1
LANDSLIDE TRIGGERING RAINFALL
THRESHOLDS IN EMBOBUT-EMBOLOT
LOCATION ELGEYO-MARAKWET COUNTY
BY
CHESIR JERONO DORCAS
ESS/100/14
A RESEARCH PROJECT SUBMITTED TO THE UNIVERSITY OF
ELDORET, SCHOOL OF ENVIRONMENTAL STUDIES,
DEPARTMENT OF EARTH SCIENCE IN PARTIAL FULFILMENT
OF THE REQUIREMENT FOR THE DEGREE OF
ENVIRONMENTAL STUDIES (SCIENCE)
JULY 2018
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DECLARATION
I declare that this project is my own work and has not been presented for any
degree award in any institution.
Name…………………………………….
Signature…………………………………
Date……………………………………….
Approval by supervisor
I declare that this research has been submitted for examination with my as the
approval official university supervisor.
Name…………………………………
Signature……………………………...
Date………………………..
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DEDICATION
This research study is dedicated to my family members who
supported me during my research period.
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ACKNOWLEDGEMENT
I wish to register my great appreciation to the Almighty God
For His unfailing love, care and guidance throughout the project
undertaking, it can never be possible without Him.
Secondly, I highly recognise the valuable input of my supervisor, Prof
Ucakuwun as well as his cordial and unremitting support. Special
tanks go to the course coordinator, Ms Keli for her enthusiastic
guidance and top of range ideas that saw the successful completion of
this project.
I owe my sincere gratitude to the metrological department county
government of Elgeiyo Marakwet County for the ready willingness to
avail technical reports on landslides and rainfall distribution data
which were paramount in these project.
Last but not least, I thankfully register my overwhelming appreciation
to my dear family and friends for their immense moral and financial
support, it would not have been easy without you. God bless you all.
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ABSTRACT
Landslides are a group name for several types of mass movement of
rock and debris down a slope or a mountain .There are several types
of landslides which include slump, debris, slide, debris fall or a
rockslide. The research paper analysed rainfall thresholds that trigger
landslides in embobut-embolot location,Elgeyo Marakwet County.
Reconnaissance survey was conducted on the study area to
understand various socio-economic activities that are linked to
landslides ,Secondary data was also used to gather information on
rainfall data and landslide data from meteorological department to
facilitate the analysis of the trend for the study. The geology and soil
characteristics that are also linked to landslides in the study area were
obtained from the literature.
From the analysis done the research study found that continuous
heavy rainfall received from the months of April to July and October
to December were the main trigger of landslides event in the study
area, because of over saturation of the soil making the ground
unstable to withstand massive flow of debris from the hilly parts of
the study area, causing landslides that have continued to cause loss of
human lives ,livestock, property and land along the Elgeyo Marakwet
escarpments.
The study therefore makes recommendation that new method of
landslide assessment be used such as rainfall thresholds in prediction
of landslides in order to provide early warning to the people living in
landslide prone areas.
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Table of Contents
DECLARATION..................................................................................3
DEDICATION......................................................................................4
ACKNOWLEDGEMENT....................................................................5
ABSTRACT.........................................................................................6
CHAPTER ONE...................................................................................9
1.1INTRODUCTION...........................................................................9
1.2 Statement of the problem..............................................................10
1.3OBJECTIVES................................................................................11
1.3.1General objective.....................................................................11
1.3.2 Specific objectives..................................................................11
1.4 Research Questions.......................................................................11
1.5 Hypothesis....................................................................................12
1.6Justification of the study................................................................12
1.7 The study Area.............................................................................12
1.8 LANDSLIDES IN ELGEIYO MARAKWET.............................13
Table 1 : Major landslides in Elgeiyo Marakwet County.............14
1.9 MAP OF STUDY AREA.............................................................16
CHAPTER TWO LITERATURE REVIEW.....................................17
2.0 Introduction..................................................................................17
2.2Factors that trigger landslides........................................................18
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2.2.1Rainfall.....................................................................................18
2.2. 2 Influence of soil characteristics.............................................19
2.2.3 Vegetation and land use..........................................................20
CHAPTER THREE: METHODOLOGY...........................................21
3.1 Sources of data..............................................................................21
3.1.1Primary data.............................................................................21
3.1.2 Secondary data........................................................................21
3.1.3 Research design......................................................................21
3.1.4 Data analysis...........................................................................22
CHAPTER 4 RESULTS.....................................................................23
4.1 GEOLOGY...................................................................................23
4.2 SOILS...........................................................................................24
4.3 SOCIO-ECONOMIC ACTIVITIES.............................................24
4.4 RAINFALL..................................................................................24
Table 2: Rainfall distribution for Embobut-Embolot location......24
Table 3: Landslide occurrence in the years 2010 -2013 for
different villages in the study area................................................26
CHAPTER 5: DISCUSSION.............................................................29
CHAPTER 6: CONCLUSION...........................................................30
6.1 RECOMMENDATIONS.............................................................31
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CHAPTER ONE
1.1INTRODUCTION
Landslides are complex natural phenomenon that constitute a serious
natural hazard in many countries (Brabb and Harrod,1989).Landslides
belong to a group of processes referred to as mass wasting these
includes a variety of slope movements such as falls,
slides ,solifluction ,flows and creep. Types of landslides includes
deep-seated slides, rock slides, debris slides,etc.(varnes 1978:pierson
and costa, 1987 ,Hutchison 1988, cruden and varnes 1996,Hunger et
al ,2001).Landslides occurrence have continued to increase in the last
few years in several parts of mountainous Kenya .These areas include
Aberdare Range ,Mount Kenya ,Mount Elgon,Nandi escarpment, and
cherang`any hills , the area of this study. These landslides have both
social and economic impacts which are mainly loss of life,
agricultural land, crops and infrastructure (Kigomo and Mburu, 2009).
Landslide risk in Kenya is studied and assessed in relation to geology,
soil type, rainfall density and slope gradient. Areas identified as being
most affected include the Rift Valley escarpment with deep nitisol
soil and high to moderate mean rainfall attracting large human
population in these areas who then alter the land cover (Davies and
Nyambok, 1993)
During the rainy season, various parts of the eastern slopes of the
cherang`any hills witness heavy landslides especially as seen in the
last twenty years. One such area greatly affected is Embobut-Embolot
location, Elgeiyo Marakwet County .Often those affected are left to
their own devices when this disaster strikes. There is no long term
solution that has been proposed for those affected by this natural
hazard and disaster .This hazard causes untold misery and poverty
when those affected lose their shelter, food crops, and livestock to the
landslide problem.
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The population of the study area increased from 23,000 to 32,000
between the year 1999 and 2009 population census, increasing the
density from 125 to 175 people per km 2 (GOK,2011).This shows that
population pressure on the use of land has increased with loss of
previous vegetation cover leaving behind bare ground of
agriculturally cultivated land. These changing land use and land cover
patterns is one of the socio-economic activity practised by the
residence of the study area that increase the cases of landslides.
There is very little research work on landslides in Embobut and
Embolot location and therefore this study is intended to contribute to
bridging of the research gap. This study thus aims to improve our
understanding on the rainfall thresholds that trigger landslides on the
escarpment areas of Embobut and Embolot location .The study
intended to analyse rainfall thresholds that trigger the occurrence of
landslides and to evaluate whether landslides triggering rainfall
thresholds as linked to geology soils and social economic activities in
the study area and also to evaluate rainfall events which are connected
to landslides against those that are not linked to landslides .
1.2 Statement of the problem
Landslides impact negatively on the socio-economic development of
the affected inhabitants in various ways. Farmers face challenges
regarding sustainable food production in the context of uncertain
conditions and disasters. Landslides among other disasters such as
droughts, pests, and diseases have a tendency to reduce crop and
animal productivity. In Embobut-Embolot location it’s important for
farmers to be equipped with knowledge about the rainfall amounts
that cause landslides in order to enable them get to a safer grounds.
Local knowledge can reveal insights in resource and ecosystem
management (Berkes and Folke 1998, Scott 1998).Such insights can
be used to develop policies and community awareness programme to
provide early warning systems to the residence of the study area.
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Disasters such as landslides have a tendency to stifle economic
growth by diverting resources from productive sectors to relief
rehabilitation. Landslides destroy homes, homesteads and social and
physical infrastructures in the affected areas. As a result of landslides
occurrences in the society`s assets are destroyed, their ways of life are
affected and poverty becomes sustained .The local communities are
very vulnerable to landslides denoting that they do not have adequate
means or ability to protect themselves against the adverse impacts of
landslides. To deal with the impact of landslides is to alleviate
poverty and put the country on a sustainable development path. Thus
the present study highlights the factors that trigger landslides and
suggest a policy direction that should be employed to resolve the
devastation caused.
1.3OBJECTIVES
1.3.1General objective
To analyse rainfall thresholds that trigger slope failures in the study
area.
1.3.2 Specific objectives
a .To study landslides events that are triggered by rainfall in the study
area.
b.To evaluate rainfall events which are connected to landslides
against those that are not linked to landslides.
c. To evaluate whether landslide triggering rainfall thresholds linked
to geology, soils, and social economic activities in the study area
1.4 Research Questions
a.Which landslide events in the past are triggered by precipitation in
the study area?
b.Which rainfall events and precipitation levels have triggered in the
area`s landslide history?
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c.Are geology, soils ,social economic activities advancing landslide
even in the area?
1.5 Hypothesis
Landslides are triggered by specific rainfall thresholds
1.6Justification of the study
Landslides are very common disasters in Elgeiyo Marakwet and other
mountainous areas in Kenya. The devastation and loss of lives have
been well documented but not investigated and resources
inadequately allocated to reduce the risk. The agricultural sector in
Kenya is under intense pressure to produce more food to feed the
rapidly growing human population, produce adequate raw materials
for the agro industries and export to earn foreign exchange. This ,
coupled with the effects of human settlement ,has led to land
degradation making some regions more vulnerable to landslides .No
further land should be allowed to be wasted through landslide
disasters. In Embobut-Embolot location, most farmers depend on rain
fed mixed farming that is dominated by traditional technologies .The
area is prone to rainfall triggered landslides, which have led to loss of
life and damage to property. Thus the study analysed the rainfall
thresholds that trigger landslides in order to provide early warning
system to the people of the study area.
1.7 The study Area
Embobut-Embolot location is an area within Tirap Division of
Elgeiyo Marakwet County, in North Rift region of Kenya .This area
is located on the eastern slopes of Cherang`any hills along the
Marakwet escarpment .It extends from 1 o05 ` N, 35o32`E to 1 0 17` N 35 36`
E.
It is an area that lies on the mid slopes of the escarpment at altitude
range of between 1600m to 2700m above sea level. The two locations
of Embobut and Embolot which experience intense occurrence of
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landslides during the two rainy seasons of between March and July
and October to December were of specific interest. The two locations
have experienced a lot of landslides due to various factors such as
geology, Soil and also the topography of the area. The marakwet
escarpment is quite steep with most areas having gradients more than
30 degrees. Some sections are sheer cliffs a22` and scarps. Tirap
division borders west Pokot County to
The north Kapyego Division to the West Tot division to the East and
Kapsowar Division to the south.
1.8 LANDSLIDES IN ELGEIYO MARAKWET
Landslides are commonly occurring natural hazard in Elgeiyo
Marakwet County. It occurs mainly along the steep areas of Elgeiyo-
Marakwet escarpment. This physical feature extends in north-south
direction as a narrow band of less than 5km in width, from the
southern tip of the county at molol and kocholwo area all the way to
the north at Mungw`o village, Embobut location ,a length of about
140km .
Every year during the onset of long and short rains, the inhabitants of
these areas brace themselves for a spate of landslides of varying sizes
and magnitudes of destruction. Once in while during periods of
prolonged, heavy rains, a massive landslide occurs that costs human
lives and property loss.
One of the earliest notable landslides in, Elgeiyo Marakwet County
the Kamoi landslide occurred in 1961, in Embobut location. It
occurred after a period of an unusual prolonged heavy rainfall during
the months of July to December of this particular year.
However it is in the last ten years that the intensity and frequency of
the occurrence of these landslides have tremendously increased .many
numerous small landslides that do not cause any harm or much loss of
land often go neither unnoticed nor reported. It is only when a larger
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landslide that costs human life and livestock occurs, does the rest of
the country gets know.In the long rains of april ,2010 a massive
landslide composed of rock and mud slide down the marakwet
escarpment at kitony village of kaben location, Tot division .This
landslide buried ten people intheir houses as they slept.it also swept
several livestock besides destroying hundreds of
bananas,mango,pawpaw and citrus fruits in adjacent farms.
On the night of December 29,2012, 11 peopledied and 25 families
were displaced when a landslide buried seven villages in southern
division of the county.Five people died at kapechei location ,four at
kaptarakwa area and two at rokocho village after a heavy downpour
that lasted two days nonstop.
Table 1 : Major landslides in Elgeiyo Marakwet County
Location of Year of Cause or Effects
event occurrence trigger
Kamoi 1962 Heavy Loss of over 100ha of gracing land
village ,Embo rainfall within kamoi village.No loss of life
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but location throughout was reported because peoplehad
marakwet east the week the time to move to a safer ground
constituency /month of
July
Kakisoo 2010,April Heavy 11 people died ,loss of 100 mangoes
village kaben overnight ,banana grove farmland
location, rainfall
marakwet
east
constituency
Keiyo south December Prolonged Loss of over 30 lives within
constituency to January short kapechei,kocholwo,rokocho,and
2012/2013 rains ,heavy molol villages of keiyo south
overnight constituencies
rainfall
Wewo 2013 at Heavy Loss of land and livestock
landslide wewo overnight
village rainfall
Katilit major 2011 Heavy Loss of land and houses destroyed
landslide overnight
rainfall
Kamoi 2010 Heavy Destruction of house and injury to
landslide overnight household members
rainfall
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1.9 MAP OF STUDY AREA
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CHAPTER TWO LITERATURE REVIEW
2.0 Introduction
Landslides are not a new phenomenon in Africa. The have been
reported in various countries including Cameroon, Kenya, Uganda,
Rwanda,Tanzania,and Ethiopia (Moeyerson
1988;1989a;1989b;Davies;1996 Westerberg and Christianson,
1998;Ngecu and Mathu 1999 ;Inganga and Ucakuwun
2001,Muwangaet al.2001;knapen et al. 2006). The East African
region which includes Malawi, is a heterogeneous in terms of
physiography, geomorphology and rainfall, and has a high
susceptibility to slope movement .In every slope there are forces
which tend to promote down slope movement and opposing forces
which tend to resist movement. A stable slope the down slope shear
stress is delicately balanced by the shear strength of the soil. Where
this balance is upset and any form of trigger mechanism occurs, slope
failure will occur. The overall call of the present study is to analyse
rainfall thresholds that trigger landslides and to look for measures that
the local communities use to cope with the landslide disaster. The
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high annual rainfall received, land cover changes experienced in the
area of study, soil type characteristics, are some of the factors that
trigger landslide.
2.2Factors that trigger landslides
2.2.1Rainfall
Landslide problem has been little researched on in Kenya and there is
lack of information on rainfall threshold, nature of occurrence and its
characteristics .Extra ordinary heavy rainfall between May 1997 and
February 1998 due to the El Nino weather phenomena caused major
landslides in Kenya (Ngecu and Mathu, 1999).In the year 1999
landslide hazard occurred in most parts of embobut and embolot
location and destroyed a lot of property as well as loss of agricultural
land.
Flow like landslides triggered by rainfall occur in most mountainous
landscape of the world .(version ,2000).they pose significant natural
hazards and have a high damaged potential (Brenner ,2003).there are
many statistically meaningful analyses that have been published to
demonstrate threshold value of rainfall and landslide triggering (Caine
1998; Glade et al, 2000: Wieczoreket al ,2000 Mikos, Cetina and
Brilly 2004; Shakoor and Smithmyer 2005 )
Water exerts a considerable influence on cohesion, strength and
viscosity of soil materials and hence a powerful influence on slope
stability .Crozier (1986) argues that low pressures cells particularly
tropical cyclones are the major source of landslide –triggering
rainstorms –because of their intensity. When the rain water reaches
the ground it starts to infiltrate, pore water pressure rises and because
of loss of cohesion of solid particles, their weight may be supported
by pore water. The slope stability is endangered .a sudden rise of pore
water pressure can be so great that the overburden of the soil and
water effectively floats on the pore water beneath and the pore water
will burst out of the voids. Such a burst will trigger slope failure. Pore
water pressure may also rise if the ground
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2.2. 2 Influence of soil characteristics
soil is a complex of fine rock fragments and organic matter serving as
medium for plant growth, and differentiated from its parent material
by actions of various genetic and environmental influences (Muller
and oberlander ,1974) soils are products of geology and
climate .Through the processes of weathering ,translocation and
organic activity ,soil characteristics especially soil profile is
developed. The depth of soil depicts a balance between soil forming
processes and soil erosion .Soil profile controls the tolerance of slopes
to all other destabilizing factors. Crozier (1986) emphasizes that
inclination and orientation of structural surface have the greatest
effect on stability of slopes.
Soil characteristics include texture, structure, chemistry and
colour .soil texture determines the ability to absorb and store water,
generally referred to liquefaction .Liquefaction is defined as a
condition when the soil momentarily liquefies and tends to behave as
a dense liquid a condition which is required for landslides to occur.
The most important textures that control liquefaction are sands and
silts or combinations of both .Sand and silts or combinations are fine
enough to inhibit rapid internal water movement , and coarse enough
to inhibit rapid capillary action , while simultaneously displaying
little cohesion. The variation of soil in stability in different
environment with similar slope properties reflects the variable
characteristics of soils for example soil developed through weathering
of volcanic ash , andosols are known to be sensitive to landslides
(kipsanai, j. A 1986) .soils such as silt and clay are weaker and
commonly have complex (colloids) or multiple planes of weakness
(clay –humus complex) which enhance the occurrence of landslides.
Soils with high clay content are known to swell when wet and shrink
in dry weather and the swelling capacity increases with increasing
surface area of the exchangeable caption’s (krhoda, 2013)
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2.2.3 Vegetation and land use
The importance of vegetation and land cover on the hydrological
cycle is fairly well known .The vegetation and any other land cover
characteristics determine the rate of rainfall infiltration into the
ground, evapotranspiration and help in binding soil particles together
and hence have some effect on stability of slope. On the other hand
the roots system of plants absorbs soil moisture and expires it to the
atmosphere and lowers the water table .deforestation therefore has a
negative impact on infiltration capacity and soil development it is
however not known whether deforestation will contribute to severe
landsides .After clearing of vegetation the sources of soil humus and
the role of tree roots will be eliminated. Deforested areas also
experience wide variations in temperature and moisture contents thus
causing heavy cracking of soils .Landslides are hence commonly
attributed to the loss of support from a root system and deforested
areas (Temple and Rapp, 1972). In many cases slope failures are
triggered as a result of undercutting of slope by a river especially
during a flood .This undercutting serves both to increase the gradient
of the slope, and to remove toe weighting, which decreases
stability .For example in Nepal this process is often seen after a
glacial lake outbursts flood, when toe erosion occurs along the
channel .Immediately after the passage of flood waves extensive
landslides often occur. This instability can continue to occur for a
long time afterwards especially during subsequent periods of heavy
rain and floods events .The proportions of landslide susceptible areas
are localized in steep headwater valleys , particularly at the heads of
the channel network (Montgomery and Dietrich 1994 )
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CHAPTER THREE: METHODOLOGY
3.1 Sources of data
3.1.1Primary data
Primary data gathered for the study involved carrying a
reconnaissance survey in order to study the socio-economical
activities of the study area in order to evaluate if they are linked to
landslides occurring in the area of study.
3.1.2 Secondary data
Data of major landslides that had occurred in the study area and
rainfall data was obtained from meterological department in iten
elgeiyo marakwet county headquarters .Information containing the
geology and soils of the study area was obtained from studying
various literature of the study area.
3.1.3 Research design
A research design is an arrangement of conditions for the collection
and analysis of data in a format that combines their relationship with
the purpose of the study to the economy of the procedures
(chandran ,2004). It works as the master plan for the collection and
analysis of data that aids in the answering of the research questions.
Cooper and schindler (2003)states that a research design ensure that
the study is relevant and applicable to the problem and its economical
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procedures for acquiring the information . This research adopted
descriptive study design . Reconnaissance survey was carried in the
study area . From the survey carried other factors such as the socio –
economic activities , geology and soils of the study region that are
associated with occurrence of landslides in the area of study were
studied.
3.1.4 Data analysis
Qualitative and quantitative data analysis techniques have been used o
facilitate interpretation of data .Both secondary as well as primary
data were collected and analysed .The secondary data was gathered
from reports this data included rainfall data and landslides from
meteorological department .primary data on the hand were obtained
by carrying a reconnaissance survey in order to understand the socio-
economical activities of the study area that area linked to trigger
landslides.
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CHAPTER 4 RESULTS
The chapter presents the data and its analysis .The specific objectives
of the study were to evaluate rainfall events that are linked to
landslides and thus not linked to landslides ,to evaluate whether
landslides triggers rainfall thresholds as linked to geology, soils and
socio-economic activities in the study area ,to study landslide events
that are triggered by rainfall in the study area ,apart from rainfall
some other factors such as soils, geology and socio-economical
activities were found to trigger landslides in presence of heavy
rainfall.
4.1 GEOLOGY
The dominant rock in along the escarpment in the study area is
pyroclastic and igneous rock. Pyroclastic deposits consist of
pyroclasts which are not cemented together. They are broken where
the volcanic material has been transported and reworked through
mechanical action such as by wind or water. One of the most
spectacular forms of pyroclastic deposit is the Ignimbrites deposits
formed by the high temperature, gas and ash mix or a pyroclastic flow
event (Blatt & robbery ,1996)
Igneous rock is one of the volcanic rock materials which have same
characteristics with the pyroclastic rock. The belt in which the two
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types of rocks lie is on high susceptibility to landslides making it a
major factor that triggers a landslide event in the study area.
4.2 SOILS
Kaolinite soil is the major type covering the study area along the
escarpments .It is a clay mineral, it has low shrink-swell capacity and
low caption exchange capacity, it is a soft earthly, usually white
mineral produced by the weathering of rocks in hot moist climates
(Balt and Robbert,1996) with the presence rainfall .This soil type are
easily susceptible to landslides in the study area.
4.3 SOCIO-ECONOMIC ACTIVITIES
Deforestation ,cultivation, cattle rearing ,road construction activities
are the major human activities which are carried out in the area of
study ,thus establishing the ground surface which for instance
escarpment or slopes are already fragile ,chances or landslides in the
type of area is high especially when there is rainfall as triggering
factor.
4.4 RAINFALL
Rainfall is the main triggering factor to landslides since heavy
downpour or the rainfall intensity relate to geology, soil and socio-
economic activities in relation to landslide occurrence .The most
precarious period of the year for the people of Embobut-Embolot is
during the period of heavy rainfall especially during the months of
April, May and July ,where monthly precipitation is high .
The table below shows rainfall data for the Years 2010-2015 for
Embobut and Embolot location
Table 2: Rainfall distribution for Embobut-Embolot location
MONTH 2010 2011 2012 2013 2014 2015
January 21.6 9.4 50.6 26.2 76.1 129.4
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February 25.8 0.0 0.0 26.0 10.1 5.3
March 99.5 18.0 13.0 0.0 55.2 12.7
April 42.5 69.2 18.1 67.1 34.2 3.1
May 173.4 35.2 159.8 186.7 21.8 122.0
June 216.8 87.9 217.2 66.9 44.5 78.6
July 83.8 65.3 105.9 94.7 55.7 102.8
August 146.2 125.0 58.4 48.7 78.4 90.4
Septembe 88.9 122.1 125.0 128.7 147.9 43.4
r
October 66.1 87.1 65.2 88.3 81.8 31.5
November 123.8 71.6 47.0 87.6 143.4 105.0
December 53.6 127.8 42.6 8.7 44.2 106.8
Totals 1242 890.2 702.8 829.6 793.3 831
Minimum 21.6 9.4 13.0 8.7 10.1 3.10
Maximum 216.4 127.8 159.8 128.7 147.9 129.4
Average 103.5 74.18 75.23 69.13 66.11 69.25
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Table 3: Landslide occurrence in the years 2010 -2013 for
different villages in the study area.
Village Year Month Monthly Cause
Rainfall
recorded
that resulted
to landslides
Kaben 2010 April 142.5 Heavy
Location rainfall
Kamoi 2010 April 142.5 Heavy
rainfall
Katilit 2011 December 127.8 Heavy
Major overnight
Landslide rainfall
Wewo 2012 July 105.9 Heavy
rainfall
Wewo 2103 May 186.7 Prolonged
short rains
Heavy
overnight
rainfall
Occurrences of landslides in the study area is due to continuous
rainfall that is received in a Month or from the previous Months :For
example the landslide that occurred in Kaben Village in the Month of
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April, is due to heavy rains from March thus making the soils more
saturated hence causing landslides.
From the analysis done on the rainfall data and landslide occurrence
in Embobut-Embolot location .it is realised that the main cause of
landslide is heavy rainfall, especially during the Months of
April ,May and July, where Monthly rainfall recorded is very high.
During the Months of January and February possibility of landslide
occurring is low. This is due to low Monthly rainfall recorded as
shown in the table above.
27
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CHAPTER 5: DISCUSSION
There are various factors that influence the occurrence of landslides
such as geology, rainfall, soils and socio-economic activities amongst
others. The role of these factors is analogous in the area of study and
especially to the landslide prone sites. Landslides for instance are
prevalent in andosols and nitosols, soils that cover the highlands of
the study area thus easily susceptible to landslides, rainfall is the
major trigger of landslides in both locations Embobut and Embolot
which favours deep weathering as well as steep slopes.
By analysing the rainfall data set collected from meteorological
department, in Iten, Elgeyo Marakwet County. It was realised that
high intense rainfall and heavy amounts of rainfall in the Elgeyo
Marakwet escarpment is the main trigger of landslides in Embobut-
Embolot location. According to inversion (2003) flow –like landslides
triggered by rainfall occur in most mountainous landscape of the
world. There are many statistically meaningful analysis that have been
published to demonstrate threshold value of rainfall and landslide
triggering. These flow-like landslides pose significant natural hazards
and have a high damaged potential. The rainfall amounts located for
two locations that are triggered landslides were recorded at 142.5mm
in the Month of April, 2010,159mm in May 2012 that caused
landslides in the study area.
The wettest Months are April, May and July with heavy rainfall,
while the driest Months are January and February hence occurrence of
landslides is very minimal due to low rainfall amounts recorded.
Despite the fact that rainfall is known to be the main trigger of
landslide in the study area .Inadequate efforts have been used given
towards to rainfall thresholds which have been used worldwide with
enormous success. However, the intensity duration method is not
applicable in Kenya due to data limitations (hourly rainfall data and
historical landslide data) thus leading to inadequate information
issued to the residents in the landslide prone areas towards the
occurrence of landslide.
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Rainfall data and daily sediment leads from a catchment are used to
explore the effects of rainfall and hill slope characteristics .On
initiation of landslide through analysis it has been discovered that two
distinct rainfall amount, a seasonal accumulation threshold and daily
rainfall threshold must be exceeded before landslide are triggered. To
understand better which rainfall amounts result into landslides,
occurrence table was drawn from different Villages in the study area
and Monthly rainfall that resulted into landslides was
recorded .Results from the table shows that high rainfall received in
the area triggers landslides while low rainfall received does not
destabilizes the ground.
CHAPTER 6: CONCLUSION
From the results of the study, it is concluded that landslides occur in
all parts of Embobut-Embolot locations .The landslides occurring in
the region vary in size from tiny inconsequential types to massive
mass wasting landslides sweeping entire hillsides and causing
massive destruction to the environment loss of human life and
property. Heavy rainfall which falls in huge quantifies in Embobut
and Embolot location in M month of April to July and October to
December averaging 1400mm annually acts as triggering element. It
can thus be said that these landslides occurring are not only as a
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result of one cause but combination of several triggering factors such
as geology of the study area, soil, socio-economic activities and
rainfall as the main triggering factors.
There is a little intervention by disaster relief agencies in terms of
response in time of landslide disaster rescue operations .Therefore the
use of rainfall thresholds in prediction of landslides will go a long
way in advancing landslide research and provision of early warning to
residents living in landslide prone areas.
6.1 RECOMMENDATIONS
Landslide research and assessment in Embobut-Embolot
locations ,Elgeyo Marakwet County have lagged behind ,thus new
methods of landslide assessment have been recommended that is use
of rainfall thresholds in prediction of landslides .Since the intensity
duration method is not currently applicable in Kenya due to data
limitations (Heavy rainfall data and historical landslide
data).Implementation of relevant instruments such as pluviometer is
recommended to ensure an improved landslide data
storage ,implementation and analysis.
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