Two I-I-drains are located along the road that Joins the storm drain located at mint X on the map. One from the Disease gate with the other at a distance Y, away from the storm drains at X. There are no further drains along the road until a culvert at a point, P on the map. The distance of no drains is where most flooding occurs during heavy downpour of rain. From the culvert is a drain that Joins the storm drain with double culvert at a point C. This storm drain connects to the main stream behind Nana Adam Hostel. From the Disease gate downwards is another drain that Joins the main stream represented by a blue line on the map.
This is used for the sizing of the drains. For the discharge of each drain, the rational formula will be used with the assumption that the same rainfall amount will be generated for the storms of equal intensities over the same catchments area. Rationale’s formula Q=CIA Where Q= discharge C= Run-off coefficient ‘?Rainfall intensity (mm/her. ) A?catchments area (km) Due to the fact that the site is commercial, with a high demand of parking facilities, most areas will be paved, hence the run-off coefficient of 0. 6 (for pavement) and 0. 8(for asphalt’s roads).
A freeboard of of the drain depth will be used in the drain design. The meanings formula can then use in computing the discharge capacities of the drains which is the hydraulic discharge. The meanings formula is given by; Q=Discharge of drain area of drain R=hydraulic radius N= meanings constant (0. 015 for in-situ concrete) S=slope of bed R=A/P P=wetted perimeter SLOPE OF BED A 4% bed slope can be chosen, which is high enough (;l% but ;5%) to ensure a self-cleansing velocity in the drains I-I-drains of dimensions mm*mm are designed to convey the surface runoffs from the catchments.
Here is a typical pictorial cross-section of the I-I-drains used in the design. Considering drain 1 For a given runoff (discharge) Using a I-I-drain of dimensions 600 x mm to accommodate the discharge Quadratics = For a u-drain, Area, A = 3. 142*BE/8+B (H-B/2) With breadth B = 0. Mm and Height H = 0. Mm Area, A = (3. 142 x 0. 62/8)+0. Xx (0. 6-0. 6/2) = 0. 321 ran perimeter, P = 3. 142*B/2 +2 (H-B/2) =3. 142 x 0. 6/2+2 (0. 6-0. 6/2) = 1. 1543 R = = 0. 321/1. 5425 = 0. 2781 m For a slope of 0. 003 and Meaning’s n of 0. 015 (in-situ concrete) Q 0. 27812/3 x 0. 0031/2 499 m ASS = (0. 321/0. 015) x
Positive impact on the environment The construction of drains would however have the following positive impacts on the environment; 1. This would increase the lifespan of the roads that would be constructed. 2. Since flooding is prevented life and property loss would not occur in ten event AT great storms. 3. I nerve would De a reaction In erosion on ten sleet rater drains are constructed. 4. Drains would avert the instance of stagnant water that might serve as breeding ground for mosquitoes. This would result in the enhancement of public health since malaria cases would be reduced.