Introduction
Drainage system is a system constructed for the purpose of draining waste water from our homes and surrounding in other to avoid accumulated waste water in our environment. It also helps to channel storm or runoff water during raining season in other to avoid flooding and presences of stagnant water (Park, 2007). Poverty has forced many to occupy areas prone to floods and mud landslides in area which has no good drainage system. Due to these, as observed in Caracas, Venezuela over half a million people lived in the flood prone areas and so many lives and properties have been claimed by this hazard (Watchtower Bible and Tracts Society, 2005).
In a news report by D.B.S. during the 2002 flood credited to NESREA, stated that maintenance of waterways and the avoidance of dumping of waste into water body should be ensured to permanently eradicate flood. In words of Lambert (1988), poor planning as it has to do with the hydrological and topical characteristics of some areas, runoff is forced to flow along the roads, gutters and overflow into depression where seasonal lake develop which would ultimately flood with subsequent rain.
Sule (2001) has given examples of cities where houses are constructed directly on drain channel to include Lagos, Calabar and Ibadan, and that this practices has resulted into blockage of storm drains and consequently leading to inundation and flooding of streets.
Drainage system is defined by law as the conveyances by means of a sink and any other necessary appliances of waste water and the conveyance of rainwater from roof. Olojoba (2009) define drainage system as a system that conveys foul matter water and flood water from the building to public sewer or septic tank installation foul of water is the discharge from W.C.S basins, baths and sinks and surface water.
Type of drainage system
David (1998) stated that drainage systems can fall into several categories, depending on the topography and geology of the land. He outlines the types of drainage system as followings.
- Dendritic drainage system.
- Parallel drainage system.
- Trellis drainage system.
- Rectangular drainage system.
- Radial drainage system.
- Deranged drainage system.
- Annular drainage system.
Dendritic drainage system
Dendritic drainage system is the most common form of drainage systems. In a dendritic drainage system, there are many contributing streams (analogous to the twigs of a tree), which are then joined together into the tributaries of the main river (the branches and the trunk of the tree, respectively). They develop where the river channel follows the slope of then the terrain. Dendritic system form V-shaped valleys as a result, the rock types must be impervious and non-porous.
Parallel drainage system
A parallel drainage system is a pattern of rivers caused steep slopes with some relief. Because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction. This system forms on uniformly sloping surface, for example, rivers following southeast from the Abandare Mountains in Kenya. (Zonn,1976).
Trellis drainage system
The geometry of a trellis drainage system is similar to that of a common garden trellis used to grow vines. As the river flows along a strike valley, smaller tributaries feed into it from the steep slopes on the sides of the mountains. These tributaries enter the main river at approximately 90 degree angles, causing a trellis-like drainage system. Trellis drainage is characteristic of folded mountains, such as the Appalachian Mountains in North America. (De Jong, 1979).
Rectangular drainage system
Rectangular drainage develops on rock that are of approximately uniform resistance -to erosion but which have two directions of jointing at approximately right angles. The joints are usually less resistant to erosion than the bulk rock so erosion tends to preferentially open the joints steams consist mainly of straight line segments with right angle bends, and tributaries join larger streams at right angles (Osterbaan, 1987).
Radial drainage system
In a radial drainage system the streams radiate outwards from a central high point. Volcanoes usually display excellent radial drainage. Other geological features the drainage may exhibit a combination of radial and annular patterns (Sharma, 1992).
Deranged drainage system
A deranged drainage system is a drainage system in drainage basins where there is no coherent pattern rivers and lakes. It happens in areas where there has been much geological disruption. The classic example is the Canadian Shield. During the last ice age, the topsoil was scraped off, leaving mostly bare rock. The melting of the glaciers left land with many irregularities of elevation, and a great deal of water to collect in the law point explaining the large number of lakes which are found in Canada. The water sheds are young and are still sorting themselves out. Eventually the system will stabilize (Bos, 1994).
Annular drainage system
In an annular drainage pattern streams follow a roughly circular or concentric path along a belt of weak rock, resembling in plan a ring like pattern. It is best displayed by streams drainage a maturely dissected structural dome or basin where erosion has exposed rimming sedimentary strata of greatly varying degree of hardness, as in the red valleys, which nearly encircles the dome structure of the block hills of South Dakota (Rao, 1992).
Reasonable basis for the provision and maintenance of community drainage system
John (2011) noted that the provision and maintenance of a community drainage system with satisfactory gradient would effectively lead away any storm water or run off, thereby preventing outbreak of landscape disease, erosion, flooding, collapsing home, lost of biodiversity, hardship and other ecological problems while absence or poorly maintained community drainage would be blocked by sediment and particles present. In run-off and consequently lead to flooding collapsing home, biodiversity lost and death. The fact that poor drainage system is capable of claiming life and destroys properties is a satisfactory reasonable basis for the provision and maintenance of drainage system in all communities.
Causes of poor drainage system
According to Pidwimy, (2006) there are many factors that lead to poor drainage system, they are as follows.
- The materials used for the construction.
- Lack of maintenance.
- Attitude of people that are using the drainage system.
Materials used for construction
There are materials used for constructing drainage system, if these materials are not strong and they are used the drainage can not last long because the materials that are used are not strong so it can lead to breakage or collapsation of the drainage there by obstructing then flow of storm water and at a time stagnant water leading to an area where mosquitoes breed and if not taken care of can lead to flood. So materials used for construction should be up to standard.
Lack of maintenance
This is on both the part of the government and the community. The government should put personnel’s in place so that the drainage system will be maintain in case of blockage it can be taken care of by the personnel’s so that the water can flow very well if this things are put in place by the government it will help to prevent flooding and other diseases.
On the part of the community they should not always wait for the government they should help to dear and clean the drainage always so that the storm water can flow very well. There should be rules that are binding every individual in the community. So that they can be clean and maintain the drainage system. If these things are put in place, it will help to prevent flooding and occurrence of diseases.
Attitude of the people using the drainage system
This is the character of the people or the way people make used of the drainage system. You will find out that some people purposely blocked the drainage system with sand simply because they want to drive into their premises or because they are constructing a house so they have to make way for the vehicle that are coming in so they block it with sand it is not right.
Those who are trading are not left out after trading the waste that was generated by them; they will throw it right inside the drainage system. This is not right; there should be law that is binding the drainage system so that it will not be blocked by the individuals and to avoid disaster like the one that happen in Lagos and Ibadan (Wijdieks, 1994).
The problem of poor drainage system
According to Cairn (1986) many low income communities in developing countries consider storm water drainage to be their most urgent need as far as urban infrastructure is concerned. This is partly because their houses are often built on unsuitable land. In areas sufficiently close to the city centre for journey for work to be afford, or on which the owner’s will allow them to stay as squatter in land that is in suitable for other purpose. This is often on steep hill sides subject to erosion and landslides or it is law-lying, marshy land often subject to flooding.
Park (2000) stated that even in the arid areas where average rainfall is low tropical when it comes is more intense than in temperate than in the temperate climates, and the lack of vegetation and of adequate drainage means that torrents of water can form in minutes causing damage to homes and properties which will take years to repair, Rain-water is not tile only problem. Leaking water mains, waste water from washing and bathing and the sewage from overflowing septic tanks and blocked sewers constitute health hazards, damage buildings and cause flooding if an adequate drainage system does not exist.
Edward (2010) stated that construction of drainage are of particular concern, soil erosion is an important problem both at its source and downstream of development site. Lost soil will be deposited somewhere and the location of the deposition could alter downstream hydrology and increase flooding. It may also pose a water quality issues directly as a result of situation and indirectly from contaminants carried with or attached to soil particles.
These changes in surface hydrology and water quality due to poor drainage system could have adverse impact in aquatic species such as fish, plants and microbes. It can also increase turbidity, temperature and pollutant lead which could be devastating to aquatic environment and humans (Source: Community Guide to Developmental Impact Analysis by Edward).
The result of poor drainage system is great hardship for inhabitants who become impoverished and deprived.
Public health implication of poor drainage system
Amadasum (2000) further stated that the stress produced by bad drainage causes a great deal of mental illness. He also stressed that those who live in slum areas have poorer health than those whom live in good residential districts, and that there quarter of incidence frequency of complication are common feature of poor drainage system.
He said that poor drainage is a contributing factor to the cause of mental illness, and also prevent the development of normal family relationship. He also outlined the following associated hazard.
- It causes nervousness, irritability bad temper, mental unrest, behavioural and personality disorder and mental break down.
- It encourages total infestation of vectors and vermin’s which transmit disease and also cause discomfort.
- It promotes the spread of disease such as cholera, typhoid and increases infant mortality.
Diseases associated with poor drainage system
1) Schistosomiasis:
In countries where schistosomiasis is endemic, poorly drained urban areas present ample opportunities for transmission of disease. Contamination of standing water with the faeces of infected persons (or for one form of the disease, with their urine) enables the schistosomiasis the microscopic parasite that cause this infection to reach the small aquatic snails in whose bodies they multiply from every infected snail, thousands of shistosomes emerge and swim in the water. Local residents because infected when they enter the water and the shistosomes penetrate their skin.
Schistosornaisis be thought of as a rural disease, but it is often no less prevalent in urban areas where drainage is lacking. Some of the species of the snail host thrive and breed rapidly in heavily polluted stagnant water which often accumulates there. Moreover, a single infected person in an area can cause sufficient contamination to infect very large numbers of the people living in his or her crowded neighbourhood because even a small number of snails, once infected, can produce many thousands of schistosomes over a long period of time (Caircross, 1986).
2) Malaria
Another important group of disease related to poor drainage is transmitted by mosquitoes. Deferent species of mosquito and each chooses different bodies of water in w which to breed in flooded areas, some in drains themselves if they are blocked by rubbish or vegetation or are laid unevenly so that there is standing water in them. Malaria is the best known of mosquito-borne infections, and is transmitted by anopheles species, many of which bite animal as well as humans. Transmission can be particularly intense in urban areas where there are relatively few animals to divert the victor species of mosquito from human blood meals. Anopheles mosquito do not usually breed in heavily polluted water, but can multiply in swaps, pools puddles and also in streams and storm water canals in which there is standing water. Anopheles mosquito breeding in poorly drained areas can transmit malaria to adjacent parts of the town. A particular danger in a city is the significant amount of international travel to and from it, which increases the risk of importation of new and possibly drug resistant strains of the malaria parasite (Tabibzadeh,1989).
3) Filariasis:
Feachem, (1981) said that finally, there is the particularly urban problem of bancroftian filariasis, which appear to be the original vector of transmission in urban areas by the culex pipiens groups which generally multiply in heavily polluted bodies of water transmission of the disease is a relatively inefficient processes, so that many years of exposure to intense night time mosquito biting are needed for the average case to develop.
Nevertheless, more than 80 million people in the developing world are infected. In many countries such as India, it is especially prevalent in urban areas. Filariasis transmission by culex pipiens mosquito is now common in Asia, is occurring in cities on the eastern coasts of Africa and South America, and may soon begin in the large poorly drained urban areas of West Africa where both the disease and the vector already exist.
Drainage construction is an effective mosquito control measures. It is cheaper than application of insecticides and does not have to be repeated regularly, in many cases, it cost more than a year’s supply of insecticides, it can have no detrimental effect on the environment, on the contrary, it constitutes an environmental improvement. Moreover, the danger of mosquito developing resistance, as they have been known to do to insecticides does to apply.
Quality of a drainage system
Qualities of a drainage system is as follow according to Olojoba (2009);
- The drainage should be constructed of hard, smooth, impervious materials
- The drainage should be laid on a sound foundation to a suitable and even gradient to ensure a self cleansing velocity.
- The bore should be circle and invert even.
- Length of pipes should be true a straight lines between changes of direction to obtain a truly cylindrical bore.
- Adequate means of access should be provided for inspection and cleansing.
- Adequate ventilation should be provided.
- Branch drains should be laid on straight lines to join the main line in the direction of low.
- Where bends are used, the junctions curved obliquely.
- All openings of the drainage system, except ventilation openings should be efficient trapped, having a seal of not less than 50 mm.
- Except in the cases of necessity nom drain should pass under building.
- A drainage system should be tight.
- Where a drainage trench passes near a lead bearing part of a building concrete backfill is required.
Principle of constructing drainage system
Huyskes, (1994) said that the following points must be put into consideration and application if an effective drainage layout is to be executed.
- Type of soil where drainage is to be constructed.
- Topography or tertian of the community or area.
- Individual residential capacity for constructing the drainage.
- Types of drainage system to be provided in residential buildings, industrial areas, markets, highly commercialized areas, traffic congested areas, slum and marshy areas, waste treatment areas.
- Sizes, volume, length and depress of drains to be constructed.
- Water sources and storm or run-off water courses in the area.
- Government policy and finance.
Remedy to the problem of drainage system
Offiong (2008) outline the following as remedy to the problem of drainage system.
- Greening the area is encouraged.
- Ensure proper connectivity of the drainage system.
- There should be provision of drainage facilities in every street and road.
- Expansion of width, length and depth of drainage systems.
- Used of quality materials in the construction of drainage facilities.
- An effective drainage design and technical capabilities should be improved.
- Routine reporting, monitoring and evaluation should be made.
- Create laws that will allow punishment of those who dump their waste products in the drainage channel.
With the recommendations stated above and assurance that government will do something about poor drainage system in the area; there definitely will be improvement in the metropolis environment more so when it rain.
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