problems_chapter 8

problems_chapter 8 - Problems Chapter 8 Janet Barco CEE 151...

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1 Problems Chapter 8 Janet Barco CEE 151 Winter 2008 If you see typo errors….let me know
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2 Problem 1 500 acres watershed, 70% grass (Runoff Coef. = 0.45), 30 % forest (Runoff Coef. = 0.35),. Estimate the peak flow for 30 min storm and 50 years frequency using the Rational Method. Solution CIA Q = Form the IDF curve (next page), the rainfall intensity is = 6 in/hr C = Runoff coef. = (0.45*0.70)+(0.35*0.30) = 0.42 Q=0.42*(2.5 in/hr)*500 acres I : [in/hr] A: [acres] If : Q: [cfs] Q= 525 ft 3 /s
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4 Problem 2 Watershed with an area of 3 mi 2 , slope of 3% and hydraulic length of 1.2 mi, receives 6 in of rainfall. If has a land-use of 40% residential (1/4 acre lots), 25 % open space in good condition, 20 % commercial + business (85 % impervious) and 15% industrial (72 % impervious). Corresponding soil types are C,D,C and D. What is the runoff peak?. solution Land use Soil group Curve number Residential C 83 Open-Space D 80 Commercial C 94 Industrial D 93
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6 CN=(0.40)(83)+(0.25)(80)+(0.20)(94)+(0.15)(93)= 86 () S 8 . 0 P S 2 . 0 P Pe 2 + = 10 86 1000 10 CN 1000 S = = S = 1.63 ( ) [] 63 . 1 8 . 0 6 63 . 1 2 . 0 6 Pe 2 + = Pe = 4.42 in precipitation excess Using SCS unit hydrograph you can get the runoff peak
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7 Step 1: compute t c () 5 . 0
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This note was uploaded on 03/11/2008 for the course CEE 151 taught by Professor Mugg during the Spring '08 term at UCLA.

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problems_chapter 8 - Problems Chapter 8 Janet Barco CEE 151...

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