Rainfall thresholds for the initiation of landslide at Lanta Khola in north Sikkim,India |
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| Authors: | A Sengupta S Gupta K Anbarasu |
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| Institution: | (1) Department of Civil Engineering, IIT-Kharagpur, Kharagpur, 721302, India;(2) Department of Geology & Geophysics, IIT-Kharagpur, Kharagpur, 721302, India |
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| Abstract: | In the Indian Himalaya, a 15 km stretch of the North Sikkim Highway that is exceptionally susceptible to landsliding is characterized
by fine-grained, low permeability debris material. Lanta Khola is one of the major debris slides in this stretch and is active
every year during the monsoons. Although the relationship between rainfall and landsliding in the area is obvious, there is
no previous study of precipitation thresholds for landslide initiation. Review of available rainfall and landslide activity
data for the area between 1998 and 2006 suggests that sliding cannot be modeled by typical exponential relationships between
cumulative rainfall (E) and rainfall duration (D). An alternative rainfall threshold has been proposed that predicts sliding if normalized cumulative rainfall for more than
15 days exceeds 250 mm. It is suggested that when this cumulative rainfall threshold is exceeded, the debris zone in the affected
stretch becomes saturated and fails, causing landsliding. |
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