Influence of sediment composition on breaching process of model river levee

In recent years, floods have been occurring in various places due to the effects of climate change, and one of the serious damages arises due to the breach of river levees. As in the case of western Japan heavy rains in July 2018, a levee breach can cause serious damage to house and people in the basin. Therefore, it is an urgent task to understand the mechanism of river levee breach for disaster prevention and mitigation. The authors have investigated experimentally the breach process of model levee composed of sand, clay and gravel. We also examined the effect of clay and gravel on the collapse mechanism of levee by conducting experiments with various content ratio of clay and gravel. In this study, we examined how the erosion process of levee in which clay and gravel were contained is different from that only made of sand, and the significance of the existence of clay and gravel in the levee is made clear.