Coupling a 1D-local inertia 2D hydraulic model for flood dispatching simulation in a floodplain under joint control of multiple gates

A 2D local inertial equations model coupled with a 1D hydraulic model was established to simulate flood dispatching in river and flood detention areas. A simplified first-order accuracy finite volume method (FVM) solution was applied to the 2D model, and the source-type linking method was used at the coupling zones. The coupled model was calibrated by the historical flood process in the Daqing River basin, satisfactory agreements were obtained at the gauge points, and the flood arrival time was consistent with the recorded data. A flood dispatching simulation in the scenario of joint control of multiple gates was then performed. The operation sequence of the corresponding gates and the flood routing in each sub-basin were consistent with the dispatch rules. The convergence analysis based on the grid scale and convective acceleration terms was presented. The results indicated that a refined grid-scale yields better accuracy of the numerical solution, but this improvement is constrained by the resolution of the digital elevation model (DEM). In the lower range of Fr, the results of the hydraulic variables and the flood behaviours obtained by the local inertial equations model are identical to those of the full shallow-water equations (SWEs) model, which suggests that the approximation based on neglecting the convective acceleration terms is reasonable for the practical case of low velocity combined with an insignificant depth gradient.