Effectiveness of Drainage Networks on Floods in Calabar Metropolis, Nigeria
Chapter One
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
CHAPTER TWO:
CONCEPTUAL FRAMEWORK AND LITERATURE REVIEW
CONCEPTUAL FRAMEWORK
This study employed the concepts of sustainable urban development and that of General System theory to analyze drainage networks and floods events in Calabar metropolis. The concept of sustainable development is employed to emphasize that it is as a result of unsustainable development that floods are common in our urban centers. Inherent in this concept is the need to imbibe development controls while the general system theory is employed to underscore urban connectivity. It is only when development practitioners see master plan as a mesh of connectivity that the problems of inadequate drainages and flood occurrences associated with it can either be stopped or reduced in urban centers.
SUSTAINABLE CITY DEVELOPMENT CONCEPT
Successful national economies depend on well-functioning and resilient urban centers. Urgent action is needed now both to address urban centers current vulnerabilities to extreme weather and to build into expanding urban centers protection from likely future changes (Satterthwaite et al, 2007). The quality of the urban space is vital to sustainable livelihood; it is important to understand the relationship between sustainable development and flood occurrence especially in an expanding city like Calabar. The concept of sustainable urban development was advanced to help cities cope with increasing environmental challenges.
The concept of sustainability was coined in 1972 at the United Nations Conference on the Human Environment in Stockholm. It means that sustainable development is a kind of development that considers supplying todays need without decreasing posterity ability to supply their needs. In fact, sustainable development and management is development that considers creating, maintaining and increasing life quality of all human kinds in all periods of time (Mannion, 2002).
After the United Nations 2005 World Summit Outcome Document refers to the “interdependent and mutually reinforcing pillars” sustainable development is considered as economic development, social development, and environmental protection (Zhangh, Zhangh, and Yongzhi 2011). As the rapid growth of world population and its concentration in cities around the globe takes place, sustainable urban development has constituted a crucial element affecting the long-term outlook of humanity.
In order to achieve sustainable urbanization, cities need to develop social and economic structures without damaging the environment, and achieve a balance between the human inhabitants and the natural resources (Abu-Ghazalah, 2008). However, urban areas are complex and are constantly changing. Many cities in the developing countries have older forms of planning, and are surrounded by large informal settlements or slums (UN- Habitat, 2009). This is the case in Calabar where most of the traditional houses are without adequate drainages to contend with the volume of storm waters.
A more disturbing issue is the lack of attention to the promotion of sustainable environmental management especially in disaster prone areas resulting in devastations which could have been averted. Sustainable urban planning should avoid harm before the need for mitigation measures. The provision of green infrastructure should be an integral part of the creation of sustainable cities throughout Nigerian towns and cities. Surface water drainage methods that take account of quantity, quality and amenity issues are collectively referred to as Sustainable Urban Drainage Systems (Jimoh, 2008). These systems are more sustainable than conventional drainage methods because they: Manage runoff flow rates, reducing the impact of urbanization on flooding protect or enhance water quality.
Sustainable urban drainage systems are now a requirement in all but the very smallest of new developments and are a key method of ensuring that existing flooding problems within the area are not made worse. The planning system should take the possible impacts of climate change, for example greater rainfall and increased risk of flooding, into account when taking decisions on the locations of new development and other changes in land use (Aderamo, 2008).
The concept of sustainable urban development calls for effective and efficient planning of urban space. Physical planning involves the reconciliation of land uses, provision of the right site for the right use, control of development, provision of facilities, services and public goods, preservation, protection and conservation of resources, preservation of heritage among others (Oduwaye, 2009). It ensures compatible land uses, guarantees orderly development and provides functional and visually pleasing environment and satisfactory services in a sustainable manner.
CHAPTER THREE
RESEARCH METHODOLOGY
The survey research design was used in this study. The design involves the collection of data about a phenomenon with a representation sample by the use of questionnaire, interview and appraisal approach (Ndiyo, 2005).
RECONNAISSANCE SURVEY
A Reconnaissance survey of Calabar was undertaken to identify flood prone areas. Using information obtained from literature on flood in the city of Calabar, couple with verbal discussion of residents of the city, the researcher identified areas that are often flooded whenever it rains. The reconnaissance assisted in the determination of suitable location for the establishment of the measurement points. At the end, a distinct area with well-defined boundaries was identified. Thus, flood volume data were collected from the following locations; IkotAnsa, EsukEdiba, Henshaw Town, Anangtigha, CRUTECH, MCC and a control was established at Satellite Town. Questionnaire were administered to residents of the selected streets in accordance with the guide outline in the procedure for data collection.
CHAPTER FOUR:
RESULTS AND DISCUSION
INTRODUCTION
This chapter is concerned with the presentation, analysis and discussion of data obtained from the field through direct field measurement, questionnaire administration and secondary data analysis.
CHAPTER FIVE:
SUMMARY, CONCLUSION AND RECOMMENDATIONS
SUMMARY
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.
CONCLUSION
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.
RECOMMENDATIONS
- 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
- 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
- The government and NGOs should carry out massive awareness campaigns on the need for thepeople to stop dumping waste in the drainage
- The cross River State government should re-enact the monthly sanitation exercise which willhelp 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
- Government should put in place flood early warning signal system with the capability to deliverreliable timely and effective flood information at an appropriate response
- 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
- All roads constructed in Calabar should be provided with adequate drainages to avoid constant flooding especially during the rainy
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