Morphological origin of run-offs through distributed hydrological observations on two Mediterranean catchments in the Cevennes region (Gard, France)

Maréchal, Denis; Ayral, Pierre‐Alain; Bailly, Jean‐Stéphane; Puech, Christian; Sauvagnargues, Sophie

doi:10.4000/geomorphologie.10120

Cited by 11 publications

(15 citation statements)

References 13 publications

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“…The natural resistivity profile suggests a regular soil bedrock interface when the latter consists of schist, while the granite one presents a more chaotic structure. Finally, the continuous comparative study of two experimental sites over surface areas of the order of 1 km 2 -one located on the schist upstream part of the Gard catchment and the other one on the downstream granite part -suggests that there is rapid subsurface flow processing on the schist area, while flow formation appears to be controlled by the extension of the saturated zone related to the river on the granitic site Maréchal et al, 2009Maréchal et al, , 2013.…”

Section: Study Catchment Setmentioning

confidence: 99%

“…1) were those of the Ardèche, Gard, Hérault and Salz rivers. These were selected for the following reasons; (i) they are representative of the physiographic variability found in areas where flash floods occur, (ii) numerous studies of flash floods have already been carried out on the Gard and Ardèche (Ruin et al, 2008;Anquetin et al, 2010;Delrieu et al, 2005;Maréchal et al, 2009;Braud et al, 2014) that could guide the interpretation of the modelling results , and (iii) a considerable number of observations of flash flood events are available for these catchments.…”

Section: Study Catchment Setmentioning

confidence: 99%

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

Douinot

Roux

Garambois

et al. 2018

Hydrol. Earth Syst. Sci.

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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.

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Section: Study Catchment Setmentioning

confidence: 99%

Section: Study Catchment Setmentioning

confidence: 99%

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

Douinot

Roux

Garambois

et al. 2018

Hydrol. Earth Syst. Sci.

View full text Add to dashboard Cite

show abstract

“…ponds, buffer, change in slopes) in producing runoff, storing water or transferring it (Sivapalan, 2003b). Recent work has shown that dense limnimeter networks combined with very-high-resolution lidar DEM provide valuable insight into the connectivity question for headwater catchments (Maréchal, 2011;Maréchal et al, 2012;Sarrazin, 2012). Various types of reaches can be identified.…”

Section: Experimental Set-up On the Small Catchment Scalementioning

confidence: 99%

Multi-scale hydrometeorological observation and modelling for flash flood understanding

Braud¹,

Ayral

Bouvier

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. This paper presents a coupled observation and modelling strategy aiming at improving the understanding of processes triggering flash floods. This strategy is illustrated for the Mediterranean area using two French catchments (Gard and Ardèche) larger than 2000 km 2 . The approach is based on the monitoring of nested spatial scales: (1) the hillslope scale, where processes influencing the runoff generation and its concentration can be tackled; (2) the small to medium catchment scale (1-100 km 2 ), where the impact of the network structure and of the spatial variability of rainfall, landscape and initial soil moisture can be quantified; (3) the larger scale (100-1000 km 2 ), where the river routing and flooding processes become important. These observations are part of the HyMeX (HYdrological cycle in the Mediterranean EXperiment) enhanced observation period (EOP), which will last 4 years (2012)(2013)(2014)(2015). In terms of hydrological modelling, the objective is to set up regional-scale models, while addressing small and generally ungauged catchments, which represent the scale of interest for flood risk assessment. Topdown and bottom-up approaches are combined and the models are used as "hypothesis testing" tools by coupling model development with data analyses in order to incrementally evaluate the validity of model hypotheses. The paper first presents the rationale behind the experimental set-up and the instrumentation itself. Second, we discuss the associated modelling strategy. Results illustrate the potential of the approach in advancing our understanding of flash flood processes on various scales.

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“…The potential hydrologic specificity of schist rocks, despite poorly described in literature, has been suggested by Martin et al (2004) and Maréchal et al (2013), both looking at French Mediterranean catchments. In these two studies, the authors observe that schist catchments behave differently from others.…”

Section: The Different Hydrological Behaviours Induced By Distinct Gementioning

confidence: 90%

Investigating the role of geology in the hydrological response of Mediterranean catchments prone to flash-floods: Regional modelling study and process understanding

Vannier

Anquetin

Braud³

2016

Journal of Hydrology

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s u m m a r yIn this study, a regional distributed hydrological model is used to perform long-term and flash-flood event simulations, over the Cévennes-Vivarais region (south of France). The objective is to improve our understanding on the role played by geology on the hydrological processes of catchments during two past flash-flood events. This modelling work is based on Vannier et al. (''Regional estimation of catchment-scale soil properties by means of streamflow recession analysis for use in distributed hydrological models", Hydrological Processes, 2014), where streamflow recessions are analysed to estimate the thickness and hydraulic conductivity of weathered rock layers, depending on the geological nature of catchments. Weathered rock layers are thus implemented into the hydrological model CVN-p, and the contribution of these layers is assessed during flash-flood events simulations as well as during interevent periods. The model is used without any calibration, to test hypotheses on the active hydrological processes. The results point out two different hydrological behaviours, depending on the geology: on crystalline rocks (granite and gneiss), the addition of a weathered rock layer considerably improves the simulated discharges, during flash-flood events as well as during recession periods, and makes the model able to remarkably reproduce the observed streamflow dynamics. For other geologies (schists especially), the benefits are real, but not sufficient to properly simulate the observed streamflow dynamics. These results probably underline the existence of poorly known processes (flow paths, non-linear spilling process) associated with the planar structure of schisty rocks. On a methodological point of view, this study proposes a simple way to account for the additional storage associated with each geological entity, through the addition of a weathered porous rock layer situated below the traditionallyconsidered upper soil horizons, and shows its applicability and benefits for the simulation of flash flood events at the regional scale.

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Morphological origin of run-offs through distributed hydrological observations on two Mediterranean catchments in the Cevennes region (Gard, France)

Cited by 11 publications

References 13 publications

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

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

Multi-scale hydrometeorological observation and modelling for flash flood understanding

Investigating the role of geology in the hydrological response of Mediterranean catchments prone to flash-floods: Regional modelling study and process understanding

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