Identification of a robust, efficient and practical finite-volume flood inundation simulator.

Schemes to support a robust and efficient two-dimensional flood inundation simulator based on an unstructured grid finite volume method are compared in the context of steady state and unsteady flow problems of practical importance where terrain is defined by high-resolution Digital Elevation Models (DEMs). The schemes adopt a Godunov-type approach and use Roe’s method to compute mass and momentum fluxes, but differ in formal accuracy and depending on whether conservative variables (CV) or primitive variables (PV) are used for variable reconstruction at cell faces. The CV scheme is found to be best suited to subcritical applications but unstable is cases where a supercritical wetting front advances over highly irregular topography, as in a dam-break application. The PV scheme is more robust, working in all practical applications considered, achieving greater accuracy than the CV scheme in supercritical flow applications, but yielding an order of magnitude more error in steady flow applications involving subcritical flow. A hybrid CV/PV scheme is therefore proposed.