Vern Singhroy

Landslide characterisation in Canada using interferometric SAR and combined SAR and TM images

Abstract In Canada and the United States the direct and indirect cost of the damages caused by landslides is about US 2.2 billion dollars a year. These slides are mainly the result of excessive precipitation or ground shaking from earthquakes. Developing new remote sensing techniques to identify and characterise landslides will assist in the current national landslide inventory and hazard mapping programs. This paper reports on the use of interferometric SAR, RADARSAT, and airborne SAR combined with Landsat, TM images to identify diagnostic features of landslides and their slope characteristics. The landslide types in Canada are found in different physiographic regions and are associated with certain kinds of soil and rock materials, geologic structures and topographic settings. Interferometric SAR images provided information on detail slope profiles of the large rock slides occurring on steep slopes and along faults in the Canadian Cordillera. From this image, faults, rock slumps, block slides, slide scars and debris slopes were identified. RADARSAT images with incidence angles varying from 40–59 degrees, particularly the fine mode images, are the most useful to identify landslide features, in mountainous areas. An interpretation of retrogressive slope failures on the shale banks of the Saskatchewan river was conducted using a combined Landsat TM and SAR images. Flow slides on sensitive marine clays were identified on airborne SAR images in the Ottawa valley. These examples show that several remote sensing techniques can assist in producing landslide inventory and risk assessment maps by providing the information on the morphological features of landslides.

Sar integrated techniques for geohazard assessment

Abstract Integrated remote sensing techniques are used increasingly in geohazard assessment. As SAR (synthetic aperture radar) images become commonly available, it is essential that these data be evaluated in terms of the information they can provide for characterizing areas affected by geological hazards. This paper summarizes the utility of remote sensing in geohazard assessment, and presents two case studies in which SAR and TM (thematic mapper) were used to characterize areas affected by landslides and coastal hazards. Based on the results of these two case studies, a guideline is proposed for the utility of remote sensors for geohazard assessment. In the first case study integrated SAR/TM techniques were used to identify and classify landslides in the lower Fraser Valley within the Canadian Rockies. The lower Fraser Valley is one of the most strategically important transportation corridors in Canada. Almost all the lifelines that link the resource rich prairie provinces with metropolitan Vancouver utilize this corridor. Landslides within this valley threaten to disrupt these major transport links. Image maps resulting from the integration of geometrically corrected SAR and TM data provided information on the geomorphology of slopes, land cover and the location and distribution of fracture zones. Such characterization enables the identification and classification of landslides and will complement current airphoto methods used for landslide inventories in high relief areas. In the second case study, enhanced SAR and TM integrated techniques using IHS transform were used to locate areas of erosion and deposition and to update current coastal geomorphological and land cover maps. Coastal Guyana is below sea level, hence sea defence (dykes and sea dams) are used to protect coastal settlements, infrastructure and rich agricultural lands. Erosion of the sea dams has led to severe damage of agricultural lands due to flooding by seawater. The resultant image maps using SAR/TM integrated techniques assist in monitoring the constantly changing shoreline, enable the assessment of flood damage, facilitate in planning areas for coastal dyke repair and maintenance and provide new information for the revision of ongoing coastal geomorphological mapping.

Interpretation of SAR Images for Coastal Zone Mapping in Guyana

La presente etude demontre que certaines parties du littoral de la Guyane se sont modifiees sur des distances de quelques metres a des kilometres au cours de vingt dernieres annees. Cela entraine d...

Geological case studies related to RADARSAT-2

RADARSAT-2 has several capabilities that will be useful to geologists. Some of these capabilities include the availability of high-resolution 3 m synthetic aperture radar (SAR) images, multipolarization and fully polarimetric image modes, and left- and right-looking images. These capabilities are currently being evaluated. Our early results from several ongoing case studies have shown that RADARSAT-2 images will improve current structural and terrain image mapping techniques; provide high-resolution mineral exploration property maps from image fusion techniques; improve interferometric SAR (InSAR) deformation monitoring, particularly small active landslides; and possibly improve the classification of surficial sediments.

Satellite Remote Sensing Applications for Landslide Detection and Monitoring

This paper provides a brief overview of the application potential of EO images related to landslides mapping and monitoring. Our challenge is to recognize and interpret the detailed geomorphic characteristics of large and small landslides, and determine whether or not failure is likely to occur. It is clear from the examples provided that remote sensing images are increasingly being used because applications are becoming more convincing relative to traditional mapping and monitoring methods.

InSAR monitoring of landslides on permafrost terrain in canada

In this study we used differential InSAR techniques to monitor landslide slide and permafrost activity at a site along the Mackenzie Valley Pipeline Corridor. Our results that motion are about 3 times more on exposed burnt slopes than the adjacent areas. The maximum activity is in September, probability related to gradual accumulated increases in soil temperatures.

Satellite Data Fusion Techniques for Terrain and Surficial Geological Mapping

Increased satellite image data availability, with different spatial, spectral, and radiometric resolutions, present some challenges for image fusion techniques to be used in many application areas. In this study, we demonstrate an improved technique combining RADARSAT (SAR), Digital Elevation Model (DEM) and Landsat (ETM+) images with surficial geology data into two complementary composite image maps within Mackenzie Valley Pipeline Corridor, Canada. The method includes four processing steps. (1) The shaded relief derived from DEM was blended with SAR data to produce 3-D effect for terrain and geological structural interpretation. (2) Image fusion using a pan-sharpened IHS technique produced a higher resolution multi-spectral (MS) image. (3) The higher resolution MS image is blended with the SAR-DEM to produce an image terrain map. (4) Two complementary composites were then produced. The first image map contains of geomorphic features/surficial geology GIS layers, and 3D terrain information derived from the SAR-DEM image. The second image map is a composite of geomorphic features/surficial geology blended with the SAR-DEM-ETM+ image map. Integrated image maps generated in steps 1 and 3 provide standardized image base maps to display surficial geological and terrain information.

Environmental and geological site characterization in vegetated areas: Image enhancement guidelines

Guidelines for environmental and geological site characterization normally include field methods with little attention to remote sensing techniques. This paper provides some useful image enhancement guidelines that will facilitate geological mapping and environmental monitoring of vegetated sites. Image enhancement techniques for environmental and geological site characterization provide information on land use, vegetation stress, fracture systems, rock types, landforms, surficial materials, moisture and drainage. In areas where the rock units are covered by vegetation and soil/drift cover, it is difficult to delineate rock types and surficial materials unless special image enhancement is performed. Selection of specific sensor characteristics and surface conditions can maximize the image enhancement techniques and therefore provide useful geologic information. This paper provides useful image enhancement techniques for (1) locating areas of vegetation stress related to acid mine drainage from high resolution airborne multispectral images; and for (2) mapping surficial materials, landforms, rock types and fractures from SAR-TM color composites, the selective uses of principal component analysis and spatial filtering techniques of TM and SAR images, and the integration of SAR and magnetics.

InSAR Monitoring of Landslides in Canada

In this study we used differential and CTM InSAR techniques to monitor landslide slides at different geological sites in Canada. Our results show that InSAR measurements are providing new information on the deformation behaviour of complex landslide processes.

InSAR Monitoring of Post-Landslide Activity

In this study we used differential InSAR techniques to monitor current post slide activity at several landslides along transportation and energy corridors. The landslide materials vary from rock debris, glacial till to permafrost alluvium. Our results show that motion is triggered by spring melt and heavy rainfall events. In the northern Mackenzie Valley pipeline corridor seasonal landslide activity is related to permafrost melt during warm summer months.