科研之友
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摘要
Overtopping seawall is a physical process of seawater climbing over seawall after physical elements acting on the seawall such as astronomical tide, storm surge, and typhoon waves. In this paper, a fine risk level assessment system of overtopping seawall in Fujian coast, South China, is established, in which astronomical tide, storm surge and typhoon waves are coupled based on unstructured triangular meshes and high-resolution geographic data (location and elevation of seawall, shoreline and water depth) using ADCIRC+SWAN. The system can accurately depicts the complex terrain along Fujian coast in resolution of up to 50m in the nearshore grid. Using the simulated water level and wave parameters, a formula of wave runup is used to calculate the wave runup in front of each seawall. According to the comparison of the sum of total water level and wave runup and seawall elevation, the risk level of overtopping seawall is divided into five levels. We made a hindcast on the process of super Typhoon Usagi in 2013, the risk level of overtopping seawall is basically the same as that of post-disaster investigation. The results are accurate and shows that the risk assessment criteria and methods for overtopping seawall adopted in this study are feasible. On this basis, four different typhoon intensity scales were designed, 206 seawalls along Fujian coast have been assessed for overtopping seawall risk to investigate the impact of typhoon intensity on the risk of overtopping seawall. The results show that the impact of wave runup on the risk of overtopping seawall is higher than that of pure storm surge. The increase of storm surge is small with the enhance of typhoon intensity, and has small impact on the risk of overtopping seawall. The wave runup is generally high along the coast of Fujian Province, with the enhance of typhoon intensity, the wave runup will significantly increase the risk level of overtopping seawall, and attention should be paid to the disaster of seawall breaking caused by the shock of typhoon waves on the seawall. This study can provide a scientific basis for disaster prevention and mitigation in similar coastal areas.
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