Landslide Hazard Evaluation and Zonation in and around Hagereselam Town, Tigray, North Ethiopia
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Date
2017-05
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Addis Ababa Universty
Abstract
The present study was carried out in Hagereselam, Wereda Degia Tenben, Tigray Regional State in Northern Ethiopia which is about 828 km far from Addis Ababa. The area is being affected by repeated landslide problems for the past several years therefore seeing the severity of landslide and related instability problems in the area the present research study was conducted. The main objective of the present research study was to evaluate landslide hazard (LHZ) in the study area. For this purpose two approaches were followed to produce the LHZ map. These methods are Slope susceptibility evaluation parameter (SSEP) rating scheme and integrated SSEP and statistical method. The parameters that were considered are slope geometry, slope material, structural discontinuities, landuse and landcover, groundwater, seismicity, rainfall and manmade activities. Beside, inventory on past landslides in the study area was also prepared. Thematic layers on, past landslides, slope facets and causative factors were prepared in GIS environment from secondary data, field observations, topographical maps and satellite images. In SSEP approach facet wise observations were made and ratings for each parameter class was assigned based on conditions prevailed on individual facet. For integrated approach hazard index value was first computed for each of the parameter class. For this density relation between past landslides in the area and each of the parameter class was established through GIS analysis. This hazard index value is a ratio between landslide did occurred to landslide did not occurred within each parameter class. Later, this hazard index value was utilized to modify the original SSEP ratings. Thus, by using these modified ratings LHZ map was produced. The results showed that LHZ map produced by SSEP approach and the integrated approach both has distributed the study area into high hazard and moderate hazard zones. On comparison; LHZ map produced by SSEP shows about 80 % validation, whereas map by integrated approach show about 91% validation with the past landslide activities. Thus, it may be concluded that both methods produced almost similar type of LHZ maps. However, LHZ map produced by integrated approach showed better validation with the past landslide activities.
Key words: Landslide evaluation, Landslide hazard zonation, Slope instability, Hazard index
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Keywords
Landslide evaluation, Landslide hazard zonation, Slope instability, Hazard index