Question

Q1. 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 (C -0.36), 30 acres is clayey loam pasture land (C) -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. Given Iso arres As Ca. 53 40 ij Drainage area (acres) A1 A2 A3 Time of concentration (min) 60 40 42

Answer 1

for Al for Az For Az G= 0.21 A, z 40 acres = 0.36 An - 80 acres = 0.30 Az = 30 apres I Here het us assume uniformn rainfall intensity Qi= GIAI 02 2 GIA2 20.36X8OXI 0.21x401 28.4I 83 = C IA3 = 0.30X30X I = 28.81 91 For total area С 2 GAI + GA₂ +₂ A3 At Azt A3 8.4 +288 +9 2 20.308 () ISO Opz 0.308 x 150 xS z 46.21 Let usa jassume qe vainfall if (merilha so there we will be usingt, The discharge & for Az s masem, so we will use te= 40min