Dec 24

Upscaling the shallow water equations for fast flood modelling

Received 04 Dec 2019, Accepted 19 Aug 2020, Published online: 24 Dec 2020
Journal of Hydraulic Research

This paper presents a new sub-grid flood inundation model aimed at high computational performance. The model solves the two-dimensional shallow water equations (SWE) by a Godunov-type finite volume (FV) method that uses two nested meshes. Runtime computations are performed at a coarse computational mesh, while a fine mesh is used to incorporate fine resolution information into the solution at pre-processing level. New upscaling methods are separately derived for each of the terms in the SWE based on the integration of the governing equations over subdomains defined by the coarse resolution grid cells. The accuracy and performance of the model are tested through artificial and real-world test problems. Results showed that (i) for the same computational (coarse mesh) resolution, the inclusion of sub-grid information delivers more accurate results than a single-mesh FV model and (ii) for the same accuracy and at low resolution, the proposed methods improve computational performance.