Abstract
This study examined the administration of drainage
policy and impact on health in Gwagwalada area council FCT, Abuja 2015-2019. This
paper focuses on the overall situation of the drainage system, environmental
impact and health hazard of urban people by unplanned drainage system of Gwagwalada.
This work includes some lab test (Water test), questionnaire survey and
collection of drainage maps. Inadequate drainage sections, conventional
drainage system with low capacity and gravity, natural siltation, absence of
inlets and outlets, lack of proper maintenance are the prime causes of blockage
in drainage system.Physical planning efforts have to be
drastic, radical and deterministic towards sustainable drainage and erosion
channels. There must be massive investment in dredging and re-dredging of the
existing drainage network and channelization of the new suburbs.
CHAPTER ONE
INTRODUCTION
1.1 Background of the study
Water is the main contributor to the failure and damage of roads. Water can be in the form of ground water, surface water (streams and rivers) or rain, as runoff from the surrounding areas. In addition, water may flow laterally from the pavement edges or it may seep upward from a high ground water table. The water flow can damage the road in several ways. Rokade et al (2016) reported that water-related damage to pavement can cause one or more of the following forms of deteriorations: a) reduction of base, subbase and sub grade strength, b) differential swelling in expansive sub-grade soils, c) stripping of asphalt in flexible pavements, d) frost heave and reduction of strength during frost melt, and e) movement of fine particles into base or subbase materials resulting in a reduction of the hydraulic conductivity considerably. The damage to the road can be reduced if the flow of water is controlled. Minor damages can easily be repaired as part of the regular maintenance provided to the road and its structures. If the flow of water is not properly managed, the deterioration of the road will be more serious and occur more rapidly. This will lead to higher maintenance demands and in the worst cases result in serious damage which may obstruct the traffic flow.
Drainage system is a process of removing & controlling excess surface water with in right of way. Drainage is an important feature in determining the ability of given pavement to withstand the effects of traffic and environment. (Adequate drainage is very essential in the design of highways since it affects the highway’s serviceability and usable life. If ponding on the traveled way occurs, hydroplaning becomes an important safety concern. Drainage design involves providing facilities that collect, transport and remove storm water from the highway (O‟Flaherty, 2002).
The objective of drainage system is to prevent onsite water standing on the surface and convey the offsite storm runoff from one side of the roadway to the other. To carry out the offsite drainage. Culverts are closed conduits in which the top of the structure is covered by embankment. United States National Bridge Inspection Standards (USNBIS, 1990) and ERA drainage design manuals (ERA DDM, 2002 and 2011).
As the water can cause a serious impact on both the road access and its strength, an efficient drainage system is the most important part of road construction and maintenance works. Good drainage needs to be taken into consideration at the early design stages in order to secure a long life for the road. With a well-designed drainage system, future rehabilitation and maintenance works can be considerably reduced and thus limit the costs of keeping the road in a good condition.
Ensuring good drainage begins when selecting the road alignment. A Centre line that avoids poorly drained areas, large runoffs and unnecessary stream crossings will greatly reduce the drainage problems. Provision of sufficient drainage is an important factor in the location and geometric design of highways. Drainage facilities on any highway or street should adequately provide for the flow of water away from the surface of the pavement to properly designed channels. In addition, traffic may be slowed by accumulated water on the pavement, and accidents may occur as a result of hydroplaning and loss of visibility from squish and sprig. The importance of enough drainage is recognized in the amount of highway construction dollars allocated to drainage facilities. About 25 percent of highway construction dollars are spent for erosion control and drainage structures, such as culverts, bridges, channels, and ditches (Wyatt et al, (2000). Surface drainage encompasses all means by which surface water is removed from the pavement and right of way of the highway or street. A properly designed highway surface drainage system should effectively intercept all surface and watershed runoff and direct this water into adequately designed channels and gutters for eventual discharge into the natural waterways. Water seeping through cracks in the highway riding surface and shoulder areas into underlying layers of the pavement may result in serious damage to the highway pavement.