ABSTRACT
Flooding is persistent in Lagos Metropolis. The objective of this study is to ascertain the causes, magnitude, and effects; and to indicate directions for policy makers and urban dwellers. Topographical maps were used for data collection on the physical environment. Some physical measurements were made of the drainage channels and floods. 200 inhabitants of the metropolis were randomly selected and made to respond to some questions. In addition, authorities in professionally related fields including policy makers were made to make contributions. Intermittent supplies and torrential rainfall in its seasons are usually beyond the capacities of the channels. These are compounded by inadequate planning of the physical environment, wastes dumped in drainage channels and erosion passages, and deliberate or inadvertent physical structures that block free flow of water along the drains.
CHAPTER ONE
INTRODUCTION
1.1 Background to the Study
Poor drainage systems form part of major threats to urban environments in Nigeria. Most of streets within the urban and rural settlement are faced with the challenges such as lack of drainages or properly designed drainages to evacuate storm water from the surface-course of our roads. Cities the world over are the dominating forces in the organization of human population. As the world most crowded places, cities continue to show increase in urban population. This increase leads to a growing urbanization trend. Duru and Nnaji (2008) defined urbanization as the increase in the population of cities in proportion to the region‟s rural population. Urbanization is the outcome of social, economic and political developments that lead to concentration and growth of large cities, changes in land use and transformation from rural to metropolitan pattern of organization and governance. Rapid growth of towns and cities has been common feature of the developing world (Aderamo, 2008). Although urbanization is the driving force for modernization, economic growth and development, there is increasing concern about the effects of expanding cities, principally on human health, livelihoods and the environment.
Drainage systems are constructed to ensure that waste water and sewage is transported neatly to disposal points, thereby keeping the environment well drained and free of waste. Examples of components that make up a good drainagesystem includes; closed ditches having pipe drains, drainage pipes, channels and conduits (Folorunsho, & Awosika, 2001). Sustainable Drainage Systems are approaches put in place to manage the water quantity (flooding), water quality (pollution) and amenity issues in the environment. Sustainable drainage is a concept that includes long term environmental and social factors in decisions about drainage. Sustainable Drainage Systems are intended to regulate surface water runoff close to where it falls and simulate natural drainage as closely as possible. They provide opportunities to reduce the causes and impacts of flooding, remove pollutants from urban runoff at source, and combine water management with recreation and wildlife. They also help to enhance water quality while protecting natural flow regimes in watercourses (Dipanjan & Mukherjee 2014).
In many parts of Nigeria today, there is a great need for properly managed sustainable drainage systems in order to help manage surface water runoff. Neighborhoods keep springing up without proper planning, which also involves planning for drainage and sewage or waste disposal. Residents regularly dump their waste in gutters, and this clogs the gutters and prevents the flow of water, causing the gutters to overflow (Enger & Smith, 2006). It is common to see flooded streets with litter floating everywhere after a short period of rainfall. Such situations create very unsanitary conditions for residents of the neighborhoods and contribute to the degradation of the environment. In the year 2012, 363 people were feared dead while 2.1 million citizens were displaced across Nigeria as a result of floods. According to the National Emergency Management Agency (NEMA), 30 states out of 36 in Nigeria were affected by that flood experience and it was concluded as the worst that has ever happened in the past 40 years, causing damages of an estimated value of N2.6 trillion Naira (Jimoh, 2008). These floods also gave rise to environmental pollution problems which affected the health of Nigerians across the various affected areas. Nigeria is currently experiencing its annual rainy season, and in order to avoid lethal floods it is important to have very effective drainage systems and strive towards ensuring free flow of water during and after heavy downpours. Poorly maintained drainage systems and poor waste management habits can adversely affect our environment (Okupe, 2002).
The implications of rapid urbanization and demographic trends for employment, food security, water supply, shelter and sanitation, especially the disposal of wastes (solid and liquid) that the cities produce are staggering (Oduwaiye, 2009). The process of urbanization is believed to be connected with levels of development and some assert that, for a country to develop there is the need for an increased level of industrialization as it is generally accepted that there cannot be urbanization without rapid economic growth (Tettey, 2005). The pattern of urbanization in developing countries, particularly Africa, however, is creating some concern that it may be generating a lot of development problems in the process of its growth. One of the daunting challenges facing African countries in the wake of unprecedented urbanization during the last few decades is the planning and management of physical infrastructure and the urban environment (Kwasi, 2011).
As urbanization gathered pace in most developing countries, the problem of inadequacy of infrastructure services and deteriorating urban environment became enormous (Sule, 2009). These problems range from poor housing conditions, inadequate infrastructure, to squatter settlements (Arimah, 2002). Spurred by the oil boom prosperity of the 1970s and the massive improvements in roads and the availability of vehicles, Nigeria since independence has become an increasingly urbanized and urban-oriented society. During the 1970s, Nigeria had possibly the fastest urbanization growth rate in the world (Sule, 2009). Because of the great influx of people into urban areas, the growth rate of urban population in Nigeria in 1986 was estimated to be close to 6 percent per year, more than twice that of the rural population. Specifically, while only 7% of Nigerians lived in urban centers in the 1930s, and 10% in 1950, by 1970, 1980 and 1990, 20%, 27% and 35% respectively lived in the cities (Okupe, 2002). Over 40% of Nigerians now live in urban centers of varying sizes. Like other developing countries, the rapid growth in urban areas in Nigeria is a ‘’sword of two edges‟ (Sule, 2009). While increasing human capital increased the economic status of the country, the growths of large centers had outpaced government capacity to meet the increasing demand for the provision of basic infrastructural facilities and services. These are manifested in poor investment in roads, housing, water supply, electricity, waste disposal mechanisms, adequate drainage systems etc. (Sule, 2007; Aderamo, 2008; Jimoh, 2008). These problems have continued to persist and made worst due to non-compliance to planning ordinances (Sule, 2010). Appropriate management of drainage systems requires knowledge relating to the system boundary, system resources, interactions between adjacent systems and allowable limits, or thresholds, for each resource. Each of these elements will be unique to the particular system under consideration, and each system must be assessed on its own merits (Offiong, et’ al, 2008).
Drainage quality is an important parameter which affects the highway pavement performance. The excessive water content in the pavement base, sub-base, and sub-grade soils can cause early distress and lead to a structural or functional failure of pavement. Drainage is the most important aspect of road design. Proper design of drainage is necessary for the satisfactory and prolonged performance of the pavement. In designing drainage, the primary objective is to properly accommodate water flow along and across the road and conveniently transport and deposit the water o the downstream without any obstruction in the flow (Rokade, Agarwal & Shrivastava, 2012). A typical road construction is multi-layered in form, comprising of unbound materials. Essentially, the lower indigenous subgrade layer is covered by a bound or unbound sub base, providing drainage and frost protection for the subgrade, and the road base layer upon which the asphalt layers are laid as a final surface coating. Poor drainage in pavement can lead to early pavement distresses lead to driving problems and structural failures of the road. The primary source of water in pavements is atmospheric precipitation. This water can enter the pavement through several ways (e.g., cracks, infiltration, through shoulders and ditches, high groundwater) and is moved by an energy gradient, such as gravity, capillary forces, osmotic forces, and temperature or pressure differences (Henderson, 2004).
Flooding in urban areas is not just related to heavy rainfall and extreme climatic events; it is also related to changes in the built-up areas themselves. In the case of Maiduguri, the problems of street flooding began when some socio economic and anthropogenic activities gained momentum as a means of face lifting the city as State Capital. The influx of people from both rural and adjoining states led to increased demand for housing. Houses were hurriedly built to meet the burgeoning demand for shelter as a result of insurgency. This alters the aesthetic image of the city as buildings were erected anyhow and anywhere (Sule, 2004).
1.2 Statement of the Problem
Worldwide, there has been a rapid growth in the number of people killed or seriously impacted by storms and floods and also in the amount of economic damage caused; a large and growing proportion of these impacts are in urban areas in low- and middle-income nations. For instance, in Nigeria, flooding affected more than three million people in selected urban areas between 1983 and 2009 (Folorunsho & Awosika, 2001). Poor urban infrastructural development and planning is likely to have been a factor in much of this, but even if it was not, it is proof of the vulnerability of urban populations to floods and storms whose frequency and intensity is likely to increase in most places. Maiduguri is one of the cities that are growing at a high rate in terms of infrastructural development, which involves construction and concretization of the city land surface. This, as a result of poor drainage systems, leads to flooding and other environmental problems such as roadway pavement failure (Giwa, 2007).
Henderson (2004) revealed that the level of risk and vulnerability in urban areas of developing countries is attributable to socio-economic stress, aging and inadequate physical infrastructure. Indeed, according to Satterthwaite, et’ al, (2007), hundreds of millions of urban dwellers have no all-weather roads, no piped water supplies, no drains and no electricity supplies; they live in poor quality homes on illegally occupied or sub-divided land, which inhibits any investment in more resilient buildings and often prevents infrastructure and service provision.
A high proportion of this are tenants, with very limited capacities to pay for quality housing and their landlords have no incentive to invest in better-quality buildings. Most low-income urban dwellers face serious constraints in any possibility of moving to less dangerous sites, because of their need to be close to income-earning opportunities and because of the lack of alternative, well-located, safer sites. Douglas et al (2008) also report that many of the urban poor in Africa face growing problems of severe flooding; they further buttressed the fact that increased storm frequency and intensity related to climate change are exacerbated by such local factors as the growing occupation of flood plains, increased runoff from hard surfaces, inadequate waste management and silted up drainage. Askew (1999) reiterated that floods cause about one third of all deaths, one third of all injuries and one third of all damage from natural disasters globally. Generally, flood events are attributed to global warming, climate change, ocean swell/surge and torrential rains. Although flood hazards are natural phenomena, damage and lose from floods are mostly the consequences of urbanization without corresponding infrastructural restructuring (Brooks, 2003). Flooding is the most common environmental hazard in Nigeria (Etuonovbe, 2011). The intensity of flood problems over time and space in Nigeria urban centers is closely related to the rapid rate of urban expansion especially where the simultaneous provision of adequate run-off disposal systems is lacking as is the case of most Nigerian cities and Maiduguri in particular (Abaje and Giwa, 2008). The implications of recent flooding in Nigerian cities include, among others, loss of life and properties, spread of diseases, deformed livelihoods, assets and infrastructure using both questionnaire and secondary data in the analysis of the history and causes of flood incidence in the city of Maiduguri opined that no year passes without flooding in the city destroying houses and blockage of road; on the average four lives were lost yearly to flooding.
Recently Maiduguri especially Jiddari Polo is facing extensive water logging during the rainy season (July to September) as result of a serious problem of poor drainage. Inadequate drainage problems become one of the most common sources of compliant from the residents in the study area and this problem becoming worse in this year. Poor existing drains and their improper operation and management mainly cause severe flooding which creates damages and problems to the road pavement and road users. In addition, deceases are spread and give problems to the population such as malaria and diarrhea. This critical situation was severely aggravated because the natural drainage system, which conveys storm runoff from the areas to the river were not fully operated and the existing drains blocked with huge amount of garbage, solid waste, silt sand accumulation and vegetation. It is against this background that this research intends to assess the effect of poor drainage system on flash flooding in Lagos State.
1.3 Aim and Objectives of the Study
The main aim of this study is to assess the effect of poor drainage network on flash flooding in Lagos state. The specific objectives of the study are to:
i. examines the intensity and frequency of floods in Lagos state;
ii. assess and evaluate the spatial distribution of drainage networks in the area;
iii. examine the effect of poor drainage system on the residents of the study area and
iv. assess the attitudes of the residents towards drainage system and flooding in the study area.
1.4 Research Questions
The study answered the following research questions toward achieving the research objectives:
i. What is the frequency and intensity of floods in Lagos state?
ii. What is the spatial distribution of drainage networks in the area?
iii. What is the effect of drainage width and depth on flood in the study area?
iv. What is the attitudes of the residents towards drainage system and flooding in the study area?
1.5 Significance of the Study
This study will be of great benefit to various sectors both governmental and Non-governmental organization. The study will be significant to National Emergency Management Agency (NEMA) as it revealed the various areas of poor sanitation in Maiduguri. It will be of benefit to environmentalist and town planners as the study revealed the various areas of poor town planning which resulted to lack of drainage because no good street for drainages to be constructed. The study will also help the health sectors in identifying the various diseases bedeviling the community of the study area due to excessive flooding which breaded some bacterial and diseases. NGOs who are concern with WASH activities will also find this study very useful as it revealed the sanitary conditions of the environment. Finally, the study will be of great benefit to students and researchers who may need information on the subject matter under study.
1.6 Scope of the Study
This study was restricted to selected area of Lagos state that is prone to flood occurrence. It assessed the capability of drainage networks to effectively handle run off volume in the area. The study was conducted in Lagos state. This location was selected because it has a history of frequent floods especially during the rainy seasons. In addition, flood prone areas are largely characterized by poor planning as compared to the control.
1.7 LIMITATION OF THE STUDY
There were some factors which limited the scope of the study:
(a) Availability of research material: The research material available to the researcher is insufficient thereby limiting the study.
(b) Time: The time frame allocated to the study does not enhance wider coverage as the researcher has to combine other academic activities and examinations with the study.
(c) Finance: The finance available for the research work does not allow for wider coverage as resources are very limited as the researcher has other academic bills to cover.
1.8 OPERATIONAL DEFINITION OF TERMS
Drainage: Drainage is the natural or artificial removal of a surface’s water and sub-surface water from an area
Floods: A flood is an overflow of water that submerges land that is usually dry. The European Union Floods Directive defines a flood as a covering by water of land not normally covered by water
Flood control: Flood control methods are used to reduce or prevent the detrimental effects of flood waters. Flood relief methods are used to reduce the effects of floodwaters or high water levels.
1.9 Organization of the study
This research work is organized in five chapters, for easy understanding, as follows Chapter one is concern with the introduction, which consist of the (overview, of the study), statement of problem, objectives of the study, research question, significance or the study, research methodology, definition of terms and historical background of the study. Chapter two highlight the theoretical framework on which the study its based, thus the review of related literature. Chapter three deals on the research design and methodology adopted in the study. Chapter four concentrate on the data collection and analysis and presentation of finding. Chapter five gives summary, conclusion and also recommendations made of the study.
