Geographia Polonica (2011) vol. 84, iss. Special Issue Part 2

Evolution of the Paglajhora slump valley in the Shiv Khola Basin, the Darjeeling Himalaya, India

Subir Sarkar

Geographia Polonica (2011) vol. 84, iss. Special Issue Part 2, pp. Sarkar | Full text

The morphologic configuration of the Paglajhora slump valley is controlled by geologicstructure and remodelled by the hydro-geomorphic processes. The slope forms exhibit a combinationof convex – concave – irregular profiles with highly variable inclination (10° to 35°).Overland flow feeding the uppermost niche during heavy rains transformed into concentratedsub-surface flow over the permeable colluvium. The observed rills and cracks facilitate the pipingand deep drainage towards the slumped areas. The high intensity of the processes as well as therelative heights and steep gradients are the limiting factors in the stabilization of the Paglajhoraslumps. At present, the form reached quasi-unstable equilibrium. Each extreme rainfall (above300 mm/day) causes substantial changes in its morphology.

Keywords: landslide, slump, quasi-unstable equilibrium, colluvium slope, palaeo-landslides, high intensity rainstorm, Darjeeling Himalaya, India.