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Recent evidence shows a noticeable reduction in the glacier mass in the Himalaya due to increasing temperatures, and therefore the downstream water availability is becoming uncertain. This study analyse the effect of changes in the Gangotri glaciers (i.e. thickness), including Raktavaran and Chaturangi regions, on the melt runoff (2011-2020) by coupling two models: Glacier Bed Topolology (GlabTop2) and Spatial Process in Hydrology (SPHY). This study performs the two-step calibration approach utilizing the observed discharge and Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover data. The R² values for SPHY-modelled runoff (Q) and observed Q at Bhojwasa are found comparable (~0.73 on a daily scale) and the proportions of glacier Q and snow Q in total Q are computed as 22.11% and 66.91%, respectively. In comparison to Chaturangi and Raktavaran, Gangotri glaciers experienced a higher rate of change in thickness, and a reduction of ~9.40% in the mean glacier thickness is calculated during 2011-2020. [ABSTRACT FROM AUTHOR]

Abstract: Earthquake is one of the most destructive natural hazards which pose a real threat to India with nearly 59% of its geographical area vulnerable to seismic disturbance of varying intensities including the capital city of the country. India has experienced several major earthquakes mainly in Himalayan region and is also considered as one of the most earthquake prone regions in the world. Therefore, during past few decades, the Himalayan region has been studied extensively in terms of present ongoing displacements. It can be believed that a better estimate of the current Himalayan convergence rate and possible rupture can improve seismic hazard evaluations. Moreover, an improved convergence rate is also necessary to estimate if any slip deficit is available to drive future earthquakes in this region. In recent years, SAR interferometry has been successfully used for generating large scale surface displacement maps in radar look direction on a dense grid and with a centimeter to millimeter accuracy. In this context, the usefulness of SAR interferometry technique and its variations for estimation of displacements has been studied and presented in this paper. To study the displacement both conventional and multi-temporal Differential SAR interferometry has been used. In order to get the 3-D surface displacement, interferogram from both ascending and descending track can be used. However, due to the unavailability of ascending track data, a well-known mathematical model also has been used. Overall average displacement rates in the present study are found to be relatively lower as compared to the reported convergence rates. From geophysical point of view, the results presented in this paper for a small area are quite promising. Several explanations have also been presented in this paper to support the results. The reported low convergence rate may be due to the occurrence of silent/quite earthquakes, aseismic slip, differential movement of Delhi Hardwar ridge, etc. Therefore, in view of the contemporary seismicity and conspicuous displacements, a study of long-term observations of this surface movement has been recommended in future. [Copyright &y& Elsevier]

The varying extent of debris cover on a glacier's boundary may seriously hinder automated mapping and inventorying of glaciers in various parts of the world. The problem arises because supraglacial debris (i.e. debris on the glacier) and the adjacent periglacial debris (occurring outside the glacier boundary) have a similar spectral response in the solar reflection region, as both are derived from the same source (i.e. the valley rock). This study based on remote sensing data in a test area in the Chenab basin, Himalayas, shows that the thermal infrared bands have potential in resolving such ambiguity, as considerable temperature differences are found to exist between supraglacial debris and periglacial debris. [ABSTRACT FROM AUTHOR]

The article presents a case study on the estimation of debris cover and its temporal variation through optical satellite sensor data at the Samudratapu glacier, Chenab basin, Himalaya. The method of the study used georeferencing or remote-sensing images because of its various applications in the field of glaciology. The study found different land-cover types demonstrated by the spectral reflectance data and the applicability of the remote-sensing data in monitoring glacier surface.

Many parts of the world with young mountain chains, such as the Himalayas, are highly susceptible to landslides. Due to general ruggedness and steep slopes, roads provide the only way of transportation and connectivity in such terrains. Generally, landslide hazards are overlooked during route planning. In this study, in a test area in the Himalayas, various thematic layers, viz. landslide distribution, landslide hazard zonation, landuse/landcover, drainage order and lithology are generated and integrated using Remote Sensing–GIS techniques. The integrated data layer in raster form has been called a ‘thematic cost map’ and provides an estimate of the cost of route development and maintenance. The relative cost assignment is based on experts' knowledge. Route planning is based on neighbourhood analysis to find various movement possibilities from a pixel to its immediate neighbours. A number of patterns such as those analogous to movements in chess games have been considered. Two new neighbourhood patterns, named here Knight31 and Knight32, have been conceived in addition to commonly used Rook, Bishop and Knight patterns. The neighbourhood movement cost for moving from one pixel to a connected neighbour has been calculated for a 7×7 pixel window considering distance, gradient cost and thematic cost. Dijkstra's algorithm has been applied to compute the least‐cost route between source and destination points. A few examples are presented to show the utility of this approach for a landslide‐safe automatic route planning for a highly rugged hilly terrain. [ABSTRACT FROM AUTHOR]

Landslides cause widespread damage in the Himalayas. Landslide Hazard Zonation is important to take quick and safe mitigation measures and make strategic planning for the future. A part of the Bhagirathi Valley in the Garhwal Himalaya was selected for landslide hazard zonation. The study utilized different types of data including Survey of India topographic maps, geological (lithological and structural) maps, IRS-1B and-1D multispectral and PAN satellite sensor data and field observations. The processing of multi-geodatasets was carried out in a raster GIS environment. The various data layers generated and co-registered were: landuse/landcover, buffer map of thrusts, buffer map of photo-lineaments, lithology, buffer map of drainage, slope angle and relative relief. Data integration was carried out using the ordinal scale (qualitative) relative weighting rating technique to give a Landslide Hazard Index (LHI) value. The breaks in the LHI frequency diagram were used to delineate various landslide hazard zones, namely, very low, low, moderate, high and very high. Field data on landslides were employed to evaluate and validate landslide hazard zonation map. It is interpreted that the distribution of landslides is largely governed by a combination of geoenvironmental conditions like proximity (>500 m) to the thrust zone, presence of Munsiari Formation (Higher Himalayan Crystalline) and barren or less-vegetated areas. [ABSTRACT FROM AUTHOR]

This article presents results on surface ice velocity of the Chhota-Shigri glacier, Himachal Himalaya, deduced by applying sub-pixel image correlation technique (COSI-Corr software) on the ASTER time series data (2003-2009). The remote sensing-derived measurements are found to match quite well with the field measurements. In general, the surface ice velocity varies from ~20 m/yr to ~40 m/yr. Velocity variations occur in different parts of the glacier and also from year to year. In all the years considered for this glacier, the mid-ablation zone and the accumulation zone exhibit higher velocities and zones near the snout and equilibrium line altitude have relatively lower velocities. Further, the velocities are found to be relatively higher in the years 2005-2006 and 2007-2008 and lower in the years 2006-2007 and 2008-2009. These spatial and temporal variations in velocity, which could be related to the glacier morphology and hydro-metrological factors, need to be further studied. [ABSTRACT FROM AUTHOR]