摘要
Riverbed geometry in piedmonts and plains is particularly sensitive to any modification of discharge and sediment supply within the watershed. In southeastern France, river incision is a characteristic example which reposes on both natural and man-induced modifications, where excessive exploitation of resources has led to development and management problems. Given the costs and damage caused to the river and riparian environments that have resulted from these situations, managers are now paying particular attention to these problems. In France, this is concurrent with new orientations established by the water law of January 3rd, 1992 and the development of ‘Schémas d'Aménagement et de Gestion des Eaux’ (water development and management programs) for different catchments in the Rhône basin. It is within this context that new management orientations have to be defined on the Drôme river, a 110-km long piedmont tributary of the middle Rhône river. The evolution of the Drôme river long profile was studied for the 20th century, leading to the identification of the causes and consequences of incision. About 75 % of the studied section is affected by this phenomenon, which can attain 4 to 5 m, locally. The potential for sediment stock renewal was assessed by: (i) lateral erosion on the level of the segment, and (ii) supply from tributaries for the entire watershed. Only 25.7 % of the total bank length is currently affected by erosion and only 11 tributaries supply sediment in 1991, compared to 24 in 1948. Several management proposals are presented, aiming to restore the long profile and maintain ecosystem dynamics without increasing risk to river side populations.