Numerical simulations of bedrock erosion around the bridge

There are bedrock erosion problems in western Taiwan. A bridge or an instream structure in the river often affects the sediment transport, and then leads to severe bed change and local scour problems. Bedrock channels lack a continuous cover of alluvial sediments over the long term. When the bed armor layer flushed away, it makes the bedrock exposed, and then increases the channel incision. There are significant bedrock erosion problems in the nearby area of Chungcheng Bridge in Touchien River, Taiwan. However, hydraulic models of past few decades often aimed at the sediment transport of alluvial channel. The numerical simulation of bedrock erosion is an important issue for the planning of stable countermeasures. In this study, a two-dimensional mobile-bed model, called CCHE2D is adopted to simulate the bedrock erosion process in the nearby area of Chungcheng Bridge. A stream power with flow shear stress method of bedrock incision rate formula is established in the model. The results show that the model has the capability of simulating flow field and morphological changes in study reach.