Abstract
In the upstream of Ishikari River whose riverbed is formed with gravels on the soft bedrock, recently, the sudden riverbed degradation has been observed, which may cause damages on revetment works and bridge piers, or losses of sermon`s spawning beds. Therefore, the Asahikawa Development Department which manages the river has conducted some hydraulic experiments to establish a countermeasure for the riverbed degradation.
While the former experiments clarified the effectiveness of the countermeasure, the authors, for further study, conducted an experiment which reproduces soft bedrock erosion. The experiment consists of two stages, which are the pre-experiment for choosing the soft bedrock material to reproduce the one on site, and the large-scale experiment to evaluate the countermeasure. The experimental results indicated that the countermeasure is safe against the bedrock erosion, and the erosion encourages roughness jump and sand deposition.
