ABSTRACT
The photographs above show the same ravine at two locations. The left shows the situation where a vast amount of sediment is flowing into a reservoir. The photograph on the right shows a newly produced talus deposit at the foot of a landslide upstream from the location shown on the left. Such erosion of talus and riverbed is the source of the sediment runoff into the reservoir. In the steep upper reaches of the ravine, the main mode of sediment transportation is debris flow, and in the downstream reaches just up from the reservoir this mode shifts to individual particle transportation. Therefore, the sediment runoff model in such a ravine must take into account the mode change in sediment transportation during the runoff processes.
