RESTORATION OF SELF-SUSTAINING GRAVEL BAR AT TAMAGASHI AREA IN THE ASAHI RIVER

Abstract

In the Asahi River, after the dam construction, flood disturbances on the river bed have reduced and stable vegetated areas have expanded on river bars. Because a development of riparian forest has reduced the number of gravel bars, peculiar river environments such as a diversity of river and a natural ecosystem have decreased. Furthermore, the developed riparian forest has degraded a riverscape and has reduced flood capacity. Artificial removal of vegetation is usually adopted to reproduce gravel bar, however self-sustaining gravel bar can not be well maintained in some cases. Therefore, to restore self-sustaining gravel bar is very important engineering problem. In this study, the effective management methods to maintain gravel bar at Tamagashi area in the Asahi River were proposed and the effects of them were investigated using two-dimensional flood flow simulation.