TITLE PAGE

TOPIC:FLOOD DISASTERS AND THEIR EFFECTS IN NGWO, UDI LOCAL

GOVERNMENT AREA ENUGU STATE

A DISSERTATIONSUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTERS OF SCIENCE (M.Sc) DEGREE IN DISASTER

RISK MANAGEMENT

BY

MBAH, CHINASA LOVE EDITHPG/ M.Sc/10/55076

CENTRE FOR ENVIRONMENTAL MANAGEMENT AND CONTROL

SCHOOL OF POSTGRADUATE STUDIES UNIVERSITY OF NIGERIA, ENUGU CAMPUS

SUPERVISOR: DR. OGBOI K. C.

JUNE, 2015

i

APPROVAL PAGE

This dissertation is certified by the undersigned as the original work carried out by

Mbah Chinasa Love, a post graduate student of the centre for Environmental

Management and Control, School of Post graduate studies, University of Nigeria,

Enugu Campus.

………………………………..MBAH CHINASA LOVE(STUDENT)

.................................................... .......................................PROF. MADU C.N. DR. OGBOI K. C. (DIRECTOR) (PROJECT SUPERVISOR)

……………………………..PROF. E.O. IGUISI(EXTERNAL EXAMINER)

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DEDICATION

This project is fully dedicated to my late beloved daughter, Mmesomachukwu Mbah,

whose love in my heart is indelible.

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ACKOWLEDGEMENT

My sincere gratitude goes to Lord God Almighty who is the qualifier of the

unqualified. To God alone be all the glory for his mercy that has seen me through this

programme.

I appreciate my dear husband, Mr. William Alum Mbah for his wonderful supports

and care. I also acknowledge my boss, Hon. Joe C. Offor and for his support and

kindness throughout the period of this programme. And to my supervisor, Dr. K. C.

Ogboi, I say thank you for being able to make out time to read and correct my work

and also for tolerating every stress I must have caused him.

My appreciation goes to all who gave me support in one way or the other that I

cannot mention one by one.

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TABLE OF CONTENTS

Title Page......................................................................................................................i

Approval Page.............................................................................................................ii

Dedication...................................................................................................................iii

Acknowledgement......................................................................................................iv

Table of Contents........................................................................................................v

List of Tables..............................................................................................................ix

List of Figures.............................................................................................................x

Abstract......................................................................................................................xi

CHAPTER ONE: INTRODUCTION

1.1 Background of the Study:.......................................................................1

1.2 Statement of the Problem:......................................................................5

1.3 Aim and Objectives of the study.......................................................................6

1.4 Research Questions:...............................................................................6

1.5 Research Hypotheses.........................................................................................7

1.6 Scope of the Study.................................................................................7

1.7 Significance of Study.............................................................................7

1.8 Limitations of the Study..........................................................................8

1.9 Definition of Terms …………………………………………………………...8

CHAPTER TWO: THEORETICAL FRAMEWORK

2.1 Geophysical Theory.................................................................................10

2.2 The Hydro – Plate Theory: The Great Flood...............................................10

2.3 Ancient Flood Theory..............................................................................11

2.4 Evidence and Theories of a Great Flood:....................................................12

2.5 The Concept of Environment And Sustainable Development........................14

2.6 Environmental Protection ........................................................................15

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CHAPTER THREE: LITERATURE REVIEW

3.1 Introduction ...........................................................................................17

3.2 Facts about Flooding................................................................................21

3.3 Economic and Health Effects of Flood on Building.....................................22

3.4 Factor about Flooding..............................................................................26

3.5 Flood Prevention and Control ..................................................................28

3.6 Computer Modeling.................................................................................30

3.7 Factors Affecting Flood...........................................................................31

3.8 Flood and climate Change ...............................................................................32

3.9 Flood and Remote sensing .......................................................................35

3.10 Floodplains ...........................................................................................36

3.11 Land surface characteristics related to floods .............................................37

3.12 Frequency of flooding ............................................................................37

3.13 Types of flooding: ..................................................................................38

3.14 Causative factors of flooding ...................................................................41

3.15 Literature Gaps.......................................................................................43

CHAPTER FOUR: THE STUDY AREA

4.1 Geographical:.........................................................................................44

4.2 Villages in Ngwo...................................................................................44

4.3 Physical Features:...................................................................................47

4.3.1 Soil ………………………………………………………………………..…..48

4.3.2 The Drainage …………………………………………………………..……48

4.3.3 Topography …………………………………………………………………48

4.4 History..................................................................................................49

4.5 Settlement Pattern.................................................................................49

4.6 Culture.................................................................................................50

4.7 Traditional Administration......................................................................50

4.8 Population............................................................................................50

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4.9 Economic Activities..............................................................................51

CHAPTER FIVE: METHODS AND PROCEDURE

5.1 Types and Sources of Data......................................................................52

5.1.1 Secondary Source..................................................................................52

5.1.2 Primary Data ………………………………………………………………54

5.1.2.1 GPS and GIS Data …………………………………………………………..54

5.1.2.2 Interviews …………………………………………………………………...55

5.1.2.3 Field Observation ……………………………………………………….….55

5.1.2.4 Questionnaire Method …………………………………………………..…..56

5.2 Material Software ……………………………………………………………56

5.3 GIS Criteria to Detect the Areas Prone to Flood ......................................56

5.4 Primary Source ................................................................................................57

5.5 Survey ……………………………………………………………………..57

5.6 Sample Population and Sample Size…………………………………….…58

5.7 Sampling Technique ........................................................................................62

5.8 Description of Instruments for Data Collection (Questionnaire) II. .............62

5.9 Description of statistics used in the analysis..............................................65

5.10 Reliability of Instrument........................................................................65

CHAPTER SIX: DATA PRESENTATION, ANALYSIS AND DISCUSSION

OF FINDINGS

6.1 Land Use and Land Cover Classification........................................................70

6.2 Shuttle Radar Topography Mission................................................................70

6.3 Major Flood Criteria........................................................................................78

6.4 Minor Flood Criteria........................................................................................79

6.5 Social Survey...................................................................................................84

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CHAPTER SEVEN: CONCLUSION AND RECOMMENDATIONS

7.1 Summary of Findings….............................................................................107

7.2 Recommendations..........................................................................................108

7.3 Conclusion .....................................................................................................109

References

Appendix

viii

LIST OF TABLES

Table 5.1: Arrangement of Strata..........................................................................59

Table 5.2: distribution of sample size by Ratio……................................................59

Table 5.3: Communities in the selected villages ………………………………........60

Table 5.4: Distribution of sample size in the villages according to communities ..61

Table 6.1: Land use land cover classification scheme of Ngwo...............................70

Table 6.2: Demographic characteristics of the respondents.......................................84

Table 6.3: Frequency of occurrence..........................................................................85

Table 6.4: Type of property lost in floods.................................................................. 86

Table 6.5: Types of property lost in flood................................................................88

Table 6.6: Causes of flood in the community..........................................................88

Table 6.7: Predominant occupation in Ngwo............................................................90

Table 6.8: Measures to check flooding......................................................................91

Table 6.9: Measures adopted to cope after the flood..................................................92

Table 6.10 Impacts of flooding in Ngwo communities ……………………..……..93

Hypothesis 1: ..............................................................................................................96

Hypothesis 2 ...............................................................................................................97

Duncan Multiple Postho Comparison: .......................................................................98

Hypothesis 3: ..............................................................................................................99

KMO and Bartlett’s Test ..........................................................................................100

Commonalties......................................................................................................... 100

Total Variance Explained .........................................................................................102

Rotated Component Matrix ......................................................................................105

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LIST OF FIGURES

Figure 4.1: Map of Nigeria showing Enugu State...................................................45

Figure 4.2: Map of Enugu State showing Udi L.G.A...............................................46

Figure 4. 3: Map of Ngwo showing the study areas ................................................47

Figure 5.1: Method Flow Chart...................................................................................53

Figure 6.1 Landsat satellite image Map of Ngwo.......................................................71

Figure 6.2: Landuse Land cover map of Ngwo...........................................................72

Figure 6.3: Shuttle Radar Topgraphy Mission............................................................73

Figure 6.4: Hydrological map of Ngwo showing the drainage areas..........................74

Figure 6.5: Hydrological map of Ngwo showing catchment areas.............................75

Figure 6.6: Hydrological map of Ngwo showing slope rank......................................76

Figure 6.7 Schematic diagrams showing the consequences of

flooding water quality......................................................................

Figure 6.8: Map of Ngwo showing major flood areas...............................................79

Figure 6.9. Areas prone to minor flood in Ngwo......................................................80

Figure 6.10. Areas prone to flash flood in Ngwo......................................................81

Figure 6.11:The flash, minor and major floods areas in Ngwo..................................83

Figure 6.12: Occurrence of flood................................................................................85

Figure 6.13: Loss of property as a result of flooding..................................................86

Figure 6.14: Lost of human life as result of flood in your community.......................87

Figure 6.15: Effects of flood on business activities in Ngwo communities................89

Figure 6.16: Extent water covers the areas during flood.............................................90

Figure 6.17: Effects of flood on sources of water supply..........................................91

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ABSTRACT

The flash flood event of July to August 2010 in Ngwo submerged many buildings, farmlands, business premises and economic trees. Flash floods are common in Ngwo, Udi Local Government Area as any other parts of Nigeria. The regular re-occurrence of flood in the area has also been detrimental to the health of the residents of Ngwo. Therefore, the study aims at examining the effects of flooding on the communities of Ngwo. Data were collected through the use of Handheld Global Positioning System (GSP),Geographic Information System (GIS) and questionnaire. GPS coordinates of Ngwo was collected to determine the topography, the landuse landcover, hydrological map (to identify the areas most prone to flooding) and the slope and soil type. The extent of flood inundation was determined through the use of GIS, SRTM(Shuttle Radar Topography Mission) , Digital Elevation Model ( DEM), Illwis and GPS. Coordinates and other data acquired during the field works at Ngwo were used to identify areas most prone to flood, flood plain and the areas impacted most during flood disaster. Using Illwis data, the digital elevation model of Ngwo was generated in ArcGIS. Land use classes were derived from visual image interpretation of Google earth images using the Multi-Resolution Land Cover classification (MRLC) system and handheld GPS. A total of 400 questionnaires were administered to the respondents in the study area. The questionnaires were distributed using the systematic random technique at interval of five communities in each ten villages. Data collated through questionnaire was coded and analyzed with the aid of statistical package for social sciences (SPSS) version 20. Descriptive statistics which includes frequency, percentages, means and standard deviations were used to summarize the data and answer the research questions. Spearman rho correlation was used in testing the first hypothesis to determine if significant relationship exists between flood disaster occurrence and the effects. In the second hypothesis, ANOVA was used to determine the significant difference among the communities in Ngwo as regards the impacts of flood disaster. The third hypothesis was tested using factor analysis. P value less than 0.05 level of significance was considered. The level of effects were determined as it affects damage to farmland and economic tress (agricultural effects), damage to infrastructural facilities (roads, schools etc), Markets (economic activities), health (loss of lives and injured) and water sources. The areas with high effects were identified. The study reveals that topography, inadequate drainage system and heavy rainfall are major causes of flood disaster in Ngwo The study reveals that the major cause of flood in the study area was the non availability/insufficient drainage system or total absence of the drainage system as the case may be. Also, high rainfall and dumping of waste into the drainage have contributed to the regular occurrence of flood in the area.

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CHAPTER ONE

INTRODUCTION

1.1 BACKGROUND OF THE STUDY

Flood is an overflow of water that submerges or "drowns" land. The European Union

(EU) Floods Directive defines a flood as a covering by water of land not normally

covered by water. In the sense of "flowing water", the word may also be applied to

the inflow of the tide. Flooding may result from the volume of water within a body of

water, such as a river or lake, which overflows or breaks levees, with the result that

some of the water escapes its usual boundaries or may be due to accumulation of

rainwater on saturated ground in an area.

The activities of man without adequate attention to geological structure of most cities

of developed and developing nations have undoubtedly contributed to reoccurrence

of disaster and consequently pose threats to environmental sustainability in most of

these nations (Oludare et al., 2012). This irrefutably has led or accumulated to

unresolved challenges. Among the unresolved challenges being faced are vicious

flood incidences experienced in the last four decades. The occurrence is stern in third

world countries where there is intensity in land use, haphazard development, and

unprecedented urbanization among others. According to Adeyinka et al. (2008)

“Most of these cities are also characterized by uncontrolled development ,

substandard and inadequate housing, poor infrastructure provision and development,

poor planning process and administration, weak urban governance, poor land use

structure resulting to slum…’’.

There has been unprecedented occurrence of floods and its associated effects in most

of the urban centers of developing countries (Montoya Morales, 2002). Several flood

disasters have occurred in Nigeria in the recent past. For instance, in Nigeria, reports

have shown that devastating flood disaster had occurred in Ibadan (1985, 1987, 1990,

and 2011), Osogbo (1992, 1996, 2002, and 2010), Yobe (2000), Akure (1996, 2000,

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2002, 2004 and 2006) and the coastal cities of Lagos, Ogun, Port Harcourt, Calabar,

Uyo and Warri among others. And the most recent flood of 2012 in Nigeria that

affected more than 12 states cannot be over emphasized. The incidence of flooding

has become more frequent and severe around the world, a situation that has been

attributed to climate change and sea-level rise (Clark et al., 1998).

The September, 2012 flood affected several states in Nigeria including Adamawa,

Kogi, Delta, Bayelsa and Rivers States, and displaced millions of people in the

process. The flood rendered millions of people homeless and their means of

livelihood destroyed. The social and economic impact of the recent flood incident,

particularly on agricultural production and social infrastructure, cannot be

overemphasized, yet the long term impacts of the recent flood in Nigeria could be

more severe.

According to Oyebande (1990) water will always find its way if not well

channelized. Its choice route often poses problems to man by tampering with his

physical environment, health and products of agriculture, urbanization and

industrialization. This has created a lot of social and economic cost on the

environment and the citizenry. Few among these social and economic impacts on the

environment are: outbreak of health diseases, infrastructure failure, mental health

effects, building collapse, destruction of agricultural farmland and products.

Flood has been reported as a major and devastating problem in some sectors of the

economy (Petak and Atkisson, 1982). Its effects are very severe to virtually all forms

of land use. The severity of its impact is also reflected on the rate of development of

most nations that experience such.

Though several scholars have analysed the problem of flooding in Nigeria (Atedhor,

Odjugo, and Uriri, 2011; Eni et al. 2011; Etuonovbe, 2011; Dabara, 2012), most of

the researches, however, focused on the health and social impacts of flooding. Eni et

al. (2011) investigated the impact of flooding on farmlands in Cross River State,

2

Nigeria using a combination of interview and laboratory methods, but the

implications of flood disaster on Ngwo Udi Local Government Area seems not to

have been investigated.

Moreover, it has been shown that the integration of Remote Sensing and Geographic

Information Systems (GIS) provide valuable and timely spatial information in the

event of a natural disaster. This approach has proved to be a very important tool in

the evaluation and management of natural disaster. Pradhan (2009) analysed flood

risk areas in the east coast of Malaysia using GIS and statistical models. Though

effective, this method may be time consuming as every part of the affected area need

to be visited for the purpose of collecting GPS data for elevation mapping and

modeling. Advanced Space-borne Thermal Emission and Reflection Radiometer

(ASTER) image and Shuttle Radar Topography Mission (SRTM) images provide a

means of generating the digital elevation model (DEM) of the landscape and

therefore, it can give an estimate of flood depth in areas inundated by flood water.

In Nigeria, flood disaster has been perilous to people, communities and institutions.

Recently, so many states of the federation were affected by flooding which have

claimed so many lives, damaged property, disrupt economic activities, caused grief

and emotional trauma and also displaced the inhabitants of the affected environments.

It shattered both the built-environment and undeveloped plan. It shattered both

artificial and natural environment. Properties worth millions of naira got lost due to

flood occurrences. One prominent feature about it is that flooding does not

discriminate, but marginalizes whosoever refuses to prepare for its occurrence NEMA

Newsletter 2012).

Whereas flooding itself is a situation that results when land that is usually dry is

covered with water of a river overflowing as a result of heavy rain, and dam over

flow, flooding occurs naturally on the flood plains which are prone to disaster. It

happens without warning but with a surprise package that always delivers to

3

unprepared community like the ones in Sokoto, Kaduna, Kebbi, Ogun, Lagos, Benue,

Jos, Adamawa, just to mention a few (Daily Sun Newspaper, July 12,2011 ; NEMA

Newsletter,2011).

Flood may create conditions that promote secondary treats of waterborne and vector

borne diseases as in respiratory diseases. Bruce (2003) identified the possibility of

human illness related to indoor mold growth in buildings. Dampness as a result of

accumulated water in corners, curves and other parts of a building may promote mold

growths. In more severe flooding, deaths and injuries are usually recorded. Business

and agriculture are affected by flood. So many farmlands have been washed away in

numerous communities, thereby contributing to food scarcity and widespread natural

disaster that need serious emergency (Internet. www.undp.org).

Floods have greatest impacts on low- lying areas, river valleys, and coastal zones. The

predicted consequences of global climate change which contribute immensely to

recent increase of flood all over the world may well worsen the situation for both

upland and low- lying areas. And Ngwo happened to be situated in a valley and top of

the hill all together. Inappropriate development plan, urbanization, and poor land

management will further aggravate the effects of climate change especially as relates

to flooding (UNDP, 2004).

In some places, water levels are increasing, whereas it is decreasing in some other

areas. The rainfall pattern is no longer what it used to be as we may experience

extended rainy season or delayed rain. And whichever way many at times, lead to

flood disaster.When flood disaster occurs, many environmental hazards are likely to

follow. Today; it is not only the coastal communities that can be affected by flood.

Poor urban planning are chief culprits in most flood cases we have in Nigeria today.

This study will identify the impacts of flood on communities in Ngwo.

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1.2 STATEMENT OF THE PROBLEM

Ngwo town in Udi L.G.A., Enugu state, is being threatened by the problem of flood

which has been devastating the communities since 2010. Consequently, many

economic activities have been paralysed, soil surface and farm lands are being washed

away along with damage to crops and creation of gullies. In a Community Report to

Enugu State Emergency Management Agency (ESEMA), (2010), it was recorded that

two primary school children were lost to flood in Ngwo in 2010. The Community

Report to ESEMA(2010) showed that loss of lives, markets and local small business;

and the destruction of infrastructure, including roads, school and health facilities, are

among the major impacts. Displacements and fatalities were recorded.

Flooding incidents around the town was associated with heavy and torrential rainfall

that ceaselessly fell for hours and sometimes days. Although the torrential rainfall is

the immediate trigger, the risk of flooding have often been heightened in periods prior

to the rainfall through human activities, including construction of home along flood

plains and river banks; siting and growth of villages and rural communities either at

the foot of hills (for protection) or also along river banks.

These have been compounded by such other activities as blocking the waterways/river

paths/flood plains through indiscriminate disposal of domestic and industrial waste.

Essentially, the poor have borne the brunt of the situation because they are the ones

who are forced by poverty to seek accommodation or build their homes in such highly

vulnerable areas. The impact of these flood disasters have often been quite

overwhelming not only on the communities immediately impacted but also on the

capacities of local and state disaster management agencies.

However, various efforts have been made to assuage the flood problem in Ngwo so as

to reduce the impact. Such efforts include digging of catchment pit by some residents

in their various compounds to reduce the surface water flow, excavations by Arab

5

Contractors Construction Company, through the efforts of ESEMA and NEMA

collaboratively, in August 2010; and construction of drainage channels in some areas.

In spite of these measures, the problem of flooding still persists in Ngwo, and no

further study has been carried out on the flood hazard in the area. It is based on this

situation that this study is set out to empirically examine the effects of the flooding on

the environment in Ngwo. It is expected that the result of this study will provide

measures that can reduce vulnerability and increase community resilience and

response to flooding.

1.3 AIM AND OBJECTIVES OF THE STUDY

The aim of the study is to examine the flood disasters and their effects in Ngwo,

Enugu State.

The following objectives are put forward in line with the aim of the study:

(i) To assess the spatial extent of flood inundation and identify the most affected

areas;

(ii) To evaluate the effects of flooding on the environment

(iii) To assess the extent of damage encountered as a result of flood in Ngwo.

1.4 RESEARCH QUESTIONS

(i) What is the spatial extent of flood inundation and which areas of the town are

affected?

(ii) What are the effects of flood disaster on the communities and the extent of

damages?

(iii) What measures can be adopted to reduce flood vulnerability in the area?

6

1.5 RESEARCH HYPOTHESES

HO 1: There is no significant relationship between flood disaster occurrence and flood

disaster effects.

Ho 2: The effects of flood disaster do not vary significantly among communities in

Ngwo

Ho 3: There is no identifiable significant pattern of flood effects in Ngwo

communities

1.6 SCOPE OF THE STUDY

The extent of this study will be on effects of flood disaster on Ngwo and its

environment. The research will identify the likely causes of flood and evaluate the

effects in the area through the use of Geographical Information System.

It will also focus on the assessment of the extent of damage caused by flood and its

environmental hazards through the use of GIS remote sensing, with a handheld GPS

hazard map, the disaster problems are identified. Finally, recommendations were

made based on the findings. These will help in preparation, prevention, mitigation and

response and recovery in future disaster management.

1.7 SIGNIFICANCE OF STUDY

This study will be of great benefit to both citizens and settlers in Ngwo communities,

professionals, students and academics, government and the general public at large.

The study will help Udi Local Government Area to know the areas that are prone to

flood in communities in Ngwo; the extent of damage of flood in the areas; and the

likely causes of flood in Ngwo. Also, the study will guide town planners and members

7

of the public that dwell and/ or do business in Ngwo on better land use/ land cover of

the environment.

1.8 LIMITATIONS OF THE STUDY

Some respondents had wrong perception of the questionnaire. Some of them thought

had the impression that it is governmental project, and refused to cooperate in filling

the questionnaire.

Again, some respondents demanded for money before they could respond to the

questionnaire. Not meeting such demand could have affected their disposition to

filling the questionnaire. High cost of obtaining data from NIMET reduced the

number of years of rainfall data that was used for the study.

1.9 DEFINITION OF TERMS

(a) Arc GIS: Arc Geographic Information System

(b) Coordinates: Coordinates define a point with reference to an ellipsoid.

Coordinates are defined using latitude, longitude and ellipsoidal height.

(c) Fluvial: Connected with water.

(d) GPS: Global Positioning System.

(e) Gauge/ Gage: An instrument for measuring the amount of level of something.

(f) Alluvial: Made of sand or earth that is left by rivers or floods.

(g) Percolate: (of a liquid –water) to move gradually through of surface that has

very small holes or spaces in it. Water percolates down through the rocks.

(h) Inundation: To cover an area of land with a large amount of water.

(i) Handheld Differential GSP: Differential Global Positioning System is a

system that utilizes differential code connections to achieve an enhanced

positioning accuracy of around 0.5 – 5m.

8

(j) Topography: The form of land of a particular region.

(k) Space segment/Satellite: The part of the whole GPS system that is in space.

9

CHAPTER TWO

THEORETICAL FRAMEWORK

2.1 GEOPHYSICAL THEORY

Vijay Gupta, a professor of Civil and Environmental Engineering, came up with the

theory that links spatial temporal statistics of rainfall, stream flow, and flooding with

physical watershed and channel network characteristics over spatial scales ranging

from small tributary watershed to large basins. According to Gupta, the Geophysical

theory of flood seeks to resolve questions such as those involving the relationship

between a watershed’s topography, the geometry of its river network and spatial

statistical stream flow variation. Gupta’s motivation is to improve real – time flood

prediction, which is more art than science. He and his colleagues have discovered a

remarkable property: stream networks and floods are mutually related through self-

similarity.

Gupta further stated that “this gives us a foundation for extending our theories of

flooding to unguaged catchments, where little data are available”. (Cooperative

Institute for Research in Environmental Sciences:2014).

2.2 THE HYDRO – PLATE THEORY: THE GREAT FLOOD

According to the hydro – plate theory, the pre- flood earth had a lot of subterranean

water, about half of what is now in our oceans. This water was contained in

interconnected chambers forming a thin spherical shell about half a mile thick perhaps

10 miles below the earth’s surface.

Increasing pressure in the subterranean water stretch the crust, just as the balloon

stretches when the pressure inside increases. Failure in the crust began with a

microscopic crack which grew in both directions at about 3 miles per second. As the

crack raced around the earth, the overlaying rock crust opened up. The subterranean

10

water was under extreme pressure because the weight of the 10 miles of rock pressing

down on it. So the water exploded violently out of the rupture. Some of the water,

jetting high above the cold atmosphere froze into super - cooledice crystals and

produced some massive ice dumps, suffocating and instantly freezing many animals.

The continental plates, the hydro plates, still with lubricating water beneath them slid

downhill away from the rising mid – Atlantic ridge. The massive slowly accelerating

continental plates compressed and buckled. The portions of the hydro plate that

buckled down formed ocean trenches. Those that buckled upward formed mountains.

The hydro plates, in sliding away from the oceanic ridges, opened up very deep ocean

basins into which the flood waters retreated. On the continents, each bowl- shaped

depression, or basin was naturally left brim full of water; producing many post- flood

lakes. (Internet: Walter Brown, Center for Scientific Creation).

2.3 ANCIENT FLOOD THEORY

Colombia marine geologists, William B.F. Ryan and Walter C. Pitman 3rd inspired a

wave of archaeological and other scientific interest in the Black Sea region with

geologic and climate evidence that a catastrophic flood 7,600 years ago destroyed an

ancient civilization that played a pivotal role in the spread of early farming into

Europe and much of Asia.

Inspiring a re-examination of the role of climate in human history, Ryan and Pitman’s

findings in 1996 suggested that the terrifying and swift flood may have cast such a

long shadow on succeeding cultures that it inspired the biblical story of Noah’s ark.

Ryan and Pitman argued their provocative theory in a 1999 book, ‘’Noah’s Flood: The

New Scientific Discoveries about the Event That Changed History” (Simon and

Schuster, 1998). Ryan and Pitman theorized that the sealed Bosporus strait, which

acted as a dam between the Mediterranean and Black Seas broke open when climatic

warming at the close of the last glacial period caused icecaps to melt, raising the

11

global sea level. With more than 200 times the force of Niagara Falls, the thundering

water flooded the Black Sea, then no more than a large lake, raising its surface up to

six inches per day and swallowing 60,000 square miles in less than a year. (Internet:

E\Ancient Flood Theory Supported By Discovery of Human Artifacts.htm).

2.4 EVIDENCE AND THEORIES OF A GREAT FLOOD

Hundreds of myths from around the world suggest there was a great flood – possibly

local or possibly global, depending on the story.

There are two scientific theories in existence, one suggesting flooding around the area

that is now the Black Sea and the other attributing devastating floods to a comet that

struck the earth.

In the late 1990s, Columbia University geologists, William Ryan and Walter Pitman

proposed that a great flood in the Middle East resulted from rising water levels at the

end of the last Ice Age about 7000 years ago. At that time, the Black Sea was a

freshwater lake and the lands around it were farmlands. When European glaciers

melted, the Mediterranean Sea overflowed with a force 200 times greater than that of

Niagara Falls, converting the Black Sea from fresh to saltwater and flooding the area

(source: National Geographic).

Moreover, Bruce Massse, an environmental archaeologist at Los Alamos National

Laboratory, put forth his own theory about the great flood. He hypothesizes that more

comets and meteors tan we know have hit earth throughout its history. He believes

that the seeds of great flood stories may have sprouted when a great comet hit our

planet about 5,000 years ago. Masse’s presumption is that a 3 mile (4.8 kilometer)

wide comet crashed into the ocean off the coast of what is now Madagascar. 600 foot

(182.8 meter) high tsunamis and massive hurricanes spawned when superheated water

vapour and aerosol particulates shot into jet stream (Internet: E\Howstuffworks

“Evidence and Theories of a Great Flood”.htm).

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Disaster is defined as the serious disruption of a community or society causing

widespread human, material, economic and environmental losses which exceed the

ability of the affected community or society to cope using its own resources

(UN/ISDR,2004). Disasters are caused by the extent to which the elements at risk

{people, infrastructure, buildings, and assets} are vulnerable to hazard or threat.

The 1994 Yokohama Strategy noted as follows:

Natural disasters continue to strike and increase in magnitude, complexity and

economic impact. Whilst natural phenomena causing disasters are in most cases

beyond human control, vulnerability is generally a result of human activity(ISDR

2004, p 9).

The risk in a disaster is partially dependent on physical hazards like floods. Flood is a

natural hazard. Flood risks are associated with physical exposure and variables tied to

GDP per capita and low densities of population.

A flood is an overflow of water that submerges land. The European Union (EU)

Floods Directives defines flood as a covering by water of land not normally covered

by water. Flooding may result from the volume of water within a body of water, such

as a river or lake which overflows or breaks levees, with the result that some of the

water escapes its usual boundaries (MSN Encarta Dictionary).

While the size of a lake or other body of water will vary with seasonal changes in

precipitation and snow melt, it is not a significant flood unless such escapes of water

endanger land areas used by man like a village, city or other inhabited area.

The word “flood” comes from the Old English “flood”, a word common on Germanic

languages. Floods can occur if water accumulates across an impermeable surface (e.g.

from rainfall) and cannot rapidly dissipate (i.e. gentle orientation or low evaporation).

Climate change increase the complexity and uncertainty of risks as floods and storms

become more frequent. A disaster due to hydro meteorological hazards like floods is

13

one of the most common in Africa, accounting to 59 per cent of disaster events (ISDR,

2004).

Flood is one of the most common widespread natural disasters. It occurs throughout

the whole world. Coppola,(2011), states that annually, more people are killed by

flooding than any other hazard, with an average of 20,000 deaths and 75 million

people affected each year(from the International Disaster Database, www.em-dat.net).

Floods can be either slow or fast rising, generally developing over days or weeks.

Most often, they are secondary hazards resulting from other meteorological processes,

such as prolonged rainfall, localized and intense thunderstorms, or onshore winds.

Moreover, other processes which can generate rapid and widespread flooding include

landslides, logjams, avalanches, icepack, levee breakage, and dam failure.

2.5 THE CONCEPT OF ENVIRONMENT AND SUSTAINABLE

DEVELOPMENT

Sustainable Development is development that meets the needs of the present without

compromising the ability of future generations to meet their own needs. It contains

two key concepts: the concept of “needs”, in particular the essential needs of the

world’s poor to which overriding priority should be given: and the idea of limitations

imposed by the state of technology and social organization on the environment’s

ability to meet present and future needs.(Brundtland Commission,1987)

Abramovitz et al (2001), UNISDR: Disaster Risk Reduction is clearly part of a

broader strategy of sustainable development- making communities socially,

economically and ecological sustainable.

Afolabi,(2008), examined Improving Urban Land Use Planning And Management in

Nigeria: The Case of Akure. He posited the importance of urban land use planning

and management to sustainable development. The study indicated the implications of

14

uncoordinated land use management in context of developing world cities and

suggests how to improve the present inefficient practices. (Jiboye,2005).

Sustainable Development is generally recognized as the optimum way to harmonize

human kind’s interaction with and dependence on our environment to the ultimate

benefit of both. Disaster Risk Reduction and Environmental Protection are two

essential components of Sustainable Development (UN/ISDR,2004). The risk of a

disaster occurring is based on physical, economic and environmental factors, all of

which need to be monitored and evaluated continuously (UN/ISDR,2002). The

environment is made up of the earth, water, atmosphere and biosphere. Our social and

economic activities impact on the environment.

The three pillars of sustainable development are:.

i. socio-cultural equity and quality (socio capital)

ii. Economic growth (Economic and Financial capital)

iii. Environmental Protection (Natural capital)

2.6 ENVIRONMENTAL PROTECTION

“Environmental protection as a component of sustainable development, consistent

with poverty alleviation, is imperative with prevention and mitigation of disasters”

(Yokohama Strategy and Plan of Action for a Safer World). Adopting sound

environmental protection measures will ensure that “we can meet our present needs

without compromising the ability of future generations to meet their own needs”

(Brundtland Commission, 1987). Environmental protection is mainly aimed at

protecting the natural functioning of ecosystems and the sustainable use of natural

resources. Many communities in Africa depend on natural resources and small scale

cultivation or livestock farming for their livelihoods. This means that they are

vulnerable to change in the environment, the impacts of extreme natural events and

poor land use or resource management.

15

Wherever we live, the natural environment is determined by the climate, the soils and

the topography. Plants and animals comprise a natural community and the conditions

define a habitat. If a habitat is degraded, fewer kinds or species of plants and animal

can thrive in it and biodiversity is lost (http:/www.unep.org).

The primary geological, climate- related, biological and technological hazards often

give rise to secondary hazards. In many cases, these secondary hazards are on a

greater threat to a community, for example, flash, coastal, river floods and landslides.

Loss of biodiversity results in an increasingly unstable environment and eventual

destruction of the ecosystem. This in turn reduces the quality of the ecosystem

resources which adversely affects a community livelihood. (UN/ISDR and

UNEP,2002)

16

CHAPTER THREE

LITERATURE REVIEW

3.1 INTRODUCTION

Flood is a body of water which rises to overflow land which is not normally

submerged, Ahman (1997). She posited that floods are environmental hazards that

occur regularly every year in different parts of Nigeria with wide ranging effects.

Islam and Sabo (2000) noted that the quantity of water and rate of rise in water level

influences the damage caused by flooding.

Coppola (2011) explained that flooding is a secondary hazard associated with debris

movements, especially when the runoff zone impedes the flow of a river or stream,

forming a natural dam. Debris movements can also trigger a tsunami if its runoff zone

terminates in a large body of water. Debris flows are dependent upon the introduction

of the great amounts of water from prolonged rainfall, flash flooding, or very rapid

snowmelt.

Moran et al (1980), in their own perspective, noted that flood occurs whenever runoff

exceeds the discharge capacity of a river channel causing water to overflow its banks

and spread over the bank plain. Flooding is a natural flow of water and flood

conditions exist when the discharge of river cannot be accommodated within the

margins of its normal channel. Flooding is highly related to the amount and intensity

of precipitation. Most dangerous flooding has connections with rivers where the river

volumes are increased by precipitation.

Previous studies also reported that communications and traffic are interrupted while

many land areas are inundated, and industrial plants and commercial establishment are

paralyzed during floods. Besides, untold hardship is experienced, especially by the

most vulnerable groups (women and school children) whenever there is flood disaster

(Oluduro, 1988; Durotoye, 1999; Folorunsho and Awosika, 2001).

17

Flooding is more dangerous in wetlands and flood plains. Widening of a river channel

and destruction of part of the floodplain by major floods arecommon and has been

observed in semiarid regions. As is the case with these regions having a high erosion

potential, the phenomenon of channel migration during flooding events will often

cause a large portion of flood waters to be carried in a channel that did not exist prior

to the onset of the flooding event. This phenomenon occurs all too frequently in arid

regions, where high velocity flood waters make drastic changes in the channel

configuration during the flooding event. In many flood cases, lives and properties are

lost or infrastructure destroyed.

According to Hoyt and Langbein (1955), flood losses are the destruction or

impairment, partial or complete, of the value of goods or services or of health

resulting from flood. It can be direct or indirect, tangible or intangible depending on

the nature.

The Pit Review (2008) stated that as little as 15cm of water can knock people off their

feet – especially if they are frail and is sufficient to float a car. On small streams,

floods induced by rainfall usually last from only a few hours to a few days, but on

large rivers flood runoff may exceed channel capacity for a month or more. Also Mba

{1996} posited that flooding hazards appear to be much more common in Nigeria in

areas that are a little above sea level and may occur occasionally in the hinterlands.

Flood is a large amount of water covering an area that is usually dry, (Oxford

Advanced Learner’s Dictionary).

As at October, 2010, the National Emergency Management Agency (NEMA),

confirmed that about 500,000 Nigerians were displaced by flood disaster source. This

was disclosed by the DG NEMA, during a Rapid Assessment of flooded communities

in Bayelsa State. Thus according to Ward (1980), flood is a body of water which rises

to overflow land which is not normally submerged. As recorded by Akintola(1981),

the causes of increased flood are due to increase in the percentage of impervious

18

surface, landscaping, especially through removal of vegetation; subdivision of land

into building sites without adequate land categorization and filling in and human

occupation of floodplains. Drainage and irrigation ditches, as well as water diversions,

can alter the discharge into floodplains and the channel's capacity to carry the

discharge. The effects of agricultural and crop practices vary and depend upon the

local soils, geology, climate, vegetation, and water management practices. Forest

vegetation in general increases rainfall and evaporation while it absorbs moisture and

lessens runoff. Deforestation or logging practices reduce the vegetation and a forest's

absorption capacity, thus increasing runoff. Overgrazing in grassland or rangeland

areas decreases the vegetation cover and exposes soil to erosion as well as increased

runoff.

The local features of the physical environment which promote flooding include the

average slope of the land especially low – lying topography and steep slopes, type of

land use, particularly urban land use and the condition of the drainage system

[Nwafor, 2006]. Flooding in natural catchments is very severe during the rainy season

in the coastal plain sands and the extensive and swampy alluvial plains of major

rivers.

With reference to Oyebande(1975), flooding in artificial catchments during the rainy

season is often disastrous. This is because in urban centres, a substantial proportion of

land area is covered by pavements, roofs over buildings and other types of man- made

impermeable surfaces which dispose of the rain water directly onto impervious

drainage systems that characterize artificial catchments. The uncontrolled expansion

of impermeable surfaces coupled with rapid population growth is one of the major

causes of flooding in urban environment in Nigeria (Nwafor, 2006). Related to this is

the increase in runoff volume as a result of physical development and expansion.

Flood disaster which occurred in Lagos and Ibadan in 2011 are typical examples that

flood is as a result of heavy down pour.

19

Engr. Mrs. Ikeji Oyeleke of Ministry of Environment (Thursday 20th September

2012), in Nigeria Television Authority, A.M Express programme, stated that climate

change and encroaching on floodplains have contributed to making flood disastrous.

Engnr.Adekunle Oshikoya of Climate Change Unit, Ministry of Environment, further

posited that a lot of water is melting in the arctic region, thereby, increasing the

volume of water.

Flood hazards are natural phenomena, but the damages and losses from floods are the

consequence of human action. It has known that floods can be caused by

anthropogenic activities and human interventions in the natural processes such as

increase in settlement areas, population growth and economic assets over low lying

plains prone to flooding leading to alterations in the natural drainage and river basin

patterns, deforestation and climate change (European Commission, 2007; Balabanova

and Vassilev, 2010; Kwak and Kondoh, 2008).

There are a number of tested techniques that could be used singly or in combination to

map flood hazards and risk; which include information on historical floods, soil maps,

aerial photographs, hydrological modeling of the major rivers, use of national digital

terrain model and water levels, and satellite imagery, etc (Hassan et al, 2000;

Bruzzone and Smits, 2002; Kondolf and Pigay, 2003; Mansor et al, 2004; Onana et al

(n.d); Ojigi, 2010). Geospatial technologies have been effectively used globally in

respects of flood and water logging disaster monitoring and evaluation, water

resources and water environment investigation, soil corrosion and soil protection,

river and reservoir sedimentation monitoring, river/lake and river mouth evolvement

investigation as well as soil moisture and drought condition monitoring (Li and

Huang, 2002). Ojigi and Shaba (2012) identified the integration of synthetic aperture

radar data and digital terrain model as a rapid flood hazards and risk mapping

technique for emergency management, as it offers in-situ inundated status and terrain

factor for rescue and relief operations.

20

3.2 EFFECTS OF FLOOD

Primary Effects:

Physical Damage: Floods can damage any type of structure, including bridges, cars,

buildings, sewage systems, roadways and canals.

Secondary Effects:

Water Supplies: One major secondary effect of flood is contamination of drinking

water. Clean drinking water will become scarce.

Diseases: unhygienic conditions which can lead to spread of water -borne diseases are

likely to occur. Bacteria, fungus, viral organisms and mosquitoes breed in stagnant

waters which collect in gutters and potholes as a result of flood help in widespread of

malaria, epidemics, cholera, typhoid fever and other manner of fever and diseases.

Increased Soil Erosion: This is simply a systematic removal of soil, including plant

nutrients, from the land surface by the various agents of denudation (Ofomata, 1985).

Crops and Food Supplies – shortage of food crops can be caused due to loss of entire

harvest.

Trees: non-tolerant species can die as a result of suffocation.

Transport: flood can destroy the roads and other transport components which can

make it so hard to get emergency aid to those who need it.

Tertiary and long term effects:

Economic: Flooding leads to economic hardship due to temporary decline in tourism,

rebuilding costs, food shortage leading to price increase, loss of business, etc.

21

3.3 ECONOMIC AND HEALTH EFFECTS OF FLOOD ON BUILDINGS

Flood can have significant effects on long – term economic growth of the affected

region. Indirect and secondary effect on the local and national economy may lead to a

reduction in the family income, which would eventually result to the increase in

spending, trying to repair the damage houses and household gadgets like electronics,

rug and more.

Flood may create conditions that promote secondary treats of waterborne and vector

borne diseases as in respiratory diseases. Bruce (2003) identified the possibility of

human illness syndromes related to indoor mold growth in buildings. Dampness as a

result of accumulated water in corners, curves and other parts of a building may

promote mold growths. In more severe flooding, deaths and injuries are usually

recorded. Flood is too much water in the wrong place whether it is an inundated city

or a single drain.

Adedeji, A.A. (2008), examined the Environmental Hazard: Flooding and its Effects

on Residential Buildings in Ilorin. Generally, some of the mechanisms that trigger

flood are dam or levee failure, more rain than what the landscape can dispose of, the

torrential rains of hurricanes, tsunamis, ocean storm surges, rapid snow melts, ice

flows blocking a river and burst water mains.

Between the years 1971 – 1980, and between 1993-2006, which coincided with

global warming experiencing in the world till today with sad news from US, Haiti,

Europe, Cuba. Ngwo, of recent has experienced the occurrence of the flood events,

while the rains recorded were greater than 25.4 mm. Naturally, flood could be due to

a high water table in an area, topography (low-land close hills), and low infiltration

such as clayed soil.

Flood is an overflow of an expanse of water that submerges land (Wikipedia.org).

The European Union (EU) Floods directive (2007), defines a flood as a temporary

22

covering by water of land that is not normally covered by water. In the sense of

"flowing water", the word may also be applied to the inflow of the tide. This water

comes from the overflow of sea, lakes, rivers, canals, sewers or from rainwater.

Flooding is normally caused by natural weather events such as heavy rainfall and

thunderstorms over a short period, prolonged rainfall or extensive rainfall. It can also

be caused by high tide combined with stormy conditions. It is predicted that climate

change will increase the risk of flooding in the UK and other parts of the world

(Petak and Atkisson, 1982). Ministry of Agriculture and fisheries (2004) also

reported that “risk is also experienced when there is heavy downpour or portion of

rainfall or thawing snow flows overland away from the area it originally precipitated,

this is called runoff”.

Odunuga et al. (2012) in his investigation also established “that Flood occurs when

there is overflow of urban drainages over the streets to extent that it cannot be

absorbed by earth surface and consequently results to property damage, traffic

obstruction and nuisance as well as health hazardsFloods often cause damage to

homes and businesses if they are located in natural flood plains of rivers (Tinh and

Hang, 2003). Oludare et al. (2012) also established that “in flood disaster there is

always loss of lives, destruction of public utilities and disruption in smooth

functioning of the system that renders fear and uncertainties among the populace,

loss of livelihoods, damage to environment, financial loss and diversion of resources

epidemics, migration, food shortages and displacement of people.

Flood is very problematic; its devastating effects on buildings can be categorized into

three:

1. Structural.

2. Economic

3. Health Related Effects.

23

STRUCTURAL EFFECT

Disasters Management Center, college of Engineering, University of Wisconsin –

Madison (1995) identified the following structural effects on buildings:

(i) Buildings washed away due to the impact of the water under high stream

velocity. Such buildings are usually destroyed or dislocated beyond feasible

reconstruction.

(ii) Floatation of buildings caused by rising water. This occurs when light–weight

houses are not securely anchored or braced.

(iii) Damage caused by inundation of buildings: A building may remain intact and

stable on its foundation, while its material is gradually and severely damaged.

(iv) Undercutting of building: here the velocity of flood may scour and erode the

building’s foundation or the earth under the foundation. This may result in

total collapse of affected buildings.

(v) Damage caused by debris: massive floating objects like trees and materials

from other collapsed house may have impact significant enough to cause

damage to the standing buildings.

The health consequences relating to flood can be either due to direct impact on human

population, direct impact on existing infrastructure or due to combination of both

factors. Flood can affect health directly or indirectly. The health effect can come long

after the flood. The impact of flood on people’s lives depends on the severity and

vulnerability and resilience.

(i) Drowning and injuries,

(ii) Infectious diseases,

(iii) Respiratory diseases and

(iv) psychosocial problems

(v) Infrastructural damages are all consequences of flooding on man and

(vi) Environment.

24

MENTAL HEALTH EFFECT

The effects on people’s health, relationships and welfare can be extensive. Accounts

of the psychosocial impacts of flood events suggest that they can have significant

effects on people’s wellbeing, relationships and mental health. Flooding can pose

substantial social and welfare problems that may continue over extended periods of

time because of not only being flooded (the primary stressor), but also because of the

secondary stressors (those stressors that are indirectly related to the initial extreme

event, i.e., economic stress associated with re-building) that arise as people try to

recover their lives, property and relationships. Flooding can challenge the

psychosocial resilience of the hardiest of people who are affected. Review on the

global health impacts of flooding, Ahern et al (2005), report a number of

epidemiological studies which examined the effects of flooding on common mental

disorders (including anxiety and depression), post-traumatic stress disorder (PTSD)

and suicide. Most studies exploring the effects of flooding on common mental

disorders came from high or middle-income countries, and results revealed

significant increases in depression, anxiety and psychological distress among flooded

adults; relatively few studies examined the effects of flooding on children, but those

that did revealed increases in aggression, bedwetting and moderate to severe stress

symptoms. Studies showing increases in PTSD following flooding came from Europe

and North America, with limited evidence reported about suicide in relation to

flooding.

Flood waters may carry debris or conceal other hazards harmful to man and

environment. Floods have the potential to increase the transmission of diseases,

depending on the circumstances of the environment, whether low income (poor) or

high income environment/ place. The risk is increased by population displacement,

loss of clean drinking water, poor sanitation, poor nutritional status and inadequate

access to health care.

25

Psychosocially, flood often causes devastating personal losses, like loved ones,

livelihood, home, business/ offices and other personal belongings. This can even lead

to mental health related problems. Flood exposure can cause depression (Galea et al,

2007), Archives of General Psychiatry.

FOOD SHORTAGE EFFECT

Agriculturally, food supply may be affected by flood as a result of damage to crops

and livestock or to stores of food. According to Director General, National Emergency

Management Agency (NEMA), Sani Sidi, the recent weather patterns in the country

and indeed the world at large, has resulted in adverse ecological imbalances, making

us victims of flood and other disasters in the North, South, East and West of Nigeria.

The severity of the incident of flood now is worrisome (NEMA 2010).

3.4 FACTS ABOUT FLOODING:

Flooding poses tremendous danger to both people and property. Since 1900, floods

have taken more than 10,000 lives in the United States alone.(UN/ISDR,2004).

Flood result from overflowing of a great body of water over land and extreme

hydrological events or an unusual presence of water on land to a depth which affects

normal activities (Olajuyigbe, 2012; and PointBlankNews.com). It also occurs as a

result of combination of meteorological and hydrological extremes as well as

activities of man on drainage basin (Adeaga, 2008).

The Big Thompson Canyon (Colorado) Flood, which killed 140 people in 1976,

proved a tragic illustration of a sobering statistic 95% of those killed in a flash flood

try to outrun the waters along their path rather than climbing rocks or going uphill to

higher grounds. Most people are unaware that 66-percent of flood deaths occur in

vehicles, and most happen when drivers make a single, fatal mistake trying to

navigate through flood waters. Just 6 inches of rapidly moving flood water can knock

a person down. A mere 2 feet of water can float a large vehicle even a bus. One-third

26

of flooded roads and bridges are so damaged by water that any vehicle trying to cross

stands only a 50% chance of making it to the other side. Beyond the risk of fatalities,

floods devastate homes, towns, and even entire regions

(www.weather.com/encyclopedia/flood/tom.76.html).

The great Mississippi River Flood of 1993 covered an area 500 miles long and 200

miles wide. More than 50,000 homes were damaged, and 12,000 miles of farmland

were washed out. (www.weather.com/encyclopedia/flood/miss93.html).

The Weather Channel correspondent Dave Malkoff says there are things you can do

to keep your home standing even in just about the worse that Mother Nature can

produce.

Flooding can be caused by the overflowing of rivers and lakes; by serious breaks in

dikes, levees, dams and other protective structures; by uncontrollable releases of

impounded water in reservoirs and by the accumulation of excessive runoff.

Floodwaters cover a wide contiguous area and spread rapidly to adjoining areas of

relatively lower elevation. Flooding is relatively deep in most parts of the stricken

areas. There is a highly perceptible current as the flood spreads to other areas.  While

floods take some time, usually from 12 to 24 hours or even longer, to develop after the

occurrence of intense rainfall, there is a particular type which develops after no more

than six hours and, frequently, after an even less time. These are what are known as

"flash floods"

 Flash floods develop in hilly and mountainous terrains where the slope of the river is

rather steep as identified in Ngwo. The rapid development of the flood is due to the

extremely short concentration time of the drainage catchment. This means that

precipitation falling on a point in the catchment farthest from the streams takes only a

short time to reach the water channel and become part of stream flow. Thus, the

amount of stream flow rapidly increases and, consequently, the rise in water level.

27

When the flow capacity of the stream is exceeded, the channel overflows and the

result is a flash flood.

3.5 FLOOD PREVENTION AND CONTROL

Many different methods can be used to prevent flooding:

In North American, according to Landis (2000), sandbagging is a standard method

used for flood protection and is quite successful. During the events of flooding, bags

are filled with sand and are stacked in a pyramid type arrangement. The walls

constructed by the sandbags are indeed stable and provide a secure structure to

withstand the forces of the rising water due to flooding.

Since the 1950’s inflatable dam products developed by Imbertson of the Los Angeles

Department of Water and Power were available as a method of controlling the rising

flood water. It was initially manufactured by the Fireston Tire and Rubber Company.

They are typically filled with air using an air compressor and are anchored to a

concrete base or abutment (Plaut et al. 1998).

Plaut and Klusman (1999) mention that geosynthetic tubes have played roles in

preventing beach erosion, protecting tunnels, and diverting pollution. Many types of

fabric such as nylon. Polyester, polypropylene and polyethylene are used to produce

the geosynthetic material (Koerner and Welsh, 1980). The tubes acted as a flexible

form so that concrete could be pumped the tubes.

UN/ISDR (2002) put it clearly that communities must adopt the notion that disaster

impacts can be reduced and therefore not only waits for disasters to be managed. In

some cases, it might be possible to reduce hazards themselves. If not, then it would

certainly be possible to reduce human vulnerability to those hazards.

28

(i) Early warning systems cannot be over emphasized. It is a process that

provides timely information so that communities are not only informed, but

sufficiently impressed, that they take preparedness actions before and during

the anticipated flood events. It depends on practical relationships between

science and technology, and the understanding of social and economic impact

of flood disaster in the context of sustainable development.

The purpose of obtaining early warnings of impending flood disaster is to enable

communities at risk to act timeously and appropriately so as to reduce the possibility

of injury, loss of life and damage to property and the environment.

The three steps of developing early warning include, forecast and prediction, using

and announcing the warning (as NEMA is doing now concerning more expected

floods in the country) and reaction.

(i) The flood we are having recently is natural, but some are equally human

induced. Therefore, there must be a form of adjustment, a form of

communication and a form of willingness with the populace. People must be

put at alert through the use of media, town criers, newspapers and daily

periodicals, churches, mosques, traditional rulers and political office holders.

(ii) As posited by the flood – Wikipedia, the free encyclopedia, E:\

floodresearch.htm (internet, 12 -06- 12), in many countries across the globe,

rivers prone to floods are often carefully managed. Defenses such as levees

bunds, reservoirs and weirs are used to prevent rivers from bursting their

banks. Emergency measures such as sandbags or portable inflatable tubes are

used in cases of defense failure.

(iv) Loss of vegetation leads to a risk increase. In Asia, forests are being planted

in places like India, Bangladesh and China. President Goodluck Jonathan of

Nigeria has also lunched planting of one million trees campaign. Reducing the

rate of deforestation should improve the incidents and severity of floods.

29

(v) In the United States, the New Orleans Metropolitan Area, 35% of which sits

below sea level is protected by hundreds of miles of levees and flood gates. But

this system failed catastrophically, in numerous sections during Hurricane

Katrina, resulting in the inundation of some part of metropolitan area. Some

properties were bought and converted into wetlands to act as a sponge in

storms.

(vi) Also in the Canadian province Manitoba, the Manitoba government undertook

the construction of a massive system of diversions, dikes and floodways to

protect the city from floods.

(vii) Still quoting from the same source, Europe is not left behind. London is

protected from sea flooding by the Thames Barrier, a huge mechanical barrier

across the River Thames, which is raised when the sea water level reaches a

certain point.

(viii) The Adige in Northern Italy was provided with an underground canal that

allows draining part of its flow into the Garda Lake, thereby lessening the risk

of estuarine floods.

(ix) However, the most elaborate flood defenses can be found in the Netherlands,

where they are referred to as Delta Works. The country has one of the world’s

largest dams constructed.

(x) In Nigeria, taking Ngwo for instance, catchment pit is the common flood

defense approach being practiced. It is dug around homes or business

environments to help restrict water from overflowing the environment.

3.6 COMPUTER MODELING

Flood modeling is a fairly recent practice. The recent development in computational

flood modeling has enabled engineers to step away from the tried and tested approach.

30

Various computational flood models have been developed in recent years. There are

1D models (flood levels measured in the channel) and 2D models (flood depth

measured for the extent of the floodplain).

HEC – RAS, the Hydraulic Engineering Centre model, is currently among the most

popular. Other models such as TUFLOW combine 1D and 2D components to derive

flood depth in the floodplain. The 2007 flood events in UK have led to emphasis on

the impact of surface water flooding.

Wang, Colby, and Mulcahy, (2002) mapped flood in the United States using Landsat

TM and noted that DEM assists in identifying flooded areas in coastal areas and in

areas of large spatial extents with relatively flat topography such as exists in Ngwo.

Similarly,

Pradhan, (2009) has noted that the use of DEM was effective in delineating areas

vulnerable to flooding.

3.7 FACTORS AFFECTING FLOOD

According to Annie (2000), in his examination, the following factors affect the bulks

of flood resulting from rainfall and flow of river(s):

Land use/Land cover (LULC): the first characteristics to be considered when

determining flood risk is the LULC. This is because the runoff results from rainfall

farmland or forest.

(iii) River floodplains: These include the low-lying, highly fertile areas that

flank rivers and streams. They tend to be highly populated because of their

ample irrigation and fertile soil. When the floodplain is wide, water velocity

is low and vise versa. Water flowing at high velocity will cause more

erosion and damage.

31

(ii) Basins and valleys affected by flash flooding: flash flooding is a significant

risk in basins and valleys where runoff from intense rainstorms collects and

concentrates. More lives are lost in this kind of flooding than any other because

very little warning is possible, and evacuation can be difficult due to the

surrounding terrain.

(iii) Land below water - retention structures (dams): Dam failures, which can

occur due to poor maintenance or as a secondary disaster from other natural or

manmade processes, often because flooding downstream from the dam as it releases a

torrent or retained water.

(iv) Low – lying coastal and inland shorelines: Coastal shorelines often flood as a

result of a storm surge preceding hurricanes, cyclones and other major

windstorms.

(v) Alluvial Fans: this type of landscape, often the result of previous periods of

hydrologic activity, can become very dangerous during flash floods when

unpredictable water drainage patterns emerge (Smith, 1992).

(vi) Soil moisture content: how dry or wet a land is affecting the rate of infiltration

hence, the runoff. The moisture content is inversely proportional to the rate of

infiltration.

3.8 FLOOD AND CLIMATE CHANGE

Climate change is a significant and lasting change in the statistical distribution of

weather patterns over periods ranging from decades to millions of years. It may be a

change in average weather condition or the distribution of events around that average.

(internet: Wikipedia).

32

The term sometimes is used to refer specifically to change caused by human activity.

In the context of environmental policy, climate change has become synonymous with

anthropogenic global warming.

Factors that can shape climate change are called climate forcings or forcing

mechanisms. It can be either internal or external. Internal are natural mechanisms,

while external can be natural or anthropogenic.

Janet.(2012), investigated five things to know about flooding and climate change. In

the study, the author came up with the following:

1. A warmer atmosphere holds more moisture.

This means that with more water in the atmosphere, the volume of rainfall may

increase when it does pour.

2. Evidence of heavier rainfall in the past is limited but growing.

Extreme events are rare, and detecting trnds outside natural variability requires

decades of continuous observations. A recent study finds greenhouse gas emissions

contributed to observations of more intense precipitation over two thirds of the

northern hemisphere between 1950-2000.

3. Attributing specific events like flooding to climate change is tricky.

In general, scientists are wary of attributing specific extreme events like flood to

climate change because it is impossible to say whether an event would have happened

if global temperatures weren’t increasing. A recent study found although the precise

human contribution to widespread flooding is difficult to pinpoint, global greenhouse

gas emissions increased the risk of flood.

33

4. Scientists predict that heavy rainfall will increase in the future.

The author further indicated that flooding occurs in number of ways, and each

may be affected by climate change. Surface water flooding occurs when heavy

rainfall can’t absorb into the ground or drain away. River flooding closely

linked to surface flooding, occurs when streams burst their banks. Coastal

flooding results from high tides, storm surges and sea level rise. Rising sea

levels present a clear threat to flood coastal areas.

5. Flooding isn’t just about rainfall, other human factors contribute

too.

Flooding and extreme precipitation go hand in hand, but they are not the same

thing. While climate change may directly alter precipitation, flooding is a

consequence of heavy rainfall which also have a human component. The rising cost of

damages associated with flooding is a perfect example.

Changes in land use, such as building houses on floodplains and paving over natural

surfaces are making people more vulnerable to flooding.(Freya and Roz 2012).

Rise in sea level resulting from climate change leads to flooding in the coastal

communities, Flood displaces farmers and fishermen in coastal areas. All the littoral

communities are the most vulnerable to natural flood disasters. It leads to

environmental refugees as some communities are made to forcefully evacuate their

homes or place of economic activities. Floods are the most common of natural

hazards that can affect people, infrastructure and the natural environment.

However, Riverside floods are the most prevalent, due to heavy, prolonged rainfall,

rapid snowmelt in upstream water sheds, or the regular spring thaw. Other floods are

caused by extremely heavy rainfall occurring over a short period in relatively flat

34

terrain, the backup of estuaries due to high tides coinciding with storm surges, dam

failures, and dam overtopping due to landslides.

3.9 FLOOD AND REMOTE SENSING

Goosby,(2010),examined Geotechnologies for Hazard Mapping. He identified that

Remote Sensing is a technique used to collect data about the earth without taking a

physical sample. A sensor is used to measure the energy reflected from the features of

interest. National Oceanic and Atmospheric Administration (NOAA). Remote sensing

supports hazard mapping like flood plains as used in this study.

Mike hydrological model depicts flood inundation that could result from rainfall, dam

or levee failure, and storm surge.

The Most tsunami model simulates the flood inundation that could occur from an

earthquake generated tsunami.

Samadi and Delaver (2011), investigated the Applications of Spatial Data

Infrastructure in Disaster Management. They stated that there are substantial problems

with availability of, and accessibility to reliable up-to-date, and accurate geospatial

data. The need for such data is significant if one is to successfully react to and manage

a disaster situation like flood, etc.

The study focuses on the use of spatial data infrastructure and geospatial information

system to achieve better outcomes for site selection of rescue centers (237 Adobe

Acrobat Document).

It is impossible to define the entire flood potential in a given area. But through remote

sensing data, the evidence for potential flood situations can be found or inferred. The

most obvious evidence of a major flood potential outside of historical evidence, is

identification of flood plain or flood- prone areas which are generally recognizable on

remote sensing imagery.

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3.10 FLOODPLAINS

Floodplains are land areas adjacent to rivers and streams that are subject to recurring

inundation. Owing to their continually changing nature, floodplains and other flood –

prone areas need to be examined in the light of how they affect or are affected by

development.

Flooding is a natural and recurring event for a river or stream. Statistically, streams

will equal or exceed the mean annual flood once every 2 – 33years (Leopold et al,

1964). Flooding is a result of heavy or continuous rainfall exceeding the absorptive

capacity of soil and the flow capacity of rivers, streams, and coastal areas. This causes

the watercourse to overflow its banks onto adjacent lands. Floodplains are, in general,

those lands most subject to recurring floods, situated adjacent to rivers and streams.

Floodplains are flood – prone and are hazardous to development activities if the

vulnerability of those activities exceeds an acceptable level.

Floodplains can be looked at from different perspectives: 'To define a floodplain

depends on the goals in mind. As a topographic category it is quite flat and lies

adjacent to a stream; geomorphologically, it is a landform composed primarily of

unconsolidated depositional material derived from sediments being transported by the

stream; hydrologically, it is best defined as a landform subject to periodic flooding by

a parent stream. A combination of these [characteristics] perhaps comprises the

essential criteria for defining the floodplain" (Schmudde, 1968). Most simply, a

Flood-plain is defined as "a strip of relatively smooth land bordering a stream and

overflowed at a time of high water" (Leopold et al, 1964). Floods are usually

described in terms of their statistical frequency. A "100-year flood" or "100-year

floodplain" describes an event or an area subject to a 1% probability of a certain size

flood occurring in any given year. The flood season is spring or early summer.

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3.11 LAND SURFACE CHARACTERISTICS RELATED TO FLOODS

(i) Topography or slope of the land, especially its flatness.

Geomorphology, type and quality of soils, especially unconsolidated fluvial

deposit base material.

(ii) Hydrology and the extent of recurring flooding and

(iii) Development.

These characteristics are commonly considered in natural resource evaluation

activities (OAS, 1984). In order to evaluate flood hazard, the researcher needs to

know:

(i) Where the floodplain and flood – prone areas are,

(ii) How often the floodplain will be covered by water,

(iii) How long the floodplain will be covered by water,

(iv) At what time of the year flooding can be expected.

3.12 FREQUENCY OF FLOODING

Generally, only annual floods are used in a probability analysis, and the recurrence

interval – the reciprocal of probability is substituted for probability. In some climates,

several years of intense flood activity are followed by many years in which few floods

occur. The floodplain may be developed and occupied during the years with the least

flood activity.

As a result, this development is subject to the risk of flooding as the cycle of flooding

returns. Deforestation and intensive crop production may drastically change run off

conditions, thereby increasing stream flow during normal rainfall cycles and thus,

increasing the risk of flooding. On small streams, floods induced by rainfall usually

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last for only a few days, but on large rivers flood, runoff may exceed channel capacity

for a month or more.

3.13 TYPES OF FLOODING

Floods are categorized into natural and artificial floods in terms of their specific

causes.    Flood is basically a natural hydrological phenomenon. Its occurrence is

usually the aftermath of meteorological events. These include an intense and

prolonged rainfall spells unusually high coastal and estuarine waters due to storm

surges, seiches, etc. Floods are also caused, indirectly, by seismic activities. Coastal

areas are particularly susceptible to flooding due to tsunamis (seismic sea waves).

Sinking of land due to earthquakes reduces the elevation of land areas. In the vicinity

of lakes and rivers, these areas become flood-prone. Likewise, the uplifting of lake

and river beds from seismic causes sometime results in the overflowing of these

bodies of water. The water then inundates the surrounding and adjacent areas. To a

certain extent, astronomically influenced phenomena such as high tides coinciding

with the occurrence of heavy rainfall frequently cause flooding.

(I) RIVER FLOODING

Flooding along rivers is a natural and inevitable part of life. Some floods occur

seasonally during winter or spring, coupled with melting snow, fill river basins with

excess water too quickly. Torrential rains from hurricanes or tropical systems can also

produce river flooding.

(II) COASTAL FLOODING

Winds generated from tropical storms and hurricanes or intense offshore low pressure

systems can drive ocean water inland and cause significant flooding. Escape routes

can be blocked off and blocked by high water. Coastal flooding can also be produced

38

by sea waves called tsunamis, sometimes referred to as tidal waves. These waves are

produced by earthquakes or volcanic activity. It is caused by severe sea storms.

(III) HUMAN – INDUCED FLOODING

Occasionally, floods occur unnaturally. These are usually the result of human

activities. Such activities include:

(i) Blasting: This causes landslides in the slopes of hills and mountains which

may result in the unintentional damming of rivers and streams.

(ii) Construction of Temporary dams : This produces an impediment to the flow

of a river or stream which then results in an overflow;

(iii) Failure of hydraulic and other control structures: Accidents like the

breaking of a dike result in the entry of an enormous quantity of water in a

protected area; and

(iv) Mismanagement of hydraulic structures: Control structures like dams which

are utilized for various purposes are usually operated according to what is

known as an "operation rule" and mismanagement which results in the

violation of the rule may necessitate an untimely and sudden release of large

amounts of excess water.

While not quite so obvious, human activities that tend to alter the ecological system in

a river basin will have an impact on the hydrology of the catchment. This could, in the

future, result in frequent floods. Foremost among such activities is the denudation of

forest and watershed areas.

Flood can be human-induced through human activities which include building on

water ways, wet land reclaiming, lack of drainage systems, inadequate maintenance of

existing drainage systems and blockage through dumping of refuse when there is

rainfall.

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IV URBAN FLOODING

As land is converted from fields or woodlands to roads or parking lots, it loses its

ability to absorb rainfall. Urbanization increases runoff 2 to 6 times over what would

occur on natural terrain. During periods of urban flooding, streets can become swift

moving rivers, while basements can become death traps as they fill with water. In a

minor flooding, inundation may or may not be due to overbanking. When there is no

bank overflow, flooding is simply due to the accumulation of excessive surface run-

off in low lying flat areas. Floodwaters are usually confined to the flood plain of the

river along the channel, on random low-lying areas and depressions in the terrain.

Floodwater is usually shallow and there may not be a perceptible flow.

(V) MUDDY FLOODING

Muddy flood is produced by an accumulation of runoff generated on cropland.

Sediments are detached by runoff and carried as suspended matters. It is more likely

detected when it reaches inhabited areas. Muddy floods are therefore, a hill slope

process.

(VI) FLASH FLOODING

Flash flooding is often the result of rapid, unplanned urbanization, which can greatly

reduce the land’s ability to absorb rainfall. The resulting runoff has nowhere to go and

accumulates as quickly as the rain can fall (Coppola, 2011). Flash floods from

torrential rains wash away thousands of hectares of farmland and Dams, houses and

market places collapse by flooding. School buildings and bridges also collapse

A flood caused by heavy or excessive rainfall in a short period of time, generally less

than 6 hours. Flash floods are usually characterized by raging torrents after heavy

rains that rip through river beds, urban streets, or mountain canyons sweeping

everything before them. They can occur within minutes or a few hours of excessive

rainfall. They can also occur even if no rain has fallen, for instance after a levee or

40

dam has failed, or after a sudden release of water by a debris or ice jam. (MRX

Webmaster 2010),the Gis tool was used to select the area where the slope is less than

10m as lowest slope area, area fallen within the defined 100m buffer zone away from

river and the land use is either Built up area or Farm land. All the combined parameter

must be truth in the catchment area

Several factors contribute to flash flooding. The two key elements are rainfall

intensity and duration. Intensity is the rate of rainfall, and duration is how long the

rain lasts. Topography, soil conditions, and ground cover also play an important role

(United States Search and Rescue Team – Internet). Flash flood results from

convective precipitation (intense thunderstorms).

3.14 CAUSATIVE FACTORS OF FLOODING

Flood is too much water in the wrong place whether it is an inundated city or a single

drain. Generally, some of the mechanisms that trigger flood are dam or levee failure,

more rain than what the landscape can dispose of, the torrential rains of hurricanes,

tsunamis, ocean storm surges, rapid snow melts, ice flows blocking a river and burst

water mains. Flood is too much water in the wrong place whether it is an inundated

city or a single drain.

In general, man activities that cause flood include:

(i) Farming and deforestation that exposes the soil to erosion and increases runoff,

(ii) Urbanization by reckless building in vulnerable areas without regards to town

planning regulations, poor watershed management and failure to control the

flooding promptly

(iii) River channels that block or narrow river channels.

Naturally flood could be due to a high water table in an area, topography (low-land

close hills), and low infiltration such as clayed soil.

41

Damon (2011) examined International Disaster Management and posited the

following as the identified causes of flood:

(a) Deforestation: This is the act of cutting down or burning the trees in an area.

Soil once anchored by vegetation quickly turns to runoff sediment which is

deposited into drainage systems such as rivers and streams, decreasing their

holding capacity. As sediment builds up, successive floods occur more rapidly.

The water retention capacity of soil anchored by vegetation is greater than that

of deforested land, leading to greater overall amounts of runoff that ultimately

results from deforestation (Coppola, 2011).

(b) Heavy and Torrential Rainfall: This is any rain that pours down fast,

violently or heavily (Eschelbach, 2007). Torrential rain falls ceaselessly for

hours and sometimes days. It results in disastrous flooding of low - lying areas.

Torrential rain is the immediate trigger of flood, and it is natural.

(c) Construction of buildings along floodplains and river banks: Citing and

growth of villages and rural communities either at the foot of the hills or also

along river banks are part of human activities that cause flooding.

Developments in urban floodplains

Blocking the water ways/ river paths/ floodplains: This is a situation in which

indiscriminate disposal of both domestic and industrial wastes are used to block the

water ways (Actionaid, 2011).

(a) Storm Surge: This is unusual volumes of water flowing onto shorelines.

Storm surges cause flooding through the blockage of the outfalls of

drainage systems.

3.15 LITERATURE GAPS

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From the above, many studies have been carried out on flood. This gaps identified

include the lack of use of Geographic Information System to identify the areas that are

likely to have more effects of flood disaster than others. Also, the level of effects was

not defined as it affects the areas under the various studies in this literature review.

From the studies examined in the literature review is that how distressed families

resettle and cope after flood disasters were not adequately addressed, whether they

resettle into the same exposed and vulnerable areas is also not looked into, nor is

anything usually done to reduce the vulnerability of the affected communities.

Again, most of the studies neglected environmental protection for sustainable

development. It is a serious gap, hence this study, which will help to enhance social

protection integration into development planning by relevant authorities.

Therefore, this research examines the level of effects of flood disaster on Ngwo Udi

Local Government Area, Enugu State, using, Global Positioning System and

Geographic Information System to identify the areas prone to future flood disaster,

and to determine the level of effects in the affected communities..

CHAPTER FOUR

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THE STUDY AREA

4.1 GEOGRAPHICAL FEATURES

Ngwo is situated on the edge of the escarpment immediate to the west of Enugu

Metropolis. A great part of the latter is in fact, built on land originally owned by

Ngwo. Enugu has a population of approximately six hundred thousand, seven hundred

(600,700). The study area is part of Enugu metropolis, located between latitude 6°22' -

6°28’ North and longitude7°26' - 7°37' East. It is the High plains of Igboland, Eastern

Nigerian Region. It is part of the Enugu Capital Territory and center of commercial

activities in the state (Enugu North). Ngwo’s boundaries with its neighbours are very

indefinite and are indicated by no natural features. The neighbours consist of Abor

and Nike on the North and East, Nsude on the South and Eke on the West. Below is a

list of all the villages in Ngwo and three figures showing Nigeria, Enugu state map

indicating Udi Local Government Area and the last map showing the geographical

location of Ngwo which is the study area.

4.2 VILLAGES IN NGWO

(i) Ameke

(ii) Amankwo

(iii) Uboji

(iv) Okwojo

(v) Amachalla

(vi) Ukaka

(vii) Amaedo

(viii) Umuasse

(ix) Etiti

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Figure 4.1: Map of Nigeria showing Enugu state

Source: www.ng.org, April, 2013.a

45

Figure 4.2: Map of Enugu State showing Udi Local Government Area

Source: Fieldwork, Google Earth, April, 2013.

46

Figure 4. 3: Map of Ngwo, the study areas

Source: Google Earth, April, 2013.

4.3 PHYSICAL FEATURE

The land owned by the clan is situated mainly on the top of escarpment which is about

1,200ft above sea level, and consists of undulating grasslands practically devoid of all

other forms of vegetation, except in areas immediately surrounding the villages. The

soil is light and sandy with low fertility. The clan did possess land at the foot of the

escarpment but the greater part of the land has been enveloped by Enugu urban.

However the clan is very short of good farming land, therefore, some Ngwo citizens

rent land from Nike for this purpose. Ngwo obtains its water supplies from the

47

following rivers: Iva, Ekulu and Asata on the East, and the Ajali on the West and

rainfall. The rain starts in the later part of April and end in November with a short dry

spell.

4.3.1 Soil

The texture of a soil in any drainage basin is defined by the relative proportion of

sand and clay present in the particule size analysis (Todd,1980).this is because

unconsolidated geologic materials are usually classified according to their particular

size distribution The study carried out in Ngwo Shows that the soil type of Ngwo is

mainly sandy loam . Loam is soil composed of sand, silt, and clay in relatively even

concentration (about 40-40-20% concentration respectively). It can be generally said

that Ngwo soil is a fragile type.

4.3.2 The Drainage

The SRTM satellite data of Ngwo were obtained using arc-Hydro software to generate

the drainage areas where all the streams and the drain basin covering the all study area

were generated .Some hydrological data on runoff characteristics were generated as

well using Arc GIS software, such as stream, slope, and the contour showing the relief

of the area, all this data were derived from Shuttle Radar Topographic Mission

(SRTM) data gotten from satellite imageries.

4.3.3 Topography

The average slope of Ngwo terrain feature was conveniently calculated from contour

lines on a topographic map. A slope map is typically created by GIS analysts. It was

created with elevation data (SRTM), which, in many cases, does not provide the detail

or currency needed for accurate slope analyses. The average slope of Ngwo hill was

determined using a topographic map.

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4.4 HISTORY

Ngwo clan is one of the six clans that make up Udi Local Government Area in Enugu

state. Ngwu Ako, the ancestor of Ngwo had two wives, the first wife who hailed from

Ojebe Ogene, begot three sons- Uboji, Ameke and Amankwo. The second wife begot

seven sons namely, Enugu, Etiti, Amachalla, Okwojo, Ukaka, Amaebo and Umuasse.

She was from Akegbe. Very little information could be obtained as to Ngwo’s early

history. All the villages meet yearly to make sacrifice to this ancestor, and a festival

known as the Nkwa Feast is held. This festival is held at a place known as Okpoto

Ngwo, where their ancestor is supposed to have lived. OkpotoNgwo is at about mile

seven on the Enugu – Onitsha road. The history was unable to state where this man,

Ngwo Ugwu Ako originated. History has it that Ngwo appeared to have fought wars

with all its neighbours, particularly Nike community.

4.5 SETTLEMENT PATTERN

Ngwu Ako the father of the ten sons mentioned above shared his assets into two parts.

To the first three sons he gave his home land which he called Ngwo Uno. And to his

seven sons from the second wife he gave plain land known as Ngwo Eguru. This is

why Ngwo has two broad sections of settlement, Ngwo Uno and Ngwo Eguru. Uboji

the first son shared home land settlement with his two brothers, Ameke and

Amankwo. Tgba Nkwa had what they called ‘’Ezi and Ibute’’. Ibute Uboji includes

Amokwe, Amadiukwu and Amagu, while Ezi consists of Uwani, Amuba and Amonu

The same thing is applicable to second wife’s seven sons. The first son shared their

own wealth and settlement with his six brothers all in order of seniority.

4.6 CULTURE

49

Ngwo as a clan has identical culture. Their cultures are as follows:

1. Igo Ani, Igo Ugwu, Igba Nkwa, Igo Akpu, Igo Chi

2. Masquerade; odo mgbugbu and odo akparakpa

3. Muo society

4. Ozo society

5. Marriage

6. Burial ceremonies

7. Naming ceremonies

8. Initiation to manhood

4.7 TRADITIONAL ADMINISTRATION

Ngwo is composed of ten villages each of which is administered by a council

composed of elders and holders of title known as “Nze na Ozo”. It appears that as a

general rule, each village manages its own affairs independent of its neighbours. But if

any serious difficulty presents itself, the village concerned calls upon the other sister

communities for assistance. Prior to 1930, Ngwo was administered by means of

Warrant Chiefs. They were appointed by the District Officer in consultation with the

people.

4.8 POPULATION

National Population Commission recorded that Udi Local Government Area, Enugu

State, has a population of 234,002, while Ngwo’s population was about 50,000. The

populations of the individual villages are not available.

4.9 ECONOMIC ACTIVITIES

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The major economy of Ngwo was based essentially on agriculture and related

activities. Peasant farming was the major economic activity of Ngwo. The major crops

they farm include yam, cocoa-yam, maize, vegetables. The natives also keep domestic

animals as poultry, goats, cows (efi igbo). They also trade on palm oil and palm wine.

Moreover, Okwojo Ngwo was known for craftsmanship precisely in blacksmith.

Amadiukwu and Uboji were also known to be good in blacksmith. They produce farm

implements such as hoes, diggers, axes and different kinds of domestic knives. There

were also people gifted in the making of mats, mortar, pestle, leather works and

carvings.

Trading is not left out. There were many Ngwo citizens who knew the trade routes of

Uburu and Afikpo where salt and beads were purchased. However, the trade pattern

changed with the discovery of coal. It turned the socio- economic activity of Ngwo

since 1915 when the first coal mine was established (Agu,1988).

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CHAPTER FIVE

METHODS AND PROCEDURE

5.1 TYPES AND SOURCES OF DATA

The data used in this study were collected from primary and secondary sources.

5.1.1 SECONDARY SOURCE

These include data obtained from published and unpublished sources. The

secondary data were collected from the following sources

1. The historical data of Ngwo was collected from National Archives in

Enugu.

2. Report of the flood disaster in Ngwo was collected from Relief and

Rehabilitation department, Enugu State Emergency Management

Agency.

3. Enugu landsat ETM satellite imagery was downloaded from Global

Landcover Facilities site.

4. The map of Nigeria, Enugu State and Ngwo were obtained from

www.motherland.com. Other maps were gotten through the satellite

imagery.

5. The Rainfall data of 2008, 2009,2010,2011 and 2012 of Enugu were collected

from climatologically return of meteorological department Oshodi, lagos.

The methods of the research are represented in the flow chart above to describe the

pattern for carrying out the research (figure 5.1). the flow chart is made up of five

steps: primary data, data processing, GIS criteria, derived parameters, final result

presentation. And the first layer consists of two main types of data: SRTM(Shuttle

Radar Topographic Mission) and Landsat Image Data. These were summarized,

52

processed and inputted for computation and processing. The following parameters

were derived; Landuse-land cover map of Ngwo,the Hydrological map showing the

drainage, the catchment area map, the slope map and the contour map showing the

relief of the terrain. The multi- criteria was applied using GIS technology to determine

the areas liable to flood in Ngwo.

Figure 5.1 Flow Chart Method

Source: Fieldwork, April 2013

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5.1.2 Primary Data

5.1.2.1 Global Positioning System and Geographic Information System data

GPS and GIS were used in the study for spatial data collection. This research was

carried out with the intention of producing a highly reliable result, and hence,

adequate attention was paid into the various stages of the work.

The data acquired using these instruments for this study were:

(i) Existing landssat satellite imagery 2008 of the Ngwo was downloaded from the

Global Landcover Facilities site, United States (GLCF), with radiometric

resolution of 30m.

(ii) A Shuttle Radar Topography Mission (SRTM) satellite data of the same area

with 90m resolution was obtained from University of Nigeria, Enugu campus.

The primary data source of use in this study is the Digital Elevation Model

(DEM) of the Shuttle Radar Topography Mission (SRTM) elevation data

which were obtained by a specially modified radar system that flew onboard

the Space Shuttle Endeavour during an 11 day mission on February, 2008. The

SRTM project is a collaborative effort by the National Aeronautics and Space

Administration (NASA), the National Geospatial- Intelligence Agency of the

U.S. Department of Defense (NGA), as well as the German Aerospace Center

(DLR) and the Italian space Agency (ASI).NASA’s jet propulsion laboratory

(JPL) managed the mission and the Earth Resources Observation and science

data center of the USA. Geological Survey (USGS EROS Data Center) has the

responsibility of hosting, distributing and archiving the final SRTM data

products. A general description of the SRTM mission can be found in Faar and

Kobrick (2000).

iv. Coordinates of different locations in the study area were obtained by the

use of GPS using the WGS84 32N Minna datum.

54

ETM satellite imagery was downloaded to get the following parameters for flooding

areas:

(i) Topographic map which involves the contour, slope and Dtu-Relief.

(ii) Hydrological information – precipitation, drainage, catchment areas and Water

flows.

(iii) Land use Land cover - feature of the area:

(a) Built-up areas

(b) Forest

(c) Farmland

(iv) Soil type

5.1.2.2 Interviews

Interviews were conducted in Ngwo communities as source of additional information

and the features found on the map and image verified on the ground. Some of the

affected individuals and families were orally interviewed face to face. Some of the

community leaders were also interviewed to collect information on the impact and

consequences of flood on the affected communities and their environment. The

information obtained include the causes of flood in the communities, the

consequences they suffer as a result of flood and the likely means to abate the

situations. During this oral interview, things communities can do as active

participation in checking the flood and reducing its impact were discussed. Data

collected from this source were used to validate data collected from other sources.

5.1.2.3 Field Observation

Observation method: Personal observations were made of how flood have been

occurring in various parts of the study area. These include the type of flood the

55

communities experience, the likely causes of the flood and the areas the flood has

likely affected their living environment (soil, farm, transport, market, education,

health, etc). The aim of the personal observation is to assess the level of flood

encountered in the areas selected and the extent to which the flood affects them in

their environment. The data from this source were used to check and confirm data

collected from other sources.

5.1.2.4 Questionnaire Method

Questionnaires were used greatly in the study to collect large volume of primary data.

Questionnaire method helped in getting the likely

5.2 SOFTWARE MATERIALS USED FOR DATA COLLECTION

(i) Laptop computer was used to process the whole data.

(ii) Arc GPS software was used for hazard data collection and mapping on flood

coverage areas.

(iii) Illwiss software was used for image processing and classification.

(iv) Satellite imagery and SRTM (Shuttle Reader Topographic Mission) data was

used to produce landuse/land cover and generate the slope of the terrain.

(v) (v)Hand-held GPS was used for field observation to capture the coordinate

of the actual locations affected by flood at Ngwo.

5.3 GIS CRITERIA TO DETECT THE AREAS PRONE TO FLOOD

Each criterion was evaluated using a different set of data, at an appropriate scale and

with a specific model for most of the criteria, spatial analysis procedures using GIS

raster calculation were an important part of the evaluation process. Evaluation of the

flooding criterion gives a good example of the processing complexity neede to obtain

56

representative values of the area prone to flood over the studied area.GIS multi criteria

analysis in this study is the process of detecting some phenomenon

Base on the factor that affects it. In this process many arithmetic and logical

expression were used. It has been find out that there is major, minor and flash flood.

To detect differently the area that has been affected by flood in the study area, the

researcher need to know the parameter that determines each of the type of flood. The

mathematical operations required to detect the flooding area in the study area hane

been realized with ARC GIS

The Raster calculation tools was used to enter the parameter. Once the necessary

database is developed and organized, computations can be carried out in a few minute.

The system passes through the combination of data (Raster) and select where the

criterion is truth.

5.4 SURVEY

Both large and small populations were studied by selecting and studying samples

chosen from the populations to discover the relative incidence, distribution, and

interrelations of sociological and psychological variables. The research was based on

the accurate assessment of the characteristics of whole populations of Ngwo. Samples

drawn from the population were studied. Interviews, field observation and

questionnaires were used in the survey.

The list containing all the flood victims in Ngwo’s 2010 flood was collected from

Enugu State Emergency Management Agency (ESEMA).

5.5 SAMPLE POPULATION AND SAMPLE SIZE.

According to National Population Commission (2006), Ngwo’s population was about

50,000. This forms the sample frame for the study. To determine the sample size, the

Taro Yamane formula was used.

57

N= N/1+n (e) 2

N = sample population

n = sample size

e = level of significance

1 = constant

Therefore, N = 50,000/1+50,000(0.05)2

= 396, 83.

Approximately 400

N = 400 respondents

Therefore, a sample of 400 respondents was surveyed in the study Sample frame.

Meanwhile, five communities / villages were randomly selected for this study. They

include Okwe–Amankwo Ngwo, Ibite- Ameke Ngwo, Amokwe, Uboji, Akama and

Uwani Uboji.

5.6 SAMPLING TECHNIQUE

The Stratified Sampling Technique was applied in this study to group the

communities / villages according to their densities: high, medium and low densities

(See table 5.1). Simple random sampling was used to select streets from the villages

and the individual respondents

58

Table 5.1: ARRANGEMENT OF STRATA.

STRATUM I STRATUM II STRATUM III( High ) ( Medium ) ( Low )

IbiteAmekeAmankwoUboji

OkwojoAmaaborEtitiEnugwu Ngwo

AmachalaNgwoAsaaUmuassee

Source: Fieldwork, April 2013.

Two villages each were taken from the high and medium densities, and one village

was taken from the low density villages. However, there was no stipulated number

attached to each of the villages in the last 2006 population census. The high density

villages/communities were assigned ratio 3 because it is agreed they are up to three

times higher than other areas. The medium density is assigned 2, and the low density

has 1 because it is the smallest. That is the ratio of 3:2:1.

Table 5.2: DISTRIBUTION OF SAMPLE SIZE BY RATIO

VILLAGES RATIO SAMPLE SIZE (400)

HIGH

MEDIUM

LOW

Ratio 3

Ratio 2

Ratio 1

3/6 % 400 = 200

2/6 % 400/100 = 133

1/6 % 400/100 = 67

TOTAL 400

Source: Fieldwork, April, 2013.

59

There was an application of Simple Random Sampling technique to select the

communities to be administered with questionnaire. Random picking of communities

was done by assigning numbers 1 to N on N Identity Card and the numbers were put

in a container and reshuffled thoroughly each time before any number was drawn.

Table 5.3: COMMUNITIES IN THE SELECTED VILLAGES.

VILLAGES DENSITY COMMUNITIES

Ibite – Ameke High Umueze-ani, Ifueke, 9th mile,

Ibite, Amankwo

Uboji High Amadi – Ukwu, Ama-onu,

Uwani, Amokwe, Amuba,

Amagu.

Okwojo Meddium Etiti, Okwe, Akama, Okunito.

EnugwuNgwo Medium Amaebor, Eke Odido, Amaedo

Umuasse Low Ukaka, NgwoAssa

TOTAL 25

Source: Fieldwork, April, 2013.

60

Table 5.4: DISTRIBUTION OF SAMPLE SIZE IN THE VILLAGES

ACCORDING TO COMMUNITIES.

VILLAGES COMMUNITIES SAMPLE SIZE

DISTRIBUTED

TOTAL SAMPLE

DISTRIBUTED

Ibite - Ameke Umueze – ani

Ifueke

9th mile

Ibite

Amankwo

25

22

25

24

24

100

Uboji Amadi – Ukwu

Ama – onu

Uwani

Amuba

Amagu

Amokwe

23

20

20

17

10

10

100

Okwojo Etiti

Okwe

Akama

Okunito

24

22

20

19

85

EnugwuNgwo Amaebor

Eke Odido

Amaedo

23

25

27

75

Umuasse Ukaka

NgwoAssa

18

22

40

TOTAL 25 400 400

Source: Fieldwork, April, 2013.

The relative frequencies were considered in the frequency distribution of x2.

61

5.7 DISCRIPTION OF INSTRUMENTS FOR DATA COLLECTION

(QUESTIONNAIRE) II

The questionnaire was designed in such a way that the variables were identified. The

questions asked the respondents were in simple and clear languages. Majority of the

questions were close ended, except the questions on the likely causes of flood in the

area. The questions were arranged sequentially and logically. The questionnaire was

divided into two sections – personal data and relevant information on the factors

responsible for flood in Ngwo and impacts of the flood on human living, economic

activities, soil, houses, etc. Fifteen questions were asked and likely answers were

supplied in some of the questions, in which the respondents are expected to tick the

appropriate answers and fill in the other open ended questions. The data collected

were used to test the hypotheses.

5.8 DESCRIPTION OF STATISTICS USED IN THE ANALYSIS

Data collated was coded and analyzed with the aid of statistical package for social

sciences (SPSS) version 20. Descriptive statistics which includes frequency,

percentages, means and standard deviations were used to summarize the data and

answer the research questions. Spearman rho correlation was used in testing the first

hypothesis to determine if significant relationship exists between flood disaster

occurrence and the impacts. In the second hypothesis, ANOVA was used to determine

the significant difference among the communities in Ngwo as regards the impacts of

flood disaster. The third hypothesis was tested using factor analysis. P value less than

0.05 level of significance was considered significant. Results were presented in tables

and charts.

62

spearman’s rho correlation formula is as follows:

Where , is the difference between ranks?

ANALYSIS OF VARIANCE FORMULA

Where,

F = ANOVA Coefficient

MST = Mean Sum of squares due to Treatment

MSE = Mean Sum of squares due to Error.

Formula for MST is given below:

Where,

SST = Sum of squares due to Treatment

p = Total number of populations

n = Total number of samples in a population.

Formula for MSE is given below:

63

Where,

SSE = Sum of squares due to error

S = Standard deviation of the samples

N = Total number of observations.

Principal Component Analysis

Principal Component Analysis is a way of identifying patterns in data, and

expressing the data in such a way as to highlight their similarities and

differences. Since patterns in data can be hard to find in data of high

dimension, where the luxury of graphical representation is not available, PCA

is a powerful tool for analysing data. The other main advantage of PCA is that

once you have found these patterns in the data, and you compress the data, ie. by

reducing the number of dimensions, without much loss of information.

Listed below are the 6 general steps for performing a principal component analysis,

which we will investigate in the following sections.

1. Take the whole dataset consisting of d-dimensional samples ignoring the class

labels

2. Compute the d-dimensional mean vector (i.e., the means for every dimension

of the whole dataset)

3. Compute the scatter matrix (alternatively, the covariance matrix) of the whole

data set

4. Compute eigenvectors (e1,e2,...,ed) and corresponding eigenvalues

(λ1,λ2,...,λd)

5. Sort the eigenvectors by decreasing eigenvalues and choose k eigenvectors

with the largest eigenvalues to form a d×k dimensional matrix W(where every

column represents an eigenvector)

6. Use this d×k eigenvector matrix to transform the samples onto the new

subspace. This can be summarized by the mathematical equation: y=WT×x

64

(where x is a d×1-dimensional vector representing one sample, and y is the

transformed k×1-dimensional sample in the new subspace.)

5.9 VALIDITY OF INSTRUMENT

The validity of a measuring instrument is the extent to which the instrument measures

what it is intended to measure. Face validity on the other hand is achieved by

superficial examination of the instrument by experts, authorities or competent source

to ensure that the content of the instrument is truly asking the required questions to get

answers to the problem of the study. The researcher then based judgment on the

certification of the instrument by experts that it is actually measuring what it is

supposed to measure. The instrument was given to colleagues, lecturers and then the

supervisor. The resulting useful criticisms, corrections and additions made by these

experts further improved these instruments and increased their content validity.

5.10 RELIABILITY OF INSTRUMENT

A pilot study was conducted. Twenty questionnaires were administered and tested for

internal consistencies of responses using a measure of reliability called Cronbach’s

alpha.

The formula is as follows:

α = k (cov/var)

1+ (k−1) (cov/var)

Where K = Number of items on the survey

Cov = Average inter-item covariance

Var = Average item variance

1 = Constant

65

Ideally, in order to obtain a good estimate of the reliability of a survey, we split the

items into two groups and then compare these groups as if they were two separate

administrations of the same survey. This is called split-half test. This test is used

instead of test –retest technique to avoid bias. The result shows that the Cronbach’s

alpha coefficient for each of the split halves 1 and 2 are 0.782 and 0.816 respectively,

and the correlation between forms is 0.751, indicating a very strong reliability.

Therefore, the instrument is reliable for the study.

66

CHAPTER SIX

DATA PRESENTATION, ANALYSIS AND DISCUSSION OF FINDINGS

Findings from the study showed a significant rise in water level in the study area

thereby causing damage to lives and properties. This is consistent with Islam and Sabo

(2000), who noted that the quantity of water and rate of rise in water level influences

the damage caused by flooding.

Based on the findings, the major cause of flood in the area is inadequate drainage

system. Though other potential factors such as topography, buildings not according to

plan, high rainfall, Indiscriminate dumping of refuse, soil type and bad roads exists

but none of them is significant to cause flooding in Ngwo communities. Majority of

the people believe that development may have contributed to flooding in Ngwo. This

was in agreement with the study by Adetunji and Oyeleye (2013) on the Evaluation

of the Causes and Effects of Flood in Apete, Ido Local Government Area, Oyo State,

Nigeria. He found that blocking of drainage with waste has been responsible for flood

in the area. Similarly, findings from the study in Anambra state by Uche (2013), agree

that flooding occurs as a result of blocking of natural and manmade drainages and that

flooding is aided mainly by blocked channels and indiscriminate sand fling of coastal

swamp areas and natural drainage channel for urban development/constructions.

Halley (2001) also identified the major cause of flood in Africa to be inadequacy of

drainage system. He noted that flood usually occurs when there is a continuous

downpour of rain for a long period, while resulted excess water has capacity beyond

what available drainage can easily convey, due to its inadequacy or blockage of the

drainage.

The study revealed that flood occurs more often than not in a year, in Ngwo

communities. Majority of the people have lost properties such as houses, household

items and farms. In general, an average expected value of property loss to flooding in

the area was N2,175,847.7449. However, loss of lives as a result of flooding in the

67

area is on the barest minimum. A study done by Enaruvbe and Yesuf (2012), on flood

disaster in Delta State, revealed that farmlands, fish ponds and other social facilities in

the affected local communities were severely damaged by flood.

It was found out from the study that people of Ngwo are predominantly farmers and

traders, no wonder most of them reported that flood affects business activities in the

area. This is in line with Mmomi and Aifesehi (2013), who found that crop farming is

the major occupation of the people, thus the 2012 flood that submerged 65% of the

entire area had damaging effect on the people’s source of livelihood.

Results show that the sources of water supply in Ngwo is affected by flood. The

sources of water supply can be easily contaminated thereby causing an outbreak of

epidemic in the communities. People in Ngwo communities experienced diseases

after the flood. They include malaria, cholera, diarrhea and typhoid fever. This is in

consonance with Adelye and Rustum (2011), who found that during flooding water is

contaminated. Clean drinking water becomes scarce. Unhygienic conditions and

spread of water-borne diseases result.

Findings from the study also reveals that flooding has caused to a high extent damages

to markets, buildings/household items, roads, recreational facilities, farm crops,

soil/farm lands, school buildings and economic trees. However, it has to a low extent

caused damages to source of water supply apparently because majority of the people

in Ngwo communities use pipe borne water supply. Damages to electrical installations

were also low as well as severe health hazards and loss of lives which is very low.

According to Olorunfemi and Raheem (2013), flooding and rainstorm, apart from

causing destruction to lives and properties often cause significant damage to

livelihood systems of the victims. The incident generally caused disruption of

electricity in some areas for months affecting trading and crops washed away on

farms, especially among those in the suburban. Furthermore, the disasters are

associated with a number of health problems including bodily injuries as well as the

attendant psychological trauma. Similarly Adetunji and Oyeleye (2013), found that

68

property loss was a major effect of flood in the area as many buildings were drowned

already. Others include loss of lives, economy loss, diseases outbreak, building

collapse and injury sustained.

The study reveals that since lack of drainage system is the major cause of flooding in

Ngwo communities, construction of drainage system remains the priority measure to

check flood in the area. Adetunji and Oyeleye (2013), similarly found that there is

need for repair and construction of new drainages. Construction of flood diversion

channels which involves the construction of artificial channels along main river

channels to divert part of the discharge during flood flows.

Moreover, the measures adopted in the area to cope after the flood are evacuation and

sensitization of the victims to prevent future occurrence. Others include proper waste

disposal, evaluation of victims, Individual assistance and community assisted projects.

Conversely, a study by Olorunfemi and Raheem (2013), revealed similarly that by and

large, support from friends and relatives and personal savings accounted for the way

large proportion of the victims cope with the immediate impacts of the disaster. They

noted that government’s help usually come late.

From the findings, a positive significant relationship was found between flood disaster

occurrence and associated flood disaster impacts. This implies that an increase in

flood occurrence increased the impact in the area. The impacts of flood disaster varied

across communities in Ngwo. Finally, three significant factors describing the patterns

of impacts were identified in Ngwo communities. The first is economic impact since

the flood damaged the farms and markets which served as their Major means of

livelihood. The second is Infrastructural impact which includes damages to roads,

health and recreational facilities, electrical installations, school buildings and sources

of water supply. The third is health impact which includes severe health hazards and

loss of lives. Abolade, Muili and Ikotun (2013), on Impacts of flood disaster in Agege

local government area Lagos, Nigeria, similarly identified an impact pattern in the

area to be economic, physical/infrastructural and Destruction of lives

69

6.1 LAND USE LAND COVER CLASSIFICATION

Supervised (full Gaussian) classification using the maximum likelihood algorithm in

ILWIS ACADEMIC 3.2 was used to generate three main land use land cover classes

of Ngwo from land sat image figure below: (1) Built up area, (2) Farm land and (3)

Forest were identified. These land use land cover classes were derived from images

2008 for Ngwo. This was due to the fact that the operator has familiarized herself with

the study area through dedicated field observation, whereby the spectra characteristics

of the classes in the sampled area has been identified. Ground truth information was

used to assess the accuracy of the classification. See table 6.1 and figure 6.1 and 6.2.

Table 6.1: Landuse Land Cover Classification Scheme of Ngwo

Source: Fieldwork, April, 2013.

70

CODE LAND USE/LAND COVER CATEGORIES

1 Built-up land

2 Farm land

3 Forest

Figure 6.1 Landsat Satellite Image Map of Ngwo

Source: Fieldwork, April, 2013.

71

Figure 6.2 Landuse Land Cover Map of Ngwo

Source: Fieldwork, (Handheld GPS) April, 2013.

In figure 6.2, the orange colour shows the built up areas, the purple is the farm land

and the green is the forest areas in Ngwo

72

Figure 6.3 Shuttle Radar Topography Mission

Source: Fieldwork, April, 2013.

The Drainage Areas

The SRTM satellite data of Ngwo was processed using arc Hydro software to generate

the drainage areas where all the streams and the drain basin covering the study area

were generated .Some hydrological data on runoff characteristics were generated as

well using Arc GIS software. They include stream, slope, and the contour showing the

relief of the area. All these data were derived from Shuttle Radar Topographic

Mission (SRTM) data gotten from satellite imageries.

The stream network layers distributed with the DEM (Digital Elevation Model) were

directly derived from the drainage direction layers. See figure 6.4 below. The flow

73

accumulation layer is used for selection and attribution. Only rivers with upstream

drainage areas exceeding a certain threshold are selected: for the 15 arc-second

resolution a threshold of 100 upstream cells has been used. The vectorized river

reaches are currently attributed with the maximum flow accumulation (in number of

cells) occurring within each river reach.

Figure 6.4: Hydrological Map of Ngwo Showing the Drainage Areas.

Source: Fieldwork, April, 2013.

The Catchment Area

The catchment area was generated with arc hydro using the stream segment. In this

process, the Catchment Grid Delineation function was used to create a grid in which

74

each cell carries a value (grid code) indicating to which catchment the cell belongs.

The value corresponds to the value carried by the stream segment or sink link that

drains that area, defined in the input stream segment link grid (Stream Segmentation)

or sink link grid (Sink Segmentation).

Figure 6.5: Hydrological Map of Ngwo Showing Catchment Areas

Source: Fieldwork, April, 2013.

THE SLOPESlope is the measure of steepness or the degree of inclination of a feature relative to

the horizontal plane. Gradient, grade, incline and pitch are used interchangeably with

slope. Slope is typically expressed as a percentage, an angle, or a ratio. The average

slope of Ngwo terrain feature was conveniently calculated from contour lines on a

topographic map. A slope map is typically created by GIS analysts. It was created

75

with elevation data (SRTM), which, in many cases, does not provide the detail or

currency needed for accurate slope analyses. The average slope of Ngwo hill was

determined using a topographic map. Slope in Ngwo can be given in two different

ways, a percent gradient or an angle of the slope. The initial steps to calculating slope

either way are the same. The slope of Ngwo terrain was generated and categorized

into two classes (low slope and high slope) as shown in figure 6.6 below:

The areas in green fall within the low slope, while those in red are in the high slope

category.

Figure 6.6: Hydrological Map of Ngwo Showing Slope Rank. Source: Fieldwork, April, 2013.

SOIL TYPE

The texture of a soil in any drainage basin is defined by the relative proportion of sand

and clay present in the particle size analysis (Todd, 1980).This is because

unconsolidated geologic materials are usually classified according to their particular

76

size distribution. The study shows that the soil type of Ngwo is mainly sandy loam.

Loam is soil composed of sand, silt, and clay in relatively even concentration (about

40-40-20% concentration respectively). The sandy loam soil is well drained and

aerated and workable for most of the year. It is very light to handle and quick to warm

up in spring. Unless it has very high organic matter content, it is prone to drying out

too quickly, and additional watering will be needed. This extra watering will also help

to wash out the plant foods and lime from the soil, so is likely to be acid (except for

some coastal soils).this contributes in making source of water supply polluted

whenever there is flood in Ngwo. They are often referred to as hungry soils and need

lots of extra feeding, with careful management. However, they can be amongst the

most productive soil types (World Soil Forum, 1998). Soil profile characteristics

determine whether groundwater reaches soil surface, or not. The evolution of soil

structure after flooding mainly depends on the quality of flood water (e.g. salinity,

sodicity, type of sodium salt, etc.) (Lavado and Taboada, 1988). It is important to

determine the origin of flood water, which in about 90 % of cases comes from

groundwater. The diagram in Figure 3.9 shows the possible consequences of different

kind of water qualities on soil structure. Soil pending or flooding by fresh water does

not cause severe consequences; except those related to the loss of soil bearing

capacity.

77

6.3 MAJOR FLOOD AREAS

Major flood is caused by the overflowing of rivers and lakes; by serious breaks in

dikes, levees, dams and other protective structures; by uncontrollable releases of

impounded water in reservoirs and by the accumulation of excessive runoff.

Floodwaters cover a wide contiguous area and spread rapidly to adjoining areas of

relatively lower elevation. In this case the GIS tool (Raster), was used to define the

areas that fall within 100m buffer zone away from river channels or any drainage area;

the selected land use must be either built up area or Farm land area. The digital terrain

model was used to define the area where the elevation is less than 300m as low

terrain. The system developed a computation which results to the map of major Flood.

The figure below shows the area liable to the major flood in Ngwo. They include Iva

valley coal mine (Enugwu Ngwo), 9th mile corner (Okwe, Etiti and Ameke).

78

Figure 6.8: Map of Ngwo showing major flood

Source: Fieldwork, April, 2013.

6.4 MINOR FLOOD AREAS

The minor flood is a flooding resulting in minimal or no property damage but some

public inconvenience. This type of flood occurs in low lying area or flat area. The GIS

tool was used to define 100m zone buffer away from the river or any drainage area

where the flooding criteria must exclude , the selected land use must be either built up

area or Farm land area where the land is victim of anthropogenic factor. All the

combined parameter must be truth in the catchment area; the digital Elevation model

was used to define the area where the elevation falls between 300m to 400m as the flat

terrain. The Raster Calculator tool in map algebra box in arc GIS 10 was used to

define the criteria. The system developed a computation which results to the Minor

79

Flood map. The figure below shows the area liable to minor Flood in Ngwo (Enugwu

Ngwo, Ameke, Iva valley coal mine, Okpara coal mine and Okwe(9th mile).

Figure 6.9: Areas Prone to Minor Flood in Ngwo.Source: Fieldwork, April, 2013.

80

Flash Flood criteria

The Raster Calculator tool in map algebra box in Arc GIS 10 was used to define the

criteria. The system developed a computation which results to the Flash Flood map.

The figure below shows the area liable to Flash Flood in Ngwo.

Figure 6.10: Areas Prone to Flash Flood in Ngwo.

Source: Fieldwork, April, 2013.

81

The flooding of drainage channel following heavy rainfall is the most common form

of flooding in Ngwo. The most common flood in that area of study is either major in

abundant rain fall or minor in normal rain .An overflow of water onto normally dry

land. The inundation of a normally dry area caused by rising water in an existing

waterway, such as a river, stream, or drainage ditch, ponding of water at or near the

point where the rain fell. Major flooding is a longer term event than flash flooding: it

may last days or weeks. In hilly areas of the communities, as well as in rivers draining

areas, flooding can occur more quickly and they are often flash flood. Flash flooding

usually results from relatively short intense bursts of rainfall, commonly from

thunderstorms. This flooding occurs in any part of Ngwo, but is a particularly serious

problem in high density areas where drainage systems may not cope and in very low

lying areas and streams. Flash floods tend to be quite local and it is difficult to provide

effective warning because of their rapid onset. In this study, GIS provide a significant

tool to detect the flood disaster in Ngwo. Figure 6.9 below shows the pattern of

flooding in Ngwo. The entire ten villages in Ngwo are prone to flash and minor flood,

but 9th mile corner (Okwe,Ameke), Iva valley (Enugwu Ngwo, Uwani Uboji) are the

areas identified to be prone to major flooding.

82

Figure 6.11: The Flash, Minor and Major Flood Areas in Ngwo.

Source: Fieldwork, April, 2013.

83

6.5 ANALYSIS OF SOCIAL SURVEY

Table 6.2: Demographic Characteristics of the Respondents

Frequency

n = 353

Percent

(%)

Sex

Male 194 55.0

Female 159 45.0

Occupation

Trader 118 33.4

Farmer 75 21.2

Civil servant 112 31.7

Artisan 13 3.9

Transporter 16 4.5

Student 16 4.5

Businessmen 3 0.8

Table 6.2 shows that 194 (55.0%) of the respondents are males while 159 (45.0%) are

females. It also reveals that 118 (33.4%) of the respondents are traders, 75 (21.2%) are

farmers, 112 (31.7%) are civil servants, 13 (3.9%) are artisans, 16 (4.5%) are

transporters, 16 (4.5%) are students while 3 (0.8%) are business men /women.

84

Yes96%

No4%

Figure 6.12: Occurrence of flood

Source: Fieldwork, April, 2013.

Table 6.3 Frequency of occurrence of flood

Frequency Percent

Several times in a year 123 36.3

Few times in year 101 29.8

Not often 115 33.9

Table 6.3 shows that 123 (36.3%) of the respondents reported that floods occur in

their locations several times in a year, 101 (29.8%) said few times in a year, while 115

(33.9%) of them said not often.

85

Yes71%

No29%

Figure 6.13: Loss of property as a result of flooding

Source: Fieldwork, April, 2013.

Figure 6.11 shows that 250 (70.8%) of the respondents have lost property as a result

of flooding while 103 (29.2%) have never lost any property as a result of flooding.

Table 6.4: Type of property lost in floods

Type of property Frequency Percent

House 52 20.8

Household items 160 64.0

Farms 98 39.2

Table 7 shows that out of 250 respondents who have lost property in flood, 52

(20.8%) lost their houses, 160 representing 64% of the 250 people lost household

86

items while 98 of them constituting 39.2% of the 250 people lost farms. The minimum

and maximum expected value of property lost by a household to flooding in the area

was N7000 and N15,000,000 respectively, while the average expected value of

property lost to flooding in the area was N2,175,847.7449.

Yes16%

No84%

Figure 6.14: Has any life been lost as a result of flood in your community.

Figure 6.14 shows that 58 (16.4%) of the respondents reported that lives have been

lost in their communities as a result of flood in the area while 295 (83.6%) said no

lives have been lost. A minimum and maximum of 1 and 11 lives respectively was

lost, while an average of 2 lives was lost in the flood.

87

Table 6.5: Type of diseases experienced after the floods

Diseases Frequency Percent

Malaria 143 40.5

Cholera 62 17.6

Diarrhea 65 18.4

Typhoid fever 72 20.4

Table 6.5 shows that 143 (40.5%) of the respondents reported that after the flood they

suffered malaria, while 62 (17.6%), 65 (18.4%) and 72 (20.4%) respectively said that

they suffered cholera and typhoid fever after the flood.

Table 6.6: Causes of flood in the community

Factors Frequency Percent

Lack of drainage system 192 54.4

Topography 27 7.6

Not building houses according to plan 11 3.1

High rainfall 49 13.9

Indiscriminate dumping of refuse 21 5.9

Bad road 26 7.4

Development 25 7.1

Soil type 2 0.6

Total 353 100.0

Table 6.6 shows that 192 (54.4%) of the respondents attributed the flooding in their

community to lack of drainage system. The table also reveals that topography,

buildings not according to plan, high rainfall and indiscriminate dumping of refuse

88

were also identified as causes of flood by (7.6%), (3.1%), (13.9%) and (5.9%) of the

respondents respectively. Other factors referred to as causes of flood by 26 (7.4%), 25

(7.1%) and 2 (0.6%) of the respondents respectively were bad roads, development and

soil type.

yes96%

no4%

Figure 6.15: Does flood affect business activities in Ngwo communities?

Figure 6.15 shows that 338 (95.8%) of the respondents agree that flood affect business

activities in Ngwo communities, while 15 (4.2%) disagree.

89

Large Low High0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

30.90%

12.20%

56.90%

Figure 6.16: Extent water covers the areas during flood

Figure 6.16 shows that 109 (30.9%) of the respondents reported that water cover the

areas to a minimum extent during flood, 43 (12.2%) said to a low extent while 201

(56.9%) said to a high extent.

Table 6.7: Source of water supply

occupation Frequency Percent

Streams 82 23.2

Bore hole 269 76.2

Others 2 0.6

Table 6.7 shows that sources of water supply in Ngwo communities include streams,

bore hole water and others as reported by 82 (23.2%), 269 (76.2%) and 2 (0.6%) of

the respondents respectively.

90

Medium

yes63%

no37%

Figure 6.17: Does flood affect your sources of water supply?

Figure 6.16 shows that 223 (63.2%) of the respondents are of the opinion that flood

affect sources of water supply in Ngwo communities while 130 (36.8%) of them

disagree. These are mainly households that depend on streams which are polluted

during flooding.

Table 6.8: Measures to check floodingMeasures Frequency PercentConstruction of drainage system 168 54.4Pit construction 45 14.6Adequate sensitization program 25 8.1Removal of waste 30 9.7Tree planting 14 4.5sand bags 17 5.5Use of palm fronds 3 1.0Building houses according to plan 5 1.6communal monthly clean up 2 0.6Total 309 100.0

91

Table 6.8 shows that measures adopted to check flood in the communities include

Construction of drainage system, Pit construction, Adequate sensitization program and

Removal of waste as indicated by (54.4%), (14.6%), (8.1%) and (9.7%) respondents

respectively. Other measures referred to by (4.5%),(5.5%),(1.0%), (1.6%) and (0.6%)

respondents respectively include Tree planting, Sand bags, Use of palm fronds,

Building houses according to plan and Communal monthly clean up.

Table 6.9: Measures adopted to cope after the flood

Occupation Frequency Percent

Evacuation and sensitization

to prevent future occurrence

62 62.0

Proper waste disposal 4 4.0

Evaluation of victims 3 3.0

Individual assistance 20 20.0

Community assisted projects 11 11.0

Total 100 100.0

Table 6.9 shows that measures adopted to cope after the flood. The measures include

evacuation and sensitization to prevent future occurrence (62.0%), proper waste

disposal (4.0%), and evacuation of victims (3.0%), individual assistance (20.0%) and

community assisted projects (11.0%).

92

Table 6.10: Impacts of flooding in Ngwo communitiesVariables None

n (%)

Very low

n (%)

Low

n (%)

Moderate

n (%)

High

n (%)

Very high

n (%)

Mean ± SD

Damage to markets 4 (1.2) 18 (5.3) 25 (7.4) 96 (28.3) 160 (47.2) 36 (10.6) 3.4 ± 1.1

Damage to sources of water supply 26 (7.7) 30 (8.8) 56 (16.5) 89 (26.3) 106 (31.3) 32 (9.4) 2.9 ± 1.4

Damage to buildings/household items 5 (1.5) 9 (2.7) 14 (4.1) 58 (17.1) 122 (36.0) 131 (38.6) 3.9 ± 1.2

Damage to roads 4 (1.2) 1 (0.3) 20 (5.9) 50 (14.7) 121 (35.7) 143 (42.2) 4.1 ± 1.1

Damage to recreational facilities 12 (3.5) 17 (5.0) 60 (17.7) 120 (35.4) 91 (26.8) 39 (11.5) 3.1 ± 1.2

Damage to farm crops 6 (1.8) 8 (2.4) 31 (9.1) 39 (11.5) 70 (20.6) 185 (54.6) 4.1 ± 1.3

Damage to soil/farm lands 5 (1.5) 11 (3.2) 16 (4.7) 41 (12.1) 79 (23.3) 187 (55.2) 4.1 ± 1.2

Damage to electrical installations 8 (2.4) 25 (7.4) 64 (18.9) 123 (36.3) 87 (25.7) 32 (9.4) 2.9 ± 1.2

Damage to health facilities 27 (8.0) 24 (7.1) 71 (20.9) 122 (36.0) 69 (20.4) 26 (7.7) 2.8 ± 1.3

Damage to school buildings 13 (3.8) 19 (5.6) 51 (15.0) 117 (34.5) 107 (31.6) 32 (9.4) 3.1 ± 1.2

Damage to economic trees 21 (6.2) 17 (5.0) 30 (8.8) 47 (13.9) 102 (30.1) 122 (36.0) 3.6 ± 1.5

Severe health hazards 14 (4.1) 33 (9.7) 75 (22.1) 100 (29.5) 75 (22.1) 42 (12.4) 2.9 ± 1.3

Loss of lives 199 (58.7) 78 (23.0) 33 (9.7) 21 (6.2) 5 (1.5) 3 (0.9) 0.7 ± 1.1

*Means greater than cutoff of 3 = high extent and vice-versa

Table 6.10 shows 10.6% of the respondents are of the opinion that flood cause a very

high damage to markets, 47.2% said high, 28.3%, 7.4%, 5.3% and 1.2% respondents

respectively, reported moderate, low, very low and no damage to markets. A high

mean value of 3.4 confirms that damage to markets were high while a standard

deviation of 1.1 very close to the mean indicates low variability of responses. As

regards damage to sources of water supply, 9.4%, 31.3% and 26.3% respondents

respectively believe it’s very high, high and moderate while 16.5% and 8.8%

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respondents respectively believe it’s low and very low. A low mean value of 2.9

confirms that damage to sources of water supply were low while a standard deviation

of 1.4 very close to the mean indicates low variability of responses. Whereas 38.6%,

36.0, and 17.1% respondents agree that flooding cause very high, high and moderate

damage respectively to buildings/household items, 4.1%, 2.7% and 1.5% respondents

believe that it causes low, very low and no damage respectively to buildings/household

items. A high mean value of 3.9 confirms that damage to buildings/household items

were high while a standard deviation of 1.2 very close to the mean indicates that their

responses do not vary much.

The table reveals that 42.2% of the respondents observed that flood cause a very high

damage to roads, 35.7% said high, while 14.7%, 5.9%, 0.3% and 1.2% respondents

respectively, reported moderate, low, very low and no damage to roads. A very high

mean value of 4.1 confirms that damage to roads were very high while a standard

deviation of 1.1 very close to the mean indicates low variability in their responses. As

regards damage to recreational facilities, 39 11.5% believe it’s very high, 26.8% said

high, 35.4% said moderate, 17.7% said low, 5.0% said very low while 3.5% said no

damage. A high mean value of 3.1 means the damage is high and a standard deviation

of 1.2 shows similar response from most respondents. Again as regards damage to

farm crops, 54.6% of the respondents believe it’s very high, 20.6% said high, 11.5%

said moderate, 9.1% said low, 2.4% said very low while 1.8% said no damage.

A high mean value of 4.1 means the damage is very high and a standard deviation of

1.3 shows similar response from most respondents. Similarly, 55.2% of respondents

feel flooding has a very high damage to soil/farm lands, 23.3% said high, 12.1% said

moderate, 4.7% said low, 3.2% said very low while 1.5% said no damage at all. A

very high mean value of 4.1 indicates a very high damage and a standard deviation of

1.2shows low variability of responses. Very high, high and moderate damage to

electrical installations was seen by 9.4%, 25.7% and 36.3% respondents respectively

as an effect of flooding while 18.9%, 7.4% and 2.4% respondents respectively

94

reported low, very low and no damage to electrical installations. A low mean value of

2.9 indicates a low damage and a standard deviation of 1.2 shows low variability of

responses. Similarly, very high, high and moderate damage to health facilities was

seen by 7.7%, 20.4% and 36.0% of respondents respectively as an effect of flooding

while 20.9%, 7.1% and 8.0% of respondents respectively reported low, very low and

no damage to health facilities in the area. A low mean value of 2.8 indicates a low

damage and a standard deviation of 1.3 shows low variability of responses. Results in

the table show that 39.4% of the respondents were of the opinion that flooding causes

very high damage to school buildings in the study area, 31.6% said high, 34.5% said

moderate, 15.0% said low, 5.6% said very low while 3.8% said no damage. A high

mean value of 3.1 confirms high damage to school buildings and a low standard

deviation of 1.2 indicates low variability of responses. Similarly, 36.0% of the

respondents were of the opinion that flooding causes very high damage to economic

trees in the study area, 30.1% said high, 13.9% said moderate, 8.8% said low, 5.0%

said very low while 6.2% said no damage. A high mean value of 3.6 confirms high

damage to economic trees and a low standard deviation of 1.2 indicates low variability

of responses.

Also in the table, 12.4% respondents reported that flooding causes to a very high

extent severe health hazards in the area, 22.1% said high, 29.5% said moderate, 22.1%

said low, 9.7% said very low while 4.1% said no damage. A low mean value of 2.9

confirms that the damage as regards severe health hazards is low and a low standard

deviation of 1.3 indicates that their responses did not vary much. Similarly, 0.9%

respondents reported that flooding causes to a very high extent loss of lives in the

study area, 5 1.5% said high, 6.2% said moderate, 9.7% said low, 23.0% said very low

while 58.7% said no damage. A very low mean value of 0.7 confirms that the damage

as regards loss of lives is very low and a low standard deviation of 1.1 indicates that

most of them agree.

95

HYPOTHESIS TESTING

Ho1: There is no significant relationship between flood occurrence and environmental

problems.

Flood disaster impacts

Flood occurrence

Spearman’s rho 0.861

Sig. (2-tailed) 0.002

N 353

(See tables 2 and 10 for data used in the analysis above)

Decision rule:

Since the significant value (0.002) of the r - statistic is less than 0.05 level of

significance, the null hypothesis is hereby rejected and the alternative accepted.

Therefore, there is a significant relationship between flood occurrence and

environmental problems. The correlation coefficient of 0.861 indicates that the

relationship that exists is very strong and positive. In other words, an increase in flood

occurrence would increase the impact in the area.

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Ho2: The impacts of flood disaster do not vary significantly among communities in

Ngwo

N Mean Std. Deviation F P value

Ukaka 21 3.2527 1.11662

Ameke 40 3.3269 1.13626

Amankwo 50 3.1046 0.50015

Uboji 27 3.3561 0.47856 4.075 < 0.001

Okwojo 20 3.2846 0.82059

Amachalla 17 3.4072 0.34590

Amaebo 23 3.5652 0.40678

Umuasse 18 3.5171 0.36920

Etiti 25 3.2308 0.73749

Okwe 112 2.8565 0.75387

Total 353 3.1639 0.77359

Decision rule:

Since the significant value (P < 0.001) of the F-statistic is less than 0.05 level of

significance, the null hypothesis is hereby rejected and the alternative accepted.

Therefore, the impacts of flood disaster vary significantly among communities in

Ngwo.

97

Duncan Multiple posthoc comparison

Effects

Duncan

Community N Subset for alpha = 0.05

1 2

Okwe 112 2.8565

Amankwo 50 3.1046

Etiti 25 3.2308

Ukaka 21 3.2527

Okwojo 20 3.2846

Ameke 40 3.3269

Uboji 27 3.3561

Amachalla 17 3.4072

Umuasse 18 3.5171

Amaebo 23 3.5652

Sig. .065 .060

Means for groups in homogeneous subsets are displayed.

a) Uses Harmonic Mean Sample Size = 25.877.

b) The group sizes are unequal. The harmonic mean of the group sizes is

used. Type I error levels are not guaranteed.

The multiple comparison result reveals that communities such as Okwe, Amankwo,

Etiti, Ukaka and Okwojo have the same flood impact but different from the rest which

includes Ameke, Uboji, Amachalla, Umuasse and Amaebo. The latter group suffers

more impact than the former group of communities as indicated by higher mean

impacts.

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Ho3: There is no identifiable significant pattern of flood impacts in Ngwo

communities.

Factor Analysis

Descriptive Statistics

Mean Std. Deviation Analysis N

Damage to markets 3.6100 .75069 100

Damage to sources of water supply 3.2200 1.08786 100

Damage to buildings/household items 4.1000 .88192 100

Damage to roads 4.4400 .70094 100

Damage to recreational facilities 3.1500 .84537 100

Damage to farm crops 4.6100 .86334 100

Damage to soil/farm lands 4.7200 .72586 100

Damage to electrical installations 2.9600 .82780 100

Damage to health facilities 3.1000 .93744 100

Damage to school buildings 3.3400 .87870 100

Damage to economic trees 4.3400 1.15662 100

Severe health hazards 2.6200 1.17877 100

Loss of lives .3900 .83961 100

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KMO and Bartlett's Test

Kaiser-Meyer-Olkin Measure of Sampling Adequacy. .755

Bartlett's Test of SphericityApprox. Chi-Square 522.463

Df 78Sig. .000

The Kaiser-Meyer-Olkin Measure of Sampling Adequacy is a statistic that indicates

the proportion of variance in the variables that might be caused by underlying factors.

A value of 0.755 generally indicates that a factor analysis is appropriate for the data.

Bartlett's test of sphericity indicates that the correlation matrix is not an identity

matrix (P < 0.001), which means that the variables are related and therefore suitable

for structure detection.

Communalities

Initial Extraction

Damage to markets 1.000 .555 Damage to sources of water supply 1.000 .588

Damage to buildings/household items 1.000 .558

Damage to roads 1.000 .550 Damage to recreational facilities 1.000 .502 Damage to farm crops 1.000 .827 Damage to soil/farm lands 1.000 .628

Damage to electrical installations 1.000 .562

Damage to health facilities 1.000 .597

Damage to school buildings 1.000 .703

Damage to economic trees 1.000 .638 Severe health hazards 1.000 .695 Loss of lives 1.000 .673

Extraction Method: Principal Component Analysis.

100

Communalities indicate the amount of variance in each variable that is accounted for.

Initial communalities are estimates of the variance in each variable accounted for by

all components or factors. For principal components extraction, this is always equal to

1.0 for correlation analyses. Extraction communalities are estimates of the variance in

each variable accounted for by the components. The communalities in this table are all

high (greater than 0.5), which indicates that the extracted components represent the

variables well.

101

Total Variance Explained

Component Initial Eigenvalues Extraction Sums of Squared Loadings Rotation Sums of Squared Loadings

Total % of VarianceCumulative % Total % of Variance Cumulative

%

Total % of

Variance

Cumulative

%

1 4.411 33.934 33.934 14.744 44.267 44.267 14.218 40.215 40.215

2 1.975 15.191 49.125 12.308 25.524 69.791 12.691 28.472 68.687

3 1.491 11.470 60.594 11.824 21.803 91.594 11.968 22.907 91.594

4 .997 7.673 68.267

5 .763 5.872 74.139

6 .677 5.210 79.349

7 .608 4.676 84.024

8 .551 4.242 88.267

9 .469 3.604 91.871

10 .372 2.860 94.731

11 .338 2.602 97.334

12 .208 1.599 98.932

13 .139 1.068 100.000

Extraction Method: Principal Component Analysis.

The Total column gives the eigenvalue, or amount of variance in the original

variables accounted for by each component. The % of Variance column gives

the ratio, expressed as a percentage, of the variance accounted for by each

component to the total variance in all of the variables. So, factor 1explains

44.267% of total variance, factor 2 explains 25.524% while factor 3 explains

102

21.803%. The first factor explain larger amount of variance whereas the second

and third factors explain smaller amounts of variance. According to Kaiser’s

criterion, retain all factors with eigenvalues above 1 and 0.6 average communality.

Therefore all factors with eigenvalues greater than 1, were extracted which leaves

only 3 factors. The eigenvalues associated with these factors are again displayed and

the percentage of variance explained in the columns labelled Extraction Sums of

Squared Loadings. The cumulative percentage for the 3 components is 92%. They

explain 92% of the variability in the original 5 variables, so we can considerably

reduce the complexity of the data set by using these components, with only a 8%

loss of information. In the final part of the table (labeled Rotation Sums of Squared

Loadings), the eigenvalues of the factors after rotation are displayed. Rotation has

the effect of optimizing the factor structure, however some changes occurred after

the rotation. The rotation maintains the cumulative percentage of variation explained

by the extracted components, but that variation is now spread more evenly over the

components. The changes in the individual totals suggest that the rotated component

matrix will be easier to interpret than the unrotated matrix.

103

The screen plot helps to determine the optimal number of components. The

eigenvalue of each component in the initial solution is plotted. Generally, the first

three components on the steep slope were extracted. The components on the shallow

slope contribute little to the solution.

104

Rotated Component Matrix

Component

1 2 3

Damage to farm crops .903

Damage to economic trees .796

Damage to soil/farm lands .779

Damage to markets .658

Damage to buildings/household items .566

Damage to roads .553

Damage to health facilities .727

Damage to electrical installations .696

Damage to recreational facilities .683

Damage to school buildings .562

Damage to sources of water supply .566

Loss of lives .797

Severe health hazards .652

Extraction Method: Principal Component Analysis.

105

Rotation Method: Varimax with Kaiser Normalization.

a. Rotation converged in 4 iterations.

Finally the rotated component matrix (also called the rotated factor matrix in factor

analysis) which is a matrix of the factor loadings for each variable onto each factor

shows factor loadings greater than 0.5 and sorted by order of size. The result reveals

three factors (components) and variables load very highly onto only one factor. The

variables that load highly on factor 1 are economic factors; the variables that load

highly on factor 2 are infrastructural factors while variables that load highly on

factor 3 health factors. Hence the hypothesis is rejected. Therefore, there is an

identifiable significant pattern of flood impacts in Ngwo communities

106

CHAPTER SEVEN

RECOMMENDATIONS AND CONCLUSION

This chapter presents summary, recommendations and conclusions.

7.1 SUMMARY OF FINDINGS

The main purpose of the study was to examine the flood disaster and its

environmental impacts in Ngwo Enugu State.

The findings of the study have shown that flood often occur in Ngwo communities

and that water covers Ngwo area to a large extent thereby causing damage to lives

and properties. The major cause of flood in the area is lack of adequate drainage

system after a heavy down pour. Blocked channels as a result of waste dumps and

development has contributed significantly to flooding in the area.

The people of Ngwo are predominantly farmers and traders thus the flood submerge

the area and damage farm lands, crops and markets affecting their major means of

livelihood. The sources of water supply were easily contaminated thereby causing

possible outbreaks of epidemic in the communities. The people experienced diseases

such as malaria, cholera, diarrhea and typhoid fever. Properties worth over N2

Million was lost to flood annually.

The study recorded to a high extent damages to markets, buildings/household items,

roads, recreational facilities, farm crops, soil/farm lands, school buildings and

economic trees as a result of flood. However, the impacts of flood on sources of

water supply, electrical installations, severe health hazards and loss of lives were

low.

Construction of drainage system was found to be the remedy to flooding in the area

as well as Construction of flood diversion channels which involves the construction

of artificial channels along main river channels to divert part of the discharge during

flood flows. Measures adopted in the area to cope after the flood were evacuation

107

and sensitization of the victims to prevent future occurrence, proper waste disposal,

evaluation of victims, individual assistance and community assisted projects.

An increase in the frequency of occurrence of flood increases the impacts. The

impacts of flood disaster varied across communities in Ngwo. The pattern of

environmental impact of flood in the area was classified into 3 main components

which include economic, infrastructural and health impacts.

7.2 RECOMMENDATIONS

Based on the findings of this study, the researcher recommends possible solutions

that would accommodate immediate remedial and preventive measures to

minimizing flood problems observed in the study area. Therefore, the following

measures are recommended:

There is a need for provision of standard infrastructural facilities by the government.

These facilities include good surface drainage, potable water supply for consumption

and other supporting facilities. Repair and construction of these drainages where

necessary should be embarked on to further ease the flow of storm water. There

should be improvement in technology on how local building materials can be

subsidized so as to make structures flood resistant. Likewise, roofing materials

should be improved upon to avoid building and structural collapse. Environmental

sanitation programme should be made compulsory and appropriate agency should be

vested with the power to punish residents who fail to adhere to the regulations of

sanitation. There should be fines and penalties for people who fail to comply with

the sanitation program.

Public enlightenment programmes should be organized to educate the public on the

dangers of flood disaster and its causes as a result of the habit of throwing and

dumping refuse in gutters, drainage paths and river channels. There is also need for

government to set up various information programmes to educate the masses on how

to respond to flood disaster. In order to reduce the risk of flood, the government

108

should provide adequate funding for to enable them perform and execute their duties

effectively and efficiently. This will go a long way in checking the problem of flood

occurrence in Ngwo. Strict flood control legislation is required to check unplanned

encroachment on urban plains and should be enforced within the study area. The

town planning authorities are required to restrict development in flood-prone areas.

This measure can be used to avoid flood rather than control it.

The road network in the study area lacks drainage system to the extent that water

overflow on the road during heavy rainfall. Thus, the state government along with

the local government should embark on the construction of wide and deep drainage

system that can withstand heavy water flow.

7.3 CONCLUSION

From the foregoing, this study has been able to examine the current picture of flood

disaster and its environmental impacts in Ngwo Enugu State. The study shows that

the area is vulnerable to flood and have suffered flooding in the past. It found out

that until the present, many of the people have not recovered from the flood losses.

The local people seem to be resilient to flood hazard as they have coped with hazards

in the past, but the frequent of flood disaster occurrence increases the poverty level

in the area since their major means of livelihood is greatly affected.

Disease outbreak was discovered as a challenge in these communities as a result of

water logging and contaminated water. The study revealed a significant positive

relationship between frequency of flood disaster and its impacts. Different

communities suffered different high levels of impacts depending on their socio-

economical, physical and environmental characteristics. Though flood disaster has

diverse effects associated with it both in developed and developing world. These

effects such as economic devastation, property loss, environmental disease and

untimely death can be reduced and properly managed by adopting both remedial and

preventive action to combat the problem of flooding as both approaches are needed

to run concurrently to achieve success in dealing with flood. Also, the above stated

109

measures could be adopted so as to have disaster free environment and to achieve a

safe, conducive, pleasant and aesthetic environment for living and working.

This study brings out the important issue of vulnerability, coping and adaptation to

disasters caused by flood among the rural poor. It examined in some detail the

strategies adopted by poor neighbourhoods as disasters impact on their livelihood

systems and the sequence of responses which they employ over time as they struggle

to cope. The study revealed that the indigenous coping mechanisms employed by the

poor may become less effective as increasingly fragile livelihood systems struggle to

withstand disaster shocks. Also, many of these long-term trends are rendering

indigenous coping strategies less and less effective and thus are increasing the

vulnerability of the poor. It seems increasingly accepted (although not consistently

implemented) that disasters shouldn’t be dealt with through humanitarian relief

interventions alone as revealed in this study. There is some evidence to support the

argument that disaster management response in the city, just like in other areas in

Nigeria, should shift away from this traditional response approach to focus

increasingly on addressing the causes of vulnerability in order to mitigate the effects

of disaster. However, the approach tends to address only the visible signs of

vulnerability, such as poor access to services, and generally fails to make a deeper

analysis based on the maintenance of sustainable livelihoods by vulnerable people.

110

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APPENDIX 1

Scale: ALL VARIABLE

Case Processing Summary

N %

CasesValid 20 100.0Excludeda 0 .0Total 20 100.0

Reliability Statistics

Cronbach's Alpha

Part 1Value .782

N of Items 22a

Part 2Value .816N of Items 21b

Total N of Items 43

Correlation Between Forms .751

a. The items are: Q4, Q5, Q5, Q7, Q8i, q8ii, q8iii, Q9, Q10, Q11, Q12, Q13i, q13ii,

q13iii, q13iv, Q14, Q15, q16i, q16ii, q16iii, q16iv, Q17.

b. The items are: Q17, Q18, Q19, Q20, Q21, Q22, Q23, Q24, Q25, Damage to markets,

Damage to sources of water supply, Damage to buildings/household items, Damage to

roads, Damage to recreational facilities, Damage to farm crops, Damage to soil/farm

lands, Damage to electrical installations, Damage to health facilities, Damage to school

buildings, Damage to economic trees, Severe health hazards, Loss of lives.

QUESTIONNAIRE

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CENTER FOR ENVIRONMENTAL MANAGEMENT AND

CONTROL

Dear Respondent,

I am an M. sc candidate in the Center for Environmental Management and

Control of the University of Nigeria. I am carrying out a research entitled

“The flood disaster and its environmental impacts on Ngwo community Udi

Local Government Area of Enugu state, Nigeria. This study is aimed at

determining the extent of environmental hazard flooding has caused on the

physical environment of Ngwo community. The outcome of the research is

capable of contributing to efforts aimed at minimizing the impacts of flood

hazards and vulnerability on physical environment of Ngwo community and

Nigeria, in general.

This exercise is purely for academic purposes; therefore any information

supplied in this questionnaire will be treated with utmost confidentiality.

Kindly respond to questions by ticking or providing the appropriate answers.

Thank you

Mbah Chinasa

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SECTION A

1. Sex A. Male B. Female

2. Your occupation? A. Trading B. Farming C. Civil service D.

Others, specify ……………………………….………………..

3. Name of your community? ---------------------------------------

4. Have your community experienced flooding before?

A. Yes B. No

5. When does this flood occur in your area? A. Several times in a year

B. Few times in a year C. Not often

7. Have you lost any property as a result of flooding? A. Yes B. No

8. What is the type of property lost in floods? A. None B. House C.

Household items D. Farms

E. Others, specify ……………………………………………..

9. What is the expected value of the property that you lost to flooding?

…………………………………………………………………...

10. Has any life been lost as a result of flood in your community?

A. YES B. NO

11. If yes, how many ……………………………………………..

12. Are there experiences of any disease after the flood?

A. YES B. NO

13. What kind of diseases did people encounter?

A. Malaria B. Cholera C. Diarrhea D. Typhoid fever

E. Others, please specify………………………………

14. What in your opinion are the likely causes of flooding in your

community?………………………………………………………….

15. Do you think development contributes to flood in Ngwo?

A. yes B. No.

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16. What do people do mostly in Ngwo to earn living?

A. Farming B. Trading C. Civil service D. Transport

E. Others, please specify others………………….…………………

17. Does flood affect business activities in Ngwo communities?

A. Yes B. No

18. To what extent does water cover the areas during flood?

A. Large B. Low C. High

19. What is your source of water supply?

A. Streams B. Pipe burn water

C. Others, please specify……………………………………..

20 Does flood affect your sources of water supply?

A. Yes B. No

21. What parts of Ngwo do you think are always most affected by the

flood?

…………………………………………………………………..

22. What measures do you adopt in your community to check flooding?

…………………………………………………………………..

23. What measures do you adopt to prevent flooding?

………………………………………………………….……...

24. What measures do you adopt to cope after flood?

………………………………………………………………..…

25. What measures do you think can be taken to reduce the impacts of the

flood in Ngwo? ..………………………………………………

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26. Please rate the extent, these factors are true about flooding in your

community:

Variables Very high

high moderate low Verylow

none

Damage to marketsDamage to sources of water supplyDamage to buildings / household items

Damage to roads

Damage to recreational facilitiesDamage to farm crops

Damage to soil/ farm lands

Damage to electrical installationsDamage to health facilities

Damage to school buildings

Damage to economic trees

Severe health hazards

Loss of lives

Thanks for your cooperation.

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