Application of Analytical Hierarchy Process (AHP) and Frequency Ratio (FR) Model in Assessing Landslide Susceptibility and Risk - Semi-quantitative Approaches for Landslide Assessment and Prediction - page 203

Table 7.4 Determined prioritized class rating value (PCRV) and prioritized factor rating value
(PFRV) of three landslide hazard risk element maps
Weighted LULC
map

Low Moderate High Very high PFRV-

0.691

PCRV 0.06 0.12 0.25 0.55

Weighted RCA map Very

low

Low ML M MH H VH PFRV-

0.218

PCRV 0.02 0.04 0.05 0.09 0.13 0.24 0.43

Weighted settlement
density map

Very
low

Low ML M MH H VH PFRV-

0.091

PCRV 0.03 0.04 0.05 0.11 0.14 0.27 0.37
PCRV prioritized class rating value, PFRV prioritized factor rating value, LULC land use and land
cover, RCA road contributing area, ML moderately low, M moderate ‚ MH moderately high,
H high, VH very high

7.2.2.3 Preparation of Landslide Hazard Risk Map

The prioritized class rating value (PCRV) against each class of landslide suscep-
tibility map and risk exposure map were estimated by developing couple-comparing
matrices on MATLAB Software (Table 7.5 ) after Saaty ( 1980 ). Then, raster inte-
gration between landslide susceptibility and landslide risk exposure was performed
by overlay analysis on ARC GIS platform and

finally landslide hazard risk

co-ef value the same

method was followed like the landslide susceptibility map and the Shivkhola
Watershed was divided into four landslide hazard risk zones i.e. low, moderate,
high and very high.

cient (R) values were derived for each pixel. To classify ' R '

7.2.2.4 FR Study to Establish the Validity of Landslide Hazard Risk
Zones

To evaluate the validity of landslide hazard risk map frequency ratio (FR) value was
estimated for each landslide hazard risk class by means of a ratio between landslide
hazard risk area (%) and landslide hazard risk events (%). The

' FR ' value

' '

approaching towards 0 indicates lower landslide probability and the value

approaching away from denotes greater chances of

landslide risk event in future. The records of the landslide hazard risk events in the
unstable terrain of the Skivkhola watershed were collected from the study accom-
plished by Basu and Ghatowar ( 1988 ), Basu and Sarkar ( 1985 , 1988 ), Basu and
Ghosh ( 1993 ), Basu and Maiti ( 2001 ), Maiti ( 2007a , b ), Ghosh et al. ( 2009 ), and
author himself that were taken into account to estimate frequency ration (FR). The
records depict

' 0 ' or toward ' 1 ' or more than ' 1 '

that since 1968 2011, the Shivkhola watershed faced 128

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