CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
Flood is the overflow of water into an environment that is normally dry thereby causing inundation and harm to plants and animals, including man. Its harm can be extended to man’s buildings and infrastructures (Udosen, 2011). Most flood definitions include damage they cause and depend on their sources or types and magnitude. In the case of flood resulting from rivers, Ating (2003) defines it as a relatively high flow which overtakes the natural channels provided for run–off as well as a high stream which overtops its natural or artificial banks. Wolf (1965) also describes flood as high rate of discharge in water sources and the inundation of normally dry lands. West (1991) further states that flood is a body of water which rises to overflow its banks or low- lying areas. All over the world, flood is known to cause great damage to people’s lives, belongings and properties. Flood causes one third of deaths, one third of all injuries and one third of all damage from natural disasters (Askew, 1999 and Etuonovbe, 2011). This damage is normally felt by various “receptors” being people, buildings, infrastructure, agriculture, and open recreational spaces. Even social and emotional costs from flooding are significant and are often widespread and indiscriminate in flooded areas. They include displacement from homes, loss of personal valuables, fear and insecurity caused by such experience. The economy can be serially affected by flooding as businesses may lose patronage, stock, data and productivity. Tourism, farming and livestock can equally be affected. Utilities and transport infrastructure can be rendered inefficient by flood. Portable water supplies may be contaminated in a flood which has immediate health effects upon human beings and animals. Other vital infrastructures may also be damaged just like the loss of electricity experienced in Britain in 2007 summer floods (RIBA, 2009). Even in a developed country such as the United Kingdom, the Association of British Insurers has estimated the cost of the July, 2007 flooding, in insurance claims alone at over 3 billion pounds (RIBA, 2011). The pattern of flooding is similar in all parts of the world. In Nigeria for instance, flooding has forced millions of people out from their homes, destroyed businesses, polluted water sources, and increased the risk of diseases (Baiye, 1988, Akinyemi, 1990, Nwaubani, 1991 and Edward- Adebiyi, 1997). a) Sources of flooding Generally, there are six recognized sources of flooding namely: tidal flooding, fluvial flooding, ground water, pluvial flooding, flooding from sewers and flooding from man – made infrastructure. Ø Tidal Flooding Sea and river defenses may be overtopped by a combination of low pressure weather systems and high tides. Its duration is limited by the cycle of the tides where drainage is available. Fluvial Flooding – When rainfall or snow occurs in rivers, the capacity is exceeded and as a result, there is a rising water level which can in turn overflow into the floodplains close to the river. Ground Water – As ground water levels rise, low lying area sitting over aquifers may flood. This type of flood is mainly seasonal and slow. Pluvial Flood -Refers to surface water from rainwater – run-off mainly from urban or rural land that has low absorbency. As developments increase in urban areas, land surfaces increase in their areas of non-permeable surfaces and combines into intense rainfall which gives rise to localized flooding. Flooding from Sewers occurs where there are faulty sewers or where sewage capacity is exceeded normally due to large surface water runoff over a short time. Flooding from Man – made Infrastructure occurs when man-made structures like canals and reservoirs fail resulting in flooding areas downstream (RIBA 1999).
1.2 Statement of the Problem
Although floods can happen at any time during the year, there are some typical seasonal patterns for flooding in Uyo Local Government Area, based on the variety of natural processes that cause floods. Rainy Season floods are produced by heavy rainfall on wet ground which penetrates into lands which were previously dry and causes a lot of damages to people and properties.
1.3 Objectives of the Study
The main thrust of this study has been to assess the immediate and remote causes of frequent flooding in Uyo metropolis. Specifically, it aims to;
1. Determine the major causes which may be more responsible for the recent incidences of flooding in Uyo city.
1.4 Research Questions
1. What are the causes of frequent flooding in Uyo metropolis?
1.5 Research Hypothesis
Ho: There is no frequent flooding in Uyo metropolis.
Hi: There is frequent flooding in Uyo metropolis.
1.6 Significance of the Study
This study will help to determine the causes which may be responsible for the recent incidences of flooding in Uyo city. To be able to do this successfully, a number of physical flood characteristics were evaluated. These critical physical characteristics include:
a) Depth of water
b) Duration of inundation
c) Area of inundation
d) Velocity of flow
e) Frequency – recurrence relations
f) Floodtime (Flood time lapse or flood-to-peak interval)
g) Seasonality
h) Peak flood
i) Rate of discharge increase and decline.
j) Sediment load and
k) Total flood run-off volume.
1.7 Scope of the Study
The study focuses on the causes of excess flood in Uyo Local Government Area, AkwaIbom state, Nigeria. UyoLocal Government Area is used as the case study for this research due to the incessant flood occurrence in Uyo during raining seasons and her representative nature to other flood prone areas.
1.8 Limitations of the Study
The area of study is Uyo metropolis. This metropolis is situated in Uyo Local Government Area. It is highly urbanized, virtually all parts of Uyo lie within the Capital City Development Area (UCCDA). The study however has some limitations most especially in the area of data collection. Financial constraints as well as time available for the completion of the study are among other factors that would limit the scope of the study.
1.9 Definition of Terms
Flood:An overflow of a large amount of water beyond its normal limits, especially over what is normally dry land.
Uyo LGA:Is the capital of Akwa Ibom State in Nigeria.
CAUSES OF EXCESS FLOOD IN UYO LOCAL GOVERNMENT AREA
