Yaspal Sundriyal

Abstract The geomorphic changes over the earth’s crust are influenced by tectonic activities. These geomorphic changes are remnants of deformation that occurred in the recent geological past. Geomorphic features can be quantified to assess relative tectonic activity and response of landscape to active tectonics, regional structures, lithology and climate. To achieve the objectives, we evaluated the relative tectonic activity of the Garhwal synform, for which six major river basins were selected. The relative tectonic activity of all the basins is computed based on quantitative analysis of geomorphic indices. Quantitative analysis of each geomorphic parameter has been carried out, and a combined product of relative tectonic activity index (TAI) was derived for each basin. The TAI is classified into three classes based on their relative tectonic activity; basins having TAI value ≤1.75 (basins I, II and III) are placed in very high tectonic activity class, basin with a value ranging >1.75 to <2.0 are categorised as moderately active basins (basin ‘IV’), while basins having values >2.0 are less active (basins V and VI). A relative tectonic activity map of the area suffices for the prioritisation of each basin based upon their TAI. Furthermore, analysis of the longitudinal profile of rivers for knickpoint, precipitation and temperature variability over the last 100 years and seismic events since the last 100 years have been studied to interpret the tectonic regime and their influence on landscape evolution. The regional seismicity data suggest that the area falls in a seismic gap and has not experienced a great earthquake in recent history but have received seismic events of moderate intensity in the past. We opine that the Garhwal synform is tectonically active, and thus, significant steps should be taken for seismic risk assessment along with preventive measures. We also suggest that the influence of tectonic activities in the southeastern part of the Garhwal synform comprised by basins V and VI is relatively less than the rest of the basins. Finally, the six basins were prioritised based on their relative tectonic activity. Research highlights Assessment of geomorphic indices from 30 m shuttle radar topography mission-digital elevation model (SRTM-DEM) in six drainage basins of the Garhwal Himalaya. Six river basins categorised under relative tectonic classes based on the calculation of geomorphic indices. Correlation of the large-scale geological setting and drainage basin dynamics contemplated with field evidence and regional seismicity. Quantification of relative tectonic activity index (TAI) of six river basins in the Lesser Himalaya of the Garhwal Himalaya.

Uttarakhand region in the NW Himalaya has experienced two extreme climatic-geomorphic events within last 10 years that killed more than 6000 people. Though these events, like many others in the Himalaya, have been attributed to climate-change and anthropogenic disturbances, identification of potential hotspots of land use/land cover change is rarely attempted to make future inferences for disaster risk reduction. An evaluation of spatio-temporal changes in land use/land cover can be used to identify such hotspots. Therefore, we analysed the spatio-temporal changes in a climatically sensitive and natural disaster-prone area (~28856 km2) of Uttarakhand (NW Himalaya), India, by comparing the satellite data of years 1991-2020 for ten land use/land cover elements to track the spatio-temporal changes over these years. Results revealed the formation of two hotspots exhibiting relatively more changes in land use/land cover pattern. Though the anthropogenic influence is observed in both hots...

<p>Alaknanda River valley in the NW Himalaya has been subjected to frequent landslides of different types and sizes owing to its geographical position and topography that receive extreme rainfall from Indian Summer Monsoon and Western Disturbance. Such landslides, mainly debris flow, pose a growing risk to the rapidly growing human population and result in huge sediment influx into river valleys that contribute to fluvial regime changes.</p><p>In this study, we have simulated runout characteristics of four debris-flow landslides based on inputs from field observation and high-resolution satellite imagery analysis. These landslides are situated along the river valley and accommodate villages/towns near the crown/toe of landslides. Hillslopes constituting these landslides are mostly made up of schist/quartzite/gneissic rock mass, and regional thrust fault passes in the vicinity, contributing to shearing. A Voellmy-Salm fluid-flow continuum model was used to perform debris flow simulations. Frictional, turbulence, and cohesion parameters are probabilistic to eliminate uncertainty, caused mainly by selective input values.</p><p>Results indicated that debris flow from these landslide slopes might reach up to 250 m upstream and downstream along the river during extreme rainfall events, contributing to sediment influx, with a flow velocity and height of 5-10 m/sec and 6-13 m, respectively. Further, the human population residing near the crown/toe of these landslides might be subjected to ground instability and subsequent failure due to shear strength loss. Such predictive studies contribute to the effective evaluation of growing hazards associated with hillslopes during extreme rainfall events. </p><p><strong>Keywords: Debris flow; Rainfall; Himalaya</strong></p>

<p>We have mapped more than 400 major landslides (debris slides, rockfalls, and rock avalanches) in 5 fluvial valleys in Himalaya (India) between 77.3° E - 80.5° E longitudes. Field/high- resolution satellite imagery based landslide area mapping and field based landslide thickness approximation were used to determine landslide area and volume. Area-volume scaling exponents of these landslides revealed a lateral variation in the study area implying that landslide slopes in the eastern part  of the study area retain relatively less volume that increases towards western part of the study area. We have hypothesized that such lateral variation is possibly caused by lateral variation in the landslide occurrence that in turn is mostly caused by lateral variation in the seismic-climatic regimes.  </p><p>Following the hypothesis, we noted that rainfall, surface runoff, soil moisture, and air moisture (climatic variables) data of years 1982-2020 represent a general decrease laterally from east to west in the study area. Further, the role of  topography on the climate variables is also noted as it increases from east to west.  Earthquake (Mw=>4) distribution (1960-2020), Arc Parallel Gravity Anomaly (APGA), cumulative seismic moment, shear stress accumulation rate, and convergence (India-Eurasia) rate  (Seismic variables) also represent a general decrease laterally from east to west in the study area.  The climatic variability is attributed to the spatial variability of the Indian Summer Monsoon (ISM), whereas seismic variability is referred to the spatial variability in the subsurface pattern of the Main Himalayan Thrust (MHT). Thus, such variability in the seismic-climatic regimes is noted to support our hypothesis.   </p>

A flash flood that originated from Raunthi Gad-a tributary of the Rishi Ganga river, in Garhwal Himalaya, caused unprecedented loss to lives and damaged two hydropower projects on 7th Februray 2021. In order to asses the flood magnitude, the flow parameters of the flood were calculated using the super-elevation of the flood marks preserved in the flood affected valleys. The textural characteristics of the flood deposits in the upper reaches of the valleys indicate dominance of debris flows. The peak discharge upstream of the confluence of Rishi Ganga and Dhauli Ganga was around 1.1×105 m3/s, which was four order of magnitiude higher than the normal peak discharge (∼ 3 m3/s). The flow achieved a velocity of 30±3 m/s. An exponential reduction in the flow velocity (from ∼37 to 2 m/s) with distance is observed. For which the river gradient and increase in sediment load is implied flow that along its entrained way downstream between Raini and Tapovan. Considering the sensitivity of paraglacial zones to climate change, the paper calls for detailed studies pertaining to the response of paraglacial zones to extreme weather events. Importantly, it is necessary to have more hydrological data covering multiple valleys for predictive model simulation of the nature and magnitude of such disasters in future.

Active tectonics is manifested in geomorphological features such as drainage basins and drainage patterns. Geomorphic parameters asymmetry factor (AF) and transverse topography symmetry factor (T) is calculated for 94 third order basins of the Garhwal synform to decipher the tilt-block tectonics based on remote sensing and geographical information system (GIS) techniques. The quantitative analysis of the AF suggests that all the 94 basins are asymmetric and gentle to steeply tilted, indicating active tectonics and early and late stage of development, respectively. The mean vector magnitude (θv) of T suggests the migration of the basin stream towards the south in most basins (60%), suggesting a unidirectional tilting of the tectonic block. The χ2 test for statistical significance indicates that the θv is significant for southern and northern limb basins. The χ2 test affirms that the third order basin position on either side of the main channel of the river basin influences the tilt d...

A 4.9-m-thick lake sequence, formed due to the landslide damming of a stream in the semiarid Garhwal Himalaya, was studied to understand past monsoonal variations in the region. The Optically Stimulated Luminescence (OSL) chronology indicates that the lake existed between ~ 12 and ~ 7 ka ago. Chronologically constrained trends of sand percent, organic phosphorus (OP), apatite inorganic phosphorus (AIP) and parameters of environmental magnetism were measured in the paleolake profile. Measured proxies indicate that the Indian summer monsoon ameliorated in the early Holocene after 12 ka cooling, and it appears that all the proxies from the lake have captured this globally recognized early Holocene warming. Four phases of wet conditions (intensified monsoon) are recognized at ~ 11.5 ka, ~ 11–10.5 ka, ~ 10–9 ka and ~ 8–7 ka with maximum uncertainties of ~ 1000 years. The wet phases are characterized by high magnetic susceptibility, increased OP and reduced AIP. In an attempt to understan...

Khajnawar village in Saharanpur district of western Utter Pradesh is inhabited over the remains of an ancient archaeological settlement. Field observations and archaeological investigation reveal two periods of settlement: settlement I with grey ware and iron objects and settlement II with painted red ware. Radiocarbon and optical stimulated luminescence (OSL) dating indicate 2600a-1400a age for settlement I and 850a-350a for settlement II. A hiatus of~ 550a between the two settlements may have been caused either by an ...

APLED-2, PRL, Ahmedabad 115 [IT. 11] Himalayan Rivers: responses to past climatic changes Pradeep Srivastava1*, Yogesh Ray1, YP Sundriyal2, Rashmi Gairola1, Shipra Chaudhary2 1Wadia Institute of Himalayan Geology, 33 GMS Road, Dehradun 248001 2Department of ...

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 ($$D_{{\text{d}}}$$ D d ), stream frequency ($$F_{{\text{s}}}$$ F s ), stream length ratio ($$L_{{{\text{ur}}}}$$ L ur ), bifurcation ratio ($$R_{{\text{...

The Zanskar River, one of the largest tributaries of the upper Indus catchment, drains transversely northward from the Higher Himalaya, dominated by the Indian summer monsoon, to flow through the arid, westerliesdominated, highly folded and thrusted Zanskar ranges in Ladakh. The Doda and the Tsarap Lingti Chu join to form the Zanskar, which in turn joins the Indus at Nimu. With an average gradient of ~ 4 m/km, the Zanskar has a gradient ~2.5 times lower than that of rivers like the Ganga and Brahmaputra, which flow through the southern wet Himalaya. Based on Stream Length (SL) gradient index and valley width and height ratio, the Zanskar valley can be divided into upper and lower divisions, separated by a gorge of nearly 60 km length. The river channel in both the divisions is flanked by 10–30m thick valley-fill deposits that in the upper part are amalgamated with fan and paleolake deposits. Using these fills and incorporating morpho-stratigraphy, Optically Stimulated Luminescence (OSL) dating and provenance analysis based on U—Pb Zircon chronology, the study show that the Zanskar valley aggraded in three phases: (i) the oldest phase during ~43 to ~32 ka (cool and wet MIS 3), (ii) during 20–12 ka, a climatic transition from the dry LGM to the wet early Holocene and (iii) the youngest aggradation phase commenced between 9 and 6 ka, corresponding with the trengthened monsoon phase of the early–mid Holocene. The study implies that, during the oldest aggradation phase, the wider Padam basin stored 3.25 ± 0.11 km3 of sediment, which, in the present geomorphic setup is 0.96 ± 0.10 km3. The provenance analysis suggests that, despite the presence of the deep narrow gorge and a low gradient, the upper and lower Zanskar valleys remained connected throughout their aggradational history. Unlike in the southern wetter Himalaya, where catchment-wide exhumation is the main source of sedimentation, valley filling in the Zanskar basin has been overwhelmed by sediment derived from headward erosion.

We provide the first continuous Indian Summer Monsoon (ISM) climate record for the higher Himalayas (Kedarnath, India) by analyzing a (14)C-dated peat sequence covering the last ~8000 years, with ~50 years temporal resolution. The ISM variability inferred using various proxies reveal striking similarity with the Greenland ice core (GISP2) temperature record and rapid denitrification changes recorded in the sediments off Peru. The Kedarnath record provides compelling evidence for a reorganization of the global climate system taking place at ~5.5 ka BP possibly after sea level stabilization and the advent of inter-annual climate variability governed by the modern ENSO phenomenon. The ISM record also captures warm-wet and cold-dry conditions during the Medieval Climate Anomaly and Little Ice Age, respectively.

We use paleoflood deposits to reconstruct a record of past floods for the Alaknanda-Mandakini Rivers (Garhwal Himalaya), the Indus River (Ladakh, NW Himalaya) and the Brahmaputra River (NE Himalaya). The deposits are characterized by sand-silt couplets, massive sand beds, and from debris flow sediment. The chronology of paleoflood deposits, established by Optically Stimulated Luminescence (OSL) and 14 C AMS dating techniques, indicates the following: (i) The Alaknanda-Mandakini Rivers experienced large floods during the wet and warm Medieval Climate Anomaly (MCA); (ii) the Indus River experienced at least 14 large floods during the Holocene climatic optimum, when flood discharges were likely an order of magnitude higher than those of modern floods; and (iii) the Brahmaputra River experienced a megaflood between 8 and 6 ka. Magnetic susceptibility of flood sediments indicates that 10 out of 14 floods on the Indus River originated in the catchments draining the Ladakh Batholith, indicating the potential role of glacial lake outbursts (GLOFs) and/or landslide lake outbursts (LLOFs) in compounding flood magnitudes. Pollen recovered from debris flow deposits located in the headwaters of the Mandakini River showed the presence of warmth-loving trees and marshy taxa, thereby corroborating the finding that floods occurred during relatively warm periods. Collectively, our new data indicate that floods in the Himalaya largely occur during warm and wet climatic phases. Further, the evidence supports the notion that the Indian Summer Monsoon front may have penetrated into the Ladakh area during the Holocene climatic optimum.

The entire Indo-Himalayan region from northwest (Kashmir) to northeast (Assam) is facing prevalence of floods and landslides in recent years causing massive loss of property, human and animal lives, infrastructure, and eventually threatening tourist activities substantially. Extremely intense rainfall event of 2013 C.E. (between 15 and 17 June) kicked off mammoth flash floods in the Kedarnath area of Uttarakhand state, resulting in huge socioeconomic losses to the state and country. Uttarakhand is an important hilly region attracting thousands of tourists every year owing to numerous shrines and forested mountainous tourist spots. Though recent studies indicate a plausible weakening of Indian summer monsoon rainfall overall, recurrent anomalous high rainfall events over northwest Himalaya (e.g.-2010, 2013, and 2016) point out the need for a thorough reassessment of long-term time series data of regional rainfall and ambient temperatures in order to trace signatures of a shifting pattern in regional meteorology, if any. Accordingly, here we investigate ~100-year-long monthly rainfall and air temperature time series data for a selected grid (28.5°N, 31.25°N; 78.75°E, 81.25°E) covering most parts of Uttarakhand state. We also examined temporal variance in interrelationships among regional meteorological data (temperature and precipitation) and key global climate variability indices using advance statistical methods. Major findings are (i) significant increase in pre-monsoon air temperature over Uttarakhand after 1997, (ii) increasing upward trend in June–July rainfall and its relationship with regional May temperatures (iii) monsoonal rainfall (June, July, August, and September; JJAS) showing covariance with interannual variability in Eurasian snow cover (ESC) extent during the month of March, and (iv) enhancing tendency of anomalous high rainfall events during negative phases of Arctic Oscillation. Obtained results indicate that under warming scenario, JJ rainfall (over AS) may further increase with occasional extreme rainfall spells when AO index (March) is negative.

ABSTRACT The fluviatile succession of Siwalik Group of the Himalayan Foreland Basin (Siwalik Group) represents one of the largest and active basins that have recorded the various manifestation of source area tectonics The distinct grey, salt and pepper textured 7.7-4.5 Ma sandstone of the Baliagad -Gaula River (BGR) Section, Ramganga sub-basin is characterized by its framework components as coarse-medium- to fine- grained matrix- poor lithic to sublithic arenite and matrix- rich quartz wacke. The textural and compositional variability of the sandstone suggests a mixed provenance comprising abundant metamorphic subordinate sedimentary and igneous. The quartz fabric and the metamorphic ranks of rock fragments hints towards the presence of low to medium grade metamorphic source. The temporal variability of sandstone types, Qp/Qm ratio and relative increase of metamorphic rock fragments suggests tectonic activity in the source area at 6.25 Ma and 5.15 Ma. The quartz fabric study further adds that the source area had suffered a temperature of at least 500ºC. Three hinterland thrust, namely the Main Boundary Thrust (MBT), Ramgarh Thrust (RT) and Almora Thrust (AT) played an important role for the supply of detritals to the depocentre. The present study infers the existence of crystalline nappes of the Ramgarh and Almora prior to 7 Ma. The MBT is responsible for exhuming the Lesser Himalaya after 5 Ma.