Abstract

To estimate the scour depth and riverbed variation in steep channels is important for flood disaster prevention. The riverbed material in steep channels which has a grain extremely broad range of sizes provides useful information on riverbed scouring and variation. But reasonable methods for estimating grain-size distribution are not established and needed for steep channel design.

In this study, we analyzed past flood data and bed variation data of the Joganji River and carried out field experiments in the floodplain of the Joganji River. From this research, we clarified the characteristics of bed variation in a channel gravel bed and the grain size group that determines riverbed stability. Furthermore, we found that digital image analysis of a riverbed’s surface provide a useful means for determining grain-size distribution in a gravel bed river.

Keywords: gravel bed rivers, field experiments, bed variation ,bed stability, grain size distribution, tractive force