CHAPTER ONE

INTRODUCTION

 Background To Study

The complexity of anthropogenic activities of man without adequate attention to geological structure of most cities of developed and developing nations has undoubtedly contributed to reoccurrence of disaster and consequently poses threat 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, p. 1) “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…’’. These plethora of problems are bedeviling cities of third world countries and Nigeria in particular.

Consequently, there has been unprecedented occurrence of floods and its associated negativities in most of the urban centers of developing countries (Montoya Morales, 2002). 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, 2002, 2004 and 2006) and the coastal cities of Lagos, Ogun, Port Harcourt, Calabar, Uyo, Warri among others (Olaniran, 1983). This claimed many lives and properties worth millions of Naira. 

Several anthropogenic factors have contributed to the incidence of flood. Among these factors is the encroachment of development to flood prone areas. The incursion into such areas have being progressive until now because of unprecedented urbanization and industrialization which has undoubtedly resulted into large scale massive deforestation, loss of surface vegetation and farmlands. According to Okechuckwu (2008 p. 272); “the incursion of unplanned and uncontrolled development into urban infrastructure facilities, violate the major objectives of physical planning and consequently result into misuse of land thereby creating disorderly arrangement of urban landscape and the occurrence flood that is mostly evident in cities of third world countries”. Arising from these incongruous and haphazard developments in cities of third world cities, the occurrence of flood, particularly in Lagos, has been known to be paramount to some areas or local government in the state where Agege local government is not an exemption. 

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. Thus if adequate attention in terms of preventive measures are not put in place towards controlling its sporadic occurrence and its associated impacts particularly during rainy season, its incidence can turn a developed nation back into a developing nation. 

In the past decade in Nigeria, thousands of lives and properties worth millions on Naira have been lost directly or indirectly from flooding every year. In most urban centers of the country most especially in fast growing towns like Gwagwalada town of the Federal Capital Territory (FCT), human population increase, landscaping in paved areas, streams and channel obstruction due to bad waste disposal habit and other human activities at flood plains were considered to be the major causes of floods Olusegun, 2004a; Olusegun 2004b). Barroca (2006) and Blong (2003) felt that flood vulnerability mapping can offer a hundred percent security against floods. 

Flood disaster management just as other disasters management can be grouped into (i) the preparedness phase where activities such as prediction and risk zone identification or vulnerable mapping are taken up long before the event occurs; (ii) the prevention phase where activities such as forecasting, early warning, monitoring and preparation of contingency plans are taken up just before or during the event and (iii) the response and mitigation phase where activities are undertaken just after the disaster and its includes damage assessment and relief management (Van Western et al., 1993).

Mitigation of flood disaster can be successful only when detailed knowledge is obtained about the expected frequency, character, and magnitude of hazardous events in an area as well as the vulnerability of the people, buildings, infrastructures and economic activities in a potential dangerous area (Van Western and Hosfstee, 2000). Unfortunately, Ifatimehin et al (2009), Ishaya et al(2008a), Ishaya et al (2008b) and Ifatimehin and Ufuah (2006) reported that this detailed knowledge is always lacking in most urban centres of the developing world especially Nigeria. One way to mitigate the effects of flooding is to ensure that all areas that are vulnerable are identified and adequate precautionary measures taken to ensure either or all of adequate preparedness, effective response, quick recovery and effective prevention. Before these could be done, information is required on important indices of flood risk identification which are elevation, slope orientation, proximity of built-up areas to drainages, network of drains, presence of buffers, extent of inundation, cultural practices as well as  attitudes and perceptions.

Statement of problem

Many factors contribute to flood risk in urban catchment areas. Hydrological factors cause rapid flood runoff and flood discharge grows with an increase in impervious areas. Concentration of population and assets is also important as a social aspect of flood risk. Climate change is now considered an important factor increasing flood risk, with its increasingly frequent torrential storms (IPCC, 2007; Patrik Willems et al., 2012). To reduce flood risk, national and local governments have been implementing structural measures, constructing flood control reservoirs and infiltration and storage facilities with their budgets available for flood prevention. Significant non-structural measures must also be employed for flood risk reduction, using such tools as hazard maps and effective forecasting systems. Flood insurance mitigates flood inundation damage and contributes to relieving flood risk. For urban flood risk management, these factors that increase or decrease risk should be compared and evaluated in the decision-making process of urban flood control planning.

There are many different definitions of flood risk. Crichton (1999) gives the simplest, a comprehensive definition using the “Crichton Risk Triangle” that consists of hazard, vulnerability, and exposure. Some researchers adopt the narrow definition of flood risk as the probability of failure during a flood event (e.g., National Research Council, 2000). Some other researchers strongly emphasize the mental aspect of flood risk (Baan, 2005). Samuels (2013) broadly discusses flood risk management and gives the definition of flood risk as an evaluation of the combination of the probability of flooding and the adverse consequences that ensures. Klijn et al. (2008) shows the standard definition of flood risk as the ‘product’ of the probability of floods and their consequences. This definition enables us to evaluate flood risk on a the basis of structures generating flood in urban areas

Objective of the study

The objective of the study are:

1.                  To map out areas that are vulnerable to flooding within Kubwa Urban area

2.                  To determine if urban structures causes flood vulnerability

Significance of the study

The importance of this research cannot be overemphasized because of its immense significance to different groups of people who are in need of information that it will provide. Its significance includes the following:

The study will enable the management of flooding and provide an in-depth understanding and knowledge of the flood prevention strategies available so that they can adopt them adequately.

The study will also serve as a source of secondary data for students and scholars who intend to carry out similar studies in the future.

Scope of the Study

The scope of this study in terms of its content is restricted to the flood generating structures in kubwa urban landscape.

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