Combining remotely sensed data and numerical modeling to investigate the impacts of vegetation on barrier island erosion

The use of high-fidelity numerical models for storm-induced beach and dune erosion is becoming more commonplace. These models explicitly compute wave transformation, currents, and sediment transport fairly accurately in the nearshore, but do not fully account for some physical controls, such as vegetation, that alter erosion processes during large storm events when barrier islands are overwashed or inundated. Methods that exist to account for the impact of vegetation on dune and island evolution have not been adequately tested, in part due to a lack of observations of spatially and temporally varying subaerial barrier island vegetation coverage. Here we use a new dataset that defines regions of vegetation density derived from satellite images with good spatial and temporal resolution to investigate 1) methods for incorporating this data into numerical models, and 2) the influence of vegetation patterns on topographic evolution during storms. We use pre- and post-storm topographic surveys from multiple storms over the last decade to investigate the sensitivity of the model results to the incorporation of vegetation presence and density. We focus on Dauphin Island, a 26 km long barrier island off the coast of Alabama in the Northern Gulf of Mexico. The island has been devastated by multiple tropical storms and offers an interesting contrast between a developed, highly vegetated island on the eastern end and an unmodified, low-lying western end absent of dense vegetation.