1.2- Case study introduction

The HydroEurope project is dedicated to the Var catchment (France) which is seriously affected by extreme flood process. The development of the downstream area of the catchment is a major issue and has to be defined in a holistic way in order to mitigate risks and ensure sustainable development. 

Fig. 1 -The French Riviera, and a Spot image of the lower Var river valley and the airport constructed on the reclaimed delta.La Côte d’Azur, et une image SPOT de la basse vallée du Var et de l’aéroport construit sur le delta.The Var is an Alpine torrential river with steep slopes. Located in the southeast of France, it has a total length of 114 km / 71 mi, with the Tinée, Estéron and Vésubie as its main tributaries. The Var rises near the Col de la Cayolle in the Maritime Alps and flows generally southeast – mainly through the Alpes-Maritimes with a short stretch in the Alpes-de-Haute-Provence – into the Mediterranean between Nice and Saint-Laurent-du-Var.

From the early 19th century on until the 1960s the river was canalized over the entire length of the lower valley, reducing its width from about 1000 m / ⅔ mi (in average between valley slopes) to a mere 300 m, and even 200 m in the last stretch close to the sea. To compensate the lowering of the river bed as a result of the extraction of building materials, sills (fixed weirs) were constructed to bring the water table back to its original level.

Fig. 3 - Ground photographs of a gravel-retention dam damaged by the November 1994 flood (A), and braided gravely channel in the coastal reaches downstream of the dams during low discharge (B). Photographies d’un barrage de rétention de graviers endommagé par la crue de novembre 1994 (A), et du lit anastomosé du Var près de la côte, en aval des barrages, durant une période d’étiage (B).

On November 5, 1994, an extreme flood event caused the lowest and the second-lowest dams on the Var to collapse. The flood wave inundated parts of Nice, including Nice’s international airport which is situated near the river mouth. It was out of service for several days. The airport lost the business of 50,000 passengers, with damages running up to an estimated 4.5 to 6 million euro. Elsewhere roads like the RN202 were cut, power and telephone lines were interrupted, and three people died and four disappeared.

In 1994 a new highway was planned, situated in part on the right bank of the Var. This would result in a further reduction of the river bed in the order of 10%.