Landslide hazards and mitigation measures at Gangtok, Sikkim Himalaya

Bhasin, Rajinder; Grimstad, E.; Larsen, Jan Otto; Dhawan, A. K.; Singh, Rajbal; Verma, Sachin; Venkatachalam, K

doi:10.1016/s0013-7952(01)00096-5

Cited by 76 publications

(25 citation statements)

References 2 publications

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“…The correlation between rainfall and landslides in Sikkim is well known, with most landslides becoming active during or immediately after the monsoon season (e.g., Bhasin et al 2002;Dubey et al 2005). Although rainfall is clearly related to slope instability in the region, slide activity is not directly correlated with each individual cloudburst event or with every period of prolonged precipitation.…”

Section: Geological Backgroundmentioning

confidence: 99%

Integrated very low-frequency EM, electrical resistivity, and geological studies on the Lanta Khola landslide, North Sikkim, India

et al. 2009

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Landslides are very common in high-altitude Himalayan terrains. Major roads in the Himalayas are frequently blocked due to heavy landslides and remain closed for long periods of time. Permanent mitigatory solutions to these landslides are required to keep the highways open. Lanta Khola, located 71.2 km north of Gangtok (capital of the Indian state of Sikkim), is one of the oldest landslides on the North Sikkim Highway and is active since 1975. The rock types on either side of the landslide are different (augen gneiss in the east and metapelitic schist in the west), and it is believed that the Main Central Thrust passes through the slide zone. Since the slide is invariably activated in the aftermath of heavy rainfall, it is important to identify the subsurface structures that channel water below the landslide surface in order to understand the triggers of slide activity. This can only be accomplished by geophysical survey; however, an appropriate geophysical technique that can be applied in such terrains must be identified. Very low-frequency (VLF) electromagnetic survey was performed over the Lanta Khola landside in order to delineate subsurface structures. Although a very limited number of VLF transmitters are available worldwide, it was possible to pick up VLF signals from a number of VLF stations even in this highaltitude mountainous terrain. VLF measurements along five profiles perpendicular to the geological strike were recorded, and a high conducting zone was delineated from the VLF observations. This conducting zone correlates with the low resistive zone identified from gradient resistivity profiling. The anomalies confirm that there is a water-saturated zone (soggy zone) even in the subsurface of the slide parallel to the geological gneiss-schist contact within the Lanta Khola slide. This indicates that the conductive feature correlates with a weak water-saturated debris layer that lies along the slide and is parallel to the geological contact. Resistive structures on either side of the landslide zone can thus be correlated with the stable ground. It is necessary to drain out water from the soggy zone to minimize slide activity since this zone appears to penetrate into the body of the slide.

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Section: Geological Backgroundmentioning

confidence: 99%

Integrated very low-frequency EM, electrical resistivity, and geological studies on the Lanta Khola landslide, North Sikkim, India

et al. 2009

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“…Landslide occurrences are quite common in the Sikkim Himalaya, and the magnitude of damages caused every year in various parts of the state is quite large (Bhasin et al 2002).…”

Section: Gis Based Spatial Data Analysis For Landslidementioning

confidence: 99%

GIS based spatial data analysis for landslide susceptibility mapping

et al. 2008

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Landslide susceptibility map delineates the potential zones for landslides occurrence. The paper presents a statistical approach through spatial data analysis in GIS for landslide susceptibility mapping in parts of Sikkim Himalaya. Six important causative factors for landslide occurrences were selected and corresponding thematic data layers were prepared in GIS. Topographic maps, satellite image, field data and published maps constitute the input data for thematic layer preparation. Numerical weights for different categories of these factors were determined based on a statistical approach and the weighted thematic layers were integrated in GIS environment to generate the landslide susceptibility map of the area. The landslide susceptibility map classifies the area into five different landslide susceptible zones i.e., very high, high, moderate, low and very low. This map was validated using the existing landslide distribution in the area.

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“…The economic loss and fatalities due to landslides increased greatly in the last century, and most of the landslides resulted from global climate change such as El Niño and unscientific human activities (Au 1998;Yin et al 2000;Schuster and Highland 2001). They are more frequent in young tectonic mountains such as Rocky and Andes mountain chain in American continent (Radbruch-Hall et al 1983;Parise and Wasowski 1999;Collison et al 2000;Mauritsch et al 2000), hills of Japan and Taiwan, and the Himalayas of South Asia (Yamagishi et al 2000;Lin et al 2002;Bhasin et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Some catastrophic landslides since the twentieth century in the southwest of China

Huang

2009

Landslides

221

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Landslides occur frequently in China. Especially, in the western part of China, large-scale landslides are notable for their scale, complex formation mechanism, and serious destruction. This paper presents some typical large-scale landslides that occurred in the southwest of China since the beginning of the twentieth century but were rarely reported worldwide. These cases represent different geological conditions and different triggering factors and mechanisms. The analysis shows that about 80% of large-scale landslides occurred in the first slope-descending zone along the eastern margin of Tibet Plateau, which is tectonically very active. The intensive interactions between the endogenic and epigenetic geological process cause serious dynamic change on the high steep slope and then result in the development of large-scale landslides. Strong earthquakes are also common in this area, and repetitive seismic activities make the slopes unstable and more vulnerable to failures. Besides earthquake, the area also experiences high rainfall, which is also responsible for triggering some of the large landslides.

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Landslide hazards and mitigation measures at Gangtok, Sikkim Himalaya

Cited by 76 publications

References 2 publications

Integrated very low-frequency EM, electrical resistivity, and geological studies on the Lanta Khola landslide, North Sikkim, India

Integrated very low-frequency EM, electrical resistivity, and geological studies on the Lanta Khola landslide, North Sikkim, India

GIS based spatial data analysis for landslide susceptibility mapping

Some catastrophic landslides since the twentieth century in the southwest of China

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