QUESTION A4 (8 marks total) a) Using the urban rational method, calculate the peak flow from a park with a catchment are

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Question A4 8 Marks Total A Using The Urban Rational Method Calculate The Peak Flow From A Park With A Catchment Are 1 (275.96 KiB) Viewed 40 times

QUESTION A4 (8 marks total) a) Using the urban rational method, calculate the peak flow from a park with a catchment area of 0.7 hectares for the 10 year ARI rainfall event. The flow path length is 90 metres and slope is 3% and percentage imperviousness is 0.2. The roughness (n*) is 0.17. Rainfall intensities at the site for the 10 year ARI rainfall event are provided in the Table 3. [6 marks] The following equations may be useful: 6.94((Ln*) 0.6) t₁ = 10.450.3 C100.9f+(1-f)(0.1 +0.0133(110,1-25)) Table 3. Rainfall Intensities for 10 year ARI event Storm Duration Rainfall Intensity 10 (minutes) year ARI (mm/hr) 5 150.1 10 130.3 15 121.1 20 105.5 25 87.1 30 71.0 45 61.1 60 47.3 90 39.3 119.8 120 b) If the park was now paved, would the peak flow would decrease or increase decrease? In your answer you should explain how the equations you used in part a) explain the increase or decrease. [2 marks]