Sur quelques modifications hydromorphologiques dans le Val de Seine (Bassin parisien, France) depuis 1830 : quelle part accorder aux facteurs hydrologiques et anthropiques ?

Abstract

The present paper deals with the hydromorphological modifications which occurred along the whole Seine valley (a 779 km long river located in Northern France) during the past two centuries. The aim is to identify these changes and to assess the role of the main controlling factors, which are the hydrological variability (and its influence on fluvial dynamics through morphogenous floods) and the human forcing (river management). The work is based on a comparison between 1830s Ordnance Survey maps and recent satellite images (2009). One qualitative (fluvial pattern) and two quantitative variables (channel width at low flow and number of fluvial islands) were estimated every 1000 m. Results show that the river course remained relatively stable over the studied period, except for the cut-off of some slightly-entrenched meanders in the alluvial plain. In the same time, the low-water channel characterised by a contraction, especially in the estuarine area. Similarly, the number of islands decreased by 50% in the whole Seine valley. The latter change mainly results from human amenities (e.g., canalisation and channelisation works performed for navigation purposes). Floods only contributed to increase the impact of some basic auto cyclic processes (erosion of concave banks, deposition on convex banks).

Keywords

• fluvial hydrogeomorphology
• low-water channel
• Paris Basin
• Seine River
• hydrological variability
• human impact