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La Loire des îles, du Bec d'Allier à Gien : rythmes d'évolution et enjeux de gestion

Abstract : The Loire is one of the main fluvial systems in France. The islands are an integral part of the landscape, particularly the anastomosing fluvial pattern of the Middle Loire, hence the name “Loire islands”. This thesis focuses on the functioning of this unknown river. The islands of the Loire river result from morphological fluvial readjustment as well as customs and practices used by inhabitants of the area. The morphological approach concentrates on the evolution of the river since the 19th century, through different spatial and temporal scales. Under a Geographic Information System (GIS), it was possible to monitor the riverbed since 1850 and to analyze in detail mechanisms and rhythms of the river formation. The islands are not stabilized, therefore they can be regarded as forms of river adjustment caused by environmental perturbations (initiating factors: the discontinuation of navigation; aggravating factors: absence of large flood, incision of the riverbed, decline in agriculture, extraction of sediment). The landscape of the Loire Islands is still in transition and is indicating the trend towards the river channelization, dominated by alluvial forests. The fine scale analysis is based on studies on seasonal and inter-annual evolution of islands, as well as secondary channels. Digital Elevation Models (DEM), longitudinal profiles and topographic cross-sections integrated GIS help to quantify precisely erosion and sedimentation, according to the hydrological year. The islands are sites of sediment trapping and they emphasize the sediment deficit recorded since the middle of the 20th century. The situation of secondary channels is contrasted, but the excessive growth of vegetation in some channels triggers their perennial functioning. The results of the thesis brings tools to the Loire river management.
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Contributor : Stéphane Grivel Connect in order to contact the contributor
Submitted on : Thursday, February 11, 2010 - 2:50:38 PM
Last modification on : Tuesday, October 19, 2021 - 4:06:45 PM
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  • HAL Id : tel-00455981, version 1


Stéphane Grivel. La Loire des îles, du Bec d'Allier à Gien : rythmes d'évolution et enjeux de gestion. Géographie. Université Paris VIII Vincennes-Saint Denis, 2008. Français. ⟨tel-00455981⟩



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