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|Title||TSX InSAR data for creeping landforms detection and monitoring in Alpine periglacial environment at different resolution scales (Western Swiss Alps, Switzerland)|
|Investigator||Barboux, Chloé - University of Fribourg, Department of Geosciences, Geography|
The project aims at the monitoring of rock glacier and landslide activity (local scale) as well as at both updating and upgrading the creeping landform inventory in Central and Bas-Valais areas in the Swiss Alps (regional scale) using TERRASAR-X stripmap mode interferometric data (single polarization, 3m resolution, 30 km swath width, 11 day acquisition time interval). It concentrates on areas situated above the tree line, which is mainly located in the Alpine periglacial belt. The existing inventory was essentially based on a large set of C- and L-band InSAR data mainly dating back to the 1990s and needs to be renewed (1,2).
Specific objectives of the proposed activity include:
The previous studies have shown that a large set of SAR scenes covering several years and various time spans was necessary to establish inventories of slope motion in a confident way. It is thus expected that the use of a large set of TSX data from 2008 to 2013 (including data from the LAN411 project covering our specific area of interest) will surely increase the relevance of these existing inventories by allowing a more accurate detection of moving landforms and a better quantification of their displacement rate in many case. The expected impact of the project is also to show TSX potential to use it as an independent tool for natural hazards survey.
The innovative character of this project was to investigate automated techniques to detect, map and monitor creep rates of moving landforms in Alpine periglacial environment at both the local and regional scales.
Through the whole project, the following main results can be observed according to the three main selected topics.
* The automated mapping of DInSAR signal is possible by using image processing and statistical classifier applied on the interferometric phase image. The related map of slope movements can be compiled using a set of DInSAR data with the same time interval and provides a general overview of the stability of the terrain during this specific time interval (2-4).
* The visual update and upgrade of existing DInSAR polygons over our region of interest, passing through the past ERS technology to the current TSX technology, seems to be the more accurate solution due to a problem of sensor compatibility. Actually, the margins of detected moving zones and the correspondence between DInSAR signal patterns and deformation rates differ according to SAR sensor involving difficulties for an automated approach (2,3).
* The maps of slope movements derived from DInSAR signal analysis can be used as useful tool for helping the visual interpretation, for reducing the subjectivity of expert and for assisting in the development of accurate inventory especially when using a large set of DInSAR data (2-4).
Finally, this project has shown that TSX DInSAR technique is really suitable to detect and map Alpine moving landforms in a mountainous region and especially in the Western Swiss Alps. DInSAR is a good alternative and a powerful technique to give a general overview about the distribution of moving objects in an entire studied region, especially in mountainous area often difficult to access. This kind of analysis, automatic or not, provides a meticulous starting point allowing the detection and selection of landforms that have to be monitored more precisely. This work has also demonstrated that common techniques, like DGPS or TLS, used in the Alpine environment to analyze landforms kinematics are probably more suitable than DInSAR technique when observing rapid Alpine moving landforms (≥ 2m/year) and have to be used jointly to precisely understand the processes governing them.1 - Barboux, C., Delaloye, R., Strozzi, T., Collet, C., Raetzo, H. (2011). TSX InSAR Assessment for slope instabilities monitoring in alpine periglacial environment (western Swiss Alps). Proceedings of FRINGE 2011 Workshop, 19–23 September 2011, Frascati, Italy (ESA SP-697, January 2012).
2 - Barboux, C. (2015). Detection, mapping and monitoring of slope movements in the Alpine environment using DInSAR. PhD thesis. Departement of Geosciences, Geography, University of Fribourg. (submitted)
3 - Barboux, C., Delaloye, R., Strozzi, T., Lambiel, C., Raetzo, H. and Collet, C. (2013). Semi-automated detection of terrain stability in the Swiss Alpine periglacial environment using segmentation and classification of DInSAR scenes: a useful tool to update past inventories of moving areas. Living Planet Symposium. 09-13 september 2013 Edimburg, Scotland.
4 - Barboux, C., Delaloye, R., Strozzi, T., Lambiel, C. and Collet, C. (2013). TSX DInSAR data for detecting and monitoring slope motion phenomena in an Alpine periglacial environment at different resolution scales (Western Swiss Alps, Switzerland) - LAN 1145. TerraSAR-X / TanDEM-X science team meeting, 10-14 June 2013, DLR Oberpfaffenhofen, Germany.
5 - Barboux, C., Delaloye, Lambiel, C. (2014). Inventorying slope movements in Alpine environment using DInSAR. Earth Surface Processes and Landforms. DOI: 10.1002/esp.3603 (In press).
6 - Barboux C., Delaloye R., Lambiel C., Strozzi T., Collet C. & RaetzoH. (2013). Surveying the activity of permafrost landforms in the Valais Alps with InSAR. Mattertal- ein Tal in Bewegung. Publikation zur Jahrestagung der Schweizerischen Geomorphologischen Gesellschaft 29. Juni - 1 Juli 2011, St Niklaus.
7 - Delaloye R., Lambiel C. & Lugon R. (2005). ESA SLAM project, phase 2, Bas-Valais. Validation of InSAR data in permafrost zone. Unpublished.
8 - Delaloye R., Perruchoud E., LambielC., Lugon R. (2008), InSAR Haut-Valais: Inventaire des mouvements de terrain par analyse de signaux d.interférométrie radar satellitaire (période 1993-2000), Rapport final, Mandant: Canton du Valais.
9 - Barboux, C., Delaloye, R., Strozzi, T., Lambiel, C., Collet, C., Raetzo, H. (2012). Monitoring active rock glaciers in the western Swiss Alps: challenges of Differential SAR Interferometry and solutions to estimate annual and seasonal displacement rates. IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 22-27 July 2012, Munich, Germany.
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