Journal Article

Debris-flow activity in abandoned channels of the Manival torrent reconstructed with LiDAR and tree-ring data

Climatic Change and Climate Impacts Research Group ; Institute for Environmental Sciences [Geneva] (ISE) ; Université de Genève = University of Geneva (UNIGE)-Université de Genève = University of Geneva (UNIGE), Laboratory of Dendrogeomorphology ; Universität Bern = University of Bern = Université de Berne (UNIBE)-Institute of Geological Sciences, Gotteland, A, Berger, F, Corona, C, Érosion torrentielle, neige et avalanches (UR ETGR (ETNA)) ; Centre national du machinisme agricole, du génie rural, des eaux et forêts (CEMAGREF), Ecosystèmes montagnards (UR EMGR) ; Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Liébault, F, Stoffel, M, Lopez Saez, J

2011

Overview

Hydrogeomorphic processes are a major threat in many parts of the Alps, where they periodically damage infrastructure, disrupt transportation corridors or even cause loss of life. Nonetheless, past torrential activity and the analysis of areas affected during particular events remain often imprecise. It was therefore the purpose of this study to reconstruct spatio-temporal patterns of past debris-flow activity in abandoned channels on the forested cone of the Manival torrent (Massif de la Chartreuse, French Prealps). A Light Detecting and Ranging (LiDAR) generated Digital Elevation Model (DEM) was used to identify five abandoned channels and related depositional forms (lobes, lateral levees) in the proximal alluvial fan of the torrent. A total of 156 Scots pine trees (Pinus sylvestris L.) with clear signs of debris flow events was analyzed and growth disturbances (GD) assessed, such as callus tissue, the onset of compression wood or abrupt growth suppression. In total, 375 GD were identified in the tree-ring samples, pointing to 13 debris-flow events for the period 1931-2008. While debris flows appear to be very common at Manival, they have only rarely propagated outside the main channel over the past 80 years. Furthermore, analysis of the spatial distribution of disturbed trees contributed to the identification of four patterns of debris-flow routing and led to the determination of three preferential breakout locations. Finally, the results of this study demonstrate that the temporal distribution of debris flows did not exhibit significant variations since the beginning of the 20th century.

• Publisher: CCSD,Copernicus Publ. / European Geosciences Union,Copernicus GmbH,Copernicus Publications
• Subject: Alluvial fans / Debris flow / Detritus / Earth Sciences / Environmental Sciences / Evergreen trees / Levees / Lidar / Pine trees / Sciences of the Universe / Spatial analysis / Spatial distribution / Temporal distribution