Multi-Temporal UAV Surveys and Modelling of Soil Erosion in the Ca l'Isard Catchment, NE Spain

Abstract

This study investigates seasonal sediment dynamics in highly active Mediterranean mountain badlands by integrating multi-temporal Uncrewed Aerial Vehicle (UAV) surveys, and landscape evolution modelling (LEM) in the Ca l'Isard catchment (NE Spain). Four years (2020–2024) of high-resolution topographic data obtained from UAV revealed a consistent seasonal pattern; winter sediment accumulation (more than 0.5 m in incised channels), followed by summer export. In this sense, intense rainfall events are identified as the main drivers of soil detachment within the system. However, sediment transport through the drainage network towards the outlet points depends on the generation of sufficient runoff capable of mobilizing and transferring the previously detached material. The catchment exhibited an average substantial sediment yields (42–105 T/km² year), with interannual variability strongly linked to seasonal patterns. The LEM, calibrated using UAV-derived digital elevation models (DEMs), successfully replicated observed fluxes at both gully (1000 m²) and catchment scales (1.32 km²). The model correctly captured the annual and seasonal sediment dynamics, revealing strong Pearson correlations (0.7) between modelled and monitored data. Minor discrepancies emerged during extreme high-intensity rainfall events. Our findings demonstrate that badland erosion is governed by climatic factors (i.e., freezing–thawing cycles, high intensity rainfalls) and highlight the value of coupling field monitoring with process-based modelling to successfully analyse sediment dynamics in rapidly eroding badlands. Moreover, this framework provides a transferable approach for quantifying sediment dynamics in similar mountain regions.