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 195

SiLi
P SiLi

F i ¼ ð 7 : 1 Þ

where, the summation ( Σ ) is for the entire lower neighbour; S is the directional
slope, and L is an effective contour length that acts as the weighting factor. The
value of L used here is 10 m of the pixel size of the cardinal neighbour and 14.14 m
of the pixel diagonal for diagonal neighbour.
The road contributing area (RCA) map (Fig. 7.6 ) was made by multiplying road
contributing length (RCL) with road contributing width (RCW) with eight equal
classes from the concerned topographical sheet and it was converted into raster
value domain on ARC GIS Platform. The Settlement Density Map (Fig. 7.4 ) was
prepared by applying 3 × 3 karnel in ARC GIS platform and the whole basin was

classi ed into seven equal density classes. Land use and land cover (LULC,

Fig. 7.5 ) map of the Shivkhola watershed is prepared with the help of LISS-III
Satellite Image (2010) and Google Earth Image in consultation with SOI Topo-sheet
(78B/5). After verifying the ground truth with GPS a land use and land cover map is
developed in GIS. The Shivkhola Watershed was classi

ed into 10 individual land
use type: (i) bare surface, (ii) agricultural land, (iii) jungle, (iv) roads, (v) settlement,
(vi) tea garden, (vii) open forest, (viii) degraded forest, (ix) mixed forest and (x)
dense forest (Fig. 4.2 , Chap. 4).

7.2.1.3 Landslide Inventory Map

A Landslide Distribution Map/Inventory Map (Fig. 2.1 , Chap. 2) was created to
determine landslide affected area (%) and frequency of landslide for each class of
the landslide inducing factors/factors. Mandal and Maiti ( 2011 ) identi

ed major and

minor landslide locations during field investigation and mapped them by evaluating

the SOI topographic map (78B/5), satellite image (IRS LISS-III, 2000), SRTM data
(2008), and Google Earth Image (2010). Several field investigations were con-

ducted to identify the landslide locations and to cross-check the prepared landslide
map. Then, the map was digitized and converted into raster value domain in ARC
GIS Software. All the landslide triggering factor maps were linked with the
prepared landslide inventory map to understand the degree of importance of each
factor in landsliding.

7.2.1.4 AHP and Quanti cation to Each Factor Map/Prioritized Factor

Rating Value

AHP is a decision making and semi-quantitative value judgement approach which
serve the objectives of the decision makers. This process is employed to support the
decision on the instability rank of the factors by estimating prioritized factor rating
value (PFRV). In the AHP, different factor preference and their conversion into