- The document discusses landslide hazard mapping methods and procedures, including landslide hazard mapping (LHZ) in Ethiopia. - Common landslide types in Ethiopia's highlands include debris/earth slides, debris/earth flows, and rockslides, which are often triggered by heavy rainfall. - Examples of LHZ studies in different parts of Ethiopia are presented, using both qualitative and quantitative/statistical approaches. Factors like geology, slope, land cover are considered. - In conclusion, population growth, geological/hydrological conditions, and heavy rainfall exacerbated by slope modifications are significant contributors to landslide risks in Ethiopia's highlands. LHZ can help identify at-risk

1. ADDIS ABABA SCIENCE AND TECHNOLOGY UNIVERSITY
COLLEGE OF APPLIED SCIENCE
DEPARTMENT OF GEOLOGY
ADVANCED GEOHAZARD (GEOL 6088)
SEMINAR ON : LANDSLIDE HAZARD MAPPING IN ETHIOPIA
PRESENTER : AZMERAW W.
6/12/2018 1
ENGINEERING GEOLOGY(MSc)
AASTU, ETHIOPIA

2. • Introduction
• landslide Hazard mapping methods
and procedure
• Types , factors , distribution and
effects of landslide in highland of
Ethiopia
• Some examples of landslide hazard
zonation in different part of Ethiopia
• Conclusion
Presentation outline
6/12/2018 2

3. 1. Landslide hazard map introduction
• Landslide is one of the most significant natural
hazards in many area throughout the world(crozier
& Glade , 2005;Varnes,1996)
• It cause damage million of dollars & hundred
thousands of casualties & injury every year (pan et
al.,2008) because of
• Urbanization & development in landslide
prone areas.
• deforestation of landslide prone areas, and
• Intensive & prolonged rain fall
•
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4. 6/12/2018 4
F.C. Dai et al. (2002)
2. landslide Hazard mapping methods and procedures

5. 3. Data needs for landslide hazard mapping
• Data which required for LHZ is different for
different methods, for instance, statistical
analysis methods will need:
• Topographic map
• Geologic map
• Data of seismic history
• Satellite / google earth image
• Hydrologic record data
• Landslide inventory map
• Land use /land cover map
• Slope map
• Slope aspect map
• Curvature map
• Soil map
• Elevation map
• Geomorphology
• Geotechnical approach will need :
soil thickness, soil strength, groundwater
pressures, slope geometry etc.
M.Paris (2000)
6/12/2018 5

6. 4. landslide Hazard zonation procedure
• Three key assumptions are used to LHZ
preparation such as
• Identified landslides and factors of LS
• Estimate relative significance of the
factors
• Estimate future slope instability based
on factors of past LS
British geological survey(2000)
• To prepare LHZ the following skills are
important :
• RS & GIS analysis techniques
• Data collection & RS data type selection
• LS inventory map preparation
• Image processing & interpretation
• Data interpretation & verification
• Database building
• GIS analysis6/12/2018 6

7. 1. Qualitative(a heuristic) assessment general steps:
• Preparing casual factor data layer (GIS –
Layer)
• Normalization using internal weighting of the
causal factors
• Generation of weighted normalized data
layers
• External weighting of each criteria-data layer
• Generation of a hazard index,
• Classification of the area
2. Quantitative (a statistical) assessment
general steps:
• Recognizing & collecting of the
causal factors & landslides
• Calculating the statistical parameters
• Determining the weights
• Combination all causal factors in the
statistical model.
• Classifying the area
6/12/2018 7
landslide Hazard zonation procedure cont..
Samuel Molla 2011

8. Satellite/google image,
Topographic map
Field data
Recorded data
Landslide hazard zonation map
Combined Information value/weight of evidence
map
Controlling Factor maps
Information value/weight of evidence map
Data collection
Interpretation & analysis
Primary landslide
distribution map
Landslide distribution
map
Reclassify
Crossing
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General flowchart of statistical analysis(information value/weight
of evidence for LHZ

9. • LHZ general flow chart
for frequency ratio value
model by M Meten et al
2015
6/12/2018 9

10. 5. Landslide hazard in Ethiopia
4
• landslide has been a frequent problem in
Ethiopia spatially in the high land parts of
north, south, western and rift escarpment
valley(Ayele et al.,2014).
• Over 700 landslide sites recorded in
Ethiopia; mostly affecting rural
communities, infrastructures, farm lands,
dwelling houses (KifleWoldearegay,2013).
Earth slide along Jimma-
Agaro road
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11. 6. Landslide type, factors ,distribution and effects in Ethiopia
Landslide type in highland of Ethiopia
• Types of landslides triggered by rainfalls in
the highlands of Ethiopia include:
• debris/earth slides,
• debris/earth flows, and
• rockslides. But
• rock fall& toppling have little
association with rain fall
Kifle Woldearegay(2013)
6/12/2018 11
Along Shire-May Tsebri road
Tarmaber area,
Feresmay area
Jimma area
Mush area (Debreberhan)
Adishu area

12. 7. landslide controlling factors in the highlands of Ethiopia
• Most of the slope failures in the highlands of Ethiopia are
happened because of
• rainfall
• geological (lithological and structural) settings,
• slope shapes,
• slope gradients,
• Drainage lines(stream incisions/gullying) and
• Slope modification, and
• vegetation cover.
6/12/2018 12
• produced by Ayalew
(1999), Woldearegay
et al. (2005), and
Woldearegay (2005).

13. 8. Landslide distribution in high land of Ethiopia
• The following areas are subjected for landslide
hazard because of its complex
geomorphological, hydrological, and
geological setting.
• Desie town, norther highland of
Ethiopia
• Abay Gorge centeral highland of
Ethiopia
• Jima basin central highland of Ethiopia
• Goffa, gilgel gibe II & sodo shone
area(southern Ethiopia )
• Tekeze basin northern Ethiopia
• Paleozoic glacial & post glacial
sediments in Tigray , northern Ethiopia
• Tarmaber & surrounding area in central
highland of Ethiopia
• In different Welo area northern highland
of Ethiopia
• Wondogenet area(southern Ethiopia )
Kifle Woldearegay(2013)
Figure 7. Locations of
landslide-affected
areas in relation to the
rainfall distribution
(mean
annual rainfall in mm)
in Ethiopia.
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14. 9. Landslide effects in the high land of Ethiopia
• landslides in the highlands of Ethiopia indicated that high hazards to economic, social and environmental
significance. E.g.Researcher Magnitude of
damage
Year of
occurrence
Damaged Elements
• L. Ayalew (1999) >100km
>200
>500ha
300
1993 - 1998 • Asphalt road
• Dwelling House demolished
• Lands
• Human lives climbed
• Woldearegay (2005) 135
3500
$ 1.5M US Dollar
1998 - 2003 • human lives have been lost,
• people were displaced and
• an estimated worth property has been damaged
• Ayenew and Barbieri (2005) • landslides in Dessie town have been affecting roads,
buildings, pipe-lines, and other infrastructures in
the town.
• (Woldeaegay, 2008; Atsbeha,
2008; Schmeider et al., 2008)
• >3000
• 1250
• 4
• 4
• over 1500 ha
Landslide in tarmaber
• people were displaced;
• dwelling houses were demolished;
• Churches, Mills, and one elementary school were
destroyed;
• farm land was devastated.
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15. 6/12/2018 15
Bonga-Mizan road
Kifle Woldearegay(2013)
Landslide effects in the high land of Ethiopia

16. 10. Some examples of of landslide hard zonation in different part of Ethiopia
Researcher LHZ/LSZ methods location Identified Factors
Tenalem Ayenew a, Giulio
Barbieri
b(2004)
Semi quantitative
approach
VES
in the city of
Dessie
• Geology ,topography,geomorphology,geothechnical
properties of soil & rocks
• Hydro metrological conditions
• Bekele et al (2009) Review & field
survey
Desie,Tigray,
wondogenet
& Blue Nile
gorge
• geological and hydrological conditions, human
interference , springs and rain fall
Birhanu Erimias 2014 slope stability
susceptibility
evaluation
parameter (SSEP)
route from
Alem ketema
– Ambat
village, north
Shewa
• intrinsic parameters: slope geometry, slope material,
structural discontinuities, land use/ land cover &
groundwater
• external triggering factors : seismicity, rainfall &
manmade activities
• B. Temesgen I**, M. U.
Mohammed’ and T. Korme’
(2001)
GIS environmental
modelling and
statistical approach
Wondogenet Lithology,structure, slope aspect,watercourse,vegetation
biomass
6/12/2018 16

17. • Effects of landslide factor combination on
the landslide prediction accuracy of
landslide susceptible maps in Blue Nile
gorge of central Ethiopia by M Meten et
al 2015.
• Using statistical analysis methods(
frequency ratio value model)
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Some examples of landslide hard zonation in different part of Ethiopia
Meten et al. ,(2015)

18. Some examples of landslide hard zonation in different part of Ethiopia
Slope failures in the Blue Nile basin, as seen
from landscape evolution perspective using
qualitative & quantitative methods6/12/2018 18
Lulseged Ayalew & Hiromitsu Yamagishi (2003)
Yoseph, 2010

19. Some examples of landslide hard zonation in different part of
Ethiopia
• Landslide hazard zonation around the route from
Alem ketema – Ambat village, north Shewa by
Birhanu Erimias 2014
• Using the slope stability susceptibility evaluation
parameter (SSEP)
• Fig 7.12 Landslide Hazard Zonation map of the
study area6/12/2018 19

20. Plate 6.8 Photo
showing
translational
rock slides in the
study area
Plate 6.7 Photo showing
rock slump or rotational
rock slide and rock fall
Plate 6.4 Photo showing
zones (modes) of motion of
rock fall
Some examples cont.…
Plate 6.9 Photo
showing
translational
slide in soil
Birhanu Erimias 2014
6/12/2018 20

21. Some examples cont.…
• Landslide hazard evaluation & zonation in
Kindo Didaye woreda south western Ethiopia
by Zerihun Dawit 2016/2017 un published MSc
thesis.
• using integrated SSEP rating approach and a
raster based information value approach
Figure 5.11. Landslide Hazard Zonation map
prepared by Slope stability Susceptibility
Evaluation
Parameter (SSEP) expert method.
6/12/2018 21

22. (E). Gully cut formed due to
erosion at Offa
Wamura Kebele.
(A) Debris flow in Offa Chew Kare Kebele.
(B) Debris slide along Zala Kare River.
(C) Rotational slide along Kila River.
(D) Debris flow in Offa Wamura
Zerihun Dawit 2016/2017 unpublished MSc thesis
Some examples cont.…
6/12/2018 22

23. Some examples cont.…
• Land slide hazard zonation in Ada Berga
district , central Ethiopia by Fikre et al
(2015)
• Using GIS based statistical approach
• Identified factors are: lithology, soil
deposit, slope, aspect, curvature,
elevation and land use/land cover
Fig 9 landslide hazard zonztion(LHZ) map of study area
6/12/2018 23

24. 9. Conclusion
• Abebe et al. 2010 , Tenalem Ayenew &Giulio Barbieri
2004, concluded that increasing population growth, gravity,
geological & hydrological conditions have great value on
landslide occurrence in the high land of Ethiopia. Eg. Dese
• Most of landslides in Ethiopia have occurred in western,
southern, northern, central and along rift margin of Ethiopia
(Kifle Woldearegay(2013))
• Even though many landslide factors are available, rain fall
& slope modifications are the most triggering factors in the
high land of Ethiopia (Kifle Woldearegay,2013)
• The types of landslides in
Ethiopia because of rain fall
triggering factors are:
• debris/earth slides,
• debris/earth flows, and
• rockslides. But
• rock fall & toppling
have little association
with rain fall
Kifle Woldearegay(2013)
6/12/2018 24

25. 36
C
End of presentation.
•This is all what I have to say.
•Thank you too much for your eyeful
attention!