Abstract
The hydrological field campaigns performed during the HyMeX EOP (2011–2014), in the framework of the Cévennes-Vivarais Mediterranean Hydrometeorological Observatory and the ANR FloodScale project, aimed to improve our understanding of the active hydrological processes triggering flash floods, as well as our skill in modelling such floods. The campaigns were based on a multi-scale observation strategy: 1) plot or hillslope experimentations brought observations about the sub-surface flow and the bedrock permeability, the soil moisture variability in time and space, for several land uses; 2) nested small catchments (