SECULAR VARIATION SHAPE OF THE BIFURCATED CHANNELS IN THE SATSUNAI RIVER

Abstract

 In the Satsunai River of the Tokachi River system, in order to eliminate the forestation that progresses due to the flow conditions and the stabilization of the river channel, a medium-scale flash release is being carried out in late June in order to eliminate the progress of forestation due to the stabilization of the river channel by causing alternating mainstream changes in bifurcated channels from 2012. However, the cause of the alternating mainstream change in bifurcated channel has not been clarified. Therefore, in this study, for the purpose of examining the relationship between this phenomenon and the discharge and the shape of the bifurcated channels, these relationships are investigated using aerial photographs taken about twice a year. As a result, it was found that the larger discharge, the more likely it is that the alternating mainstream changes will occur and that the ease of this phenomenon differs depending on the shape of bifurcated channels.