Field Performance of Permeable Breakwater

A semipermeable removable submerged breakwater was successfully installed at Virginia Beach, Virginia. Accretion of sand in the area between the device and the shoreline was minor. Excessive water depth above the structure allowed most of the incident wave energy to pass over. During a 13-month period, wave height, longshore current velocity, and sand size were monitored at the test site and at comparison areas to the north and south. Statistical tests show that there is no significant difference in the measured characteristics in the lee of the structure and at nearby comparison areas. Apparently an effective wave shadow zone was not created by the structure. Beach width measurements and the reslts of grain size analysis showed no significant relation to the structure. Increase in elevation of the bottom during the study period was l.42 ft (0.43 m) greater at the test site than at comparison areas. Corresponding sand volume is 20,000 cu yd (15,300 m³).