The phenomena of severe erosion over riverbed can be found in several major rivers of Taiwan in recent years. Continuous terrain variation of main channel by rapid riverbed erosion could be a great challenge to the function and safety of infrastructures over river, and the ecology environment of river, etc. The countermeasure to deal with rapid bedrock erosion is an urgent requirement. The project aims to realize the process of bedrock erosion, to propose a bedrock erosion model, and to develop a mobile-bed model with soft rock riverbed. The channel uplifted (maximum 10 meters vertically) by the 1999 Chi-Chi earthquake in the Ta-An River, which length is 1km in longitudinal direction and 500 meters in lateral direction, is choosing as the study site. The scope in the second year of this three-year project include the following: (1) literature review and data collection; (2) site investigation and measurement (including topographic survey, investigation on erosion of soft rock riverbed, riverbed erodibility, and bed rock erosion rate); (3) borehole exploration and sampling, borehole imaging, and laboratory tests; (4) development of an erosion model for soft rock riverbed; (5) modification of the EFA2D code to include a new rock river-bed erosion model in the rock scouring module.