Erosion Feedback System - Soil Thinning MMMF Model

Soil erosion rates on arable land often exceed the pace at which new soil is formed. This imbalance leads to soil thinning (i.e., truncation), whereby subsoil horizons and their underlying parent material become progressively closer to the land surface. As the subsurface horizons often have contrasting properties to the original topsoil, truncation-induced changes to the soil system might affect erosion rates and runoff formation. However, the potential feedbacks between soil erosion and soil thinning are poorly understood due to a lack of empirical data and the neglection of long-term erodibility dynamics in erosion simulation models. Here we present the code for a model-based exploration of the feedbacks between soil erosion by water and soil thinning. The model simulates annual runoff generation and soil losses on soil profiles with the Modified Morgan-Morgan-Finey model. As the original topsoil is successively removed, our model gradually mixes the soil properties from subsurface horizons into a 20 cm plough layer. The modelling framework is applied on a yearly time-step over a 500-year period, or until the plough layer reaches the bottom of the lowermost soil horizon. The model runs within a Monte Carlo simulation with 100 iterations per year to provide a forward error assessment of the simulated soil losses. Version 2.0 corrects an error in the lead drainage equation and in the layer mixing model. See the preprint discussion for further details: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-181/