Geomorphic Response and Large Wood Recruitment in the Vésubie Valley (France) Following Storm Alex

• DOI: 10.5194/egusphere-egu25-9727
• Publication Date: 2025-03-14T22:04:43Z
• Authors: Marco Martini; Vincenzo D'Agostino; Guillaume Piton

Extreme rainfall events in mountain catchments can induce substantial geomorphic changes, reshaping channels, hillslopes, and surrounding environments. These changes often widen active recruiting large wood from adjacent forests into sediment-laden flows, thereby increasing hazards such as altered flow patterns, sediment retention, logjam formation. Such dynamics exacerbate flood risks, particularly near infrastructure like bridge piers, dams weirs. Understanding the extent of forest areas contributing to recruitment predicting mobilized volumes is critical for effective hazard mitigation. This study examines response Vésubie catchment (392 km², south-east, France) Storm Alex (October 2020), which caused intense transport (i.e., bedload, debris floods flows) with strong recruitment. Using high-resolution aerial LiDAR data pre- post-storm surveys, valley bottom channels 43 tributaries (catchment sizes: 0.06–59 km²) were analysed at both 100-m reach scales via DEM Difference (DoD) technique. Diachronic canopy height models used assess cover loss, volume recruited was estimated based on French national inventory. Results revealed massive mobilization, net balances ranging -669 m³ ± 36 -341,575 3,625 -518,609 5,735 326,213 16,912 bottoms. culminated a total export 2.14 Mm³ 48,985 catchment. Tributary erosion varied by an order magnitude, displaying spatially consistent patterns pronounced variability channels. Erosion rates showed no distinct trend slope, high observed also low gradients. Conversely, deposition increased decreasing slopes (