Page 2 of9 Hydrology & Drainage A. 23 marks 21 marks areas (flat terrain), Question A...
Page 2 of9 Hydrology & Drainage A. 23 marks 21 marks areas (flat terrain), Question A proposed subdivisionitly conslists of 30%s ropidential a 37.5% open spaces, 25%business areas and 75% T ransport Corridor Assuming that the catchment area approximates a rectangle measuring 2,400m by 3 ,800m The City's rainfall design data is derived from National Institute of Water and Atmospheric Research. The values of rainfall intensities and runoff coefficient are provided in following table. Assume the catchment has a time of concentration of 30 minutes, 60 minutes, 90 minutes and 2 hours. Calculate the catchment discharge for S-year and 20-year ABL events Rainfall Depths (mm) ARI 10m 20m 30m 1h 2h 6h 12h 24h 48h 72h 96h 120h 2 486 6.617.9 5 6.939.27 11 14.6 19.4 30.3 40 52.6 69.1 809 90.5 98.6 10 8.7 11.5 13.5 17.9 23.5 36 47 61.2 794 924 103 112 20 10.8 14.1 16.5 21.5 28 42.2 54.5 70.2 90.3 104 116 125 96.9 112 123 133 30 12.1 15.8 18.423.9 30.9 46.1 59.2 40 13.2 17.1 19.9 25.7 33 49 62.7 80 102 117 129 139 50 14.1 182 21.1 27.1 34.8 51.4 65.5 83.3 106 121 134 144 60 14.8 19.1 22.1 284 36.3 53.4 679 86.1 109 125 137 148 80 1620.6 238 30.4 38.8 56.6 71.7 90.5 114 130 143 154 100 171 218 252 321 407 592 748 941 118 135 148 159 Runoff Coefficient Runoff Coefficient 0.60 0.65 0.80 0.80 0.90 0.80 0.35 0.25 0.35 0.80 Ground Cover General Residential (Flat terrain General Residential (slopes>5%) Residential Medium/High Density Industrial Business Area Community and Major Facilities Future Urban Rural Open Space ransport Corridor May 2019