Citation
Original Version

Material Information

Title:
Original Version
Series Title:
Review of selected east coast Florida inlets Phase 1 : Sebastian Inlet, FL Evaluation of coastal processes and management practices and development o
Creator:
Dean, Robert G.
Place of Publication:
Gainesville, Fla.
Publisher:
Coastal & Oceanographic Engineering Dept. of Civil & Coastal Engineering, University of Florida
Publication Date:
Language:
English

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.

Full Text
UFL/COEL-2003/001

REVIEW OF SELECTED EAST COAST FLORIDA INLETS PHASE 1: SEBASTIAN INLET, FL EVALUATION OF COASTAL PROCESSES AND MANAGEMENT PRACTICES AND DEVELOPMENT OF RECOMMENDED MODIFICATIONS
by
Robert G. Dean

Submitted to:
Bureau of Beaches and Wetland Resources Department of Environmental Protection Tallahassee, FL 32399

January 20, 2003




REVIEW OF SELECTED EAST COAST
FLORIDA INLETS
PHASE 1: SEBASTIAN INLET, FL
EVALUATION OF COASTAL PROCESSES AND
MANAGEMENT PRACTICES AND
DEVELOPMENT OF RECOMMENDED MODIFICATIONS
January 20, 2003
Submitted to:
Bureau of Beaches and Wetland Resources Department of Environmental Protection
Tallahassee, FL 32399
Submitted by:
Department of Civil and Coastal Engineering
University of Florida
Gainesville, FL 32611 6590




EXECUTIVE SUMMARY
This report presents results of an investigation of the interaction of Sebastian Inlet (SI) with the adjacent beach and nearshore systems. Available survey data over the approximately 30,000 feet north and south of SI were analyzed to determine rates of volume and shoreline changes. Surveys of the sand trap, ebb tidal shoal, and back bay areas provided by the Sebastian Inlet Tax District (SITD) were analyzed. Additionally, 42 aerial photographs are provided as an appendix to provide a qualitative assessment of changes. In the analysis, it was found necessary to correct the offshore portion of the profile surveys that were conducted by fathometer, a fairly common problem/requirement in coastal engineering. A numerical! theoretical analysis was carried out to demonstrate the idealized interaction of a partial littoral barrier with the adjacent beach systems. A sediment budget framework was developed and applied to determine the appropriate nourishment quantities to balance the volume changes on the two sides of SI.
Various methods were applied to determine the changes north and south of SI. In general, for all methods applied and common periods, it was found that the volumes and shorelines increased north of SI relative to those south of the inlet. The available data allowed sediment budgets to be examined over two time frames: Winter 1999 to Winter 2002 and 1972 to Winter 2002. Application of the sediment budget principles established that over the period: Winter 1999 to Winter 2002, there has been an average annual deficit of nourishment of 56,800 yd 3/year. For the total period: 1972 to Winter 2002, there was an average annual nourishment deficit of 30,400 yd 3/year. These results are based on the consideration that the surveys (over 30,000 feet north and south of the inlet) have captured all volume changes. If inlet-induced erosion occurs south of the southerly survey limits, the appropriate nourishment requirements would be greater.
The analysis considers the possibility of onshore sediment transport and it is shown that it is not possible to quantify the sediment budget definitively. It is only the sum of the: (1) differences between the sediment inflows to and outflows from the region, and (2) the total onshore sediment transport that can be quantified. Example sediment budgets for the two time frames are presented for the case of balanced sediment inflows to and outflows from the region.
A significant result evident from the analysis is that there is substantial interannual variability in the net longshore sediment transport (littoral drift) of sand. In particular, from 1999 to 2002, the net longshore sediment transport was substantially greater than during the period 1972 to 2002. This result relates to appropriate sand management practices. In particular, since the magnitude of the interaction of SI with the adjacent beach systems depends on the net littoral drift, so do the appropriate remedial measures.
(Continued on Next Page)




EXECUTIVE SUMMARY
(Continued)
The results of the analysis carried out were developed into the following five recommendations: (1) Continuation and expansion of the semi-annual surveys, (2) Develo an agreed-upon basis for analyzing, interpreting and responding to the results of the data analysis,
(3) Analysis of the data as a bipartisan effort, (4) Consider extending the south jetty, and (5) Explore with the Florida State Division of Parks and Recreation, their position regarding the placement of various bypassing facilities located on the north jetty or on the beaches north of the north jetty.




TABLE OF CONTENTS
EXECUTIVE SUMMARY ..................................................... ii
LIST OF TABLES ............................................................ vi
LIST OF FIGURES .......................................................... vii
1. INTRODU CTION ........................................................... 1
2.13ACKGROUND ........................................................... 1
3. METHODOLOGY AND SCOPE .............................................. 3
3.1 Available Survey Data .................................................... 3
3.2 A erial Photographs ....................................................... 8
4. DATA SCREENING AND ADJUSTMENTS TO INDIVIDUAL PROFILE DATA ....... 8
4.1 Screening of Profile Data ................................................. 10
4.2 Corrections for Monument Relocations ...................................... 10
4.3 Correction for Lack of Profile Closure ...................................... 10
5. ANALYSIS AND PRESENTATION METHODOLOGY ........................... 15
5.1 G eneral ............................................................... 15
5.2 Individual Profile Analysis ............................................... 15
5.2.1 General Discussion ................................................ 15
5.2.2 Average Values to North and South of Sebastian Inlet ..................... 17
5.2.3 Average Profiles and Associated Volume Differences ..................... 17
5.3 Alongshore Shoreline and Volumetric Distributions of Change ................... 20
5.4 Analysis of Survey Data Through GIS Methodology ........................... 26
6. ANALYSIS RESULTS ...................................................... 27
6.1 Individual Profile Analysis ............................................... 27
6.1.1 Longshore Averages of Survey Results for Each Survey ................... 27
6. 1. 1.1 Average Shoreline Positions ................................... 28
6.1.1.2 Average Volumes ........................................... 28
6.1.1.3 Average Profiles and Associated Volumes ........................ 29
6.1.2 Alongshore Shoreline and Volumetric Distributions of Change .............. 29
6.1.2.1 Alongshore Distributions of Shoreline Change Rate ................ 29
6.1.2.1.1 Shoreline Change Rates: January 1999 to January 2002 ..... 29 6.1.2.1.2 Shoreline Change Rates: 1972 to January 2002 ............ 30
6.1.3 Alongshore Distributions of Volume Change Rate ........................ 30
6.1.3.1 Volume Change Rates: January 1999 to January 2002 ............... 30
6.1.3.2 Volume Change Rates: 1972 to January 2002 ..................... 30
6.2 GIS Analysis Results .................................................... 31
6.2.1 Sand Trap ........................................................ 31
6.2.2 Ebb Tidal Shoal ................................................... 31
6.2.3 B ack B ay ........................................................ 32
6.2.4 North (Brevard County) Beach and Offshore ............................ 32
6.2.5 South (Indian River County) Beach and Offshore ......................... 32
iv




7. THEORETICAL AND NUMERICAL SHORELINE CHANGES IN THE VICINITY OF A COMPLETE OR PARTIAL LITTORAL BARRIER ............... 34
7.1 Results Based on a Simple Theoretical Model ............................... 34
7.2 Results Based on a Numerical Model ...................................... 34
8. SUMMARY OF RESULTS ................................................. 35
9. SEDIMENT BUDGET CONSIDERATIONS ................................... 36
10. RECOMM ENDATIONS ................................................... 36
10.1 Continuation of Semi-Annual Monitoring .................................. 36
10.2 Develop an Agreed-Upon Basis for Analyzing and Responding to Results ........ 36 10.3 Analyze Data in a Bipartisan Effort ....................................... 38
10.4 Consider Extending the South Jetty at Sebastian Inlet ........................ 38
10.5 Initiate Discussions with State Division of Parks and Recreation Regarding
Their Position on Bypassing Equipment/Facilities ............................ 38
11. REFEREN CES ........................................................... 39
APPENDICES
A Historical Aerial Photos of Sebastian Inlet .................................... A-1
B Plots of Average Profiles for Brevard and Indian River Counties ................... B-1
C Sediment Interaction with Littoral Barriers and Inlets ............................ C-1
C. I Introduction ......................................................... C-2
C.2 Applications of Analytical Model to a Littoral Barrier ........................ C-3
C.2.1 Patterns of Updrift Shoreline Advancement and Downdrift
Shoreline Recession at a Littoral Barrier .............................. C-3
C.2.2 Patterns of Shoreline Change Rate and Longshore Sediment Transport ..... C-3 C.2.3 Bypassing Rates ................................................ C-3
C.3 Applications of Numerical Model ......................................... C-7
C.3.1 Shoreline Response to Constant and Oscillating Wave Directions .......... C-7
C.3.2 Volume Stored on Updrift Beach for Unidirectional and
. Oscillating W ave Directions ...................................... C-10
C.3.3 Effect of Sand Stored in Flood and/or Ebb Tidal Shoals ................. C-10
D Sediment Budget Considerations for Sebastian Inlet and Adjacent Beaches .......... D-1
D I Introduction ........................................................ D -2
D .2 M ethodology ....................................................... D-2
D.2.1 Sediment Budget for North Beach, Inlet and Offshore System ........... D-2
D.2.2 Sediment Budget for South Beach, Inlet and Offshore System ........... D-2
D.3 Determination of Appropriate Nourishment Quantities ....................... D-4
D.3.1 W inter 1999 to W inter 2002 ...................................... D-5
D.3.2 1972 to W inter 2002 ............................................ D-5
DA Further Sediment Budget Considerations ................................. D-6
D.4.1 W inter 1999 to W inter 2002 ...................................... D-7
D.4.2 1972 to W inter 2002 ............................................ D-7




LIST OF TABLES

Table Page
1 Chronology of Modifications/Activities in the Vicinity of Sebastian Inlet (Based
Substantially on Coastal Technology, 1987) ................................... 4
2 Summary of Survey Resources Provided by SITD .............................. 7
3 DEP Shoreline and Offshore Profile Data Analyzed in This Report ................. 8
4 Summary of Aerial Photographs Presented in Appendix A ........................ 9
5 Volumetric Error Due to One-inch Bias Error in Vertical Datum, GIS Analysis ...... 26
6 Summary of Rates of Average Shoreline and Volume Change Rates for
Various Time Frames for 30,000 feet North and South of Sebastian Inlet ........... 35
D. I Values and Their Sources for Two Time Periods Considered ................... D-6




LIST OF FIGURES

Figure Page
1 Sebastian Inlet, FL ................................................... 2
2 Individual Nourishment and Bypassing Events Onto the Beaches South of
Sebastian Inlet (Lower Panel) and the Cumulative of These Nourishment
and Bypassing Events (Upper Panel) ..................................... 6
3 Profile for Monument R-2 14, January 1999 to January 2002, Showing
Apparent Error in 2002 Survey......................................... 11
4 Profiles from Monument R-219 in Brevard County Showing Apparent
Errors Due to Different Azimuths ....................................... 11
5 Profiles from Monument R-2 in Indian River County Showing Noise in Data ........12 6 Geometry for Correcting for Monument Relocation.......................... 12
7 Illustration of Profiles Before (Panel a) and After (Panel b) Corrections for
Vertical Offsets. Corrections Applied from Approximately 5 feet Depth
Seaward. Monument R-204, Brevard County .............................. 13
8 Illustration of Profiles Before (Panel a) and After (Panel b) Corrections for
Vertical Offsets. Corrections Applied from Approximately 5 feet Depth
Seaward. Monument R-9, Indian River County............................. 14
9 Cumulative Differences Between Depths for Individual Surveys and the
January 2002 Survey. Monument R-204, Brevard County ...................... 16
10 Cumulative Differences Between Depths for Individual Surveys and the January 2002 Survey. Monument R-9, Indian River County ....................16
11 Average Shoreline Changes Over Approximately 30,000 feet North (Panel a) and South (Panel b) of Sebastian Inlet: a) Brevard County; b) Indian River County ...... 18 12 Volume Changes Over Approximately 30,000 feet Norhit (Panel a) and South (Panel b) of Sebastian Inlet: a) Brevard County; b) Indian River County ...........19
13 Comparison of 20 Averaged Common Profiles for 2000.09 and 2002.09 Survey Dates in Brevard County........................................ 21
vii




14 Comparison of 21 Averaged Common Profiles for 2000.09 and 2002.09 Survey Dates in Indian River County ....................................... 21
15 Shoreline Changes (Upper Panel) and Cumulative Shoreline Changes (Lower Panel).
January 1999 to January 2002 ............................................. 22
16 Shoreline Changes (Upper Panel) and Cumulative Shoreline Changes (Lower Panel).
1972 to January 2002 .................................................... 23
17 Volume Changes (Upper Panel) and Cumulative Volume Changes (Lower Panel).
January 1999 to January 2002 ............................................. 24
18 Volume Changes (Upper Panel) and Cumulative Volume Changes (Lower Panel).
1972 to January 2002 .................................................... 25
19 Sand Trap Sediment Volume Change Over Time (Relative to Winter 2002 Survey) ... 27 20 Ebb Shoal Volume Change With Time (Relative to Winter 2002 Survey Volume) .... 31 21 Back Bay Sediment Volume Change Over Time (Relative to Winter 2002 Survey V olum e) ........................................................ 32
22 Brevard County Outer Volume Changes to Approximate 20-foot Depth (Relative to Winter 2002 Survey Volume) ................................... 33
23 Indian River Outer Volume Changes to Approximate 20-foot Depth (Relative to Winter 2002 Survey Volume) ................................... 33
24 Example Sediment Budget for Two Time Periods. Transport Into and Out of Region Assumed to be the Same ........................................... 37
A.1 An Early but undated Photograph. Deposition Inside Inlet Forms a Nearly
Complete Blockage ................................................... A-2
A.2 Photograph of December 2, 1933 ........................................ A-2
A.3 Photograph on March 18, 1936 .......................................... A-3
A.4 Same Photograph Date as Figure A.3, But Showing Shoreline Farther to the North A-3 A.5 Photograph of February 14, 1943 ......................................... A-4
A.6 Photograph on February 24, 1943 ........................................ A-4




A.7 Photograph on October 25, 1948: New Southwest-Northeast Channel
Being Cut and Previous Channel Blocked by Dike ........................... A-5
A.8 Photograph on October 27, 1948, Bulldozer Working to Open New Inlet ......... A-5
A.9 Photograph on November 5, 1948, Nine Days after Photograph in Figure A.8,
North Jetty Now Visible ............................................... A-6
A.10 Photograph of November 15, 1948, Ten Days After Photograph in Figure A.9 ..... A-6 A.11 Photograph on December 19, 1948 ....................................... A-7
A. 12 Photograph on January 13, 1949 ......................................... A-7
A. 13 Photograph on July 11, 1949, Taken During Low Tide ........................ A-8
A. 14 Photograph on July 11, 1949, Note Bar Across Entrance ...................... A-8
A.15 Photograph on August 30, 1949 .......................................... A-9
A.16 Photograph on M arch 26, 1951 .......................................... A-9
A. 17 Photograph on March 26, 1951 (Same date as Figure A. 16, but showing
shoreline farther south) ............................................... A-10
A.18 Photograph on April 4, 1951 ........................................... A-1 I
A. 19 Photograph on April 24, 195 8 .......................................... A-1 1
A.20 Photograph on November 6, 1962 ....................................... A-12
A.21 Photograph on November 6, 1962 (Same date as in photograph of Figure A.20, but
showing a greater distance to the north) .................................. A-12
A.22 Photograph on January 31, 1963 (Showing substantial shoreline offset) ......... A-13
A.23 Photograph of March 25, 1968 ......................................... A-14
A.24 Photograph on January 12, 1970 ........................................ A-15
A.25 Photograph of February 13, 1970 ........................................ A-16
A.26 Photograph on December 29, 1970 ...................................... A-16




A.27 Photograph on February 13, 1974..................................... A-17
A.28 Photograph on May 13, 1974 ........................................ A-18
A.29 Photograph in 1976, Specific Date Unknown ............................. A-19
A.30 Photogrpahon January 11, 1978 ......................... I............. A-20
A.3 1 Photograph on February 28, 1980..................................... A-20
A.32 Photograph on January 30, 1981...................................... A-21
A.33 Photograph on January 1, 1983....................................... A-22
A.34 Photograph on May 10, 1984 ........................................ A-22
A.35 Photograph on February 13, 1985..................................... A-23
A.36 Photograph on April 18, 1986 ....................................... A-23
A.37 Photograph on February 25, 1988..................................... A-24
A.38 Photograph on January 5, 1989 ...................................... A-24
A.39 Photograph on January 17, 1992...................................... A-25
A.40 Photograph on March 10, 1993 ...................................... A-25
A.41 Photograph of Sebastian Inlet on June 18, 1998 ........................... A-26
A.42 Photograph of Sebastian Inlet on July 24, 1999........................... A-26
B. 1 Comparison of Average Profiles for Brevard and Indian River Counties,
January 1999 vs. January 2002 ........................................ B-2
B.2 Average Profile for Brevard County, July 1999 vs January 2002 ................B-3
B.3 Comparison of Average Profiles for Brevard and Indian River Counties,
January 2000 vs January 2002......................................... B-4
B.4 Average Profile for Brevard County, July 2000 vs. January 2002 ................B-5
B.5 Comparison of Average Profiles for Brevard and Indian River Counties,
January 2001 vs January 2002......................................... B-6
x




B.6 Comparison of Average Profiles for Brevard and Indian River Counties,
July 2001 vs January 2002 ............................................... B-7
C.1 Two Types of Littoral Barriers Addressed in This Appendix .................... C-2
C.2 Interaction of Littoral Barrier With Adjacent Shorelines (Analytical Model) ........ C-4 C.3 Alongshore Distributions of Shoreline Change Rate and Associated Transport ...... C-5 CA Bypassing Rate Around a Littoral Barrier for Two Time Periods ................. C-6
C.5 Oscillating Ambient Sediment Transport Due to Oscillating Deep Water
W ave D irection ....................................................... C-8
C.6 Average Shorelines for Constant Wave Direction ............................. C-8
C.7 Average Shoreline Positions for Oscillating Wave Directions ................... C-9
C.8 Maximum Shorelines Associated with Oscillating Wave Directions .............. C-9
C.9 Minimum Shoreline Displacements Associated With Oscillating
W ave D irections ...................................................... C-10
C.10 Sand Stored on Updrift Beach for Unidirectional and Oscillating
W ave D irections ...................................................... C-1 1
C.11 Average Shoreline Displacements for 20% of Potential Bypassed Sand
Stored in Flood and/or Ebb Tidal Shoals ................................... C-12
C. 12 Average Shoreline Displacements for 50% of Potential Bypassed Sand
Stored in Flood and/or Ebb Tidal Shoals ................................... C-12
D.1 Definition Sketch of Sebastian Inlet and Vicinity and Terminology
Used in Developing Sediment Budget ..................................... D-3
D.2 Example Sediment Budget for Two Time Periods ........................... D-9




REVIEW OF SELECTED EAST COAST
FLORIDA INLETS
PHASE 1: SEBASTIAN INLET, FL
EVALUATION OF COASTAL PROCESSES AND MANAGEMENT PRACTICES AND
DEVELOPMENT OF RECOMMENDED MODIFICATIONS
1. INTRODUCTION
The purpose of the study for which this report was conducted was to develop an understanding of the sediment flows in the vicinity of Sebastian Inlet (SI) and their interaction with SI and to develop this understanding into a sediment budget for SI. Based on these sediment budget considerations, recommendations for sand management at this inlet are presented.
2. BACKGROUND
Historically, inlets in the vicinity of modem-day SI have formed but were not stable over the long-term prior to extensive stabilization measures commencing in the late 1940's and early 1950's. Inlets were formed by storms, high water levels inside Indian River Lagoon or other processes and have resulted in migration and closure and are evidenced by the presence of relict flood tidal deposits inside the lagoon, see Figure 1. In 1886, local interests attempted to open an inlet; however, this opening was soon closed by a hurricane. Several similar efforts followed to open an inlet with similar results until the Sebastian Inlet Tax District (SITD) was formed by the Florida Legislature in 1919. The District designed an inlet located slightly north of the present inlet and construction commenced in 1924. The inlet channel was partially excavated when a hurricane completed opening the inlet in August 1924. Although this inlet required maintenance dredging, it remained open until 1942 when wartime fuel shortages limited maintenance dredging activities and the inlet was closed by a northeaster.
Sebastian Inlet was opened in its present position in 1948. Since that time, a combination of maintenance dredging, sand trap construction and operation and jetty modifications have resulted in a stable and navigable entrance. In 1955, the north jetty was extended 175 ft in a southwesterly (landward) direction and the south j etty was raised. Both j etties were extended southwesterly in 1959. In 1962, a channel was excavated with the following dimensions seaward of the bridge: 200 ft wide and 11I feet deep. Landward (east) of the bridge, the channel was 150 ft wide and 11 feet deep. The 1962 modifications included construction of a sand trap and the northwest channel was excavated. In 1963, the Coastal Engineering Laboratory (CEL) of the University of Florida was contracted to conduct a field and model study to develop recommendations that would improve navigation and reduce shoaling in the inlet (CEL, 1965; Chiu, 1966). The three main recommendations resulting from that study were: construction of a sand trap to impound sand entering the inlet on flood currents. This sand was to be later pumped to the downdrift (south)




.1 ., I I :1 I
0 1000
Scale (feet)

Figure 1. Sebastian Inlet, FL




beaches, a lengthening by 5 00 ft of the north jetty and a lengthening by 75 ft of the south jetty. These recommendations were later implemented (in 1970). More recently, (in the Fall of 1996 and in early 1997), approximately 200,000 cubic yards of compatible sand, excavated from an inland borrow pit, were placed a short distance south of the inlet. The suitability of this sand was evaluated by Parkinson (1995) who found that the sand "appears to be an acceptable source for beach nourishment." The mean diameter of the borrow sand was 0.28 mm. which was stated to be ''slightly finer than the sand from the feeder and control beaches."~
A chronology of construction and maintenance activities at Sebastian Inlet up through 200 1/2002 is provided in Table 1 including five nourishments since the 1996 placement. Figure 2 presents the individual beach nourishments and transfers from the sediment trap placed on the beaches south of the inlet since 1970 (Lower Panel) and the cumulative beach placement (Upper Panel). It is seen that a total nourishment volume of 1,340,000 yd 3 has been placed since 1978.
Appendix C presents analytical results describing the interaction of an idealized inlet with a beach and nearshore system along which a net longshore sediment transport occurs. These results are relevant to the interpretation of the results presented here and will be summarized in a later section of this report.
3. METHODOLOGY AND SCOPE
3.1 Available Survey Data
The primary data available for analysis include shoreline and profile data available in the DEP data base, surveys carried out in the vicinity of Sebastian Inlet under the auspices of the Sebastian Inlet Tax District (SITD) for the general purpose of quantifying the interaction of Sebastian Inlet
(SI) with the adjacent shorelines and aerial photographs. In addition to the surveys of the outer shorelines at the DEP monuments, the SITD data include surveys of the sediment trap, the ebb tidal shoal and back bay region. Subsequent to the Winter survey of 1999, the beach and offshore surveys extended approximately 30,000 feet north and south of SI; however, prior to that survey, these surveys extended variable distances north and south of SI, ranging from approximately 3,000 feet north in 1989 to 18,000 feet north in Summer 1998. To the south, these surveys extended from 10,000 feet in 1989 to 18,000 feet in the Summer 1998 survey. Thus, the analysis presented in this report of the outer survey data collected by the SITD is limited to the Winter 1999 to Winter 2002 surveys, although other survey data will be analyzed and reported.
Table 2 summarizes the extent of the survey data provided by the SITD which are available for analysis. The significance of the percentages in Table 2 will be described later. In addition to the SITD data, the data shown in Table 3 available from the Florida Department of Environmental Protection (FDEP) were analyzed in this study. Note that when semi-annual surveys were conducted, they are referred to by the SITD as "Winter" and "Sumnmer". For plotting and discussion purposes, these data are considered to have been collected in January and July, respectively.




Date Improvements/Activities
1886 First Cut Attempted by Hand
1895 First Cut Completed, Inlet Closed by Storm
1918 First Dredge Cut Completed, Inlet Closed by Northeaster
1919 Florida Legislature Establishes the Sebastian Inlet Tax District, a Special Tax
District With Responsibility to Maintain the Inlet 1923 Permit Obtained and Dredging Commences
1924 Inlet 100 ft Wide and 6 ft Deep Channel With rock jetties extending 400 ft
Offshore Completed
1939 Approximately 72,000 Cubic Yards of Sediment are Removed From Inlet at a
Cost of $ 6,000
1941/1942 Inlet Closed by Northeaster 1947 Approximately 70,000 Cubic Yards Dredged to Open an 8 ft deep by 100 ft
Wide Channel at a Cost of $ 35,000.
1948 Channel is Realigned to Modem-day Configuration. About 202,000 Cubic
Yards of Sand and 660 Cubic Yards of Rock removed at a Cost of $ 57,625.
1950 Maintenance Dredging Removes 140,840 Cubic Yards of Sand and 4,843 Cubic
Yards of Rock at a Cost of $ 38,000
1952 A 300 foot Extension of the North Jetty Was Completed at a Cost of $ 24,300.
Channel Dredging Removes 18,000 Cubic Yards of Sand at a Cost of $ 13,000. 1955 Maintenance dredging removes 60,000 cubic yards of material at a cost of $
15,580. Two newjetties are completed. The northietty was extended 250 feet
and the south jetty extended 175 feet.
1958 Maintenance Dredging removes 65,000 cubic yards
1962 Bridge construction commenced. Completed in 1965.

Table I
Chronology of Modifications/Activities in the Vicinity of Sebastian Inlet
(Based Substantially on Coastal Technology, 1987)




Table 1
Chronology of Modifications/Activities in the Vicinity of Sebastian Inlet
(Based Substantially on Coastal Technology, 1987) (Continued)

Date Improvements/Activities
1962 Channel dredging and sand trap excavation removes 282,400 cubic
yards at a cost of $ 247,138
1970 North and South jetty extensions completed
1972 New 37 acre sand trap excavation totaling 420,000 cubic yards
completed at a cost of $ 195,998
1978 765,500 cubic yards excavated from sand trap and 187,600 cubic yards
placed on downdrift beach at a cost of $ 599,900 1985/1986 133,290 cubic yards excavated from sand trap and 110,038 cubic yards
placed on downdrift beaches at a cost of $ 287,779. 1987/1988 Navigation channel located west of sand trap is excavated.
1989/1990 249,000 cubic yards of sand bypassed from sand trap
1992/1993 116,500 cubic yards of sand bypassed from sand trap
1996/1997 200,000 cubic yards of sand placed on downdrift beaches
1998/1999* Approximately 236,883 cubic yards of sand dredged from Inlet sand
trap and channel and placed between DNR monuments R-8 and R-10 1999* Approximately 50,000 cubic yards of sand trucked from an upland
source and placed between DNR monuments R-8 and R-10 2000* Approximately 50,000 cubic yards of sand trucked from an upland
source and placed between DNR monuments R-8 and R-10 2001* Approximately 64,250 cubic yards of sand trucked from an upland
source and placed between DNR monuments R-8 and R-9 2001/2002* Approximately 50,000 cubic yards of sand trucked from an upland
source and placed between DNR monuments R-8 and R-9
* This information provided by Dr. William Dally




0
*0
0 19)

300
0
S200
ca
0
a~100 (D
E

70

1980

1990
Year

(a) Nourishment Volumes
_..... .. LI......

2000

2010

-5 1970 1980 1990 2000 201
> Year
Figure 2. Individual Nourishment and Bypassing Events Onto the Beaches South of Sebastian Inlet (Lower Panel) and the Cumulative of These Nourishment and Bypassing Events (Upper Panel).

M Cumulative Volume Added
.......... ..................... .......... ..................... ......
.......... .......... ........... I ...... .. .........
.......... ......................... ...... ......... .........
. ...................................... ............................... .........
.................

0




Table 2
Summary of Survey Resources Provided by SITD

Date Ebb Shoal Sand Trap Back Bay North Beach South Beach
________Coverage (ft) Coverage (ft)
1989 50% 100% 85% 3,000 10,000
1990 40% 100% 85% 3,000 10,000
W 1991 50% 100% 90% 3,000 13,000
S 1991 70% 100% 90% 3,000 13,000
W 1992 80% 100% 90% 8,000 13,000
S 1992 95% 100% 95% 3,000 17,000
W 1993 35% 100% 95% 6,000 18,000
S 1993 95% 100% 85% 5,000 18,000
W 1994 85% 100% 85% 10,000 18,000
S 1994 85% 100% 95% 10,000 18,000
W 1995 60% 100% 90% 10,000 18,000
S 1995 100% 100% 90% 10,000 18,000
W 1996 95% 100% 90% 18,000 18,000
S 1996 100% 100% 100% 19,000 19,000
W 1997 95% 97% 100% 19,000 19,000
S 1997 95% 100% 100% 20,000 20,000
W 1998 95% 100% No Data 17,000 18,000
S 1998 95% 100% 100% 18,000 18,000
W 1999 95% 95% No Data 30,000 30,000
S 1999 98% 100% 100% 30,000 30,000
W 2000 100% 98% 95% 30,000 30,000
S 2000 95% 100% No Data 30,000 30,000
W 2001 97% 100% 95% 30,000 30,000
S 2001 100% 95% 90% 30,000 30,000
W 2002 1 97% 95% 97% 30,000 30,000




Table 3

DEP Shoreline and Offshore Profile Data Analyzed in This Report

Date County I Exten of Data Offshore Profile
__________________ Availability Availability
1972 Both, Coastal Complete Counties Every Third Profile
Construction Control Line
(CCCL) Survey ________1986 Both, (CCCL) Survey Complete Counties Every Third Profile
1997 Both Complete Counties None in Brevard County.
Every Profile in Indian
River County
3.2 Aerial Photographs
Appendix A provides a compilation of 42 historical aerial photographs of Sebastian Inlet. Most of these photographs were obtained from the Coastal and Oceanographic Engineering Archives at the University of Florida. These photographs provide semi-quantitative information regarding the interaction of Sebastian Inlet with the adjacent beaches and nearshore system.
Table 4 summarizes the aerial photographs included in Appendix A.
4. DATA SCREENING AND ADJUSTMENTS TO INDIVIDUAL PROFILE DATA
To ensure, to the degree possible, optimum results from the analysis of the individual profile data, the data were screened for obvious errors. In addition, as discussed in greater detail later, it was found necessary to adjust the profiles for the lack of offshore closure. This lack of closure is a common problem in data collected with a fathometer, especially with surveys for which the vertical datum was determined by a tide gage. In the vicinity of an inlet, the water surface is not horizontal at any time; rather the water surface is "warped" due to the water flows into and out of the inlet with the greatest overall spatial variations in water level occurring during periods of peak ebb and flood tidal currents. The tidal range can be small near the throat of the inlet and, depending on the hydraulic characteristics of the inlet, can be approximately one-half the ocean tidal range.




Table 4

Summary of Aerial Photographs Presented in Appendix A

FiueDate/Comments Figure 1Date/Comments 11 Figure IDate/Comments
A. 1 Undated Early A.15 August 30, 1949 A.29 1976, Specific Date
Photograph Unknown
A.2 Dec. 2, 1933 A.16 March 26, 1951 A.30 Jan. 11, 1978
A.3 March 18, 193 6 A. 17 March 26, 195 1, A.31 February 28, 1980
Different View
From Figure A. 16
A.4 March 18, 1936, A.18 April 14, 1951 A.32 January 30, 1981
Different View
From Figure A.4
A.5 February 14, 1943 A. 19 April 24, 1951 A.33 January 1, 1983
Inlet Blocked
A.6 February 24, 1943 A.20 Nov. 6, 1962 A.34 May 10, 1984
A.7 Oct. 25, 1948 A.21 Nov. 6, 1952, A.35 February 13, 1985
Different View
From Figure A.20
A.8 Oct. 27, 1948, A.22 January 31, 1963 A.36 April 18, 1986
Dredging New
Alignment_____________A.9 November 5, 1948 A.23 March 25, 1968 A.37 February 25, 1988
A.10 November 15, 1948 A.24 January 12, 1970 A.38 January 5, 1989
A. 11 Decemberl19, 1948 A.25 Feb. 13, 1970 A.39 January 17, 1992
A. 12 January 13, 1949 A.26 Dec. 29, 1970 A.40 March 10, 1993
A. 13 July 11, 1949, Date A.27 Feb. 14, 1974 A.41 June 18, 1998
__ _ M ay be in E rror 1 A 8 M y 3 97
A.14 July11, 1949 A2 Ma 3,94 A.42 July 24, 199




The data were screened to identify any obvious errors and, if appropriate means were evident to correct these errors, they were made. If not, the data were deleted from further analysis. Several examples will be presented to provide a flavor for the types of data requiring removal. An example is presented in Figure 3 for Profile R-214 in Brevard County where the 2002 survey appears to be quite anomalous from the other data for this profile. In this case, this survey was removed from further analysis. Figure 4 presents the various surveys at R-219, the southernmost monument in Brevard County. It is evident from these data that the azimuths of the various survey lines differed with some of the lines passing over the Sebastian Inlet north jetty whereas others were directed north of the jetty. This survey line was deleted from further analysis. Some of the data were characterized by rapid fluctuations, an example of which is shown in Figure 5 for Monument R-2 in Indian River County. These data were removed from further analysis.
An additional type of consideration that eliminated some data from further analysis was based on whether the survey track was too far from the specified track line. Specifically, those data collected more than 50 feet from the specified track line for distances less than 200 feet seaward from the monument were deleted and those data collected more than 200 feet from the track line for greater distances from the monument were removed from further analysis.
4.2 Corrections for Monument Relocations
In some cases, the monuments were relocated from their original positions within the time range of survey periods available. In these cases the post-relocation shoreline positions were adjusted by projecting all post-relocation survey lines onto an alignment parallel to the survey azimuth as illustrated in Figure 6.
4.3 Correction for Lack of Profile Closure
The profile data were analyzed to determine volume changes. Inspection of these data indicated considerable need to correct the data for failure of the profiles to "close" indicating datum problems. Figure 7a presents the ten profiles for survey line R 204 in Brevard County where the lack of offshore closure is evident. Figure 8a presents similar results for survey line R-9 in Indian River County.

4.1 Screening of Profile Data




2O
Brevard County R-214
1,2002.09
0
-2--
-30-

0 200 400 600 600 1000
Distance in Feet

1200 1400 1600

Figure 3. Profile for Monument R-214, January 1999 to January 2002, Showing Apparent Error in 2002 Survey.

Brevard County R-219
i
0 A I
10 -1 f I II II I
0
C
0-
.......

500 1000 1500 2000 2500
Distance in Feet

Figure 4. Profiles From Monument R-219 in Brevard County Showing Apparent Errors Due to Different Azimuths.

-2
-3

-4n'

4000

3000




z
20 0
0- 500 1000 1500 2000 2500 3000 3500 4000
Distance in Feet Figure 5. Profiles From Monument R-2 in Indian River County Showing Noise in Data.

Figure 6. Geometry for Correcting for Monument Relocation.

New Location

L
0

Original Location




0

I 1 ....2 I ~L...... I .....~L...... I ~ L....J..~..... I ~ I .....~L.....I I .........t I
~wv V4~~ Ahan

(mon)

01 I

111 t1W 4 W Xg
TiWWtOe in Nit

Figure 7. Illustration of Profiles Before (Panel a) and After (Panel b) Corrections for Vertical Offsets. Corrections Applied From Approximately 5 feet Depth Seaward. Monument R-204, Brevard County.
13

40
-20"
-40
(moil) ,Distance in Fed
Brevard Couny R-204 b) After Correction for Vertical Offset
20-
-40 "-
60
- - - - - - -

0.




Distance in Feet

40O
Indian River County R-9 b) After Correction for Vertical Offset
20
- -- -- -- -- -- -----------or-
-20 -------------------------------------------c........................................................
-40.

,0 1000 Ditn neet0 2500
Distance in Feet

3000 350D 4000

Figure 8. Illustration of Profiles Before (Panel a) and After (Panel b) Corrections for Vertical Offsets. Corrections Applied From Approximately 5 feet Depth Seaward. Monument R-9, Indian River County.
14

(m'bn)




In extracting volume change information from subsequent profiles, each of which may contain errors, the objective is to obtain the most relevant results possible. If the case of interest here, if the profiles are not corrected and the analysis is terminated landward of the closure depth, errors will result due to not capturing the full changes that have occurred. If the profiles are analyzed over their full length and closure errors exist, the farther the analysis is conducted, the greater the non-closure error. Fortunately, non-closure or other survey errors are not cumulative from survey to survey; however, they appear in the analyzed data as undesirable "noise" and thus detract from interpretation of the results.
The approach to reducing the non-closure error was to select, for each monument, one of the available surveys as a "reference survey". We have selected the January 2002 survey for the reference. The cumulative differences between each of the remaining profiles and the reference profile were calculated as a function of seaward distance for depths greater than approximately 20 feet as shown in Figure 9 for Profile R-204 in Brevard County and Figure 10 for Profile R-9 in Indian River County. If the cumulative differences between the two profiles were due to closure errors, the seaward portion of this curve would change linearly with seaward distance and the slope of this line would be equal to the relative closure error. The slopes of these lines were determined by a least squares procedure and represent the vertical difference between these offshore portions of these two profiles. The profiles were adjusted by the slope of these lines for water depths greater than 5 feet. Figures 7b and 8b illustrate the adjusted profiles for Profiles at monuments R-204 and R-9 in Brevard and Indian River Counties, respectively. The improvement in profile closure is evident from inspection of these figures.
5. ANALYSIS AND PRESENTATION METHODOLOGY
5.1 General
Results were developed through analysis of both the individual profiles as described in Section 4 and the general survey data without correcting the individual profiles, the latter accomplished through ArcView 3.2a Geographic Information System (GIS) methodology. The results of each of these will be presented separately.
5.2 Individual Profile Analysis
5.2.1 General Discussion
In developing a quantitative understanding of the effects of SI on the adjacent shorelines, one primary interest is in the volume changes. However, as discussed in the preceding section, interpretation of volume changes can be difficult due to the uncertainties in vertical datums in those portions of the profiles that were measured by fathometer and, in some cases, gaps in the profiles between the portions measured by fathometer and those measured by land based procedures. Additionally, if placed sediments are of different sizes than the native, the usual relationship between volumes and shoreline changes may not apply. However, with substantial amounts of survey data available, it is likely that the overall results will be reasonably correct




320
Brevard CountyR-204 1600
o -. =-comi-=

~1

1000

1500

2000

2500

3000

Distance in Feet From Approximate 20 Ft Depth Contour. Figure 9. Cumulative Differences Between Depths for Individual Surveys and the
January 2002 Survey. Monument R-204, Brevard County.
,3 3200
Indian River County R-9
S1600
S
0
0.500 1000 1600 2009 2500 3000.
Distance in Feet From Approximnate 20 Ft Depth Contour. Figure 10. Cumulative Differences Between Depths for Individual Surveys and the January 2002 Survey. Monument R-9, Indian River County.

I at%^ -




even with substantial errors present in individual profiles and perhaps particular surveys. The desirability of quantification of the effect through volume changes is that shoreline changes can occur without changes in volumes. Shorelines change on a seasonal basis with magnitudes which, on the east coast of Florida, are believed to average approximately 15 feet. Additional greater shoreline changes can occur due to a series of storms and/or major hurricanes. Fortunately, in some of the data sets, the shorelines were measured in both Brevard and Indian River Counties during approximately the same seasons and thus the effects of seasonal or storminduced shoreline changes should be approximately the same on the two sides of the inlet. The shoreline and profile data required different procedures and precautions as described separately in the following sections.
Because the results of the shoreline and profile data analyses were to some degree surprising, these data were subjected to more analysis than would normally be the case. The details and some of the analyses results are presented in various appendices for completeness and the sections below simply present a brief discussion of the methods and illustration of some of the associated results.
Three types of analyses were conducted for the shorelines and volumes: (1) Average summary values to the north and south of SI, (2) Average profiles and associated volumes for each survey period relative to the 2002 survey, and (3) Best least squares rates of change versus longshore distance and the cumulative rates of change versus distance from SI. The rationale for and significance of these results will become apparent as they are presented.
5.2.2 Average Values to North and South of Sebastian Inlet
This type of analysis simply averages all values of the variable (shoreline positions or volumes) under consideration for each particular survey date using only commonly available monuments for each survey date. The values are averaged separately for the monuments north and south of SI. These average results will be presented relative to the latest survey (January 2002). Figures 11 and 12 present the average shorelines and volumes, respectively. For Brevard County, a total of 20 monuments (of a potential 3 1) were common and considered of good quality. For Indian River County, 21 (of a potential 30) monuments qualified. The results presented in these figures will be discussed later in this report.
5.2.3 Average Profiles and Associated Volume Differences
The procedure for calculating average profiles is as follows. For the 2002 survey, the distance from the NGVD elevation on the profile to the monument was determined for each monument. This "offset" value was subtracted from each cross-shore location such that the horizontal location of the NGVD elevation of each profile was zero for the 2002 survey. For every other survey, those monuments were selected for which valid surveys were common to the 2002 survey. For these selected profiles, for each survey location, the 2002 offset was subtracted from each horizontal location such that if there were no changes, the two profiles would be identical. For the two survey dates (2002 and the date under consideration) all common profiles for a




-41
to
V 0
V
C
o -10
co
"-20 ..

Time in Years a) Brevard County

-- 20
. 10
0
0
10
0 97
197

1980 1990 2000

2010

Time in Years b) Indian River County Figure 11. Average Shoreline Changes Over Approximately 30,000
feet North (Panel a) and South (Panel b) of Sebastian Inlet.
18




0.
0
I-.
V

9nr

1970

1980

1990

2000

2010

Time in Years a) Brevard County

Time in Years

b) Indian River County
Figure 12. Volume Changes Over Approximately 30,000 feet
North (Panel a) and South (Panel b) of Sebastian Inlet.
19




particular date were averaged. The volume differences and MHW shoreline displacements relative to the 2002 profile were calculated. The average profiles determined for January 2000 and January 2002 as described above, are presented in Figures 13 and 14, for Brevard County and Indian River County, respectively. Appendix B presents averaged profiles for all dates for which the data were adequate.
5.3 Alongshore Shoreline and Volumetric Distributions of Change
This type of results includes both the alongshore distributions of shoreline and volumetric change and the alongshore cumulative distributions of shoreline and volumetric change. These results were developed as follows. First, the value (shoreline or volume) was determined for each survey date for each monument. Second, the best least squares slope was determined for each monument for the time range selected for the particular analysis. These slopes represent the rate of change of the particular variable (shoreline or volume) at that monument. These least squares slopes were obtained for various time periods. Finally, these slopes were integrated (summed) away from SI in accordance with Eq. (1) below to provide the cumulative rate of change for the variable over the available distances on either side of the inlet. The equations for determining the cumulative changes are:
u J-1 y A
CumS(xj,,)=0.5Z{(.Y)1 1+(LJ .+ }~ fAxj
and (1)
CumN(xj ')=-0"5' ,(AY ( At).,I ,
IY At)~ AtitJ
in which the summations, CumS(xj+ ) and CumN(x,+l) represent the summed values to the south and north sides of the inlet, respectively, thus representing the net beach plan area (or volume) change cumulated (if Cum is positive) or net beach plan area (or volume) lost (if Cum (x) is negative) up to the location, xj l. The terms xj 1 and Axi represent the location of the (j+l)th survey line relative to the inlet and the longshore distance between the jth and (j+1)th survey lines, respectively. This type of plot is useful because it yields a net area (or volume) change up to the point (x) of interest. Figure 15 presents the shoreline changes and cumulative shoreline changes, respectively for the period January 1999 to January 2002 and Figure 16 presents the same results for the period 1972 to January 2002. Figures 17 and 18 present the same information for the volume changes. The changes at each monument are presented in the upper panels of these figures and the lower panels present the cumulative change results. Inspecting the lower panel of Figure 15, it is seen that south of SI, the cumulative shoreline change rates decrease to approximately




10
S2002.09
0 "
2000.09
-20 .. .. .

Distance in Feet Figure 13. Comparison of 20 Averaged Common Profiles for 2000.09 and 2002.09 Survey
Dates in Brevard County.

1U
0
- -2002.09
-10
2000.09
-32^ ^

100U

Distance in Feet Figure 14. Comparison of 21 Averaged Common Profiles for 2000.09 and 2002.09 Survey
Dates in Indian River County.

0
.2

z
.U.

800 1000

1200

-00

120

140

-A




Y

.- Brvard CoitAty I Indian River County.
Monument Locations Alonguphore

x
. O 10.000ft:
..z" .'l" 'I, i ""'' ', !"' 1 "I '. I ..
- Ioumnt Locations-Alonso.
* .4.
Figure 15. Shoreline Changes (Upper Panel) and Cumulative Shoreline
Changes (Lower Panel). January 1999 to January 2002.
*Cl ty -I4 Cont -:
Monaumnt Locaans.Aionghor.".
Figure 15. Shoreline Changes (Upper Panel) and Cumulative Shoreline
Changes (Lower Panel). January 1999 to January 2002.




5
4)
2
0
02

-~. . . . .I I

o to 0 to 0 It
IM CD 0 0
C O COI COj Cq 02

-4 It) 0 It) 0
I I 02
CO ~ I I I
CO CO ~

- Brevard County >'<"-- Indian River County
Monument Locations Alongshore

I I I I I I

-I It) 0 It) 0 10 0 I I -4 .02 02 0)
CO CO I I I I
CO CO CO CO CO

-- Brevard County : :- Indian River County
Monument Locations Alongshore
Figure 16. Shoreline Changes (Upper Panel) and Cumulative Shoreline
Changes (Lower Panel). 1972 to January 2002.

Scale
0 10,000ft.-
V7
027

V') 0
02 0
1 1
Cd 0:

*n

0
0
10
0 2

-4
4)
0
0
0
0
.0
4) 02

Scale:Distance
0 10,000ft




4U
00
-20
UL
S-207
Scale
0 10,000ft
-40
0 20 to 0 to 0 IL) 0
-. '1 I 1 N" 1 I I1 1 1 1 *
Brevard County. b': Indian River County --->'
Monument Locations Alongshore
(a) Volume Rate Changes for Last Seven Surveys. To 20 feet.
V . .I .

0
0
0
0
x
I
N
C.)
~ 10 4)
N
4,
0 4)
U 4,
0

Scale
. O 10.ooft
2 W 7 Y I ,
h.- Brevard County > : Indian River County'
Monument Locatlons Alongshore
(b) Cumulative Volume Rate Changes for Last Seven Surveys.
To 20 feet.
Figure 17. Volume Changes (Upper Panel) and Cumulative Volume
Changes (Lower Panel). January 1999 to January 2002.

C: W)




I.
20
0
3
-20 8 I-20
0

o ~ 0 U) 0 Lo O 0 to 0
o o 0 0 .. - I .- N1
I I I I I I I I
Brevard County F- Indian River County amb
Monument Locations Alongshore

Figure 18. Volume Changes (Upper Panel) and Cumulative Volume Changes (Lower Panel). 1972 to January 2002.

Scale:Distance
0. 10,0oft
- NZ NZ NZ N r I I I I
S I I .I I I "I' I I ".
Brevard County Indian River County -->j
Monument Locations Alongshore

0
o 140
N,
120 S100
0
S60 S40 20
0
-20




- 9,000 ftl/year at approximately survey line R 5 and then increase to approximately 0 at R-20 and remain at approximately 0 to Monument R-30. North of SI, the areas increase more or less monotonically, reaching a value of approximately 105,000 ft2/year at survey line R-189 in Brevard County. Referring to Figure 17 for volume changes for the period January 1999 to January 2002, it is seen that south of SI, the cumulative volumes first decrease slightly, then increase reaching a maximum of approximately + 55,000 yd3/year at survey line R 16, decrease slightly, then increase to approximately 85,000 yd3/year. On the updrift (north) side of SI, at the limits of the available data, the volumes have increased to approximately 155,000 yd3/year.
5.4 Analysis of Survey Data Through GIS Methodology
Table 2 summarizes the data provided by the SITD. In addition to the individual profile data as described in the preceding section, other data were analyzed by GIS methodology through the commercial program ArcView 3.2a. The individual surveys of a feature (for example, the ebb tidal shoal) did not encompass the same geographical area for each survey. Thus, in analyzing these data, horizontal areas were established which corresponded reasonably with most individual surveys such that the volumes would represent the same plan areas. In establishing the areas to represent the individual features, there is a trade off in establishing an area that is so small that the areas contain all of the surveys; areas defined in this manner would be too small to represent the changes of interest. If the defined areas are too large, considerable extrapolation of the survey results beyond the physical measurements is required for some surveys to represent volumes within the defined area. ArcView develops a Triangular Integrated Network (TIN) which represents the surface associated with the individual surveyed area within the defined plan area. The volumes within that area are also calculated by ArcView and the plan area for which the TIN is considered reliable for volume calculation. The calculated volumes are proportioned by the defined area and the plan area for which the volumes are calculated to determine the reported volumes.
The volumetric errors that result due to vertical datum errors has been discussed previously. Table 5 presents the nominal volume error for each of the features resulting from one inch of vertical bias error.
Table 5
Volumetric Error Due to One Inch Bias Error in Vertical Datum, GIS Analysis
Feature
Sand Trap Ebb Shoal Back Bay North Beach South Beach
Error (yd') 12000 45000 32000 71000 101000




In calculating the volumes for the north and south beaches, the offshore limits were taken to be the approximate 20 foot depth contour.
The presentation methodology for the GIS results is simply to plot the volumes for the individual features relative to the Winter 2002 volume for that feature. Figure 19 presents these results for the sand trap.

1987 1989 1991 1993 1995
Year

1997 1999 2001 2003

Figure 19. Sand Trap Sediment Volume Change Over Time.
(Relative to Winter 2002 Survey)
6. ANALYSIS RESULTS 6.1 Individual Profile Analysis
6.1.1 Longshore Averages of Survey Results For Each Survey
These results present the simple longshore averages for the various surveys and are presented in the following two sections. As will be evident from the results, the positions and volumes are presented with respect to those of the latest survey results (January 2002).

400000 300000
.~200000
*0 100000 cc 0
-100000

-200000 ~1985




6.1.1.1 Average Shoreline Positions

The shoreline positions averaged for the ten survey dates have been presented in Figures 11I a and
1 lb for Brevard and Indian River Counties, respectively. As noted, for Brevard County, 20 monuments from the potential 31 and for Indian River County, 21 monuments from the potential 30 were included in the analysis.
The shoreline positions for Brevard County (Figure I11 a) show that there was a substantial shoreline advance from 1972 to 1986, a moderate decrease from 1986 to 1997 and a very steep increase from January 1999 to January 2002,. Overall during this 30 year period, the shoreline experienced a net increase of approximately 30 feet or 0.9 feet per year. The least squares best fit shoreline change for the entire period is 0.68 feet per year and for 1999 to 2002, the best least squares fit is 4.3 feet per year.
The average shoreline positions for Indian River County (Figure 11I b) show a substantial decrease from 1972 to January 1999 followed by an increase to January 2001 and then a decrease to January 2002. Overall during this 30 year period, the shoreline experienced a net decrease of approximately 19 feet or 0.63 feet per year. The least squares best fit shoreline change for the entire period is 0.5 feet per year and for the period 1999 to 2002, the best least squares fit is + 1.7 feet per year.
6.1.1.2 Average Volumes
The average volumes to an approximate depth of 20 feet were averaged and have been presented in Figures 12a and 12b for Brevard and Indian River Counties, respectively. It is noted that the 1972 and 1986 surveys were conducted every third monument which precluded averages of the type presented here. Also, the 1997 survey in Brevard County was conducted every third monument; however the 1997 survey in Indian River County was conducted at every monument.
The average volumes for Brevard County show similarities to the shoreline changes presented and discussed earlier for the period January 1999 to January 2002. Overall, there was an increase of approximately 12 yd3/foot/year over the 3 year period represented or approximately 3.9 yd 3/foot/year. The best least squares fit from January 1999 to January 2002 is + 4.4 yd 3/foot/year. The average volumes for Indian River County, presented in Figure 12b again mirror the shoreline changes and show a decrease from 1997 to January 1999, followed by an increase from January 1999 to January 2001, following which the volumes decrease to July 2001 then increase to January 2002. Overall, there was an increase of approximately 9 yd 3/foot over the 3 year period represented or approximately 3 yd3/foot/year. The best least squares fit from January 1999 to January 2002 is + 2.8 yd 3/foot/year.




6.1.1.3 Average Profiles and Associated Volumes

The results presented here are the average profiles for various time periods compared with the 2002 average profiles. All of the dates for which adequate data are available are presented in Appendix B. In the present section, only results comparing average profiles for January 2000 and January 2002 are presented and discussed.
Figure 13 has presented an example of the averaged profile results for January 2000 and January 2002 for Brevard County. For this case, there were 20 profiles that were common for these two dates. It is apparent that there is more volume present in the 2002.09 profile than in the 2000.09 profile. Integration of the profile differences out to a depth of 20 feet yields a volume difference of + 11.09 yd3/foot or 5.5 yd3/foot/year for the 2 years between the two surveys. This amounts to 165,000 yd3/year for the entire 30,000 feet length encompassed by the profiles. The differences between the two MHW shorelines is + 10.4 feet or + 5.7 feet/year for this 2 year intersurvey period. This amounts to an area increase rate of + 171,000 ft2/year for the approximately 30,000 shoreline segment.
Figure 14 has presented an example of the averaged profile results for January 2000 and January 2002 for Indian River County. For this case, there were 21 profiles that were common for these two dates. The volume changes between these two average profiles is + 6.46 yd3 /foot or 3.23 yd3/foot/year for this 2 year period. This amounts to + 96,900 yd3/year for the entire 30,000 feet length encompassed by the profiles. The differences between the two MHW shorelines is + 2.04 feet or + 1.02 feet/year for this 2 year intersurvey period. This amounts to + 30,600 ft2 for the approximately 30,000 foot shoreline segment.
6.1.2 Alongshore Shoreline and Volumetric Distributions of Change
6.1.2.1 Alongshore Distributions of Shoreline Change Rate
6.1.2.1.1 Shoreline Change Rates: January 1999 to January 2002
Figure 15 has presented the alongshore distribution of change for the shorelines and the cumulative alongshore distributions of shoreline change for the period 1999.09 to 2002.09, respectively. These results were discussed earlier. Referring to the upper panel of Figure 15, it is seen that the shoreline change rates on the updrift (Brevard County) side are mostly positive reflecting advancement whereas those on the downdrift (Indian River County) side are both positive and negative reflecting both shoreline advancement and recession. These results are what we would refer to as "noisy" in the sense that it is not a smooth distribution. There are several possible reasons including beach nourishment, sand waves and various other shoreline features that are known to occur. It is seen that at the updrift limit of the surveys (Brevard County), the value is approximately 105,000 ft2/year which averages to 3.5 feet/year over the approximately 30,000 feet survey distance and the three year time interval represented by the surveys.




At the downdrift limit of the surveys, the cumulative shoreline change rate is approximately zero meaning that there is approximately as much shoreline recession as advancement in this 30,000 feet distance. This is to be compared with the results computed from Figure I1 b which also showed that for this period in Indian River County the average shoreline change was + 4 feet or +
1.3 feet per year.
6.1.2.1.2 Shoreline Change Rates: 1972 to January 2002
These results are presented in Figure 16 and, in general, show considerably lower shoreline advancement rates than for the period January 1999 to January 2002. Updrift of SI, the average shoreline changes are approximately 0.4 feet per year whereas downdrift of SI, the average rate is recession at approximately 0.3 feet per year based on least squares analysis.
6.1.3 Alongshore Distributions of Volume Change Rate
6.1.3.1 Volume Change Rates: January 1999 to January 2002
Figure 17 presented the alongshore distribution of volumetric changes and the cumulative alongshore distributions of volumetric change for the period 1999.09 to 2002.09. It is seen that the volumetric change rates on the updrift (Brevard County) side are mostly positive reflecting advancement whereas those on the downdrift (Indian River County) side are both negative and positive reflecting both accretion and erosion, although positive on average. Again there are several possible natural and human-induced causes of the noiseness apparent in these results, including "sand waves" which are large "pulses" of sand moving along the shoreline and which are poorly understood, the interaction of the inlet and jetties with changes in wave direction and certainly the effects of the various nourishments on the downdrift side of SI. It is seen that at the updrift limit of the surveys (Brevard County), the value is approximately 155,000 yd3/year which averages to 5.2 yd3/foot/year over the approximately 30,000 feet survey distance and 3 year period. This can be compared with the values shown in Figure 12a (4.4 yd3/foot/year) based on a least squares fit to the averages from common monuments.
At the downdrift limit of the surveys, the cumulative volumetric change rate is approximately 85,000 yd3/year which averages to + 2.7 yd3/foot/year over the approximate 30,000 feet distance and time encompassed by these surveys. This can be compared with the values shown in Figure 12b (2.83 yd3/foot/year) based on a least squares fit to the averages from common monuments.
6.1.3.2 Volume Change Rates: 1972 to January 2002
The results for this period are shown in Figure 18. As was the case for the shorelines, the change rates are considerably smaller than they were for the January 1999 to January 2002 period. At the updrift limit of the surveys (Brevard County), the value is approximately 120,000 yd3/year which averages to 4.0 yd3/foot/year over the approximately 30,000 feet survey distance represented by this figure.




At the downdrift limit of the surveys, the cumulative volumetric change rate is approximately 20,000 yd3/year which averages to 0.67 yd3/foot/year over the approximate 30,000 feet distance encompassed by these surveys.
6.2 GIS Analysis Results
6.2.1 Sand Trap
Figure 19 has presented the differences of volumes in the sand trap relative to the Winter 2002 survey. It is seen that there is an apparent error in the Winter 1998 results which could not be resolved. The remainder of the results are reasonable. The volumes removed by dredging in 1989/1990, 1992/1993 and 1998/1 999 are evident in the data as are the accumulations following the dredging events. These results demonstrate that the deeper the trap, the greater the rate that sand is induced to deposit in the trap. There is a trade off in dredging the trap since, to an unknown degree, the deeper the trap, the more sand is drawn into the trap and the less sand is bypassed on the ebb tidal shoal.
6.2.2 Ebb Tidal Shoal
Figure 20 presents volume changes for the ebb tidal shoal in the same format as for the sand trap. The trend is toward generally increasing volumes with time. The noise in the data precludes identifying any relationship between the volume changes in the ebb tidal shoal and sand trap.

600000
400000 200000
0
-200000
-400000
-600000

1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 Year
Figure 20. Ebb Shoal Volume Change With Time (Relative to Winter 2002 Survey Volume)

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




6.2.3 Back Bay
Figure 21 presents the volumes in the back bay area relative to the Winter 2002 survey value. It appears that, in addition to the substantial volume fluctuations, there is a trend of increasing volumes commencing in approximately 1997/1998.
100000
0
- 100000
-200000 .... ..
-3000001985 1987 1989 1991 1993 1995 1997 1999 2001 2003 Year
Figure 21. Back Bay Sediment Volume Change Over Time (Relative to Winter 2002 Survey Volume)
6.2.4 North (Brevard County) Beach and Offshore Figure 22 presents the volumes relative to the Winter 2002 values. The sand volumes above NGVD, below NGVD out to the approximate 20 foot depth and the total of these two volume representations are presented. It is seen that there is an increasing trend with time. The best least squares line is included in this figure and has a slope of + 166,000 yd3/year. It is of interest that for most years, the volumes are less during the Winter surveys.
6.2.5 South (Indian River County) Beach and Offshore Figure 23 presents the volumes relative to the Winter 2002 values. The results in this figure are in the same form as for Figure 22. The data for Winter 1999 were not of adequate quality for this analysis. The best least squares line is included in this figure and has a slope of + 57,000 yd 3/year.




1000000 800000 600000 400000 U/)
E 200000
60
M -200000
-400000 I -600000
-800000 -1000000
199

2000

2001 Year

2002

2003

Figure 22. Brevard County Outer Volume Changes to Approximate 20 foot Depth.
(Relative to Winter 2002 Survey Volume)

1000000
800000 600000
400000 200000
0
-200000
-400000
-600000
-800000
-1000000
19

'99

2000

2001

2002

Year
Figure 23. Indian River Outer Volume Changes to Approximate 20 foot Depth
(Relative to Winter 2002 Survey Volumes)

. . .. . . . ... .. . . . . . . . . . . . . . . . . .
Volumes Above NGVD
......... Volumes Below NGVD
Total Volumes
- -- Least Squares Fit to Total .. .. ... . . . ... .. ,. . . . . . ..... ..... . : . .. .. .. . ... .. .. .... .. . ... .. .. .. ..
. . . . . . . . -7. . .... ... .' . . . ... ' .... . !. . .... . . . .
. .... .... ..... . .. .... ..... ..... .... . . ... ... ..-- ;
',. ... . .:." .. . ..-. . ..r :
- . . . . . . . . . .. .. .. ... . : > . . . . . . . . . . . . .
. ..4 / ": ".. : . .........
. ,. . .. . .. .. ,, . :;... . . . :.. .. . ............ .. .. .. .. : . . .. .. .. . .. .. .. . .
Best Least Suares Slope
..... ...... ....... .. ... + 166,000 yd l -year... ..

. . . \ .. . .. . . . ..
:i
. .. .. .. .... Volumes Above NGVD
Volumes Below NGVD
.. .- "--"-- Total Volumes
...... .... .. i. .. ..i.- ...." \. ... oa
k ------- Least Squares Fit to Total
. . . ... . .. . . .... .. . . . .:. .. . . .... . . . . . . ..". . . . . . . : . . . . . .
. . . . . . . . . . .: . . .. ... . . ... . . : . . ... . .. . . . . . .. .. . . . ..
i . . . -:. .-.-. ... ..". ..' .'.
q .. .. .. ... .. . .
. . .: . . .. . i i . . .. . : . . . : .'. . ... , . . . . . . . . . . .. .
. . . . .. .. . . . . . . .
................. I.......... .Best-Least Squares-Slope
. ... . . ". "" . . . . ." . . . . . . ... . .. . ... . . . : . . . . . ..
. . . .. . . .... . . . . . . . ... . . . . . . .. . . . . . . . . .,.. . . . . . - -

2003

99




7. THEORETICAL AND NUMERICAL SHORELINE CHANGES IN THE VICINITY OF A COMPLETE OR PARTIAL LITTORAL BARRIER
A substantial body of theory exists which can assist in the general understanding and interpretation of the interaction of a littoral barrier with the updrift and downdrift beach and nearshore systems. The sections below summarize the results which are presented in greater detail in Appendix C. In general, results are presented for wave conditions resulting in a net longshore sediment transport of 260,000 yda/year and for a barrier length of 500 feet.
7.1 Results Based on a Simple Theoretical Model
It is shown that, according to this idealized theory, the patterns of shoreline advancement on the updrift side of the barrier and shoreline recession on the downdrift side of the barrier are antisymmetric. That is, at equal distances from the barrier, the shoreline advancement on the updrift side of the barrier is equal to the shoreline recession on the downdrift side of the barrier. Initially, the barrier acts to completely block the longshore sediment transport; however, for the conditions selected, bypassing commences after a period slightly in excess of 10 years. Bypassing is never complete and after a period of 100 years, the bypassing rate is only 77% of the net longshore sediment transport. As time progresses, the updrift distance affected by the barrier increases such that after 10 and 50 years, the effect of the barrier is felt some 3 and 8 miles, respectively updrift and downdrift of the barrier.
7.2 Results Based on a Numerical Model
Advantages of a numerical model include the capability to represent more complex wave and geometric conditions than allowed by the simple analytical model. Two issues were investigated with the numerical model that could not be represented by the theory discussed in the previous section: (1) The effects of an oscillating wave direction, and (2) Effects of sediment stored on the flood and/or ebb tidal shoals. Results are summarized below.
The effects of oscillating wave direction are to cause fluctuations on the two sides of the barrier and to decrease slightly the volumes of sand impounded and eroded on the updrift and downdrift sides of the barrier, respectively.
As expected, with sand deposited on the ebb and/or flood tidal shoals, the shoreline change patterns on the two sides of the barrier are not antisymmetric and greater erosion occurs on the downdrift side than accumulation on the updrift side.




8. SUMMARY OF RESULTS

The overall results of the analysis presented herein are summarized in Table 6. It is seen that, in general even with the nourishment placed on the south beaches, the beaches to the north of Sebastian Inlet have experienced more volumetric accumulation and shoreline advancement than the beaches to the south. This is the case for all periods examined. Although these results demonstrate some inconsistencies, when compared on a common basis, this assessment of volume and shoreline changes hold.
Table 6
Summary of Rates of Average Shoreline and Volume Change Rates for Various Time Frames for 30,000 feet North and South of Sebastian Inlet
Rate of Average Rate of Average Volume Volume Placed on
Shoreline Change Change (yd3/ft/year) Downdrift (Indian
Time Span of (ft/year) River County)
Data Beaches
Considered Brevard Indian Brevard Indian (yd3/ft/year)
County River County River
County County
1972 to 2002 0.4* 0.3* 4.0* 0.67* 0.49 (Nourishment)
0.68** 0.50** 1.00 (Bypassing)
0.9*** 0.63*"
1999 to 2002 3.5* 0* 5.2 2.7 2.38 (Nourishment)
4.3** 1.7** 4.4** 2.8** 0 (Bypassing)
4.0"** 1.3*** 3.9*** 3.0 ***
(5.6) (1.9)
* Based on Least Squares Analysis of Individual Monument Results
** Based on Least Squares Analysis of Averaged Common Monument Results
Based on End Point Analysis of Averaged Common Monument Results
()Based on Least Squares Fit to GIS Analysis Results
A second result evident from the data is that there is considerably variability present in the system. This variability is manifested by the differences between the rates in the time period from 1972 to 2002 and that from 1999 to 2002. In particular, it appears that the latter period is one during which there was greater transport to the south than during the entire period.




9. SEDIMENT BUDGET CONSIDERATIONS

Appendix D presents the basis and results of sediment budget considerations for Sebastian Inlet for two periods: Winter 1999 to Winter 2002 and 1972 to Winter 2002. The equations and results developed allow calculation of the required nourishment to balance the volumetric changes on the 30,000 feet north and south of Sebastian Inlet. Application of these equations and results has determined that for the period Winter 1999 to Winter 2002, there has been an average annual deficit of nourishment of 56,800 yd3/year. For the total period: 1972 to Winter 2002, there was an average annual deficit of 30,400 yd3/year.
The analysis considers the possibility of onshore sediment transport and it is shown that it is not possible to quantify the sediment budget definitively. It is only the sum of the: (1) differences between the sediment inflows to and outflows from the region, and (2) the total onshore sediment transport that can be quantified. The results in Figure 24 are for balanced inflows into and outflows from the region; this consideration requires onshore sediment flows into the region. Additionally, a bypassing of 50,000 yd3/year has been assumed in developing these results. The Reader is referred to Appendix D for more details.
10. RECOMMENDATIONS
Five recommendations have emerged from the present study; (1) Continue and extend semiannual monitoring, (2) Develop an agreed-upon basis for analyzing and responding to the data analysis results, (3) Analysis of the data in a bipartisan effort, (4) Consider extending the south jetty, and (5) Explore with the Florida State Division of Parks and Recreation, their position regarding various bypassing facilities located on the north jetty or north of the north jetty. Each of these recommendations is discussed further below.
10.1 Continuation of Semi-Annual Monitoring
It is recommended that semi-annual monitoring be continued and expanded to 40,000 feet north and south of SI. The present profile spacing of approximately 1,000 feet is considered appropriate.
10.2 Develop an Agreed-Upon Basis for Analyzing and Responding to Results
The data collected under 10. 1 could be analyzed, interpreted and acted upon in various manners. To ensure that the results be effective, an agreement regarding these issues should be resolved between the SITD, the State and other Stakeholders. The goal should be to stabilize the downdrift beach systems equitably through placement of adequate volumes of good quality sediment. The question of past management practices should be addressed using the data that are presently available. Issues to be resolved include whether to balance the shoreline and volume changes on the two sides of the inlet, the quality of the sediment used in beach nourishment, etc.




Back Bay
-12,000 +19.200*

-4.-.Q + 168,400
+ 123,700*
I
(dV/dt)Ns + 135,000 + 120,000"* Q N
1+ 141,300 Q + 50,400
B BN EBB QBP

Sand Trap' + 43,000
- 13,00/
QDR
0*
30,800**

ned)

+ 50,000 + 50,000**
dV/dt), S84,000** 20'000

- Ebb Tidal Shoal + 103,000 *
- 30,800**
.,Qos~s
+ 141,300 + 50,400**

71,400 14,600"

+ 168,400 *
*~QOUT
. -OUT + 123,700*
Figure 24 Example Sediment Budget for Two Time Periods. Transport Into and Out of Region Assumed to be the Same. The Quantities With a Single Asterisk
are for the Period Winter 1999 to Winter 2002 and Those With a Double Asterisk are For 1972 to Winter 2002. See Appendix D for Nomenclature.




Based on the available data, the beach systems to the north of SI have gained volume and dry beach relative to the beaches south of SI. It is reconumended that the basis for future agreements and actions be to balance the shoreline and volume changes over the long term.
10.3 Analyze Data in a Bipartisan Effort
As noted, data can be analyzed and interpreted differently by different individuals. The goal of the recommendation would be to ensure that the data are analyzed and interpreted according to 10.2. When questions and inconsistencies arise, they are to be examined and resolved equitably to the best of the abilities of the bipartisan analysts.
10.4 Consider Extending the South Jetty at Sebastian Inlet
It is clear that some of the erosion on south beach is due to sand drawn into the inlet around the south jetty. This occurs primarily during transport reversals when sand is transported from south to north by the waves and during flood tidal currents. The characteristics of such reversals are not well known, but may persist for several months, if not years. Regardless, careful consideration should be given to the erosional contribution of this sediment transport pathway and the benefits of a longer south jetty to the Indian River County beach systems.
10.5 Initiate Discussions With State Division of Parks and Recreation Regarding Their Position on Bypassing Equipment/Facilities
There are several methods which could be recommended for bypassing of sediment around Sebastian Inlet to the beaches of Indian River County. The present method is to allow sediment to be collected in the interior sediment trap and then to bypass this sediment. Other methods may be more efficient. One possible disadvantage of the present method is that it is the finer sediment that tends to be located seaward and thus tends to be drawn into the inlet and deposited in the sediment trap. Also, undoubtedly some good quality sediment is transported into SI but not deposited inside the sediment trap. An advantage of bypassing via the sediment trap is that no facilities are required on the outer shores.
There are several inlet bypassing operations in the State of Florida. These include fixed bypassing plants on the updrift jetties at Lake Worth Entrance and South Lake Worth Entrance. Weirs in the updrift jetties and sand collection in a deposition basin and removal by a dedicated dredge are present at Hillsboro Inlet and Boca Raton Inlet. Jupiter Inlet operates much the same way as Sebastian Inlet with the sand being collected in an interior deposition basin and then transferred to the downdrift beaches. The transfer of sand at Indian River Inlet, Delaware is accomplished by a jet pump arrangement suspended from a dragline boom. The slurry from the jet pump, which has no moving parts, is conveyed to a dredge pump and then pumped across the bridge to the downdrift beaches.




Recreation to describe the problem, discuss the various alternatives and determine their positions regarding the various options.
11. REFERENCES
Bruun, P. J. A. Battjes, T. Y. Chiu and J. A. Purpura (1996) "Coastal Engineering Studies of Three Coastal Inlets", Bulletin No. 122, Florida Engineering and Industrial Experiment Station, University of Florida, Gainesville, Florida.
Coastal Engineering Department (1965) "Coastal Engineering Hydraulic Model Study of Sebastian Inlet, Florida", Report No. 65/006, Florida Engineering and Industrial Experiment Station, University of Florida, Gainesville, Florida.
Coastal Technology Corporation (1988) "Sebastian Inlet District Comprehensive Management Plan", Vero Beach, Florida.
Dally, W. R. Personal Communication
Parkinson, R. (1995) "Grain Size Analysis of Fisher and Sons Samples", Memorandum Report with Attachments to Ms. Kathy Fitzpatrick of the Sebastian Inlet Tax District.




APPENDIX A
Historical Aerial Photos of Sebastian Inlet




Figure A. 1. An Early, but undated Photograph. Deposition Inside
Inlet Forms a Nearly Complete Blockage.

Figure A.2. Photograph of December 2, 1933. Note the
Extensive and Unvegetated Flood Tidal Shoals.

A-2




IZ -

Figure A.3.

Photograph on March 18, 1936. Note Newly Deposited Flood Tidal Shoals and Vegetation Present on Shoals Evident in Figure A.2.

Figure A.4. Same Photograph Date as Figure A.3, But Showing
Shoreline Farther to the North.

A-3




-4
: "= '

Figure A.5.

Photograph of Februry 14, 1943. Inlet Apparently Completely Blocked. Note Very Extensive Flood Tidal Shoals.

Figure A.6. Photograph on February 24, 1943.
Similar to Figure A.5.




10-25-1948

ft

L-A-

Figure A.7. Photograph on October 25, 1948. New Southwest
-Northeast Channel Being Cut and Previous
Channel Blocked by Dike.

J~&~ -~
-,,.
V
- tt
- -.,- .-~*-: '4
-' ~
7-
- ~ ,9- *\ ~ -,

Figure A.8. Photograph on October 27, 1948. Bulldozer Working
to Open New Inlet.

A-5




11-05-1948


- -
- a---

Figure A.9. Photograph on Novernber 5, 1948. Nine Days After
Photograph in Figure A.8. North Jetty Now Visible.

Figure A. 10. Photograph of November 15, 1948, Ten Days After
Photograph in Figure A.9. Note Nearly Clogged Channel.

A-6

4




12-19-1948

Figure A. 11. Photograph on December 19, 1948.

Figure A. 12. Photograph on January 13, 1949.
A-7

A




07-11-1949
--Now
M

Figure A. 13.

Photograph on July 11, 1949, Taken During Low Tide. (Note this photograph date may be in error.)

07-11-1949

Figure A. 14. Photograph on July 11, 1949. Note Bar Across Entrance.
(Note this date reported to be same for Figure 13, but is
believed to be later.)

A-8




Figure A. 15. Photograph on August 30, 1949. Note Fairly Straight
Channel and No Shoals Apparent.

Figure A. 16. Photograph on March 26, 195 1. Note
Extensive Recent Dredge Spoils on South
Side of Channel.




Figure A. 17. Photograph on March 26, 195 1, Same Date as
Figure A. 16, But Showing Shoreline Farther South.

A-10




Figure A. 18. Photograph on April 4, 195 1. Note Shoreline Offset.

Figure A. 19. Photograph on April 24, 1958.

A-1 I




Figure A.20. Photograph on November 6, 1962. Note Narrow,
Channel Dredged Through End of Flood
Tidal Shoat.

Figure A.2 1. Photograph on November 6, 1962, Same Date as
in Photograph of Figure A.20, But Showing a Greater
Distance to the North.

A- 12




Figure A.22. Photograph on January 31, 1963, Showing
Substantial Shoreline Offset.

A-13




Figure A.23. Photograph of March 25, 1968.

A-14




Figure A.24. Photogra[ph on January 12, 1970. Note Extended
North Jetty.

A-15




Figure A.25. Photograph of February 13, 1970.

Figure A.26. Photograph on December 29, 1970. Note
Relative Absence of Shoals Between Jetties and in Outer Portions of Entrance Channel.

A-16




Figure A.27. Photograph on February 14, 1974.

A-17




At~
. . ,\ ...
Figure A.28. Photograph on May 13, 1974. Note Narrowed and
Widened North and South Beaches, Respectively
Apparently in Response to Southerly Waves.

A-18




Figure A.29. Photograph in 1976, Specific Date Unknown.

A- 19




Figure A.M. Photograph on January 11, 1978.

Figure A.3 1. Photograph on February 28, 1980.
A-20




Figure A.32. Photograph on January 30, 1981. Note Widened
and Narrowed North and South Beaches, Respectively.

A-21




Figure A.33. Photograph on January 1, 1983.

Figure A.34. Photograph on May 10, 1984.

A-22




Figure A.35. Photograph on February 13, 1985.

Figure A.36. Photograph on April 18, 1986.

A-23




Figure A.37. Photograph on February 25, 1988.

Figure A.38. Photogra[h on January 5, 1989. Note Widened and
Narrowed North and South Beaches, Respectively.

A-24




Figure A.39. Photograph on January 17, 1992.

Figure A.40. Photograph on March 10, 1993.

A-25




Figure A.41. Photograph of Sebastian Inlet on June 18, 1998.
Source of Photograph is Evans Library, Florida
Institute of Technology.
Ns,
Figure A.42. Photograph of Sebastian Inlet on July 24, 1999.
Source of Photograph is Evans Library, Florida
Institute of Technology.

A-26




APPENDIX B
Plots of Average Profiles for Brevard and
Indian River Counties




2002.1

Brevard County

10
z o 0 C4 -10 = -20
C
-30
-2

0 200 400 600 800 .1000 1200 1400
Distance in Feet

10
z
V 1999.1
-10
= -20
C
>
-30
-200 0

200 400 600 800 1000 1200 1400
Distance in Feet

Figure B- 1. Comparison of Average Profiles for Brevard and Indian River Counties,
January 1999 vs January 2002.

1999.1 \\
-, I

:00




0, 2002.1 t ]Brevard County
> 1999.6 .
-20
-30 L____-200 0 200 400 600 800 1000 1200 1400
Distance in Feet
Figure B-2. Average Profile for Brevard County, July 1999 vs January 2002. There was Inadequate
Number of Good Quality Profiles for the Time Period in Indian River County.




10 0
20
-10
-20
-30
-200

0 200 400 600 800 1000 1200 1400
Distance in Feet

N, I Indian River County
2002.1
2000.1

-30 1 1i1 1 1 1 1 1 1__ 1 I
-200 0 200 400 600 800 1000 1200 1400
Distance in Feet
Figure B-3. Comparison of Average Profiles for Brevard and Indian River Counties,
January 2000 vs January 2002.

10
0
-to
o 20
LL




7 Brevard County
o 0 1
I>11 2002.1
C -10 -i
2000.6
00
.-Li"-

-200 0

200 400 600 800 1000 1200 1400

Distance in Feet
Figure B-4. Average Profile for Brevard County, July 2000 vs January 2002. There was Inadequate
Number of Good Quality Profiles for the Time Period in Indian River County.




>
o 0 0 -10
-20
o
V
30
-200
10

0 200 400 600 800 1000 1200 1400
Distance in Feet

Indian River County

2001.1 \N
-10
-20 -- -

1- -I - -I l I l____ _I l

-30
-2C

0 200 400 600 800 1000 1200 1400

Distance in Feet
Figure B-5. Comparison of Average Profiles for Brevard and Indian River Counties,
January 2001 vs January 2002.

2002.1

00




10
I0
z
0
-10
o -20
-30
-200

Indian River County ~2002.1 2001.6 ,,

200 400 600 800 1000 1200 1400

Distance in Feet

Comparison of Average Profiles for Brevard and Indian River Counties, July 2001 vs January 2002.

0 200 400 600 800 1000 1200 1400
Distance in Feet

'U
z
0
V C4 -10
-20
LL)

-30 L
200

Figure B-6.




APPENDIX C

SEDIMENT INTERACTION WITH LITTORAL BARRIERS AND INLETS

C-1




APPENDIX C

SEDIMENT INTERACTION WITH LITTORAL BARRIERS AND INLETS
C.1 Introduction
The purpose of this appendix is to introduce and demonstrate some of the characteristics of complete and partial littoral barriers and inlets. There are similarities and differences between littoral barriers and inlets in the presence of a net longshore sediment transport. The main similarity is that sand accumulates and erodes on the updrift and downdrift sides, respectively. The main difference is that inlets can remove sand from the beach system through storage in the ebb and flood tidal shoals whereas for littoral barriers, the sand volume stored on the updrift side must equal the volume eroded on the downdrift side. Although the results to be presented are idealized, they form a framework for findings presented for Sebastian Inlet.
Two methods will be applied here. The first method is analytical or theoretical and is limited in capabilities whereas the second is a numerical model which has been modified slightly for purposes of application to Sebastian Inlet.
The two types of features addressed in this appendix are illustrated in Figures C. 1 a and C. lb below.
Sediment Transport Sediment Transport
I e Ebb Tidal
Flood Tidal Shoal
Shoal r)
a) Littoral Barrier Along an b) Inlet Along an Otherwise
Unobstructed Shoreline Unobstructed Shoreline
Figure C. 1. Two Types of Littoral Barriers Addressed in This Appendix.

C- 2




C.2 Applications of Analytical Model to a Littoral Barrier

Several results associated with a littoral barrier will be illustrated based on the analytical model. In the applications, an attempt has been made to approximate the conditions occurring at Sebastian Inlet. The model requires a breaking wave angle relative to the shoreline, ab, a vertical dimension of the active profile (here referred to as h. + B), a so-called longshore diffusivity, G and a barrier length, Y. The values selected for the applications are: a(b = 3.52, h. + B = 22.7 feet, and G = 0.159 ft2/second. This combination of variables results in a constant net longshore sediment transport to the south, Q = 260,000 yd3/year. The barrier length is 500 feet.
C.2.1 Patterns of Updrift Shoreline Advancement and Downdrift Shoreline Recession at a Littoral Barrier
The patterns of updrift shoreline advancement and downdrift erosion are presented in Figure 2. The upper panel of this figure shows the calculated shorelines at 1, 5, 10, 20 and 50 years and it is seen that the patterns of shoreline change on the two sides of the inlet are antisymmetric. Two solutions have been applied in Figure C.2. The first solution applies prior to bypassing at the littoral barrier and the second is for the case after bypassing has commenced. For the case represented, bypassing commences after 10.3 years. The lower panel represents the longshore distributions of area accumulation and loss on the updrift and downdrift sides, respectively. These distributions are also antisymmetric.
C.2.2 Patterns of Shoreline Change Rate and Longshore Sediment Transport
The upper panel in Figure C.3 presents the patterns of shoreline change rate for different times after installation of the littoral barrier. It is seen that initially the changes are concentrated near the barrier; however, as time progresses, the effect is manifested farther and farther from the barrier. As noted earlier, bypassing commences at 10.3 years for this situation, so for the first three times presented (1, 5, and 10 years), the total area under these three curves is equal to the total area being transported into the domain (Area rate = volume rate/(h, + B) = 309,300 ft2/year). The patterns of shoreline change rate are antisymmetric.
The lower panel presents the patterns of longshore sediment transport. The lack of bypassing for the first three times presented is evident after which the bypassing commences and is approximatelyl85,000 yd3/year after 50 years which amounts to 71% of the ambient transport rate.
C.2.3 Bypassing Rates
It is of interest to examine the rates of sediment bypassing at the barrier. In a later section of this appendix, the bypassing rates will be examined for both unidirectional and oscillating deep water wave directions. The upper panel of Figure C.4 presents the bypassing for a total period of 100

C-3




600
400 200
0
-200
-400
-600
-1.

1000 800 600
400 200
0
-200
-400
-600
-800

. ... :... .. .. ... : ..: ...... ...;., .
h
. .... ... .. ... .. .. .... .. . / .
. .

.- Year ... i ... 5 Years
.... ...... i...... .... .... I0 Years
20 Years
---- 20Years

. . .
. . .. .. .. .. .7.. . . . . . .
.. .. . .
.. .. . .

2

-1UUU
-12

-8 -4 0 4 8
Distance From Littoral Barrier (Miles)

-8 -4 0 4 8
Distance From Littoral Barrier (Miles)

Figure C.2. Interaction of Littoral Barrier With Adjacent Shorelines. Analytical Model.

C-4

.. - ... ... . .. ..... -...... .. 1 1 .. ... .. . .
- I Year
. .. 5 Years
.. .. ......... ... ... .......... ......... ...
, , , , . . . - - - - .,,- . . . . . . . . . . .... . . 5 0 Y e a r s
. . ... .i ..... i................ > ." I ..... .. ........... .. .... i ..... i.....
:. ..... .... i........ . . .. i ...... ...... i...... i...... ...... "....I
.... . .. ..
. . : . . . . . . . . . . . .: .. .. . .. !.. .. .. . ...
.......... ........ . ....
. ........... ............. ...................... .... ......
.. ....... ..... .. .......:.... . .
. ............ ,...... ....... ............. ...... ........... ...... ..... .......
. . . . . .. . .. . .... .. ... .. .. ...




80 60
40 20
0
-20
-40
-60
-80
-1

2

-8 -4 0 4 8
Distance From Littoral Barrier (Miles)
Longshore Distribution of Shoreline Change Rates

12

-8 -4 0 4
Distance From Littoral Barrier (Miles)

Longshore Distribution of Longshore Sediment Transport Figure C.3. Alongshore Distributions of Shoreline Change Rate and Associated Transport.
C-5

................ Year
...... ............... ....... 5 Years
........... ............. Years
....... ....... ...... 20 Years
................. 0 Years

... . .. . .5 .. ..

P. 300
0
200
0
(0
200 I:.
C
0
0
W.

.... ....... .. .. .
. .. .. . . ........ .
... ...: .. .. .. ....... -, -. .: .;...... Ix.. ............ ....... ... ..
4"- i ,% I' "i 0Years
....... '.......: ....... '........: ...... .. .. "..... ""............ I Years
I.... 10 Years .............. .............. ......... ... ..... ....... ...... -- 20 Y ears
: : : 50 Years

L

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

............ ....... ......
. . . . . . . . . . . . . . .
. . . . . e . . . . .
. . . .. . . . . . . . . . . . . . . . . .
.......... ... ....... ...............
. . . . . . I . . . . . . . . . . . . . .
...........................................

I

I




300 *Ambient Transport Rate:= 260,000 yd3eart
0 200
C
c 200 ... . ... .. ...
0
Time (Years) Sediment Bypassing Rate Around Littoral Barrier CUm300: ,
) Ambien transport Rate= 260,0O00yVd3/Yearii
200. ............... ....................
100 ... ....... ........ ..........
4
C
I
C
0
0 100 200 300 400 500 600 700 800 900 1000 Time (Years) Sediment Bypassing Rate Around Littoral Barrier
Figure C.4. Bypassing Rate Around a Littoral Barrier for Two Time Periods

C-6




years and the lower panel for a total period of 1000 years. It is interesting that the transport after 100 years is still only 77 % of the ambient transport. As presented in both panels, the approach to bypassing of the full ambient transport is slow and after 1,000 years, the transport is 92 % of the ambient. The portion of the transport which is not bypassed accumulates on the updrift beaches and an equivalent amount erodes on the downdrift beaches.
C.3 Applications of Numerical Model
As noted, advantages of a numerical model over the analytical model described earlier include flexibility to represent situations that are more complex and representative of the actual situation. The sections below examine the effects of a variable wave direction and the effects of sand removed from the beach system through storage in the flood and/or ebb tidal shoals. The numerical model also accounts for the nonlinearity of the transport equation.
C.3.1 Shoreline Response to Constant and Oscillating Wave Directions
For the cases to be presented the average net longshore sediment transport is 260,000 yd3/year, the same as for the analytical model. However for this case, a deep water wave height and period were specified which resulted in this net longshore sediment transport. The wave height and period were: H. = 1.6 feet, T = 7 seconds. The deep water wave direction depended on the fluctuating wave direction, which was specified in terms of deep water conditions, as
ao(t)= a0+Aa0sinort
where a (= 2it/T) is the angular frequency of the oscillation and T is the associated period ( 1 year in the application here). For the case of Aao = 0, ao = 8.3 10, and for A ao = 200, ao
9.650. The different values of ao required to cause a net transport, Q = 260,000 yd3/year are due to the nonlinearity of the transport equation. The oscillating transport rate is presented in Figure C.5 for a one year period.
Results are presented in Figures C.6 and C.7 for the average shorelines due to the constant and oscillating wave directions, respectively. The shorelines presented are the average shorelines for the year indicated.
Results for the maximum and minimum shoreline positions for the year indicated for the oscillating deep water wave direction are presented in Figures C.8 and C.9, respectively. It is seen that the shoreline cannot exceed the 500 feet length of the barrier nor can the minimum position downdrift (recession) of the barrier exceed this amount.

C-7




3000
3%2000
t:
0
(V)

1000
0
0

- 1000
6( 4
E 2
(o
0
cc
,Q -2
0 C0
-4
-6

.. .. . .. . . .. . . ... . /
Xt.1
.. ... .. ... ..... '. .. ... ..... ............ ". . 1 '
i~ ~ . ... .. .. ...... .... / / ..!
'K:
... ..... ..... ... ; ..... ..... . .

Average Shoreline Over Ist Year ..... ......... Average Shoreline Over 5th Year ........-Average Shoreline Over 10th Year
------- Average Shoreline Over 30th Year
Average Shoreline Over 50th Year
. ...a...e.

." s' ... . .
:../ : / / ..'/,l
' ...........
1 /

0
00 00 00
0 00 00 00
-1

C-8

.. -.... :... ... ... .......... .... .... ..... ...... ..... ... .. .... ...... ......... ..... .......... .. .. i. ....
..~... ..... ... .. ..... i..... ..... i.... ........
. .i l I I I ..

0

.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Time (Year)
Figure C.5. Oscillating Ambient Sediment Transport
Due to Oscillating Deep Water Wave Direction.

-8 -6 -4 -2 0 2 4 6
Distance from Barrier (Miles)
Figure C.6. Average Shorelines For Constant Wave Direction.

0

-I- - --. .. .. ..

. . . ... ... .... ....... .. I .. .. .... . .. ....... . .
..... ! i ~ i ..... ..... ..... ...... ...... ...... . .
~~ ~~ ~~~ ~~~~ :... .. .. .. .. ......

8

I i I I I I i I i I I I I I I I I I




600
400 4-'
C
a) E 200
A 0 C0
2: -200
0 CO,
-400
.J'Ju

~1

600
400 .4
E 200
8
,_. 0
C 01)
,-200 0, CO
-400

-Ann L

-10 -8 -6 -4 -2 0 2 4 6 8
Distance from Barrier (Miles)
Figure C.7. Average Shoreline Positions for Oscillating Wave Directions.

-10 -8 -6 -4 -2 0 2 4 6 8 10
Distance from Barrier (Miles)
Figure C.8. Maximum Shorelines Associated With Oscillating Wave Directions.
C-9

........................ .... ............. ..... i...... i...... ......
. . ... . . ... . ... . . . . . . . . . . . . . . : . .. :.. . ... .
.... ; ... ... i ...": ..... "......: ......: ...... ...... :...... .. !...... ;..... ;..... ;........... .. .: ..... ... ...... ....

i i i i "i i : i "): aximum Shoreline Over 1st Year ..
: : : : : f ........ Maximumn Shorline Over 5th Year
.................... ....... ........ --- --- Ma., ."m . ...ShorlineOver 10thYear ....
i i i i i i i /'.'-:--..... Maximum Shoreline Over 30th Year
.... i.... i ..i..... i..... i...... :...... ...... ....t.. -- --- Maimuttm Shoreline Over 50t Year ..
; ;i j/ ;.............
~~~~~...... ..... ..... ..... ..... ...... ...... .; : ..... .. ..... "..... ..... !..... ..... ..... .. ... ..... "...... i.....
i i :: :..........,.. ..........rr e r i i
..... : ... .. ..... ..... ..... ...... :''. ; ....... ..:..... .... : .... :..... :..... ..... ..... .....
.... .".--!": I .:'" ............ i
.. ... ... ... .. ... ...i ...... ...... .. .... o !..... ... :. .. i .... i.....

.... ... .. :... ............................. ..........:. .A e a e S o e i e O e e e r I .
Average Shoreline Over I1st Year
......... Average Shoreline Over 5th Year .... ....... Average Shoreline Over 10th Year .
--------------- Average Shoreline Over 30th Year
Average Shoreline Over 5th Year . . ... . ... . .. ... . . . . . .
............ ,... . ...... .
-7 arrief.
.. . . ... ..... ..... ..... f. .. .. ........ .,". ... ...... .....




600
.....-.... .Minimum Shoreline Over let Year .
......... Minimum Shoreline Over 5th Year
400 .......... ...... ...... ...... Minimum Shoreline Over 10th Year ...
-----, Minimum Shoreline Over 30th Year
................/.. ... Minimum Shoreline Over 50th Year
.... ... ....: ... ..... ...... ..... ........ 7 '" . . ....
E 200 : : : : : : :/ :
Barrier.
a
... ...!... .. .. ...: ... ...... .. ....:.... ;..... :..... :..... :.... ,..... ......: ..... : ....
.... -... ... :.. ... ..........".-.. ..B. a ~r ... ..... ..... ........ ..
C
.0 .. ......... 0..0..... ...... ....
0 CO,
. o ....... ..: ...i ... i.. ..... ............ ... . . ....i..... ...i..... !......
- 4 0 0 . .. .. . . . . . . . . . . . . . . . .
-600
-10 -8 -6 -4 -2 0 2 4 6 8 10
Distance from Barrier (Miles)
Figure C.9. Minimum Shoreline Displacements Associated With Oscillating Wave Directions.
C.3.2 Volume Stored on Updrift Beach for Unidirectional and Oscillating Wave Directions
It is intuitive that for the same net longshore sediment transport rate that the volume stored on the updrift beach would be less for an oscillating wave direction than for a unidirectional wave direction. The reason is that the greater wave directions will cause more sand to be transported around the littoral barrier, leaving less on the updrift beaches. To address this issue, the numerical model was exercised for the unidirectional and oscillating wave directions described in the preceding section and the results are presented in Figure C. 10. It is seen that prior to bypassing, the accumulations on the updrift beaches are approximately the same for the steady and oscillating wave directions, respectively; however, after bypassing commences, the two quantities gradually diverge. After 50 years, the two differ by only 7%. At any time, the total volume bypassed is the difference between the "Total Volume Transported" into the region (based on Q = 260,000 yd3/year) line in Figure C.10 and either of the two curves.
C.3.3 Effect of Sand Stored in Flood and/or Ebb Tidal Shoals
The cases presented heretofore have resulted in the same volume (area) stored on the updrift side and eroded on the downdrift sides of the barrier. However, with sand stored in the ebb and flood tidal shoals, these two volumes will differ by the amount of sand removed from the system through storage on the flood and ebb tidal shoals.

C-10




8
.. . . . ....... ......... ..........; ..........: .. .......... :..........: ...... . .
.To ta V o.u.e............. ..... .........
U) 7 ......... :. ............ .. . . . . . .... .-.......... . : ....... .. .. .
S Transpopd.
. .. ............. ... ..,.. .... .. .... ......
6 . i0 ... .
.. .... .......... i.......... i...... !.. . - :- .3.. ,, ., .. :. ..... ... ...- .....
0 5'
. . . . . . . . .. . .
. ... I ..........
........ '.......... .... ...... ......... ",...... .I ...... ."..... .......... ,.......... .........
. I I ,
.. ....................... .. . : . ........ .; .. ...... ..... -.--:.. ... ........ ..... ... .. .. .
Cf: 3, ...........,,....,........ ............. . . . . .. . .
.. . . . . . . . . . . . . .
4-- ... ......
0. . 2 ..... ... ........... ......... ...,.-" .... / .. ...... .......... .......... ......... :.........
2 ...... ............ .......... .... o n
C
. . .. . . . . .. .. . I . . . . . . -. . . . . . . . . ." . . .i . . .i . .
..........p W ater W... Av.I .. ..... e e DW..a t i.r.W .~~..D ~.p .31 .
0...............Ye ars...".
.......... "1..... .9.P .. .. .. .. .. .. . :"" ......
..... ... ... Z .:. . ..... ........ ... ..... ... ..... . . . .
.2O 1 : Deep Water Wave Direction = 9.65 20
0; ;f I I
0 10 20 30 40 50
Years
Figure C.10. Sand Stored on Updrift Beach for Unidirectional and Oscillating Wave Directions.
Figures C. 11 and C.12 present the shorelines for the case of 20% and 50% of the transport, respectively, that would otherwise be bypassed being stored in the flood and/or ebb tidal shoals. The effect on the downdrift shorelines of the sediment removed and stored in the flood and/or ebb tidal shoals is evident as greater downdrift recession compared to the updrift shoreline advancement.
C-11




800 :
.. ...... .. i....... .. .i .. ..... ..... "...... :.......: ........ v r g h r ln v rI tY a .
-Average Shoreline Over 1st Year
600 ...... ................ I ... ......... Average Shoreline over th Year ...
........ Average Shoreline Over 10th Year .......................... ........ . Average Shoreline Over 30th Year ...
/1 Average Shoreline Over 50th Year
4 0 0 .... .... ...... ..... ..
(1) ... : .. .. .. .. '; ... ":... "... ... . .., .. .. ..... i...... :...... ...... ..... : . . . . ...
E7
200 .. ...... . . ar er
CiT 0
....... ::..... .... .. ...... ..L . .
z oo ..... ..... i ~i ..... ........ ...- I ".. .. I. ...... ..... . .... ..r~ ..... . .i. ..:. .
0
4-200 .......
.--(::: ~ ~ ~ ~ ~ ~ ~ ~ ~ ....... ..... : ":/ / ...:...:... .. ;...:..
. ~ ~ ~~ ~~ ...i...i... . ... .. .. .. .. .. 7 ...... .......:.:. .. ...
6 0. . .. . . . . i. . . . . . i . .
. . ..o o. . . .. . . . . . . . . . . . i . . . . . .
--to -8 -6 -4 2 0 2 4 6 8
Distance from Barrier (Miles)
Figure C. 11. Average Shoreline Displacements for 20% of
Potential Bypassed Sand Stored in Flood and/or Ebb Tidal Shoals.

uu
600
400
C
()
E 200
0)
(D
00
- 0
0.
C -200
..0
00
-c
O' -600
-00

-1~nN

1 -10

-8 -6 -4 -2 0 2 4 6 8
Distance from Barrier (Miles) Figure C.12. Average Shoreline Displacements for 50% of
Potential Bypassed Sand Stored in Flood and/or Ebb Tidal Shoals.
C-12

Average Shoreline Over IstYear
.. .. . . :.. .. .: .. .".. . ... i........ i ....... A e a e S o e ie o e t e rI.....
........ Average Shoreline over 1th Year .... .... i... ..... ..... i..... i ....i...... .. /, I..... ----- Average Shoreline Over 10th Year
------- Average Shoreline Over 30th Year ....... Average Shoreline over 50th Year
.... ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .. .. .. . ......... .... ..... .......... ..:. ..; :. .
. . . .ri ... ; 2
: : : ~ ~ ~.... ... ... ..... .... ..... ... ....._.. . n., / : .."" :;
" : .. . : "-" i.... ....... : :
..... ... . .. . . . . . . . . j ' . . . .i .
...... ... . .. .. .. .... .......... ...... .. .. . .
. . . . . . . . . . ... . ... .. . . . . . . .. . . .. . . . . .
.. . .. . ... .. .. .. . T .. . ....... .... .. ..:. .: .i. .:
. . . .. ... . .... .. .... . : i..... ".... ...... .:... .: ..... :......
..... i ..... i........... i ..... ..... ... ................. .... .
: : : : i ~ ~ . .. .. .. ....... .:. . . "
.. ". .. .. . .. .. ".. . ' :. .. .: ..: '" . . . . . .. . . :. .'
: ', ,., ,




APPENDIX D
SEDIMENT BUDGET CONSIDERATIONS FOR SEBASTIAN INLET AND ADJACENT BEACHES

D-1




APPENDIX D

SEDIMENT BUDGET CONSIDERATIONS FOR SEBASTIAN INLET AND ADJACENT BEACHES
D.1 Introduction
The results of the survey analysis presented in the main body of this report provide information that can assist in the development of sediment budgets. Complete results are available for the period Winter 1999 to Winter 2002. Outer shoreline volume changes are available for the period 1972 to Winter 2002 and volume changes are available for the sand trap, ebb tidal shoal and back bay areas for the period 1989 to Winter 2002. Thus, this information allows sediment budgets to be developed for two periods: (1) Winter 1999 to Winter 2002, and (2) 1972 to Winter 2002 although the data for the latter originate from different periods..
D.2 Methodology
Sediment budgets will be developed including the possibility of onshore sediment transport. Referring to Figure D. 1, the sediment budgets for the north and south beaches and inlet and offshore systems are:
D.2.1 Sediment Budget for North Beach, Inlet and Offshore System
O = (dV / dt)Ns +QBP + QST,N + QBBN, + QEBB -QOS,N +QDR (D.1)
which can be rearranged to represent the rate at which volume is stored in the north beach system and in the inlet system,
QIN Q. + QOSN = (dV / dt)Ns + QST,N + QBB,N + QEEB + QDR (D.2)
D.2.2 Sediment Budget for South Beach, Inlet and Offshore System
QOUT = -(dV / dt)ss + QEp + QDR+QNOuR + Qoss- QST,S QBB,S (D.3) which can also be rearranged to represent the rate at which volume is stored in the south beach system and the inlet system
QEP + Qoss- QOUT + QDR + QNOUR = (dV / dt)ss + QST,S + QBB,S (D.4)
For the north beach system, QIN is the average annual rate at which sediment volume enters the

D-2




Back Ba

QDR

QIN
(dV/dt)NS y Area
I
S -, %P I
r
STN BBN EBB +QBP
sQ,s Ebb Tidal Shoal
BP
dV/dt)ss
QOSS
QNOU
-----QouT
Figure D. 1 Definition Sketch of Sebastian Inlet and Vicinity and Terminology Used in Developing Sediment Budget.

D-3

Sand Tral




north system due to longshore sediment transport, (dV / dt)Ns is the volumetric rate at which sediment is being stored (accumulated) in the north beach system, QBp is the rate at which sand is bypassed around Sebastian Inlet (SI) from the north beach system to the south beach system, QST,N is the rate at which sand is transported and deposited in the sand trap from the north beach system, QEBB is the rate at which sand is stored in the ebb tidal bar system, QBB,N is the rate at which sand is transported and deposited in the back bay system from the north beach system, Qos,N is the rate at which sediment transport is entering the system from the offshore and QDR is the average rate at which sediment is removed from the sediment trap and placed on the south beach system. For the south beach, the definitions are quite similar, except for the following: QNOuR is the average annual nourishment rate with sedimentsfrom outside the system considered here and Qos,s is the average annual rate at which is entering the south system from offshore. The total rate at which sand accumulates in the sand trap, QSTI is QST = QST,N + QST,S and the total rate at which sand is stored in the back bay region, QBB is QBB = QBB,N + QBB,S.
The left hand sides of Eqs. (D.2) and (D.4) represent the net rates of sediment inflow into the beach and inlet systems north of and within SI and south of and within SI, respectively. The quantities on the right hand sides of these equations can be evaluated from the surveys and other available information.
Adding Eqs. (D.2) and (D.4)
QIN QoUT + QOS,N + Qoss + QNOUR
= (dV / dt)Ns + (dV / dt)ss + QsT + QEBE + QBB
The right hand side of the above equation represents the total rate at which sand is stored in the beach, nearshore and inlet system. The left hand side represents the sources of sediment which lead to this total volumetric rate of storage. However, a portion of this stored amount is due to nourishment, QNOUR"
D.3 Determination of Appropriate Nourishment Quantities The net amount of storage that would occur on the beaches in the absence of the inlet if AQ = QIN QOUT = 0 that is if the surveys encompass the entire region of the inlet effect, is:

D-4