Paper No. 211-10
Presentation Time: 11:15 AM
HIGH RESOLUTION DIGITAL MAPPING AND GEOMORPHOLOGICAL ANALYSIS OF THE MOUNT MEAGER ROCK-DEBRIS AVALANCHE (BC, CANADA)
ROBERTI, Gioachino1, CLAGUE, John2, FRIELE, Pierre A.3, GIARDINO, Marco4, MASERA, Diego1, PEROTTI, Luigi5 and VAN WYK DE VRIES, Benjamin6, (1)Earth Sciences Department, University of Torino, Via Valperga Caluso 35, Torino, 10125, Italy, (2)Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A1S6, Canada, (3)Cordilleran Geoscience, Consultant, Squamish, BC, Squamish, BC V8B 0A5, Canada, (4)Department of Earth Sciences, University of Torino, Via Valperga Caluso, 35, Torino, I-10125, Italy, (5)Department of Earth Sciences, University of Torino, Via Valperga Caluso 35, Torino, 10125, Italy, (6)Laboratoire Magmas et Volcans, University Blaise Pascal, 5 rue Kessler, Clermont-Ferrand, 63038, France
An international (EU-Canada), multidisciplinary (Geomorphology, Engineering Geology, Geomatics) research project has been set up for studying the 6
th August 2010 Mt Meager (BC, Canada) rock-debris avalanche (RDA). Within the present study, new high definition orthophoto and DSM have been produced with the expeditious photogrammetric approach SfM (Structure from Motion) from many redundant overlapping helicopter photos collected with a non-metric camera. The quality of the SfM products have been useful for enhanced interpretation of landforms, deformational structures and deposits of the RDA. Then, a comprehensive reconstruction of the RDA history has been obtained by means of an interpretative subdivision of the landslide accumulation. New insights on formation of structures in RDA deposit and in the fluid phase separation have been proposed.
Dimensions and inaccessibility of parts of the Mt Meager RDA make impossible a classical field approach for studying the whole area. Mesoscopic morpho-structural and detailed sedimentological observations have been partly conducted on the field, while geometry reconstruction and correlations have been described mostly from high resolution orthophoto. RDA facies (block, matrix, mixed, trunks and re-sedimented facies) and geomorphological features (hummocks and structures) have been defined and outlined. For the geomorphological description RDA has been subdivided in 5 major areas (Barrier, Terrace, Plug, Distal Up and Distal Down). Within each area, sub-areas has been identified, where units and sub-units of deposit have been recognized, basing on the associations of geomorphological features and facies. For each area, highly detailed geomorphological maps have been produced.
Analysis, interpretations and correlations of data from the 5 areas allowed a final interpretative legend to be structured. It has been defined by characterizing deposits from their facies association and their deformational structures. The different units within areas and sub-areas have been traced back in five legend symbols. Two end-members deposits have been included in the legend; these allowed to interpret two major “phases” (dense and fluid phases) of the RDA emplacement. They differently affected the areas, leaving a diversity of deposits and traces.
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