 7. Locations of DNR Monuments and Segment Nourished in 1985.

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their National Park Service responsibilities, investigators from Rutgers have conducted limited measurements, the analysis of which will be discussed in later paragraphs. Hurricane Elena occurred in September, 1985, shortly after completion of the project. Although the effects of this hurricane on Perdido Key were substantial, it is believed that the eastern end of Perdido Key would have suffered much more degradation if the restoration project had not been in place. Shoreline Changes -Information provided by Rutgers included shoreline position measurements at 33 locations of monuments maintained by the Florida Department of Natural Resources. These monuments are numbered 34 through 66 and are approximately 1,000 ft apart; see Figure 7. The 1985 restoration segment encompassed Monuments 61 through 64. Rutgers provided survey information for the following dates October 1984 April 1985 (Pre-nourishment)* September 1985 (Post-nourishment and post Hurricane Elena) May 1986 September 1986 February 1987 July 1987 (*Note: Nourishment occurred in July 1985) Prior to presenting the analysis of the Rutgers results, a brief presentation will be made of the expected behavior of an idealized beach restoration project on a long straight shoreline. Figure 8 presents as a bold line an idealized initial rectangular planform distribution of a nourishment project. For the idealized case of an infinitely long coastline, a simplified solution (summarized in Appendix II) is available for the evolution of this planform. An example of the solution is presented as the additional lines in Figure 8. It is seen that the sand spreads laterally, nourishing the adjacent beaches as a result of sand transported out of the nourished area. The rate at which this evolution occurs depends on the wave height raised to the 2.5 power, and inversely on the project length. As mentioned, actual project behavior deviates from the idealized results presented above; however, the idealized treatment provides a framework against which to evaluate actual 24

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0 Or o y(ft) MD8 o 0 z O C -7 ,4 0 ..."-"' / "':,, .: 20".,"-" 2 I r_..-_-_,_,_'-,__,,^____ _x -2.0 -1.0 0 1.0 2.0 ALONGSHORE DISTANCE (miles) Figure 8. Example of Evolution of Initially Rectangular Beach Planform on a Long Uninterrupted Shoreline.

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performance. Detailed results from the idealized solution will be used to evaluate the 1985 nourishment project. The Rutgers' tabulated results for shoreline position are presented as Table V. Prior to analyzing these data, several features are noted. The positions are presented for the NGVD (National Geodetic Vertical Datum) contour, which is approximately the mean sea level contour. All positions are relative to April, 1985. Although a separate column is not presented for the April survey, if it were, all entries would be zeros, since these are the reference values. It is evident, examining the September 1985 survey, that the nourishment took place over DNR monuments 61-64 a distance of approximately 4,000 ft. As a visual indication of the evolution of the beach fill over time, the average shoreline change over FDNR ranges 61-64 has been plotted in Figure 9. It is seen that the shoreline eroded an average of about 82 ft from October 1984 to April 1985, followed by an increase of approximately 525 ft due to the nourishment project. During the subsequent 1.8 years (September 1985 to July 1987), the shoreline within Ranges 61-64 eroded approximately 197 ft. An additional simple and informative result is obtained by establishing the percentage loss of sediment within the area placed. Considering sand to have been placed in the area represented by FDNR range monuments 61-64, the results presented in Table VI are obtained. Based on the results of Table VI, by July 1987 approximately 35% of the material present in September 1985 was transported out of the nourished segment. Using results from the idealized analysis described in Appendix II, an effective wave height of approximately 1.1 ft can be determined as a mobilizing agent for the placed sand. This effective wave height will be useful in later calculations of evolution of a nourishment project. Aerial Photography Aerial photography of the area was provided by the U.S. Army Corps of Engineers for the periods 1969, 1976, 1985 and 1986. In addition for purposes of this study, additional black and white and color photography was flown in October, 1987. The dates, scales and other information relevant to this photography are presented in Table VII. 26

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TABLE V SHORELINE CHANGE DATA FURNISHED BY RUTGERS (Distances in Meters) ngvd change Apr 85 (datum) DNR monument oct 84 sep 85 may 86 sep 86 feb 87 jul 87 34 8.390 -2.840 -19.320 -16.110 -1.660 -12.85 35 -8.800 4.130 -14.220 -10.160 -8.150 -12.61 36 -20.470 -10.850 -21.550 -18.750 -21.130 -22.73 37 -1.910 -9.400 -18.150 -22.550 -11.890 -19.11 38 -17.720 -7.030 -18.100 -20.72 39 -3.920 -10.470 -18.790 -3.910 -13.01 40 -0.340 0.300 -9.520 -7.350 -8.25 41 -6.300 -0.010 -14.780 -15.280 -10.030 -12.12 42 -20.650 -0.160 -14.950 -14.340 -23.460 3.61 43 -3.350 -2.530 -8.650 -3.120 -15.000 -8.31 44 -12.880 -1.690 -19.590 -19.200 -24.650 -7.43 45 -2.490 -3.270 -16.620 -14.140 -17.420 -3.87 46 47 -2.840 -5.660 -27.090 -13.320 -21.670 -3.17 48 -17.430 -9.390 -22.900 -9.870 -22.370 -7.42 49 -8.880 -8.030 -13.060 -12.000 -4.370 -1.81 50 -5.250 -9.310 -22.760 -27.280 -12.380 -14.2Q. 51 -0.650 17.720 -25.190 -21.030 -5.070 -11.71 52 -7.620 -20.260 -17.940 -22.620 -11.060 -31.38 53 7.540 -8.070 -21.540 -23.130 10.850 -11.06 54 9.080 -3.200 -19.890 -10.750 7.160 -8.91 55 19.790 -8.000 -15.480 -13.860 -4.280 -5.8 56 5.860 -5.520 -12.880 -9.910 --1.410 -3.07 57 4.880 -21.470 -25.590 -9.130 -8.95 58 13.760 -19.150 -5.890 0.960 -8.580 3.51 59 11.650 18.240 33.420 18.700 28.32 60 -2.480 53.260 40.680 68.000 45.780 54.71 61 16.660 117.560 101.080 132.970 97.300 97.36 62 25.690 169.810 131.900 143.430 107.770 114.70 63 33.020 186.070 148.530 146.980 107.090 113.37 64 30.220 175.740 129.620 121.080 119.640 94.09 65 -9.990 -0.580 -1.080 2.750 -12.56 66 15.620 -9.910 20.140

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Hurricane S o600Elena 0 Soo 2 500 El to jr 300 cc 2 ro 200 MAMJASO FMASOND FMAMJAS DJ 00 UJ 0 100r 100 5 200 J F YMA MJ J A S O ND J FMA MJ J A SOND J FM AMJ J AS ONDJ FMA MJ J AS 1984---1985 --1986--1987Figure 9. Average Shoreline Changes Over DNR Ranges 61-64 Encompassing Shoreline Segment of 1985 Nourishment.

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TABLE VI PLAN AREA CHANGES ASSOCIATED WITH 1985 NOURISHMENT Dates Plan Area Changes (ft2) April 1985 to September 1985 + 2,128,400 ft2 September 1985 to July 1987 -753,400 ft2 TABLE VII CHARACTERISTICS OF AERIAL PHOTOGRAPHY USED IN THIS REPORT Photography Date Scale Type Comments April 1969 1:12000 Black and White Eastern 8,000 ft of Island Not Covered March 1977 1:24000 Color All of Park System Covered September 1985 1:12000 Black and White All of Park System Covered March 1986 1:12000 Color All of Park System Covered October 1987 1:24000 Black and White All of Park System Covered October 1987 1:12000 Color All of Park System Covered 29

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The aerial photographs were digitized, adjusted to a common scale, plotted and are presented in Figure 10. The correct alignment of the photographs is critical to an accurate determination of shoreline changes and for this purpose a road intersection was used on the western end of the region of interest and an identifiable feature on Fort McRee was used on the eastern end. As noted in Table VI, the 1969 photography did not include the eastern 8,000 ft of the island. This has resulted in less confidence in the photography alignment, with these uncertanties greatest toward the east. Additionally, the generally small scale of all but the 1987 aerial photography results in relatively low confidence in quantitative shoreline changes. The aerial photographs were analyzed to determine the shoreline changes in the vicinity of the 1985 beach nourishment. These results are presented in Figure 11 for the time intervals 1977 to 1985 and 1985 to 1987. The first time period includes the 1985 nourishment and Hurricane Elena. It is seen that the ambient erosion over the 1977 to 1985 period (8.5 years) is on the order of 150-200 ft., part of which may be attributed to the erosional trend in this area and part due to the impact of Hurricane Elena. The nourishment has spread out beyond the limits where it was placed and also more than compensates for the erosion in the placement area. During the 1985 to 1987 interval, erosion has occurred in the nourished area and the adjacent shoreline has been relatively stable. This time interval (2.1 years) is too short to develop quantitative results; however, it is clear that a portion of the nourished area has eroded and appears to be of benefit to the adjacent shorelines. In summary, the results of the aerial photography analysis are in qualitative agreement with the more reliable survey data of Florida DNR and Rutgers. SEDIMENT ANALYSIS During the field visit, 32 sediment samples were taken both within and outside of the 1985 nourished area. These samples generally extended across the beach profile and included material from the dune, berm, beach face and offshore bar. These samples were subsequently analyzed by Thompson Engineering Testing, Inc. (Job #1666-A87670, Report No. 1) for size distribution and calcium content. It had been reported that the calcium carbonate (shell) content of the nourishment material was significantly higher 30

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Escambia County, Perdido Key Sacle: 1"=4000ft. .II I I I I I I I I I I I I I I I I I I I I I I I II I I I I I I I 7 1969/04 Photos -1977/03 Photos + = Locations of Florida DNR Monuments 1985/09 Photos 1986/03 Photos FLORIDA DNR MONUMENT NUMBER 1987/10 Photos Figr 1 0. L tion and Caraeristics of R endd B h Nurisent. Figure 10. Location and Characteristics of Recommended Beach Nourishment.

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+500 West Approximate Limits 1985 NourlshmentI SMarch 1977 to Sept. 1985 S(Includes 1985 Nourishment W and Hurricane Elena) Z Sept. 1985 to October 1987 o 0 500 I I I I I I -500 -I --I --I --I --I --I --I -55 60 65 DNR RANGE MONUMENT NUMBER Figure 11. Shoreline Changes in Vicinity of 1985 Beach Nourishment. Based on Analysis ot Aerial Photographs.

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than the native material and therefore quantification of this parameter was of interest. The locations of the samples and the median size and calcium carbonate content are presented in Table VIII. Column 4 indicates whether or not the sample was located in the 1985 nourishment area. The samples RX-1,2,3 were located adjacent to the Park Headquarters. In order to determine whether or not the nourished material was significantly different than the native properties (median diameter and calcium carbonate), these properties were averaged for common positions across the beach profile for areas within and outside of the 1985 nourishment limits. These results are presented in Table IX. Prior to discussing the averages, it should be noted that there is significant variability in some of the individual parameters, especially the calcium carbonate content. Returning to Table IX, the only significant differences in diameter are for "Near the Dune Line". Presumably the reason is that outside the fill area, these sediments have been transported by wind; as a result only the smaller grains have been transported to and deposited in this area. The similar grain sizes on the beach face could be the result of the relatively high transport activity in this region. Although the diameters "midway across the berm" within the fill limits are slightly coarser than outside, it is somewhat surprising that these differences are not greater. The diameters at the five foot depth, usually on the bar, are essentially the same inside and outside of the fill limits. This is due to offshore transport of the finer material, leaving the coarser material on the more energetic beach face. With the exception of the beach face and five foot depth, the average calcium content is substantially higher within the fill limits. This is consistent with (1) the active transport on the beach face, and (2) the selective transport of the finer materials offshore and the tendency for the shells to be coarser than the sand. In summary, although the sediment properties did exhibit some differences within and outside of the fill limits, they are not so large as to be regarded negatively. Moreover, with the beach system exposed to a wider range of storm and normal wave processes, it is anticipated that any noticeable differences will tend to diminish with time. 33

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TABLE VIII SUMMARY OF SEDIMENT SIZE AND CALCIUM CARBONATE CHARACTERISTICS Sample Percent Median In 1985 Comments Designation Calcium Size, D50 Nourishment Carbonate (mm) Area? R61-1 2.2 0.49 Yes Near Old Dune Line R61-2 2.8 0.38 Yes Midway on Fill to Water R61-3 4.5 0.51 Yes Beachface R61-4 < 0.2 0.31 Yes Bar Crest, Approx. 5 ft Depth R62.5-1 0.3 0.49 Yes Near Old Dune Line R62.5-2 0.5 0.41 Yes Midway on Fill to Water R62.5-3 5.2 0.50 Yes Beachface R62.5-4 0.4 0.31 Yes Bar Crest, Approx. 5 ft Depth R64-1 0.2 0.33 Yes Near Old Dune Line R64-2 0.2 0.33 Yes Midway on Fill to Water R64-3 3.9 0.54 Yes Beachface R64-4 0.2 0.32 Yes Bar, Approx. 5 ft Depth R64-5 < 0.2 0.30 Yes Natural Dune R67-1 < 0.2 0.33 No Near Dune Line R67-2 < 0.2 0.37 No Midway from Dune to Water R67-3 1.0 0.33 No Beachface R67-4 < 0.2 0.37 No Approx. 5 ft Depth, No Bar R65-1 < 0.2 0.30 No Near Dune LIne R65-2 < 0.2 0.31 No Midway from Dune to Water R65-3 5.4 0.35 No Beachface R65-4 < 0.2 0.25 No Approx. 5 ft Depth, No Bar R57-1 < 0.2 0.36 No Near Dune Line R57-2 < 0.2 0.37 No Midway from Dune to Water R57-3 3.3 0.45 No Beachface R57-4 0.2 0.30 No Outer Bar Crest, Approx. 5 ft Depth R55-1 < 0.2 0.36 No Near Dune Line R55-2 < 0.2 0.32 No Midway from Dune to Water R55-3 4.2 0.50 No Beachface R55-4 0.2 0.30 No Outer Bar Crest, Approx. 5 ft Depth RX-1 0.2 0.37 No Beach, No Dune RX-2 1.9 0.45 No Beachface RX-3 0.4 0.29 No Outer Bar Crest, Approx. 5 ft Depth 34

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TABLE IX CHARACTERISTICS OF SEDIMENT SAMPLES INSIDE AND OUTSIDE OF 1985 NOURISHMENT LIMITS Beach Profile Median Diameter (mm) Calcium Carbonate Percentage Feature Inside Fill Limits Outside Inside Fill Limits Outside Near Dune Line 0.44 0.34 0.9 < 0.2 Midway Across Berm 0.37 0.35 1.17 < 0.2 Beach Face 0.44 0.42 3.3 3.2 Bar Crest or Five Foot Water Depth if Bar Not Present 0.31 0.30 0.3 0.2 RECOMMENDED INITIAL PROJECT CHARACTERISTICS AND EVOLUTION OF THE PLANFORM Initial Planform The most relevant parameters of the initial planform are the length, £, the width, w, and the transition characteristics at the end of the project. Using accepted procedures, the additional width, w, for various lengths and nourishment quantities are presented in Table X. To provide a basis for comparison, the average shoreline advancement associated with the 1985 nourishment was approximately 525 ft. TABLE X INITIAL PLANFORM CHARACTERISTICS Project Additional Beach Volume Placed Length Width (yd3) (miles) (ft) 4 95 ft 2,000,000 6 60 ft 4 180 ft 4,000,000 6 120 ft 4 285 ft 6,000,000 6 180 ft 5,000,000 4.5 270 ft* (with tapered ends) *Recommended Plan 35

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Planform Evolution Considering the nourishment to occur over a beach segment encompassed by FDNR Ranges 40 through 64 (4.5 miles), the recommended planform is presented in Figure 12 and the anticipated evolution is presented in Figure 13. Figure 13a presents the planform at 2, 5 and 10 years for an otherwise stable shoreline and Figure 13b presents the planform at the same time periods for the more realistic case of a shoreline eroding at 5 ft. per year. In Figure 13, the shoreline has been drawn straight for convenience rather than curved. Also, the jetty at the northeastern end of Perdido Key (near DNR monument 67 is included). Beach Profile The planform characteristics presented in the preceding section and in Table X have been based on the consideration that one cubic yard of sand along one foot of beach length will cause a shoreline advancement of one foot. Thus, this one cubic yard (27 cubic feet) is distributed such that it causes a uniform profile advancement of one foot over a vertical portion of the profile of 27 ft. The placement options include placing the material to a shallower depth which means that the shoreline advancement must be greater. With this placement strategy, the waves will ultimately redistribute the sand to greater depths to yield the one foot shoreline advancement per cubic yard of sand per unit length of beach. Figure 14 shows these two options and the recommended profile shoreward of the equilibrated position of the initial shoreline. The purpose of the lower berm (4 to 5 ft.) compared to the natural berm height (approximately 6 ft.) is to allow the wind and water processes to exert their respective shaping processes, thereby yielding a more natural profile. BIOLOGICAL CONSIDERATIONS No specific studies have been conducted to determine the effect of the 1985 beach nourishment on the biology of Perdido Key. However, monitoring studies have been conducted of other projects and these results allow the probable impact to be inferred. The information below is drawn primarily from an excellent review by Nelson (1985) of the effects of beach nourishment on the nearshore biota. The primary focus will be on three common nearshore organisms: (1) Emerita talpoida (mole crabs), (2) Donax (coquina clams), and (3) Ocypode (ghost crabs). 36

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0 5 Scale(miles) Recommended Nourishment in Connection with Channel Dredging Project Volume: 5 Million Cu. Yds. Characterists f Length: 4.5 Miles Additional Beach Width: 270 Ft. Figure 12. Location and Characteristics of Recommended Beach Nourishment.

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0 1 2 I I I West Scale (miles) Initial C -1 Year S300 -5 Years U -..10 Years 040 50 60 Jetty DNR MONUMENT NUMBER a) Calculated Evolution of Recommended Nourishment If Shoreline Were Stable. ee West , ..In itia l 1I Year 300 -5 Years S--10 Years S40 50 60 Jetty DNR MONUMENT NUMBER b) Calculated Evolution of Recommended Nourishment on a Shoreline Eroding at a Rate of Five Feet Per Year. § Figure 13. Calculated Evolution of Recommended Nourishment Planform for Stable and Eroding Beaches.

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20 O 10 Natural Berm Elevation -6 ft +5ft +4ft (. +4ft z U 280oftO m0 0 O Recommended SNourishment Profile > -10 DNR Profile w Measured October 31,1984 -20 I I I I I I I 0 300 600 900 1200 1500 1800 DISTANCE GULFWARD FROM DNR MONUMENT R-48 (ft) Figure 14. Recommended Characteristics of Nourished Profile. Illustrated for DNR Monument No. 48

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Emerita Talpoida (Mole Crabs) This organism is a filter feeder that burrows in the lower foreshore of the beach and can be very abundant, although the densities tend to be very irregular. The highly energetic swash zone appears to be the preferred environment for E. Talpoida probably enhancing the food supply. Densities in excess of 3,700 animals per square meter have been reported (Bowman, 1981). The animals tend to be in greatest abundancies in Florida in December to January. E. Talpoida are very mobile and apparently have the capability to avoid being buried by beach nourishing by leaving an area. In a project in which 956,000 m3 sand was placed on the Cape Hatteras beach, Hayden and Dolan (1974) found no dead animals and they concluded that the affected areas recovered in less than two weeks. The sand used in this nourishment project was quite comparable to the native sand. A second project of similar quantity (904,000 m3) at Fort Macon, N.C., was monitored by Reilly and Bellis (1978, 1983); however the sand was taken from dredged harbor sediments and was not compatible in size characteristics. Additionally the sediment was from a reducing enviornment. The monitoring indicated that the E. Talpoida populations were nonexistent in the project area during material placement but recolonized rapidly several months later during the spring recruitment period. A delay of one month during the recruitment period was evident. The summer after the commencement of nourishment (the preceding December), the animal densities were the same on the nourished and control beaches. However, there were significant differences in the size classes with the nourishment containing exclusively juveniles. The investigators concluded that the adult mole crabs in the vicinity of the nourished site were killed by turbidity and that the juvenile animals had populated the area from the adjacent beaches. Nelson (1985) has suggested that the liberated hydrogen sulfide in the nourished sediments may also have contributed to the mortality of adult animals. In summary of the impact of beach nourishment on E. Talpoida, it is concluded that these animals are very mobile and are able to vacate an area unsuitable for their physiology. Moreover, with the return of favorable conditions, they rapidly recolonize the area. If the material placed is compatible with that originally on the beach, effects are of quite short 40

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duration. If poor quality sediment is used, recovery is slower, but still relatively rapid, probably due to the high motility of these animals and the longshore currents on the beachface. Donax (Coquina Clams) This genus of bivalves has two species that have been reported to be found in the Florida panhandle area. The documented range of Donax Variabilis is from Virginia Beach, VA to Mississippi. Also Donax Texasianus has been found in the Florida panhandle. Most Donax Variabilis migrate up and down the beach with the tide, presumably to be in the active swash zone where the high velocities ensure ample quantities of moving water from which these filter feeders obtain nourishment. However some studies have reported populations that do not migrate with the tide. The life of Donax is generally 2-3 years with one or two spawning periods per year. Primary spawning occurs in February and in Florida a second spawning may occur in June. The peak seasonal abundance tends to occur in June and July. Maximum densities of Donax Texasianus in Panama City, Florida was 2,050 animals/m2 Few studies are available documenting the effects of beach nourishment on Donax. Reilly and Bellis (1978, 1983), reporting on the effects of nourishment on a North Carolina Beach found that following a December nourishment event, Donax were not found in the nourished area until the following July. These were young believed to be transported in by the longshore currents and it was suggested that the adults were killed by burial in the offshore area. Ocypode Quadrata (Ghost Crab) These animals burrow in the dry beach although they do lay their eggs in the water. The older crabs tend to burrow higher on the beach than the young animals. Their diet varies from dead plant and animal material to live Donax and Emerita. Although seen frequently during the daytime, they are primarily nocturnal. Only the studies of Reilly and Bellis (1978, 1983) have evaluated the effects of beach nourishment on ghost crab populations. Their limited data 41

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indicated that the summer following nourishment, there was a 50% lower population. Their interpretation was that, since the material was placed below a level that would cause direct burial and since the crabs could probably burrow up through placed sand, it is likely that the reduced population was a result of emigration of the crabs due to a reduced food supply. Panama City Studies Saloman (1976), Culter and Mahadevan (1982) and Saloman, et.al. (1982) have reported on extensive biological studies in conjunction with the 1976 nourishment of some 300,000 cubic meters along the beaches of Panama City. Saloman (1976) conducted a pre-nourishment baseline study in 1974-1975 and documented the effects of Hurricane Eloise (September, 1975) on the biota. It was found that there was no decline in the abundance of intertidal animals following the hurricane. Culter and Mahadevan (1982) conducted studies in 1979-1980 to examine long-term effects of the 1976 nourishment. They concluded "No long-term adverse environmental effects as a result of beach nourishment could be detected within the nearshore zone of the Panama City beaches. There were also no adverse or stressful conditions present at the borrow sites." Saloman, et.al. (1982) carried out a study analyzing data collected between April 1976 and November 1977. The purpose of the study was to examine short-term effects of offshore dredging on the benthic community. It was concluded that there was an immediate decline in the benthic community; however, the populations rapidly recovered and were virtually at preconstruction levels within one year. It was noted that the borrow pits were relatively small and no more than 5 m of sand (vertically) was removed from each pit. The pits were located in water depths of 6 to 9 m. Initially the pits filled with material finer than on the adjacent bottom; however, these differences tended to diminish with further filling. 42

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Summary Regarding Biological Effects of Beach Nourishment Based on a comprehensive review of published information, Nelson (1985) has concluded that the intertidal beach organisms are well adapted to this high energy environment including times of significant erosion and accretion and fluctuations in turbidity. During and immediately following storms, massive erosion and deposition occur over segments of beaches long in comparison to nourishment projects. Thus any adverse effects of beach nourishment carried out with compatible sand tend to be short-lived as the animals can either survive the event or are adapted to rapid lateral recolonization. Nelson notes that although the available evidence indicates minimal and short-lived biological effects, the present level of understanding is such that biological monitoring programs are necessary to further document the quantitative impacts of beach nourishment projects. RECOMMENDATIONS The following recommendations are made based on the results of this study. In conjunction with the construction dredging of the Kitty Hawk channel, it is recommended that up to a total of 5,000,000 cubic yards of material be placed along a 4.5 mile segment along the eastern end of Perdido Key as presented in Figure 12. Based on historical erosion data, implementation of this recommendation would still fall short of restoring the shoreline to the condition that would prevail if channel deepening projects had not interfered with the natural processes. Based on Florida Department of Natural Resources shoreline change data, this nourishment project would reinstate the shoreline to its approximate condition some 20 years ago. Moreover, this project should fill in and "arrest" to some extent the shoreline erosional wave which is now moving to the west. Soon after placement of the material, it is recommended that sea oats and possibly other natural vegetation be planted to enhance dune formation and early return to a more natural condition. It is recommended that the above project be monitored to determine the physical evolution and biological effects. A preliminary description of a monitoring program to document the physical effects is presented in Appendix I; it is recommended that the monitoring program continue for at least five years. 43

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If the project performs as expected with erosion of material in the region placed and transport to and deposition in the beach segments adjacent to the placement area, it is recommended that during future channel maintenance, all beach quality sand up to 300,000 yd3/year be placed on the beach. The most appropriate placement locations will be established as a result of the monitoring efforts. REFERENCES Bowman, M.L. (1981) "The Relationship of Emerita Talpoida to Beach Characteristics," M.S. Thesis, University of Virginia, Charlottesville, Virginia, 106 pp. Culter, J.K. and Mahadevan, S. (1982) "Long-Term Effects of Beach Nourishment on the Benthic Fauna of Panama City Beach, Florida," Miscellaneous Report No. 82-2, U.S. Army Corps of Engineers, Coastal Engineering Research Center, Fort Belvoir, VA. Dean, R.G. (1983) "Principles of Beach Nourishment," in Handbook of Coastal Processes and Erosion, CRC Press, p. 217-231. Hayden, B. and Dolan, R. (1974) "Impact of Beach Nourishment on Distribution of Emerita Talpoida, the Common Mole Crab," Journal Waterways, Harbors and Coastal Engineering Division, ASCE, Vol. 100, WW2, p. 123-132. Nelson, W.G. (1985) "Guideline for Beach Restoration, Part I: Biological Guidelines," Report No. 76, Florida Sea Grant College. Rutgers University (Undated) "Measurements of Shoreline Positions Along Perdido Key, 1985-1987". Reilly, F.J. and Bellis, V.J. (1978) "A Study of the Ecological Impact of Beach Nourishment with Dredged Materials on the Intertidal Zone," Institute for Coastal and Marine Resources, East Carolina University, Technical Report No. 4. Reilly, F.J. and Bellis, V.J. (1983) "The Ecological Impact of Beach Nourishment with Dredged Materials on the Intertidal Zone at Bogue Banks, North Carolina," U.S. Army Corps of Engineers, Coastal Engineering Research Center, Miscellaneous Report No. 83-3. Saloman, C.H. (1976) "The Benthic Fauna and Sediments of the Nearshore Zone Off Panama City, Florida," Miscellaneous Report No. 76-10, U.S. Army Corps of Engineers, Coastal Engineering Research Center, Fort Belvoir, VA. 44

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Saloman, C.H., Naughton, S.P. and Taylor, J.L. (1982) "Benthic Community Response to Dredging Borrow Pits, Panama City Beach, Florida," Miscellaneous Report No. 82-3, U.S. Army Corps of Engineers, Coastal Engineering Research Center, Fort Belvoir, VA. Thompson Engineering Testing, Inc. (1987) "Grain Size Distribution and Calcium Carbonate Analyses of Sediment Samples," Contract N62467-85-C-0593, Amendment/Modification No. P00009, Mobile, Alabama. 45

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APPENDIX I PRELIMINARY MONITORING PROGRAM TO QUANTIFY PHYSICAL EFFECTS OF BEACH NOURISHMENT ON PERDIDO KEY INTRODUCTION The purpose of the monitoring program described below is to establish the physical effects of beach nourishment on Perdido Key. The results of this program will serve to quantify the performance of the nourishment project and to establish optimum quantities and location of material placement in future maintenance programs. The results will be used also to evaluate/improve methods of predicting performance of such projects, an objective of importance to both the Corps of Engineers and the National Park Service. Finally, of special importance will be the evolution of the upper portions of the beach profile (presented in Figure 14) toward more natural vegetation, profile and grain size characteristics than would occur otherwise. The biological monitoring plan will be developed and submitted separately. MONITORING PROGRAM ORGANIZATION In accordance with the objectives of the monitoring to be able to document and predict the performance of the nourishment project, the program is organized into Past, Present and Future components. Past This component comprises a historical study to document the changes that have occurred to Perdido Key and the modifications of the large scale "forces", predominantly dredging at the Pensacola Channel and the occurrence of major storms. The effects of recent storms (Camille, 1969; Frederic, 1979; Elena, 1985) have been documented rather well and will serve to assist in quantifying shoreline effects that should be associated with earlier major storms for which the shoreline effects have not been documented. Present This component would concentrate on documenting pre-nourishment conditions and the effects of the nourishment project. 46

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Future Results from the Past and Present programs will be combined to predict evolution of the nourishment project farther into the future. Also the monitoring results will serve as a basis for evaluating and refining present prediction calculation methodology. The revised methodology will be used to evaluate various scenarios for maintenance material placement and through this process, recommendations developed. PROGRAM DURATION AND ELEMENTS The recommended duration of the recommended monitoring program is five years with one complete set of measurements carried out prior to commencement of the nourishment project. The recommended monitoring elements are (1) Beach and Offshore Profiles -All profiles would be carried out at DNR monument locations. Profiles would be taken at a total of 31 monuments with: 5 Profiles, Monuments 27-35, Alternate Monuments 10 Profiles, Monuments 36-45, Every Monument 6 Profiles, Monuments 47-57, Alternate Monuments 10 Profiles, Monuments 58-67, Every Monument These profiles would be taken twice yearly (spring and fall) and after major storms, extending offshore 1,000 m or to the 8 m contour on the Gulf side, across the island to wading depth on the bay side. The bayside profiles need only be conducted during the first survey period and after storms which affect the dunes and cause washover deposits. The locations of the profiles are presented in Figure I-1. 2. Sand Sample Collection -Samples will be collected in conjunction with the profiling described above. The samples shall be taken at representative positions of the profile including: dune, berm, beach face, depths of 1 m, 2 m, 5 m, 8 m, 10 m on the Gulf side and at the shoreline and at 1 m and 2 m on the bay side. Samples will be taken with each set of profiles. 47

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0 1 2 / I I I i I Scale(miles) R-30 R-35 R-40 R-4 R-50 R-55 I I I Ri R'6650 I I I • ! I I I 1 I .I I I I I I I I 1 "I' 1 Approximate Possible Location of Recommended Beach Westerly Park Directional Wave Gage Nourishment Boundary NOTE: R-40 is Florida Department of Natural Resources Monumented "Range 40" Figure I-1. Recommended 31 Profile Locations and Location of Directional Wave Gage

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3. Aerial Photographs -Black and white and color photography shall be taken in conjunction with the fall profiling and provided at scales of 1:12,000 (Color) and 1:2400 (Black and White). 4. Directional Wave Gage -It is recommended that a directional wave gage be located in a water depth of approximately 10 m, see Figure I-1. 5. Weather Station -A weather station should be installed. The primary components of the station are: rain gage, recording anemometer (wind speed and direction) and recording barometric pressure. 6. Ground Photographs -Approximately 40 locations of special interest relative to vegetation growth or shoreline change will be identified initially and will be photographed on a bimonthly basis. PROJECT COST It is envisioned that the physical component of the monitoring program as described herein would cost approximately $200,000 per year for a total of $1,000,000. It is planned that where advantageous to understanding and interpretation, the biological and physical field collection components will be coordinated. 49

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APPENDIX II GOVERNING EQUATIONS FOR BEACH PLANFORM EVOLUTION It can be shown that beach profile evolution along a straight shoreline is approximately in accord with the following linear partial differential equation: -y = B -92 (II-1) at x2 ax in which y is the shore-perpendicular distance from a baseline to a particular contour (which in this case will be mean sea level), x is the alongshore distance, t is time and B is an "activity" coefficient related to breaking or shallow water conditions as: Breaking Wave K Hb 5/2gK cos(B-ab Conditions: B = -(11-2) Conditions: B =-8 (S -1) (1 -p) (h + G) (II-2) 2 Deep Water KH gT cos(B -a ) Conditions: B = 32w (S1) (1 -p) (h+ G) (1-3) in which K is a sediment transport coefficient, usually taken as 0.77, H and T represent the wave height and period, respectively, g is the gravitational constant, K is the spilling breaker constant (= 0.8), S is the ratio of sediment density to water density, p is the porosity, (h* + G) is the vertical dimension of the portion of the profile partipating in the profile response, a is the azimuth of the outward shore normal, a is the azimuth of the direction from which the waves originate and the subscripts "o" and "b" denote conditions at deepwater and breaking, respectively. Considering a nourishment project of uniform width, w, over a length, L, forming a rectangular planform, it can be shown that the solution to Eq. (II-1) is w L 2x L 2x y(x,t) = -{erf[--( + )] -erf[-(---]}11-4) 2 4/B L 4/BiF in which "erf" is a mathematical function called the "error function". 50

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The fraction, F, of the fill removed from the region placed due to longshore sediment transport can be shown to be approximated for early time, t, by F = (11-5) rw L in which t is the time during which the fill is lost. Considering that 35% of the fill was transported out of the area placed in a period of 10 months (September, 1985 to July, 1987, Table VI), an effective breaking wave height, Hb, can be determined as 2 F B = --F 4t ST (4000)2(.35)2 2 4 (685 x 24 x 3600) 0026 ft and, from Eq. (1-2) 0.4 8B(S -1)(1 -p) (h,+ G) 4 Hb [ "1 KbK/g/ cos(B -ab) 0.4 H = [8(.026)(1.65)(.65)(27)] = 1.1 ft 0.77 r32.2/0.78 1 in which the approximation cos(B -ab) = 1.0 has been made. 51


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