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Summary of Proposal HYD1963

Investigator Wiesmann, Andreas - GAMMA Remote Sensing AG, N/A
Team Member
Dr. Strozzi, Tazio - GAMMA Remote Sensing AG, Hazard
Prof. Kääb, Andreas - University of Oslo, Department of Geosciences
Dr. Huggel, Christian - University of Zurich, Geography
Mrs. Matzler, Eva - ASIAQ, Geodata
SummaryThis proposal is in support of the ESA GLOF-DM project addressing GLOF related hazard assessment and monitoring. Glacial hazards are of serious concern and have repeatedly been the cause of major fatal events with up to thousands of people killed in single events (Kääb et al., 2005). Among glacier hazards, glacier lake outburst floods (GLOF) are especially devastating and represent the glacial threat with the farthest potential reach, up to hundred kilometers and more downstream of the glacier lake that burst out. Typically, glacier lake outbursts are a part of complex chain reactions and process interactions, for instance when sudden slope failures above a lake cause impact waves that trigger destabilization of a lake dam that would otherwise remained stable. Due to rapidly changing hazard and risk conditions related to slope instabilities and glacier lakes, historic empirical evidence alone is not anymore sufficient alone for hazard assessment. There is thus an urgent need for improved systematic monitoring. Since most of these glacier lakes are located in remote high-mountain areas, often with difficult access conditions, remote sensing should represent a primary tool for monitoring. While for some potentially hazardous glacier lakes in-situ observation and warning systems have been setup, a majority of the potential sites are not monitored on a regular base be it due to limited finances or inaccessible or hostile environment. Glacier lakes often develop slowly and well visible so that remote sensing methods have actually the potential to be the backbone of regional-scale monitoring schemes. With the ESA INNOVATOR GLOF project it was for the first time shown that and how radar imagery can be used for glacier lake mapping and monitoring (Strozzi et al. 2012). With regard to mass movements, repeat-pass differential SAR interferometry (InSAR) represents a powerful technique for the mapping and monitoring of land surface deformations from space at fine spatial resolution (Bamler and Hartl 1998, Rosen et al. 2000). Potential and limitations of InSAR for the periodical survey of alpine displacements were investigated e.g. in Delaloye et al. (2006). For the alpine territory, which is characterized by low or even absent vegetation, differential InSAR shows a relatively high coherence during the snow-free season between early summer and mid fall permitting the detection and monitoring of unstable slopes on a regular basis (Strozzi et al., 2010). Restrictions to the spatial coverage arise from decorrelation over forested and snow covered areas and from layover and shadowing caused by the very rugged topography. In addition, the technique is better suited for the monitoring of the displacement of slopes facing away from the SAR look vector. As stressed above, glacier lake outbursts are usually part of chain reactions and process interactions, where some processes are rather involved in triggering of outbursts (e.g. slope failures into the lake) or in a change in disposition (e.g. changes of glacier thickness or ice flux), while other conditions and processes rather are involved in deciding about the volume and reach of the event (e.g. river bed topography and amount of sediments that can be mobilized from the outburst flood). Despite these widely acknowledged dependencies, integrated detection, monitoring and modelling of glacial lakes together with detection, monitoring and modelling of slope instabilities and glacier conditions and behavior that potentially affect the glacial lakes is to our best knowledge not done so far, and would represent a novel, though highly needed approach towards integrated assessment of hazards related to glacial lakes.

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