Shoreline Position (m) 



100 200 300 400 



Distance Alongshore (m) 



500 



Fig. 6. Shoreline evolution behind a detached breakwater 

 with variable wave transmission 



giving strong support to the newly developed wave calculation procedure. As 

 an empirical test of the enhanced model, a simulation was made of the shore- 

 line evolution which occurred after installation of six detached breakwaters 

 at Holly Beach, Louisiana. 



APPLICATION TO HOLLY BEACH, LOUISIANA 

 Site Description 



Holly Beach is located near the Texas - Louisiana border on the chenier 

 plain along an east-west oriented coast (Fig. 7). This coast is undergoing 

 chronic erosion resulting from limited sand supply, relative sea level rise 

 caused in part by regional subsidence, and seasonal impacts from frequent 

 extratropical cyclones (cold fronts) occurring in winter and hurricanes 

 developing in the late summer and early fall. The wave energy is typically 

 low, with average an breaking wave height of 50 cm and a period of 5 sec 

 (Nakashima et al . 1987). The tidal environment is microtidal ; the diurnal 

 tides have a mean range of 60 cm and a spring tide range of 74 cm. Annual 

 wind data indicate that locally generated wind waves dominate from the south 



50 



