Storm Drainage Design Project Essay Example | Topics and Well Written Essays - 1500 words - 3

Storm Drainage Design Project - Essay Example The inflow into the river after the rainfall is through different ways. The major types are overland flow which represents the surface flows which includes other direct flows into the river. The ground water flow component is the sub-surface runoff component contributing to the river discharge from a particular region after the rainfall. If the major portion of runoff water reaches the river as overland flow , a heavy rainfall would result in quick response in the river and the hydrograph shape would be peak. Thus the risk of floods would be higher in this case. While if the major share is through ground water flow the rise in discharge is slower and the repose of the river is slower. Thus the rate at which the flood waters reaches the river body determines the shape of t he hydrograph. The major factors contributing to these situations are characteristics of drainage basin, type and amount of precipitation, land use pattern in a region, impact caused by human intervention, size and shape of drainage basin and major river management measures adopted (Flood hydrograph, n.d.). The hydrograph for river Cynon is drawn based on the rainfall and river flow depth data (figure 1). The discharge in the river is plotted along y-axis and the time (in hours) along x axis. Similarly, the rainfall depth is indicated on a secondary y axis in the same graph corresponding to particular instant of time. Based on the flood hydrograph obtained for the river Cynon, it is obvious that the drainage characteristics of the terrain results in the occurrence of peak discharge soon after the rainfall. The drainage basin soil characteristics is said to have relatively low value of permeability and this results in low infiltration rates into the soil. The rising limb of the hydrograph has a very steep rise while the receding limb was not as steep. The receding limb required more time to reach the base flow condition which justified the