where SLOPE is slope value; CURVATURE is curvature
value; DRAINAGE is distance from drainage value, LINEAMENT
is distance from lineament value, NDVI is
normalized difference vegetation index value, PRECIPITATION
is rainfall precipitation value, and ASPECTc,
LITHOLOGYc, LANDCOVERc, SOILc are logistic multiple
regression coefficients as listed in Table 2; and p is the
landslide-occurrence possibility.
For landslide hazard mapping, the logistic regression
coefficient values were applied to the study area from which
they were derived, as well as to the other two areas. That is,
the calculated logistic regression coefficient values from
each dataset (for Penang, Cameron, and Selangor) were
applied to all datasets (Penang, Cameron and Selangor).
Overall, there were nine cases for mapping. Thus, the calculated
ratings from the Penang datasets were applied to
Penang, Cameron and Selangor. Similarly, the calculated
ratings from the Cameron datasets were applied to Penang,
Cameron and Selangor, and those from the Selangor datasets
were applied to Penang, Cameron and Selangor, giving
nine sets to be mapped. Using the logistic regression coefficients
(Table 2) and Eq. (1), the values were computed for
the nine cases. If no ratio was available for a certain class,
the average value (i.e., 1) was used.
Hence, as presented in Figs. 2 and 3, nine landslide hazard
maps were calculated. Fig. 2A presents Penang based
on the Penang coefficients, Fig. 3A the same area based
on the Cameron coefficients, and Fig. 3B, on the Selangor
coeffcients. Then the calculated landslide hazard indices
(LHI) were grouped into five groups by equal area classification
(highest 10%, second-highest 10%, third-highest
20%, fourth highest 20% and remaining 40%) for easy
visual interpretation of the landslide hazard areas. The
landslide hazard increases with the increment of the LHI
value. The patterns of the identical study areas proofedto be very similar, but there were some differences in the
distribution of the index values. Fig. 2A, for example,
represents a landslide hazard map of Penang calculated
by using logistic coefficient values from the Penang datasets.
Here the minimum, mean and maximum values of
each LHI are 1.6, 9.15, and 20.38, respectively. Similarly,
Fig. 3A shows a landslide hazard map of Penang calculated
on the basis of logistic regression coefficient values from
the Cameron datasets. In this case, the minimum, mean
and maximum LHI are 4.96, 11.77, and 19.33.