Browsing by Author "Y.P. Sundriyal"

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Assessment of soil erosion, flood risk and groundwater potential of Dhanari watershed using remote sensing and geographic information system, district Uttarkashi, Uttarakhand, India
(Springer Science and Business Media Deutschland GmbH, 2021) Ashish Rawat; M.P.S. Bisht; Y.P. Sundriyal; S. Banerjee; Vidushi Singh
Quantitative morphometric analysis of Dhanari watershed has been done using remote sensing and Geographical Information System (GIS). The impact of climate, lithology, tectonics, structural antecedents, vegetation cover and land use on hydrological processes is assessed by quantifying geomorphic parameters. The Dhanari River (a tributary of the Bhagirathi River) and its tributaries Dhanpati Gad and Kali Gad forms Dhanari watershed covering 91.8 Km2 area. Several geomorphic aspects viz. linear, areal, relief were computed to comprehend potentials of soil erosion, groundwater, flood vulnerability and the geomorphic response of watershed. LISS-III image is used to generate the Land Use and Land Cover (LULC) map and assess the watershed dynamics. Values of computed hypsometric integral and morphometric parameters viz. drainage density (Dd), stream frequency (Fs), stream length ratio (Lur), bifurcation ratio (Rb), rho coefficient (ρ), drainage texture (Dt), circularity ratio (Rc), relief ratio (Rhl), elongation ratio (Re), form factor (Ff), basin shape (Bs), drainage intensity (Di), compactness coefficient (Cc) and infiltration number (If) have shown a moderate and steady erosion rate, with low groundwater potential and low to moderate flood vulnerability in the watershed. Hypsometry presents a dependable geomorphic parameter to understand the erosion and geomorphic response of a watershed to hydrological processes. Hypsometric integral value (0.51) of Dhanari watershed suggests a mature topography with steady erosion in the watershed. © 2021, The Author(s).
Formation of paleovalleys in the Central Himalaya during valley aggradation
(Elsevier Ltd, 2015) Shipra Chaudhary; U.K. Shukla; Y.P. Sundriyal; Pradeep Srivastava; Poonam Jalal
The formation of paleovalleys in mountainous regions is considered to result from extreme events such as landslides and glacial or landslide lake outburst floods. According to IPCC (2012) the extreme events are rarest of the rare weather/climatic events when the climate/weather variable is significantly above or below the defined threshold value. The present study suggests that paleovalleys can also form during years long periods of valley aggradation. A series of paleovalleys thus formed runs parallel to the present river course. In this study, we suggest that paleovalleys in the Alaknanda valley of the Central Himalaya have formed in two ways: 1) major valley aggradation and 2) local events of landsliding and lake breaching. Most of the paleovalleys in the Alaknanda valley formed during a major valley aggradation phase (between 15 and 8ka). Paleovalleys formed due to local landsliding also formed around 8ka. Local landslides were triggered due to high rainfall in lower valley reaches during unstable climatic conditions. Therefore, the formation of paleovalleys both by regional and local mode within 15-8ka indicates that the valley was receiving excess sediment from upper catchment as well as from lower reaches during this period. This phase of excess sediment supply and valley aggradation coincides well with post glacial climatic amelioration. Therefore the study underlines the role of climate in the time scales of 103 years in shaping the landscape of an active mountain like the Himalaya. The role of other landscape changing agencies such as tectonics and erosion is not accounted in the present study. © 2015 Elsevier Ltd and INQUA.
Geo-environmental consequences of obstructing the Bhagirathi River, Uttarakhand Himalaya, India
(Taylor and Francis Ltd., 2020) S.P. Sati; Shubhra Sharma; Y.P. Sundriyal; Deepa Rawat; Manoj Riyal
The Bhagirathi Valley is investigated to understand the impact of various barrages and dams on natural river flow. The multiple barrages and dams in the valley (downstream of the Bhatwari Village) have obstructed/disrupted natural flow of the river which has adversely impacted geomorphological and ecological functions of the river. Besides, it is observed that during and after the implementation of the hydropower projects, the terrain stability was severely affected due to creation of fresh landslide zones, destruction of forest and rural infrastructures including the marginal agricultural lands. The study observes that lack of detailed geological, geomorphological and ecological investigation prior to the execution of the hydropower projects led to the terrain instability. Further, dearth of detailed scientific studies was responsible for the lack of comprehensive engineering/bioengineering measures and catchment area treatment plans as also the measures for reservoir rim slope stability. Taking cognizance from the Bhagirathi valley, present study calls for a detailed multidisciplinary study in the Himalayan valleys where the rivers are likely to get impounded for harnessing hydropower. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Late Pleistocene-Holocene flood history, flood-sediment provenance and human imprints from the upper Indus River catchment, Ladakh Himalaya
(Geological Society of America, 2022) Choudhurimayum Pankaj Sharma; Poonam Chahal; Anil Kumar; Saurabh Singhal; Y.P. Sundriyal; Alan D. Ziegler; Rajesh Agnihotri; Robert J Wasson; Uma Kant Shukla; Pradeep Srivastava
The Indus River, originating from Mana-sarovar Lake in Tibet, runs along the Indus Tsangpo suture zone in Ladakh which separates the Tethyan Himalaya in the south from the Karakoram zone to the north. Due to the barriers created by the Pir-Panjal ranges and the High Himalaya, Ladakh is located in a rain shadow zone of the Indian summer monsoon (ISM) making it a high-altitude desert. Occasional catastrophic hydrological events are known to endanger lives and properties of people residing there. Evidence of such events in the recent geologic past that are larger in magnitude than modern occurrences is preserved along the channels. Detailed investigation of these archives is imperative to expand our knowledge of extreme floods that rarely occur on the human timescale. Understanding the frequency, distribution, and forcing mechanisms of past extreme floods of this region is crucial to examine whether the causal agents are regional, global, or both on long timescales. We studied the Holocene extreme flood history of the Upper Indus catchment in Ladakh using slackwater deposits (SWDs) preserved along the Indus and Zanskar Rivers. SWDs here are composed of stacks of sand-silt couplets deposited rapidly during large flooding events in areas where a sharp reduction of flow velocity is caused by local geomorphic conditions. Each couplet represents a flood, the age of which is constrained using optically stimulated luminescence for sand and accelerator mass spectrometry and liquid scintillation counter 14C for charcoal specks from hearths. The study suggests occurrence of large floods during phases of strengthened ISM when the monsoon penetrated into arid Ladakh. Comparison with flood records of rivers draining other regions of the Himalaya and those influenced by the East Asian summer monsoon (EASM) indicates asynchronicity with the Western Himalaya that confirms the existing anti-phase relationship of the ISM-EASM that occurred in the Holocene. Detrital zircon provenance analysis indicates that sediment transportation along the Zanskar River is more efficient than the main Indus channel during extreme floods. Post-Last Glacial Maximum human migration, during warm and wet climatic conditions, into the arid upper Indus catchment is revealed from hearths found within the SWDs. © 2022. All Rights Reserved.
Mid to late Holocene climate variability, forest fires and floods entwined with human occupation in the upper Ganga catchment, India
(Elsevier Ltd, 2022) Shubhra Sharma; S.P. Sati; N. Basaviaha; Shilpa Pandey; Y.P. Sundriyal; Naresh Rana; Priyanka Singh; Subhendu Pradhan; A.D. Shukla; R. Bhushan; Rakesh Bhatt; Navin Juyal
The present study attempts to understand the geomorphic response in the upper Ganga catchment to the mid-late Holocene (neoglacial) climate variability. The study infers five major phases of millennial-scale climate variability with centennial-scale inversions using geochemical and magnetic proxies from relict Lesser Himalayan Lake sediments. Phase-1 (6–4 ka) is marked by enhanced precipitation/runoff (increased allochthonous contribution) under a stronger Indian Summer Monsoon (ISM). The prominent reversal in the trend between ∼5 and 4 ka includes global arid events such as 4.2 ka. Phase-2 (4–2.2 ka) shows a declining precipitation/runoff (decreased allochthonous input) under declining ISM with a prominent dip after ∼3 ka. After phase-2 the climate reversals are distinct and of shorter (centennial) duration. For example, in Phase-3 (2.2–1.4 ka) improved ISM is inferred; Phase-4 (1.4–1.0 ka) is marked by a sharp decline in the ISM, and Phase-5 (<1.0 ka) includes centennial-scale events of Medieval Climate Anomaly (MCA) and the onset of Little Ice Age (LIA). The relative increase (decrease) in the concentration of geochemical and magnetic proxies is indicative of strengthened (weakened) ISM where relatively drier phases are in sync with the North Atlantic climate perturbations. We observed clustering of optically dated flood events around 6.5, 4.5, 2.6, 1.4, 0.8, and 0.4 ka which corresponds to periods of moderate ISM thus, suggesting a coupling between warm-humid monsoon and relatively dry westerlies. The relatively higher concentration of micro-charcoal in the lake sediments indicates widespread forest fires around 5.9–5.3, 4.5–4.3, 3.4–3.0, 2.0–1.5 and ∼1 ka. Given the archaeological evidence of sedentary settlements since ∼3 ka in the upper Ganga catchment, the study speculatively argues anthropogenic forcing for forest fires after 3 ka. Further, the highest probability flood phases succeed the fire events and may be indicative of enhanced vulnerability of the catchment to floods due to vegetation loss (enhanced erosion and surface runoff). © 2022 Elsevier Ltd
Mountain highway stability threading on the fragile terrain of upper Ganga catchment (Uttarakhand Himalaya), India
(Science Press, 2022) S.P. Sati; Shubhra Sharma; Girish Ch. Kothyari; Maria Asim; Y.P. Sundriyal; Kapil Malik; Ayush Joshi; Harsh Dobhal; Naresh Rana; Navin Juyal
Roads are the most critical means of connectivity in Himalayan villages. However, the terrain is inherently fragile with varied geological, geomorphological, ecological, and climate regimes, that result in frequent slope failure and disruption in connectivity. The risk is further to be increased by extreme events-generated hazards, which are expected to rise in frequency and magnitude with ongoing climate change. Critical scientific intervention, however, can improve the sustainability of road networks. The present study attempts to analyse and quantify the impacts of a major road widening project initiated in 2018 in the upper Ganga catchment, Uttarakhand Himalaya which has destabilised valley slopes along the widened segments. Also, a large quantity of excavated sediments is dumped down slopes, which is posing a threat to aquatic biodiversity. The estimates are based on Google Earth imagery of a few representative road segments recently widened in the upper Ganga catchment, which indicate a substantial increase in the landslide and unstable slope area following the road widening. The increase in unstable slope area is attributed to improper road widening approaches and poor slope management in seismically active Himalayan terrain. Further, the mean velocity plots of Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) indicate that the segments undergoing road widening are coherent with areas of significant earth surface change. A broad correlation between the road width and sediment yield indicates that even a slight increase in road width can result in a large-scale mass removal from the toe of the hillslope, inflicting cascading impact on hillslopes. The study recommends a more flexible road construction approach based on the environmental and geological aspects of the terrain for sustainable road networks. Further, the impact of climate change is looming over the Himalayas, and the relation between climate change and its potential effects on the stability of slopes remains an open issue. © 2022, Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag GmbH Germany, part of Springer Nature.
Quest for disaster-resilient roads in the Himalaya
(Indian Academy of Sciences, 2021) Shubhra Sharma; S.P. Sati; Y.P. Sundriyal; Vikram Sharma; Harsh Dobhal
Mountain roads are important lifelines and the most critical means for connectivity in the Himalayan villages of India. However, the inherent geological, geomorphological, ecological and climate fragility of the terrain warrants critical scientific investigations for the roads to sustain the vagaries of nature. Further, the increased frequency of extreme events with the ongoing climate change increases the potential impact of disasters. This note highlights the major challenges and issues faced with the ongoing road-widening projects in the country. It cautions against the uniform standard of road widening and the need to increase sensitivity towards appreciating the terrain fragility. © 2021
The 23rd April '21 Snow Avalanche, Girthi Ganga post the 7th February '21 Rishi Ganga Flash Flood: Are these Events Linked to Climate Warming in the Western Himalaya?
(Springer, 2021) Shubhra Sharma; Sarswati Prakash Sati; Y.P. Sundriyal; Harsh Dobhal
The upper catchment of Dhauli Ganga valley (Chamoli district) in Uttarakhand Himalaya recently witnessed a large snow avalanche on the night of 23rd April 2021 along the Indo-Tibet border. This event followed the 7th February 2021 Rishi Ganga (debris flow induced) flash flood within less than three months. This note analyses the plausible causes of the avalanche using pre-disaster field survey data, supported by the limited geological and remote sensing based geomorphological investigations as the site could not be investigated due to remoteness of the location and travel restrictions due to COVID pandemic. The present observations suggest that active and relict cirques to the north of the South Tibetan Detachment System (STDS) are the sites for potential snow and debris avalanches under the projected warming trends in the western Himalaya. Particularly, the study calls for climate change adaptation measures in the climate sensitive Trans Himalayan region and optimize anthropogenic activities in order to safeguard the lives and vital infrastructure. © 2021, GEOL. SOC. INDIA.
Unstable slopes and threatened livelihoods of the historical Joshimath town, Uttarakhand Himalaya, India
(Indian Academy of Sciences, 2023) S.P. Sati; Maria Asim; Y.P. Sundriyal; Naresh Rana; Vijay Bahuguna; Shubhra Sharma
This study analyses the causes and consequences of slope instability around the historical Himala-yan town of Joshimath, Uttarakhand, India. The town is in the Higher Himalaya near the Main Central Thrust. The lithology constitutes fissile, shattered and sheared gneiss. Consequently, the slopes are prone to land subsidence and mass wasting. In the last few decades rise in population has led to a surge of infrastructure development, thus causing immense pressure on the finite resources and limited accommodation space on precariously balanced vulnerable slopes. Particularly, the unplanned in-frastructure development, lack of adequate drainage and excavation of roads through unstable debris slopes are some of the reasons that seem to have accelerated the ongoing slope instability and land subsidence. © 2023, Current Science. All Rights Reserved.