Geomorphic changes and sediment yield dynamics in Alpine hillslopes: the role of surface temperature and rainfall intensity

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the upper soil layer. The investigation of geomorphic changes based on high-resolution elevation data combined with sediment estimation at the hillslope toe is particularly rare in Alpine areas, where freeze-thaw cycles strongly influence soil erosion. Furthermore, the combined role of surface temperature and rainfall intensity on sediment dynamics is not fully understood. Therefore, in this study, we aim to: i) assess multi-temporal geomorphic changes using high-resolution digital surface models (DSMs) reconstructed based on four unmanned aerial vehicle (UAV) surveys conducted between 2023 and 2025 on two avalanche-affected hillslope areas, ii) quantify the sediment collected at the hillslope toe during two summer seasons, and iii) investigate the influence of meteorological forcing on the sediment yield. Reconstructed differences of DSMs (30-05-2025 compared to 31-08-2023) showed that erosion volumes substantially exceed deposition. The resulting imbalance (>45%) indicates significant soil loss at the monitoring site. Similarly, a total of 8240 kg of soil was removed from Area 1 (910 m2) during the experimental period. Sediment yield had a significant positive correlation with land surface temperature (LST, r = 0.67), air temperature (r = 0.69) and rainfall intensity (r = 0.62). High LST, coupled with intense summer rainfall, was associated with increased sediment yield. Based on our results, we call for similar studies on other Alpine hillslopes to estimate erosion dynamics following extreme events and to implement nature-based solutions aimed at restoring avalanche-affected grasslands.

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