Author(s): Yasuyuki Hirai; Kei Karasawa; Yasuharu Watanabe
Linked Author(s): Yasuharu Watanabe
Keywords: Sandbar; Water course; Falling[recession]stage; Tractive force; Hydraulic experiment
Abstract: The purpose of this study was to clarify the formation and development processes of a water course in the falling stage of flood discharge. A hydraulic model experiment was conducted to observe how a water course forms in the recession stage in a river channel with sandbars. The experiment was conducted for three basic flood hydrograph waveforms, as well as for additional cases by varying the falling time and the duration of the minimum discharge. The water course formation and development conditions were studied by measuring the riverbed forms after the passage of running water. The grain size distribution of the riverbed that formed in each case was also measured. In addition, temporal changes in the bed shear stress from the depth of the water course were estimated using image analysis during its formation process. The results revealed that the water course formed more clearly for the hydrograph with a longer low-flow period in the recession stage. It was suggested that the duration of the low flow rate affected the water course formation.
Year: 2010