Erosion and morphology of a debris flow caused by a glacial lake outburst flood, Western Norway
This article documents a 240,000-m3 debris flow resulting from a glacial lake outburst flood in Fjærland, Western Norway, May 8, 2004. The event started when a glacial lake breached a moraine ridge. The ensuing debris flow was able to erode material along its path, increasing in volume from about 25,000 to 240,000 m3 before depositing about 3 km from its starting point. Field investigations, pre- and post-flow aerial photographs as well as airborne laser scanning (LIDAR) were used to describe and investigate the flow. The most striking and unusual feature of this case study is the very pronounced erosion and bulking. We have made a detailed study of this aspect. Erosion and entrainment is quantified and the final volume of the debris flow is determined. We also present geometrical and sedimentological features of the final deposit. Based on the Fjærland data, we suggest that a self-sustaining mechanism might partly explain the extreme growth of debris flows traversing soft terrain.
KeywordsDebris flow Erosion Entrainment Glacier hazard Fjærland Norway
This work has been funded by VISTA (Norwegian Academy of Science and Letters together with Statoil), and by the Norwegian Research Council through the International Centre for Geohazards (ICG), Project 9: “Slide dynamics and mechanics of disintegration”.
We would like to thank Trond Eiken at the University of Oslo for helpful advice concerning the photogrammetry, all our colleagues at ICG for fruitful cooperation and Miriam Jackson at the Norwegian Water Resources and Energy Directorate (NVE) for valuable discussions concerning glaciology and the water volume involved in the debris flow. We are also grateful to Adrian Read for proofreading. Special thanks to the inhabitants of Supphelledalen in Fjærland for their hospitality and provision of valuable information.
This is ICG-contribution number 186.
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