History of landslide susceptibility and a chorology of landslide-prone areas in the Western Ghats of Kerala,India |
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| Authors: | Sekhar L Kuriakose G Sankar C Muraleedharan |
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| Institution: | (1) United Nations University-ITC School for Disaster Geo-Information Management, International Institute for Geo-Information Science and Earth Observation (ITC), Hengelosestraat 99, P.O. Box 6, 7500AA Enschede, The Netherlands;(2) Centre for Earth Science Studies (CESS), Thiruvananthapuram, Kerala, India;(3) Geological Survey of India (GSI), Thiruvananthapuram, Kerala, India |
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| Abstract: | Kerala is the third most densely populated state in India. It is a narrow strip of land, of which 47% is occupied by the most
prominent orographic feature of peninsular India, The Western Ghats mountain chain. The highlands of Kerala experience several
types of landslides, of which debris flows are the most common. They are called “Urul Pottal” in the local vernacular. The
west-facing Western Ghats scarps that runs the entire extent of the mountain system is the most prone physiographic unit for
landslides. The highlands of the region experience an annual average rainfall as high as 500 cm through the South-West, North-East
and Pre-Monsoon showers. A survey of ancient documents and early news papers indicates a reduced rate of slope instability
in the past. The processes leading to landslides were accelerated by anthropogenic disturbances such as deforestation since
the early 18th century, terracing and obstruction of ephemeral streams and cultivation of crops lacking capability to add
root cohesion in steep slopes. The events have become more destructive given the increasing vulnerability of population and
property. Majority of mass movements have occurred in hill slopes >20° along the Western Ghats scarps, the only exception
being the coastal cliffs. Studies conducted in the state indicates that prolonged and intense rainfall or more particularly
a combination of the two and the resultant pore pressure variations are the most important trigger of landslides. The initiation
zone of most of the landslides was typical hollows generally having degraded natural vegetation. A survey of post-landslide
investigation and news paper reports enabled the identification of 29 major landslide events in the state. All except one
of the 14 districts in the state are prone to landslides. Wayanad and Kozhikode districts are prone to deep seated landslides,
while Idukki and Kottayam are prone to shallow landslides. |
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| Keywords: | Landslides The Western Ghats scarps Kerala Land use Debris flows Rainfall intensity Pore pressure |
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