A new approach for simulating the redistribution of soil particles by water erosion: A marker-in-cell model

There are currently no process‐based approaches that allow detailed spatial information on soil redistribution on hillslopes to be modeled at spatial scales that are appropriate for studying slope processes. In response, we developed a new type of soil‐erosion model, a marker‐in‐cell model, which simulates the redistribution of soil during rainfall events. The model is a hybrid of cell‐ and particle‐based techniques. A cell‐based model is used to determine the hydrology and hydraulics occurring at the cellular scale on the hillslope. Markers, representing sediment, are then moved through the grid according to these properties. The spatial pattern of erosion is determined directly by the properties of the markers. The model allows two‐dimensional spatial patterns of individual particle movement on a hillslope to be simulated within a computationally efficient framework. We have tested the model using data collected from a plot‐scale, rainfall‐simulation experiment. We measured the redistribution of137Cs‐rich tracer soil to resolve the spatial patterns of erosion caused by a single, high‐intensity, rainfall event. The model was able to recreate the key temporal and spatial aspects of the hydrology and hydraulics occurring on the plot, as well as the spatial redistribution of137Cs‐rich tracer soil. The development of the model was used to probe our understanding of how to investigate soil‐erosion processes. The lack of empirical underpinnings of the different model components highlighted the need to understand the spatiotemporal dynamics of soil erosion processes at the grain‐scale so to provide a better process‐based understanding of detachment and transport can be sought. Key Points Developed a new soil‐erosion model for hillslopes, a marker‐in‐cell model Recreates key aspects of hydrology, hydraulics, and spatial distribution of soil Provides a key feedback to our understanding of soil erosion processes