Examination of a prefabricated submerged breakwater - preliminary results: Vero Beach, Florida, USA

Indian River County. Florida, USA has experienced significant shoreline erosion along portions of its coastline. In August 1996, a 915-m long prefabricated modular concrete unit submerged breakwater was deployed 70 m to 80 m offshore of the City of Vera Beach, Florida. The design of this narrow-crested submerged breakwater, installed as an erosion and wave energy reduction measure, incorporated lessons from a previous installation at Palm Beach, Florida (Dean et al., 1994a), and additional basin model tests (Dean et al., 1994b). To evaluate the effectiveness of the breakwater, a three-year monitoring program is being conducted by Indian River County and the US Army Corps of Engineers Waterways Experiment Station. The program includes quarterly hydrographic and topographic surveys, wave transmission, breakwater settlement, and scour measurements. The purpose of the program is to determine profile and areal volumetric changes, wave attenuation effects, structure stability and shoreline response relative to pre-project conditions. A unique challenge to the monitoring program includes the presence of an irregular natural limestone reef which causes variable wave transformation, and an inshore perched sand wedge which shifts onshore and offshore in response to seasonal variations and episodic events. Preliminary findings concerning shoreline response, sediment volumetric changes, wave transmission effects, and breakwater settlement relative to pre-project conditions are presented.