Geoscience Reference
In-Depth Information
Chapter 7
Application of Analytical Hierarchy
Process (AHP) and Frequency Ratio (FR)
Model in Assessing Landslide
Susceptibility and Risk
Abstract To prepare landslide susceptibility map of the Shivkhola watershed, one of
the landslide prone part of Darjiling Himalaya, RS and GIS tools were being used to
integrate 10 landslide triggering parameters like lithology, slope angle, slope aspect,
slope curvature, drainage density, lineament, upslope contributing area (UCA), road
contributing area (RCA) settlement density, and land use and land cover (LULC).
Analytical Hierarchy Process (AHP) was applied to quantify all the factors by
estimating factors weight on MATLAB Software with reasonable consistency ratio
(CR). Frequency ratio model (FR) was used to derive class frequency ratio or class
weight incorporating both pixels with and without landslides and to determine the
relative importance of individual classes. All the required data layers were prepared in
consultation with SOI Topo-sheet (78B/5), LIIS-III Satellite Image (2010) by using
Erdas Imagine 8.5, PCI Geomatica, and ARC GIS Software. The weighted linear
combination (WLC) method was followed to combine factors weight and class weight
and to determine the landslide susceptibility coef
cient value (LSCV or
'
M
'
) on GIS
'
'
platform. Greater the value of
M
, higher is the susceptibility of landslide. The
Shivkhola watershed was classi
five landslide susceptibility zones by aver-
aging window lengths of 3, 5, 7, and 9 and taking into account the landslide threshold
boundaries value of 7.05, 9.29, 11.5, and 13.8. The overall classi
ed into
cation accuracy rate
is 92.22 % and overall Kappa statistics is 0.894. The elements like weighted LULC
map, RCA (road contributing area) map and settlement density map were developed
and their weighted linear combination was performed to prepare landslide risk
exposure map. Then by integrating landslide susceptibility map and landslide risk
exposure map landslide hazard risk co-ef
-
cation was incorporated on ARCGIS Platform to prepare landslide hazard risk map of
the Shivkhola watershed. To evaluate the validity of the landslide hazard risk map,
probability/chance of landslide hazard risk event has been estimated by means of
frequency ratio (FR) between landslide hazard risk area (%) and number of risk events
(%) for each landslide hazard risk class. Finally, an accuracy assessment was made
through a comparative study between true GPS derived data and a set of randomly
selected pixels points from the classi
cient values were derived and a classifi-
ed image corresponding to the true data from 50
locations on ERDAS Imagine (8.5) which depicts that the classi
cation accuracy of
the landslide hazard risk map was 92.89 with overall Kappa statistics of 0.8929.
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