Abstract
Surface flow routing is an important component in hydrologic and hydrodynamic research. Based on a literature review and comparing the different coupling models (the hydrologic model and hydrodynamic model), a multigrid dynamic bidirectional coupled surface flow routing model (M-DBCM), consisting of diffusion wave equations (DWEs) and shallow water equations (SWEs), is proposed herein based on grids with different resolutions. DWEs were applied to obtain runoff routing in coarse grid regions to improve the computational efficiency, while the DWEs and SWEs were bidirectionally coupled to detail the flood dynamics in fine grid regions to obtain good accuracy. In fine grid zones, the DWEs and SWEs were connected by an internal moving boundary, which ensured the conservation of mass and momentum through the internal moving boundary. The DWEs and SWEs were solved by using the time explicit scheme, and different time steps were adopted in regions with different grid sizes. The proposed M-DBCM was validated via three cases, and the results showed that the M-DBCM can effectively simulate the process of surface flow routing, which had reliable computational efficiency while maintaining satisfactory simulation accuracy. The rainfall runoff in the Goodwin Creek Watershed was simulated based on the proposed M-DBCM. The results showed that the discharge hydrographs simulated by the M-DBCM were closer to the measured data, and the simulation results were more realistic and reliable, which will be useful in assisting flood mitigation and management.
Highlights
Surface flow routing, consisting of overland and channel flow routing, refers to the process in which a precipitation-generated surface runoff moves over the land surface from the source to an outlet
In M-DBCM, the shallow water equations (SWEs) and diffusion wave equations (DWEs) were solved synchronously, which ensured the conservation of mass and momentum flux on the coupled boundary, and the numerical accuracy was improved compared with the external coupling model
The results showed that the hydrographs from the M-DBCM and 2D hydrodynamic model matched the peak arriving times and the peak discharges very well, except for a few stations, which showed the rationality of the M-DBCM proposed in this study
Summary
Surface flow routing, consisting of overland and channel flow routing, refers to the process in which a precipitation-generated surface runoff moves over the land surface from the source to an outlet. An accurate description of surface flow routing plays an important role in a variety of hydrologic, hydrodynamic, and ecological problems, such as flood routing, rainfall runoff modeling, sediment transport, pollutant convection diffusion, and so on [1,2]. Simulating the surface flow routing is key to minimizing the potential human and property damage from floods. Many researchers have studied rainfall–runoff mechanisms and ways to reduce the loss caused by floods, using physically-based hydrologic and hydrodynamic models for simulations [4,5,6,7]. The hydrologic model has been widely used for overland flows but rarely expanded to the simulation of flood propagation processes. The hydrodynamic model has played a major role in simulating inundation processes, which have been
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