CIV E 444 - APPLIED HYDRAULICS FALL 2009 HOMEWORK No. 12 Given a basin with drainage area = 355 mi2, 24-hr rainfall = 5 in, and time of concentration = 4 hr. Calculate a maximum peak discharge by the Creager formula, and compare with the maximum value that is possible with TR-55. Use ONLINE TR55. A watershed in coastal Southern California has a drainage area = 6.8 mi2, 24-hr rainfall = 4.5 in, and time of concentration = 1 hr. The current estimated CN = 80. What reduction in CN would be necessary through watershed improvements in order to reduce the peak discharge to less than 80% of the current estimated value? Use ONLINE TR55. A compound river cross section is estimated for simplicity to be a prismatic 8-point section, with inbank width = 100 ft, depth = 10 ft, mean velocity = 5 fps, and Manning's n = 0.03; and flood plain width (on each side) = 500 ft, depth = 2 ft, mean velocity = 2 fps, and Manning's n = 0.05. Determine the velocity coefficient α applicable to this compound cross section. What is the Darcy-Weisbach friction factor in a channel with Q = 7.2 m3/s, b = 1.2 m, z = 1, So = 0.0006, and n = 0.013? [Hint: Find critical slope using ONLINE CHANNEL 04].