sp sati

The slope instability in the Himalayan terrain is a common phenomenon which is caused by a combination of the ongoing seismicity and climate variability (extreme weather evets). In addition to this, in the last few decades, the anthropogenic intervention in the form of various developmental activity (roads, hydropower projects, expansion of urban sectors etc.) have posed serious threat to slope stability. In this study we have evaluated the terrain status for landslide susceptibility in a monsoon fed Giri Watershed. An attempted has been made to decouple various causative factors of landslides susceptibility of the region using remote sensing and GIS techniques. Employing the Frequency ratio and the information value methods, the study observe that increasing incidences of landslides occur along the drainage in the lower valley sides, along the linear developmental activities and settlement areas. Further the study observed a broad correlation between rock formation, lineaments, veg...

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.

Abstract Active surface deformation, displacement pattern, and erosional variability is estimated using the geomorphologically sensitive morphometry along with the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique using the Sentinel-1Adata (119 images) acquired between 07- 02-2017 and 10-02-2021. The average velocities for this dataset are estimated to be between ±11 mm/y. The Raunthi River catchment from where the flood was triggered is undergoing ~8 mm/y subsidence and ~10 mm/y uplift. Compared to this the basin wide deformation (Rishi Ganga basin) is estimated to be around ±10 mm/y with commulative ground displacement of around ±45 mm. The times series analysis suggests an increase in the ground displacement by around 5 mm/y and seems to be responsible for the expansion of pre-existing cracks in the vicinity of the Vaikrita Thrust (VT) and subsequent failure of the northern face of Nandi Peak on 7th February 2021. The Global Positioning System (GPS) derived strain distribution pattern indicate a relatively higher accumulation of strain (>0.35µ strain/y). The normalized steepness index (ksn) variation along the longitudinal section of Rishi Ganga and Raunthi River sub-basin in Central Himalayan region shows anomalous increase at the glacio-fluvial transitional processes. Moreover, the χ profiles as well as planform plots shows anomalously lower values within the Raunthi River sub-basin when compared with the Rishi Ganga basin. Based on the lower values of χ it is observed that Raunthi River sub-basin is undergoing high erosion which can be caused by the presence of sheared lithology and incision of the relict glacial and paraglacial sediments. We negate the suggestion that abrupt rise in the temperature was the major triggering mechanism for the recent disaster, instead it is the sheared lithology and pre-existing fissure developed because of differential uplift and subsidence in Raunthi River that led to the wedge failure and subsequent flash flood. Had the climate was the major driver of the recent tragedy ?, it should have impacted multiple hanging glaciers in the Rishi Ganga valley. Therefore, the study calls for detailed geomorphological, structural and glaciological investigation in regions dominated by glacial and paraglacial processes in the strategic regions of the Himalaya. Towards this, the state of art PSInSAR technique seems to provide fast and reliable detection of terrain instability/stability along with identification of potential areas of slope failures in near future in the glacial and preglacial zones.

A short-lived flashflood in Rishi and Dhauli Ganga rivers on 7th February 2021, Uttarakhand Himalaya, killed 65 people with 141 reported missing (official estimate) and devastated two hydropower projects. Geomorphological observations supported by meteorological data suggest that the flood was triggered by a combination of avalanche and debris flow. The Dhauli Ganga valley has preserved ponded sedimentary sequences (laminated sand and silty-clay), suggesting that the valley is prone to episodic mega foods in the recent geological past. Considering that the receding glaciers in the higher Himalaya have left behind enormous sediment, unusual weather events are likely to generate such disasters more frequently as the climate becomes warmer. Thus, the study calls for not only incorporating the disaster risk assessment in the developmental planning of the Himalayan region but also recommends routine monitoring of the potential areas of structural failures in the glaciated valleys along with supra-glacial lakes.

Increase in rainfall during the early Holocene has been reported from different regions of Indian subcontinent, although the magnitude shows spatial variability with lower change in higher rainfall regions and vice versa. While the early-Holocene rainfall records are available from lowland areas of the Indian sub-continent, the record is poorly documented from the high-altitude Central Himalayan region where orography plays an important role in the spatial variability in the rainfall pattern. For the first time, δDC29, δ13CC29 values of alkane and δ13C values of organic matter from a relict lake of Benital area in the Central Himalaya have been used to reconstruct monsoonal rainfall and contemporary vegetation for last 10.5 ka with an emphasis on the early Holocene. The δDC29 values suggest that the early Holocene was characterized by a wet phase at ca. 9 ka with 25% higher rainfall compared to present while the middle-late-Holocene was relatively arid. The estimated increase in mon...

Abstract Relict lake sediments situated within the transition of the lesser and higher central Himalayas show a persistent millennial to centennial-scale monsoon variability during the Holocene. Based on high resolution geochemical data supported by radiocarbon dating, six phases of enhanced Indian Summer Monsoon (ISM) with varying magnitude have been identified. These are dated between 10,000–9600, 9500–9200, 8600–5800, 5000–4200, 3500–2400 and 1800–1000 cal yr BP. The millennial and multi-centennial-scale phases of enhanced ISM are broadly comparable with the existing continental and marine records from the monsoon dominated region of SE Asia, suggesting sensitivity of the regions to short-term climatic perturbations. Further, the study observed that the phases of weakened ISM largely correlate with the drift-ice record of the northern Atlantic implying a coupling between short-term solar irradiance induced glacial boundary condition in the northern Atlantic and the millennial and multi- centennial scale monsoon variability in the central Himalaya.

... 605– 608. 4. Bhandari, RK, Keynote address in India Disaster Management Congress, New Delhi, 2006. 5. Sati, SP, Rawat, GS, Kumar, Deepak and Satendra, In Proceedings of the Na-... Sci., 2007, 4, 344–353. 8. Gupta, V. and Bist, KS, Curr. Sci., 2004, 87(11), 1600–1605. ...

In this paper an attempt has been made to identify places of high surface uplift in the Alaknanda valley using the steepness index method. Locations that are undergoing faster surface uplift are marked by convex river profile and high steepness index (ks) values. Conventionally, ...

We present observations on landslide-dammed lake deposits located in the vicinity of the E–W and NW–SE trending, south-dipping North Almora Thrust, in the Alaknanda Basin around Srinagar Garhwal. Prelimi-nary observations suggest that activation of crumpled and ...

Uttarakhand has witnessed one of the worst forest fires in the recent times. As expected, majority of fire incidents are reported from the pine forests. Till 30 April 2016, around 20,000 hectare of the forest was engulfed by the fire and 10 people lost their lives. In fact entire system looked helpless in front of the towering inferno in the Uttarakhand jungle. The fire was unprecedented as it virtually swept the entire Uttarakhand and part of Himachal. The disaster mitigation machinery and the forest department should discuss ways and means and evolve methodologies for preventing such incidences of fire in future.

We present observations on landslide-dammed lake deposits located in the vicinity of the E–W and NW–SE trending, south-dipping North Almora Thrust, in the Alaknanda Basin around Srinagar Garhwal. Prelimi-nary observations suggest that activation of crumpled and ...

ABSTRACT The floods in the parts of the north-west Himalayan region caused severe damage in the Uttarakhand state of India and in some parts of western Nepal. The severity of the floods and damage was maximum in the Kedarnath region, home of a very famous Hindu pilgrimage. It caused the death of about 4000 people and almost a similar number are still missing. The flash floods were mainly caused by the heavy rainfall, triggering landslides in some places, damaging buildings and infrastructures. The extensive damage and large death toll expose the vulnerability of the mountainous region and lack of coordinated relief and rescue operation.