Abstract
<jats:p>Mediterranean catchments are particularly prone to short-duration, high-intensity rainfall events that generate flash floods with significant impacts. Analyzing this type of event requires sub-daily hydrometric data in order to adequately capture their dynamics. This study investigates trends in flood characteristics across 38 Mediterranean basins in southern France, with an average size of 200km², using hourly discharge, radar rainfall, and reanalysis-derived soil moisture data over the period 1997–2024. Flood events are identified using a peaks-over-threshold approach and classified according to response time (flash-floods versus slower onset floods) and antecedent soil moisture conditions. Trends in flood peaks and direct runoff volumes are assessed using regional quantile regression after applying a spatiotemporal declustering procedure.Results indicate increasing magnitudes for both flash floods and slow-onset floods under saturated soil conditions. These increases are more pronounced for flood volumes than for peak discharges, with trend magnitudes approximately twice as large. However, these results should be interpreted with caution given the pronounced spatiotemporal variability of flood processes in Mediterranean environments, given that the detected trends are not statistically significant based on a regional bootstrap assessment.Overall, the results suggests that flood volume provides a more sensitive indicator of change than peak discharge in Mediterranean catchments. This underscores the importance of considering hourly data and process-based flood classification to improve the detection of evolving flood hazards in regions impacted by flash floods.</jats:p>