ANALYSIS OF LONG TERM CHANGE PROPERTIES AT A STEEP RIVER

Abstract

When it comes to flood, increased river flow causes stream diversion with bank erosion. Therefore, we have built revetments in order to keep the channel flow stable. However, the construction of the protection which narrows the flow width caused an increase of bed shear stress and a degradation of bed. In order to solve these problems, it is necessary to permit river channel change to some extent. However, the knowledge about the long-term movement of river channels accompanying bank erosion is insufficient.

This research investigates a river channel meandering process from the past to the present using the topographical maps. We found that river works revetments mitigate the degree of meandering in the present river. The width of channel is the almost same as the past meandering width in general. However, the old channel shown by the aerial photograph locates at protected area. Therefore, it is necessary to consider the danger of riverbank erosion on a long-term management plan.