Artificial sandbar, widely used in a lot of nourishment projects, is defined as the nearshore placement serving as an underwater berm for purpose of beach nourishment or stabilization. A series of experiments were conducted to investigate the wave-sandbar interactions under five irregular wave conditions of JOSWAP spectra. The wave surface elevations, velocity changes and turbidity were measured for analysis during the experiment. In general, the responses of a submerged artificial sandbar to irregular waves can be summarized as followings. The waves mainly broke on the crest of the sandbar in both spilling and plunging type and wave energy are redistributed under large waves. The turbidity grows when the incident wave height increases. The difference of turbulent kinetic energy between two ADVs augments with the increase of the incident wave height. The profile of sandbar has developed from a symmetrical shape to an asymmetrical shape with a steep landward slope and a mild seaward slope in large incident wave.
Coastal erosion, generally described as recession of coastal line and erosion of beach, is a common problem throughout the world. Particularly, China is one of the worst-hit countries with the erosion taking about 70% of the sandy coast and nearly all open silty coast. As a consequence, land loss, destruction of coastal construction and environment degradation are threatening the human life and property. To protect beach against erosion, both hard structures and soft defense measures are attempted. The hard structures, such as groins, offshore breakwaters and seawalls onshore, turn out to cause erosion locally or downstream more or less. Unlike hard structures, beach nourishment, as a soft measure to recharge the eroded coast with sediment from somewhere else, is one of the most effective and eco-friendly methods (Dean, 2005). In a beach nourishment project, the location of sediment placement is a key parameter. The sediment is usually supplemented to the beach onshore or offshore and the latter practice often develops a submerged sandbar offshore.