QUESTION 1 The desiga storm intensity of a 37,500 a 2 lot in Perth, Australia is

Question

QUESTION 1 The desiga storm intensity of a 37,500 a 2 lot in Perth, Australia is 64 in/hr and the weighted runoff coefficient is 0.79. You need to specify the minimum size concrete pipe needed to convey the flow from that lot's inlet to the next do instream inlet, which is 350 feet away on a slope of0.1%? 0 a.27 inches O b.18 inches 06.21 inches o d 15 inches 24 inches o f 12 inches QUESTION 2 Determine the peak rnort. Q'or·sor.., normfor . drainage basin in whreve, vA having the "esowing paramesert A Area47 acre 8 Time of concentration l. Overiand now-average Era". 100 feet long, 15%·verage siope ", shallow concentrated now-a2s-feet long. S S %·verage 'iepe m. Strean, now-450-feet. natural channel (n·006). 1.25% average bed i100€, trapeioidai eroaa section with . bottom width e, 3-est and ace alopes a, ( C Runoff Coeticient L Single Family houses-4 acres Suburban residential-5 acres Light industrial-6 acres IV. Parking lot-3 acres V. Grass- 12 acres Woods-17 acre

Explanation / Answer

1) from rational method,

Design flow,Q= CIA,

Coefficient of runoff C = 0.79,

Intensity of rain I = 6.4 in/hr,

Area = 37500 sqft = 0.861 acres

Therefore, Q = 0.79*6.4*0.861=4.353 cfs

Q= 4.353 cfs= 0.123 cumecs.

Manning formula Q=(1/n)*(R)^2/3*(S)^1/2*A.

Where Q=0.123 cumecs.

For concrete pipe n= 0.013,

R= D/4,

S =0.1%=0.001,

A= pi (D^2/4)

substitute all values in above manning equation,we will get diameter of pipe, D= 0.505 meter.

Therefore dia of pipe D = 21 inches,

Option C is correct.

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