Bhutan is a relatively small Himalayan country, landlocked between India and Tibet (between 88° and 92° east and 26° and 28° north) and characterised by a very rugged terrain and high topographic gradients, with elevations ranging from around 100 to 7500 m a.s.l.. The steep terrain, as well as geological and geomorphological settings, make this country highly susceptible to landslides phenomena of different size and typology. Given the low population density, secondary hazards related to landslides, such as landslide damming and floods, are particularly important for hazard assessment considerations, since their effects can propagate several kilometres downstream. We here present the results obtained to date in the framework of a large research effort aimed at generating a broad picture of slope instabilities in north-western Bhutan. In this context, we exploit Synthetic Aperture Radar Differential Interferometry (DInSAR) techniques for the identification of formerly unknown landslides in north-western Bhutan and to assess their activity. We focus on the potential and limitations of DInSAR techniques for landslide identification on a regional scale across a high mountain terrain with little initial information. We generated displacement velocity maps and time series through the Small Baseline Subset (SBAS) processing approach of available ENVISAT ASAR and ALOS PALSAR acquisitions for the area of interest. These acquisitions cover respectively the periods between 2003 and 2010 and between 2006 and 2011, and thus provide valuable information for a back analysis of ground movements in the region. Furthermore, we combine the results obtained from the DInSAR analyses with a preliminary inventory of landslides and field observations. The initial inventory was generated through the analysis of optical images and a high resolution Digital Surface Model (ALOS World DEM, 5m GSD). The inventory was initially composed of around 900 polygons, including rock slides, rock avalanches deposits and deep seated gravitational slope deformations. A field campaign carried out in October 2016 allowed to refine this preliminary catalogue of slope instabilities, by jointly interpreting data collected in the field with respect to the results obtained with the DInSAR processing. This work stems from an evident lack of information and knowledge regarding landslides distribution in north-western Bhutan and from the absence of a landslide hazard assessment. This dearth of information on such hazardous phenomena is related to the intrinsic inaccessibility of the terrain, to the current lack of ground based data and, in part, also to existing travel restrictions.
Dini, B., Manconi, A., Loew, S. (2017). DinSAR Investigations Of Landslides In North-western Bhutan. In Fringe ESA 2017.
DinSAR Investigations Of Landslides In North-western Bhutan
Dini, B;
2017
Abstract
Bhutan is a relatively small Himalayan country, landlocked between India and Tibet (between 88° and 92° east and 26° and 28° north) and characterised by a very rugged terrain and high topographic gradients, with elevations ranging from around 100 to 7500 m a.s.l.. The steep terrain, as well as geological and geomorphological settings, make this country highly susceptible to landslides phenomena of different size and typology. Given the low population density, secondary hazards related to landslides, such as landslide damming and floods, are particularly important for hazard assessment considerations, since their effects can propagate several kilometres downstream. We here present the results obtained to date in the framework of a large research effort aimed at generating a broad picture of slope instabilities in north-western Bhutan. In this context, we exploit Synthetic Aperture Radar Differential Interferometry (DInSAR) techniques for the identification of formerly unknown landslides in north-western Bhutan and to assess their activity. We focus on the potential and limitations of DInSAR techniques for landslide identification on a regional scale across a high mountain terrain with little initial information. We generated displacement velocity maps and time series through the Small Baseline Subset (SBAS) processing approach of available ENVISAT ASAR and ALOS PALSAR acquisitions for the area of interest. These acquisitions cover respectively the periods between 2003 and 2010 and between 2006 and 2011, and thus provide valuable information for a back analysis of ground movements in the region. Furthermore, we combine the results obtained from the DInSAR analyses with a preliminary inventory of landslides and field observations. The initial inventory was generated through the analysis of optical images and a high resolution Digital Surface Model (ALOS World DEM, 5m GSD). The inventory was initially composed of around 900 polygons, including rock slides, rock avalanches deposits and deep seated gravitational slope deformations. A field campaign carried out in October 2016 allowed to refine this preliminary catalogue of slope instabilities, by jointly interpreting data collected in the field with respect to the results obtained with the DInSAR processing. This work stems from an evident lack of information and knowledge regarding landslides distribution in north-western Bhutan and from the absence of a landslide hazard assessment. This dearth of information on such hazardous phenomena is related to the intrinsic inaccessibility of the terrain, to the current lack of ground based data and, in part, also to existing travel restrictions.
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