| Summary: | The current study is concentrated in modeling the cross-shore beach profile evolution and severe erosion of the dune (overwash) of a restored barrier island due to Hurricanes Gustav (2008) and Ike (2008) in coastal Louisiana. Pre-storm and post-storm survey data sets of Chaland Headland located in Plaquemines Parish, LA, were analyzed and categorized based on the overwash processes, and numerically modeled using SBEACH (Storm-induced BEAch CHange). The model results were compared with the measured topographic data. A total of 10 survey profiles were used in this study.
SBEACH simulates cross-shore beach, berm and dune erosion produced by storm waves and water levels. The model was calibrated for site specific conditions; sensitivity tests were conducted with varying water levels, wave heights and median grain sizes. Hurricanes Gustav and Ike forcing conditions were applied and the model profiles were then compared with survey profiles.
It was found that, although SBEACH is capable of reproducing the shape of the post-storm profiles to some extent, the amount of measured erosion on the foreshore slopes of the measured beach profile is much greater than the modeled erosion. Dune erosion of the measured profiles is also greater than the modeled profiles. It is also found that some of the empirical parameters of SBEACH need to be adjusted beyond the recommended values to obtain better simulation results.
SBEACH does not account for any longshore sediment transport due to longshore currents. Also the surge level gradient across the profile is not considered in the model. In general, the beach profile evolution processes are three-dimensional and complex. Although a one dimensional model could be a helpful tool in the preliminary stages of a project to estimate the shape of the post-storm profile, the three dimensional effects should be considered to obtain accurate results, in particular under hurricane conditions.
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