Experimental study on wave attenuation and stability of ecological dike system composed of submerged breakwater, mangrove, and dike under storm surge

Abstract

Four tests were conducted to investigate the wave attenuation and dike stability effectiveness of a basic dike, a dike that combined with the submerged breakwater, with mangrove, and with both submerged breakwater and mangrove. Wave variation, hydrodynamic responses (wave scour, wave pressure, pore pressure), and dike stability were investigated. It was found that the submerged breakwater effectively reduced wave height and wave pressure in small wave conditions. However, the dike stability was not improved due to the balance between the positive effect of wave attenuation and the negative effect of water elevation increase in large wave conditions. The mangrove's wave attenuation effects were remarkable at both small and large wave conditions, leading to smaller hydrodynamic responses and ultimately contributing to a significant improvement in the dike stability. The combination of submerged breakwater and mangrove induced the best wave attenuation effect in shallow water with the smallest hydrodynamic responses. However, the presence of submerged breakwater amplified water elevation and significant wave height in deep water conditions, inducing stronger wave impact and more intense wave scour, ultimately resulting in the weaker stability of the dike.