Two-dimensional time dependent hurricane overwash and erosion modeling at Santa Rosa Island |
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| Authors: | RT McCall JSM Van Thiel de Vries NG Plant AR Van Dongeren JA Roelvink DM Thompson AJHM Reniers |
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| Institution: | 1. Deltares (formerly Delft Hydraulics), Delft, The Netherlands;2. Department of Civil Engineering and Geosciences, Delft University of Technology, Delft, The Netherlands;3. Center for Coastal & Watershed Studies, USGS, St. Petersburg, Florida, USA;4. Unesco-IHE Institute for Water Education, Delft, The Netherlands;5. Rosenstiel School of Marine and Atmospheric Science, University of Miami, Florida, USA |
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| Abstract: | A 2DH numerical, model which is capable of computing nearshore circulation and morphodynamics, including dune erosion, breaching and overwash, is used to simulate overwash caused by Hurricane Ivan (2004) on a barrier island. The model is forced using parametric wave and surge time series based on field data and large-scale numerical model results. The model predicted beach face and dune erosion reasonably well as well as the development of washover fans. Furthermore, the model demonstrated considerable quantitative skill (upwards of 66% of variance explained, maximum bias − 0.21 m) in hindcasting the post-storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied. The prediction skill ranged between 0.66 and 0.77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied. The sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay. The model sensitivity to the sheet flow sediment transport limiter, which served as a proxy for unknown factors controlling the resistance to erosion, was significantly greater than the sensitivity to the hydraulic forcing parameters. If no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response. |
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| Keywords: | Overwash Hurricane impact XBeach Dune erosion Numerical modeling Morphodynamics Infragravity waves |
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