Author(s): Kayo Asami; Akihiko Nakayama; Takeshi Kaw Atani; Ichiro Fujita
Keywords: River vegetation; Anaphalis margaritacea; Refugia; LES; Flood flows
Abstract: In order to find mechanisms of maintaining cobble bars found along many Japanese rivers, we have conducted a field survey, two-dimensional flow analysis and LES simulation of flood flows of various discharges at a mid reach of Ibogawa River in W estern Japan. The prominent feature of the river reach studied by the present work is the cobble bar on the inner bank of an acute bend after a steep sloped riffle but there are a number of other features such as large boulders and a sudden drop. The roles of these features are investigated by the field survey and the simulation. The simulation under various conditions indicate that it is the sharp bend and a relatively steep slope that create a bar on the inner bank where flow of slow speed occurs during medium to large floods.