Numerical Simulation of Sheet and Rill Erosion using 2D Modelling

Heavy precipitation and resulting erosion of arable land present ongoing challenges in disaster prevention and agricultural management. This interdisciplinary topic is gaining significant attention due to increasing frequency of extreme events linked to climate change (IPCC, 2021; Robinson et al., 2021). According to Parkin et al. (2008), the largest amount of erosion results from extreme individual events.

State-of-the-art methods for simulating heavy precipitation events involve two-dimensional, hydrodynamic-numerical models (2D models) (LUBW, 2016). Traditional erosion simulations have relied on simplified hydraulic calculations, but in this study, the hydraulics, and forces acting on the soil were precisely calculated using a 2D model as the erosion simulation critically depends on the quality of this hydraulics (Morgan et al., 1998).

In contrast to well-known stream transport capacity approaches (e.g. Meyer-Peter & Müller), the Govers (1990) approach is effective for surface runoff and is particularly suitable for simulating soil erosion on arable land (Wang et al., 2019). Therefore, this approach was selected and integrated into the existing sediment transport module of the 2D HydroAS model.

To calibrate and validate the model, natural erosion events caused by heavy precipitation were recorded using an unmanned aerial vehicle (UAV) and analysed. Erosion areas were chosen and simulated using the combined model. The simulation results show both sheet and rill erosion. To assess the simulation results, the spatial distribution of the rill erosion and the erosion quantity were determined and compared with the natural events. Erosion on arable land can be simulated both spatially and quantitatively by coupling the Govers approach with the 2D HydroAS model. However, erosion quantities are highly dependent on the rill size and model resolution, representing minimum erosion.

Assessing sedimentation amount and its spatial distribution is also crucial for evaluating erosion risks due to heavy precipitation. The transfer of sediments from erosion areas to downstream ecosystems or settlements can negatively impact farmers, residents, and ecosystems. Sediment flow analysis is currently being conducted.