Landslides cover down slope movements of soil and rock material in masses under
gravity. Many of the natural hill slopes that are considered safe in the past
are now recording landslides due to human interventions in hill slopes.
Landslides are normally associated with intense monsoon and inter-monsoon rains.
Nearly 13,000 km2 (20% area of the country) in ten administrative districts such
as Badulla, Nuwara Eliya, Matale, Kandy, Kegale, Rathnapura, Kalutara, Galle,
Matara and Hambanthota are considered to be landslide prone.
National Building Research Organisation (NBRO) in 1985 started to identify
contributory factors for landslides and potentially dangerous slopes; establish
criteria for selection of land for development; design guidelines to mitigate
and manage landslides including early warning systems. In June 1986 NBRO to
undertook a long-term mapping of landslide hazards at 1:50,000 scale at district
level and 1:10,000 scale for selected high priority areas.
In the landslide hazard profile 1:50,000 hazard zonation maps were prepared
using relative contribution of causative factors, namely, Bedrock Geology, Slope
Angle Range and Land use and Land Management along with assigned weights and
ratings based on their relative contribution. The weights and ratings have been
decided on considering expert opinion and statistical analysis of historical
data. Considering the complex nature of landslide potential decided based on the
variations of causative factors the predicted landslide hazard zones are
expressed more in descriptive terms such as landslides are most likely to occur.
Landslide hazard zonation maps are useful in planning human settlements,
infrastructure and other development activities and investments in mitigation.
Same information provides the base for landslide guidelines and local authority
level permitting in landslide prone areas.
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Download The Report on Landslides here