Storm Drainage Study Essay Example | Topics and Well Written Essays - 1500 words

Storm Drainage Study - Essay Example A line graph is usually used for the discharge over time. Rainfall is plotted with the use of a bar graph. There are several factors that control the shape of a hydrograph. The different shapes are shown and the main components are labelled according to Weyman, 1975. Hydrographs have differences between the peak rainfall from its peak discharge. The difference is the lag time. If the lag time is great, there is a less chance of flooding. A short lag time will indicate that water had already reached the river channel at a fast rate. The rise in discharge shown in the is called the rising limb, and the decrease in the discharge is called the falling limb. The larger size means that there is longer lag time as water has a longer distance to reach the river trunk. The shape of the basin is normally elongated and produces a lower peak flow and longer lag time than a circular basin with the same size (Gillesania,2006). The line graph illustrates the change in height of water in the river over time, while the bar graphs illustrates discharge of water in the river with respect to time. The study was taken for 96 hours or 4 days. It was done continuously, taking the height reading every hour for 96 hours. All the readings vary from each other. In its analysis, there was almost a steady flow of water from the start up to 42 hours. After 42 hours, the water in the river began to rise. The rising of the water is called the process of rising limb. The time between the rise of water and the time the water reaches its peak is known to be the basin lag time. It reached the peak flow at the 57th hour in the study. This means that water had reached its peak discharge and is now starting to fall down. From the peak point, when the water height starts to fall down the process is called recession limb. After the recession limb, the water discharge will normalize. Channel Design Given data are: Apply the Manning formula to design a suitable breadth b, with Q = 1.1 m2s the given data of discharge of the channel d = 0.6 m n = 0.015 where: v = velocity, m/s S = 0.0005 R = hydraulic radius v = R2/3S1/ 2 S = slopen n = Manning's coefficient of roughness A = db A = cross-sectional area b = breadth Q = Av d = depth wetted perimeter = 2d + b v = R2/3S1/ 2 n Requirement = width of base b of the open channel Discharge Q of the river into the open channel Design of water pump to discharge water from the river to the open channel Computations: A = db = (0.6)b Wetted Perimeter = 2d + b = 2(0.4) + b = 0.8 + b = 0.8 + b. Q = Av 1.1 = 0.6b 1.1(0.015) = 0.6b 0.0165 = 0.6b = b 1.2406 = b = b3 1.9093 = b3 1.9093 = b3 1.9093 = b3 1.9093(1.44 + 2.4b + b2) = 0.36b5 2.7494 + 4.5423b +