Landslide Hazard Zonation Mapping Along Right Bank of Giberiver
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Date
2005-06
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Addis Ababa Universty
Abstract
The hilbide and road cliltings ofmosl parIs oflhe north and westem regions of tile Ethiopinn
Plateau have a record of instability in both the superficd materials and the bedrock. Landslidegenerated
problems claimed many lives and properly dalll2ges in the country.
Landslide hazard zonation is a rapid technique of hazard Jssessment of the land surface. It is used
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to classify the land surface into zones of varying degree of hazard based on the estimated
significance of causative fa, ctors which influence the stability of the land. Since the study area is
extremely rugged and the variation in elevation is very large additionally landslide problems al':
common in the area. Hence the study of landslide anci susceptibility zonation using LHEF is
crucial. The geology of the area is dominated by sheared Jnd discontinuous rhyolite, rhyolitic tutT,
and doleritic intrusions which are liable to failure.
The "Landslide Hazard haluation Factor" (LI IEF) rating scheme, is a numerical system which is
based on major inherent causative factors of slope instab,:ity such as geology, slope m0rphometry,
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relative relief; land use and land cover and groundwater conditions. In the present study on the
basis of Total Estimated Hazard (TEHD) of LHEF, three categories of landslide hazard LOnes haw
been identified. These are low hazard \\ hich occupies 1:'-:0 of the total study area, moderate hazard
(34%). and high hazard (S~%),
Further, potentially unstable critical slopes have heen identified from the High llazard and
Moderately Hazard zones. Later, detailed stability analyses have been carried out for potential
unstable slopes using 'limit equilibrium method'. The 'ta~ility analysis of critical slope sections
has been carried out for static and d.\ namic conditions L,,',der varied water saturation situations. Fo.r
the stability studies data pertaining to structural discont;nuities, Geomechanics (RMR) rock mass
classification system and the slope geometry were collc,,<:ted from the field. Later these data Ilere
lIsed for the computation of Factor of safety. In additi,,~ soil samples were collected and analyzed
for the index propel1ies. From the study, it is found :hat some slope sections are unstable for
anticipated worst conditions. Therefore, safe slope design has been. worked ,out and remedial
measures have also been suggested for these, slope sectk'lls.
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Keywords
Along Right Bank