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Auteurs :
Lissak, Candide

Description :

International audience

In mountainous areas, especially in large river catchments with torrential tributaries, the production and sedimenttransport significantly increase flood impacts in the valley bottoms. For a better understanding of Alpine rivercatchments considered as complex systems, we focused our research on the Guil River catchment (Queyras,Southern French Alps - 317km2). This catchment is prone to catastrophic summer floods (June 1957 (> R.I. 100yr), June 2000 (R.I. 30 yr)...) characterized by considerable sediment transport from tributaries to downvalley,very much facilitated by strong hillslope-channel connectivity (12,000 m3 volume of sediment aggraded duringthe June 2000 flood event). During the last flood events, several infrastructures and buildings were seriouslydamaged. Most of them were located at confluences and, at specific reaches such as canyon reaches constrainedby infrastructures. For risk mitigation some protection equipments were built after the 1957 event, but most ofthem are now poorly maintained and might be less effective in case of flood event.In the frame of SAMCO (ANR 12 SENV-0004) project designed for mountain hazard mitigation in a context ofClimate Change, one objective is to understand the hydro-geomorphological functioning of Alpine catchmentsfor a sustainable management of sediment yield, transfer and deposition. Part of our study is aimed at a betterassessment of sediment transfers, especially on adjacent sediment supply (i.e. from hillslope to channel, and fromtributaries to the trunk river) for a better management of sediment fluxes in the frame of the local “River Scheme".For this reason, we decided to establish a sediment budget of the Guil River catchment, with a quantitativeassessment and a spatial analysis of erosion, transport, and deposition processes. The initial phase of our studyconsists in identifying contributive, erosion and deposition areas with a twofold approach: (i) assessment oflongitudinal sedimentary transfers in the floodplain, (ii) assessment of slopes contribution to sediment supply witha main focus on lower slopes where lateral cutting and landslides provide huge quantities of material to the valleybottom. The semi-automatic methodology proposed here is based on data directly derived from remote sensing,GIS analysis (e.g. interpretation of aerial photographs, measurement from regional scale Digital Elevation Model(DEM), high-resolution DEM derived from airborne-based LiDAR) and field surveys.This study highlights spatial differences in sediment storage and redistribution areas grounded on quantitativeand qualitative environmental parameters and index defined for 250 homogeneous sections (i.e. definition ofmorphological index, geometric measurement, rates and type of vegetation cover, hydraulic infrastructureslocation, urban development rates. . . ). It also provides a useful classification of six distinct reach types andareas that will be susceptible to erosion, transport and deposition during the next flooding event (i.e. sedimentproduction areas, temporary and permanent sediment storage areas, areas sensitive to erosion...).

Mots-clés :
budget sédimentaire - bassin-versant - montagne - tributaire - Queyras - Alpes - France - [SDU] Sciences of the Universe [physics] - [SDU.STU] Sciences of the Universe [physics]/Earth Sciences - [SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology - [SDU.STU.HY] Sciences of the Universe [physics]/Earth Sciences/Hydrology

Editeur :

Langue :

Type de document :
info:eu-repo/semantics/conferenceObject, Conference papers

Source :
European Geosciences Union General Assembly 2015;; European Geosciences Union General Assembly 2015, Apr 2015, Vienne, Austria

Date :

Contributeurs :
Littoral, Environnement, Télédétection, Géomatique (LETG - Géophen) ; Université d'Angers (UA) - Université de Nantes (UN) - Université de Caen Basse-Normandie - Université de Bretagne Occidentale (UBO) - Université Rennes 2 - Centre National de la Recherche Scientifique (CNRS)
Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG) ; Institut de Recherche pour le Développement (IRD) - Université Paris-Sorbonne (UP4) - École pratique des hautes études (EPHE) - Université Paris Diderot - Paris 7 (UP7) - AgroParisTech (AgroParisTech) - Centre National de la Recherche Scientifique (CNRS) - Université Panthéon-Sorbonne (UP1)

Identifiants :

Couverture :

Vienne, Austria