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Summary of Proposal LAN1145

TitleTSX 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
Team Member
Prof. Delaloye, Reynald - University of Fribourg, Department of Geosciences, Geography
Dr. Strozzi, Tazio - Gamma Remote Sensing, N/A
Prof. Collet, Claude - University of Fribourg, Department of Geosciences, Geography
Dr. Lambiel, Christophe - University of Lausanne, Department of Geography
Eng. Barboux, Chloé - University of Fribourg, Department of Geosciences, Geography
Summary

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:

  • Combination of InSAR analysis and GPS field measurements (continuation of existing time series) to monitor active rock glaciers and landslides;
  • Investigation of automated methods to monitor acceleration or reduction of creeping landforms. The objective here is to analyze changes in the seasonal and annual flow and to see if automated processes could be done using InSAR TSX independently of field surveying for mass wasting dynamics monitoring in rough terrain topography. Then, some quantification of the variability in flow could be addressed between different rock glaciers;
  • Update (changes in activity rate) and upgrade (more accurate identification of active landforms and quantification of displacement rate) of the creeping landform inventory and especially active rock glaciers in the region of interest using current TSX data.
  • Investigation of automated methods to detect creeping landforms in periglacial environment.

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.

References :

  1. Delaloye R., Lambiel C. & Lugon R. (2005). ESA SLAM project, phase 2, Bas-Valais. Validation of InSAR data in permafrost zone. Unpublished.
  2. Delaloye R., Perruchoud E., Lambiel C., 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.

Final Report

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.
Firstly, we have investigated to which level DInSAR TSX can be used independently of field surveying as a mapping and monitoring tool of mass wasting dynamics in rough alpine terrain topography. Thus, the suitability of available TSX DInSAR data has been assessed for the observation of Alpine slope movements over the region of interest which can move at rates of several centimeters per day.
Then, the objective was to automatically update existing inventories of slope movements of Western Swiss Alps by integrating the most recent TSX data. The current inventory indicates the outlines of moving zones through detected signals of different magnitude orders (cm/day, dm/month, cm/month, cm/year). It contains signal patterns that are related to different phenomena like glaciers, debris-covered glaciers, push-moraines, active rock glaciers, landslides and saggings. In order to obtain new information of active rock glaciers and moving landslides in the studied area, the plan was to use a large set of TSX SAR data (2008-2013).
Finally, the project has investigated the potential of TSX DInSAR for a precise slope motion monitoring at local scale, which means at the scale of a single landform. The objective here was to analyze changes in the seasonal and annual flow of moving landforms and to see if automated processes could be done using DInSAR TSX independently of field surveying for mass wasting dynamics.
To support these targets, a large set of TSX SAR data was used covering our region of interest from the projects LAN411, LAN1145 and LAN2458 together. DGPS measurements from campaigns and permanent GPS stations acquired over more than 20 sites during 2008-2013 have also been used to compare and validate the results.

Through the whole project, the following main results can be observed according to the three main selected topics.

  1. Suitability of TSX DInSAR data for the observation of Alpine slope movements:
    The performance of DInSAR data for the observation of Alpine moving landforms in a defined region of interest should be evaluated before acquiring data thanks to a systematic procedure. Consequently a standard protocol for the suitability assessment of DInSAR technique for the observation of Alpine moving landforms in a delimited area of interest has been proposed (1,2). It was shown that the high temporal sampling and resolution of TSX should have the advantage to deliver better deformation information for displacement rates of some cm/year to 3.5 m/year (or 1 cm/day) (1, 2).

  2. Detection and mapping of Alpine slope movements:
    An automated procedure for the mapping of the slope movements derived from DInSAR data has been developed and has been tested for the update and upgrade of past inventoried DInSAR detected moving zones scenes (2-4). The automated procedure uses segmentation and classification methodologies applied on interferometric coherence and phase images to detect the deformation rate of the surface within large dataset of DInSAR. The model of creating maps of slope movements is simple but robust and the classification of the slope movements is much more reliable by using large number of DInSAR pairs.
    The use of these maps was tested in a small studied area using large set of TSX DInSAR scenes from summers 2008 to 2012 in order to automatically update past moving slope inventories (2-4). The method to automatically detect change in deformation rate of DInSAR polygons works reliably. False change detection is mainly due to external factors as vegetation, snow or atmosphere (where the signal is noisy), due to border effect in layover and shadow areas, as well as due to a change of the outline of the moving zone of the landform.

    The main conclusions about the use of TSX DInSAR data for the detection and mapping of Alpine slope movements can be summarized as follow:
    * The use of TSX DInSAR data seems to be one of the current best methods for a large-scale detection of slope instabilities. Using large set of TSX DInSAR data with various time intervals, this technique provides a regional overview of surface displacements at mm to cm resolution over Alpine areas (with sparse vegetation and during the snow-free period). A large set of TSX SAR scenes covering several years and various time intervals is necessary to establish inventories of slope motion in a confident way (5-8). It allows a more accurate detection of moving landforms and a better quantification of their displacement rate in many cases (2,4).
    * The DInSAR signal pattern gives information about a detected area moving homogeneously which is dependent of the sensor characteristics. The margin of the moving zone depends mainly on the sensor spatial resolution and the deformation rate of the moving zone mainly on the time interval and the wavelength of the sensor (2,5).
  3. * Using a set of DInSAR data from the same sensor, it is possible to detect a change in deformation rate by observing the change of DInSAR signal pattern. However, the evolution in time of the moving zones detected with different SAR sensor has to be performed carefully (2-4).
    * 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).

  4. Monitoring of Alpine slope movements:
    The challenge to monitor annual and seasonal behavior of rapid rock glaciers (1.5-3 m/year) using the new high spatio-temporal resolution of TSX data was investigated in this project (1). Three methods were proposed in order to show the potential of TSX DInSAR for observing Alpine rock glaciers. The first one consists in a study of the interferometric coherence and phase images on a profile defined along the landform (9). The two following ones consider the DInSAR signal observed on the whole studied landform using maps of slope movements previously defined to roughly estimate its annual velocity rate and to detect potential seasonal changes in its behavior (2, 4). TSX DInSAR data has been used for the detection of seasonal and geomorphological processes governing active rock glaciers.

    The main contributions of this project for the use of TSX DInSAR data for the detection and mapping of Alpine slope movements can be summarize as follow:
    * In practice, the new high spatio-temporal resolution of TSX DInSAR data does not allow the quantification of very active rock glacier having a deformation rate larger than 2m/year. Noise generally affects DInSAR signal over (some parts of) these landforms and stops the possibility to estimate precisely the deformation rate (2,9).
    * The new high spatio-temporal resolution of TSX DInSAR data allows the change detection of rock glacier deformation during the summer. The use of a complete set of TSX DInSAR data during summer with a time interval of eleven days allows the qualitative estimation of seasonal variation of the landform deformation rate. The new high spatio-temporal resolution of TSX DInSAR data can be used to detect and point out specific processes governing the Alpine landforms (2,4).
    * To understand and interpret the processes governing the landform with high reliability, DInSAR observations have to be combined with geomorphological expertise (2).

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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