Geological and geotechnical characterisation of the Khotila landslide in the Dharchula region, NE Kumaun Himalaya

Abstract

, a severe landslide had occurred in the vicinity of Khotila village in Dharchula, region of NE Kumaun Himalaya. This landslide may be classified as typical rockslide, involving thin veneer of debris on the slope as well as the highly shattered rockmass. The slide has been divided into three morpho-dynamic zones, viz., (i) Zone of detachment between elevation 1000 and 960 m, (ii) Zone of transportation between elevation 960 and 910 m, and (iii) Zone of accumulation between elevation 910 and 870 m. The landslide had occurred at the end of the monsoon season when the slope was completely saturated. It has been noted that the area received ∼88% rainfall during the monsoon months which is about two times more rainfall during 2016 monsoon than during 2015 monsoon. Geotechnical testing of the soil overlying the rockmass, corroborate the soil as 'soft soil' with compressive strength of 42 kPa and friction angle of 27.4 •. Granulometry confirms the soil as having >97% sand and silt size particles and <3% clay size particles, indicating higher permeability. Mineralogically, the soil dominantly constitutes quartz, muscovite and clinochore. Though no swelling clay minerals has been observed, the higher permeability and low strength of the soil, and concentrated higher rainfall during 2016 are the main causes for the landslide to occur. This landslide has partially blocked the flow of Kali river that serve as a boundary between India and Nepal and is endangering the habitants of the Khotila and Bangabagar villages, situated downstream in the Indian and Nepalese side of the Himalaya. In order to understand the stability of the slope, finite element modelling of the landslide has been carried out that points towards higher concentration of stresses in the landslide zone, indicating that there is further probability for the failure of landslide mass. It is therefore suggested that the landslide must be monitored continuously, particularly during the rainy season and also the risk posed by this landslide must be evaluated so as to avoid any further loss to life and infrastructure in the region.

Mechanisms of Initiation, Runout, and Rainfall Thresholds of Extreme-Precipitation-Induced Debris Flows

“…Recently, (Van Asch et al 2014) proposed an integrated model that defines critical rainfall thresholds for runout distances of debris flows based on the experimentally derived equation of erosion from Takahashi et al (1992). Many studies focusing on hazard and risk assessment of shallow landslides in the Indian sub-continent are available (Gupta & Virdi 2000, Gupta & Ahmed 2007, Kumar & Bhagavanulu 2008, Martha et al 2013, Mathew et al 2014, Solanki et al 2019, Vijith et al 2014). However, very few studies are available for debris flows (Kuriakose, Luna, Portugues & Van Westen 2009, Jaiswal et al 2011, Sujatha & Sridhar 2017, Singh et al 2018, Chattoraj et al 2018, Abraham et al 2021.…”

Regional-scale landslide susceptibility assessment for the hilly state of Uttarakhand, NW Himalaya, India

“…Some of the chronic landslides in the area are the Wariya landslide (Yamuna valley), Varunavat Parvat landslide and Natela landslide (Bhagirathi valley), Kaliayasaur landslide (Alaknanda valley), Byung Gad landslide (Mandakini valley), Malpa landslide and Khotila landslide (Kali valley), Surabhi Resort landslides (Mussoorie township), Balia Nala landslide and Sher ka Danda landslide (Nainital township), and there are many more including the Totaghati landslide. All these landslides have been studied in isolation by various workers to understand their causes and consequences in the region and on the environment (Sati et al 1998;Gupta and Bist 2004;Chaudhary et al 2010;Onagh et al 2012;Gupta et al 2016Gupta et al , 2017Jamir et al 2018Jamir et al , 2020Kundu and Patel 2019;Solanki et al 2019;Ram et al 2020).…”

“…Broadly, the quantitative methods are deterministic and statistical. Deterministic methods use algorithms that include geotechnical properties of the soil and rocks on the slopes and topographic parameters of slope surfaces and thus are mainly used for very site-speciBc studies (Solanki et al 2019;Pradhan and Siddique 2020;Tandon et al 2021). Statistical methods elucidate the correlation between the distribution of landslides and different classes of the causative factors of landslides.…”

Application of rock mass classification to evaluate rock properties, NW Himalayas, Pakistan

“…The Himalayan area is structurally dynamic zone described by a structure of thrusted sheets (Kumar, 1971). Slope failures in Himalayan region along road cut sections are frequent and common problem which poses great threat to human life as well as socio-economic developments (Singh et al, 2020;Ansari et al, 2019;Solanki et al, 2019;Gupta et al, 2016;Mahanta et al, 2016). Characteristics of rock mass along the main road is key concern issue in inclined series.…”