INVESTIGATION TO RIVERBED FLUCTUATION USED BY UAV IN LOWER REACHES OF THE ASHIDA RIVER

Abstract

 The field investigations were performed 3 times at June, September and December in 2019. The shape of riverbed in this test zone is changed by the riverflow conditions both flood and dry. Using by UAV analyses, the 3-dimensional riverbed shape were made clear by used DMS. Judjing from the cross-sectional direction, the sandbank materials of this test zone are composed of 1) the sands at near place of the riverflow line, 2) the gravel materials at the central zone and 3) both sands and gravels at the begitation zone near the rightside bank. As shown the characteristic of the riverbed, at the meandering point from flat to swift current, the new sand materials sediment to the outside bend. As shown the result of numerical analyses for the small-scale flood less than about 70m³/sec, the sandy-particals of diameter less than 2.3mm are washed down over the tractive force of the flood.