ON THE DIMENSIONLESS CRITICAL TRACTIVE FORCE FOR STABLE LOW-WATER CHANNEL OF GRAVEL AND SAND BED ALLUVIAL RIVERS

Abstract

This study is concerned with the dimensionless tractive force τ*S for stable low-water channel of gravel and sand bed alluvial rivers. A non-dimensional parameter α contained in the τ*S -relation, that has been obtained theoretically by the author, is examined with use of existing data of natural Japanese and overseas rivers as well as three Japanese A-class rivers in Kyushu, so that such relationship as α=KI-1/2 is identified and the value of coefficient K is simultaneously estimated. Then, the obtained τ*S-relation compares with τ*S for the above mentioned field data, and the validity of the τ*S-relation is confirmed. In addition, the stability of low-water channel of the Onga River after the flood in 2012, when maximum past flood has occurred, is examined by means of the τ*S-relation, so that river sections required close attention for river managements in the Onga River are identified.