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Nepal Hazard Risk Assessment
1.2.7 CATEGORISATION OF LANDSLIDE HAZARD
The obtained landslide hazard indices were calibrated against the databases of landslide events in
selected (mostly European) countries to obtain the frequency of the events. On the basis of this
calibration, the landslide hazard classifications listed in the following table were established.
Values for
Hlandslide, rainfall
Values for
Hlandslide, earthquake Class
Classification of
landslide hazard
potential
Representative
annual frequency in
1 km 2 grid cell
≤ 32 ≤ 55 0 Negligible ~ 0
33 – 81 56 – 146 1 Low 0.01 – 0.2 %
82 – 134 147 – 164 2 Medium 0.3 – 2 %
134 – 288 165 – 591 3 High 3 – 10 %
Figure 1.8. Map of precipitation-induced landslide hazard in Nepal.
1.3 USING THE LANDSLIDE HAZARD RESULTS IN RISK ESTIMATION
The intersection of the landslide hazard "hotspots" with population density (see Figure 1.9) and
infrastructure density maps, and appropriate set of socio-economic indicators (GDP, Human
Development Index, etc.) provides a first-pass estimate of landslide risk "hotspots".
Figure 1.7. Map of earthquake-induced landslide hazard in Nepal.
Since landslides are highly correlated with other natural disasters, one may overestimate the total risk
from all natural hazards if one simply adds the individual risks. This is particularly significant for
earthquake-induced landslides, where the fatalities due to the earthquake event reported in various
databases are inclusive of those caused by landslides. In the analyses presented in this note, the landslide
hazard due to earthquakes and rainfall are differentiated. This should make it possible to correct for
some of the correlations among the risks associated with different natural hazards when the total risk is
estimated.
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