Modelling seasonal variation of gully erosion at the catchment scale

Geo-hydrological phenomena, including gullies, contribute significantly to soil erosion and land degradation. To address this, proper management of basins and hillslopes should consider the mechanism, timing, and location of gully development and how gullies interact with other hillslope processes. Yet, conventional modelling techniques for such processes are rare, frequently being limited to applications of only single processes and typically requiring high-resolution input data. Further, existing tools for characterizing basins and hillslopes tend to be based on static descriptions of geo-environmental conditions, and thus are not effective for modelling changes such as the seasonal triggering conditions of gully phenomena over time. This study proposes a method to integrate open remote sensing data (Sentinel-2) and an existing modelling tool (LANDPLANER) using simplified input data to better predict and forecast gullies' spatial and temporal occurrence. The study investigates the seasonal conditions responsible for the triggering of gullies at the catchment scale using different erosion modelling schema in the Toscana region of Central Italy. Geomorphological gully inventory data were collected and used as benchmarks to test the proposed approach. The results show that the occurrence of gully erosion in the studied region changes seasonally, and the proposed method was able to effectively discriminate spatial and temporal differences of the gully phenomena. The proposed method can be applied to similar regions worldwide, allowing for the investigation of gully erosion over time, even in places with limited data availability.