Présentations Colloques

    Oral Presentation
    Session 8.05: Karst aquifers
    Fleury Perrine
    Karst flash floods characterization and tools for warning system management (KRHU projet)
    Forecasters working on basins with carbonate outcrops have difficulties to anticipate karst systems response to rainfall event. This is related to their duality of functioning. In low water stage, karst can store water+ At the opposite, in times of high water, karst is saturated, its storage capacity is limited, resulting in increasing the part of runoff and quick underground transfers that can amplify flooding downstream of the basins. With the understanding of these phenomena that depend on the filling of the aquifers, tools were developed by brgm to anticipate the response of systems to rainfall event (Fleury et al., 2010+ 2011+ 2015). **Several systems in South of the France have been studied partly during KRHU project (Lez, Nîmes, the Avene and L'esquielle and the Nartuby. Their functioning was obtained from characterization of aquifers saturation. An indicator of the filling of the karst (followed by representative piezometers of the karst aquifer behavior) has been defined. The latter is called KI (Karst Indicator). **First, the potential of karstification of the basins is spatialized. This work allows locating the karst compartments in the basins. Two cases arise then- most of the basin is karstic, either it's a mixed one. Studies differ then. For essentially Karst basins, only the IK is characterized from a classic hydrogeological study. Nartuby system will be presented. For basins mixed, a preliminary study of the karst compartment is performed to characterize the IK and then the groundwater component from the karst downstream of basin study. **Charts presenting the evolutions of piezometric level in karst compartments are being implemented (KI). They allow define before rainfall event karst reducing capabilities. Then, an evaluation of the response of the system is proposed according to IK initial level and upcoming precipitation (total rainfall and intensity). A classification of the response is proposed as the risk associated. Monitoring levels are then proposed (monitoring, enhanced monitoring, and extreme monitoring). Information are presented in a usable real-time chart tool destined for forecasters. **


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