Articles | Volume 22, issue 10
Research article
16 Oct 2018
Research article |  | 16 Oct 2018

Using a multi-hypothesis framework to improve the understanding of flow dynamics during flash floods

Audrey Douinot, Hélène Roux, Pierre-André Garambois, and Denis Dartus

Abstract. A method of multiple working hypotheses was applied to a range of catchments in the Mediterranean area to analyse different types of possible flow dynamics in soils during flash flood events. The distributed, process-oriented model, MARINE, was used to test several representations of subsurface flows, including flows at depth in fractured bedrock and flows through preferential pathways in macropores. Results showed the contrasting performances of the submitted models, revealing different hydrological behaviours among the catchment set. The benchmark study offered a characterisation of the catchments' reactivity through the description of the hydrograph formation. The quantification of the different flow processes (surface and intra-soil flows) was consistent with the scarce in situ observations, but it remains uncertain as a result of an equifinality issue. The spatial description of the simulated flows over the catchments, made available by the model, enabled the identification of counterbalancing effects between internal flow processes, including the compensation for the water transit time in the hillslopes and in the drainage network. New insights are finally proposed in the form of setting up strategic monitoring and calibration constraints.

Short summary
The distributed, process-oriented model, MARINE, was used to test several hypotheses of flow dynamics in soils during flash flood events in the Mediterranean area. Results show that the most realistic hypothesis for each catchment is consistent with existing in situ observations and measurements. The study also highlights the potential of distributed modelling and spatial observations in hydrology, especially in dealing with equifinality issues.