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Réponses hydrosédimentaires de chenaux latéraux restaurés du Rhône français : Structures spatiales et dynamiques temporelles des patrons et des processus, pérennité et recommandations opérationnelles

Abstract : Over the past two centuries, the hydrological regime and the fluvial dynamics of the Rhône River have been highly modified, leading to a drastic decrease in the structural and functional habitat diversity of the main river channel and floodplains. An ambitious restoration project was initiated at the end of the 1990's. This thesis deals with the monitoring of 18 floodplain channels, which were restored between 1999 and 2006. We combined analysis based on grain size of deposits, fine sediment thicknesses, water depth, topographical and hydrological data and airborne imagery. We used pre-restoration data for 12 floodplain channels coupled with between three and seven post-restoration surveys for each channel, ranging from 5 to 15 years after restoration. To assess the adjustment of hydromorphological conditions, the physical functional diversity and the persistence of floodplain channels as aquatic habitats, we used statistical analysis and a modeling approach that allowed us to forecast conditions. Results demonstrate that both (i) grain size patterns and (ii) fine sediment accumulation rates can be predicted using simple hydrologic and/or hydraulic descriptors (upstream overflow frequency, shear stress, back-flowing capacity), which reflect the control exerted by the geometry of floodplain channels on their flooding regime (upstream overflow frequency, shear stress and backflow capacity). Such empirical statistical relationships can be used a priori to estimate the potential effects of different floodplain channel geometries on the propensity to accumulate fine sediment and the grain sizes of this sediment. Estimates of potential ranges of floodplain channel life spans are provided and discussed according to multiple trend models. This research has direct application and provides tools to river managers that will help guide this type of floodplain channel restoration design in the future on the Rhône River.
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Submitted on : Tuesday, December 22, 2015 - 12:01:17 PM
Last modification on : Monday, August 30, 2021 - 1:24:02 PM
Long-term archiving on: : Saturday, April 29, 2017 - 11:50:28 PM

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  • HAL Id : tel-01247592, version 1

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Jérémie Riquier. Réponses hydrosédimentaires de chenaux latéraux restaurés du Rhône français : Structures spatiales et dynamiques temporelles des patrons et des processus, pérennité et recommandations opérationnelles. Géographie. Université Lumière Lyon 2, 2015. Français. ⟨tel-01247592⟩

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