Author(s): Martin Utz; Leopold Utz

Linked Author(s): Martin Utz

Keywords: Shallow water; Bedload transport; Implicit time discretization; Finite volume

Abstract: This study was performed in order to test if the shallow water model of the open-source simulator Dumux can be used to simulate rainfall runoff. The Dumux model for two-dimensional shallow water equations applies a fully implicit time discretization in combination with a first-order finite volume discretization in space. The scheme was originally developed for the simulation of unsteady flow in rivers, in particular inland waterways. For these applications the implicit solver allows to apply large time steps (Courant number >> 1). This reduces the computing time compared to explicit models. In combination with an efficient MPI-parallelization Dumux can simulate over thousand seconds unsteady flow in just one second. The excellent performance of Dumux is an important feature for river engineering, since the influence of different hydraulic measures can be simulated more rapidly. The performance of the Dumux shallow water model makes its application also interesting for rainfall runoff modelling. Furthermore, Dumux contains a comprehensive library of subsurface flow models and focuses on model coupling. Model coupling again can be used to simulate the interaction between surface flow and subsurface flow models. For example, this would be interesting for hillslope hydrology, where the existing shallow water model can be coupled with a subsurface flow model (e.g. Richards equation) to simulate rainfall, infiltration and surface run-off in combination with subsurface flow (interflow). In the first part, we present results of different benchmarks to examine the potential of Dumux for rainfall runoff modelling. We investigate if large time steps (Courant number >> 1) can be applied within rainfall runoff modelling to reduce the computing time. We also examine if a high-er mesh resolution in combination with an increasing number of cores can be used to improve the results of the first-order spatial discretization without significantly increasing the computing time. In the second part we present a bed load transport model for Dumux. This model is based on the shallow water model and uses a fully coupled approach to couple shallow water equations and the sediment balance equation. We show different benchmarks, including cases where the bed load transport model allows also to simulate a high interaction between flow and sediment transport.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022SS725

Year: 2022