STUDY ON BAR AND LOW-WATER CHANNEL MANAGEMENT BY USING FLOOD DISTURBANCE RESULTING FROM BAR EXCAVATION

Abstract

Recently, riparian vegetation has been extremely increasing and alternate bars covered with much vegetation can be seen as one of typical landscape in gravel-bed rivers. This situation brings about forestation in river which reduces the capacity of flood discharge, affects channel morphology by increasing of local roughness and obstructing to flow direction and produces remarkable bank erosion by strong meandering flow. This study aims to propose an effective method for channel management in such deteriorated gravel rivers by using flood disturbance. The bed excavation over the fixed gravel bar in the segment-1 zone of Watarasegawa River was conducted for the restriction of growth of riverine trees and the recovery of crooked low-water channel caused by leading flash flood flow. As results of the field survey and the numerical hydraulic simulation, it was confirmed that induced flood disturbance due to bed excavation on a stable forested gravel bar is one of effective measures for forestation controlling and channel management of gravel-bed river.