矢作川の瀬における2000年9月出水後の河床砂礫の粒径

Abstract

Size of the bed material was measured at riffles of seven stations in the Yahagi River, Aichi Prefecture, Honshu, Japan from October to December 2000 just after a great flash flood on 12 September 2000. The material was sampled from three layers of the bed : 1) the extreme surface layer, 2) the second layer beneath the extreme surface, and 3) the deep layer below ca. 30cm depth up to the depth of 45-50cm. The thickness of the extreme surface and the second layers was adjusted at the depth of maximum diameter of the gravel in each layer. The material was chiefly gravel, and its mean size tended to decrease downstream except the relatively fine size at a station slightly up an artificial reservoir. The size also tended to decrease from the extreme surface to the deep layer at every station. This vertical structure of material size did not show any apparent difference between the stations up and down the artificial reservoir.