Using the TR-55 method, calculate the time of concentration for a drainage area having the following characteristics:

a. Sheet flow; dense grass, length L = 100 ft; slope S = 2.0%, 2 year-24 hour rainfall P2 = 3.5 in.

b. Shallow concentrated flow; unpaved, length L = 250 ft, slope S = 1%

c. Stream flow; Manning’s n = 0.06, flow area A = 9 ft2, wetted perimeter P = 11 ft, slope S = 0.7%, length L = 700 ft.

The watershed area is 10 acres.