Technical Studies

Due to the effects of environmental changes (e.g., earthquake uplift, climate change, etc.) or human activities (e.g., hydraulic engineering, infrastructures construction, gravel mining, etc.), bedrock scouring and stream instability were induced in several major rivers of western Taiwan. Most of the major rivers in western Taiwan flow over the Western Foothills which composed of weak sedimentary rocks. Once the weak rocks lost the protection from overlain armor layer, the channel bedrock erosion progressed rapidly. In order to properly manage the issue of rapid morphological change in river reaches, related works on the subject of weak bedrock erosion carried out in this three-years project, including literature review and data collection, investigation of erosive characteristics of bedrock and rock riverbank, development of erosion rate model for weak rock riverbed and riverbank, and development of guidelines for evaluation of bedrock scour and strategy suggestion for bedrock scour countermeasures. This year is the first executive year of the three-year project. The object is to establish the research methodology and useful data related to erosion rate model. The severely eroded bedrock reach in both the Bazhang River and the Daan River were selected as study sites, which were chosen from the major rivers in western Taiwan after the comparison of their morphological change of bedrock erosive history and characteristics of bedrock erosion. There are other three reaches in the Dahan River, the Dajia River, and the Jhuoshuei River were adopted as supplementary sites. Historical bedrock erosion data and rock erodibility index will be collected and determined, respectively, for erosion rate model development at the supplementary sites.