Simulation of soil erosion in the Little Ice Age glacier foreland of the Zufallferner (South Tyrol, Italy) using Erosion-3D

Studies on the simulation of erosion in high alpine geosystems are still rare. Using the physically based soil erosion model Erosion3D (E3D), we show the simulation of fluvial erosion on a steep and unvegetated slope in a Little Ice Age (LIA) glacier foreland over several years. The study area is located in the proglacial area of the Zufallferner glacier in the Martell Valley (South Tyrol, Italy). The slope erosion is mainly due to fluvial erosion and process dynamics. A digital elevation model (DEM), various soil physical properties and precipitation data were used as input parameters for the E3D model. The DEMs were generated either from airborne LiDAR surveys (2013 and 2019) or from UAV-based structure-from-motion (SfM) photogrammetry (2023). Additional soil parameters required for E3D, such as bulk density, soil moisture, cover information, grain size distribution, erosion resistance, hydraulic roughness and the skin factor were determined. For this purpose, three rain simulations were carried out during a field campaign in August 2023 and corresponding soil samples were collected and analysed in the laboratory. The precipitation data as input for E3D comes from a data set that was created with a regional climate model (RCM). The Advanced Research WRF (ARW) module of the Weather Research and Forecasting (WRF) model (version 4.3) was used for the dynamic downscaling of the ERA5 climate data. This approach provided precipitation data for the Martell Valley with a temporal resolution of 15 minutes and a spatial resolution of 2x2 kilometres.

The E3D simulations were calibrated by comparing the modelled erosion volume of a specific slope section with the erosion volume derived from the DEMs of Difference (DoD) for 2023 and 2021. Spatial and temporal validation was then performed by comparing the E3D simulated erosion volumes with the volumes calculated from the corresponding DoDs (2013 to 2019 and 2019 to 2021). The E3D simulation results show that the net erosion volume of the entire slope section for each epoch agrees well with the calculated erosion volumes from the DoDs and is within their respective error ranges. These results confirm the suitability of the E3D model for simulating geomorphological activity on this slope within an LIA glacier foreland. Finally, we aim to improve the temporal resolution of geomorphological activity on the selected slope section using E3D simulations. By allowing an annual quantification of erosion between 2013 and 2023, the model enables a deeper understanding of the relationship between erosion dynamics and precipitation events.