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(Lower), Shiviter (Lower), Tindharia T.E. were characterized by upwardly concave
or negative curvature and highest class weight value ranging from 52.09 to 165.71.
The marginal part of the watershed mainly Upper Paglajhora, 14 miles (upslope)
bustee, Gayabari (Upper), and Tindharia (Upper) registered high positive curvature
(Fig.
2.8
, Chap. 2) with maximum landslide frequency and class weight of more than
40. Lithologically, Darjiling Gneiss, Gorubathan, Lingste Granite and Reyang
Formation (Fig.
2.4
, Chap. 2) showed the maximum number of landslide phenomena.
Probability of Landslide phenomena was very high for the lithological composition
of gneiss, mica-schist and granulite. Class weight values of Lingtse Granite,
Gorubathan Formation and Chungtung Formation were 48.98, 50.31 and 23.10
respectively (Table G.1, Appendix G). All these lothological groups were accom-
panied with large number of landslide activities and greater chances of landslip
probability in future. Drainage density (Fig.
3.6
, Chap. 3) was very high at Lower
Paglajhora, Gayabari and Shiviter T.E. which were attributed by high landslide
susceptibility and high frequency ratio (>2.5). The value of the drainage density
increased away from the marginal part to the central part. The area having more that
11 km length of drainage/km
2
were attribute with highest class weight (>140) and
greater probability of landslide phenomena. The values of Upslope Contributing
Area (UCA) increases away from the water divide and the maximum of 20.98 km
2
experienced the lower most portion of the watershed (Fig.
3.7
, Chap. 3). The upslope
contributing area having less than 5 km
2
experienced less saturation excess run-off
and less intensity of landslide. The more contributing areas were registered along the
main rivers that had maximum length and thus maximum flow. The study envisaged
that the place with the UCA of 5.00
10.00 km
2
and 10.00
15.00 km
2
were attributed
-
-
as high
value of 1.21 and 1.48 and class weight values of 20.93 and 48.39
respectively. These places were very much prone to landslide. In Shivkhola
Watershed tea garden, jungle, roads and settlement (Fig.
7.5
) were characterized by
high
'
FR
'
of 1.23, 1.15, 1.98 and 1.14 and highest class weight of 23.73, 15.62, 99.31
and 14.09 (Table G.1, Appendix F). The analysis showed that tea garden, road and
settlement were dominated by high intensity of landslide and could be treated as
maximum probable areas of landslide occurrences. Road contributing area (RCA)
was high at the places of Tindharia, Paglajahora, Mahanadi and Shiviter where the
landslide frequency was also very high (Fig.
7.6
). At all those places the RCA ranged
from 0.008 to 0.014 km
2
and the class weight value ranged between 29.84 and 169.
12. In the study area, construction of roads and slope modi
'
FR
'
cation caused by human
intervention were responsible for slope instability. The moderate to high intensity of
human settlement at Tindharia, Gayabari, Shiviter, Mahanadi and Lower Paglajhora
(Fig.
7.4
) depicted high
'
FR
'
and maximum class weight as well as greater proba-
bility of landslip (Fig.
7.7
).
In Shivkhola Watershed, Lower Paglajhora, Shiviter and Tindharia were very
highly susceptible to landslide; Upper Paglajhora, Gayabari, 14 Miles Bustee and
Nurbong T.E. were characterized by high landslide susceptibility; Mahanadi and
Giddapahar were of moderate landslide potentiality; and marginal waxing slope of
water divide and low-central wanning slope were registered with low landslide
susceptibility (Fig.
7.8
).
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