CENTRAL PALM BEACH COUNTY COMPREHENSIVE EROSION CONTROL PROJECT REFORMULATED SHORE PROTECTION ALTERNATIVES

Transcription

1 CENTRAL PALM BEACH COUNTY COMPREHENSVE EROSON CONTROL PROJECT REFORMULATED SHORE PROTECTON ALTERNATVES PREPARED FOR: PALM BEACH COUNTY PREPARED BY: COASTAL PLANNNG & ENGNEERNG, NC. June 213

2 CENTRAL PALM BEACH COUNTY COMPREHENSVE EROSON CONTROL PROJECT REFORMULATED SHORE PROTECTON ALTERNATVES Executive Summary Due to the effects of recent storms and long-term erosion, the shorelines along the Towns of South Palm Beach and Lantana have been categoried as eroded. Although the long term erosional trend is moderate, erosion and shoreline retreat patterns can be highly variable due to the effects of storms, erosion waves, and nearshore hardbottom. To restore the shoreline to a moderate beach width, a shore protection project is being considered for the area between the northern end of South Palm Beach and the Rit-Carlton hotel in Manalapan. t is anticipated that that the Palm Beach sland Beach Management Agreement (BMA) being developed in coordination with the Florida Department of Environmental Protection (FDEP) will not include an erosion control project for South Palm Beach and Lantana. Due to the extensive hardbottom, seawalls, and narrow beaches in this area, an Environmental mpact Statement (ES) is expected to be required for projects in the area. Accordingly, Palm Beach County is now seeking a fill design without breakwaters to last 2 to 3 years. To identify the most appropriate shore protection plan, the erosion rates between 24 and the present were reviewed to assess the present erosion patterns. Seven alternatives were then formulated based on those erosion rates and previous studies of the project area. The Delft3D morphological model was recalibrated from previous studies based on more recent erosion patterns. The performance and impact of each alternative over a 3 year project life was then assessed using the calibrated model. For comparative purposes, the no-action scenario (Alternative A) and original recommended plan (Alternative B: 13 breakwaters with 75, cubic yards of fill) (CPE, 211) were simulated with the recalibrated model and compared to a fill only alternative (Alternative C: 75, cubic yards) and an alternative with short low-profile groins with fill (Alternative D: 7 groins with 75, cubic yards of fill). f Alternative B was constructed, benefits would be concentrated along the northern third of the project area and a 2, foot updrift segment. Benefits along the rest of the project area would be low. f Alternative C was constructed, erosion into the preconstruction beach profile over the first 3 years would likely occur. f Alternative D was constructed, the amount of erosion would be substantially less than the fill-only alternative and provide a more uniform beach due to the benefit of the groins. After 3 years, fill would still remain along the north and south ends of the project area. Based on the results of Alternative D, an erosion control solution with groins and fill was determined to be viable option and was further refined to optimie performance. Based on the initial model simulations and sediment transport analysis, several alternatives were developed using approximately 75, cubic yards of sand in varying fill distributions, with and without groins. n addition, a larger, fill-only alternative with 16,6 cubic yards of material was developed based on recent erosion rates to last 3 years without any structures. i COASTAL PLANNNG & ENGNEERNG, NC.

3 Based the results of the model simulations and analytical analyses, the County s objective to address erosion with a moderate sied project lasting 2 to 3 years, and the improved performance of the optimied fill distribution with groin stabiliation, Alternative G is the recommended plan: Approximately 75, cubic yards of sand in an optimied fill distribution. Seven groins extending from the existing seawalls to the post-construction water line. The recommend plan for the project area (Figures E-1 and E-2 below) includes both sand fill and short groins strategically placed in conjunction to maximie the project life and minimie hardbottom coverage. Under a typical wave climate, the project is expected to last an average of 3 years, although minor erosion into the pre-construction beach profile may occur in some locations (< 1 c.y./foot). The hardbottom impact associated with this alternative is roughly 1.4 acres based on the March 212 hardbottom mapping, which would occur primarily at construction. Changes in hardbottom exposure between the time of this analysis and the time of permitting and construction will result in variations to these estimates and the mitigation that may be required by regulatory agencies. Excluding long-term physical and environmental monitoring, construction costs associated with the recommended plan are estimated to be $3,85, for beach fill and structures, $1,8,625 for hardbottom mitigation and turtle monitoring around the time of construction, and $488,562 for associated costs and contingencies, for a total cost estimate of $5,374,187. The results of this numerical modeling study should be used in conjunction with other coastal engineering assessments and prudent engineering judgment. Further engineering is recommended prior to implementation. ii COASTAL PLANNNG & ENGNEERNG, NC.

4 NOTES: 1. OA TE OF AERAL PHOTOGRAPH: 3/3/ GRAPHC SCALE N FT Figure E-1: Recommended Plan Beach Fill and Groin Layout (Alternative G). iii COASTAL PLANNNG & ENGNEERNG, NC.

5 March 3, 212 Aerial Volume Changes, Years -3, Entire Profile, Alt. A & G ,-r--r-c:::;:c:=c:=c:=c:====:::;-l Alt. A Volume Changes, Years -3 --Alt. G Remaining Fill, Year 3 --All. G nitial Fill Volume at Year --mpact(-) Benefit(+) of Alt. G R R R-1;J Q) Ol c :.c t::: 82 iii <U w _j ll R R-1;J6 + R R R R-14 + R R R Easting (feet) Remaining Fill (c.y./foot) Figure E-2: Performance of the Recommended Plan Given a Typical Wave Climate Based on Waves between December 28 and January 212. iv COASTAL PLANNNG & ENGNEERNG, NC.

6 CENTRAL PALM BEACH COUNTY COMPREHENSVE EROSON CONTROL PROJECT REFORMULATED SHORE PROTECTON ALTERNATVES Table of Contents 1. NTRODUCTON SUMMARY OF THE COASTAL SYSTEM ALONG PROJECT AREA General Recent & Future Projects Sediments Beach Erosion DESGN OF ALTERNATVES DELFT3D MODELNG STUDY General Updated Model Calibration Grids nitial Bathymetry Waves Winds Water Levels Hardbottom and Bedrock Existing Structures Model Calibration Alternatives Alternative A - No-Action Alternative B - Original 21 Recommended Plan Alternative C - 75, Cubic Yards of Fill without Structures Alternative D - 75, Cubic Yards of Fill with Short Groins Alternative E - Fill Able to Last 3 Years without Any Structures Alternative F Fill Optimied to Minimie Hardbottom mpacts and Maximie Project Life Alternative G - Fill Optimied to Minimie Hardbottom mpacts and Maximie Project Life with Groins RECOMMENDED PLAN - FLL OPTMZED TO MNMZE HARDBOTTOM MPACTS AND MAXMZE PROJECT LFE WTH GRONS (ALT. G) Long-Term Performance Maintenance Requirements Hardbottom mpacts Recreational & Sea Turtle Nesting Benefits Construction Costs CONCLUSONS REFERENCES v COASTAL PLANNNG & ENGNEERNG, NC.

7 List of Figures Figure 1: Project Area Location Figure 2: Damaged Seawall at the Mayfair House Condominium, October 3, Figure 3: Damaged Sidewalk at Town of Lantana Public Beach, October 29, Figure 4: CPE (211) Alternative Figure 5: CPE (211) Alternative Figure 6: CPE (211) Alternative Figure 7: Seawall under Construction at Lantana Public Beach, March 4, 21 Photo Figure 8: March 3, 212 Aerial Photograph of Completed Lantana Public Beach Seawall Figure 9: South End Palm Beach Restoration Plan View Figure 1: South End Palm Beach Restoration July 27, 212 Permit Cross-Sections (Coastal Systems, 212) Figure 11: Recent Mean High Water (+.45 NAVD) Shoreline Changes Figure 12: Recent Volume Changes Figure 13: Representative Profiles at Concordia East (R-135) and Lantana Public Beach (R- 137) Figure 14: Alternative B & C Fill Layout Figure 15: Typical Breakwater Cross-Section, Alternative B (CPE, 29) Figure 16: Typical Alternative D & G Groin Cross-Section Based on CPE, Figure 17: Alternative D Groin & Fill Layout Figure 18: Comparison of the Discrete and Analytical Solutions for a Triangular Beach Fill Figure 19: Predicted and Observed Performance of the Palm Beach Midtown Beach Nourishment Project Figure 2: Alternative E Beach Fill Distribution and Performance Estimate Based on the Walton & Chiu (1979) Analytical Method Figure 21: Alternative E Fill Layout Figure 22: Alternatives F & G Fill & Groin Layout Figure 23: Computational Grids for the SWAN and Delft3D-FLOW Models Figure 24: Regional Wave Grid Bathymetry Figure 25: ntermediate Wave Grid Bathymetry Figure 26: nitial, 28 Bathymetry over the Local Wave Grid & the Flow & Morphology Grid Figure 27: Offshore Directional Wave Statistics from 1999 to Figure 28: Monthly Offshore Wave Statistics Figure 29: Monthly Variation of Wave Direction Offshore Figure 3: Wave Rose Showing Dec. 28 to Jan. 212 Wave Cases (numbers) and Wave Records (light-colored dots) Figure 31: January 24, 29 Aerial Photograph of the Lake Worth Pier Figure 32: Typical Survey Profiles (R-133) across the Phipps Ocean Park South Borrow Area.52 Figure 33: 26 and 28 Surveys near the Phipps Ocean Park Borrow Areas Figure 34: Hardbottom/Bedrock Elevations Used in the Final Calibration Run Figure 35: Simulated Volume Changes during the Final Calibration Run Figure 36: and Alternative A Bathymetry Comparison Figure 37: Alternative A Flow & Morphology Grid Bathymetry... 6 Figure 38: Volumes Changes Given Alternatives A and B vi COASTAL PLANNNG & ENGNEERNG, NC.

8 Figure 39: Low-Tide Shoreline Changes, Alternatives A and B Figure 4: Volume Changes versus Time Figure 41: nitial Bathymetry for Alternatives B, C, and D (excluding groins or breakwaters). 67 Figure 42: Project-nduced Hardbottom Coverage versus Time Figure 43: Volume Changes Given Alternatives A & C Figure 44: Low-Tide Shoreline Changes, Alternatives A and C Figure 45: Volume Changes Given Alternatives A & D Figure 46: Low-Tide Shoreline Changes, Alternatives A and D Figure 47: Comparative Performance, Alternatives A, C, D, & F Figure 48: nitial Bathymetry for Alternative E Figure 49: Volume Changes Given Alternatives A & E Figure 5: Low-Tide Shoreline Changes, Alternatives A and E Figure 51: nitial Bathymetry for Alternatives F & G (excluding groins) Figure 52: Volume Changes Given Alternatives A & F Figure 53: Low-Tide Shoreline Changes, Alternatives A and F Figure 54: Volume Changes Given Alternatives A & G Figure 55: Low-Tide Shoreline Changes, Alternatives A and G Figure 56: Comparative Performance, Alternatives A, D, F, & G Figure 57: Performance of the Recommended Plan through Year Figure 58: Five Year Low-Tide Shoreline Changes Given the Recommended Plan List of Tables Table 1: South Palm Beach & Lantana Dune Projects... 8 Table 2: Dune Restoration Bid Volumes, Town of Palm Beach (ATM, 29) Table 3: Bathymetric & Topographic Data Sources Table 4: September-December 28 to January 212 Volume Change Rates Table 5: Alternative B-D Beach Fill Volumes... 2 Table 6: Alternative E Beach Fill Volumes Table 7: Alternatives F & G Beach Fill Volumes Table 8: Computational Grid Characteristics Table 9: Dec. 28 to Jan. 212 Wave Climate A Table 1: Tidal Datums, Lake Worth Pier (NOAA, 23) Table 11: Surveys Used to Estimate Hardbottom Outcropping Elevations in Feet NAVD Table 12: Delft3D Calibration Parameters, South Palm Beach, FL Table 13: Volume Changes Based on the Delft3D Model, Years Table 14: Coverage of March 212 Hardbottom at Year 3 Based on the Delft3D Model Table 15: Five Year Project Performance, Recommended Plan Table 16: Five Year Project-nduced Hardbottom Coverage, Recommended Plan Table 17: Low-Tide Beach Width in Front of the Existing Seawalls... 9 Table 18: Comparison of Existing (No-Action, Year ) and Post-Project (Alternative G, Year 3) Average Beach Widths... 9 Table 19: Alternative G Estimated Construction Costs vii COASTAL PLANNNG & ENGNEERNG, NC.

9 Appendix No. List of Appendices 1 Beach Profiles Used to Estimate Observed Erosion Rates 2 Delft3D Model Results Assuming December 28 to January 212 Waves 3 Dry Beach Width in Front of the Existing Seawalls Given the Recommended Plan viii COASTAL PLANNNG & ENGNEERNG, NC.

10 1. NTRODUCTON CENTRAL PALM BEACH COUNTY COMPREHENSVE EROSON CONTROL PROJECT REFORMULATED SHORE PROTECTON ALTERNATVES Due to the effects of recent storms and long-term erosion, the shorelines along the Towns of South Palm Beach and Lantana have been categoried as eroded (see Figure 1 to Figure 3). To restore the shoreline to a moderate beach width, the Central Palm Beach County Comprehensive Erosion Control Project is being developed. Coastal Planning & Engineering, nc. (CPE) has been working with the Palm Beach County Environmental Resources Management (ERM) to develop and assess shore protection alternatives to address beach erosion concerns along the Town of South Palm Beach, the Town of Lantana, and the north end of Manalapan (see Figure 1). The study presented herein builds upon the following series of earlier reports: Coastal Planning & Engineering, nc., 27a. Town of South Palm Beach/Town of Lantana Erosion Control Study, Coastal Planning & Engineering, nc., Boca Raton, FL. Coastal Planning & Engineering, nc., 21. Central Palm Beach County Comprehensive Erosion Control Project, Numerical Calibration of Wave Propagation and Morphology Changes, Coastal Planning & Engineering, nc., Boca Raton, FL. Coastal Planning & Engineering, nc., 211. Central Palm Beach County Comprehensive Erosion Control Project Numerical Modeling of Shore Protection Alternatives, Coastal Planning & Engineering, nc., Boca Raton, FL. Based on the studies listed above, three viable alternatives were previously identified: Alternative 1 This alternative included 13 breakwaters along South Palm Beach, Lantana, and the Rit-Carlton, Palm Beach (R-134 to R '), with placement of 75, cubic yards of trucked fill (see Figure 4). This was the original recommendation for South Palm Beach and Lantana (CPE, 211) prior to inclusion of the Town of Palm Beach. Alternative 2 This alternative included 18 breakwaters and 4 groins between profile R- 132 in the Town of Palm Beach and the Rit-Carlton (R '), with 112, cubic yards of trucked fill (see Figure 5). Alternative 9 This alternative included 16 breakwaters and 9 groins between profile R- 132 in the Town of Palm Beach and the Rit-Carlton (R '), with 112, cubic yards of trucked fill (see Figure 6). The alternative recommended by CPE (211) was Alternative 9, which included the Town of Palm Beach. 1 COASTAL PLANNNG & ENGNEERNG, NC.

11 City of Lake Worth Town of Palm Beach Town of South Palm Beach Town of Lantana PROJECT AREA Town of Manalapan Figure 1: Project Area Location. 2 COASTAL PLANNNG & ENGNEERNG, NC.

12 NOTE: This seawall was replaced in December 29. Figure 2: Damaged Seawall at the Mayfair House Condominium, October 3, 28. NOTE: A seawall was subsequently constructed here in 29 & 21. Figure 3: Damaged Sidewalk at Town of Lantana Public Beach, October 29, COASTAL PLANNNG & ENGNEERNG, NC.

13 X 1 5 South Palm Beach, FL Alternative ,-----,-----'lrT--1'----r;:::========r:::====:::;l ---Shoreline ---Local Streets - Dec. 26 Seawalls - Proposed Structures R c.y. Beach Fill R Q) Ol c: :c t: ("") o:j <{ (j) ca w Ll R ' : 146' : 145' : 145' R : 146' ' : 147' : 146' 144' R ' 144' R ' 62'.. } FL-Eas! NAD83 Easting (feet) X 1d NOTE: ORGNAL FGURE FROM CPE (211) REPORT. Figure 4: CPE (211) Alternative 1. 4 COASTAL PLANNNG & ENGNEERNG, NC.

14 X 1 5 South Palm Beach, FL Alternative ,-----,-----'lrT--1'---r::::========r:::====:::;l ---Shoreline ---local Streets - Dec. 28 Seawalls - Proposed Structures R c.y. Beach Fill +r ' 124' 8.25 ' 121' 117' 8.24 R-133 "'i 111' r 112' r 121' Q) Ol c: :c t: ("") o:j <{ (j) ca w..l ' R-134 : 121' : 118' R ' 145' 146' 145' : 147' ' 146' : : 124' : 14' R ' 125' R-138 : 144' 115' r J 61' FL-Eas! NAD83 Easting (feet) X 1d NOTE: ORGNAL FGURE FROM CPE (211) REPORT. Figure 5: CPE (211) Alternative 2. 5 COASTAL PLANNNG & ENGNEERNG, NC.

15 X 1 5 South Palm Beach, FL Alternative ,-----,-----'lrT--1'---r::::========r:::====:::;l ---Shoreline ---local Streets - Dec. 28 Seawalls - Proposed Structures R c.y. Beach Fill 124' 8.25 ' 121' 117' 8.24 R-133 "'i 111' 112' 121' Q) Ol c: :c t: ("") o:j <{ (j) ca w..l ' R-134 : 121' : 118' R ' 145' 146' J. 145' 114' :135' :136' : 14' 74' : 124' : 14' R ' 125' R-138 : 144' 115' J 61' FL-Eas! NAD83 Easting (feet) NOTE: ORGNAL FGURE FROM CPE (211) REPORT. Figure 6: CPE (211) Alternative 9. 6 COASTAL PLANNNG & ENGNEERNG, NC.

16 t is anticipated that that the Palm Beach sland Beach Management Agreement (BMA) being developed in coordination with the Florida Department of Environmental Protection (FDEP) will not include an erosion control project for South Palm Beach and Lantana. Due to the extensive hardbottom, seawalls, and narrow beaches in this area, an Environmental mpact Statement (ES) is also expected to be required. Accordingly, Palm Beach County is seeking a fill design without breakwaters to last 2 to 3 years, which is the objective of the work described in this report. Using observed erosion rates, standard analytical methods (i.e.: Walton & Chiu, 1979), and the Delft3D modeling package, the report details the following alternatives: A. No Action. B. Original 21 Recommended Plan. As noted earlier, Alternative 9 (Figure 6) was the plan recommended in the CPE (211) alternatives report. However, the Town of Palm Beach segment was subsequently removed from the project area. As such, CPE (211) Alternative 1 (Figure 4) is treated as the Original 21 Recommended Plan (Figure 4). C. 75, Cubic Yards of Fill without Structures. D. 75, Cubic Yards of Fill with Short Groins. E. Fill Able to Last 3 Years without Any Structures. F. Fill Optimied to Minimie Hardbottom mpacts and Maximie Project Life. G. Fill Optimied to Minimie Hardbottom mpacts and Maximie Project Life with Groins. 2. SUMMARY OF THE COASTAL SYSTEM ALONG PROJECT AREA 2.1 General The project area extends from Florida Department of Environmental Protection (FDEP) profile lines R ' to R ' (Figure 1), the majority of which has been designated as critically eroded by FDEP. Upland properties consist of condominiums, the Palm Beach Oceanfront nn, the Town of Lantana Public Beach, and the Rit-Carlton Palm Beach hotel. Along the private properties, most of the beaches are backed by seawalls and revetments, with crest elevations on the order of +12 to +2 feet NAVD. Some of these seawalls have required replacement or repair due to damage associated with chronic erosion (Figure 2). Due to erosion related damages along Lantana Public Beach (Figure 3), the original dunes have been replaced with a seawall. The dry beach widths along the study area are generally narrow, and berm terraces are narrow or absent. The toes of the seawalls, revetments, and dunes are on the order of +4 to +1 feet NAVD. Onshore beach slopes are on the order of 1v:8h. A bar and trough system is present along much of the project area. Trough elevations are on the order of -5 to -12 feet NAVD, with the deeper troughs located near the south end of the project area. Bar elevations are on the order 7 COASTAL PLANNNG & ENGNEERNG, NC.

17 of -1 to -5 feet NAVD, with the shallower bars located near the north end of the project area. Offshore slopes between the bar and trough system and the -45 foot NAVD are on the order of 1v:6h. Below the -45 foot NAVD contour, the offshore slope increases to 1v:2h. Much of the study area is characteried by nearshore hardbottom. The hardbottom is not always continuous along the project area, and is subject to frequent burial and subsequent exposure. Based on recent (28-212) aerial photographs, the present hardbottom areas lie within 3 feet of the shoreline. The hardbottom areas and the shallow bedrock surrounding them are indicative of the limited sand supply along the project area. 2.2 Recent & Future Projects To partly address the eroded conditions along the project area, several dune projects were constructed along Lantana Public Beach and the properties to the north (R-136 to R-137) (see Table 1). n 29 and 21, a seawall was constructed along Lantana Public Beach to protect the restaurant and restroom facilities located on top of the dune (see Figure 7 and Figure 8). The elevation of the seawall is feet NAVD along most its length (Taylor Engineering, 29). Table 1: South Palm Beach & Lantana Dune Projects Date Volume Fill Length (cubic yards) (feet) November 23 1, 1,151 February 25 3,132 1,856 December 25 5,814 1,856 June 27 6,75 1,856 January 28 11, 1,856 January 29 1, 1,856 n addition to the projects above, recent and future projects within the Town of Palm Beach could affect erosion rates and sediment transport along the project area: Between December 21 and February 211, dune restoration projects were conducted at three (3) separate locations within the Town of Palm Beach. Fill distributions based on the bid plans (ATM, 29) appear in Table 2. South of the Lake Worth Pier (R ' to R '), the Palm Beach sland Beach Management Agreement (BMA) will likely include dune restoration every 3 years, with fill volumes on the order of 25, to 3, cubic yards (Weber, 213). A draft permit for the South End Palm Beach (North Reach 8) Restoration project was issued on October 25, 212, which would allow the placement of beach fill from R ' to R ' (FDEP, 212). The volume to be placed would depend on the capacity of the permitted beach fill templates (Figure 9 and Figure 1) at the time of construction (Coastal Systems, 212, p. 4). 8 COASTAL PLANNNG & ENGNEERNG, NC.

18 Figure 7: Seawall under Construction at Lantana Public Beach, March 4, 21 Photo. NOTE: COORDNATES SHOWN HEREON ARE N FEET BASED ON THE FLORDA STATE PLANE COORDNATE SYSTEM, EAST ZONE, NORTH AMERCAN DATUM OF 1983 (NAD83). RTZ-CARLTON LANTANA PUBLC BEACH MPERAL HOUSE SEAWALL N Figure 8: March 3, 212 Aerial Photograph of Completed Lantana Public Beach Seawall. 9 COASTAL PLANNNG & ENGNEERNG, NC.

19 COASTAL S'STMS NTUNAllOHA!.NC.... :.... o.... JnK rw.d-fil-31ai r.: 31:61-1!11' -.o.nisj-'t.cdn 'm1e w no11w. m f'm1 a.-....,.,w...t Figure 9: South End Palm Beach Restoration Plan View. TOWN Of PALM EAOl 951 OLD OKEECHOBEE RQ.6 WEST P>U BEACH, FL 3348 SOUTH END PALM BEACH RESTORATON PROJECT VCNTY 1 COASTAL PLANNNG & ENGNEERNG, NC.

20 Figure 1: South End Palm Beach Restoration July 27, 212 Permit Cross-Sections (Coastal Systems, 212). 11 COASTAL PLANNNG & ENGNEERNG, NC.

21 Table 2: Dune Restoration Bid Volumes, Town of Palm Beach (ATM, 29) Profile Line Fill Length (feet) Fill Distribution (c.y./foot) Fill Volume (c.y.) R ,99 R ,267 16,781 R ,214 16,137 R ,155 9,433 R ,736 R Midtown Total R-95 to R-1 5, ,996 R ,61 R ,5 R ,175 4,465 R ,16 1,92 R ,245 R ,71 R ,33 7,851 R ,217 T ,336 R ,6 T-125. Reach 7 (Phipps) Total R-116 to T-125 8, , COASTAL PLANNNG & ENGNEERNG, NC.

22 Table 2 (continued): Dune Restoration Bid Volumes, Town of Palm Beach (ATM, 29) Profile Line Fill Length (feet) 13 Fill Distribution (c.y./foot) COASTAL PLANNNG & ENGNEERNG, NC. Fill Volume (c.y.) R ,326 5,92 R ,294 5,228 T ,168 4,834 R ,221 4,565 R ,198 4,696 R Town Line 4.4 Reach 8 Total R-129 to Town Line 6, , The BMA may also include an extension of the Phipps Ocean Park (Reach 7) Beach Renourishment project to south to the Palm Worth Condominium (R-125+9') (Weber, 213). 2.3 Sediments Sediments along the native beach are a mixture of quart and carbonate sands. The most recent sand samples over the entire project area were taken by Palm Beach County (1993). While several dune restoration projects have been constructed since that effort (see Table 1), no major beach nourishment projects have been constructed. Thus, the Palm Beach County (1993) samples can still provide a reasonable description of the existing materials on the dry beach, surf one, and submerged profile as a whole. Based on the composite for profile lines R-124 to R- 139 (Palm Beach County, 1993, p. 32), the mean grain sie is approximately.36 mm (1.49 ), with a sorting value of.78, a silt content of.2%, and a carbonate content of 42%. However, it is noted that years of erosion have likely winnowed out the finer sediments from the beach resulting in sediment characteristics that are coarser than they once were. 2.4 Beach Erosion Observed erosion rates and shoreline changes along the study area were based on the profiles shown in Appendix 1. The beach profiles were based on surveys taken in 212, 211, 28, 26, and 24 (see Table 3). Shoreline changes were based on the locations of the Mean High Water Line (+.45 feet NAVD, NOAA, 23). Volume changes were calculated from the landward limit of each survey to the point beyond which the apparent changes were dominated by survey error (see Appendix 1).

23 Table 3: Bathymetric & Topographic Data Sources Date Data Type Location Source Vertical Accuracy (feet) January 212 Beach Profiles R-135 to R-164 FDEP (212).1 to.5 September-November 211 Beach Profiles R-73 to R-135 ATM (212).1 to.5 August-September 211 Beach Profiles R-1 to R-8 R-21 to R-45 FDEP (212).1 to.5 R-6 to R-71 August-October 29 LDAR Palm Beach County USACE (212).5 December 28 High-Density Beach Profiles R-132 to R-143 Sea-Diversified (28).1 to.5 October-December 28 Beach Profiles R-77 to R-135 CPE (29).1 to.5 September 28 Beach Profiles R-13 to R-38 R-6 to R-75 R-135 to R-175 FDEP (212).1 to 2. R-19 to R-24 December 27 LDAR Palm Beach County 31, nc. (28).5 April 26 After-Dredging Phipps Ocean Park (Reach 7) Borrow Area Bean-Stuyvesant (26).5 January-February 26 LDAR Palm Beach County USACE (26).5 June 24 LDAR Palm Beach County USACE (24).5 November 22 LDAR Palm Beach County Tenix (23) Hydrographic Palm Beach County NOAA (26) 1.4 Shoreline and volume changes appear in Figure 11, Figure 12, and Table 4 (Note Figure 12 is also referenced on page 26 to show the erosion rates of Alternative E). Recent changes are based on the 28, 211, and 212 surveys. Changes during years characteried by elevated wave and storm activity are based on the 24 and 26 surveys. Both the shoreline and volume changes suggest that the erosional patterns around the project area are characteried by erosion waves (see also CPE, 27b), or alternating areas of erosion and accretion that move down the beach over time. Although the project area s beaches have grown wider since 28, the long-term trend is erosional (see Figure 11 and Figure 13). Over the beach profile as a whole, the net volume change since 28 is a loss of 13,7 c.y./year between R-135 (Concordia East) and R-139 (Manalapan Town Hall) (see Table 4). The area that appears to be most susceptible to erosion is Lantana Public Beach (R-137), which experienced the highest losses within the project area during the 24 and 25 hurricane seasons. 14 COASTAL PLANNNG & ENGNEERNG, NC.

24 Shoreline Retreat (-) / Advance (+feet/year) Figure 11: Recent Mean High Water (+.45 NAVD) Shoreline Changes. 15 COASTAL PLANNNG & ENGNEERNG, NC.

25 834 March 212 Aerial 834 Recent Volume Changes (Adjusted for Beach & Dune Fills) ---June 24- Feb. 26 (24-25 Hur. Season) Nov. 28to Fall-Winter (Most Recent) (see also p 26) g' 824 :.c 5 ("') C3 822 <( (;) crl LlJ 82 l.l R-134 :. '' ' ' ' ' ' ' ' ' ' ' ' ' ' " '''' '''' '''' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' )' ' '''' ' ' ' + R R R R Easting (feet) Erosion (-) Accretion (+c.y./foot/year) Figure 12: Recent Volume Changes. 16 COASTAL PLANNNG & ENGNEERNG, NC.

26 Table 4: September-December 28 to January 212 Volume Change Rates South Palm Beach to Manalapan, FL Obs. Profile Change Dune Adjusted Change Obs. Profile Change Dune Adjusted Change Profile Beach (c.y./foot/year) Fill (c.y./foot/year) (cubic yards / year) Fill (cubic yards / year) Line Length Above Entire (c.y./foot Above Entire Above Entire (c.y. per Above Entire (feet) ' NAVD Profile /year) ' NAVD Profile ' NAVD Profile year) ' NAVD Profile R ,6-7, ,6 R ,2-3,5 1,7 5-5,2 R R , R R135 to R139 3, , -1,4 3,3 7-13,7 17 COASTAL PLANNNG & ENGNEERNG, NC.

27 PROFLE L NE: 1 35 LOCATON: PALM BEACH CO. N, , s ;;: _j w "' JUNE FEB JAN.212 D STACE:S REFERENC-ED -TO: -. ' ' N = FEET E =' FEET j,,, --r,- --,--- --' DST. (FEET) PROFLE L NE: 1 37 LOCATON: PALM BEACH CO. N, ,.. s > >-- w "- _j w l{) "' JUNE FEB JAN.2 12 DSTNJCES REFERENOED -TO: -: N :i FEET E =' FEET AZ. = 95 DEG j_-, , r----, , DST. (FEET) Figure 13: Representative Profiles at Concordia East (R-135) and Lantana Public Beach (R-137). 18 COASTAL PLANNNG & ENGNEERNG, NC.

28 3. DESGN OF ALTERNATVES A. No-Action Alternative A, the No-Action Scenario, is the default plan and serves as the basis for comparison with other alternatives. Under the No-Action Scenario, no further projects would be constructed by the County. The project area might benefit from littoral drift out of the various projects to the north (see Section 2.2, Figure 9, Figure 1, and Table 2). However: Construction of these projects is not certain. n particular, the Phipps Ocean Beach (Reach 7) Beach Renourishment has not entered the Joint Coastal Permitting process. Excluding the Phipps project, the volumes would be relatively small. t would take several years for the placed materials to reach the project area. Aside from the project discussed in Section 2.2, protection of the upland properties from erosionrelated damages would be provided by the existing seawalls only. The Delft3D model study presented later in this report provides a detailed evaluation of the No-Action Scenario. B. Original 21 Recommended Plan Alternative B includes 13 breakwaters and 75, cubic yards of fill material along the project area (see Table 5). A plan view of the alternative appears in Figure 14, with a typical breakwater cross-section appearing in Figure 15. The development of the breakwaters dimensions and their layout is discussed in the South Palm Beach/Lantana Joint Coastal Permit Draft, Appendix A dated March 9, 29 (CPE, 29). This draft document summaries the methodology by which the breakwaters were designed. Based on the analytical/empirical methods used in the draft permit application (CPE, 29), the volumetric impact to the beach and dune system resulting from the structures salients fill would be 75, cubic yards. The amount of fill that would have been placed under this alternative is equal to that volume. As noted earlier, the County is now seeking a fill design without breakwaters to last 2 to 3 years. Thus, the primary purpose of evaluating Alternative B is to compare the performance and impact of the study alternatives to the plan that was originally developed. The Delft3D model study presented later in this report provides a detailed evaluation of Alternative B in comparison to the No-Action Scenario and the other alternatives discussed below. 19 COASTAL PLANNNG & ENGNEERNG, NC.

29 Table 5: Alternatives B, C and D Beach Fill Volumes 75, c.y. with & without Breakwaters or Groins Direct Hardbottom Construction Beach Fill Density Profile Line 1 Fill Length Coverage 2 Berm Width Volume (feet) (acres) (feet) (c.y./foot) (c.y.) R ' R ' , ,8 R ,5 R ,4 R ' ,2 R N ,3 R ,6 R ' ,6 R ,5 R ' ,3 R '. South Palm Beach Segment 2, ,5 R ' to R ' (excl. breakwaters) Lantana Segment ,1 R ' to R ' (excl. breakwaters) Manalapan Segment ,4 R ' to R ' (excl. breakwaters) TOTAL (ALT. C & D) 4, , (excl. breakwaters) Breakwater # (acres) 3 #1 to #9. # 1, E = 97929', N = '.8 # 11, E = 97933', N = 81996'.19 # 12, E = 97915', N = '.15 # 13, E = 9788', N = '.3 Hardbottom Coverage by Breakwaters.45 (Structure Footprint) Alt. B Hardbottom Coverage 1.56 (ncluding Breakwaters and Fill) 1 Fill Length, Direct Hardbottom Coverage and Beach Fill Volume are representative of values between two profile lines, the rows are aligned as such and shaded light grey. Berm Width and Density are reported at each the profile line. 2 Based on the March 212 hardbottom mapping. Values do not include hardbottom covered directly by structure footprint. 3 Alternatives B, C and D have the same fill design. The hardbottom covered by fill is the same for Alt. B, C and D. The footprint of the breakwaters in Alt. B contributes to additional hardbottom coverage. 2 COASTAL PLANNNG ENGNEERNG, NC.

30 NOTES: 1. ALTERNATVE C DOES NOT NCLUDE BREAKWATERS. 2. DATE OF AERAL PHOTOGRAPH: 3/3/ GRAPHC SCALE N FT Figure 14: Alternative B & C Fill Layout. (Note - Fill distribution is the same for Alternatives B and C) 21 COASTAL PLANNNG & ENGNEERNG, NC.

31 COASTAL PLANNNG & ENGNEERNG, NC. 22 Figure 15: Typical Breakwater Cross-Section, Alternative B (CPE, 29). c G) > (/) ;::: > :-o!"'' p (Q "' (Q > itl T"' 'Z oo Al-l ONSHORE OFFSHORE :;u""t] fto C):;u c: rn >O r--12'-l -iz Dill 1+4. FT. NAVO :;uc: ft SO FT. NAVD rrl =e fl!ii O p FT. -8. FT. NAVD MHW.4-4 FT. MLW FT. NOTE: 1. ELEVATONS ARE N FEET REFERENCED TO NORn-t AMERCAN VERTCAL DATUM OF 1988 (NAVDBB). 2. FOUNDATON DESGN MAY BE MODFED DUE TO PRESENC QF.EXSTNG LfMESTQN..E SUBSTRATE. COASTAL P.ANNNG ENGNEEUNG, NC. GEOTEXTLE AROR FABRC STONE r ' J'(p!CAL BREAKWATER CROSS SECDON B-B' P ll.ivl]a14fig:l rj51t]mi.clt e.c.t... n. a e.c A.A.D l llle: CENTRAL PALM BEACH COUNTY COMPREHENSVE EROSON CONTROL PROJECT TYPCAL BREAKWATER PROFLE B-B'

32 C. 75, Cubic Yards of Fill without Structures Alternative C includes a uniform fill layout of 75, cubic yards (see Table 5), similar to Alternative B (see Figure 14). The primary purpose of evaluating Alternative C is to determine: The feasibility of constructing a project similar to Alternative B without breakwaters, with specific attention to the longevity of the beach fill. The contribution of the breakwaters to the performance and impact of Alternative B. The performance of Alternative C is detailed in the Delft3D study, which appears later in this report. D. 75, Cubic Yards of Fill with Short Groins Alternative D includes a uniform fill layout of 75, cubic yards similar to Alternatives B & C (see Table 5). However, to stabilie the fill, the alternative includes a number of strategically placed groins. The groins will be constructed using King Pile-and-Panel construction, similar to the design presented in the CPE (211) alternatives report. The crest elevation of each groin will follow the existing grade elevations, and will range from -3 to +2.2 feet NAVD (see Figure 16). The groin layout is based on the location of the recent erosion and the erosion that could occur over the next 3 years based on the Delft3D model. As shown in Figure 12, the area between R and R-138 has been erosional since 28. The Delft3D model results, presented in this report, also suggest that over the next 3 years, this area will continue to erode. To stabilie the beach fill along this area, groins could be constructed from the existing seawall to the postconstruction water line (see Figure 17). The resulting lengths would range from 85 to 145 feet, depending on location. The distances between the groins would be roughly equal to 3 times their average length. The length to spacing ratio is similar to the one used in the initial Erosion Control Study (CPE, 27a). The overall performance of Alternative D is detailed in the Delft3D study. 23 COASTAL PLANNNG & ENGNEERNG, NC.

33 COASTAL PLANNNG & ENGNEERNG, NC. 24 Figure 16: Typical Alternative D & G Groin Cross-Section Based on CPE, 211. c r.n ;::: > :u!"1 p N (g it.., oo Al-j ;u.., TTO G');g c rn >O -iz Dill Al-i -(AJ c: Alo TT::::j So TTi :1: r -( TTl.::::1 - f.., TTl l2-r B 4 < > -4 -, EXSTNG SEAWALL ' TOP EL= 12.5' NAVD PROPOSED KNG PLE AND PANEL GRON EXSTNG PROFLE FROM TAYLOR ENGNEERNG, NC. SEAWALL CONSTRUCTON ASBULTS 'POTENT'Al 'R'ANGE Of ' BEACH PROFLE SEAWARD OF GRON t.1hw =.44 FT. NAVD t r<<<<«fe<'?tsjsss )(.ix l \ ', POTENTAL HARDBOTTOM MPACT AT THE GRON -, o o o o o o o... o o o o t o t o o 28 AERAL HARDBOTOM 28 SURVEY HARDBOTOM -12-r r T T ; DSTANCE FRO SEAWALL (FEET) GRON CROSS SECDON 2 - Bl :11> " Z. - p CM,STA.L PlANNNG &. t:ngnt:t:.. NG, NC. ::1»1 ll.. KCA, R,.JD DU.. EV&flll' KA,tA"'J(lH, fullll.. 1M31 t':lll8--l!t P H, jm1]3ri_.ut:! fl«jllt]' C.(! A. JLillfll«lt CflA_A_.112D l iue: CETRAL PAU BEACH COUNTY COMPREHENSVE EROSON CONTROL PROJECT GRON CROSS SECTON

34 DATE OF AERAL PHOTOGRAPH: 3/3/ GRAPHC SCALE N FT Figure 17: Alternative D Groin & Fill Layout. 25 COASTAL PLANNNG & ENGNEERNG, NC.

35 E. Fill Able to Last 3 Years without Any Structures The intent of Alternative E is to place enough fill to last 3 years. The erosion rates upon which the fill design is based are shown using the thin, black line in Figure 12. These rates are equal to the maximum of the 28 to 211/212 erosion rates or the 24 to 26 erosion rates. As noted by Dean (1992) and Campbell (1992), beach fills have a tendency to spread in the longshore direction. The losses associated are known as end losses, and cause restored beaches to erode faster than beaches that have not been nourished (Campbell, 1992). End losses given Alternative E are based on the analytical method of Walton and Chiu (1979). This method is also detailed in Dean (1992). For a rectangular beach fill of uniform width, the spreading of fill, excluding background erosion, may be described by: y Y 2 x 1 erf a 2 a x 1 erf Kt a 2 a Kt K = 2C 1 H b 5/2 / d where C 1 1/ 2 C' SPM (g / ) = H b / d b 16(G 1)(1 p) s y = fill width assuming an equilibrium beach profile Y = initial uniform fill width assuming an equilibrium beach profile x = longshore distance from the center of the beach fill a = half the fill length t = time elapsed since construction H b = breaking wave height d = berm elevation depth of closure elevation g = 32.2 feet/second 2 G s = density of sand solids divided by density of water 2.65 p = porosity of sand.37 C spm = empirical constant.128 (Walton and Chiu, 1979, p. 811) d b = breaking wave depth For multiple beach fills, results from the equation above can be superimposed: w(l, t) where N y(x i,y i,a i,k, t) S(L) t i 1 w = total beach width relative to present conditions L = distance along the beach x i = distance from the center of beach fill i 26 COASTAL PLANNNG & ENGNEERNG, NC.

36 Y i = initial fill width of beach fill i a i = half the fill length of beach fill i S = background shoreline change rate (+ advance / retreat) For a non-uniform beach fill, the fill layout can be divided into N individual beach fills with an a i value of L/2 and a Y i value of w(l, t=). Figure 18 illustrates the application of the discrete solution for a triangular beach fill, a layout for which an analytical spreading solution is also available (Walton and Chiu, 1979). (Background shoreline change = feet/year) Figure 18: Comparison of the Discrete and Analytical Solutions for a Triangular Beach Fill. The Walton and Chiu (1979) method utilies several parameters that are site-specific. The density of the sand solids is based on a typical value for sands, G s = Likewise, a typical porosity value of 37 percent (p =.37) is assumed. The berm elevation is set to +8.4 feet MSL (+7.5 feet NAVD), and a foot MSL (-23.5 feet NAVD) depth of closure is assumed (see CPE, 27b, 2). The breaking wave height and corresponding depth were based on the measurements at the Lake Worth Pier (USACE, 1991; CPE, 27b). Given the entire record, the root mean square wave height was 2.2 feet, with a peak period averaging 7.3 seconds and an energy propagation vector averaging 75 degrees (east-northeast). This wave was then refracted from the 27 COASTAL PLANNNG & ENGNEERNG, NC.

37 nominal gage depth of 33 feet to the breaking depth of 3.4 feet using ACES (Leenknecht, et al, 1992). The breaking wave height was 4.3 feet. The value of C spm was based on the performance of the Palm Beach Midtown Beach Nourishment Project. This project was chosen due to its long period between the initial construction and the first renourishment ( ) and its previous analysis by CPE (27). As a first approximation, the project was treated as a rectangular beach fill. The value of C spm was then determined by comparing the calculated and observed volume left in the project area (R-95C to R-1) over the project duration ( ) (Figure 19). The resulting value of C spm was.177, which was on the same order of magnitude as the typical value of.128 (Walton and Chiu, 1979, p. 811). PREDCTED AND OBSERVED PERFORMANCE OF THE PALM BEACH MDTOWN BEACH NOURSHMENT PROJECT 1% 9% 8% 7% 6% 5% 4% 3% 2% 1% % Jan 1996 Jan 1997 Jan 1998 Jan 1999 Jan 2 Jan 21 Remaining Fill by Volume (%) Jan 22 Jan 23 Jan 24 Excluding Background Retreat ncluding Background Retreat Observed Figure 19: Predicted and Observed Performance of the Palm Beach Midtown Beach Nourishment Project. Using the analytical method outlined above, a beach fill layout was developed, with enough fill to prevent significant erosion into the pre-construction cross-section between Year and Year 3 (see Figure 2, Figure 21, and Table 6). Fill quantities are equal to the amount of erosion based on the design erosion rates (Figure 2, dashed line and Table 6, columns 5-6) plus additional fill to account for end losses (Table 6, column 7). The total fill volume is 16,6 cubic yards. Fill performance based on the Delft3D model is presented later in this report. 28 COASTAL PLANNNG & ENGNEERNG, NC.

38 March 3, 212 Aerial Photograph Alt. E Walton & Chiu (1979) Analytical Performance Estimate nitial Fill (Year ) Year 3 Without Project Year 3 With Project v Cl : <( 819 ll v Cl : <( J ll Easting (feet) Remaining Volume (c.y./foot) Figure 2: Alternative E Beach Fill Distribution and Performance Estimate Based on the Walton & Chiu (1979) Analytical Method. 29 COASTAL PLANNNG & ENGNEERNG, NC.

39 DATE OF AERAL PHOTOGRAPH: 3/3/ GRAPHC SCALE N FT Figure 21: Alternative E Fill Layout. 3 COASTAL PLANNNG & ENGNEERNG, NC.

40 Table 6: Alternative E Beach Fill Volumes Fill Able to Last 3 Years Without Any Structures Direct Construction Design Profile Fill Hardbottom Berm Volume Fill Distribution Fill Line 1 Length Coverage 2 Width Change Rate 3 Base Spreading Total Volume (feet) (acres) (feet) (c.y./foot/year) (c.y./foot) (c.y./foot) (c.y./foot) (c.y.) R ' R ' , ,9 R ,3 R ,1 R ' ,3 R N R S ,8 R ,5 R ' , R , R ' R ' South Palm Beach Segment 2, ,2 R ' to R ' Lantana Segment ,6 R ' to R ' Manalapan Segment ,8 R ' to R ' TOTAL 4, ,6 NOTES: 1 Values in rows above are aligned to represent quantities between profile lines or at profile lines. 2 Based on the March 212 hardbottom mapping. 3 Design volume change rate (-erosion) is the more severe of the June 24 to Feb. 26 and the Dec. 28 to Jan. 212 rate. 31 COASTAL PLANNNG ENGNEERNG, NC.

41 F. Fill Optimied to Minimie Hardbottom mpacts and Maximie Project Life Alternative F includes a fill volume similar to Alternatives B-D. However, to reduce the degree of hardbottom coverage (compare Table 5 versus Table 7) and improve project performance versus Alternative C, the fill is concentrated in the area of highest erosion towards the middle of the project area. As detailed later, the Delft3D modeling results suggest that the strategic arrangement of fill improves the performance of the project between the Palm Beach Oceanfront nn (R-135.5) and the mperial House (R-136.5). This section of the project area is likely to experience the greatest degree of erosion under the No-Action scenario. A plan view of the fill layout appears in Figure 22. G. Fill Optimied to Minimie Hardbottom mpacts and Maximie Project Life with Groins Based on the performance of Alternatives D and F, an additional alternative was formulated using groin layout of Alternative D and the fill layout of Alternative F (see Table 7 and Figure 22). The estimated performance and impact of Alternative G is detailed in the Delft3D modeling study. 32 COASTAL PLANNNG & ENGNEERNG, NC.

42 Table 7: Alternatives F & G Beach Fill Volumes Fill Optimied to Minimie Hardbottom mpacts and Maximie Project Life with & without Groins Direct Construction Profile Fill Hardbottom Berm Fill Fill Line Length Coverage* Width Distr. Volume (feet) (acres) (feet) (c.y./foot) (c.y.) R ' R ' ,82.1 1,8 R ,8 R ,4 R ' ,3 R N R S ,5 R ,2 R ' , R ,1 R ' ,4 R ' South Palm Beach Segment 2, ,5 R ' to R ' Lantana Segment , R ' to R ' Manalapan Segment ,5 R ' to R ' TOTAL 4, , * Based on the March 212 hardbottom mapping. 33 COASTAL PLANNNG & ENGNEERNG, NC.

43 NOTES: 1. ALTERNATVE F DOES NOT NCLUDE GRONS. 2. DATE OF AERAL PHOTOGRAPH: 3/3/ GRAPHC SCALE N FT Figure 22: Alternatives F & G Fill & Groin Layout. (Note - Fill distribution is the same for Alternatives F and G) 34 COASTAL PLANNNG & ENGNEERNG, NC.

44 4. DELFT3D MODELNG STUDY 4.1 General The performance and impact of each alternative was evaluated using the Delft3D morphological model (Deltares, 211a). This model determines changes in a topographic and bathymetric surface based on the effects of waves, water levels, winds, and currents. Wave transformation from the offshore to the nearshore area is simulated using the SWAN wave transformation model (Booij, et al, 24). The SWAN model (version 4.72ABCDE) is coupled with the Delft3D- FLOW model (version ), which simulates currents, water levels, and sediment transport. Based on the sediment transport estimates at each flow time step, the Delft3D-FLOW model calculates the subsequent elevations of the topographic and bathymetric surface. Typical time steps in Delft3D-FLOW range from 1 second to 6 seconds. Water levels, currents, and bottom grade elevations are then sent to the SWAN model at each wave time step, which is on the order of.5 to 3 hours. 4.2 Updated Model Calibration Calibration of the SWAN model was performed using wave measurements collected near the project site in 28. Details regarding the SWAN model calibration appear in CPE (21). The flow parameters used in the Delft3D-FLOW model were set to the values recommended by Deltares (211a) as detailed in Appendix 2 of CPE (21). Sediment transport, erosion, and deposition within Delft3D-FLOW were initially calibrated using bathymetric surveys taken in 26 and 28 (CPE, 21). This phase of the calibration was heavily tied to the hardbottom conditions that existed in 26 (see CPE, 21, pp ). As noted in the initial calibration report and other sources (CPE, 27b), the extent of the exposed hardbottom near the project area is highly variable. Given these factors, the sediment transport, erosion, and deposition parameters in the model were recalibrated based on the volumetric erosion rates between December 28 and January 212 (Figure 12) Grids Four different computational grids were created for numerical model calibration and production simulations (Figure 23). These grids were created for the following purposes: Regional Wave Grid. This grid was designed to propagate wave characteristics from deep water to intermediate-shallow water and examine regional wave transformation processes. ntermediate Wave Grid. This grid was designed to transform waves between the coarsely-spaced, Regional Wave Grid and the local, high resolution wave grid. The ntermediate Wave Grid was nested within the Regional Wave Grid. 35 COASTAL PLANNNG & ENGNEERNG, NC.

45 9 Wavewatch Hindcast Node N, W + > c: :.c t:: (") co <( iii ro w..j ll Regional Wave Grid --ntermediate Wave Grid --Local Wave Grid Flow & Morphol Grid FL-East NAD83 Easting (feet) Figure 23: Computational Grids for the SWAN and Delft3D-FLOW Models. 36 COASTAL PLANNNG & ENGNEERNG, NC.

46 Local Wave Grid. This grid was designed to examine detailed, shallow water wave propagation processes. This nearshore grid was nested within the ntermediate Wave Grid. The central area of this grid was created with sufficient resolution to simulate the refraction, diffraction, and breaking processes near the coastal structures being evaluated. The offshore boundary of the nearshore wave grids followed the -61 foot NAVD depth contour. Flow & Morphology Grid. This grid was designed to examine circulation patterns and bathymetric changes in the project area and the adjacent beaches. This grid was merged along several rows of grid cells along the northern, southern, and eastern edges of the grid to provide for a stable coupling between the SWAN and Delft3D-FLOW models. All 4 grids were constructed in Cartesian coordinates based on the Florida State Plane Coordinate System, East Zone, North American Datum of 1983 (FLE-NAD83). Grid characteristics are summaried in Table 8: Table 8: Computational Grid Characteristics Regional Wave ntermediate Flow & Local Wave Grid Grid Wave Grid Morphology Grid Grid Sie (cells) 36 x x x x 65 Grid Spacing (feet) 61 to 1, to to to 392 The Local Wave Grid and the Flow & Morphology Grid were refined near the project area to provide sufficient resolution to simulate the flow patterns and the circulation processes inside the wave breaking one. The Delft3D-Flow model was run in 3D mode with five vertical layers. Since the model was primarily a shallow water model, the layering was schematied using sigma coordinates based on the percentage of the water depth at each time and grid point. The model s developer has established guidelines for computational smoothing and orthogonality. The smoothing represents the change in cell sie between two rows of grid cells. A smoothing value of 1.1 indicates that the cell sie between two rows of grid cells increases by 1%. The maximum smoothing value recommended by the model s developer is 1.2. The orthogonality is equivalent to the angle between the longshore and cross-shore grid lines. The angles between the longshore and cross-shore grid lines should be at least 87.7 degrees. All 4 grids follow the guidelines for smoothing and orthogonality nitial Bathymetry The initial bathymetry over each grid was based on the December 28 survey as the primary data source. Grid points outside the December 28 survey limits were filled using the older data sources, beginning with the other 28 surveys, followed by the 27 Light Detection and Ranging (LDAR) survey, the 26 surveys, the 22 LDAR survey, and the hydrographic survey (see Table 3). The datum used for each grid surface was the North 37 COASTAL PLANNNG & ENGNEERNG, NC.

47 American Vertical Datum of 1988 (NAVD). following: Conversions to NAVD were based on the For the 22 LDAR survey and the 26 borrow area survey, the National Geodetic Vertical Datum of 1929 (NGVD) was assumed to be equal to feet NAVD (NOAA, 23). For the hydrographic offshore, the average value of the Mean Lower Low Water datum was feet NAVD based on the NOAA (212) VDATUM 3.1 conversion program. The horiontal conversion between latitude/longitude and FLE- NAD83 coordinates was performed using Corpscon The initial bathymetry over each grid appears in Figure 24 through Figure 26. Bathymetry over the Local Wave Grid and the Flow & Morphology Grid was updated based on the estimated sediment transport. Bathymetry over the Regional Wave Grid and ntermediate Wave Grid was assumed to be constant with time Waves Waves in this study were primarily based on the NOAA (213) WAVEWATCH hindcast for the Western North Atlantic. The hindcast data was provided in the form of grids covering the Atlantic coast of North America from 1999 to 212. Similar to the original calibration (CPE, 21), the WAVEWATCH waves used in the Delft3D model were taken from the forecast at 26.5ºN, 79.75ºW (see Figure 23). The depth at this site was -1,488 feet NAVD. The highest and longest waves during average conditions occur between September and January, with the lowest and shortest waves occurring between June and August. Between June and August, waves from the east and east-southeast are common. During the rest of the year, waves typically originate from the northeast. The root-mean-square wave height is on the order of 4. feet, with an average peak period of 6.8 seconds and an average direction of 43 degrees (from the NE). Overall, 7 percent of the wave energy originates from the northerly direction bands ( degrees), 8 percent of the wave energy originates from the east, and 19 percent of the wave energy originates from the southerly direction bands (112.5 to 18 degrees). Directional wave statistics appear in Figure 27. Monthly wave statistics appear in Figure 28 and Figure 29. Two- and three-dimensional sediment transport and morphology models are computationally intensive. Furthermore, while flows change on an hourly basis, the morphology changes occur on a scale of months to years. For this reason, it is not practical to simulate 3-4 years of volume changes using a 3-4 year time series of offshore water levels and waves to drive the model. nstead, the Delft3D model is typically run for a shorter period of time, using 1-3 wave cases to approximate the general wave climate during the period of interest (i.e.: Lesser, et al., 24; Benedet and List, 28). The number of wave cases, and their characteristics, are chosen to produce sediment transport patterns that would be similar to those based on the full time series of offshore waves (i.e. 3-4 years). 38 COASTAL PLANNNG & ENGNEERNG, NC.

48 Regional Wave Grid Bathymetry through Dec. 28 (feet NAVD) Ol c 83 C') ex:> 82 u; <ll w...:, 81 L.L FL-Eas! NAD83 Easting (feet) Figure 24: Regional Wave Grid Bathymetry. 39 COASTAL PLANNNG & ENGNEERNG, NC.

49 ntermediate Wave Grid Bathymetry through Dec. 28 (feet NAVD) l82sooo Ol c E t: ("') a:> <{ 82 v; «! w ll FL-East NAD83 Easting (feet) -35 Figure 25: ntermediate Wave Grid Bathymetry. 4 COASTAL PLANNNG & ENGNEERNG, NC.

50 PHPPS OCEAN PARK BORROW AREAS Figure 26: nitial, 28 Bathymetry over the Local Wave Grid & the Flow & Morphology Grid. 41 COASTAL PLANNNG & ENGNEERNG, NC.

51 Percent Occurrence Maximum Hs (feet) ---Maximum Tp (seconds) ' 5.fl ' ' / ' '' ' '... ' ' ',,,, ,,,,, ' \ RMS Hs (feet) ' Average Tp (seconds) Figure 27: Offshore Directional Wave Statistics from 1999 to 28 (Location: N, W, NAVD). 42 COASTAL PLANNNG & ENGNEERNG, NC.

52 MONTHLYWAVE STATSTCS N, W, -1488' NAVD, PA LM BEACH COUNTY, FL 8.,----,,----,----,-----, ,-----,----,-----,----, ;< =.96u<B, r ' ,... )!( ' 2 ' r _'J =--b r s.o"- 4 r:... --o... d. d " " r r r r r Jan. Feb. March April May June July Aug. Sep. Oct. Nov. Dec. RMS Sign. Wave Height (feet) - Avg. Peak Wave Period (seconds) MONTHLYWAVE STATSTCS N, W, -1488' NAVD, PA LM BEACH COUNTY, FL J\ /,+--\ r r r---, l+- / t". -r _ 1! 4, 15.o r r /;""_8"'!-""' -,---+"" ----=""'-=- -"'---- ==+--_p-- =...,.(,-+_ J_-r..., _ 1 _ \5. : 1 ; ,- '" 1 1/ "- K2 - v = cr \'3 '.3..._,., r r Jan. Feb. March April May June July Aug. Sep. Oct. Nov. Dec. -<>-Maximum Wav e Height(feet) '- Maximum Peak Wave Period (seconds) Figure 28: Monthly Offshore Wave Statistics. 43 COASTAL PLANNNG & ENGNEERNG, NC.

53 Figure 29: Monthly Variation of Wave Direction Offshore. The offshore wave climate during the calibration period was based on the time series of WAVEWATCH waves at N, W between December 28 and January 212. The primary wave cases were selected from the waves originating from the seaward direction bands ( to 18 ), which covered 82 percent of the wave record by time. These wave records were divided into wave height and direction classes, with each wave class containing an equal amount of wave energy (in KW-Hours/m or Joules/m). This method, known as the Energy Flux Method, characteried each wave record based on the energy flux: P = EC g = wave energy in watts per m Energy per wave record (Joules per m) = P t where: E = gh s 2 = wave energy in Joules per m 2 (3,6, Joules = 1 KW-hour) C gn = (1/2) (L/T p ){ 1 + [(4 d/l)/sinh(4 d/l)] } = group wave velocity in m/s 44 COASTAL PLANNNG & ENGNEERNG, NC.

54 L = [gt p 2 /(2 )] tanh(2 d/l) = wavelength in m and: = seawater density = 1,25 kg/m 3 (63.99 lbm/foot 3 ) g = gravity = 9.81 m/s 2 (32.2 feet/s 2 ) H s = significant wave height in m T p = peak wave period in seconds d = depth = 453 m (1,488 feet) t = interval between wave records = 1,8 seconds (3 hours) Based on the energy estimates above, the offshore waves ( to 18 ) were divided into 3 height classes with roughly equal amounts of wave energy in KW-Hours/m. Each height class was then divided into 4 direction bands representing equal amounts of wave energy, for a total of 12 wave cases (see Table 9 and Figure 3). To account for periods during which the offshore waves were propagating from the landward directions (18 to 36 ), a 13 th wave case was added, representing calm conditions. Excluding the calm case, each wave case at N, W represented a nearly equal amount of wave energy. However, since higher, more energetic waves occurred less often than lower waves, the various wave cases did not represent an equal portion of the wave record with respect to time (% occurrence). Directional spreading values offshore were assumed to be equal to the model s default value of 25 degrees. The wave measurements taken in 28 did not support the use of narrower directional spreading values for medium or long-period (T p > 5 sec.) waves. To decrease the time needed for the morphological computation, morphological acceleration factors were used, as described in Lesser et al (24) and Benedet and List (28). The morphological acceleration factor M was estimated according to the following: M = T study period / T model period where T study period = (length of the study period) x (percent occurrence for each wave case) T model period = duration of the wave case in the model simulation For example, a wave case that occurs 14 days a year can be simulated over 24 hours with an M value of 14. With the Delft3D modeling community, it is common practice to use lower M values for high wave cases, when the most significant morphological changes occur, and higher M values for smaller wave cases, where little change takes place. Over the calibration period, the values of T model period were equal to the following: Calm Case and Wave Cases #1 to #4: 9 tide cycles (3 per year), hours. Wave Cases #5 to #8: 6 tide cycles (3 per year), 74.4 hours. Wave Cases #9 to #12: 3 tide cycles (1 per year), 37.2 hours. 45 COASTAL PLANNNG & ENGNEERNG, NC.

55 Table 9: Dec. 28 to Jan. 212 Wave Climate A 26.75ºN, 79.75ºW, -1,488 feet NAVD Central Palm Beach County, FL Case # RMS Sign. Wave Height (feet) Avg. Peak Wave Period (sec.) Avg. Peak Wave Direction (deg.) Avg. Wind Speed (mph) Avg. Wind Direction (deg.) % Occurrence Height Class (feet) Direction Band (deg.) Month Freq. Month Dec. 28 to Jan. 212 Morphological Accel. Factor 5-Year Morphological Accel. Factor % 1. to 4.6 to 35 Dec % 1. to to 44 Dec % 1. to to 55 Dec % 1. to to 18 Dec % 4.6 to to 27 Dec % 4.6 to to 37 Jan % 4.6 to to 43 Feb % 4.6 to to 178 Dec % 6.7 to to 3 Jan % 6.7 to to 38 April % 6.7 to to 41 March % 6.7 to to 176 Nov CALM % All Remaining Waves July COASTAL PLANNNG & ENGNEERNG, NC.

56 Figure 3: Wave Rose Showing Dec. 28 to Jan. 212 Wave Cases (numbers) and Wave Records (light-colored dots). The resulting values of the morphological acceleration factor during the calibration period (28 to 212) appear in Table 9 (second-to-last column). To account for seasonal variations in wave height and direction, the following steps were taken: 1. Within each wave case, the month representing the greatest number wave records was identified (see Table 9). t should be noted that the most frequent month is a general trend, not an absolute rule. Calm conditions in December are possible, along with sediment transport reversal conditions (Case #4) in July. 2. Based on the most frequent month listed in Table 9, the wave cases were sequenced in the following order, beginning and ending with the December wave cases: Case #4, Case #5, Case #1, Case #6, Case #9, Case #7, Case #11, Case #1, Calm conditions, Case #12, Case #8, Case #2, and Case #3. This sequence of wave cases was repeated 3 times to represent the 3 approximate years covered by the calibration period Winds Winds during the calibration period (Dec. 28 to Jan. 212) were based primarily on hourly measurements at the Lake Worth Pier ( ' N, 8 2' W). Gaps in the record were filled using hourly measurements at Palm Beach nternational Airport ( 47 COASTAL PLANNNG & ENGNEERNG, NC.

57 land-based-station-data/find-station). Wind velocities for each wave case were then averaged based on the concurrent wind records during each wave case (see Table 9) Water Levels Water levels during the calibration period were based on the tidal datums at the Lake Worth Pier ( ' N, 8 2' W, see Table 1). Tides at this location were semi-diurnal, with amplitudes averaging 1.4 feet. Table 1: Tidal Datums, Lake Worth Pier (NOAA, 23) TDAL DATUM ELEVATON TDAL DATUM (feet (feet (feet NGVD) NAVD) MLLW) Mean Higher High Water (MHHW) Mean High Water (MHW) North American Datum of 1988 (NAVD) Mean Tide Level (MTL) National Geodetic Vertical Datum of 1929 (NGVD) Mean Low Water (MLW) Mean Lower Low Water (MLLW) As detailed above, the waves used as input were given in the form of wave cases representing long-term averages. Accordingly, water levels were schematied using a simple, sine-wave tide with a period of 12.4 hours and an amplitude of 1.4 feet based on the vertical difference between MHW and MLW Hardbottom and Bedrock Hardbottom was incorporated into the model by varying the erodible sediment depth. To develop the erodible sediment depth, the following steps were taken: 1. The hardbottom database was acquired from the Palm Beach County Environmental Resources Management Department. This database was distributed in the form of a Shape File outlining hardbottom areas appearing in the 1993, 2, 21, 23, 24, 25, 26, 27, 28, and 29 aerials. Blue Kenue was used to convert the hardbottom information into a plain-text file listing the years and coordinates of each outcropping. 2. To supplement the information above: a. Post-Hurricane Jeanne hardbottom areas were digitied from aerial photographs taken in January 25 and March COASTAL PLANNNG & ENGNEERNG, NC.

58 b. Nearshore hardbottom areas were digitied from December 22 aerials provided by the U.S. Geological Survey (USGS) Earth Explorer. These hardbottom areas were combined with 22 offshore hardbottom mapping provided by the Florida Fish and Wildlife Conservation Commission (FFWCC, c. The 1993 hardbottom mapping from FFWCC was combined with the 1993 hardbottom mapping from the Palm Beach County database. d. The March 212 hardbottom mapping was digitied from March 212 aerial photographs flown by Aerial Cartographics of America on behalf of the Town of Palm Beach and FDEP. The quality of the photographs and the water clarity during the flight date was sufficient for this purpose (for example, see Figure 14). Although the Town of Palm Beach was the sponsor of these photographs, they provided full coverage of the model grids shown in Figure 26, including the project area. 3. Concurrent bathymetries over the Flow & Morphology Grid from 1993 to 29 were estimated based on the surveys listed in Table 11. For each year s mapping, grid points within the respective hardbottom areas were identified. The elevations of the exposed hardbottom areas at those grid points were then estimated based on the concurrent survey. For example, the elevations of the exposed hardbottom in 22 were based on the bathymetric grid surface drawn from the November 22 LDAR survey. Table 11: Surveys Used to Estimate Hardbottom Outcropping Elevations in Feet NAVD. Hardbottom Closest Survey Date(s) Survey Data Sources* Mapping 1993 July-October 199 FDEP - PB98_CCC_1.PRF 2 Fall-Winter 2-21 FDEP - PB12_MAE_1.PRF 21 August 21 FDEP - PB19_MAE_1.PRF 22 Nov. 22 LDAR Tenix (23) 24 June 24 LDAR USACE (24) Jan.-March 25 (Post-Jeanne) Nov. 24 LDAR USACE (24) 25 May-Aug. 25 CPE (25) FDEP - PB57_MAE_1.PRF 26 May 26 Project Area April 26 R124 to R134 Nearshore Jan.-Feb 26 Remaining Areas Sea Diversified (26) Bean-Stuyvesant (26) USACE (26) 27 May-Sep. 27 CPE (27d) FDEP - PB79_MAE_1.PRF 28 Sep.-Dec. 28 Sea Diversified (28) CPE (29) FDEP - PB89_BL_1.PRF 29 October 29 FDEP - PB99_BL_1.PRF 212 Jan. 212 & FDEP - PB119_SD_1.PRF September-November 211 ATM (212) *NOTE: The FDEP surveys are taken from the FDEP Historic Shoreline Data / Profile Data database, ftp://ftp.dep.state.fl.us/pub/water/beaches/hssd/profiledata/prof83988/ PALPZ.ZP. 49 COASTAL PLANNNG & ENGNEERNG, NC.

59 4. n many areas, hardbottom outcroppings were visible in 2 or more sets of aerial photographs. As a result, many grid points had several values associated with the hardbottom elevation, not just one. Thus, two different variations of the bedrock elevation were estimated in feet NAVD one based on the average, estimated hardbottom elevations, and a second based on the highest hardbottom elevations. The second hardbottom elevation mapping based on the highest hardbottom elevations was eventually selected for further refinement during the model calibration process. 5. To further extend the bedrock surfaces developed above, two additional data sources were used: a. The first reflector (seismic) mapping developed for the 27 Town of Palm Beach borrow area investigation (Finkl, et al., 28). b. The minimum beach profile envelope on FDEP profiles R-124 to R-137. This was used to estimate erodible depth elevations where neither hardbottom information nor seismic data (Finkl, et al., 28) was available. The minimum beach profile elevation was developed using the surveys in Table 3 and Table 11 and the Average Profile tool in Beach Morphology Analysis Package 2.. Using the methods and data sources listed above, several versions of the hardbottom/bedrock surface were developed as a calibration parameter, similar to CPE (21). Further details regarding the variation of the hardbottom/bedrock surface are discussed in the next section Existing Structures The locations and elevations of the existing seawalls were verified based on the March 212 aerial photograph, the Town of Lantana Seawall drawings by Taylor Engineering (29), and the beach profile surveys listed in Table 3. n the SWAN model, the seawalls were treated as vertical walls with finite heights ( dams ) ranging from to feet NAVD. The overtopping coefficients = 1.8 and =.1 were equal to the recommended values for vertical walls (Deltares, 211b). Reflection coefficients were assumed to be equal to 2%, similar to CPE (21, 211). n the Delft3D-FLOW model, the seawalls were treated as thin-dams that prevented flow from occurring through or over the structures regardless of water level. The representation of the Lake Worth Pier and the proposed structures under Alternatives B, D, and G is described in the next sections Model Calibration Sediment transport, erosion, and deposition parameters in the Delft3D-FLOW model were recalibrated based on the volumetric erosion rates between December 28 and January 212 (Figure 12). A total of 68 test simulations and calibration runs were conducted to identify the parameters best suited to simulating the general erosion pattern along the study area. Beginning with the model setup used in the 211 alternatives report (CPE, 211), the following model parameters were calibrated: 5 COASTAL PLANNNG & ENGNEERNG, NC.

60 BED and SUS. These two parameters control the magnitude of the large-scale bedload (BED) and suspended sediment (SUS) transport by currents, including longshore currents. These parameters have a default value of 1., but typically range from.5 to 1.5. n the original modeling study (CPE, 21; 211), the values of these parameters were BED = SUS =.6. The final values of these two parameters in this study were BED = SUS =.5. BEDW and SUSW. These two parameters control the magnitude of the bedload (BEDW) and suspended sediment (SUSW) transport associated with the wave-driven orbital velocities. These parameters have a default value of, but usually range from to 1% of BED and SUS. n the original modeling study (CPE, 21, 211), the values of these parameters were BEDW = SUSW =.125. The final values of these two parameters in this study were BEDW = SUSW =.5. Grain Sie. As noted in Section 2.3, the mean grain sie for profiles R-124 to R-139 was approximately.36 mm (1.49 ), based on samples collected by Palm Beach County (1993). However, this value represents an average of multiple samples. To examine the sensitivity of the model to grain sie, a number of simulations were conducted using a mean grain sie of.42 mm (1.26 ), which was based on the samples collected above 7.5 feet NAVD ( 6 feet NGVD) only. Since this change did not affect the model results significantly, final value of the grain sie was the value used in the original modeling study (CPE, 21; 211):.36 mm (1.49 ). Lake Worth Pier Schematiation. As shown in Figure 31, the Lake Worth Pier has a localied influence on the shoreline shape. Accordingly, several representations of the Lake Worth Pier in the model were examined: Option 1. Negligible nfluence: The pier was not used in the SWAN and Delft3D- FLOW models. n the original model study (CPE, 21; 211), the effects of the Lake Worth Pier were shown to be negligible. Option 2. Permeable Structure: n the SWAN model, the pier was treated as a sheet of infinite height with transmission coefficients of.75,.85, and.93. n the Delft3D-FLOW model, the pier was treated as a porous plate, or a partially transparent structure that extends into the flow along one of the grid directions, with a thickness that is much smaller than the grid sie in the direction normal to the porous plate. Unlike other types of structures in the Delft3D-FLOW model, mass and momentum can be exchanged through the porous plate. The porosity of the plate is controlled using a quadratic friction term, or loss coefficient, that is an input to the Delft3D-Flow model. Given permeabilities of 75 percent, 85 percent, and 93 percent, the equivalent loss factors for a.2 m/s (.66 feet/second) longshore current would be 1.36,.65, and.28, respectively. The final calibration run identified the Lake Worth Pier as a structure with a permeability of 85 percent for modeling purposes. 51 COASTAL PLANNNG & ENGNEERNG, NC.

61 Phipps Ocean Park Borrow Area Representation. The Phipps Ocean Park Borrow Areas were the most prominent bathymetric features near the project area (see Figure 26). Following the construction of the Phipps Ocean Park (Reach 7) Beach Restoration project in 26, some slumping of the borrow areas occurred (see Figure 32). Figure 31: January 24, 29 Aerial Photograph of the Lake Worth Pier. NOTE SLUMPNG ALONG THE SDE OF THE BORROW AREA. Figure 32: Typical Survey Profiles (R-133) across the Phipps Ocean Park South Borrow Area. 52 COASTAL PLANNNG & ENGNEERNG, NC.

62 26 and 28 Surveys near the Phipps Ocean Park Borrow Areas with July 26 Aerial Photograph r.:r-----r After-Dredging Surveys Sep.-Dec. 28 FDEP & CPE Profile Dec. 28 Sea Diversified Survey Q) 827 Cl <:: :E 5 C') co FL-East NAD83 Easting (feel) Figure 33: 26 and 28 Surveys near the Phipps Ocean Park Borrow Areas. 53 COASTAL PLANNNG & ENGNEERNG, NC.

63 However, the coverage and resolution of the more recent surveys was not as good as the After-Dredging surveys performed by Bean-Stuyvesant (26) (see Figure 33). To better resolve the bathymetry near the borrow areas, the initial condition was modified by using the 26 After-Dredging surveys as the primary data sources offshore, instead of the 28 surveys (see Figure 33). However, this change to the initial conditions did not improve the model s results. Accordingly, the final calibration run used the more recent 28 surveys as the initial bathymetry s primary data sources (see Figure 26). Activation of Wind Stress in the SWAN Model. n the present calibration effort, wind stress was activated in the majority of simulations, with a smaller number of simulations not including wind stress. As whole, the various test runs suggested that the model results could be improved by activating the default wind stress formulations in both SWAN and Delft3D-FLOW. Accordingly, the final calibration run included wind stress in both the SWAN and Delft3D-FLOW models. Extrapolation of the Bathymetry from the Flow & Morphology Grid at the Northern and Southern Ends of the Local Wave Grid in the SWAN Model. To provide for a stable coupling between the SWAN and Delft3D-FLOW models, the Local Wave Grid is slightly longer than the Flow & Morphology Grid (see Figure 23). The SWAN model allows the bathymetry on the upcoast and downcoast edges of the Local Wave Grid to be: 1. Taken from the initial condition (see Figure 26), or 2. Extrapolated based on the updated bathymetry over the Flow & Morphology Grid. n preliminary simulations, utiliing the first option led to unrealistic accretion near the north end of the Flow & Morphology Grid. Accordingly, the second option was utilied in subsequent simulations, including the final calibration run (see also CPE, 21; 211). Erodible Sediment Depth. As noted earlier, several versions of the hardbottom/bedrock surface were developed as a calibration parameter. The hardbottom/bedrock surface was based on hardbottom outlines from various years, concurrent surveys (Table 11), seismic data (Finkl, et al., 28), and the observed beach profile envelope. Nevertheless, due to the sampling of the survey and seismic data, the maximum elevations of the hardbottom/bedrock were strictly estimates. n some areas, it was necessary to eliminate small variations in the hardbottom/bedrock surface to improve the fit between the observed, volume changes (see Figure 12) and the simulated volume changes. n addition, to moderate scour at the various seawalls, the erodible bed depth at the grid cells in front of them was set to 4.2 feet based on observed profile changes between December 28 and January 212, along with methods appearing in Fowler (1992). The final hardbottom/bedrock elevation based on the historical data review, the anomaly removal, and the scour limitation appears in Figure COASTAL PLANNNG & ENGNEERNG, NC.

64 Cal. 44A Sediment Thickness (feet) Relative to the Dec. 28 Bathymetry (feet) Cal. 44A Hardbottom/Bedrock Elevation (feet NAVD) Landward edge of excavated Phipps Ocean Park borrow area Figure 34: Hardbottom/Bedrock Elevations Used in the Final Calibration Run. 55 COASTAL PLANNNG & ENGNEERNG, NC.

65 t should be noted that the sediment thickness on the left side of Figure 34 is intended to approximate a hard surface whose elevation (in feet NAVD) does not vary with time. Accordingly, the hardbottom/bedrock surface used in subsequent simulations is based on the absolute, NAVD value shown on the right side of Figure 34, not the relative thickness value shown on the left side. Simulated volumetric changes during the final calibration run appear with the observed values in Figure 35. Along the majority of the project area and downdrift area, the simulated erosion rates fall within the uncertainty ranges of the observed erosion rates, which are based on the best vertical accuracy possible for beach profile surveys (±.1 foot on land; ±.2 feet offshore). While the model is not expected to provide an exact simulation of the measured erosion rates, it is able to replicate the general erosion pattern along the area that is shown (34 Atriums, R to R-143, 118 South Ocean Blvd). Based on the agreement between the observed and simulated erosional trends, the Delft3D model was well calibrated for evaluating the performance and impact of the various alternatives. Table 12 lists the final calibration parameters for the waves, water levels, currents, and morphological changes. 4.3 Alternatives Using the model setup in Table 12, the alternatives detailed in Section 3. were simulated for a period of 5 years. To simulate 5 years of bathymetric changes, the cycle of wave cases in Table 9 was repeated 5 times using the morphological acceleration factors listed in the last column of the table. The results for Years -3 are presented in the next sections. Results for Years -5 appear in Appendix Alternative A - No-Action Alternative A is the No-Action Scenario. The bathymetry for this alternative is based on the 211 and 212 beach surveys (see Table 3), followed by the 29 LDAR survey, the 28 surveys, the 27 Light Detection and Ranging (LDAR) survey, the 26 surveys, the 22 LDAR survey, and the hydrographic survey. Since the project area might benefit from littoral drift out of the various projects to the north, the following projects have been superimposed on the bathymetry (see Figure 36): The South End Palm Beach (North Reach 8) Restoration (Figure 9 and Figure 1). The 25, cubic yard dune restoration project south of the Lake Worth Pier (R ' to R '), in accordance with Palm Beach sland BMA (Weber, 213) (see Table 2). The resulting bathymetry appears in Figure COASTAL PLANNNG & ENGNEERNG, NC.

66 March 3, 212 Aerial Photograph Volume Changes, Calibration Run 44A R "' c R c N " E - - : ;; '{;.. >...,.s R-1l6 +.. t:.,.. Ol Ol " c :::; R c: c: : :c :c c t: t: ;.iii... :; ("") ("") o:> o:> ;;; " u <l:: <l::!!... N... E : (j) 818 (j) 818 "'t' <ll <ll l w ll;l....; ll...j ll N... c ,.s.. R R c "' c.. N.c..; u.... ll q E c.. : -= ;a. E FL-Eas! NAD83 Easting (feet) iii ', R ;; :; R " 6 R Volume Change (c.y./foot/year) Figure 35: Simulated Volume Changes during the Final Calibration Run. 57 COASTAL PLANNNG & ENGNEERNG, NC.

67 Table 12: Delft3D Calibration Parameters, South Palm Beach, FL Min. Default Max. Selected Value SWAN Wave Transformation Model Parameters: Breaking Parameter (Hb/db) Breaking Parameter Bottom Friction Coef. for Waves (Optional): JONSWAP Friction Value (m 2 /s 3 )..67 None.2 Collins Friction Value..15 None Not used Madsen Roughness Scale (m)..5 None Not used Triads - Energy Transfer from low to high frequencies in shallow water -N/A- Off -N/A- Off Diffraction* -N/A- Off -N/A- Off Wind Growth -N/A- On -N/A- On JONSWAP Peak Enhancement Factor (for input waves specified in terms of height, period, and direction) -N/A N/A- 1.8 Delft3D-FLOW Model, Flow Parameters: Bottom Friction Coef. for Flow: Chey's Friction Coef. C Manning's n. None.4 Not Used Hori. Eddy Viscosity (m 2 /s) Vertical Eddy Viscosity (m 2 /s) 1 x Extrapolation of Bathymetry from Delft3D-FLOW into SWAN? -N/A- NO -N/A- YES Delft3D-FLOW Model, Sediment Transport Parameters: Spin-up nterval - # of hours between the start of the simulation and the initiation of erosion & deposition estimates 6 None 12.4 Erodible sediment depth (m) Mud.5 Mud 1 Sand 5 Sand 5 See Figure 34 Density of sediment grains (kg/m 3 ) Dry bed density (kg/m 3 Mud 1 Mud 5 ) Sand 5 Sand Median Grain Sie (mm) Hori. Eddy Diffusivity (m 2 /s) Vertical Eddy Diffusivity (m 2 /s) 1 x Dry Cell Erosion Factor 1.5 BED - Current-Related Bedload Transport Factor (including wave-driven currents) SUS - Current-Related Suspended Load Transport Factor (including wave-driven currents) BEDW - Wave-Related Bedload Transport Factor SUSW - Wave-Related Suspended Load Transport Factor * NOTE: The process of diffraction can only be solved accurately when a detailed grid with a spacing 1/1 the wave length is used. n case of much coarser grids, the SWAN computation can become unstable, and results are not reliable (Deltares, 211b). n the case of wind-generated waves, the directional spreading provides sufficient energy transport into shadow areas (Luijendijk, 211). For these reasons, diffraction was not activated in SWAN. 58 COASTAL PLANNNG & ENGNEERNG, NC.

68 Bathymetry through Winter (feet NAVD) Alt. A Bathymetry (feet NAVD) Alt. A Beach & Dune Fill (feet) COASTAL PLANNNG & ENGNEERNG, NC. 59 Figure 36: and Alternative A Bathymetry Comparison. ""Tl r m ll )> g_ ;;;T :: (C (!) c Easting (feet) ""Tl 5 r; m ll )> g_ ;;;T :: (C -1 (!) c Easting (feet) ""Tl 5 r m ll 5 )> g_ ;;;T :: (C -1 c Easting (feet) 6 3 2

69 Alt. A Bathymetry (feet NAVD) Alt. A Sediment Depth (feet)* Q) 824 :c t: ("') (5 822 <{ (j) ca 82 LL Q) 824 :c -2 ("') (5 822 <{ LL Easting (feet) Easting (feet) * Relative to Alt A. Bathymetry Figure 37: Alternative A Flow & Morphology Grid Bathymetry. 6 COASTAL PLANNNG & ENGNEERNG, NC.

70 The initial sediment thickness for Alternative A is based on the difference between the bathymetry shown in Figure 37 (left side) and the hardbottom/bedrock elevation shown in Figure 34 (right side). The resulting sediment thickness appears on the right side of Figure 37. t should be noted since the 28 and bathymetries are not the same, there are slight differences between the sediment thickness in Figure 34 (left side) and the sediment thickness in Figure 37 (right side). Model results given Alternative A appear in Appendix 2, Table 13, Table 14, and Figure 38 through Figure 4. Over the next 3 years, the model suggests that the project area (R ' to R ') could lose 81, c.y. These erosion rates are higher than the one shown in Table 4 (last column). However, the following must be noted: The volume changes estimated by the model generally fall within the uncertainty ranges of the observed volume changes (see Figure 35). Shoreline and volume changes along the project area and the adjacent beaches vary with respect to time, location, and magnitude (see Figure 11 and Figure 12). Given these considerations, the estimated volume changes are reasonable. Within the project area, the model suggests that middle of the project area (R-135 to R-137) will experience the highest erosion rates under either wave climate. The observed volume changes between 28 and 212 indicated higher erosion along the northern half of the project area (see Table 4). However, an erosion hotspot centered further to the south is consistent with the erosion rates (see Figure 11 and Figure 12) and the 28 sidewalk collapse at Lantana Public Beach (see Figure 3). Low-tide shoreline changes appear in Figure 39. The model suggests that under the average Wave Climate A, the shoreline might be stable along a small section of the project area (R-135). However, most of the project area would experience shoreline retreat. At the Mayfair House (R ), the model suggests that retreat could occur back to existing seawall. At other locations, the amount of dry beach width at Year 3 would be very small. Hardbottom coverage is detailed in Appendix 2 and summaried in Table 14. The values shown therein include hardbottom coverage only. CPE (27a, pp ) notes that hardbottom exposure along the project area and the adjacent beaches varies widely over time, with hardbottom being covered and uncovered due to natural processes. The natural variability in hardbottom exposure is one of the primary reasons that Palm Beach County compiles hardbottom mapping information on a frequent basis (see Section above). 61 COASTAL PLANNNG & ENGNEERNG, NC.

71 Table 13: Volume Changes Based on the Delft3D Model, Years -3 Beach Segment Beach Volume Change, Entire Beach Profile, Pre-Construction versus Year 3 (cubic yards) Length (feet) Alt. A Alt. B Alt. C Alt. D Alt. E Alt. F Alt. G Reach 8 North 2,226-21,5-21,1-21,2-21,6-21,4-21,4-21,6 R-125 to R ' Lake Worth Public Beach 1,884 78,7 81,9 78,9 78,8 79,1 78,7 78,6 R ' to R ' Reach 8 South 6,542-74,5-49,2-69,9-67,2-64, -7,6-68,6 R ' to R ' South Palm Beach Segment 2,679-57, -11,2-37,2-8,2 17,6-34,2-8,3 R ' to R ' Lantana Segment 848-2,4-16,5-12,6-8, 4,9-12,1-6,5 R ' to R ' Manalapan Segment 851-3,6 4 6,1 2,4 1,9 6,1 1,9 R ' to R ' PROJECT AREA TOTAL 4,378-81, -27,3-43,7-13,8 33,4-4,2-12,9 R ' to R ' Downdrift 5,85-6,9-13,9 2,1-6,6 21,6 14,4-1, R ' to R-144 NOTE: Negative (-) volume changes indicate erosion into pre-construction profile. Positive volume changes indicate accretion or remaining fill. 62 COASTAL PLANNNG & ENGNEERNG, NC.

72 Table 14: Coverage of March 212 Hardbottom at Year 3 Based on the Delft3D Model (NOTE This table does not include exposure of presently buried hardbottom, which occurs naturally and frequently along the project area) Beach Segment Beach Hardbottom Coverage (acres) Length (feet) Alt. A Alt. B Alt. C Alt. D Alt. E Alt. F Alt. G Reach 8 North 2, R-125 to R ' Lake Worth Public Beach 1, R ' to R ' Reach 8 South 6, R ' to R ' South Palm Beach Segment 2, R ' to R ' Lantana Segment R ' to R ' Manalapan Segment R ' to R ' PROJECT AREA TOTAL 4, R ' to R ' Downdrift 5, R ' to R-144 TOTAL (R-125 to R-144) 2, PROJECT-NDUCED COVERAGE -N/A AT YEAR 3, R-125 to R COASTAL PLANNNG & ENGNEERNG, NC.

73 March 3, 212 Aerial Volume Changes, Years -3, Entire Profile, Alt. A & B ,-r--r----o::c::::;:c=c=c======::;l Alt. A Volume Changes, Years -3 --Alt. B Remaining Fill, Year 3 --Alt. 8 nitial Fill Volume at Year --mpact(-) Benefit(+) of Alt. B R-1;J1 + R-1;J R-1;J Q) Ol c :.c t::: 82 4: iii <U w _j ll R R-1 ;J6 + R R R R-14 + R R R Easting (feet) Remaining Fill (c.y./foot) Figure 38: Volumes Changes Given Alternatives A and B. 64 COASTAL PLANNNG & ENGNEERNG, NC.

74 North Half of Project Area South Half of Project Area Year MLLW, All. B 8232 " , ' Q) Ol c :c t: ("") <Xl <l:: (j) <ll w LL l ;: N ' ot: :1:: '.... :!..;... o N ' : :.c ; :!... ft " ii i c Q) Ol c :c t: 8194 ("") <Xl <l:: (j) <ll w LL : ' : ' : : ' :, -1 a: T r { Easting (feet) Easting (feet) Figure 39: Low-Tide Shoreline Changes, Alternatives A and B. 65 COASTAL PLANNNG & ENGNEERNG, NC.

75 Figure 4: Volume Changes versus Time. Coverage of the present (March 3, 212) hardbottom can be readily assessed based on the deposition that occurs in the model (>.2 feet) and the location of the present hardbottom (see Appendix 2). However, it is much more difficult to estimate the exposure of hardbottom that is presently buried, as the hardbottom/bedrock elevation in Figure 34 (right half) is an estimate. For these reasons, hardbottom exposure is not shown. Overall, hardbottom coverage values given the No-Action scenario (Table 14, 3 rd column) are consistent with those of CPE (211, pp. 22, 71). The degree of hardbottom coverage is consistent with the observed variability in exposed hardbottom along profiles R-134 and R-141 between March 1993 and May 26 (see CPE, 27a, pp ) Alternative B - Original 21 Recommended Plan Alternative B places 13 breakwaters and 75, cubic yards of fill material along the project area. The initial bathymetry for this alternative appears in Figure 41. Model results given Alternative B appear in Appendix 2, Table 13, Table 14, Figure 38 through Figure 4, and Figure 42. The model results suggest that under an average wave climate, the benefits associated with the project will be concentrated along the northern third of the project area and the quarter-mile segment updrift (R-133 to R-135) (see Figure 38 and Figure 39). Along these areas, erosion into the pre-construction shoreline will be prevented over the first 3 years. 66 COASTAL PLANNNG & ENGNEERNG, NC.

76 Bathymetry through Winter (feet NAVD) Alt. B-D Bathymetry (feet NAVD) Alt. B-D Beach Fill (feet) COASTAL PLANNNG & ENGNEERNG, NC. 67 Figure 41: nitial Bathymetry for Alternatives B, C, and D (excluding groins or breakwaters). )> w ;:::). :T D? '. ( filii! f Easting (feet) )> 8251 w (Q j r A r i l, i R-13ll.l A Easting (feet) )> co w ;:::). :T , CO " - '" Easting (feet) i4 -i3-2

77 Project-nduced Hardbottom Coverage R-125 to R-144 Figure 42: Project-nduced Hardbottom Coverage versus Time. Within the northern third of the project area, salients are shown to form along the shoreline. The model results also suggest that under an average wave climate, the breakwaters would have a minor impact on the downdrift segment between R ' and R-139, along with the beaches facing the gaps between the structures (see Figure 38). Alternative B would bury approximately 1.56 acres of hardbottom during initial construction (see Table 5). This includes hardbottom covered directly by fill (1.11 acres) and the footprint of the structures (.45 acres). However, the model suggests that after construction, the amount of additional hardbottom coverage that would occur would be less than the No Action scenario (Alternative A) due to the erosion and deposition patterns around the breakwaters (see Table 14 and Figure 42) Alternative C - 75, Cubic Yards of Fill without Structures Alternative C features the same fill layout as Alternative B. However, breakwaters are not included. The initial bathymetry for this alternative appears in Figure 41. Model results given Alternative B appear in Appendix 2, Table 13, Table 14, Figure 4, and Figure 42 to Figure 44. n general, the model results show that there would be considerable spreading of fill given the construction of Alternative C (see Figure 43). n most areas, erosion into the pre-construction beach profile over the first 3 years would not be reduced substantially. The only exceptions might be the northern and southern ends of the project area (see Figure 43). 68 COASTAL PLANNNG & ENGNEERNG, NC.

78 March 3, 212 Aerial Volume Changes, Years -3, Entire Profile, Alt. A & C ,-r--r-c:::;:c:=c:=c:=c:====:::;-l Alt. A Volume Changes, Years -3 --Alt. C Remaining Fill, Year 3 --All. C nitial Fill Volume at Year --mpact(-) Benefit(+) of Alt. c R R R-1;J Q) Ol c :.c t::: 82 iii <U w _j ll R R-1;J6 + R R R R-14 + R R R Easting (feet) Remaining Fill (c.y./foot) Figure 43: Volume Changes Given Alternatives A & C. 69 COASTAL PLANNNG & ENGNEERNG, NC.

79 North Half of Project Area South Half of Project Area j 8224 Ol c :c ("") < 822 (j) <ll w LL ot: N '. :1: _.,' ;; ' i c 8198 v 8196 Ol c :c ("") < <( (j) 8192 <ll w LL :!..; : N :..c ; :! Easting (feet) Easting (feet) Figure 44: Low-Tide Shoreline Changes, Alternatives A and C. 7 COASTAL PLANNNG & ENGNEERNG, NC.

80 Alternative C would bury approximately 1.11 acres of hardbottom during initial construction (see Table 5). Model results suggest that project-induced hardbottom coverage could eventually increase over the 5 year post-construction period (see Figure 42). Overall, the model suggests that simply removing the breakwaters from the project s design reduces the benefit of the project by at least half (see Table 13), while increasing the hardbottom impact (see Table 13 and Figure 42) due to sediment transport. Given these results, Alternative C does not offer any significant improvement over Alternative B or the County s present shoreline management strategy of periodic dune fill placement (see Table 1) Alternative D - 75, Cubic Yards of Fill with Short Groins Alternative D also features the same fill layout as Alternative B. However, the breakwaters are replaced by short groins as shown in Figure 16 and Figure 17. The initial bathymetry for this alternative appears in Figure 41. Model results given Alternative B appear in Appendix 2, Table 13, Table 14, Figure 4, Figure 42, Figure 45, Figure 46, and Figure 47. f Alternative D were constructed, erosion into the pre-construction shoreline would occur by Year 3. However, based on the model s estimates, the amount of erosion would be 83 percent less than what would occur under Alternative A, and 68 percent less than what would occur under Alternative C (see Table 13 and Figure 47). Under an average wave climate, there could still be remaining beach fill at Year 3 along the northern and southern ends of the project area (see Figure 45, left half). The updrift benefits of the project would extend to roughly R-132. The model also suggests that the 3-year downdrift impact under an average wave climate would be negligible (see Table 13 and Figure 45). Alternative D would bury approximately 1.11 acres of hardbottom during initial construction (see Table 5). Model results suggest that project-induced hardbottom coverage would remain below this level under an average wave climate (see Figure 42 and Figure 45). Overall, the model suggests that replacing the breakwaters with groins increases the benefits of the project in terms of a more uniform beach response and decreases the downdrift, erosional impact (see Table 13 and Figure 47). Hardbottom coverage at construction would be less than Alternative B (see Table 5). Hardbottom coverage in the post-construction years would be comparable to or less than Alternative C (see Figure 42). Given these results, the addition of short groins to the project s design is a feasible approach. 71 COASTAL PLANNNG & ENGNEERNG, NC.

81 March 3, 212 Aerial Volume Changes, Years -3, Entire Profile, Alt. A & D ,-r--r-c:::;:c=c=c===c===c==:::;-] Alt. A Volume Changes, Years -3 --Alt. D Remaining Fill, Year 3 --All. D nitial Fill Volume at Year --mpact(-) Benefit(+) of Alt. D R R R Q) 1 c :.c t::: ("') co <( Vi (tj llj LL R R R R R R R R R Easting (feet) Remaining Fill (c.y./foot) Figure 45: Volume Changes Given Alternatives A & D. 72 COASTAL PLANNNG & ENGNEERNG, NC.

82 North Half of Project Area South Half of Project Area " j 8224 Ol c :c t: ("") <Xl <l:: (j) <ll w LL \ r. :. r r f r f l l r' r ot: N '. :1::... -'.' :!..; : N ' :... ft.;.c ; :! ;; ' i c v Ol c :c t: 8194 ("") <Xl <l:: (j) <ll w LL ' '. 1..;. i., -1 T {... :.... i Easting (feet) Easting (feet) Figure 46: Low-Tide Shoreline Changes, Alternatives A and D. 73 COASTAL PLANNNG & ENGNEERNG, NC.

83 March 3, 212 Aerial Beach Fill Performance Comparison, Alternatives C, D, & F !=!====r:====::c=====r====:::r====:::;-] --Alt. C-D nitial Fill at Year ---- Alt. F nitial Fill at Year --Alt. A Volume Changes, Years -3 --Alt. C Remaining Fill, Year 3 --Alt. D Remaining Fill, Year Alt. F Remaining Fill, Year 3 R w OJ c E t::: R ("') co <( (j) R <tl LlJ LL R V c a (; 819 c R J i... E t> Ci R Easting (feet) Remaining Fill (c.y./foot) Figure 47: Comparative Performance, Alternatives A, C, D, & F. 74 COASTAL PLANNNG & ENGNEERNG, NC.

84 4.3.5 Alternative E - Fill Able to Last 3 Years without Any Structures The intent of Alternative E is to place enough fill to last 3 years without any coastal structures. The fill volume simulated was 16,6 cubic yards (Table 6). The initial bathymetry for Alternative E appears in Figure 48. Model results given Alternative E appear in Appendix 2, Table 13, Table 14, Figure 4, Figure 42, Figure 49, and Figure 5. Under an average wave climate, the volume placed under Alternative E would be able to last for 3 years (see Figure 49). Model results suggest that erosion into the pre-construction beach profile through Year 3 would be minimal. Except for the long taper near the southern end of the project area (R to R '), the shoreline at Year 3 would be located near its preconstruction location (see Figure 5). The spreading of fill would generate an estimated benefit of 21,6 c.y downdrift (R ' to R-144) and an updrift (R ' to R ') benefit on the order of 1,5 c.y. (see Table 13). Alternative E would bury 1.53 acres of hardbottom at construction (Table 6). After project construction, the model estimates that hardbottom impact could increase to 1.7 acres under an average wave climate (see Figure 42). Overall, the model suggests that under an average wave climate, Alternative E could be a viable solution, since the hardbottom impacts would be moderate (see Figure 42). Over the fill length as a whole, approximately 21 percent of the initial fill volume would be remaining at Year Alternative F Fill Optimied to Minimie Hardbottom mpacts and Maximie Project Life Alternative F places a fill volume similar to Alternative C, approximately 75, cy. However, to reduce hardbottom coverage and improve beach fill performance, fill is concentrated in the area of highest erosion near the middle of the project area. The initial bathymetry for this alternative appears in Figure 51. Model results given Alternative B appear in Appendix 2, Table 13, Table 14, Figure 4, Figure 42, Figure 47, Figure 52, and Figure 53. n general, the model results suggest that the performance of Alternative F would be similar to Alternative C, except for the following: There would be an improvement in beach fill performance between Palm Beach Oceanfront nn (R-135.5) and the mperial House (R-136.5) (see Figure 47 and Table 13). While erosion into the pre-construction shoreline may occur along that area by Year 3, the degree of erosion would be less. Project-induced hardbottom coverage would generally be less (see Table 13 and Figure 42). 75 COASTAL PLANNNG & ENGNEERNG, NC.

85 Bathymetry through Winter (feet NAVD) Alt. E Bathymetry (feet NAVD) Alt. E Beach Fill (feet) 1 COASTAL PLANNNG & ENGNEERNG, NC. 76 Figure 48: nitial Bathymetry for Alternative E. "Tl r m ll!4. )> co VJ ;:::+ ::J ( & "Tl JR-131 r 821 ). ltf 5... )> j) 8251 > ;::: ( & 8195 lll } l R-137 ' ) 819 il 15 1 "Tl r m ll (f) 5 ; )> 825 ;:::+ :::!. ::J ( & -5 (](] non 1 L."---1 J c_j i -----, -, r r M E! l J n n f //J J " " Easting (feet) Easting (feet) Easting (feet)

86 March 3, 212 Aerial Volume Changes, Years -3, Entire Profile, Alt. A & E ,-r--r-c:::;:c=c=c=c====::;l Alt. A Volume Changes, Years -3 --Alt. E Remaining Fill, Year 3 --All. E nitial Fill Volume at Year --mpact(-) Benefit(+) of Alt. E R R R Q) Ol c :.c t::: ('") o:> : iii <U w _j u fl '-. R R R R R R-14 + R R R Easting (feet) Remaining Fill (c.y./foot) Figure 49: Volume Changes Given Alternatives A & E. 77 COASTAL PLANNNG & ENGNEERNG, NC.

87 North Half of Project Area South Half of Project Area ot: N ' :r:... :!..; : N.....:.c ; :! ;; ' i c v 8196 OJ c: :c ("') co <( Vi 8192 <tl LlJ LL t. r.. '. '. ' ' ' ', /...., Easting (feet) Easting (feet) Figure 5: Low-Tide Shoreline Changes, Alternatives A and E. 78 COASTAL PLANNNG & ENGNEERNG, NC.