石狩川中流部で発生した大規模河岸浸食の要因について

抄録

The middle reaches (KP77 - KP87) of the Ishikari River have been repeated meandering and cut-off. Although this part was improved, alternate bars present there and the low water channel is meandered. In this river section, which is just below the Sunagawa New Channel, sandbar(island) began to develop immediately after the 1969 completion of the channel work. This island grew and the riverbank suffered serious erosion. Bank protection work was executed as a countermeasure.

The sandbars are developed by several factors, and it caused the unusual situation of erosion on both the inner and outer banks. While it is true that outer bank erosion can generally be explained in relation to excess velocity, this is not so for inner bank erosion.

This paper used existing research on the relationship between erosion process and excess velocity in order to explain the erosion following the development of the sandbars. We also examined the section prone to erosion caused by changing of sandbar formation. We propose how to maintain the low-water channel in rivers where alternate bars develop at the middle reaches.