Browsing by Author "Prabhat Semwal"

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Soil erosion and flood hazard zonation using morphometric and morphotectonic parameters in Upper Alaknanda river basin
(Springer, 2020) Neeraj Pant; Rajendra Kumar Dubey; Anand Bhatt; Shive Prakash Rai; Prabhat Semwal; Sumit Mishra
In the present study, detailed morphometric, morphotectonic, statistical and hazard analyses have been carried out in the Upper Alaknanda river basin (UAB) located in Central Himalayas, Garhwal, India. The study area is bounded by the South Tibetan Detachment System in the north and by the Main Central Thrust in the south. The major river flowing in the area is Alaknanda which is a major tributary of river Ganga. The purpose of this study is to examine the influence of active tectonics, flood hazard, and soil erosion on the basis of morphotectonic and morphometric parameters using the Cartosat-1 Digital Elevation Model and ArcGIS software. The study area is divided into 10 sub-basins, where 50 morphometric and 6 morphotectonic parameters were calculated. Bifurcation ratio and stream frequency show that streams up to third order is having steep gradient and rolling through highly dichotomized terrain, due to which high overland flow and less groundwater recharge takes places, whereas drainage density clearly indicates the high flood possibility in the region. Morphotectonic parameters indicate relatively young to an early mature geological stage of sub-basins and tectonically active region. The statistical analysis of morphometric parameters is carried out by using correlation analysis, hierarchal cluster analysis, and principal component analysis. Based on their susceptibility to soil erosion, morphometry and landcover classification is carried out to prioritize the sub-basins of UAB. The combined morphometric, morphotectonic and statistical analysis indicates that the area is tectonically active and highly prone to flood, flood induced landslide and soil erosion. The case study of the 2013 flash flood event at three locations Benakuli, JP HEP and Pulna also confirms that the study area is hydro-geologically active to flood and flood induced hazards. The results obtained in this study are directly related to watershed management and hence soil erosion, tectonic activities and flash flood possibilities should be taken into consideration during future development in the area. © 2020, Springer Nature B.V.
Tracing the isotopic signatures of cryospheric water and establishing the altitude effect in Central Himalayas: A tool for cryospheric water partitioning
(Elsevier B.V., 2021) Neeraj Pant; Prabhat Semwal; Suhas Damodar Khobragade; Shive Prakash Rai; Sudhir Kumar; Rajendra Kumar Dubey; Jacob Noble; Suneel Kumar Joshi; Yadhvir Singh Rawat; Harish Chandra Nainwal; Sunil Shah; Aditya Mishra; Rajeev Saran Ahluwalia
This study focuses on the isotopic characterization of cryospheric water and quantification of different components contributing to Alaknanda River (major tributary of the Ganges River system) at its place of origin near snout of the Satopanth Glacier. A detailed understanding of various sources/flow components contributing to the river is useful for water resource management under changing climate scenario and helpful in risk assessment due to natural hazards in the headwater catchments, Extensive fieldwork was conducted, and water samples were collected from the river, snow, glacial ice, rain, lakes, and supraglacial channels of Satopanth Glacier Basin during the ablation period of 2017 and analysed for δ18O, δ2H, and 3H along with electrical conductivity. The results helped to establish the spatio-temporal and altitudinal variability in isotopic signatures of rain, snow, and ice in Satopanth Glacier Basin. The altitudinal effect in δ18O of pre-monsoon and monsoon rainfall is −0.13‰ and −0.41‰ per 100 m rise in elevation, respectively. Snow samples show depleting isotopic trend with an altitude effect of −0.43‰ in δ18O per 100 m rise in altitude. However, snowpack samples show an enrichment with time indicating post-depositional isotopic fractionation. The contrasting isotopic gradient in debris covered and non-debris covered ice are −0.9‰ and +3.4‰ per 100 m rise in elevation, respectively. These results divulge the spatial as well as temporal variation in cryospheric waters and these variations are used to derive the isotopic signatures of snow melt, glacier melt, and rain water. The results of hydrograph separation show that the snow melt, ice melt and rain water contribute about 33%, 49% and 18% respectively, to the discharge of Alaknanda River during the ablation period. Tracer based hydrograph separation indicates that the snow melt contribution dominates in river discharge during the initial ablation period. River discharge is a mixture of snow melt, glacier melt and rain water during July and August, while there is a dominance of glacier melt during end of the ablation period. The results of the present study highlight the importance of accounting the spatial and temporal variability in tracer signatures of cryospheric water for quantifying the contributions of snow and ice melt in a river originating from glacerised area. © 2021 Elsevier B.V.