Abstract
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 and Water 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.
Highlights
Floods are natural phenomena with environmental, social and economic impacts [1,2,3]
We considered eight flash flood events for MARINE calibration, six of which were used for the comparison with Soil and Water Assessment Tool (SWAT) (Table 1)
The RCHRG_DP and the CH_K2 parameters both drive water loss to the groundwater, respectively, along the soil profile and within the stream bed. Their respective best-fitted values of 0.52 (-) and 52 mm h−1 account for the pervious bedrock of the basin, but they reflect the water abstraction for irrigation purposes: diverted water is lost for the channel
Summary
Floods are natural phenomena with environmental, social and economic impacts [1,2,3]. Impacts of floods may be magnified by some human activities, such as increasing settlements and economic assets in floodplains, or the reduction of the soil’s natural water retention under changing land uses. Global change is expected to increase the flooding risk in the decades, with more people settling in floodplains, whereas climate change is likely to increase the frequency of intense rainfall events and consequent floods, especially across the prominent climate response hot-spot Mediterranean basin [10,11,12]. Flash floods are generally triggered by quasi-stationary convective systems, with local and intense rainfall events [13,14]. The term “flash” refers to the rapid response, with water
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