• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.6
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• pp.3-14
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• 2005

Accurate estimation of the spatial distribution of rainfall is critical to the successful modeling of hydrologic processes. The objective of this study is to evaluate the applicability of spatially distributed rainfall data. Spatially distributed rainfall was calculated using Kriging method and Thiessen method. The application of spatially distributed rainfall was appreciated to the runoff response from the watershed. The results showed that for each method the coefficient of determination for observed hydrograph was $0.92\~0.95$ and root mean square error was $9.78\~10.89$ CMS. Ordinary Kriging method showed more exact results than Simple Kriging, Universal Kriging and Thiessen method, based on comparison of observed and simulated hydrograph. The coefncient of determination for the observed peak flow was 0.9991 and runoff volume was 0.9982. The accuracy of rainfall-runoff prediction depends on the extent of spatial rainfall variability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2B
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• pp.137-147
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• 2010

In this study, Chukwooki and modern data were compared using annual maximum rainfall event series. Annual maximum series for specified rainfall duration in modern frequency analysis can not be constructed from Chukwooki data, so the concept of independent rainfall event is introduced to compare Chukwooki and modern data. Annual maximum rainfall event is determined by applying the bivariate exponential distribution and the parameters estimated annually are selected. The results using the annual parameter show that the hydrological meaning of the parameters is related to the variation of annual total rainfall amounts. For the whole independent rainfall events, the total rainfall and the rainfall intensity of Chukwooki data are greater than those of modern data, and rainfall duration of the two periods is similar. However modern annual maximum rainfall events show different characteristics that rainfall duration is much longer, rainfall intensity is similar and the total rainfall is greater than those of Chukwooki period. The increasing trend of rainfall duration and total rainfall of the modern annual rainfall events may be regarded as the one of components of the long-term cycle.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.2 no.1
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• pp.29-36
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• 1998

An instantaneous unit sediment graph (IUSG) model is investigated for prediction of sediment yield from an upland watershed in Northwestern Mississippi. Sediment yields are predicted by convolving source runoff with an IUSG. The IUSG is the distribution of sediment from an instantaneous burst of rainfall producing one unit of runoff. The IUSG, defined as a product of the sediment concentration distribution (SCD) and the instantaneous unit hydrograph (IUH), is known to depend on the characteristics of the effective rainfall. The IUH is derived by the Nash model for each event. The SCD is assumed to be an exponential function for each event and its parameters were correlated with the effective rainfall characteristics. A sediment routing function, based on travel time and sediment particle size, is used to predict the SCD.

• Journal of Environmental Science International
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• v.2 no.1
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• pp.29-36
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• 1993

An instantaneous unit sediment graph (IUSG) model is investigated for prediction of sediment yield from an upland watershed In Northwestern Mississippi. Sediment yields are predicted by convolving source runoff with an IUSG. The IUSG is the distribution of sediment from an instantaneous burst of rainfall producing one unit of runoff. The IUSG, defined as a product of the sediment concentration distribution (SCD) and the instantaneous unit hydrograph (IUH), is known to depend on the characteristics of the effective rainfall. The IUH is derived by the Nash model for each event. The SCD is assumed to be an exponential function for each event and its parameters were correlated with the effective rainfall characteristics. A sediment routing function, based on travel time and sediment particle size, is used to predict the SCD.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.51.2-51.2
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• 2010

A novel approach of Poisson cluster stochastic rainfall generator was validated in its ability to reproduce important rainfall and watershed response characteristics at 104 locations of the United States. The suggested novel approach - The Hybrid Model(THM), as compared to the traditional ones, has an additional function to account for the year-to-year variability of rainfall statistics. The two-sample Kolmogorov-Smirnov test was used to see how well THM and traditional approach of Poisson cluster rainfall model reproduce the distribution of the following hydrologic variables: monthly maximum rainfall depths with 1, 3, 6, 12, and 24 hour duration, monthly maximum flow peaks at the virtual watersheds with Curve Number of 50, 60, 70, 80 and 90; and monthly runoff depths at the same virtual watersheds. In all of the testing variables, THM significantly outperformed the traditional approach. This result indicates that the year-to-year variability of rainfall statistics contains important information about the characteristics of rainfall processes that were not considered by the conventional approach of Poisson cluster rainfall modeling and that further considering it in rainfall simulation will enhance the performance of the rainfall models.

• Proceedings of the Korea Water Resources Association Conference
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• 2001.05a
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• pp.35-44
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• 2001

As one of advanced uses of radar, a physically based rainfall prediction method which uses a conceptual rainfall model assimilated by information from volume scanning radar is shown. As another example of advanced utilization of weather radar, results from analyzing a hierarchical time-scale structure in dependency of rainfall distribution en topography are shown.

• Journal of Korea Water Resources Association
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• v.39 no.9 s.170
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• pp.779-786
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• 2006

In this study, we propose a new method that utilizes rainfall data in and out of a basin, which is greater than 25.4mm for point rainfall or 12.7mm for areal mean rainfall respectively. From our analysis, most frequent quartile for point and areal mean rainfall were found to be the same in general for various rainfall duration intervals. From an evaluation of design rainfall per each rainfall duration distributed in time by the MOCT(Ministry of Construction and Transportation) version of Huff's method and this study, peak rainfall intensity by this study was found to be greater than the one by MOCT, but there were no consistent increase or decrease of this difference with rainfall durations. Using the distributed design rainfall per each duration by MOCT and this study, corresponding flood inflow hydrographs were simulated and compared each other. Contrary to the case of peak rainfall intensity, difference in peak flow by both methods per each rainfall duration started to increase from about 12-hr duration. Especially, the difference in peak flow was significant when critical rainfall duration was considered, and this trend was similar for peak flows of other rainfall durations. Therefore, the method proposed in this study is thought to be the effective procedure for the construction of dimensionless cumulative rainfall curve that is representative of a basin while considering time distribution characteristics for different rainfall durations.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1191-1195
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• 2006

Now days, heavy storm occur to be continue. It is hard to use before frequency based on flood discharge for decision that design water pocket structure. We need to estimation of frequency based on flood discharge on the important basin likely city or basin that damage caused by flood recurrence. In this paper flood discharge calculated by Clark watershed method and SCS synthetic unit hydrograph method about upside during each minute of among time distribution method of rainfall, Huff method choosing Bocheong Stream basin that is representative basin of International Hydrologic Project (IHP) about time distribution of rainfall that exert big effect at flood discharge estimate to research target basin because of and the result is as following. Relation between probability flood discharge that is calculated through frequency analysis about flood discharge data and rainfall - runoff that is calculated through outward flow model was assumed about $48.1{\sim}95.9%$ in the case of $55.8{\sim}104.0%$, SCS synthetic unit hydrograph method in case of Clark watershed method, and Clark watershed method has big value overly in case of than SCS synthetic unit hydrograph method in case of basin that see, but branch of except appeared little more similarly with frequency flood discharge that calculate using survey data. In the case of Critical duration, could know that change is big area of basin is decrescent. When decide time distribution type of rainfall, apply upside during most Huff 1-ST because heavy rain phenomenon of upsides appears by the most things during result 1-ST about observation recording of target area about Huff method to be method to use most in business, but maximum value of peak flood discharge appeared on Huff 3-RD too in the case of upside, SCS synthetic unit hydrograph method during Huff 3-RD incidental of this research and case of Clark watershed method. That is, in the case of Huff method, latitude is decide that it is decision method of reasonable design floods that calculate applying during all $1-ST{\sim}4-TH$.

• Journal of Korea Water Resources Association
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• v.50 no.3
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• pp.211-221
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• 2017

In statistical hydrology, various extreme distributions such as the generalized extreme value (GEV), generalized logistic (GLO) and Gumbel (GUM) models have been widely used to analyze the extreme events. In the case of rainfall events in South Korea, the GEV and Gumbel distributions are known to be appropriate among various extreme distribution models. However, the proper probability distribution model may be different depending on the type of extreme events, rainfall duration, region, and statistical characteristics of extreme events. In this regard, it is necessary to apply a wide range of statistical properties that can be represented by the distribution model because it has two shape parameters. In this study, the statistical applicability of rainfall data is analyzed using the Burr XII distribution and the dimensionless L-moment ratio for 620 stations in South Korea. For this purpose, L-skewness and L-kurtosis of the Burr XII distribution are derived and L-moment ratio diagram is drawn and then the applicability of 620 stations was analyzed. As a result, it is found that the Burr XII distribution for the stations of the Han River basin in which L-skewness is relatively larger than L-kurtosis is appropriate, It is possibility of replacing the distribution of commonly used Gumbel or GEV distributions. Therefore, the Burr XII model can be replaced as an appropriate probability model in this basin.

• Journal of Korea Water Resources Association
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• v.32 no.6
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• pp.627-636
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• 1999

In 60 years when the double $CO_2$concentration is anticipated the average annual rainfall depth is expected to be increased by 5 10% due to global warming. However, in the water resources area the frequency change of meteorological extremes such as droughts and floods attracts more interests than the increase of annual rainfall amount. Even though recent frequent occurrences of this kind of meteorological extremes are assumed as an indirect proof of global warming, the prediction of its overall tendency has not yet been made. Thus, in this research we propose a possible methodology to be used for its prediction. The methodology proposed is based on the frequency distribution of daily rainfall be Todorovie and Woolhiser(1975), and Katz(1977), where the input parameters are modified to consider the change of monthly or annual rainfall depth and, thus, to result in the change of frequency distribution. We adopt two values(10mm, 50mm) as thresholds and investigate the change of occurrence probability due to the change monthly and annual rainfall depth. these changes do not directly indicate the changes of occurrence probability of floods and droughts, but it may still be a very useful information for their prediction. Finally, the changes of occurrence probability were found to be greater when considering the monthly rainfall rather than the annual rainfall, and those in rainy season than those in dry season.