A Study of Travel Time for Different Open Channels

摘要

An increase in developmental activities such as afforestation, paved surfaces and construction of buildings and other structures leads to an increase in surface runoff and peak discharge from the watershed. These all cause a decrease in detention storage and surface depression and thus diminish the concentration time that flow will take and distributes flow to the adjoining stream quickly rather than that would have taken before development or urbanization. Despite the importance of time of concentration, planners and engineers are often puzzled by different profiles of the channels and their equation available in the literature without knowing the accuracy of each formula. In this paper, kinematic wave theory integrated with the Manning's equation has been applied for the comparative assessment of the performance of the various cross-sectional channels. The result of different channel profiles toward travel time of flow has been matched for nine channel profiles. Of the nine channel profiles, it was found that the deep rectangular cross-sectional channel possesses the highest time of travel. Therefore, the use of deep rectangular channel yields lesser watershed runoff. The parabolic channel with more depth yields the lesser time of travel; therefore, the use of parabolic channel profile yields larger watershed runoff.