傾斜地域の河道における流木の挙動に関する実験

Abstract

Flood hazard in sloped areas is amplified by a large amount of drift wood that is conveyed in rushed waters, being supplied by river bank erosion and surface failure of mountain side during heavy rainfall. Drift wood damages river bank and structures by collisions against them, causes flooding by piling-up in river channels, and remains over farmland and urban areas to make restoration be difficult.Transport capacity of drift wood in stream channels was studied in an experimental flume with a rough bed covered with semi spheres. Experiments were conducted by using two kinds of drift wood models, specific gravities of which are a little greater and less than unity. Simultaneously, influence of drift wood on stream bank erosion and its flooding process was investigated in a newly designed experimental apparatus. An optical measurement system for 3-dimensional variation of stream channels was accomplished along with a personal computer program for its control and measurement. Drift wood models having simple forms, such as thin log shapes, proved to affect hardly bank erosion process.