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As coastal development in the Cayman Islands increases, the importance of beach erosion continues to increase. One location that experiences greater than normal erosion is the stretch of beach adjacent to the Marriott Hotel, located on the southern end of Seven Mile Beach, in Grand Cayman, B.W.I. In order to stabilize the eroded beach, a submerged breakwater system was constructed approximately 170 feet offshore. The breakwater system consists of 232 Reef Ball artificial reef units, 200 of which were installed in the fall of 2002, and 32 in the fall of 2005. Following the breakwater extension in the fall of 2005, approximately 6,000 cubic yards of beach fill were placed along 1,000 feet in the southern Seven Mile Beach area, with approximately 1,900 cubic yards placed in front of the Marriott. To provide a basis for examining the effects of this breakwater system, a field monitoring program was conducted, which included the collection of beachiv profile surveys, beach width measurements, and ground and aerial photographic images. These data provided information to analyze the behavior of the beach and shoreline response, including shoreline, crossshore, and volumetric changes, in addition to determining the expected wave transmission and sand transport leeward of the breakwater. In November 2002, prior to the installation of the breakwater system, the shoreline in front of the Marriott had retreated to the seawall, with waves scouring underneath the seawall. Since the installation of the submerged breakwater system the beach width and volume of sand have substantially increased. The beach width varied seasonally 25 to 70 feet, compared to 0 to 30 feet before installation. Four years after the completion of the project, the average beach width reached 72 feet. Wave transmission analysis, based on empirical equations, showed a wave height reduction of at least 60%. Under most nonstorm conditions, sediment leeward of the breakwater remains stable, and has allowed a salient to build up in front of the Marriott Hotel
Shoreline Response for a Reef Ball TM Submerged Breakwater System Offshore of Grand Cayman Island By Dana Suzanne Arnouil Bachelor of Science Ocean Engineering Florida Institute of Technology 2006 A thesis submitted to Florida Institute of Technology in partial fulfillment of the requirements for the degree of Master of Science in Ocean Engineering Melbourne, Florida August, 2008 Shoreline Response for a Reef Ball TM Submerged Breakwater System Offshore of Grand Cayman Island A thesis by Dana Suzanne Arnouil Approved as to style and content by: _ Lee E Harris, Ph.D.,P.E., Committee Chair Associate Professor, Ocean Engineering Department of Marine and Environmental Systems _ Steven M Jachec, Ph.D.,P.E., Committee Member Assistant Professor, Ocean Engineering Department of Marine and Environmental Systems _ Ralph V Locurcio, M.S.E.,P.E., Committee Member Professor, Civil Engineering Department of Civil Engineering _ George A Maul, Ph.D., Program Chair Professor, Oceanography Department of Marine and Environmental Systems Abstract Shoreline Response for a Reef Ball TM Submerged Breakwater System Offshore of Grand Cayman Island Author Dana S Arnouil Principal Advisor Lee E Harris, Ph.D., P.E As coastal development in the Cayman Islands increases, the importance of beach erosion continues to increase One location that experiences greater than normal erosion is the stretch of beach adjacent to the Marriott Hotel, located on the southern end of Seven Mile Beach, in Grand Cayman, B.W.I In order to stabilize the eroded beach, a submerged breakwater system was constructed approximately 170 feet offshore The breakwater system consists of 232 Reef Ball artificial reef units, 200 of which were installed in the fall of 2002, and 32 in the fall of 2005 Following the breakwater extension in the fall of 2005, approximately 6,000 cubic yards of beach fill were placed along 1,000 feet in the southern Seven Mile Beach area, with approximately 1,900 cubic yards placed in front of the Marriott To provide a basis for examining the effects of this breakwater system, a field monitoring program was conducted, which included the collection of beach iii profile surveys, beach width measurements, and ground and aerial photographic images These data provided information to analyze the behavior of the beach and shoreline response, including shoreline, cross-shore, and volumetric changes, in addition to determining the expected wave transmission and sand transport leeward of the breakwater In November 2002, prior to the installation of the breakwater system, the shoreline in front of the Marriott had retreated to the seawall, with waves scouring underneath the seawall Since the installation of the submerged breakwater system the beach width and volume of sand have substantially increased The beach width varied seasonally 25 to 70 feet, compared to to 30 feet before installation Four years after the completion of the project, the average beach width reached 72 feet Wave transmission analysis, based on empirical equations, showed a wave height reduction of at least 60% Under most non-storm conditions, sediment leeward of the breakwater remains stable, and has allowed a salient to build up in front of the Marriott Hotel iv Table of Contents List of Figures vii List of Tables ix List of Symbols and Abbreviations x Acknowledgements xii Introduction Background and Review of Literature 2.1 2.1.1 Negative Impacts 2.1.2 Breakwater Design Considerations 2.1.3 Wave Transmission Models 13 2.2 Reef Ball Breakwaters 16 2.3 Shoreline Analysis 19 2.4 Sediment Transport 20 Marriott Reef Ball Breakwater Project 24 3.1 Erosion Issues 24 3.1.1 Environmental Conditions 26 3.1.2 Marriott Seawall 32 3.2 Submerged Breakwaters for Shore Protection Marriott Reef Ball Breakwater Project 33 Methodology 39 4.1 Data Sources 39 4.2 Shoreline Changes 40 4.2.1 Survey-based 40 4.2.2 Aerial Photography 42 4.3 Volumetric Changes 43 4.4 Wave Transmission 44 4.5 Sediment Transport 45 Project Performance 48 v 5.1 Shoreline Changes 48 5.1.1 Plan View 48 5.1.2 Time Series 52 5.2 Beach Profile Changes 53 5.3 Volumetric Changes 56 5.4 Wave Transmission 60 5.5 Sediment Transport 62 Conclusions 66 Recommendations 68 References 69 Appendix A A-1 Storm Information A-1 Appendix B B-1 Tidal Data B-1 Appendix C C-1 Photographs C-1 Appendix D D-1 Sand Sample Report D-1 Appendix E E-1 Wave Transmission .E-1 vi List of Figures Figure Grand Cayman location map Figure Location of Seven Mile Beach and the Marriott Hotel Figure Nearshore circulation and accretion patterns in response to a submerged breakwater under oblique wave incidence Figure Parameters for a submerged breakwater .10 Figure Reef Ball unit installed off Grand Cayman Island 17 Figure Reef Balls being deployed from a barge 18 Figure Reef Ball Breakwater after installation in Grand Cayman Island 18 Figure Forces acting on a grain resting on the bed 21 Figure Shields curve for the initiation of motion 23 Figure 10 View looking to the North at Marriott seawall in 10/02 25 Figure 11 Grand Cayman‟s wind and storm directions, surface currents and details of shelf-edge reef 27 Figure 12 Typical Seven Mile Beach sand transport system 28 Figure 13 Seasonal beach width changes from 1999-2003 .30 Figure 14 Hurricane and Tropical Storm paths near Grand Cayman 31 Figure 15 Hurricane and Tropical Storm paths near Grand Cayman 31 Figure 16 Aerial image from 1994 showing location of Marriott Seawall and width of beach in front of the seawall .33 Figure 17 Aerial Image from 2004 showing the Marriott Reef Ball Submerged Breakwater Project 34 Figure 18 Initial design for Marriott Reef Ball Breakwater Project 35 Figure 19 Bathymetry plot for in front of the Marriott Hotel in 08/02 .36 Figure 20 Example of Anchored Reef Ball .38 Figure 21 Location of beach profile survey lines (04/04) 41 Figure 22 Grain size distribution curve 46 Figure 23 Location of shoreline from 04/94 to 11/02 (pre- breakwater installation) 49 Figure 24 Location of shoreline from 11/02 to 06/08 (post-breakwater installation) 50 Figure 25 Cumulative shoreline change (from 04/94 to 06/08) 52 Figure 26 Cross-shore positions for PL (South end of breakwater) 54 Figure 27 Cross-shore positions for PL (South end of seawall) 54 Figure 28 Cross-shore positions for PL (Center of seawall) 55 Figure 29 Cross-shore positions for PL (North end of seawall) 55 Figure 30 Annualized volume changes between surveys 58 vii Figure 31 Cumulative volume changes from 11/02 for each section 59 Figure 32 Time series cumulative volume changes per unit width from 11/02 60 Figure 33 Wave transmission coefficient for a wave period of seconds 61 Figure 34 Wave transmission coefficient for a wave period of 10 seconds 62 Figure 35 Shields diagram showing variables required for sediment transport 63 viii List of Tables Table Alternative Solutions for Coastal Erosion and Protection .2 Table Type of shoreline formation for the ratio Ls/X .12 Table Summary of design characteristic for Marriott Reef Ball Breakwater 36 Table Timeline for Marriott Reef Ball Breakwater Project 37 Table Data available for Marriott Area from 1972 to 2008 39 Table Available Profile Data for the Marriott Hotel 42 Table Variables used to determine the critical shear stress 47 Table Average shoreline position and rate of change 51 Table Average annual shoreline changes .51 Table 10 Volume changes for each survey period 57 Table 11 Volume changes per unit width of beach for each survey period 57 Table 12 Annualized volume changes per unit width of beach for each survey period 57 Table 13 Cumulative volume changes per unit width from 11/02 (As-Built) 59 Table 14 Variables calculated to determine when sediment transport occurs 63 Table 15 Results using Friebel and Harris method for a period of seconds 64 Table 16 Results using Friebel and Harris method for a period of seconds 64 Table 17 Results using Friebel and Harris method for a period of seconds 65 Table 18 Results using Friebel and Harris method for a period of 10 seconds 65 ix List of Symbols and Abbreviations Symbol Definition Units A Cross-sectional area of breakwater ft2 B Breakwater crest width ft d Depth at toe of structure ft ds particle diameter ft Dn50 Nominal diameter of stone ft F Freeboard ft g Acceleration due to gravity ft/s2 h Height of breakwater ft Hi Incident wave height ft Ht Transmitted wave height ft k Wave number N/A Kt Wave transmission coefficient N/A L Wave length ft Ls Length of breakwater structure ft MWL Mean water level ft R* Grain Reynolds number N/A SWL Still water level ft T Wave period s U Horizontal water particle velocity ft/s u* Shear velocity ft/s V Volume cyd/ft X Distance from the undisturbed shoreline ft x C-4 Figure C-3 Aerial photographs for 2004 (Nov.) and 2006 (from right to left) (Photo Courtesy Tim Austin, Cayman Islands Department of Environment) Figure C-4 View looking to the South and North at seawall in Oct 2002 Figure C-5 View looking to the South and North at seawall in 02/03 Figure C-6 View looking to the South and North at seawall in May 2005 (All photographs courtesy of Lee Harris) C-5 Figure C-7 View looking to the South and North at seawall in 01/08 Figure C-8 View looking to the South and North at seawall in 06/08 Figure C-9 Example of rocky shoreline to the south (02/03) and boat docking to the north (01/08) of the Marriot Hotel (All photographs courtesy of Lee Harris) C-6 Appendix D Sand Sample Report D-1 D-2 Appendix E Wave Transmission Figure E-1 Wave transmission coefficient between for methods for a wave period of seconds E-4 Figure E-2 Wave transmission coefficient between for methods for a wave period of seconds E-4 Table E-1 Design parameters used in determining wave transmission E-2 Table E-2 Design parameters used in determining wave transmission E-3 Table E-3 Results using Armono and Hall method for a period of seconds E-5 Table E-4 Results using Armono and Hall method for a period of seconds E-5 Table E-5 Results using Armono and Hall method for a period of seconds E-6 Table E-6 Results using Armono and Hall method for a period of 10 seconds E-6 Table E-7 Results using Seabrook and Hall method for a period of seconds E-7 Table E-8 Results using Seabrook and Hall method for a period of seconds E-7 Table E-9 Results using Seabrook and Hall method for a period of seconds E-8 Table E-10 Results using Seabrook and Hall method for a period of 10 seconds E-8 Table E-11 Results using Ahrens method for a period of seconds E-9 Table E-12 Results using Ahrens method for a period of seconds E-9 Table E-13 Results using Ahrens method for a period of seconds E-10 Table E-14 Results using Ahrens method for a period of 10 seconds E-10 E-1 Table E-1 Design parameters used in determining wave transmission Wave Height, H (ft) d (ft) F(ft) F/H B/d h/d F/B 3.5 4.8 4.8 4.8 4.8 5.13 6.41 -0.7 -0.7 -0.7 -0.7 -1.03 -2.31 -0.70 -0.35 -0.23 -0.20 -0.26 -0.46 5.21 5.21 5.21 5.21 4.88 3.90 0.85 0.85 0.85 0.85 0.80 0.64 -0.028 -0.028 -0.028 -0.028 -0.04 -0.09 10 7.69 8.97 10.26 11.54 12.82 -3.59 -4.87 -6.16 -7.44 -8.72 -0.60 -0.70 -0.77 -0.83 -0.87 3.25 2.79 2.44 2.17 1.95 0.53 0.46 0.40 0.36 0.32 -0.14 -0.19 -0.25 -0.30 -0.35 E-2 E-3 T (s) H (ft) 3.5 10 Table E-2 Design parameters used in determining wave transmission 10 L(ft) B/L Hi/gT2 L(ft) B/L Hi/gT2 L(ft) B/L Hi/gT2 L(ft) B/L Hi/gT2 46.67 46.67 46.67 46.67 48.03 52.74 56.73 60.17 63.15 65.73 67.97 0.54 0.54 0.54 0.54 0.52 0.47 0.44 0.42 0.40 0.38 0.37 0.002 0.004 0.006 0.007 0.008 0.010 0.012 0.014 0.016 0.017 0.019 72.33 72.33 72.33 72.33 74.86 83.06 90.29 96.77 102.69 108.06 113.00 0.35 0.35 0.35 0.35 0.33 0.30 0.28 0.26 0.24 0.23 0.22 0.001 0.002 0.003 0.003 0.003 0.004 0.005 0.006 0.007 0.008 0.009 97.94 97.94 97.94 97.94 101.13 112.57 122.80 132.07 140.62 148.50 155.85 0.26 0.26 0.26 0.26 0.25 0.22 0.20 0.19 0.18 0.17 0.16 0.000 0.001 0.001 0.002 0.002 0.002 0.003 0.003 0.004 0.004 0.005 123.09 123.09 123.09 123.09 127.16 141.77 154.87 166.81 177.92 188.19 197.81 0.20 0.20 0.20 0.20 0.20 0.18 0.16 0.15 0.14 0.13 0.13 0.000 0.001 0.001 0.001 0.001 0.002 0.002 0.002 0.002 0.003 0.003 Figure E-1 Wave transmission coefficient between for methods for a wave period of seconds Figure E-2 Wave transmission coefficient between for methods for a wave period of seconds E-4 Table E-3 Results using Armono and Hall method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 46.67 1.13 0.66 0.66 0.75 4.8 46.67 2.27 0.60 1.20 1.36 4.8 46.67 3.40 0.54 1.62 1.83 3.5 4.8 46.67 3.97 0.51 1.78 2.02 4 5.13 0.33 48.03 4.35 0.54 2.15 2.34 6.41 1.61 52.74 4.68 0.65 3.27 3.06 7.69 2.89 56.73 4.92 0.71 4.26 3.49 8.97 4.17 60.17 5.09 0.73 5.13 3.73 10.26 5.46 63.15 5.21 0.74 5.88 3.83 11.54 6.74 65.73 5.27 0.72 6.51 3.82 10 12.82 8.02 67.97 5.30 0.70 7.02 3.72 Table E-4 Results using Armono and Hall method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 72.33 1.23 0.69 0.69 0.85 4.8 72.33 2.45 0.67 1.33 1.64 4.8 72.33 3.68 0.64 1.92 2.36 3.5 4.8 72.33 4.30 0.63 2.19 2.69 5.13 0.33 74.86 4.72 0.67 2.69 3.18 6.41 1.61 83.06 5.19 0.82 4.11 4.27 6 7.69 2.89 90.29 5.60 0.91 5.47 5.11 8.97 4.17 96.77 5.95 0.97 6.78 5.76 10.26 5.46 102.69 6.25 1.00 8.04 6.28 11.54 6.74 108.06 6.52 1.03 9.24 6.70 10 12.82 8.02 113.00 6.76 1.04 10.39 7.02 E-5 Table E-5 Results using Armono and Hall method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 97.94 1.26 0.71 0.71 0.89 4.8 97.94 2.51 0.69 1.38 1.73 4.8 97.94 3.77 0.68 2.03 2.54 3.5 4.8 97.94 4.39 0.67 2.34 2.93 5.13 0.33 101.13 4.85 0.72 2.88 3.49 6.41 1.61 112.57 5.37 0.88 4.40 4.73 7.69 2.89 122.80 5.84 0.98 5.90 5.73 8.97 4.17 132.07 6.25 1.05 7.36 6.57 8 10.26 5.46 140.62 6.62 1.10 8.79 7.28 11.54 6.74 148.50 6.96 1.13 10.19 7.88 10 12.82 8.02 155.85 7.27 1.16 11.57 8.41 Table E-6 Results using Armono and Hall method for a period of 10 seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 10 4.8 123.09 1.27 0.71 0.71 0.90 10 4.8 123.09 2.54 0.70 1.40 1.78 10 4.8 123.09 3.81 0.69 2.07 2.63 3.5 10 4.8 123.09 4.44 0.69 2.40 3.05 10 5.13 0.33 127.16 4.91 0.74 2.97 3.64 10 6.41 1.61 141.77 5.46 0.91 4.54 4.95 10 7.69 2.89 154.87 5.95 1.02 6.09 6.04 10 8.97 4.17 166.81 6.39 1.09 7.63 6.96 10 10.26 5.46 177.92 6.79 1.14 9.14 7.76 10 11.54 6.74 188.19 7.16 1.18 10.64 8.46 10 10 12.82 8.02 197.81 7.51 1.21 12.11 9.09 E-6 Table E-7 Results using Seabrook and Hall method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 46.67 1.13 0.39 0.39 0.44 4.8 46.67 2.27 0.27 0.53 0.61 4.8 46.67 3.40 0.24 0.73 0.83 3.5 4.8 46.67 3.97 0.24 0.85 0.97 4 5.13 0.33 48.03 4.35 0.29 1.15 1.25 6.41 1.61 52.74 4.68 0.40 2.00 1.87 7.69 2.89 56.73 4.92 0.47 2.85 2.34 8.97 4.17 60.17 5.09 0.53 3.71 2.70 10.26 5.46 63.15 5.21 0.58 4.61 3.00 11.54 6.74 65.73 5.27 0.61 5.53 3.24 10 12.82 8.02 67.97 5.30 0.65 6.50 3.44 Table E-8 Results using Seabrook and Hall method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 72.33 1.23 0.39 0.39 0.48 4.8 72.33 2.45 0.27 0.54 0.66 4.8 72.33 3.68 0.24 0.73 0.90 3.5 4.8 72.33 4.30 0.25 0.86 1.05 5.13 0.33 74.86 4.72 0.29 1.15 1.36 6.41 1.61 83.06 5.19 0.40 2.02 2.10 6 7.69 2.89 90.29 5.60 0.48 2.88 2.69 8.97 4.17 96.77 5.95 0.54 3.76 3.20 10.26 5.46 102.69 6.25 0.58 4.68 3.66 11.54 6.74 108.06 6.52 0.63 5.63 4.08 10 12.82 8.02 113.00 6.76 0.66 6.62 4.47 E-7 Table E-9 Results using Seabrook and Hall method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 97.94 1.26 0.39 0.39 0.49 4.8 97.94 2.51 0.27 0.54 0.68 4.8 97.94 3.77 0.25 0.74 0.92 3.5 4.8 97.94 4.39 0.25 0.86 1.08 5.13 0.33 101.13 5.00 0.29 1.16 1.45 6.41 1.61 112.57 5.37 0.41 2.03 2.18 7.69 2.89 122.80 5.84 0.48 2.90 2.82 8.97 4.17 132.07 6.25 0.54 3.78 3.38 8 10.26 5.46 140.62 6.62 0.59 4.71 3.90 11.54 6.74 148.50 6.96 0.63 5.67 4.38 10 12.82 8.02 155.85 7.27 0.67 6.67 4.85 Table E-10 Results using Seabrook and Hall method for a period of 10 seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 10 4.8 123.09 1.27 0.39 0.39 0.50 10 4.8 123.09 2.54 0.27 0.54 0.68 10 4.8 123.09 3.81 0.25 0.74 0.94 3.5 10 4.8 123.09 4.44 0.25 0.86 1.09 10 5.13 0.33 127.16 4.91 0.29 1.16 1.42 10 6.41 1.61 141.77 5.46 0.41 2.03 2.22 10 7.69 2.89 154.87 5.95 0.48 2.91 2.88 10 8.97 4.17 166.81 6.39 0.54 3.80 3.47 10 10.26 5.46 177.92 6.79 0.59 4.72 4.01 10 11.54 6.74 188.19 7.16 0.63 5.69 4.53 10 10 12.82 8.02 197.81 7.51 0.67 6.70 5.03 E-8 Table E-11 Results using Ahrens method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 46.67 1.13 0.76 0.76 0.87 4.8 46.67 2.27 0.73 1.46 1.65 4.8 46.67 3.40 0.72 2.15 2.44 3.5 4.8 46.67 3.97 0.71 2.50 2.83 4 5.13 0.33 48.03 4.35 0.74 2.96 3.22 6.41 1.61 52.74 4.68 0.82 4.09 3.82 7.69 2.89 56.73 4.92 0.87 5.19 4.25 8.97 4.17 60.17 5.09 0.90 6.27 4.56 10.26 5.46 63.15 5.21 0.92 7.33 4.77 11.54 6.74 65.73 5.27 0.93 8.38 4.91 10 12.82 8.02 67.97 5.30 0.94 9.42 4.99 Table E-12 Results using Ahrens method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 72.33 1.23 0.79 0.79 0.96 4.8 72.33 2.45 0.75 1.50 1.85 4.8 72.33 3.68 0.74 2.22 2.73 3.5 4.8 72.33 4.30 0.74 2.58 3.17 5.13 0.33 74.86 4.72 0.76 3.05 3.60 6.41 1.61 83.06 5.19 0.84 4.18 4.34 6 7.69 2.89 90.29 5.60 0.88 5.28 4.92 8.97 4.17 96.77 5.95 0.91 6.35 5.40 10.26 5.46 102.69 6.25 0.93 7.41 5.79 11.54 6.74 108.06 6.52 0.94 8.46 6.13 10 12.82 8.02 113.00 6.76 0.95 9.49 6.42 E-9 Table E-13 Results using Ahrens method for a period of seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 4.8 97.94 1.26 0.80 0.80 1.00 4.8 97.94 2.51 0.77 1.53 1.93 4.8 97.94 3.77 0.76 2.27 2.85 3.5 4.8 97.94 4.39 0.75 2.63 3.31 5.13 0.33 101.13 4.85 0.78 3.11 3.77 6.41 1.61 112.57 5.37 0.85 4.23 4.55 7.69 2.89 122.80 5.84 0.89 5.33 5.18 8.97 4.17 132.07 6.25 0.91 6.40 5.71 8 10.26 5.46 140.62 6.62 0.93 7.45 6.17 11.54 6.74 148.50 6.96 0.94 8.50 6.57 10 12.82 8.02 155.85 7.27 0.95 9.53 6.93 Table E-14 Results using Ahrens method for a period of 10 seconds Storm H' = H T d L U U' Surge Kt H*Kt (ft) (s) (ft) (ft) (ft/s) (ft/s) (ft) (ft) 10 4.8 123.09 1.27 0.81 0.81 1.03 10 4.8 123.09 2.54 0.78 1.56 1.98 10 4.8 123.09 3.81 0.77 2.30 2.92 3.5 10 4.8 123.09 4.44 0.76 2.67 3.40 10 5.13 0.33 127.16 4.91 0.79 3.15 3.86 10 6.41 1.61 141.77 5.46 0.85 4.27 4.66 10 7.69 2.89 154.87 5.95 0.89 5.36 5.31 10 8.97 4.17 166.81 6.39 0.92 6.43 5.87 10 10.26 5.46 177.92 6.79 0.94 7.48 6.35 10 11.54 6.74 188.19 7.16 0.95 8.53 6.79 10 10 12.82 8.02 197.81 7.51 0.96 9.56 7.18 E-10 ... Response for a Reef Ball TM Submerged Breakwater System Offshore of Grand Cayman Island Author Dana S Arnouil Principal Advisor Lee E Harris, Ph.D., P.E As coastal development in the Cayman Islands... installed off Grand Cayman Island 17 Figure Reef Balls being deployed from a barge 18 Figure Reef Ball Breakwater after installation in Grand Cayman Island 18 Figure Forces acting on a. . .Shoreline Response for a Reef Ball TM Submerged Breakwater System Offshore of Grand Cayman Island A thesis by Dana Suzanne Arnouil Approved as to style and content by: