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Manatee County Beach Nourishment Project performance and erosional hot spot analyses

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Manatee County Beach Nourishment Project performance and erosional hot spot analyses
Series Title:
Manatee County Beach Nourishment Project performance and erosional hot spot analyses
Creator:
Wang, Zhanxian
Place of Publication:
Gainesville, Fla.
Publisher:
Coastal & Oceanographic Engineering Dept. of Civil & Coastal Engineering, University of Florida
Language:
English

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University of Florida
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IUFL/COEL-2001/003
MANATEE COUNTY BEACH NOURISHMENT PROJECT
PERFORMANCE AND EROSIONAL HOT SPOT ANALYSES
I by
I Zhanxian Wang
and
*Robert G. Dean
*January 26, 2001
Prepared for:
I Office of Beaches and Coastal Systems
Department of Environmental Protection I Tallahassee, Florida 32399
I Coastal & Oceanographic Engineering Program
Department of Civil & Coastal Engineering
I433 Weil Hall *P.O. Box 116590 Gainesville, Florida 32611-6590 LJWRSIT OF I FLORIDA




UFL/COEL-2001/003

MANATEE COUNTY BEACH NOURISHMENT PROJECT PERFORMANCE AND EROSIONAL HOT SPOT ANALYSES
by
Zhanxian Wang and
Robert G. Dean

January 26, 2001
Prepared for: Office of Beaches and Coastal Systems Department of Environmental Protection Tallahassee, Florida 32399




MANATEE COUNTY BEACH NOURISHMENT PROJECT PERFORMANCE
AND EROSIONAL HOT SPOT ANALYSES
December 26,2001
Prepared for:
Office of Beaches and Coastal Systems
Department of Environmental Protection Tallahassee, FL 32399
Submitted by:
Zhanxian Wang and Robert G. Dean
Department of Civil and Coastal Engineering University of Florida Gainesville, FL 32611




Table of Contents
List of Figure ............................................................................................... ii
List of Tables .............................................................................................. iv
1. Introduction ............................................................................................... I
1. 1 General D escription ............................................................................ 1
1.2 Anna M aria Key Shore Protection Pro ect ........................................... 3
1.3 Purpose of This Study ......................................................................... 4
2. D escription of Project Area ....................................................................... 5
2.1 General ................................................................................................ 5
2.2 Sedim ent Characteristics ..................................................................... 8
2.3 D ata Sources ..................................................................................... 10
2.4 Beach Profiles ............................................................................ I ...... 11
2.5 Initial Placem ent ............................................................................... 12
2.6 Shoreline Changes ............................................................................. 14
2.7 Volum e Changes ............................................................................... 16
3. Project Perform ance Prediction .............................................................. 19
3.1 Predicted Beach Planform Evolution ................................................. 19
3.2 Comparison between Measured and Predicted Changes ..................... 20
4. Identification and Probable Cause(s) of Erosional Hot Spot(s) ................ 30
4.1 Erosional H ot Spot Identification ....................................................... 30
4.2 Analysis of Possible Cause(s) of H ot Spot(s) ..................................... 32
5. Summ ary and Conclusions ..................................................................... 36
6. References ............................................................................................. 37
Appendix A Beach Profile Survey D ata .................................................... 39
Appendix B. Shoreline Change Rates on Anna Maria Key ........................ 56




Figure Page
1.1 M anatee County Location ...................................................................... 3
2.1 Anna Maria Key in Manatee County ....................................................... 6
2.2 Grain Size Distribution for Native and Borrow Area Sediments with
and w ithout Carbonates .......................................................................... 9
2.3 Comparison of Average Profiles for Monuments R-20 to R-27 for
Four Surveys ........................................................................................ 11
2.4 Initial Shoreline Position Based on Shoreline Changes between
Pre-built and A s-built ........................................................................... 13
2.5 Initial Volume Placement Based on Profile Changes between
Pre-built and A s-built ............................................................................ 13
2.6 Shoreline Changes for Different Periods Relative to As-built .............. 14
2.7 Volume Changes foe Different Periods Relative to As-built ................ 16
2.8 Proportion of Total Volume and plan Area Remaining in Placement
Area (R-12-R-35) Relative to As-built ................................................. 17
3.1 Comparison of Predicted and Measured Shoreline Advancement
and Volume Remaining from Pre-built to 08/1993 ............................... 21
3.2 Comparison of Predicted and Measured Shoreline Advancement
and Volume Remaining from Pre-built to 02/1994 ................................ 22
3.3 Comparison of Predicted and Measured Shoreline Advancement
and Volume Remaining from Pre-built to 02/1995 ................................ 23
3.4 Comparison of Predicted and Measured Shoreline Advancement
and Volume Remaining from Pre-built to 07/1997 ................................ 24

List of Figures




Page

3.5 Comparison of Predicted and Measured Shoreline Advancement
and Volume Remaining from Pre-built to 03/1998 ................................ 25
3.6 Comparison of Predicted and Measured Shoreline Advancement
and Volume Remaining from Pre-built to 02/1999 ................................ 26
3.7 Comparison of Predicted and Measured Plan Area and Volume
Remaining in the Project Area ............................................................. 29
4.1 Hot Spots Identification Based on Shoreline Advancement ................... 31
4.2 Hot Spots Identification Based on Volume Remaining .......................... 31
4.3 Pre- and Post-Nourishment Profiles at Monument R-25 ........................ 33

Figure




Table Page
1. 1 Possible Causes of Erosional Hot Spots .................................................. 2
2.1 List of Survey Data Used in this Report ................................................ 10
2.2 Total Plan Area and Volume Remaining at Different Surveys in
Project Area (R-12 to R-35) ................................................................. 17
3.1 Deviation of the Shoreline and Volume Changes .................................. 27
3.2 The Measured and Predicted Average Beach Widths and Volume
Densities within Project Limits ............................................................. 28

List of Tables




PERFORMANCE OF TILE ANNA MARIA KEY
BEACH NOURISHMENT PROJECT:
AN ASSESSMENT OF EROSIONAL HOT SPOTS
1. INTRODUCTION
1. 1 General Description
Beach nourishment, one of the most effective approaches to counter coastal erosion, consists of the placement of large quantities of good quality sand in the nearshore system in order to create or restore a beach system. One of the benefits of this soft approach is by supplying additional sand, the project benefits adjacent beaches as contrasted to structures which can adversely affect adjacent beaches. One of the most perplexing and expensive aspects of the beach nourishment solution can be the occurrence of erosional hot spots (EHSs) within the limits of the project. An erosional hot spot is defined as a limited area that erodes more rapidly and/or equilibrates with a significantly narrower beach width compared to the adjacent beaches. EHSs can contribute substantially to the overall cost of the project, to the need for early renourishment, and to the negative public perception of project performance.
There are at least twelve identified possible causes of EHSs (Dean, et al 1999). EHSs can occur as a result of non-uniform wave conditions along the shoreline, pre-existing natural or constructed structures, non-uniform sediment sizes along the shoreline and sediment transport into a borrow pit. Table 1.1 lists the twelve identified types of EHSs and classifies them




according to these four generic causes. Some types of EHSs have one or two associated cold spots (ECSs) as indicated in Table 1.1.
Table 1.1 Possible Causes of Erosional Hot Spots
Associated
Type Cause Related to
ECS?
1 Dredge Selectivity Sand Size No
Residual Structure Induced
2 Pre-existing Structure No
SlopePreisigSrcue N
3 Borrow Pit Location Wave Transformation Yes
4 Breaks in Bars Wave Concentration Possibly
5 Mechanically Placed Fill Less Fill Placed No
Profile Lowering in Front of
6ewalsPre-existing Structure No
Seawalls
7 Headlands Pre-existing Structure Yes
8 Residual Bathymetry Wave Transformation Yes
Losses Over or Through Less Fill Available to
9 No
Reefs Beaches
Wave Focusing Due to
10 Offshore Translation of Wave Focusing Yes
Beach
Wave Focusing Due to
11 Wave Focusing Yes
Offshore Bathymetry
Borrow Pit Located Within Trapping of Sediment
12 No
Active profile Zone Within Borrow Pit




1.2 Anna Maria Key Shore Protection Project
Anna Maria Key is located in Manatee County approximately on the central coast of West Florida (Figure 1. 1) along the Gulf of Mexico and includes the beaches of Holmes Beach and Bradenton Beach. Anna Maria Key is a sandy barrier island approximately 7.2 miles (11. 5km) long and is bounded on the north by Passage Key Inlet and on the south by Longboat Pass.
FLORIDA .'
Figure 1. 1 Manatee County Location
The Anna Maria Key shore protection project was authorized by Public Law 89-298 in 1965 and originally consisted of the restoration of 3.2 miles (5.1km) of the Gulf beach of Anna Maria Key. In 1989, the authorized project was modified to provide for restoration of 4.2 miles (6.7km) of shoreline and construction of a 0.5 mile (0.8km) beach fill transition zone at the southern end of the project area in order to reduce the effects of the spreading out losses.




Project construction commenced on December 24,, 1992 and was completed on February 24, 1993. The total volume placed was 2.21 million cubic yards of sand.
1.3 Purpose of This Study
This report presents data and analysis results based on beach profile monitoring, and the resulting shoreline changes and sand volume changes. The report draws upon monitoring data availab le for the period following construction of the beach nourishment project for quantitative analysis of the beach fill performance and understanding of the coastal processes in the study area, focusing particularly on areas within which the project performed poorly compared to expectations or neighboring areas. These areas will be referred to as Erosional Hot Spots (EHSs). The identification and possible cause(s) of EHSs are also presented.




2. DESCRIPTION OF PROJECT AREA

2.1 General
Anna Maria Key is the northern-most island entirely within Manatee County extending from Passage Key Inlet at the north to Longboat Pass at the south,, encompassing a length of 7.2 miles (11.5 kin). The most significant causes of shoreline changes on Anna Maria Key are due to the following (Liotta, 1999):
" Construction of shoreline stabilization structures.
" Construction of the Manatee County, Florida,, Shore Protection Project
in 1993.
" Hurricane Opal in October 1995.
Each of these is discussed in the following sections. Construction of Shoreline Stabilization Structures
The littoral segment included in the 4.2 mile (6.7 1km) nourishment project was heavily armored with revetments, seawalls, groins, and bulkheads constructed first by local interests and later as public projects. In the early 1950's,, the Anna Maria Island Erosion Prevention District installed about 100 stone groins varying in length from 50 to 70 feet (15.2 to 21.3 in). In 1959, the State Road Department constructed 20 additional concrete groins along the southern end of Anna Maria Key at Coquina Beach. In subsequent years, two permeable groins, 460 and 320 feet (140 and 97 m) long respectively, were built in an attempt to stabilize the shoreline.




Manatee County Florida. Shore Protection Project
The Manatee County, Florida, Shore Protection Project was authorized by Public Law 89-298 in 1965 and originally consisted in the restoration of 3.2 miles (5.1 kin) of the Gulf beach of Anna Maria Key (U.S. Army Corps of Engineers, 1989). In 1989, the authorized project was modified to provide for restoration of 4.2 miles (6.7 kin) of shoreline and construction of an additional 0.5 mile (0.8 kin) beach fill transition zone at the southern end of the project area in order to reduce the effects of the spreading out losses (Figure 2. 1).

4'
I -.

Tampa. Bay

R-1

7 14 4

F
Holn

t-10
~es Beach
R-20
Palma
Bradenton Beach
R-40
Longboat Pass
Long~boat Key
'0R-50 'I
R-60
Sarasota

Figure 2.1 Anna Maria Key in Manatee County

Anne Maria




The nourishment comprised the placement of 2,028,000 yd3 (1,552,000 m3) between DNR Monument R-12 and R-33A with an additional 180,000 yd3 (140,000 m3) transition between Monument R-33A and R-35, a total distance of 4.7 miles (7.5 km). The average nourishment density for this project was 89 yd3/ft (225 m3/m), an amount considered as reasonably substantial. Periodic required renourishment of approximately 664,800 yd3 (508,000 m3) was estimated every 9 years, corresponding to a renourishment rate of 73,900 yd3/year (56,000 m3/year). The borrow area was directly offshore of the southern portion of the project area in water depths between 17 feet (5.2 m) and 20 feet (6.1 m). Based on profile surveys, the borrow area was located at distances ranging from 1600 feet (490 m) to 2600 feet (800 in) from the pre-nourished shoreline, and extended from Monument R24 to R-34.5. The design of the cross-section increased the berm width by approximately 75 feet (23 m) at an elevation of 5.0 feet (1.5 m) above NGVD. The design berm is located seaward of the Corps construction line, which was established near to or seaward of the pre-construction shoreline. The design included seaward slopes of 1:11 from the berm to the MLW shoreline position, and 1:27 until intersecting with the existing bottom profile. The project commenced on December 24, 1992 and was completed on February 24, 1993.
Hurricane Opal 1995
When Hurricane Opal passed 325 nautical miles (602 km) west of Manatee County in October 1995, it was a Category 4 hurricane with highest sustained winds of 150 mph (67.1 m/s). Wave heights of 22.6 feet (6.9 m) with a dominant wave period of nearly 13 seconds were recorded by Buoy Number 42003 of the National Data Buoy Center. This buoy was located




approximately 210 nautical miles west of Manatee County. The Corps of Engineers reported that Hurricane Opal produced an estimated storm surge of 1-3 feet (0.3-1.0 in), strong winds and wave action. These conditions, combined with two higher than normal tidal events resulted in waves overtopping the beach berm, flooding the back area of the project and transporting sand to the back beach or offshore. Based on observations, the shoreline retreated an average of approximately 30-50 feet (9.1-15.2 in). The Corps also reported that the southern area of the project between Monument R-24 and R-33 was particularly affected.
2.2 Sediment Characteristics
In 1988, the Jacksonville District of the U.S. Army Corps of Engineers collected surface samples on 10 profile lines spaced 3000 feet (915 m) apart along the project area. Samples were collected along each profile line at three-foot elevation increments above the NEW, and five-foot increments below the NEW. Also in 1988, The Corps drilled twenty-five borings in the principal alongshore borrow area. The composite mean grain size of the native beach and borrow area were 0.36 mm and 0.30 mm respectively. The two composite distributions were -poorly sorted with a composite sorting value of 1.47 for the native sand and 1.51 for the borrow area sand. The mean value of the visual estimate of the shell content for the native and the borrow area samples were 27 percent and 21 percent, respectively. Subsequently, an acid treatment was applied to all the samples in order to determine the contribution of the shells to the grain size distributions. After removing the carbonate fraction, the composite mean grain size and the sorting were 0.17 mm and 0.47 (well sorted) for the native sand and 0.12 mm and 0.46 (well sorted) for the borrow area sand. Figure 2.2 shows the




composite cumulative mean grain size distributions for the native beach and the principal alongshore borrow areas before and after the acid treatment.
MANATEE COUNTY- -i fill fill fi Jill s s 111s1 Ms ls u *
HOM Pf9rECrOfN PFOEjCT .
COMPOSITE GRAN SiZe
DISTRIBUTIONS S--- ---P9
g. .g T VS A ES CI AT
PC'! c- asAT s o
ll fIl I Il I i f ii l 8 W l L ff If Ha fU li i f l l it 1 1 tL t gng 40
-_- i. Ph 1
,,I / I/
V 20
,11
tllIII Ill I!1 I!1 !11 1 llt Ilt II 1 I !1!11 !!1 II! !11:[1tl II1!!1 II!I! 1 0

.P- a- .
P S. RI, .
. .. '' I lllll t~0 085l

S MILLIMETERS
MILLIMETER S

Figure 2.2 Grain Size Distribution for Native and
Borrow Area Sediments With and Without Carbonates

_" T

-l, -i,-I

SWEE

V.40 %0.92

s.o 4O




2.3 Data Sources
A number of monitoring surveys have been conducted for the Anna Maria Key Project. The data used in this report are listed in Table 2.1. Postconstruction survey data are included in the State of Florida, DEP database that is available on the Internet at the Website www.dep.fl.us/beach/. The pre-built, as-built and post-storm (March 1993) data are from Coastal Planning & Engineering.
Table 2.1 List of Survey Data Used in This Report
Date Source Average Offshore Data Description
Extent of Data (ft)
Pre-Built" CPE" 700 Beach and Offshore Profiles
As-Built"" CPE 700 Beach and Offshore Profiles
March 1993 CPE 3200 Beach and Offshore Profiles
August 1993 DEP 2756 Beach and Offshore Profiles
October 1993 DEP 3270 Beach and Offshore Profiles
February 1994 DEP 2673 Beach and Offshore Profiles
May 1994 DEP 3015 Beach and Offshore Profiles
February 1995 DEP 1219 Beach and Offshore Profiles
July 1997 DEP 2558 Beach and Offshore Profiles
March 1998 DEP 2630 Beach and Offshore Profiles
February 1999 DEP 2615 Beach and Offshore Profiles
* Coastal Planning and Engineering
** Department of Environmental Protection
* These two data are from R-12 to R35, while others from R-9 to R40




It is noted that monuments at some survey lines were moved during the years from their original positions. All results presented in this report are referenced to the monument positions immediately prior to construction. The data listed in Table 2.1 were used to compute NGVD shoreline changes and volumetric changes. In the calculations, within the project area (R-12 to R-35), the results are referred to the as-built data; outside of the project area, because no as-built data are available, the results are referred to the post-storm survey (March 1993). This is equivalent to assuming that storm-induced shoreline changes outside of the project area are minimal.
2.4 Beach Profiles
Comparative profiles in the area of interest for eight different surveys have been plotted at each monument and are presented in Appendix A.

0 500 1000 1500 2000 2500
Offshore Distance (ft)
Figure 2.3 Comparison of Average Profiles of Monument R-20 to R-27 for Four Surveys

3000




Figure 2.3 presents the average profile for monuments R-20 to R-27, the central one-third part of the project area, for four survey dates: pre-built, asbuilt,- 02/1994 and 02/1999. After 6 years approximately one-third of the original nourished beach width remains in place. The post-nourishment bar appears to be more prominent than prior to nourishment. Finally, it appears that a minor amount of sand has been transported into the borrow area. In most of the profiles it is seen that a portion of the sand has been transported offshore as a result of profile equilibration process, causing the expected recession of the shoreline. It is of interest to note that the mean grain size of nourishment sediment (0.30 mm) was smaller than the native sediment size (0.36 mm). Therefore, as a result of equilibrium profile theory, the slopes of the nourished profiles are milder than for the prenourished profiles. Consequently, the equilibrated dry beach width is narrower than would have been the case for compatible sand.
2.5 Initial Placement
The initial shoreline displacement and volume placements are taken as the differences between as-built and pre-built surveys. Here as-built survey is considered to be the survey immediately after the nourishment project. The volume placements here are the input to the numerical model study. Figures
2.4 and 2.5 show these results.




---------- ............... --------------- ............... --------------- ..... --- ... ..... ............... ------..... ...............
12 0 ............... ................ .............. ................ L ............... I ............... ------_------- --------------- ............... ------------ ............... ------Z)
0
.. ........... ..... ................
100 ................ ..... ......... ............... .. ............... .............. ......... ---------------- t -----------. ............. ................ --------------- ..............
80 .................... .... ...... ............ ......................................................... ..............
................ ............... -------------- ---------------- ----------- ..........
60 .............................. T ............... t ............... .............. ................
0
............... ............................... ........... ............ -------------4 0 ............. .... --------------- - ------------- -_------------- ------2 0 ............. I ................ ............... ............ ... --------------- ............... ............
--------------- ---------------- -------------------- ......
................
A

400
-350
.0 300-.4.0
0
le
"1 250
W
200-
150
Cd
100
50
01
12

14 16 18 20 22 24 26 28 30 32 34
Monument
Figure 2.4 Initial Shoreline Position Based on
Shoreline Changes between Pre-built and As-built

160

26 28 30 32 34

I12 14 16 18 20 22 24 Monument

Figure 2.5 Initial Volume Placement Based on Profile
Changes between Pre-built and As-built




2.6 Shoreline Changes
Figure 2.6 presents the shoreline changes determined from the profile surveys after the construction of the shore protection project, where the shoreline positions of as-built within the project area and March 1993 (poststorm) outside the project area have been taken as references respectively.
150 1 r[ T T ~ ~ r
10 Project Ar ea
0
06
08/1994
10/1993
W20 .....02/1995
o 0- 03/1998
-250 1 1 1 __ __ a-219
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Monument
Figure 2.6 Shoreline Changes for Different Periods Relative to As-built
The 1999 data show that within the project area (R-12 to R-35) the shoreline receded on average 124.6 feet (38.0 m) after 6 years. The average shoreline recession of the center segment of the nourished area (R-20 to R27) is 103.3 feet (31.5 in), while those of the northern (R-12 to R-19) and of the southern part (R-28 to R-35) are 133.8 feet (40.8 m) and 136.6 feet (41.6 in), respectively. Greater shoreline recession near the extremities of the




project is in agreement with the planform evolution theory and with the initial additional volume densities and shoreline widths near the ends (Figure2 2.4 and 2.5).
Several results are evident from Figure 2.6:
- The August 1993 (6 month after construction) shorelines exhibit a
substantial recession (average 70.0 feet (21.3 in)), undoubtedly due in part to the March 1993 storm after construction. This storm caused
offshore sand transport and profile equilibration.
- From August 1993 to October 1993, the shoreline experienced a
surprising average advancement, especially in the project area from R-12
to R-35,, where the average advancement is 12.3 feet in two months.
- In the segments adjacent to the project area (from R-9 to R-12, and from
R-35 to R-4 1), the shoreline has experienced alternating accretion and recession. Accretion would have been expected due to the spreading
losses from the nourishment.
- The southern part of the project area (R26 to R33) receded more than the
northern part of the project. Most of this difference occurred between the February 1995 and July 1997 surveys and is probably a result of Hurricane Opal which occurred in October 1995, and the oversteepened
profiles compared to the remainder of the project.




2.7 Volume Changes
Figure 2.7 presents the volume changes determined from the profiles for different survey periods relative to as-built within the project area and March 1993 outside the project area, respectively. The results of cumulative plan area and volume changes in the project area are listed in Table 2.2.
100 1 r 1
S 60- ---- Priqje-f irec -----...... ......
40...r .......... ..... ..... ..... .... ....................... ....... ---40
-20 .......... ... ... . ... 44 ~ .... .....i. .. .
4) 08/1993
~ 4 0 .*... ..... 10119--- ------ ----- ----- --3--.10/199
--------02/1994
>0 -60 ............................ ........ ............ ............... ....................... .........
-so + 02/1995
. e-0311998
2-1001- 02/19991
911 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Monument
Figure 2.7 Volume Changes for Different Periods Relative to As-built
From Table 2.2, the same feature observed in shoreline changes appears in the periods between August 1993 and October 1993, there is a volumetric increase in the project area. Also in the periods of February 1994 to August 1994 and March 1998 to February 1999, the volume change is positive. These volume increases suggest possible survey errors.




Table 2.2 Total Plan Area and Volume Remaining at Different Surveys in Project Area (R-12 to R-35)

O ......... .... ................ ----------------.............
-e 0.4n Ara eminn
0 g .... ......................... ............... ...............I.........
0
0 1 2 3 4 5
Time (yr)
Figure 2.8 Proportion of Total Volume and Plan Area Remaining in Placement Area (R12 R35) Relative to As-built.

Total Plan Area Total Volume Remaining Survey Remaining (million ft2) (million yd&)
As-built 4.59 2.13
August 1993 3.11 2.08
October 1993 3.36 2.11
February 1994 2.65 1.89
August 1994 2.46 2.00
February 1995 2.51 1.92
July 1997 2.03 1.77
March 1998 1.66 1.75
February 1999 1.89 1.88




The percentages of the total volume and plan area remaining in the various surveys are shown in Figure 2.8. For the overall surveyed period from asbuilt to February 1999, the area within the original project lost an estimated 0.25 million cubic yards of sand. This represents approximately 12% of the original placement. The erosion rate associated with this volume loss is 41,669 yd3/year, which is substantially smaller than the estimated renourishment rate (73,900 yd3lyear). The project has performed very well in terms of volume losses. Figure 2.8 also demonstrates that the profiles within the project area continue to equilibrate after 4.5 years. If the profiles had equilibrated as of the as-built survey, the two curves would be approximately the same.
The differences between volume and shoreline changes near the ends of the project are of interest. As shown in Figure 2.6 and discussed earlier, the southern end of the project receded more than the northern end subsequent to the February 1995 survey. However, as shown in Figure 2.8, similar differences in volume changes are not evident. This implies that the constructed profiles were steeper near the southern end of the project compared to those near the northern end.




3. PROJECT PERFORMANCE PREDICTION

3.1 Predicted Beach Planform Evolution Numerical models have been developed to predict the performance of beach nourishment projects. The model applied here is the "one-line model", developed by Dean and Grant (1989) for the Division of Beaches and Shores of the Florida Department of Natural Resources. This model is referred to as DNRBS. Realistic conditions can be incorporated, including arbitrary initial shoreline position, littoral barriers, and background erosion rates. This model was applied to the Anna Maria Key project to predict its performance. An ad-hoc transformation has been applied to the prenourishment shoreline and contours to render them straight and parallel. The background erosion rates (Dean, et al, 1998) are listed in Appendix B for different time frames: long-term (from 1874 to 1986) and short-term (from 1974 to 1986). The long-term data are considered the best basis for the overall trend, including any anthropogenic effects, and thus are applied in the present analysis.
The representative wave and site characteristics are those recommended by Dean and Grant (1989): effective deep water wave height Ho=1.6ft, effective wave period T=5.8s, wave direction ao=240.00, shoreline orientation ,80 =330.00, depth of limiting motion h,=13.7ft, and berm height, B=5.Oft above NGVD.
The initial position is taken as the measured volume changes between prebuilt and as-built (as shown in Figure 2.5). Calculations were carried out using the sediment transport coefficient, K=1.1, recommended by Dean and Grant (1989) for a sediment size of 0.30 mm. The boundary conditions are




taken as y = 0 at both ends of calculation domain, i.e. the shorelines at Monuments R-1 and R-41.
3.2 Comparison between Measured and Predicted Changes The comparison of predicted and measured shoreline advancement and volume remaining from as-built to: August 1993, February 1994, February 1995, July 1997, March 1998 and February 1999 are presented in Figures 3.1, 3.2, 3.3, 3.4, 3.5 and 3.6 respectively. In order to quantify the degree to which predictions agree with field measurements, the deviation relative to as-built conditions within the project area is calculated as
N
where N is the number of points (N=24 in this case), and Ay represents the shoreline changes. The same expression is applicable to volume changes. Another measure is relative to a reference value, in this case, the measured changes,
apm N
where the subscripts "p" and "in" denote the predicted and measured data, respectively. Of particular interest is the relationship om /a which is a measure of the model predictive "skill" for the overall planform evolution. For this expression approaching zero, a good overall prediction is considered to have been made, whereas for this expression approaching unity, the model is said to have zero predictive skill. Table 3.1 shows the results for o., o-pm, and a.m /om.




Pre-Built-08/1993

35
25 21 20 15
0
5

Pre-Built-08/1993

9 11 13 15 17 19 21 23 25 27 29
Monument

31 33 35 37 39

Figure 3.1 Comparison of Predicted and Measured Shoreline Advancement and Volume Remaining from Pre-built to 08/1993. (Average Values Listed Represent Those within Project Limits)

Annlf

'=I*V

1
1 o1
cc li)

Avo. Meas. S4oreli.!e AdVanc4ment 13.3 t Measured
0 -.A....re...Sho~rein0.Ad-V:ancennt ....... 11124t,.......... .E .... -e- P re d icte d
. /, .. .... ---- As-Built
Ave', As-B3uilt $hore:lne Advan~emeht=- 213.1 i,/i
0 0 ..... i ..... ..... ............... i ........... ........... ------ ----- ........... ........... --.....---... ....... ,......... ....... ------ ----------- i........ .....
0o ......... ----- ........... ..... .... ........... I ............ i........... I ........... ... ........ ......... ....... ........... ........... ........... !.....
oo ......... i........ X;: .......... ........ :,." I . ....... : :- ': ? ..... .... .... ............. -" ....... ......... ........... i............ .----- i.......R ---- -- ------ ----- ........... ...........
. .. . .. .. ....
-E3-- E
so .......:..-.-.A .. ....... ...... .. .... .......-.. .-i. .. o. ..! ...... ....... ...... ...
w / R l i l l i ,B
-0 -- .............. ... .............. ........ ..... ...... .-.... -----.---... i --------- --------....i.. -....."vetA e
__0 I i i i i i i i I I i 1
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Monument




P re-B uilt-02/1994

Monument

Pre-Built-02/1994
I I I I I j9I ,. IT[V
[Ave. Meas. Vol. Remaing= 88 0 yd/ft
... L -...i ,.. .._ L ... .... ...3 ........ % .......... ."I..........- -_-

IVC. r Iul.V 1. 1Iil% U ,Ave. As'Built:Vol. Placenent..... ..... t : : ........... ........... :............
.. ... .......

1 YU at 100i4 yd~ft

.1 ~ V /~\

-I- Measured
--E- Predicted
* As-Built

..... ...... 7 ... ... ......................- ........... ........... ........... ... .. -r... .. ... -------- ....... ........... ...........:...
0 0 .......... : --- --- -- -----... ... " .......... ....... .... ........ .. ... ... ./ .... .. ..... ... -'-4 ........... ........... ........... i....
8 0 ....... .. ............ ......... . .. .. .... .. .. .-.... . .. ... ".......... ..... ..... ..
S. i Prjec t Ar pa
, o . ....... ....... i) I.. !. ....... ....
2 0. .. 1 ........... .........-- ........... I ----------- ........... I ----------- -- -- -.. . --.. .. ..-- .. ..--.. .. .. .......... .. . ... .. . . .
20

9 11 13

15 17 19 21

23 25 27
Monument

29 31 33 35 37 39

Figure 3.2 Comparison of Predicted and Measured Shoreline Advancement and Volume Remaining from Pre-built to 02/1994. (Average Values Listed Represent Those within Project Limits)

,300
'S
250
14
200
150
o 100 ri

80 60
40

M
1
Z)




40

-100L
9

11 13 15 17

19 21 23 25 27 29 31 33 35
Monument

Pre-Built-02/1995

9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Monument
Figure 3.3 Comparison of Predicted and Measured Shoreline Advancement and Volume Remaining from Pre-built to 02/1995. (Average Values Listed Represent Those within Project Limits)

Pre-Built-02/1995
0 Ave. Me4s. SIre.e Ad.Vancnent 105.8 Measured
0 _Ave.Pro.d..S4relia.Ad. ana en......I9.f ...... .. ....... -- Predicted
Ave As-Built Shoreline Advanemeht 213.1 ft ... As-Built
0 ..... ......... .. ----- ---- --- -----........... ........... .......... T .. .............
-_-_---_--------. ------ ...... . .... ........... ............ ........... I ........... !........... I------ I .........i ........... i ........... ..............
o ... :;: .-..s I. ..; i
0 ,--0
fltg
0
0--- ---------Project Ar a
o -- -.....- --.-.

35 30 25
S20 15 10
0
.4 5 Wa

120
100 80
S60
5 40( S20




Pre-Built-07/1997

400

Monument

Pre-Built-07/1997
}0 I I i i I [ 3
Ave. Mets. V4L Reimain g 83.6 yd .ft E- Measured
o--Av4:--Pre0---Vo Rcaaini4g ----. -d-t.............. --- Predicted
Ave. As-uilt Vol. Placeient4 100.4 yd3ft 0 *.... As-Built
...... ............ ... ............. ..... ...... ..' ........... .......... q........... .......... I"" ...........-. ......... ..... I ------------ I ------ ........... ....
o ........ %
,o .......... ............ I.- .... ...... .......... ..... ........., .. ... ........ .... .a ...... .... .... ... .. .......... .................. ,. .......... ...... 7..
0 .. ... ----- ............. ........... ........... .... ... . ........ --- -....
0 ...... ... ........ ".... ....... "..... .. .......... ".. ..."......: ..... -....."......".. ....... .. ...... ......... .. ...... ....
|0 J i i i .
o tr
P)roj ct A ea
0.
0 ~ ...... ------ ------ t I----- ------4------ .....J............. ------4 ------4 .....I ......I ........

9 11

13 15 17 19 21 23 25 27 29 31 Monument

33 35 37

Figure 3.4 Comparison of Predicted and Measured Shoreline Advancement and Volume Remaining from Pre-built to 07/1997. (Average Values Listed Represent Those within Project Limits)

16
14 12 10 [8
6

-4




40

23 25 27 29 31
Monument

Figure 3.5 Comparison of Predicted and Measured Shoreline Advancement and Volume Remaining from Pre-built to 03/1998. (Average Values Listed Represent Those within Project Limits)

35 30
- 25 S20 <15 10
0

Pre-Built-03/1998
0 I I I I
Ave. Meas. Shoreline Advanc Iment 78.2 f -e- Measured
0 --Av.-Pre4i.--Sh reline-Adanceinent ...... 142. .... .. -e- Predicted
Ave. As-built Shoreline Advancement= 233.1 t / ----0.-- As-Built
0 ........... .-- ----- ---------- --- -, -------- ------- ---- --. .... .
0 ----- ------ ---- ..... ....
01 . i ............................. T,----.- ------ ...... .......... .......... .......... ...
......... .......... ..::..... ....... !.i ....... ; ... ...... < : ....... .......... .. ... ............. ..
o ..-....z .+ ,- .... ... I.. ..... ...............
......, ',....... ...... ....... . ....... .. ...... ...... -- ...... "-......... i---- ....... ....- ................ ...........
0 ......... .. .. ..... ..... .... ....... ........... r .. ............. ....... 7 ........ ... .....' ........ --..........---...
0 0@
0
Project Area. I
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Monument
Pre-Built-03/1998
n'




Pre-Built-02/1999

9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Monument

Pre-Built-02/1999

WM I I I I I Z t 1 I I I
Av6. Meas. VoL Remainhg= 87., yd /ft ---- Measured
0 --A-ve.--P-re.;--Vol--Rehainig ..... -6-7-6,1y& --/f-t .......... ......... -. Predicted
Ava. As-Built Vol. Placenent- 100.4 ydaft 1 .... As-Built
,0 ........ i y : ; :: l...... i......I. ..... i.......... i ......... ........ .... ... ....... i ........ i.......... ....*........ ------ ---------- --
. ........ ... .. ... ......... . ...." .......... .... ........ ...... ... ... ....... .......... .......... "
0i ... ..... .. ----... .. ..... .... ..... ------ -------.... .......... ...... ... ....... ..... ... .... .......... ..
S0 ................. .. .. ...... .... ----- -- --.... .. ...--.. ... .......
0 ... ...........
40.
Project Ar.a

13 15 17

19 21 23 25 27 29 31
Monument

37 39

Figure 3.6 Comparison of Predicted and Measured Shoreline Advancement and Volume Remaining from Pre-built to 02/1999. (Average Values Listed Represent Those within Project Limits)

400

350 300
-4250 200 <150
.)
$- 100

U't

4)

-20L
9

VT.

18




Table 3.1 Deviation of the Shoreline and Volume Changes

Shoreline Change Volume Change
S u rv ey P erio d s m aRm pinpm/ m m P, pm / a .
(ft) (ft) (yd3/ft) (yd3/ft)
As-built-08/1993 76.8 70.6 0.92 19.0 18.5 0.97
As-built-02/1994 102.9 89.3 0.87 18.8 18.5 0.98
As-built-02/1995 107.1 86.4 0.81 21.6 23.0 1.06
As-built-07/1997 136.2 97.4 0.72 32.3 19.3 0.60
As-built-03/1998 148.0 108.3 0.73 33.8 19.9 0.59
As-built-02/1999 138.7 92.6 0.67 32.6 23.6 0.72
Although the results shown in Figure 3.1 through 3.6 appear to provide a generally good fit, the quantitative measures applied and presented in Table
3.1 generally do not indicate a high degree of predictive skill. The measured and predicted average beach widths and volume densities within the project area are shown in Table 3.2. Figure 3.7 presents the comparison between predicted and measured percentages of planform area and volume remaining in project area. Because Ay= AV/(h. + B), the predicted proportional plan area and volume remaining are the same. Both Table 3.2 and Figures 3.1 to 3.7 shows that initially the model underestimates the shoreline increases and later overpredictes the shoreline increases. The interpretation is that initially the profiles had not equilibrated resulting in measured beach width greater than equilibrium and later the smaller nourishment sand resulted in smaller beach width than would have occurred for compatible sand. The time scales of profile equilibration and




alongshore equilibration are disparate: profile equilibration occurs in a few years, whereas the alongshore equilibration varies in duration and is related to project length, sediment size and wave environment (National Research Council 1995). For example, a reasonably long project may require decades before 50 percent or more of the sand volume is transported to the adjacent beaches. We note that after 6 years, the Anna Maria Key beach nourishment project has only lost 12% of the volume placed and the measured rates of loss are decreasing in accordance with beach nourishment theory.
Table 3.2 The Measured and Predicted Average Beach Widths and Volume Densities within Project Limits
Time As-built 08/93 02/94 02/95 07/97 03/98 02/99
Predicted
Beach Width 145.0 131.2 126.7 119.4 105.0 102.5 97.6
(ft) __Measured
Beach Width 213.1 143.3 121.7 115.8 96.2 78.2 88.5
(ft)
Predicted
Volume 100.4 90.8 87.8 82.7 72.7 71.0 67.6
Density (yd3/ft)
Measured
Volume 100.4 97.8 88.0 87.1 83.6 82.3 87.5
Density (yd3/ft)




-4,
............................................................................................................
9 ................. ..................... ................
8 ---- ---- ---------------------------- ........ ........................... ------------------- ------- ---------------------7 --------- N ..... --------------------------------------- ------------------------------- --------- .................. -----6 ------------------ .........................................................
------ ---------------------- ------------------------ I ............ ................
5 ......................... ............................ ........................... ................................................................. -----El,
4 ......................... ...................... .............................................................. ....................... ..... .......... ....
3 ------------------------------------------------------------------------------------ I ---------------------------- I ............................ I --------------------------
2 -------------------------- --------------------------- ------- ------------------- --------------------------------------------------------- I ---------------------------e- Measured Volume Remaining
- ------------------------...... --------------------- ------------------- -E3.- M easured Plan Area Remaining
Predicted Remaining
01
0 1 2 3 4 5 6
Time (yr)
Figure 3.7 Comparison of Predicted and Measured
Plan Area and Volume Remaining in the Project Area

V.
0.
0.
0.
04




4. Identification and Probable Cause(s) of Erosional Hot Spot(s)
4.1 Erosional Hot Spot Identification
An erosional hot spot is considered as a local area where the project performs poorly compared to expectations or neighboring areas. To be termed a hot spot, the shoreline must behave atypically. For example, at the ends of the beach fill area, the shoreline typically loses more sand than other areas. However, these areas are not considered as hot spots, because this behavior is an expected planformn evolution feature. However, if the sand losses are greater than expected, these areas are then identified as hot spots. To establish a criterion to determine the presence of an erosional hot spot, first we calculate the mean alongshore value of both predicted and measured shoreline advancements within project area for each survey, Y' (t), then normalize the shoreline advancements as y(x, t) /IY' (t), and finally take the time average of these normalized shoreline advancements. These predicted and measured values are then compared and the areas where the measured value is substantially smaller than the predicted value is considered as an erosional hot spot. The same procedure is also applied to volume remaining. This method can reduce the effect of measure errors and averages over the various surveys thus addressing the overall project performance. The results of this procedure are shown in Figures 4.1 and 4.2 for shoreline advancement and volume remaining, respectively. Shoreline advancement comparison (Figure 4. 1) identifies two erosional hot spots: one between R-12 and R-14, another between R-17 and R-28. From volume remaining comparison, the area from R-17 to R-23 and the area from R-26 to R-28 can be identified as erosional hot spots.




0 .5 /
~ro~Measured
9 1 1 13 15 1 1 1 oumn
-E- Mreaiured
.....0 ~r .. ........... .......... ....... ..... i... . -- ----.. .'.. ...... .... ...... I ........... ........-..
w 1.2B Preicte
i~ / 'El i i
4) 1 1: i i i \
S i .. i i
0 ..0.6...... ......................------.---------------------2' -- ..... ............. .
I .. ...... ...................... ........................ .........------------ ....................... ..... ....i...............................
0. / .4 i 1'i
cc
z Borro*4 A re i
-0.5 1 1 L L__ I I I I I I L
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Monument
Figure 4.1 Hot Spots Identification Based on Shoreline Advancement
1.4 i
i ,, ik i-E3- Predicted
.2 ..----.. :...... ........------_ ---------------------......I.... ......... .
. . .......... ... ... / ........... ," ---- .. -- --........ ---........ ........ ..... . ... -:-....... ..... ...... . ....... ..........T "
0 - - . . -- - . . . . . ..... . .. . ... .. . . ......... - - -- - - .......... -- -- --...--- --- - --T
wi< 0.6 ......... --- --- ---------- ------ ---------- --------- ............ I ---------- t -----.......... t .. ..... ........... .......... T
0 o ...... ..... ..........i ........... ------ ----------- .......... .......... .. ........ .-......... ........... .......... ---- ....
z 0 -1 --- ..................;.......L.... . . ... ........ ...... ...... .... .... ...... .....
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Monument
Figure 4.2 Hot Spots Identification Based on Volume Remaining




4.2 Analysis of Possible Cause(s) of Hot Spot(s)
4.2.1 Hot Spot between R-12 and R-14 A possible cause of this hot spot is dredge selectivity. This potential cause of the EHS is related to different sizes placed along a particular project during the nourishment process. Borrow areas usually contain sub-areas of coarser and finer sediments. In order to reduce costs of pumping, the dredger is likely to choose to pump the finer sediment to those greater distances of the project. Substantially more amounts of finer sediment are required to advance the shoreline to a particular width than for coarser sediments. If the volume density of finer sediment placed is the same as coarser sediment it will result in a narrower beach width that may be considered as an EHS.
The sediment distribution of the borrow pit area of this project (Figure 2.2) shows that the size is poorly sorted with a composite sorting value of 1.51. That means significant variation in sand size exists at the borrow pit, the borrow pit is located offshore of Monument R-24 and R-34. The dredger may pump finer sand to the project's north end. However, the sediment distribution along the shoreline after nourishment and the detailed fill placement documents is not available. A conclusion cannot be made that dredge selectivity is the cause of the hot spot between R-12 and R-14.
4.2.2 Hot Spot between R-17 and R-28 The possible causes of this hot spot are considered including profile lowering in front of seawalls, borrow pit location within active nearshore zone and wave transformation due to borrow pit. Each possible cause is examined in the following.
Profile lowering in front of seawalls: Prior to beach nourishment construction, erosion had occurred to the degree that no dry beach was




present immediately fronting a seawall at some sections. In some unusual cases a substantial water depth may occur adjacent to the seawall. In these cases, application of the usual design relationships between shoreline advancement and required volumes will underestimate the volume density required resulting in a smaller equilibrated beach width than anticipated which may be considered as an EHS. The profile at Monument R-25 is presented in Figure 4.3 and shows that there is no dry beach before the project. Also from the plan view of the barrier island before the project construction (Corps of Engineers, 1989), the shoreline at this portion was seriously eroded.
R-25
10
Pre-Built
5 .................... ................................................... ------------------------- ........................ A s-B u ift
........... 08/1993
............. ............................................................................ ------------------------ ...... 0 2 /1 9 9 4
02/1995
- --- -- ------ ......................... .................. ------ 0 7 /19 9 7
.... 03/1998
_1 U ............ ........ .................... ..................
........................ ------------------------ 0 2/19 9 9
0
!Borrow P
1 5 ................... ............... ------------- ----------- .......................... I ................. ..... ......................... ------------------------2 0 ....................... ................ ..................... ------------------------------------------- ------- ---------------2 5 ...................... .............................................. ........................ ........... ................................... ....................
-3 0 ....................... ..................................................... ...... ................. ......................... ........................
-35 L L L_ L
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)
Figure 4.3 Pre- and Post-nourishment Profiles at Monument R-25
Borrow Pit Location within Active Nearshore Zone: If the borrow pit is located so far landward that it could either induce seaward sediment transport into the pit or trap sediment during normal seasonal or storm




related cross-shore transport, an EHS landward of the pit will result. Kojima et al. (1986) found the possibility of a link between beach erosion occurring on the northern part of Kyushu Island, Japan and dredging activities in that area. They found that the dredged holes in their study area were refilled with sediment originally from the hole's landward side. They suggested that mining take place in depths of 35 m or greater to avoid any effects on the shoreline.
From the profiles at Monument R-24 to R-28, it also found that a small amount of sand had been transport into the dredged pit. Thus, the pit may be located within the active nearshore zone thus causing sediment losses and contributing to the landward EHS; however, this effect is considered relatively minor.
Wave Transformation Due to Borrow Pit: Borrow pit locations can interact with waves and causes a modification of the wave patterns along the shoreline and thus a nonuniform quasi equilibrium beach planform. Considerable research has been conducted to qualify the influence of the dredged holes on the shorelines. Gravens and Rosati (1994) and Horikawa et al. (1977) found that dredged holes could cause shoreline advancement. However, other researchers such as Motyka and Willis (1974) obtained a totally different result with beach recession occurred behind dredged holes. In summary, the wave transformation processes associated with a borrow pit depression are complicated and the available documentation suggests that, landward of the borrow pits, it is possible for either shoreline advancement or recession to occur.
From the analysis of the three possible causes of the EHS, profile lowering in front of seawalls and borrow pit location within active nearshore zone are believed as the most probable causes of the hot spot here. Wave




transformation due to the presence of the borrow pit is another possible cause which requires further evaluation.




5. SUMMARY AND CONCLUSIONS

Based on the seven post-nourishment surveys, the analysis has shown that the Anna Maria Key Beach Nourishment Project has performed quite well. The annual volumetric loss for the period from As-built to February 1999, based on profile changes, is 41,669 yd3/year which is substantially less than the estimated loss rate of 73,900 yd3/year. After 6 years,, approximately 88% of the original placement volume remained within the project area. Locally, based on shoreline advancement, two erosional hot spots have been identified: one between R-12 and R-14,, the other between Monument R-17 and R-28. Based on volume remaining, one area from R-17 to R-23 and another area from R-26 to R-28 are identified as hot spots. Dredge selectivity is a possible cause of the hot spot between R-12 and R-14 near northern end of the project. Profile lowering in front of seawalls and borrow pit location within the active nearshore zone are considered as the probable causes of the hot spot between R-17 and R-28. Wave
transformation due to the presence of the borrow pit is another possible cause which requires further evaluation.




6.REFERENCES

Dean, R.G., and Grant J., 1989, "Development of Methodology for ThirtyYear Shoreline Projections in The Vicinity of Beach Nourishment Projects," UFL/COEL-89/026, Coastal and Oceanographic Engineering Department, University of Florida.
Dean, R.G., Cheng, J., and Malakar, S.B., 1998, "Characteristics of the Shoreline Change Along the Sandy Beaches of the State of Florida: An Atlas," UFL/COEL-98/015, Coastal and Oceanographic Engineering Department, University of Florida.
Dean, R.G., Liotta, R., and Simon, G., 1999, "Erosional Hot Spots," UFL/COEL-99/021, Coastal and Oceanographic Engineering Department, University of Florida.
Gravens, M.B. and Rosati, J.D., 1994, "Numerical Model Study of Breakwaters at Grand Isle, Louisiana," Miscellaneous Paper CERC-94-16. Vicksburg, MS, U.S. Army Corps of Engineers.
Horikawa, K., Sasaki, T., and Sakuramoto, H., 1977, "Mathematical and Laboratory Models of Shoreline Changes Due to Dredged Holes," Journal of the Faculty of Engineering, The University of Tokyo, Vol.34, No.1, pp.4957.
Kojima, H., Ijima, T., and Nakamuta, T., 1986, "Impact of Offshore Dredging on Beaches along the Genkai Sea, Japan," Proceedings, 20th




International Conference on Coastal Engineering, ASCE, Taipei, Vol.2, pp.1281-1295.
Liotta, R., 1999, "Erosional Hot Spots: Causes and Case Studies at Dade and Manatee County," UFL/COEL-99/007, Coastal and Oceanographic
Engineering Department, University of Florida.
Motyka, J.M. and Willis, D.H., 1974, "The Effect of Wave Refraction over Dredged Holes," Proceedings, 14th International Conference on Coastal Engineering, ASCE, Copenhagen, Vol.1, pp.615-625.
National Research Council, 1995, "Beach Nourishment and Protection", National Academy Press, Washington, DC.
U.S Army Corps of Engineers, 1989, "Manatee County, Florida Shore Protection Project, General Design Memorandum with Supplemental Environmental Impact Statement," South Atlantic Division, Jacksonville District.




APPENDIX A
BEACH PROFILE SURVEY DATA




R-9

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

R-10

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

-15'
0

-10
-15
0




R-I I

1 T 1 1

-10.------- ............. --------------------------- .........................................
......._........... ----- -- -- ----- --- --------_

500

1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

R-12

-20I 1 1 1
0 500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

0 0)

P re-Built
---As-Built
.......08/1993
....02/1994
--02/1995
07/1997 ..03/1998 ....02/1999

0

.......................... .................................................................................. ..........................
................ ........................... ........................... .......................... ...........................




R-13

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

R-14

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

-15
-20
0

-10
-15
-20 L
0




R-15

1500 2000
Offshore Distance (ft)

R-16

1500 2000
Offshore Distance (ft)

3500

3500




R-I 7

..... 03/1998
02/1999
-5 .......... .......................... .......................... .......................... ------------------------- ......................... ........................
cis
-1 0 ----------------- ....................... ------------------------- ......................... ...............................................................................
-1 5 ------------------------ L --------------- I L- ---------------------- ......................... ........................... ......................... ........................
-201 1
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft) R-18
10
Pre-Built As-Built
5 ....... --------- t .......................... t ------------------------- t ......................... t ......................... i...
............ 08/1993
....... 02/1994
.. ........................... t ......................... ......................... ----------------- ----------- 0 2 /1 9 9 5
07/1997
E) ..... 03/1998
-5 ------------------ ............................................... ...................... .......................... ..
02/1999
0
-1 0 ---------------------- .. .................. ..................... ......................... ......................... ...................................................
-1 5 .............. ..... ......................... T ......................... ......................... ......................... .......................
-2 0 ----_----------------- ----------------------------------------------------- .......................... --------- ------ - ------------ .............
-25
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)




R-19

..... 03/1998
-5 .......... ........................... ......................... ..................................................... ..
02/1999
0 1 0 ----------------- .. ................... .......................... ...................................................... ----------------------------------------------------
- 1 5 ........................ ..... .............. ..................................................... I ...............................................................................
-2 0 .............. ........ -------------- ------..... ............. ........
-25
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)
R-20
15
Pre-Built As-Built
1 0 ....... ............... .......................... .......................... ..........................................................
............ 08/1993
. ....... 02/1994
5 --------- ............. ................................................................................. ..
..............
02/1995 07/1997 !A ------------- ---------------- ----------------------- .......... .......................... ------------------------------ 03/1998
02/1999
-5 ------------------------ ....... ...................... .......................... .......................... -------------------- -------------->
w 1 0 ---------------------_ ............ . ......................... ...................................................... ....................................................

0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)




R-21

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

R-22

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

-15
-20
-25 L
0

u
-' 5
-10
-15
-20

-25'
0




R-23
10
Pre-Built As-Built
5 .. ........................................... ......................... ---------------------------------------------------08/1993 ....... 02/1994
------------------------- ...................................................................................
07/1997
----- 03/1998
-5 ----------- ......................... I ......................... .....................................................
02/1999
0
0 -1 0 ....................... ....................... -------------------------------------------- ....................................................................... ....
-15 -------------- ........... ........
---- ................. ......... ---------------- ---------------------------------------------------- .......................
-2 0 ----------------------- .................. ........... ...... .. .... ... ......................... ...........................................
-25
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)
R-24
10
Pre-Built As-Built
5 ............ ---------------------------------------------------- -------------------------- ------------------------............ 08/1993
02/1994 ..................................... ...... 0 2 /1 9 9 5
------------------------- -------------------------- ...................
07/1997 ..... 03/1998
5 ........ .............................................. -------------------------------------------------
02/1999
0 -10 ................. .. .. .....................................................................................................................................................
-1 5 ....................... ... ..... ............ ------------------------- -------------------------- ------------------------- -------------------------- -----------------------
. .............. ................
-2 0 --------- -------- ................
-25,
500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)




R-25
10TT1r Pre-Built
5 ......................... ............ ..........................A s -B u ilt
08/1993
0 ---- ---4.............. ------- .... ---- ...... ............ ... 0 2 /1 9 9 4
--.02/1995
-5 .07/1997
---- 03/1998
*...02/1999
.................. ...............
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)
R-26
101
Pre-Built
5 As-Built..........
~ 08/1993
0 .... V T 4............. ............ ---------------------------0 2 /1 9 9 4
--02/1995
.5 -~--.-*07/1997
.' ....~03/1998
------- ...... 02/1999
>0 5 -------------...... ......................... .............------------- -----------2 ............ .......................... ..........----5 .------------ ..... .............
-30.L
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)




R-27

-35
0 500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

R-28

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

-10
0
> -15
a)

10
5
0 -5
S-10
0
> -15
-20
-25
-30

-35L
0




R-29

10 5
0
-5
a -100
> -15-20
-25
-30
-35
0
10 5
0
-5
"e -10
0
o
> -15
-20
-25
-30-

2500 3000 3500

R-30

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

500 1000 1500 2000
Offshore Distance (ft)

-35 L
0




R-31

105
0
-5
0
-10
-15
-20
-25
-30
0
10
5
0
-, -5
m -150-

2500 3000 3500

R-32

2500 3000 3500

500 1000 1500 2000
Offshore Distance (ft)

-30 I i
0 500 1000 1500 2000
Offshore Distance (ft)




R-33

0*r -10
-20
-25
-30
0
10
5
0
,-5
0 -10
-15
-20
-25
-30
0

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

500 1000 1500 2000 2500 3000 3500 4000
Offshore Distance (ft) R-34




R-35
10 T
Pre-Built As-Built
5 T .................................. ..................... ..................... ....... ..............
. ......... 08/1993
02/1994 0 -------- ........................................................ ....................................................... 0 2 /1 9 9 5
07/1997
---- 03/1998 02/1999
~-10
- 1 5 ................................. .. ......................... ......................... i......................... I ......................... ,. ............ ........
-20o-.-.------------------.---------.---------------. ........... ............. ......... .......................----25
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)
R-36
10 1 T
Pre-Built As-Built
55 .....................................---.--------------------------------.-------------------.------.------------------. --------.--008/199
...... 02/1994
0 ................................................................... ......................... .......................... . 0 2 /1 9 9 5
07/1997
--.-.. 03/1998
-... 02/1999
> -1 5 .................. ...... ........................ ........................... ................................................... .......................
-15 ."
-2 0 -..--------- .---------.- I..------------------- ....- ...... ................ Z .... ----------- ............ ......... ....................
-25
0 500 1000 1500 2000 2500 3000 3500
Offshore Distance (ft)




R-37

500 1000 1500 2000 2500 3000 3500 4000
Offshore Distance (ft) R-38

2500 3000 3500

10 5,
0

-15
-20
-25
0
10
5,
0
-5
g=- -5
0
(D-10

-25' 1 1 i 1
0 500 1000 1500 2000
Offshore Distance (ft)




R-39

0 500 1000 1500 2000 2500 3000 3500 4000
Offshore Distance (ft) R-40

500 1000 1500 2000
Offshore Distance (ft)

2500 3000 3500

-10
-15

-20 L
0




APPENDIX B
SHORELINE CHANGE RATES ON
ANNA MARIA KEY
(From Dean, R.G., et al., 1998)




Manatee County

Total Period of Record Recent Period
(1874-1986) (1974-1986)
Monument Shoreline Standard Number Shoreline Standard Number Number Change Deviation Of Change Deviation Of
Rate (t) Data Rate (t) Data
(fl/yr) Points (ftl/yr) Points

Passage Key Inlet

R-001 R-002 R-003 R-004 R-005
R-006 R-007 R-008 R-009 R-010
R-011 R-012 R-013 R-014

1.6 8.3
0.7 1.4 7.8
4.0 2.1
2.5 2.0 1.7
0.8
-0.1
-0.8
-1.2

14.9 153.8 297.2 191.4 118.4
261.6 221.6 113.1 55.0
44.7
46.3 43.7 47.4 51.9

2.8
21.2 7.6
14.2 7.3
27.2 16.2 1.1 1.5 0.8
0.9
-1.3
-1.2
-1.4

17.1
48.3 29.1 4.1
45.9 29.6 3.8
14.4 4.6
15.2 13.9 20.2 24.2




51.2 9 -4.1

R-016 R-017 R-018 R-019 R-020
R-021 R-022 R-023 R-024 R-025
R-026 R-027 R-028 R-029 R-030
R-031 R-032 R-033 R-034 R-035

-2.1
-2.2
-2.4
-1.9
-1.2
-2.2
-2.4
-1.8
-2.2
-1.7
-1.6
-1.2
-0.8
-1.6
-1.9
-3.2
-2.2
-3.6
-3.4
-4.4

45.0
40.8 33.1 33.5 39.5
21.7 13.5 12.9 22.1 30.9
42.2 40.6 21.8 27.0 41.6
49.2 95.4
70.9 125.8 112.6

-2.5
-0.4
-1.2
0.5
-0.5
-0.4
-1.9
-3.7
-1.7
-0.4
1.0
-0.3
-0.6
-0.4
1.1
0.3
-0.1
2.4
2.9 3.9

17.1 15.4 3.2
20.8 19.9

9.4 0.4 3.6 9.3
5.6

1.5 1.1 7.0 6.3
23.5

0.3 3.2 6.3
59.7
48.6

R-015 -2.0

21.2 4




R-036 -5.4 118.4 9 3.7 76.1 4
R-037 -6.3 118.1 8 6.5 51.9 3
R-038 -5.9 133.6 8 10.2 42.7 3
R-039 -5.4 152.0 9 7.1 39.0 4
R-040 -5.8 177.9 8 10.4 13.7 3
R-041 -4.7 223.6 9 -7.4 36.6 4
Longboat Pass