XBEACH SIMULATION OF HYBRID COASTAL PROTECTION: A GALVESTON SEAWALL TEST CASE
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The City of Galveston is protected from extreme storm impact by a 17-km concrete seawall facing the Gulf of Mexico. Recent studies have shown that the seawall may not be sufficient to protect against a 100-year design storm. Since raising the seawall disconnects the city from the beach and may be very costly, a hybrid approach is explored in which the existing hard structure is fronted and covered by a layer of sand. By means of numerical simulationsthe hydro- and morphodynamic effects of adding a sand cover to the Galveston Seawall under extreme storm conditions are further investigated. It was found that by adding a sand cover over the seawall, maximum dissipation is spread over a larger cross-shore extent. This led to the reduction of the wave height at the face of the hybrid structure, as well as the generation of more wave-induced setup. Different hybrid design configurations were simulated, which varied in sand cover dimensions. Differences in wave attenuation, wave-induced setup and required sand cover volumes are discussed. It was found that a hybrid measure shows potential in reducing wave impact during extreme storm events, thereby reducing the required elevation of the Galveston Seawall.
