AIGA: an operational tool for flood warning in southern France. Principle and performances on Mediterranean flash floods

Monitoring and flood forecasting on the great French rivers are a legal obligation since 2003. These great rivers, plus the ones monitored by local communities, account for hardly 10% of the national hydrographic network. No measured data are thus available for the very large majority of the French rivers. In order to cope with the needs of flood warning for such basins, the Cemagref and Météo-France have developed an operational tool named AIGA. It is based on a regionalized rainfall-runoff model, and can thus be applied to any watershed of the regionalization area including ungauged catchments. The major interest of the method is indeed to yield flood warnings on such basins. AIGA is designed for small watersheds (a few tens to a few hundreds of km2) affected by flash-floods, where the implementation of a rainfall-runoff model is useful to improve the anticipation delay. The method is currently operational on the French Mediterranean area which is prone to flash-floods.