Technical Studies

Owing 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 is the second executive year of the three-year project. Six major tasks were executed in this year: 1) Data and literature review; 2) Measurement of erosion data in the Bazhang River and the Daan River; 3) Field investigation for surface geology, erodibility index of bedrock, and characteristics of bedrock erosion; 4) Development and verification of erosion rate model for weak rock riverbed; 5) Development and verification of erosion rate model for weak rock riverbank; 6) Calibration of erosion rate model for riverbed and riverbank.