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 - ' 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, " 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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Along Right Bank

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