Effectiveness Of Drainage Networks On Floods In Calabar Metropolis, Nigeria
The study examined the effects of drainage networks on floods in Calabar metropolis, Nigeria. The rapid increase in urbanization without corresponding infrastructures in the city of Calabar has led to increased incidences of flood as the available drainage channels cannot contend with the volume of storm water. In view of this, the study established gauging stations for the measurement of drainage run off using measuring steel tape. And the volume of flood water was measured using stop watch method (Velocity of flow) and copies of questionnaire were administered to 400 households proportionally to the seven sample units.
In view of the study objectives, it determine the relationship between drainage width and depth and floods. In addition, varied descriptive statistics tools were used to give a spot on assessment and understanding of the variables of interest. In view of the response of the gauging and physical measurement, it was established that Calabar experience heavy rainfall due to poor drainage facilities The result revealed that about 47% of the respondents said flood occur every year in their zone and 41.75% said it occurred most parts of the year. The frequency of flood is compounded with it’s intensity as over 59% of the sampled population agreed that flood of the sampled population agreed that flood intensity is very high in Calabar.
The result further showed that the factors of flood occurrence in the study area is linked to heavy rainfall (26.3%), inadequate drainage channel (22%) poor physical planning (15.5%) among others. On the perceived causes of inadequate drainage channel, the result indicated that abuse of land use plans (28.7%) was a major factor followed by poor monitoring and evaluation of project (21.5%). the study also revealed that the drainage were very narrow and shallows as shown in frequent floods in the city.
The incessant flood often leads to water inundating compounds (64.5%), preventing people from going out (11.25%), distortion of the scenic beauty of the environment (6.25%), landslide (4.75%). Based on these findings, the study recommended that since Calabar is located in a tropical zone characterized by heavy rainfall the government should take proactive measure to mitigate storm water. The present drainage systems should be cleared with shovel by the people on a regular basis to allow for a free flow of storm water. State department of town planning should live up to their bidding by ensuring total compliance to urban ordinance to forestall incessant floods and destruction of properties in the city of Calabar.
1.1 Background to the Study
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. 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 (United Nations Conference on Environment and Development, 1992).
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. 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.
Flooding has been identified as one of the major factors that prevent Nigeria growing population of city dwellers from escaping poverty and stands in the way of United Nations goal of achieving significant improvement in the lives of urban slum dwellers by 2020 (Action Aid, 2006)
Nigerian coastal cities are daily inundated with flood waters, and millions of properties have been destroyed and lives lost (Eze, 2008). Poor drainage systems are often associated with street flooding, and this has become critical environmental problems in coastal cities of Nigeria such as Lagos, Port Harcourt, Ondo, Warri, Uyo, and Calabar (Eze, 2008). These towns which are quite close to the Atlantic Ocean experience heavy flooding especially during the rainy season. However, it is not waters from the Ocean that usually floods these cities but the heavy rains, and the low nature of the topography and the poor drainage networks. Aderamo (2008) listed land use problems, increased paved surfaces, river channel encroachments, poor waste disposal techniques, physical development control problems, gaps in basic hydrological data and cultural problems as major causes of street flooding in Nigerian cities.
1.2 Statement of the Research 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 (Environmental Management Disaster Database). 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.
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, Mark, Saleemul, Reid and Romero (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). Flood disaster is not an ancient phenomenon in the country, and its destructive tendencies are sometimes enormous. Reports have it that serious flood disasters have occurred in Ibadan (1985, 1987 and 1990), Osogbo (1992, 1996, 2002), Yobe (2000) and Akure (1996, 2000, 2002, 2004 and 2006); the coastal cities of Lagos, Port Harcourt, Calabar, Uyo, Warri among others have severally experienced incidences that have claimed many lives and properties worth millions of dollars (Olajuyigbe, Rotowa and Durojaye, 2012).
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 are lacking as is the case of most Nigerian cities (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 (Adedeji, Bashir, Bongwa and Oladesu, 2012).
Eze (2008) using both questionnaire and secondary data in the analysis of the history and causes of flood incidence in the city of Calabar opined that no year passes without flooding in the city claiming lives and properties; on the average four lives were lost yearly to flooding. Eze attributed flood occurrence to expansion of residential areas and the multiplications of paved surfaces including roads and sidewalks. Offiong and Eni (2007) using both conventional questionnaire and secondary data corroborated these claim by observing that the damage to materials is quantified to be well over 115.76 million naira per year. The main factors of flooding in the city of Calabar in the view of Ofiong and Eni, are increasing demand for concrete surfaces for buildings which has increased surface runoff, and waste waters that have increased the volume of water in rivers, streams and drainage channels.
Afangideh, Ekpe and Offiong (2012) examined the implication of changing rainfall pattern on building loss in Calabar. Rainfall data for the study were collected from the Nigerian Meteorological Agency (NIMET) and Margaret Ekpo International Airport, Calabar. While data on cost of building loss to flood for the previous 20 years were gotten from the inhabitants of the flood prone areas in Calabar. The result from their study revealed that annual rainfall intensity with beta coefficient of 0.437 has more implication on cost of building loss to rainfall in Calabar than annual rainfall duration, with beta coefficient of -0.063.
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 Calabar, 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. This alters the aesthetic image of the city as buildings were erected anyhow and anywhere (Sule, 2004), which degenerated into the „ugly face of Canaan city‟ (Iquot, 1982). Today in spite of the fact that Calabar is acclaimed to be one of the cleanest cities in Nigeria, the menace of flooding has more than double.
However, none of these studies measured the dimensions of drainages and their role in flood events as majority of reviewed studies only mentioned poor drainage system as a factor of flood events in Nigeria. This is the gap the research intends to fill. It is against this background that this research intends to answer the following questions:
- What is the frequency and intensity of floods in Calabar?
- What is the spatial distribution and intensity of drainage networks in Calabar metropolis
- What is the effect of drainage width and depth on flood in Calabar?
- What is the environmental state of drainage network in the metropolitan city of Calabar?
1.3 Aim and Objectives
The aim of the study is to assess the drainage network in relation to flood occurrences in Calabar. Specifically, the objectives of the study are to:
- Examine the intensity and frequency of floods in Calabar
- Evaluate the geometry of selected drainage channels in Calabar
- Determine the relationship between drainage width and depth and floods
- Assess the drainage system in Calabar
1.4 Scope and Delimitation
This study was restricted to selected areas of Calabar Metropolis that are prone to flood occurrence and one area with relatively little or no flooding and it assessed the capability of drainage networks to effectively handle run off volume in the area. The study was conducted in seven purposedly selected locations which include the Cross River University of Technology (CRUTECH) staff quarters, Akim Quo, Ediba, Yellow Duke, MCC Road, Esuk Utan Junctions and satellite town as the control. These locations are selected because they have 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. The control (Satellite town) could be said to be an area of both high and medium income earners. In this zone, squatter structures are not common. The study covered duration of six (6) month, that is between March to September, 2014 which falls within the rainy season in Calabar (Offiong and Eni, 2007).
1.5 Justification of the Study
Flooding has been identified as one of the major factors that prevents Africa‟s growing population of city dwellers from escaping poverty and stands in the way of United Nations 2020 goal of achieving significant improvement in the lives of urban slum dwellers (Action Aid, 2006). This is because many African cities lack the infrastructures to withstand extreme weather conditions. Poor urban planning together with other urban governance challenges contribute to making African urban slum dwellers most at risk.
In Nigeria for instance studies have been conducted to establish the relationship between urbanization and flooding. Many of these studies emphasized the implications of flooding on the environment and socio economic wellbeing of affected cities and the population. Offiong and Eni, (2007) concluded in their study on the effects of urban floods on infrastructure in Calabar that rainfall duration was the major determinant of runoff volume which leads to drainage infrastructure destruction in the city. Researches of Ahern, Few, Kovats and Matthies (2004); Abaje and Giwa (2007); Ladan (2007); Offiong et.al, (2008); and Eze (2008) summarise that the twin factors of poor urban planning and increased paved surfaces are the main causal factors that increase the frequencies of floods in Nigeria.
Summary, Conclusion and Recommendations
The frequency of floods episode in the city of Calabar is not unconnected to the problem of inadequate drainage networks as the study has revealed. The study indicates that about 47% of the respondent said flood occurs every year in the city of Calabar while 41.75% were of the view that they do experience flood most parts of the year. However, only 1.75% of the sampled residents claimed they have never experience flood. This response is likely to have come from those who live Satellite Town which is high brow residential area with relatively adequate drainages. On the frequency of flood, 59.5% of the sampled population supported the view that flood events are often very high while 41.75% of them said flood episode is fairly high and only 0.5% claimed flood intensity is low in the city.
The also observed that drainage dimension in the study zones vary but generally the depth and width of the drainages are not adequate for the runoff volume flowing through them hence the incessant overflowing of the banks. Specifically, the mean width of the drainages in Ikot Ansa is 64cm, depth is 58cm while the width to depth ratio is 1.10 and a total of 7 drainages were measured. On runoff volume in the station along one of these drainages, 3812% was recorded.
Similarly, in Esuk Ediba, the width, depth, and width to depth ratio is 84.8cm, 63cm and 1.34 respectively. The runoff volume was 42.10% while 4 channels were used for the study. In Henshaw Town, the dimensions of the channels is 75.3% (width), 45% (depth), width to depth ratio is 1.67 while the mean runoff volume for was 36.0%. The study also observed that in Anangtigha, the measured channels have width mean values of 61.3%, depth of 38%, and width to depth ratio of 1.61 while the runoff volume was 38.01%. A total of 8 channels were observed in Anangtigha.
CRUCTECH zone has the highest numbers of drainages (13) and the dimensions are larger compared to other zones. The mean width of the drainages in this zone is 107.6 S/%, the mean depth is 69%, width to depth ratio is 1.55 and the average runoff was 49.8%. In MCC zone, the width, depth and width to depth ratio is 82%, 56%, 1.46 respectively. A total of 3 drainages were surveyed while the average runoff volume in MCC was 32.2%. Satellite Town is high brow area where most of the University of Calabar staff live relatively good drainages that are maintain on a regularly basis. The drainage width is 55.5%, depth 36% and the runoff volume was 9S/%. A total of 4 channels were studied.
This area has little or no flood as rainstorm water flow freely without any impediments.
The study also indicates that heavy rainfall was the main factor responsible for flood occurrence in Calabar as 105 out of the 400 numbers of people interviewed blamed flood on heavy rainfall. This was followed by inadequate drainage, poor physical planning among others. It is imperative to note that different views were expressed as the perceived cause of inadequate drainage in Calabar. On the bases of this, many of the sampled population blamed it on non conformity to land use zoning, poor monitoring and government negligence.
The sampled head of households claimed that the quality of the drainages in their zone is very narrow and not well plastered. In Ikot Ansa, 65.11% of those interviewed supported the view that the have narrow drainages in their zone. In Esuk Ediba the same high response was given (75%). In Henshaw Town, 54.83% of those sampled accepted that the quality of the drainage in their area is narrow and 19.04% of the people in the same area said the gutters are not plastered properly. In Anangtigha, CRUTECH, MCC and Satellite Town, 64.28%, 79.49%, 77.17% and 25.00% of the sampled people said their gutters are narrow. On the quality of the finishing in the gutters in Anangtigha, CRUTECH, MCC and Satellite Town, the percentage distribution of the responses were 10.46%, 7.69%, 22.58%, 19.04%, 5.12%, 15.21%, and 56.25% respectively. It can be observed that a very high proportion of those interviewed in Satellite Town claimed the drainage channels are very narrow but well plastered.
The lapses in the drainage characteristics have varied effects on the environment of the study area. According to the respondents, one of the most pervasive environmental problems traced to flood is flooding of streets which prevent them from going out to do carry out daily activities. The study also revealed that whenever flood occurs, it destroys the beauty of their surrounding. In some occasions, landslide and erosion do take place and destroy their properties. The menace of flood in the city of Calabar is increasingly becoming worrisome in recent time. Poor planning and inordinate development of properties in Calabar often exacerbate the problems of flood. This is why this study makes the following recommendations.
Flood remains a very serious environmental problem in Calabar. Recurrent flood events in the city of Calabar have been traced to in inadequate drainage channels. Many properties have been destroyed, lives lost and this has subjected the people to unquantifiable trauma. More so, the menaces of flood have been on the increase as a result of incipient and prolong weather conditions.
The findings of this study was to assess drainage network and floods occurrence in Calabar Metropolis. The data collected from the field and extant literatures were used to achieve the outlined objectives. The result revealed that flood occurs every year and most parts of the season while the flood intensity ranges from very high and fairly high. On the dimension of the drainages across the seven sampled zones, only two zones hard consistent patterns of drainage width and runoff. That is, high drainage width correlated positively with runoff volume in CRUTECH and Esuk Ediba. However, other zones showed irregular patterns in drainage width and runoff volume. For instance in Henshaw Town, the drainage width is 75.3% while run was 36.OS/m. this may explain by the undulating drainage beds in some sections of the drainage as the concrete floor has been washed away by the storm water.
The study also recorded similar observation in MCC, Ikot Ansa, and Satellite Town. On the whole, it was observed that flood intensity is very high in CRUTECH zone even when very large and wide drainage channels exist in the area. The presence of waste and other household items like furniture in the gutters might have been responsible for the storm water over flowing it bounds.
Many factors were identified as being responsible for flood occurrence. Some of them include building on storm water drainages, poor physical planning, inadequate drainage channels, heavy rainfall, dumping of waste on drainage networks and nature of the terrain. This flood causing factors have created series of environmental and socioeconomic problems in Calabar. Some of which include flooding of streets, lost of life, pollution of domestic water sources, distortion of the beauty of the environment, prevented from going out among others.
In view of these, the study put forward some recommendations which when implemented will help in mitigating flood incidence in Calabar. Some of the recommendations are; the government should award contract to a competent company for the construction of underground
drainages covering the entire city of Calabar, as surface drainages have created many problems to the resident including the lost of lives, the present drainage systems should be cleared with shove is on regular basis to allow for the free flow of storm water and the government and NGOs should carry out massive awareness campaigns on the need for the people to stop dumping waste in the drainage channels. In addition, government should put in place flood early warning signal system with the capability to deliver reliable timely and effective flood information at an appropriate response time. This will help to reduce the lost of lives and properties in the city.
- Giving that Calabar is located in a tropical zone characterized heavy rainfall; the government should take proactive measure to mitigating the storm waters by clearing the drainage channel on regular basis.
- The government contract should be awarded to a competent company for the construction of under drainages covering the entire city of Calabar, as surface drainages have created many problems to the resident including the lost of lives.
- The government and NGOs should carry out massive awareness campaigns on the need for the people to stop dumping waste in the drainage channels.
- The cross River State government should re-enact the monthly sanitation exercise which will help in the total removal or reduction of waste in the drainage channels. This will not only stop flood occurrence but will also enhance the beauty and health of the people.
- Government should put in place flood early warning signal system with the capability to deliver reliable timely and effective flood information at an appropriate response time.
- Building without plan approval in every part of Calabar should be unacceptable. In fact, all structures built on drainage way of right should be demolished to reduce the carnage caused by flood.
- All roads constructed in Calabar should be provided with adequate drainages to avoid constant flooding especially during the rainy season.
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