MITIGATIONS OF RIVER WIDTH REDUCTION AND LARGE SCALE SANDBAR FORMATION BY REPEATEDLY FLUSHING OF SAND INTAKE WEIRS

Abstract

In the Hii River, there are some intake weirs which are made by river bed materials of sands. Since the sand intake weirs are eroded and scoured by flood flows, flushing of the sand intake weirs by a series of floods and rebuilding them after the floods induces formation of large scale sandbars and reduction of channel widths at downstream of the sand intake weirs. Therefore, first we investigated effects of flushing of the sand intake weirs on channel widths reduction by using observed annual data and the general Bottom Velocity Computation (GBVC) method which was developed by Uchida and Fukuoka. Next, we discussed how to rebuild the sand intake weirs after floods for minimizing effects of the sand intake weirs flushing on channel widths reduction.