2019 Volume 25 Pages 759-764
In this study, we aimed to clarify the channel characteristics of the soft rocks riverbed by carrying out various field survey in the Usui River where the riverbed has progressed. We surveyed the physical conditions such as erosion rate, strength, deterioration status, and discharge condition of the weir on the soft rock bed. In addition, Fish and benthic surveys were also conducted. As the result of the survey about deterioration situation, soft rock caused slaking two days after draining the water in the river channel. Therefore, it was found that the wet and dry condition associated with the water level change is one of the causes of the riverbed degradation. Further, it was clarified from the results of the biological surveys that habitat species and density is influenced by exposure rate. From the above survey results, it was possible to grasp the channel characteristics of the soft rock riverbed in the Usui River.
