Question

Develop the 15-min Clark unit hydro graph for a 2.17 mi² (1389 acre) urban watershed that has a flow path of 1.85 mi, a slope of 30.5 ft/mi, and an imperviousness of 21 percent. A rainfall intensity of 2.56 in/hr is to be used. The time of concentration for the watershed is computed using

T_c = 11.4 L^0.50 K_b^0.52 S^-0.31 i ^-0.38

where T_c is the time of concentration in hours, L is the length of the longest flow path in miles, K_b is a watershed resistance coefficient (K_b = -0.013751ogA + 0.08), A is the watershed area in acres, and S is the slope of the flow path in ft/mi, and i is the rainfall intensity in in/hr.

Answer 1

Iolokon:- 0 6534- 9.u-13P AID: 55lo212012 3ind the walesshed Resislance coeRicient usina the k6 = -0.00625109 A +0.08 Donate uatexxesislance coepp,cient Sub litokįpatk value o,33 aces fo A in equaon -L-0.006 25 log x1389)+0.0% the lime o Concentsation Yoś woteasted using the osmula C2) Donale time a conentsaon besslance coerpici ent as kbhe Plou pa as

050 0.52 X 30.5-0.31 X2.56-0.38 06 hss Time o conentaon o the oaleashed is 10-62 hss Ind he slosage coePRicient usirg the nda 0.50-30 . - - 3 Donale walexshedeo etoooge CoefFicient aS R.and conta balh -ng oxea inmi as A ubeRiule he values oP85 L21a m f A and 0.623 hosPo Te n eapakon to aet 0.5 R-0.37 XO. 678 1.11 x 2.13-0 .80 O.254 uwatesshed slozoge coepficient 0.54

(ut) coeppicient as R, andTme inleaval as Δ6.SobShkle the value op 0-254 oz R. and 0-5 os At in egpahon (u)to aet 2X 0.25 C- (2x D 254to-23) ind he me-axea velalionships usinhe foamula 七 Donale Cn taiboling Abea at ime t os A. Total uoalesshed avea as Ac, and time o co ncentaation aes To

Subs įtUle the value op 0.510% 촐 in egualion Cs)toget 1-5 -1.414 (0.367) = 1-1.414(1-1)'. cakolale nvesge Inslanloneaus Roosing e Pamuola Avexoge Instantaneou ou osing he e tosmula ve . 3.600se ponale intzemental avea beseen sunalp s ochzones as AA, andl Time Incsement ost 25 time inlesval Sobskilole he values oP3-l2k At in equlon o get

ave t m2lkm2 6.22 mssec At nequation (a) to aet o.Shs 3.600 sec = 11.69 M 31sec. ind Rook Donate outPlous com the (ineoz sese v ae lave,b Subsitle the values op 066as,and 35-23sec P ac

in equalion () to geb ave.t 0.66 x 35.22 + 0, 34 X Δ 23:24 m3/sec emainingCompotoion esults and unit hycoa ase given n table ) Time ΔΑ hx 0.0 0-0 0.0 0.25 | 0.367| O-37 | 3.17 | 3.R | 35.22 23.24 | 1.62 & 5 | О.Az? | 0895 | 895 | 5.78 | 64.2.2| 50.29 | 25.15 to 0S 6 24.80 2u.02 3.u3 2.36 o 3s106 1-25 L- -25 O.331.6 O 55 23