Abstract
Abstract. The MARINE (Model of Anticipation of Runoff and INundations for Extreme events) hydrological model is a distributed model dedicated to flash flood simulation. Recent developments of the MARINE model are explored in this work. On one hand, transfers of water through the subsurface, formerly relying on water height, now take place in a homogeneous soil column based on the soil saturation degree (SSF model). On the other hand, the soil column is divided into two layers, which represent, respectively, the upper soil layer and the deep weathered rocks (SSF–DWF model). The aim of the present work is to assess the accuracy of these new representations for the simulation of soil moisture during flash flood events. An exploration of the various products available in the literature for soil moisture estimation is performed. The efficiency of the models for soil saturation degree simulation is estimated with respect to several products either at the local scale or spatially distributed: (i) the gridded soil moisture product provided by the operational modeling chain SAFRAN-ISBA-MODCOU; (ii) the gridded soil moisture product provided by the LDAS-Monde assimilation chain, which is based on the ISBA-A-gs land surface model and assimilating satellite derived data; (iii) the upper soil water content hourly measurements taken from the SMOSMANIA observation network; and (iv) the Soil Water Index provided by the Copernicus Global Land Service (CGLS), which is derived from Sentinel-1 C-SAR and ASCAT satellite data. The case study is performed over two French Mediterranean catchments impacted by flash flood events over the 2017–2019 period. The local comparison of the MARINE outputs with the SMOSMANIA measurements, as well as the comparison at the basin scale of the MARINE outputs with the gridded LDAS-Monde and CGLS data, lead to the following conclusion: both the dynamics and the amplitudes of the soil saturation degree simulated with the SSF and SSF–DWF models are better correlated with both the SMOSMANIA measurements and the LDAS-Monde data than the outputs of the base model. Finally, the soil saturation degree simulated by the two-layers model for the deep layer is compared to the soil saturation degree provided by the LDAS-Monde product at corresponding depths. In conclusion, the developments presented for the representation of subsurface flow in the MARINE model enhance the soil saturation degree simulation during flash floods with respect to both gridded data and local soil moisture measurements.
Highlights
The risk associated with flash flood events is of growing importance, in particular in the Mediterranean area (Payrastre et al, 2011; Ruin et al, 2014; Suárez-Almiñana et al, 2020)
Since the water height gradient between two cells depends on the slope between the cells and the cell textures, water height gradients are larger than volumetric soil water gradients when no precipitation happens
Lateral flows based on the water height gradients are larger than lateral flows based on the volumetric soil water gradients
Summary
The risk associated with flash flood events is of growing importance, in particular in the Mediterranean area (Payrastre et al, 2011; Ruin et al, 2014; Suárez-Almiñana et al, 2020). The main variable of interest for flood simulations at the catchment scale is usually. J. Eeckman et al.: An assessment of the soil moisture dynamics in the MARINE flood model the discharge variable, which integrates all the processes taking place at the subsurface and the surface of the catchment. Surface runoff, itself controlled by soil infiltration rates, is shown to exacerbate both human and material risks during extreme events (Vincendon et al, 2010). The representation of soil processes in the models is a key factor for flash flood simulation (Berthet et al, 2009)
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