peak discharge in ents) Using the following information and the \"Rational Equat
ID: 299580 • Letter: P
Question
peak discharge in ents) Using the following information and the "Rational Equation" Qs- Ci A determine the peak discharge in cfs from a undevelo Problem 1 (20 20 acre undeveloped piece of land that has a time of concentration 40 minutes is the peak discharge if the land receives a 25 year storm? What if we went back to e site is developed and has a time of concentration of 20 minutes and is developed for neighborhood business? Which results in the greatest increase undeveloped land, or a 5 y in peak discharge, a 25 year storm on for the "Rational Equation" are Qr are on the next page. ear storm on developed land? Why do you think that is? Please note that the units (cts) C (dimensionless) i (in/hr) A (acres). Necessary figures and tables Pre-development, 5 year storm- cfs maximum discharge year storm = -cfs maximum discharge year stormcfs maximum discharge Post-development, 5 year storm Which was greatest, pre/25 or post/5? Why, in your opinion (use equations to back up your explanation if possible)? Use the space below only to answer this question.Explanation / Answer
We know that
Qp = CiA where Q = peak discharge , cfs C = Rational method runoff coefficient i = rainfall intensity , inch/hr A = drainage area, acre
Note: Rainfall intensity at e duration is equal to the time of concentration.
(i) Pre-development, 5 year storm = 800 cfs maximum discharge
i.e. Qp = CiA = 1 × 40 × 20 = 800 cfs where runoff coefficient adjustment factor of 5 years recurrence interval is 1.0
(ii) Pre-development, 25 year storm = 880 cfs maximum discharge where runoff coefficient adjustment factor of 25 years recurrence interval is 1.1
(iii) Post-development, 5 year storm = 400 cfs maximum discharge
Pre- development peak discharge of 25 year storm was greatest.
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