Modeling of Vertical and Lateral Erosion on the Chosui River, Taiwan

Chosui River in Taiwan has been subject to a large amount of yearly vertical and lateral geomorphic changes. Costly efforts have been made over the years for river maintenance, water delivery, and flood prevention. In the last decade or so, extensive studies have been initiated to seek whether numerical models may be used to predict river morphological changes so that potential risk areas may be identified, project alternatives may be evaluated, and project benefits may be assessed. In this study, the two-dimensional (2D) mobile-bed model SRH-2D, with its bank erosion capability, is used to simulate a 16.7-kilometer reach on the Chosui River. This reach is relatively complex and has experienced large lateral changes. There are measured data available for comparisons so that the numerical model may be evaluated. After a combined calibration and verification model over a seven-year period, the study shows that the coupled river channel and bank erosion modeling correctly captured major erosion and deposition locations and trends. It demonstrates that SRH-2D may be used for identifying potential erosion sites and providing information for river maintenance planning. Also, the bank erosion module is capable of predicting the bank retreat rate reasonably with only one major calibration parameter: bank erodibility.