Question

Time of concentration Determine the time of concentration (te) for an overland flow length of 200 ft on an area in Colorado Springs, CO, with a Manning's roughness coefficient of 0.10, for a design frequency of 25 years. The rainfall intensity-duration relationship for a 25-year frequency is as given in Table 1. Take the average slope of the area as 0.005 ft/ft. Recall that the time of concentration for inlets is given by: where time of concentration (in seconds) 1-overland flow length in feet (U.S. units) or meters (S.L units) n Manning's roughness coefficient S average slope for the overland flow area i= average rainfall intensity in in/hr (U.S. units) or m/hr (SI. units) K, a unit conversion constant 56 (if using U.S. units) or 26.285 (for S.I. units) te Table 1.aif intensity-duration relationship for a 25-year frequency at Colorado Springs, Colorado. Dura 15 4.8 30 3.3 tion (min) 10 60 2.1 Rainfall intensity (in/hr) 7.3 5.7

Answer 1

Sol of 5 Yeari 4- Time of (onenhaon xo. 56メ 24.022メo2S1

Ca,094 Sec 60 sec C33 m. The ime o is 33.724 min.