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Table 2.5 Slope angle and landslide potentiality
Classes
(slope in
degree)
Number of
pixels (F1)
(N
pix(Ni)
)
%of
(N
pix(Ni)
)
Landslide
pixels (F2)
(N
pix(Si)
)
%of
(N
pix(Si)
)
Landslide
potentiality
index
0
-
7.17
3,353
10.12
190
5.63
5.67
7.17
14.34
3,238
9.77
202
5.99
6.24
-
14.34
19.92
3,587
10.83
211
6.26
5.88
-
19.92
-
24.97
2,445
7.38
201
5.96
8.22
24.97
29.75
3,555
10.73
311
9.22
8.75
-
29.75
34.53
2,776
8.38
329
9.75
11.85
-
34.53
-
39.57
3,854
11.63
413
12.24
10.72
39.57
-
45.95
3,276
9.89
427
12.65
13.03
45.95
54.71
3,557
10.74
543
16.09
15.27
-
54.71
67.73
3,490
10.53
646
19.15
18.51
-
of the Shivkhola Watershed with slope angle of more than 40
is registered with
high to very high landslide hazard risk (Fig.
2.6
). It could be demonstrated that
50 % area of the Shivkhola basin is dominated by the high intensity of landslide
with 24
°
. The landslide potentiality index value increases with increasing
slope angle. It is inferred that there is a positive relationship between slope angle
and landsliding in the corresponding study area (Table
2.5
).
°
and 40
°
2.2.7 Slope Aspect and Landslide Potentiality
Slope aspect of the Shivkhola Watershed was derived from the developed digital
elevation model (DEM) with the help of ARC GIS Software. In general, the
watershed shows the south facing slope with some local variation due to the
location of ridges, spurs and valleys. The concentrated local erosion and consequent
development of valleys, landslide scars and other topographic depressions are
responsible for the spatial distribution of slope aspect. This slope aspect is helpful
for the identi
cation of slope segments which are required for the analysis of
potentiality of slope failure. The Fig.
2.6
shows the slope direction and most of the
places show the southward slope with some places of northward slope. The varied
direction of flow based on local slope and orientation of ridges, spurs and valleys
shows the pattern of concentration of surface water and the places of potential
surplus region. The availability of water increases with the increase in the distance
from water divide. Thus at
the lower reach, of every stream,
the availability
becomes more than the upper portion.
North, south, east, north east and south east facing slope are registered with the
landslide potentiality index value of 17.14, 13.10, 15.53, 11.67 and 12.54
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