• Journal of Environmental Science International
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• v.10 no.3
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• pp.217-223
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• 2001

Where no records are available at a site, a preliminary estimate may be made from relations between floods and catchment chatacteristics. A number of these chatacteristics were chosen for testing and were measured for those catchments where mean annual flood estimates were available. Although the improvement using extended data in regression of flood estimates on catchment characteristics was small, this may be due to the limitations of the regression model. When an individual short term record is to be extended, more detailed attention can be given; an example is presented of the technique which should be adopted in practice, particularly when a short term record covers a period which is known to be biassed. A method of extending the peaks over a threshold series is presented with a numerical example. The extension of records directly from rainfall by means of a conceptual model is discussed, although the application of such methods is likely to be limited by lack of recording raingauge information. Methods of combining information from various sources are discussed in terms of information from catchment characteristics supplemented by records. but are generally applicable to different sources of information. The application of this technique to estimating the probable maximum flood requires more conservative assumptions about the antecedent condition, storm profile and unit hydrograph. It is suggested that the profile and catchment wetness index at the start of the design duration should be based on the assumption that the estimated maximum rainfall occurs in all durations centered on the storm peak.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.3
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• pp.99-106
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• 1998

This paper presents a procedure for determining the design rainfall depth and the design rainfall intensity at Incheon city area in Korea. In this study the eight probability distributions are considered to estimate the probable rainfall depths for 11 different durations. The Kolmogorov - Smirnov test and the Chi-square test are adopted to test each distribution. The probable rainfall intensity formulas are then determined by i) the least squares (LS) method, ii) the least median squares (LMS) method, iii) the reweighted least squares method based on the LMS (RLS), and iv) the constrained regression (CR) model. The Talbot, the Sherman, the Japanese, and the Unified type are considered to determine the best type for the Incheon station. The root mean squared (RMS) errors are computed to test the formulas derived by four methods. It is found that the Unified type is the most reliable and that all methods presented herein are acceptable for determining the coefficients of rainfall intensity formulas from an engineering point of view.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.3
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• pp.251-259
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• 2000

In this study, the urban runoff models, ILLUDAS model and SWMM, are analyzed the probable peak discharge and discharge using rainfall distribution by Huff's method at Bum-uh chun area in Taegu city. The probability rainfall and intensity is analyzed by Pearson-III type. The rainfall duration, 90 minutes, is determined by the critical duration computed the maximun peak discharge for some rainfall durations. The peak discharge according to Huff's rainfall distribution types compute in order of type 3, type 4, type2, and type 1, so Huff's 3 type is selected as an adequate rainfall distribution in Bum-uh chun basin. ILLUDAS model and SWMM are shown as good models in Bum-uh chun, but SWMM is computed higher peak discharge than ILLUDAS model, so SWMM is shown as the adequate urban runoff model for the design of interior drainage in urban basin.

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.873-884
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• 2008

In this study, rainfall quantile was estimated using scale invariance property of rainfall data with different durations and the applicability of such property was evaluated for the rainfall data of South Korea. For this purpose, maximum annual rainfall at 22 recording sites of Korea Meteorological Administration (KMA) having relatively long records were used to compare rainfall quantiles between at-site frequency analysis and scale invariance property. As the results, the absolute relative errors of rainfall quantiles between two methods show at most 10 % for hourly rainfall data. The estimated quantiles by scale invariance property can be generally applied in the 8 of 14 return periods used in this study. As an example of down-scaling method, rainfall quantiles of $10{\sim}50$ minutes duration were estimated by scale invariance property based on index duration of 1 hour. These results show less than 10 % of absolute relative errors except 10 minutes duration. It is found that scale invariance property can be applied to estimate rainfall quantile for unmeasured rainfall durations.

• Water for future
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• v.28 no.2
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• pp.145-154
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• 1995

The various analyses of the historical rainfall data need to be utilized in a hydraulic engineering project. The probability distributions of the rainfall events according to annual maximum continuous rainfall depths are studied for the hydrologic frequency analysis. The bivariate normal distribution, the bivariate lognormal distribution, and the bivariate gamma distribution are applied to the rainfall events composed of rainfall depths and its durations at Kangnung, Seoul, Incheon, Chupungnyung, Teagu, Jeonju, Kwangju, and Busan. These rainfall events are fitted to the the bivariate normal distribution and the bivariate lognormal distribution, but not fitted to the bivariate gamma distribution. Frequency curves of probability rainfall events are suggested from the probability distribution selected by the goodness-of-fit test.

• Water for future
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• v.14 no.3
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• pp.47-54
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• 1981

The characteristics of point rainfall for three different durations in Seoul Pusan Taegu and Gwangju have been analysed by the probabilistic ainfall method and the M-year maximum rainfall method. The probabilities that the T-year probabilistic rainfall did not occur during the observation period, compared with the values obtained from the observed data. were smaller than the theoretical values. The averages of the probabilities that the M-year maximum-ten-minute rainfall did not occur in the consequent N-years were larger than the theoretical values, the M-year maximumone hour rainfall were smaller than the theoretical ones, and the M-year maximum daily rainfall nearly agreed with them, and while those of Japan were smaller than the theoretical values. It is recommended from the results that the recorded maximum value should be used as a design value rather than the probabilistic rainfall.

• Journal of Korea Water Resources Association
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• v.39 no.6 s.167
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• pp.521-531
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• 2006

The formula was proposed through the examination of probability rainfall intensity formula used in Incheon based upon recent occurrences of heavy rain and extraordinary storms. Random-time maximum annual rainfalls were estimated for durations from ten minutes to twenty-four hours from the data by Korea Meteorological Administration. Eleven types of probability distribution are considered to estimate probable rainfall depths for different storm durations at Incheon city. Three goodness-of-fit tests including Chi-square, Kolmogorov-Smirmov and framer Von Misses were used to analyze the tendency of recent rainfall. Considering maximum rainfall occurred, General Extreme Value(GEV) distribution was chosen as the appropriate probability distribution. Five types of probability rainfall formulas including Talbot type, Sherman type, Japanese type, unified type I and unified type II are considered to determine the best type for rainfall intensity at Incheon. The formula was determined considering the time of concentration of sewer system and river at Incheon city. Unified type I was chosen for its accuracy and was proposed to represent rainfall intensity of Incheon district.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.439-442
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• 2003

This study was conducted to choose optimal distribution and to estimate properly parameters for the derivation of design rainfall in Gamma Family. Design rainfall derived by Gamma Family Distributions were compared by the Relative Mean Errors(RME) and Relative Absolute Errors(RAE) for the consecutive durations of 1, 3, 6, 12, 24, 36, 48 and 72hr and 65 regions all over the regions except Cheju and Wulreung islands in Korea. Consequently, Design rainfall derived by Indirect Method of Moments in the Log-Pearson Type 3 distribution are seemed to be more reasonable than those of other distributions in Gamma Family.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.443-446
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• 2003

This study was conducted to draw design rainfall for the regional design rainfall derived by the optimal distribution and method of frequency analysis. The design rainfalls were calculated by the regional and at-site analysis for Log-Pearson type III and GEV distributions and were compared with Relative efficiency(RE) which is ratio of Relative root-mean-square error(RRMSE) by the regional and at-site analysis for Log-Pearson type III and GEV distributions. Consequently, optimal design rainfalls following the regions and consecutive durations were derived by the regional frequency analysis for GEV distribution and design rainfall maps were drawn by GIS techniques.

• Journal of Korea Water Resources Association
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• v.32 no.4
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• pp.403-415
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• 1999

This study is to derive the rainfall intensity formula based on the representative probability distribution in Korea. The 11 probability distributions which has been widely used in hydrologic frequency analysis are applied to the annual maximum rainfall. The parameters of each probability distribution are estimated by method of moments, maximum likelihood method and method of probability weighted moments. Four tests such as $x^2$-test, Kolmogorv-Smirnov test, difference test and modified difference test are used to determine the goodness of fit of the distributions. The homogeneous tests (Mann-Whitney U test, Kruskal-Wallis one-way analysis of variance of nonparametric test) are applied to find the stations with rainfall homogeneity. The results of homogeneous tests show that there is no representative appropriate distribution for the whole duration in Korea. The whole region could be divided into five zones for 12-durations. The representative probability distribution of each divided zone for 12-durations was determined. The GEV distribution for I,II,V zones and the 3-parameter Weibull distribution for III,IV zones were determined as the representative probability distribution. The rainfall were obtained from representative probability distribution for the selected return periods. Rainfall intensity formula was determined by linearization technique for the rainfall.