| Riverbed degradation and subsequent exposure of clay layer have occurred in the Kiso River due to less supply of sediment materials from upstream basins. The loss of the clay layer resulted in acute erosions of underlying sandy deposits. Ultimately, local scouring with about 20 m in maximum water depth was occurred. In this study, we investigated the riverbed morphology and found a broad exposure of the clay layer and two large-sized local scouring in the Kiso River. In addition, we simulated the two-dimensional bed variation to evaluate the generating factor and process of the local scouring. The simulation indicated that the local scouring became enlarged because the edge of the clay layer has same function as riverbed girdle. |
