Simulating flash floods at hourly time-step using the SWAT model

Laurie Boithias (1, 2, 3) , Sabine Sauvage (1, 3) , Anneli Lenica (4, 3) , Hélène Roux (4, 3) , Karim C. Abbaspour (5) , Kévin Larnier (4, 3) , Denis Dartus (4, 3) , Jose-Miguel Sanchez-Perez (1, 3)

1 LEFE - Laboratoire Ecologie Fonctionnelle et Environnement
2 GET - Géosciences Environnement Toulouse
3 UT - Université de Toulouse
4 IMFT - Institut de mécanique des fluides de Toulouse
5 EAWAG - Swiss Federal Insitute of Aquatic Science and Technology [Dübendorf]

Flash floods are natural phenomena with environmental, social and economic impacts. To date, few numerical models are able to simulate hydrological processes at catchment scale at a reasonable time scale to describe flash events with accurate details. Considering a ~810 km2 Mediterranean river coastal basin (southwestern France) as a study case, the objective of the present study was to assess the ability of the sub-daily module of the lumped Soil andWater Assessment Tool (SWAT) to simulate discharge (1) time-continuously, by testing two sub-basin delineation schemes, two catchment sizes, and two output time-steps; and (2) at flood time-scale, by comparing the performances of SWAT to the performances of the event-based fully distributed MARINE model when simulating flash flood events. We showed that there was no benefit of decreasing the size of the minimum drainage area (e.g., from ~15 km2 down to ~1 km2) when delineating sub-basins in SWAT. We also showed that both the MARINE and SWAT models were equally able to reproduce peak discharge, flood timing and volume, and that they were both limited by rainfall and soil data. Hence, the SWAT model appears to be a reliable modelling tool to predict discharge over long periods of time in large flash-flood-prone basins.

Mots clés: flash storm; flood event; sub-daily simulation; peak discharge; runoff; Mediterranean watershed

Mots clés: MARINE model

Domaines: Sciences du Vivant [q-bio]

Laurie Boithias, Sabine Sauvage, Anneli Lenica, Hélène Roux, Karim C. Abbaspour, et al.. Simulating flash floods at hourly time-step using the SWAT model. Water, 2017, 9 (12), pp.1-25. ⟨10.3390/w9120929⟩. ⟨hal-02620257⟩