Are hydrologic-hydraulic coupling approaches able to reproduce Alex flash-flood dynamics and impacts on southeastern French headwaters?

International audienceDuring the last 5 years, south-eastern France experienced four deadly Mediterranean flash-floods: one in October 2015, two in November and December 2019 and the last one in October 2020, caused by the Storm Alex. The 2015 and 2019 events mostly affected small coastal catchments of the French Riviera ( 100 km2) and (ii) in the context of significant topographic changes due to the flood. A continuous semi-distributed rainfall-runoff model has been coupled with the Basilisk software, which is based on state-of-the-art 2D hydraulic modelling (well-balanced finite volume method for shallow water equations) with adaptive grid refinement. The streamflow series and inundation extents simulated have be compared with available observations gathered from post-event surveys with a particular focus on two places (Saint-Martin-Vésubie and Roquebilière)