Landslide Hazard Zonation and Slope Instability Assessment by Using Optical and Insar Remote Sensing: the Case of Arbaminch-Gidole Road, Southern Ethiopia
No Thumbnail Available
Date
2018-05-15
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
In the present study landslide hazard zonation and slope instability assessment were carried
out in and around Gidole Town in Southern Ethiopia. The main objective of the study was to
map landslide hazard zone using Information Value Bivariat statistical model and assess the
slope instability using InSAR approach. For landslide hazard zonation of the study area six
causative factors namely; aspect, slope angle, elevation, slope material, Normalized
Deference Vegetation Index (NDVI) and land-use and land-cover were considered. The
landslide inventory mapping for the present study area was carried out through field
observations and Google Earth image interpretation. Later, Information value was calculated
based on the influence of causative factors on past landslide. The distribution of landslide
over each causative factor maps was obtained and analyzed. Weights for the class with in
these causative factor maps was obtained using information value model. Distribution of
landslide in the study area was largely governed by aspect of southwest facing, slope angel of
30-45o, elevation of 1815–2150m, NDVI of 0.27−0.37, slope material of colluvial deposit
and land-use and land-cover of agricultural land. The landslide hazard zonation map shows
that 78.38km2 (36.3%) area fall within very low hazard (VLH) zone, 72.85km2 (34.2%) of
the area fall within low hazard (LH) zone, 12.78 km2 (6.6%), 32.72 km2 (15.4%) and 15.89
km2 (7.5%) of the area falls into very high hazard (VHH), high hazard (HH) and moderate
hazard (MH), respectively. Further, validation of LHZ map with past landslide inventory data
shows that 92.3% of the existing landslides fall in very high hazard (VHH) and high hazard
(VHH) zone. Thus, it can safely be concluded that the hazard zones delineated in the present
study validates with the past landslide data and the potential zone depicted can reasonably be
applied for the safe planning of the area. Further, the landslide activities in the study area
were studied using Persistent Scatterer -Interferometry synthetic Aperture method. For the
analysis radar image was acquired by the Sentinel Satellite for the period 2014−2018. The
result of PS-InSAR processing indicates the average displacement located in the study area
has gradually increasing starting from 15.3mm/yr. to -19.2 mm/yr. The result of the study
area represented in terms of vertical displacement from the satellite Line of sight. Negative
displacement indicates that the land surface is moving away from the satellite line of sight
and the positive sign indicate the area is moving towards line of sight.
Description
Keywords
Landslide, Gidole, Landslide Hazard Zone, PS-Insar, Persistent Scattered