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2.2.6 Slope Angle and Landslide Potentiality
Firstly, the contour map at 20 m interval was prepared and digitized from the SOI
Topo-sheet (1987, 78B/5) at the scale of 1:50000 and was subsequently used for
generating Digital Elevation Model (DEM) using ARC GIS Software. Then slope
gradient, slope curvature and slope aspect maps were derived from DEM with
25 m grid cell size and classi
cation was made following the earlier works of
Anbalangan (
1992
) and Dhakal et al. (
2000
). The slope is maximum near
Paglajhora area. Hill Cart Road and North Eastern Frontier Rail line (0.61 m gauge)
cross the entire river system twice through this steeper and unstable zone. The slope
is least at the central part where the river develops a cut and
fill terrace. The slope
registers one of the minimum at the crest of water divide and towards the bottom
right of the basin. Slope gradient of the watershed varies from very gentle gradient
(around 10
),
towards the marginal part/water divide. Most of the landslide phenomena were
found in the area of above 35
°
) in the mid central and mid-lower part to that of high (more than 60
°
slope gradient.
In the Shivkhola Watershed high to very high landslide hazard risk is being
found at the place with slope angle between 24
°
. Low to moderate level of
risk is observed in the area pertaining to the slope angle of less than 24
°
and 40
°
°
. Small parts
Fig. 2.6 Spatial distribution of slope angle
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