The river Hérault is a 160 km long coastal river of the south of France. It brings a lot of water to the region, but it is subject to important floods. It has an abundant flow : it discharges more than 1.3 billion tones of water per year. The irregularity of its flow is quite a problem, especially concerning sudden floods which are linked to the seasonal heavy rain on the Mont Aigoual mountain range: the river Hérault reached a flow of 1.500 m³/s on December 1st 1958 and of 1.320 m³/s on December 19 1997 (= the average flow of the river Rhône in Valence). However, in August, the flow can go down to 7.5 m³/s only. The depth of runoff in the Hérault basin is of 543 millimeter/year, which is higher than the average in France. Thus, here is a coastal river absolutely typical of the Mediterranean banks.