This review paper examines thermal conditions (active layer and permafrost), internal composition (rock and ice components), kinematics and rheology of creeping perennially frozen slopes in cold mountain areas. The aim is to assemble current information about creep in permafrost and rock glaciers from diverse published sources into a single paper that will be useful in studies of the flow and deformation of subsurface ice and their surface manifestations not only on Earth, but also on Mars. Emphasis is placed on quantitative information from drilling, borehole measurements, geophysical soundings, photogrammetry, laboratory experiments, etc. It is evident that quantitative holistic treatment of permafrost creep and rock glaciers requires consideration of: (a) rock weathering, snow avalanches and rockfall, with grain-size sorting on scree slopes; (b) freezing processes and ice formation in scree at sub-zero temperatures containing abundant fine material as well as coarse-grained blocks; (c) coupled thermohydro-mechanical aspects of creep and failure processes in frozen rock debris; (d) kinematics of non-isotropic, heterogeneous and layered, ice-rich permafrost on slopes with long transport paths for coarse surface material from the headwall to the front and, in some cases, subsequent re-incorporation into an advancing rock glacier causing corresponding age inversion at

Permafrost creep and rock glacier dynamics

. Process interactions and chain reactions, the present shift of cryospheric hazard zones due to atmospheric warming, and the potential far reach of glacier disasters make it necessary to apply modern remote sensing techniques for the assessment of glacier and permafrost hazards in high-mountains. Typically, related hazard source areas are situated in remote regions, often difficult to access for physical and/or political reasons. In this contribution we provide an overview of air- and spaceborne remote sensing methods suitable for glacier and permafrost hazard assessment and disaster management. A number of image classification and change detection techniques support high-mountain hazard studies. Digital terrain models (DTMs), derived from optical stereo data, synthetic aperture radar or laserscanning, represent one of the most important data sets for investigating high-mountain processes. Fusion of satellite stereo-derived DTMs with the DTM from the Shuttle Radar Topography Mission (SRTM) is a promising way to combine the advantages of both technologies. Large changes in terrain volume such as from avalanche deposits can indeed be measured even by repeat satellite DTMs. Multitemporal data can be used to derive surface displacements on glaciers, permafrost and landslides. Combining DTMs, results from spectral image classification, and multitemporal data from change detection and displacement measurements significantly improves the detection of hazard potentials. Modelling of hazardous processes based on geographic information systems (GIS) complements the remote sensing analyses towards an integrated assessment of glacier and permafrost hazards in mountains. Major present limitations in the application of remote sensing to glacier and permafrost hazards in mountains are, on the one hand, of technical nature (e.g. combination and fusion of different methods and data; improved understanding of microwave backscatter). On the other hand, better dissemination of remote sensing expertise towards institutions involved in high-mountain hazard assessment and management is needed in order to exploit the large potential of remote sensing in this field.

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Remote sensing of glacier- and permafrost-related hazards in high mountains: an overview

In order to define adequate prevention measures and to manage landslide emergencies, real-time monitoring is required. This paper presents two different applications of the remote sensing technique: the ground-based synthetic aperture radar interferometry, here proposed as a monitoring and early warning support for slope instability. Data acquisitions carried out through a ground-based synthetic aperture radar interferometer, operating in Ku band, installed in front of the observed slopes, are discussed. Two case studies, based on the use of the same apparatus (formerly developed by the Joint Research Center of the European Commission and by Ellegi-LiSALab srl), are reported: the first one concerns the monitoring of a large landslide, named Ruinon (Valfurva, Italy). The second one deals with the monitoring of the NW unstable slope in the Stromboli island aimed to implementing an early warning system. Acquired interferometric data are processed to provide displacements and velocity maps of the monitored area. The monitoring services ongoing on the Ruinon landslide and on Stromboli demonstrate the capability of this technique to operate in different operative settings (i.e., different phenomena and geological framework) and for different aims (monitoring for prevention, early warning, and emergency assessment). This methodology has also been proved by national and regional authorities of civil protection in order to provide a real-time monitoring for emergency management.

Monitoring, prediction, and early warning using ground-based radar interferometry

This paper illustrates the capabilities of L-band satellite SAR interferometry for the investigation of landslide displacements. SAR data acquired by the L-band JERS satellite over the Italian and Swiss Alps have been analyzed together with C-band ERS-1/2 SAR data and in situ information. The use of L-band SAR data with a wavelength larger than the usual C-band, generally considered for ground motion measurements, reduces some of the limitations of differential SAR interferometry, in particular, signal decorrelation induced by vegetation cover and rapid displacements. The sites of the Alta Val Badia region in South Tyrol (Italy), Ruinon in Lombardia (Italy), Saas Grund in Valais (Switzerland) and Campo Vallemaggia in Ticino (Switzerland), representing a comprehensive set of different mass wasting phenomena in various environments, are considered. The landslides in the Alta Val Badia region are good examples for presenting the improved performance of L-band in comparison to C-band for vegetated areas, in particular concerning open forest. The landslides of Ruinon, Saas Grund, and Campo Vallemaggia demonstrate the strength of L-band in observing moderately fast displacements in comparison to C-band. This work, performed with historical SAR data from a satellite which operated until 1998, demonstrates the capabilities of future planned L-band SAR missions, like ALOS and TerraSAR-L, for landslide studies.

Survey and monitoring of landslide displacements by means of L-band satellite SAR interferometry

The application of ground-based radar interferometry for landslide monitoring is analyzed: a case study based on an experimental campaign carried out in Italy during 2002 is discussed. Interferometric data obtained from coherent synthetic aperture radar (SAR) images acquired by means of C-band ground-based equipment are analyzed. The campaign was aimed at retrieving potential terrain movements of a small landslide observed hundreds of meters away. Critical aspects related to spatial and temporal decorrelation are discussed: the use of optical photogrammetry as a technique for evaluating mechanical stability and correcting geometric distortion is presented. Results also confirmed that the application of ground-based radar interferometry can be attractive and effective if the acquired SAR images maintain an adequate coherence on different dates.

Ground-based radar interferometry for landslides monitoring: atmospheric and instrumental decorrelation sources on experimental data

The detection and quantification of surface deformation of an active rock glacier using the differential synthetic aperture radar (SAR) interferometry (D-InSAR) technique is presented. An average deformation rate of -6 mm/35 days in the radar line of ight was estimated for the summer of 1992. The maximum deformation rate, -18 mm/35 days, was identified at the upper part of the rock glacier, whereas the deformation rate at the snout of the rock glacier was about -10 mm/35 days. The spatial distribution of the surface deformation in the D-InSAR displacement map is smooth and supports the idea that ice is the stress-transferring medium in rock glaciers.

Estimation of rock glacier surface deformation using SAR interferometry data

The detection of an active rock glacier and the quantification of the observed surface movement as well as its temporal change using the D-InSAR method are presented. An average deformation rate of -7.7 mm/35 days in the radar line-of-sight, in the summer of 1992, was estimated. Whereas, the corresponding geodetic measurement, vertical component of 3D flow velocity, was about -8.0 mm/35 days. Additionally, the spatial distribution of the rock glacier surface deformation derived from the D-InSAR data matches the photogrammetric and geodetic generated results to a very high degree.

Estimation of alpine permafrost surface deformation using InSAR data

This paper discusses the detection and satellite-based measurement of the surface displacement (surface deformation) of the largest Austrian glacier, the Pasterze (47°05’N, 12°44’E, 17.5 km2) by means of differential SAR-Interferometry (DINSAR). For this Band 42/1 (2008), S. 85–104 Z E I T S C H R I F T F Ü R GLETSCHERKUNDE U N D G L A Z I A L G E O L O G I E © 2009 by Universitätsverlag Wagner, Innsbruck

Gletscherbewegungsmessungen mittels satellitengestützter Radar-Interferometrie: Die Pasterze (Glocknergruppe, Hohe Tauern, Kärnten).

This investigation is based on the EU project ASSIST (Alpine Safety, Security & Informational Services and Technologies). It is focused on the identification of parameters and/or indicators for natural hazards with special emphasis on landslides analysis. In order to derive the related parameters with adequate accuracy, automated classification and visual interpretation of QUICKBIRD data are used complementarily. For this purpose a comprehensive work has been performed to segregate land cover classes from QUICKBIRD data, to derive geo-morphometric information, and to create a landslide inventory from 'pseudo-stereo' QUICKBIRD interpretation. For estimating the landslide probability on a catchment- and on a single pixel basis the weights-of-evidence method was employed. Such susceptibility maps can subsequently be integrated into the multi platform geo-service framework, which is also developed within the ASSIST project. This framework is used to improve the risk management capacities in mountainous regions by realizing an integrated pre-operational service. The demonstrator includes the client applications for building up an overall crisis management system, e.g. the use of mobile units, a mobile command centre, web-based presentations and open interfaces for other systems.

Generation and webgis representation of landslide susceptibility maps using VHR satellite data

Atmospheric error impacts on interferometric DEM generation were assessed It was found that atmospheric effects are manifested in the InSAR data as deviations from the local topography of the terrain Local height errors of 50 m corresponding to a phase shift of about 247/spl deg/ in an InSAR image pair with a baseline of 160 m was found, while the RMS error of the InSAR generated DEM was about 11 m Error analysis indicated that atmospheric induced errors in InSAR DEMs are significantly reduced in larger baselines data

http://ieeexplore.ieee.org/iel3/3772/11016/00516338.pdf

L.W. Kenyi

Papers

Estimation of rock glacier surface deformation using SAR interferometry data

Estimation of alpine permafrost surface deformation using InSAR data

Gletscherbewegungsmessungen mittels satellitengestützter Radar-Interferometrie: Die Pasterze (Glocknergruppe, Hohe Tauern, Kärnten).

Generation and webgis representation of landslide susceptibility maps using VHR satellite data

Atmospheric induced errors in interferometric DEM generation