Le Drac dans l'agglomération de Grenoble : première évaluation des changements géomorphologiques contemporains

Abstract

Abstract : The Drac river in the Grenoble urban area : a first assessment of present-day geomorpholo- gical changes. Since the Second World War, the Drac river has been subject to considerable channel instability in its passage through the alluvial plain of Grenoble. Between 1950 and 1975, channel width decreased markedly and the river lowered its bed by more than 3 metres. A second phase began after 1975, when the channel became more stable and gravel bars became progressively covered by vegetation. Geomorphological changes in the alluival plain of Grenoble have been caused mainly by gravel extraction which between 1955 and 1972 accounted for more than 7 million m3. The effect of such extraction activities has been reinforced by water diversions near hydropower plants and by road construction works encroaching on the river channel. The complex response of fluvial systems to human activities requires that river management practices be continually updated.