Question

QI. As shown in the figure, the total drainage area of the catchment is 150 acres, 40 acres is light forest cover (C = 0.21), 80 acres is lawn grass (C2 = 0.36), 30 acres is clayey loam pasture land (C3= 0.30). If the three drainage areas are contributing flow at a storm water inlet. Find the time of concentration that has to be used for design purpose. Az Crn Czy ci Drainage area (acres) Al A2 A3 Time of concentration (min) 60 40 42

Answer 1

Giveni A1 = 40 acres (=0.21 A2 = 80 acres 2 = 0.36 A3 = 30 acres C3 20.30 T, = 60 min T2 = 40min T3 2 42min Time of concentration = {Ai Citi { Ai Ci

40xo:21х60 + 3OXO-30х40 + 30x D, 30 x — 4ox 0-21 + 30х0-36 + 3OX 0-30 2034 Боч + 152 +313 46-2 3. 4 + 28. 8+ 9 Т- 24:02 ,