Action des crues sur la dynamique sédimentaire et végétale dans un lit de rivière à galets : L’Isère en Combe de Savoie.

Abstract : In the recent past, mature vegetation has established on gravel bars of many gravel bed rivers worldwide often partly because of anthropic alterations of water and sediment regimes. This trend is problematic in terms of flood risks and biodiversity. Managing hydrology in a way that would limit vegetation establishment on bars presents an interesting management option. In this context, our study aims at understanding the impacts of floods of varying magnitude on vegetation removal, and identifying and quantifying the underlying mechanisms. Our study site is the Isère River, a heavily managed gravel bed river flowing in the western French Alps. Our methodological approach consists of aerial photo analysis in relation to hydrology at the reach scale (20 km), complemented by field observations and hydraulic modeling at the bar scale. At the reach scale, discharges associated to return intervals of less than a year seem to have an impact on vegetation removal. However removed areas are modest : on average, 3,4% of veetation area is removed annually since 1996. At the bar scale, frequent floods (return interval < 1 an) were not able to remove vegetation. Only a 10 year flood, which triggered important sediment mobility, could partially remove pioneer vegetation from bars. Generally, vegetation removal on the bars of the Isère River is related to the large scale mobility of macroforms.
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https://hal.archives-ouvertes.fr/tel-01616077
Contributor : Camille Jourdain <>
Submitted on : Friday, October 13, 2017 - 10:07:26 AM
Last modification on : Saturday, July 13, 2019 - 9:52:06 PM
Long-term archiving on: Sunday, January 14, 2018 - 12:51:04 PM

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Camille Jourdain. Action des crues sur la dynamique sédimentaire et végétale dans un lit de rivière à galets : L’Isère en Combe de Savoie.. Hydrologie. École Doctorale Terre Univers Environnement, 2017. Français. ⟨tel-01616077v1⟩

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