Runoff Estimation Based on Stochastic Optimization Method

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Runoff Estimation Based on Stochastic Optimization Method

Original Article, C48
Nikbakht Shahbazi A.
Journal. Civil Eng. Urban. 3(5):323-330. 2013

ABSTRACT:Despite widespread use of Curve Number (CN) as main parameter in SCS equations for estimating runoff of basins with limited data, its capability in appropriate estimation of runoff has always been controversial. In this study, ability of CN method has been studied in estimating runoff through the application of a stochastic optimization method and within the framework of SCS equations. In stochastic method, sensitivity of statistical distributions, number of statistical samples and range of CN changes on accuracy of calculations have been studied through the application of Monte Carlo Simulation. The used stochastic method is based on the rainfall and runoff information. For this purpose, rainfall and runoff modeling are first selected and probable distribution functions, governing these events, are specified. Then, rainfall and runoff modeling are produced in different sample sizes within random modeling. Produced samples of rainfall and runoff are evaluated based on the specific criteria and specific runoff modeling is selected. The selective runoffs and number of experimental curves are used in SCS equations, rainfall modeling is calculated and their probable functions are determined. Based on Kolmogrov-Smirnov Test, optimal curve number (CN_OPT) is set between produced distribution functions and initial probability distribution function governing rainfall events. Also, average and mean curve number (CN_AVG,,CN_MEG) has been studied. Statistics of basins representing Kasilian and Emameh (Northen Iran) has been used with the aim of studying efficiency of stochastic method. In Kasilian Basin, the runoffs, calculated through the use of CN _OPT, enjoyed the minimum error than observational runoffs. This emphasizes desirable capability of CN method in estimating runoff of the basin but stochastic method was unenforceable in Emameh Basin due to the shortage of rainfall and runoff events.
Keywords:Curve Number, Monte Carlo Simulation, SCS Method, Statistical Distribution Function, Stochastic Method.

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