Introduction - Semi-quantitative Approaches for Landslide Assessment and Prediction - page 35

proper knowledge and understanding of the local geological aspects, rainfall and
physical and chemical properties of soil, the construction of Hill Cart Road, trunk
road between Siliguri and Darjiling by outside planners and designers along the
steep escarpment slope has aggravated the problem of slope instability within the
Shivkhola watershed. After the completion of the project they leave the place
without assurance of suf cient training and maintenance of resources. The

responsible local government has also not allocated suf cient resources for regu-

lating land use conversion in the concerned area. Therefore the study on landslides
in relation to land, water and soil will be bene

cial to the local and national
government in planning land use pattern and human construction in a rational
manner for the future prospect and well being of the people living in the study area.
For the ful llment of three objectives mentioned above, the present work is carried

out under the following heads.

Quantitative measurement and analysis of geomorphic and hydrologic param-
eters of slope instability in the Shivkhola Watershed of Darjiling Himalaya.

￿

￿ Preparation of a landslide susceptible map and landslide risk map for under-

standing the spatial distribution of slope instability by analyzing all the landslide
triggering factors corresponding to the Shivkhola watershed.

￿ Preparation of a suitable management plan.

1.8 Applied Methodology

The deductive methodology is followed to investigate into the destructive impacts
of anthropogenic activities on local environment.

Repeated and continued 2011) were made

for the proper cognition of the processes and their interaction. The topographic
factors mainly slope steepness, slope length, contributing area and concavity of
the slope were measured in

field studies for long duration (2006

￿ -

field in consultation with SOI Topographical map
(RF-1:50,000). Slope length and upslope contributing area was measured by
locating the divide on the topographical map and measuring distance from it.
The concavity was measured by means of ratio between area (a) and contour
length (b) following Borga et al. ( 1998 ).

The depth of the slide scar was measured by holding a measuring tape at both
the margins of scar and the other tape was allowed to hang, the reading is then
taken from the base of the hanging tape. The margin of the scars was surveyed
by prismatic compass. The intensive survey of the sliding scar was carried on by
Abney

￿

'

s level at 0.5 m interval along radial lines originating from lower most
part of the scar. The altitude of the points at 0.5 m interval along the radial lines
was then estimated in reference to the central base point of known altitude
determined by GPS (Basu and Maiti 2001 ). The rate of road subsidence (along