Impact of Oyster Reefs on Wave Climate along a Marsh Edge

Jacob Bushey1, Matthew Abraham Reidenbach2, Sara Hogan2 and William Kearney3, (1)United States, (2)University of Virginia, Department of Environmental Sciences, Charlottesville, United States, (3)University of Virginia, Environmental Sciences, United States
Abstract:
The Virginia Coast Reserve (VCR) is a highly diverse coastal system on the Mid-Atlantic Coast. Rising seas allow salt marshes in the VCR to accrete vertically, but also allow for larger waves, and wave driven shear stress is the key driver behind marsh edge erosion. Artificial oyster reefs are commonly used to attenuate wave energy and reduce rates of erosion, simultaneously offering biological services to the ecosystem. This study was designed to quantify the ability of intertidal oyster reefs to attenuate wave energy at the marsh edge. A series of oyster reefs were constructed approximately 20 m offshore and adjacent to an eroding marsh edge. Wave height was measured on both sides of a restored oyster reef as well as at a control site adjacent to the reef. Wave conditions, water velocities and suspended sediment concentrations were measured along the marsh edge. The differences in wave height were used to determine the percent attenuation. Results show that in water depths of less than 0.5m, wave height was attenuated by <10%. At depths greater than 1m, wave height attenuated by >15%. The greatest attenuation was observed when water depths were between 0.5m and 1m, with greater than 30% attenuation. Since wind-driven waves are the primary driver of marsh edge erosion for low elevation salt marshes and low elevation salt marshes have edge scarp heights between 0.5m-1m above mean sea level, the data suggests that artificial oyster reefs are effective at attenuating wave energy in this critical range.