EFFECTS OF LATERAL EROSION BY WIND WAVES IN COUPLED BARRIER ISLAND-MARSH SYSTEMS

Until recently marsh loss was largely thought to be due to an inability for vertical accretion rates to match rates of sea level rise. However, recent work points to marsh edge erosion by wind waves as the leading cause of marsh loss worldwide. To better understand the response of coastal ecosystems to future changes in sea level and storm intensity, we further develop the coupled barrier-island marsh evolution model GEOMBEST+. Using the relationship between wave height, fetch, and wind speed we add marsh edge erosion to the model and provide a more physical formulation for bay bottom erosion. Considering marshes in isolation from barrier islands, previous research (Mariotti and Fagherazzi, 2013) suggests that backbarrier marshes are unstable and tend to erode away completely or grow laterally to fill adjacent basins. Previous GEOMBEST+ experiments (Walters et al 2014) suggest that in the presence of an influx of overwash sediment from an adjacent barrier island, a long-lasting narrow marsh state exists. Here we present the results of new GEOMBEST+ model experiments that address how this alternate state is affected by the addition of lateral erosion by wind waves. As the new formulation for bay bottom erosion has no effect on marsh width, model experiments explore the effects of lateral erosion on the frequency and characteristic time and space scales of the narrow marsh state.