Sandy Beach Profile Response to Sloping Seawalls: An Experimental Study

Abstract

Seawalls are commonly used as a tool for coastal defence worldwide. Most previous studies have considered the case of vertical seawalls and descriptions of existing seawalls, rather than the influence of different designs of sloping seawalls on beach erosion. In this study, laboratory investigations of an undistorted moveable bed model were conducted to determine the resulting beach profile of artificial sandy beaches. In the experiments, three different sloping seawalls were considered under erosive wave conditions with a 50-year return period. The coast of Northern Jiangsu Province, China, is used as a case study. To simulate natural conditions, similarity criteria are developed assuming that the energy dissipation per unit volume along the beach profile is uniform and that the wave properties can be properly scaled by Froude criteria. Field surveys of beach profile changes due to the storm surge induced by Typhoon 9711 were taken to validate the experimental model and good agreements were attained. Spatial profile configurations were studied by examining dominant profile features such as the break point bar and the scour trough on the seawall-backed profiles. Experimental results provided a reference for the maintenance of artificial sandy beaches and the design of seawalls on the coast of Northern Jiangsu Province, China.