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Title: Land Slide Assessement and Hazard Zonation in Mersa and Wurgessa, North Wollo, Ethiopia.
Authors: Jemal, Ibrahim
Advisors: Dereje Ayalew(Dr.)
Tarun Kumar Raghuvanshi(Dr.)
Keywords: Landslide
Causative factors
Triggering factors
Landslide hazard zonation
Copyright: Jun-2011
Date Added: 20-Jul-2012
Publisher: Addis Ababa University
Abstract: On August 22, 2010, after a period of prolonged rainfall catastrophic and devastating landslides have been triggered around Mersa and Wurgessa towns, Habru Wereda of North Wollo Zonal Administration, Amhara National Regional State in northern Ethiopia, some 490 km and 465 km respectively from Addis Ababa. These Landslides have caused twenty three causalities, destruction of property and infrastructures, disrupting traffic movement on roads, loss and damage to agricultural lands, and a general degradation of natural environment. The dominant type of slides which triggered was soil slips, translational slides and debris flows. Thus, looking into the severity of such devastating landslide hazard in the area the present research study was conceived, mainly to evaluate the various possible causes which were responsible for the triggering of such landslide hazard in the said area. Besides, to identify those areas which have possible potential for future landslide activities, Landslide hazard zonation of the present study area was delineated. In order to meet out the objectives of the present study a systematic methodology was executed. To develop a conceptual framework of the problem a thorough literature review was carried out. As a part of methodology field trip was made where various kinds of observations and assessments were made pertaining to the causative and triggering factors which might be responsible for the instability of the area. An inventory on various past landslide activities and the potential instability zones in the area was prepared. In order to delineate the Landslide hazard zonation of the area expert evaluation technique was adopted. The technique for Landslide Hazard Zonation (LHZ) proposed by Anbalagan (1992) and modified by Raghuvanshi (2011) has been followed for the present study. This modified technique includes inherent causative factors such as; slope material, slope morphometry, relative relief, landuse/ landcover and groundwater condition. Besides, it considers triggering factors such as; rainfall, seismicity and manmade activities. Based on these inherent causative and triggering factors landslide hazard was evaluated for the present study area. From the field observations and the data analysis on various aspects it was found that the possible cause of past landslide activities is a combination of inherent causative and triggering factors. The inherent causative factors responsible for past activities are; mainly slope morphometry, incompetent slope material and structural discontinuities, whereas the triggering factor was mainly prolonged intensive rainfall and for some slopes the construction activities which has made the slopes steeper locally. The LHZ performed during the present study reveals that 25% of the present study area falls under very high hazard, 69% falls into high hazard, and 6% falls in moderate hazard zone. Further, in order to validate the LHZ map prepared during the present study, past landslide activities and potential instability areas, delineated through inventory mapping, was overlain on it. All past landslide activities and potential instability areas fall within very high and high hazard zone. Thus, the satisfactory agreement confirms the rationality of the considered governing parameters, the adopted methodology, tools and procedures in developing the landslide hazard map of the study area. Further, to avoid/ reduce the hazard in the susceptible zones various remedial measures have been proposed, which include proper drainage of the area and resettlement of residents from high and very high hazard zone to other stable areas.
Description: A thesis submitted to school of graduate studies of Addis Ababa University in partial fulfillment of the requirements for the Degree Of Master of Science in Engineering geology.
URI: http://hdl.handle.net/123456789/3454
Appears in:Thesis - Earth Sciences

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