Abstract
This work aims at assessing the flooding hazard. More precisely, the study focuses on the influence of groundwater on the genesis and propagation of surface flows in the case of a highly karstified watershed. The experimental site of the Coulazou River, a temporary River which crosses the karstified formation of the Causse d'Aumelas (western Montpellier) has been selected to study hydrodynamic interactions between surface flows and groundwater flows during flood.<br />The hydrodynamic study of this karst/River system is based on a suitable experimental monitoring of both fast and intense hydrological (rain, runoff) and hydrogeological (water level in wells and karst drains, discharge measurements at the main outlets of the system) phenomenon. The specific hydrological response of this watershed is due to the Mediterranean climate but also to surface and underground drainage structures which allow very fast water flows within the karst/river system.<br />A common hydrodynamic description is followed by a functional approach of karst/river exchanges in order (i) to better understand the hydrodynamic behaviour of such a system and (ii) to highlight some indicators that can be used in a modelling approach. A first conceptual model of surface water/groundwater exchanges in karst terranes is presented in the latter part of the manuscript.