• Water for future
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• v.24 no.2
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• pp.97-108
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• 1991

A number of different curve numbers are estimated, and three of them are the basin or composite curve numbers (CN-II and CN-III) evaluated from hydrologic soil cover complex, the observed curve numbers computed from rainfal1-runoff observations and the basin median curve numbers as a median of the observed curve numbers. Based on the observed runoff, CM-II underestimates the effective rainfall meanwhile CN-III overestimates. Hence, for the improvement in estimating effective rainfall, a modulating curve number may be defined as a value in between CN-II and CN-III. Basin median curve numbers produces the closest result to the observed runoff and therefore it can be adopted as a representative curve number for gaged basin.

• Water for future
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• v.25 no.4
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• pp.87-95
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• 1992

The validity of the estimate of runoff depth and peak runoff by the basin runoff curve numbers(CN-II for AMC-II condition and CN-III for AMC-III condition) obtained from hydrologic soil-cover complexs is investigated by making use of the observed curve numbers(median curve number and optimum curve number) computed from rainfall-runoff records. For gaged basins the median curve numbers are recommended for the estimation of runoff depth and peak runoff. For ungaged basins, found is that for the estimate of runoff depth CN-III is adequate and for the peak runoff CN-II is adequate. Also investigated is the variation of curve numbers during rainfall, which is turned out to improve the estimates of both depth and peak of runoff.

• Korean Journal of Hydrosciences
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• v.4
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• pp.21-32
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• 1993

The estimates of both runoff depth and peak runoff by the basin runoff curve numbers, which are CN-II for antecedent moisture condition- II and CN -III for antecedent moisture condition-III, obtained from hydrological soil-cover complexes of 26 watersheds are investigated by making use of the observed curve numbers, which are median curve number and optimum curve number, computed from 250 rainfall-runoff records. For gaged basins the median curve numbers are recommended for the estimation of both runoff depth and peak runoff. For ungaged basin, found is that for the estimate of runoff depth CN-II is adequate and for peak runoff CN-II is suitable. Also investigated is the variation of the runoff curves during storms. By the variable runoff curve numbers, the prediction of runoff depth and peak runoff can be improved slightly.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.633-645
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• 2003

The techniques of GIS and remote sensing are being applied to hydrology, geomorphology and various field of studies are performed by many researcher, related those techniques. In this paper, curve number change detection is tested according to soil map and land cover in mountain area. Neural networks method is applied for land cover classification and GIS for curve number calculation. The first, sample area are selected and tested land cover classification, NN(84.1％) is superior to MLC(80.9％). So we selected NN with land cover classifier. The second, curve number from the land cover by neural network classifier(57) is compared with that(curve number) from the land cover by manual work(55). Two values are so similar. The third, curve number classified by NN in sample area was applied and tested to whole study area. As results of this study, it is shown that curve number is more exact and efficient by using NN and GIS technique than by (using) manual work.

• Journal of Korea Water Resources Association
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• v.49 no.5
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• pp.373-380
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• 2016

The NRCS-CN (Natural Resources Conservation Service-Curve Number) method has been practically applied for estimating the effective precipitation. However, there are no criteria which reflect the geographic characteristics of Korea having more than 70% of mountainous and rice paddy areas, leading to significant errors in runoff calculation. Thus, it is required to estimate the runoff curve number considered Korea land use classification, however there are practical difficulties to conduct the accurate research and experimentation. In this study, after selecting target areas (urban, agriculture, forest), we performed the runoff analysis to redetermine CN values for the selected basins. To do this, curve numbers for soil type A were estimated using genetic algorithm, and then curve numbers for soil type (B, C, D) were estimated using CN aligner equation. Comparing the initial curve numbers with the estimated curve numbers, it was observed that the slightly differences at Chunwang(0), Choonyang(-1), Janggi(-3). Through the above process, this study proposed new curve numbers to reflect observed rainfall-runoff.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.590-597
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• 2010

NRCS Curve Number (CN) method is widely used for practical purposes in the field by engineers and researchers to calculate direct runoff from total rainfall. However, CN is obtained from antecedent moisture condition and soil characteristics and so it has some problems due to its uncertainty. Therefore this study estimated CN of a watershed using asymptotic CN method which can estimate CN by rainfall and runoff data and compared the result with representative CN given by WAMIS. And we performed runoff simulation for rainy season of Bocheong stream by CN regression equation. From the result, we showed that it could be more reasonable to simulate direct runoff using watershed CN regression equation than WAMIS CN. Furthermore, we knew that the equation is more sensitive to small rainfall event.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.6
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• pp.11-16
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• 2009

This study is to suggest the SWAT model as inputs for the estimation of CN (Curve number) if we do not have hourly rainfall and runoff data in the ungaged watershed. The daily CNs were estimated by using SWAT model for Chungju dam watershed and the CNs by hourly rainfall and runoff data in the same period with daily CN estimation were also estimated. Then the daily and hourly CNs were compared each other. The CNs by SWAT model were larger than the actual CNs. 7.4% larger in AMC-I, 1.2% in AMC-II, and 6.3% in AMC-III respectively. If we consider various uncertainties in the estimation of CN, the error of 6.8% could be acceptable for the application in the field.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.775-780
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• 2008

유출곡선지수(SCS-CN)를 사용하는 유역수문모형의 정확도를 향상시키기 위해서는 토지이용별 유출곡선지수가 잘 정의되어야한다. 하지만 논의 경우에는 유출곡선지수가 잘 정의되어 있지않다. 현재까지 연구된 논 CN number로는 경기지역의 조건을 반영한다. 본 연구에서는 영산강 수계와 섬진강 수계에 대한 논의 CN값을 추정하기위해 수문모니터링을 실시하였다. 시험지구는 영산강 수계 내에 위치한 전라남도 함평군 엄다면 화양리 학야지구와 섬진강 수계 내에 위치한 전라북도 순창군 적성면 고원리 적성지구로 2004년부터 2007년 영농기(5월$\sim$9월)동안 모니터링을 실시하였다. 두 시험지구에서 각각 강우량과 유출량을 조사하여 강우-유출 관계식을 유도하여 CN값을 산정하였다. 그 결과 CN-I, CN-II, CN-III 값은 학야지구에서 각각 65, 85, 94로 나타났고, 적성지구에서 각각 69, 89, 97로 나타났다. 이는 기존의 연구와 비교하여 CN-II값이 더 높은 것으로 나타났다.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1231-1244
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• 2008

The objective of this study is to present a methodology for estimating runoff curve number(CN) using SWAT model which is capable of reflecting watershed heterogeneity such as climate condition, land use, soil type. The proposed CN estimation method is based on the asymptotic CN method and particularly, it uses surface flow data simulated by SWAT. This method has advantages to estimate spatial CN values according to subbasin division and to reflect watershed characteristics because the calibration process has been made by matching the measured and simulated streamflows. Furthermore, the method is not sensitive to rainfall-runoff data since CN estimation is on a daily basis. The SWAT based CN estimation method is applied to Chungju dam watershed. The regression equation of the estimated CN that exponentially decays with the increase of rainfall is presented.

• Journal of Korea Water Resources Association
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• v.30 no.5
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• pp.423-430
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• 1997

It is one of the most important factors to determine the effective rainfall for estimation of flood hydrograph in design schedule. SCS curve number (CN) method has been frequently used to estimate the effective rainfall of synthesized design flood hydrograph for hydraulic structures. But, it should be cautious to apply SCS-CN originally developed in U.S.A to watersheds in Korea, because characteristics of watersheds in Korea and cropping patterns especially like a paddy land cultivation are quite different from those in USA. New CN method has been introduced. Maximum storage capacity which was herein defined as Umax can be calibrated from the streamflow data and converted to new CN-I of direst condition of soil moisture in the given watershed. Effective rainfall for design flood hydrograph can be estimated by the curve number developed in the watersheds in Korea.