Question

8.7.10 Consider a drainage basin having 60 percent soil group A and 40 percent soil group B. Five years ago, the land use pattern in the basin was 1/2 wooded area with poor cover and 1/2 cultivated land with good conservation treatment. Now, the land use has been changed to 1/3 wooded area, 1/3 cultivated land, and 1/3 commercial and business area. Estimate the increased runoff volume during the dormant season due to the land use change over the past 5-year period for a storm of 350 mm in total depth. This storm depth corresponds to a duration of 6-hr and 100-year return period. The total 5-day antecedent rainfall amount is 30 mm. Note: 1 inch 25.4 mm

Answer 1

uen Denote Number o land use Claries nice The area indi a land use aulLand ce], and Cue oumber o pauti Show The Land ure, Soil group, and CorreRpondi Cuue Numben value oTe Catchment as in Table() So roup Go A and YL.I^ Cultivated GO./.A and Numbex Wooded auea 4S 40-/ B Land 401. 8 Cu Number, CN(H):0.5(45)十0.5(83) Compute The Cusve Number CCTIT) CorreRpon thon t The Onte CeduntheMoisture Condit

using The _feơ mula 23 CNC 0+0-13 CN 64-per CNCT) Substitute 2O The Welahed Cesue Numbes Ta Firdinq e Maximum Pet ential velasrion, I, o o O CNCL) go S-2.s ure Pe me Avg.raintal , EHece rartel Volume-P e, Maximum, Potential e1entrơn 22,ISO.25 35

relation Land uSe Change ajtes 5 yea. The Catchment- as T Table() Sofl EToup Number 4S Coues y Cultivated Land Bosiness asea CN CI) 333 (45)+0 33 333(9) toTeOante Cedent Compute The N(L) Covse sp wer Moisture Cortom CN 23 CNCL) 23 73 ニ86 The Maximum potential Retestio

inding Total e ecrive rainta" volume Pe =(350-0. 2x !. 628 22,272.1g 351 20 350+0.gx1 2293 Rune ㆅ due·to he Retarion 가e Sincealed n Land Pe343- 347 .. The ncsased ru