Promoting ecological management of riparian forests on the Drôme River, France

Abstract

1. Riparian forests, because of their multiple ecological and dynamic functions, have become a subject of particular interest for managers. This is the case in France following the Water Law of 3 January 1992 and the development of the ‘Schema Directeur d'Amenagement et de Gestion des Eaux (SDAGE)’ (Planning and Management—Master Plan—of Water Resources) in various sub-catchments of the Rhone. Within this framework, the major themes of ecologically integrated riparian forest management have been developed on a 110 km section of the Drome river, a piedmont tributary of the middle Rhone river, in south-eastern France. 2. The geographical expansion, diversity and evolution of riparian forest within this section of the Drome since 1948 have been studied. The transport of woody debris, which is characteristic of forest hydrosystems, has also been taken into consideration as managers were concerned by its recent increase. 3. The recently developed vegetation corridor, measuring nearly 710 ha, is threatened by reduced bedload availability leading to channel incision and the disconnection of the floodplain from the active band of the channel, as well as reduced vegetation renewal. 4. Several management proposals have been put forward in an effort to maintain riparian ecosystem dynamics without simultaneously increasing flooding and erosion risk: (i) legal measures to conserve the most functional sections, (ii) replanting a vegetation corridor at least 5 m wide in farming areas, (iii) impeding the breaking-up of the most interesting vegetation corridors into small parcels of land, (iv) urgently encouraging the regeneration of vegetation margins and renewed sediment transport, namely by creating artificial overflow channels in forested areas or by clearing certain sectors of the active channel. 5. It has been proposed that vegetation maintenance and logjam removal, today recognized as detrimental from an ecological standpoint, be conducted selectively on the basis of management appraisals of certain sectors. Certain reaches will no longer be subject to maintenance on the grounds of their great ecological value and because of their low risk of flooding impacts. ©1997 John Wiley & Sons, Ltd.