Description:
Abstract : The dynamics of water and matter flows : changes in plant communities in the Isère valley. The paper presents a model of the organisation of alluvial vegetation in the flood plain of the Isère river, between Albertville and Grenoble. Each type of plant community occupies a specific location in a three-dimensional space defined by the following gradients : — longitudinal gradient : from upstream to downstream, with a characteristic change from braiding to meandering ; — transverse gradient : from river islands, inside the dykes, flooded during spring and summer high water, to backswamps, outside the dykes, flooded during winter ; — vertical gradient : from banks of frequently rejuvenated coarse deposits to high terraces which are rarely subject to flooding. The present state of the vegetation is the result of the cumulative effect of man's actions : forest clearance, dyking, warping, drainage works, extraction of gravel, hydropower development schemes. In conclusion, the hydrosystem is undergoing irreversible change and some extreme hy- drological situations are analysed.