In the DSH the dominant geomorphic hazard is landslide which is the downhill movement of soil and/or rock under the force of gravity. The difficulty of monitoring frequent landslides, during monsoon, is attributed to its highly dynamic spatial and temporal character, especially in a tectonic regime like the Eastern Himalayas, where the control of structural discontinuities to determine the risk at a local and regional scale is essential. Field data pertaining to spatial distribution of landslides have been collected for about 405 line km along the major road corridors of Sikkim-Darjeeling Himalayas in different parts of Darjeeling district, West Bengal and the state of Sikkim for preparation of a landslide inventory map. This inventory contains information on the landslides occurred along the road during the period from April, 2014 to March, 2015. The present inventory contains information of 52 landslides, of which 45 are rock slides and rests seven are soil/debris slides. Out of the 52 slides 15 slides are new and remaining 37 are old. In total 28 slides are small in nature, nine are medium and 15 are large slides/subsidence. The quantified relations between geology and landslides indicate that soft, fragile and fractured lithology of Daling Group consisting of meta-pelites is the most susceptible and vulnerable to landslides reporting 36 incidences. It also appears that frequency of landslides depends upon intensity and duration of rainfall. Majority of the landslides in the study area are active slides with signs of distressing in the slope forming material and causing damages to the road corridors. This inventory provides a broad database of the landslide incidences along the major stretches of road corridors of the DSH and would help in drawing up planning for investigations, monitoring, installation of early warning system, etc. and for perspective planning for future developmental activities.

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Landslide—A Dominant Geomorphic Hazard

  • Sandipan Ghosh

摘要

In the DSH the dominant geomorphic hazard is landslide which is the downhill movement of soil and/or rock under the force of gravity. The difficulty of monitoring frequent landslides, during monsoon, is attributed to its highly dynamic spatial and temporal character, especially in a tectonic regime like the Eastern Himalayas, where the control of structural discontinuities to determine the risk at a local and regional scale is essential. Field data pertaining to spatial distribution of landslides have been collected for about 405 line km along the major road corridors of Sikkim-Darjeeling Himalayas in different parts of Darjeeling district, West Bengal and the state of Sikkim for preparation of a landslide inventory map. This inventory contains information on the landslides occurred along the road during the period from April, 2014 to March, 2015. The present inventory contains information of 52 landslides, of which 45 are rock slides and rests seven are soil/debris slides. Out of the 52 slides 15 slides are new and remaining 37 are old. In total 28 slides are small in nature, nine are medium and 15 are large slides/subsidence. The quantified relations between geology and landslides indicate that soft, fragile and fractured lithology of Daling Group consisting of meta-pelites is the most susceptible and vulnerable to landslides reporting 36 incidences. It also appears that frequency of landslides depends upon intensity and duration of rainfall. Majority of the landslides in the study area are active slides with signs of distressing in the slope forming material and causing damages to the road corridors. This inventory provides a broad database of the landslide incidences along the major stretches of road corridors of the DSH and would help in drawing up planning for investigations, monitoring, installation of early warning system, etc. and for perspective planning for future developmental activities.