Tidal effect has a significant impact on flood routing in tidal rivers, conceptually taking on a resistant effect during flood tide and a dynamic effect during ebb tide. Two expressions were developed to reflect the tidal effect in this study, which consisted of the tidal wave velocity, the change rate of tidal level and the change in channel width. By incorporating the expressions into the momentum equation of the one-dimensional (1D) Saint-Venant equations, we propose that there are two types of momentum equations accounting for tidal effect. Based on the continuity equation and proposed momentum equations, two types of 1D hydrodynamic model for tidal rivers (namely the SVN-1 and -2 models) were constructed. In the case study, these models were applied to the tidal reach of the Qiantang River in China. The simulation results show that the SVN-1 and -2 models can obtain better accuracy than the SVN model based on the standard Saint-Venant equations, and that the SVN-1 model performs better than the SVN-2 model. Furthermore, the SVN-1 model can effectively capture water-level fluctuation, indicating that the expression employed is capable of accounting for tidal effect.
Keywords: 1D hydrodynamic model, channel geometry, flood routing, tidal effect, tidal river