Assessment of River Morphological Change for Co Chien Estuary Applying the CCHE2D Model

Abstract

Two-dimensional (2D) numerical models are useful tools for studying river morphology. Frequently, 2D numerical models are often applied to predict the impacts of the artificial changes to rivers and estuaries. These changes may be caused by altered watershed hydrology, variations in the sediment supply and the construction of artificial works such as dams, embankments and tidal gutters. The aim of this study was to apply the CCHE2D model in simulating riverbed morphological variation in the Co Chien Estuary of Vietnam with complex morphology under the combined impacts of hydrodynamic processes such as waves, flow field, tidal currents and sediment transport. First, the proposed model was calibrated using water surface level and current speed data during dry and flood seasons in 2010. Calibrated results showed satisfactory coefficients (root mean square error smaller than 0.10 and Brier skill score (BSS) criteria varying between 0.63 and 0.94). Second, the proposed model is applied to simulate riverbed level variation for Co Chien Estuary after the 6-year flood (2010–2015). The results were evaluated comparing deviations between simulated and measured elevations at multiple monitoring cross sections and longitudinal bed profiles after the 6-year flood. Compared results confirmed that the proposed model is suitable for simulating hydrodynamic processes and riverbed morphological changes in the study area with BSS criteria greater than 0.68. The proposed model is a useful tool to help efficiently manage resources and minimizing the unwanted influences of wave, current, tide and sediment transport process.