Evolution naturelle d'un remplissage sédimentaire intramontagnard et impacts des aménagements contemporains : L'exemple de la vallée de l'Arve (74)

Natural evolution of an intramontane alluvial infill and impacts of contemporary development: The example of the Arve valley

Département de Géographie, Université Lyon 3, 74 rue Pasteur, 69365 Lyon

Abstract

The present valley floors of rivers in mountainous regions represent a particular phase of postglacial and holocene dynamics. Over an extended period i.e. at a geological or historical timescale, alluvial masses have experienced changes in their facies and volume, which are linked to change in the character of mountain erosion and fluvial dynamics. At a contemporaneous timescale, floodplains have probably experienced a shortage of sediment inputs: the resulting degradation of the river bed was canalized by nineteenth century enbankments and gravel extraction. These rapid changes have affected the long profiles and reduced the transport of bedload; conversely, the movement of suspended matter appears to have been less affected.