2004 Volume 48 Pages 985-990
This paper describes the relation among the flood, topographical features and the vegetated region on the floodplain at Honmura in the Kita River. The past changes in topographical features and the vegetated region were measured from the aerial photographs. The grain sizes of the gravels were investigated at the several points on the floodplain. As a result, the followings have been understood. 1) Gravels piled up due to the flood in 1997, fine sand mixing clay piled up during 1983-1997 and gravels piled up due to the flood in 1982 are accumulated in the vicinity of the 11.7km section. 2) Gravels on the bare ground of floodplain moved for the flood of 2, 000m3/s in discharge. However, the large scale movement of bed materials did not occur for the flood of 3, 500m3/s in discharge if the floodplain was covered by the thick vegetation. 3) The forest zone in the river bend had the effect that the topographical feature of floodplain was stabilized. 4) The state that the herbaceous vegetation covered the whole area of the floodplain, recovered from the state of the bare ground when the condition of 1, 600m3/s or less in discharge continued for two and half years. 5) The state with thick vegetation recovered when the condition of 1, 800m3/s or less in discharge continued for five years.
