河原地形と河床材料分級から見られる流域特性

抄録

Topography and bed material distribution have much effect on river ecosystem. To understand determinant factors which have effects on topography and bed material distribution, we performed field observations on about 20 dry riverbeds in 4 rivers. At first, according to the results about topography, sharp flood hydrograph makes dry riverbed to two parts. And in straight channel which has enough sediment supply, or if gravel bar is in little lower side of the curvature of the river, dry riverbed has steep water edge. On contrast, in straight channel which doesn’t have enough sediment supply, dry riverbed has mild water edge.

Secondly, about bed material distribution, if sediment is not supplied by large flood but by small or middle flood because of effect of weir, there is the area which is consists of mostly gravels in higher area in dry riverbed. On contrast, sediment supply is even exist in small or middle flood, there is the area consist of gravels. If longitudinal slope is large, even small flood convey gravels over dry riverbed.