• Title/Summary/Keyword: Probability rainfall amount

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Rainfall Variations of Temporal Characteristics of Korea Using Rainfall Indicators (강수지표를 이용한 우리나라 강수량의 시간적인 특성 변화)

  • Hong, Seong-Hyun;Kim, Young-Gyu;Lee, Won-Hyun;Chung, Eun-Sung
    • Journal of Korea Water Resources Association
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    • v.45 no.4
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    • pp.393-407
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    • 2012
  • This study suggests the results of temporal and spatial variations for rainfall data in the Korean Peninsula. We got the index of the rainfall amount, frequency and extreme indices from 65 weather stations. The results could be easily understood by drawing the graph, and the Mann-Kendall trend analysis was also used to determine the tendency (up & downward/no trend) of rainfall and temperature where the trend could not be clear. Moreover, by using the FARD, frequency probability rainfalls could be calculated for 100 and 200 years and then compared each other value through the moment method, maximum likelihood method and probability weighted moments. The Average Rainfall Index (ARI) which is meant comprehensive rainfalls risk for the flood could be obtained from calculating an arithmetic mean of the RI for Amount (RIA), RI for Extreme (RIE), and RI for Frequency (RIF) and as well as the characteristics of rainfalls have been mainly classified into Amount, Extremes, and Frequency. As a result, these each Average Rainfall Indices could be increased respectively into 22.3%, 26.2%, and 5.1% for a recent decade. Since this study showed the recent climate change trend in detail, it will be useful data for the research of climate change adaptation.

Bayesian Nonstationary Probability Rainfall Estimation using the Grid Method (Grid Method 기법을 이용한 베이지안 비정상성 확률강수량 산정)

  • Kwak, Dohyun;Kim, Gwangseob
    • Journal of Korea Water Resources Association
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    • v.48 no.1
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    • pp.37-44
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    • 2015
  • A Bayesian nonstationary probability rainfall estimation model using the Grid method is developed. A hierarchical Bayesian framework is consisted with prior and hyper-prior distributions associated with parameters of the Gumbel distribution which is selected for rainfall extreme data. In this study, the Grid method is adopted instead of the Matropolis Hastings algorithm for random number generation since it has advantage that it can provide a thorough sampling of parameter space. This method is good for situations where the best-fit parameter values are not easily inferred a priori, and where there is a high probability of false minima. The developed model was applied to estimated target year probability rainfall using hourly rainfall data of Seoul station from 1973 to 2012. Results demonstrated that the target year estimate using nonstationary assumption is about 5~8% larger than the estimate using stationary assumption.

Probability of performance failure of storm sewer according to accumulation of debris (토사 적체에 따른 우수관의 성능불능확률)

  • Kwon, Hyuk-Jae
    • Journal of Korean Society of Water and Wastewater
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    • v.24 no.5
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    • pp.509-517
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    • 2010
  • Statistical distribution of annual maximum rainfall intensity of 18 cities in Korea was analyzed and applied to the reliability model which can calculate the probability of performance failure of storm sewer. After the analysis, it was found that distribution of annual maximum rainfall intensity of 18 cities in Korea is well matched with Gumbel distribution. Rational equation was used to estimate the load and Manning's equation was used to estimate the capacity in reliability function to calculate the probability of performance failure of storm sewer. Reliability analysis was performed by developed model applying to the real storm sewer. It was found that probability of performance failure is abruptly increased if the diameter is smaller than certain size. Therefore, cleaning the inside of storm sewer to maintain the original diameter can be one of the best ways to reduce the probability of performance failure. In the present study, probability of performance failure according to accumulation of debris in storm sewer was calculated. It was found that increasing the amount of debris seriously decrease the capacity of storm sewer and significantly increase the probability of performance failure.

Radar Rainfall Estimation Using Window Probability Matching Method : 1. Establishment of Ze-R Relationship for Kwanak Mt, DWSR-88C at Summer, 1998 (WPMM 방법을 이용한 레이더 강수량 추정 : 1. 1998년 여름철 관악산 DWSR-88C를 위한 Ze-R 관계식 산출)

  • Kim, Hyo-Gyeong;Lee, Dong-In;Yu, Cheol-Hwan;Gwon, Won-Tae
    • Journal of Korea Water Resources Association
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    • v.35 no.1
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    • pp.25-36
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    • 2002
  • Window Probability Matching Method(WPMM) is achieved by matching identical probability density of rain intensities and radar reflectivities taken only from small window centered about the gage. The equation of $Z_{e}-R$ relationship is obtained and compared with data between a DWSR-88C radar and high density rain gage networks within 150km from radar site in summer season, 1998. The probability density of radar effective reflectivity is distributed with high frequency near 15dBZ. The frequency distribution of rain intensities shows that rain intensity is lower than 10mm/hr in most part of radar coverage area. As the result of $Z_{e}-R$ relationship using WPMM, curved line has shown to the log scale spatially and it can be explained more flexible than any straight-line power laws at the transformation to the rainfall amount from $Z_e$ value. During 3 months, total radar cumulative rainfall amount estimated by $Z=200R^{1.6}$ and WPMM relationships are 44 and 80 percentages of total raingage amount, respectively. Therefore, $Z_{e}-R$ relationships by WPMM may be widely needed a statistical method for the computation of accumulated precipitation.

Revised AMC for the Application of SCS Method (SCS 유효우량 산정방법 적용을 위한 선행토양함수조건의 재설정(장평유역을 중심으로))

  • Park, Cheong-Hoon;Yoo, Chul-Sang;Kim, Joong-Hoon
    • Proceedings of the Korea Water Resources Association Conference
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    • 2005.05b
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    • pp.578-582
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    • 2005
  • In this study, the conceptual foundation and development process of the Antecedent soil Moisture Condition(AMC) in SCS runoff curve number method are reviewed. Although the runoff volume is very sensitive with AMC condition, the AMC class limits developed in SCS(1972) are used in rainfall-runoff analysis without careful consideration. Tn this study, following the SCS curve number development process, rainfall-runoff characteristics of the Jang-Pyung subbasin subject to the Pyung-Chang River basin are analyzed to evaluate the reasonability of the AMC class limits at present. The New AMC class limits are proposed by the sensitive analysis of the antecedent rainfall - curve number value. As a result, the classification value of AMC-I with II is 22mm of antecedent 5-day rainfall amount, and the classification of AMC-II with III is 117mm in growing season. When the New AMC class limits are applied to Jang-Pyung subbasin, AMC probability distribution shows that the AMC-II has increased remarkably even though the AMC-I has a little higher value. But the AMC-III has the smallest one. According to the conceptual basis of the curve number method, the AMC probability distribution, the New AMC class limits adopted, gives reasonable results.

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On the Change of Flood and Drought Occurrence Frequency due to Global Warming : 2. Estimation of the Change in Daily Rainfall Depth Distribution due to Global Warming (지구온난화에 따른 홍수 및 가뭄 발생빈도의 변화와 관련하여 : 2. 지구 온난화에 따른 일강수량 분포의 변화 추정)

  • Yun, Yong-Nam;Yu, Cheol-Sang;Lee, Jae-Su;An, Jae-Hyeon
    • 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.

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Reestimation of Hydrologic Design Data in Donghwa Area (동화지구 절계 수문량 재추정)

  • Kwon, Soon-Kuk;Lee, Jae-Hyoung;Jung, Jae-Sung;Chon, Il-Kweon;Kim, Min-Hwan;Lee, Kyung-Do
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.6
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    • pp.3-10
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    • 2004
  • The fundamental study of hydrologic redesign of Donghwa area located in a sccond tributary of Seomjin river was performed. The amounts of hydrologic design were estimated using the available cumulated hydrology data provided by Korea Agricultural and Rural Infrastructure Corporation (KARICO). The management status of The water resources in Donghwa area was also widely surveyed. The probability rainfalls, probable maximum precipitation (PMP) and probability floods were estimated and subsequently their changes analyzed. The amount of 200 year frequency rainfall with l day duration was 351.1 mm, 2.5 % increased from the original design value, and The PMP was 780.2 mm. The concentration time was reestimated as 2.5 hours from existing 2.4 hours. Soil Conservation Service(SCS) method was used to estimate effective rainfall- The runoff curve number was changed from 90 to 78, therefore the maximum potential retention was 71.6 mm, 154 % increased from the original value. The Hood estimates using SCS unit hydrograph showed 8 % increase from original value 623 $m^3$/s to 674 $m^3$/s and The probable maximum Hood was 1,637 $m^3$/s. Although the Row rate at the dam site was increased, the Hood risk at the downstream river was decreased by the Hood control of the Donghwa dam.

A Study on the Flooding Risk Assessment of Energy Storage Facilities According to Climate Change (기후변화에 따른 에너지 저장시설 침수 위험성 평가에 관한 연구)

  • Ryu, Seong-Reul
    • Journal of the Society of Disaster Information
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    • v.18 no.1
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    • pp.10-18
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    • 2022
  • Purpose: For smooth performance of flood analysis due to heavy rain disasters at energy storage facilities in the Incheon area, field surveys, observational surveys, and pre-established reports and drawings were analyzed. Through the field survey, the characteristics of pipelines and rivers that have not been identified so far were investigated, and based on this, the input data of the SWMM model selected for inundation analysis was constructed. Method: In order to determine the critical duration through the probability flood analysis according to the calculation of the probability rainfall intensity by recurrence period and duration, it is necessary to calculate the probability rainfall intensity for an arbitrary duration by frequency, so the research results of the Ministry of Land, Transport and Maritime Affairs were utilized. Result: Based on this, the probability of rainfall by frequency and duration was extracted, the critical duration was determined through flood analysis, and the rainfall amount suggested in the disaster prevention performance target was applied to enable site safety review. Conclusion: The critical duration of the base was found to be a relatively short duration of 30 minutes due to the very gentle slope of the watershed. In general, if the critical duration is less than 30 minutes, even if flooding occurs, the scale of inundation is not large.

Estimation of Markov Chain and Gamma Distribution Parameters for Generation of Daily Precipitation Data from Monthly Data (월 자료로부터 일 강수자료 생성을 위한 Markov 연쇄 및 감마분포 모수 추정)

  • Moon, Kyung Hwan;Song, Eun Young;Son, In Chang;Wi, Seung Hwan;Oh, Soonja;Hyun, Hae Nam
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.19 no.1
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    • pp.27-35
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    • 2017
  • This research was to elucidate the generation method of daily precipitation data from monthly data. We applied a combined method of Markov chain and gamma distribution function using 4 specific parameters of ${\alpha}$, ${\beta}$, p(W/W) and p(W/D) for generation of daily rainfall data using daily precipitation data for the past 30 years which were collected from the country's 23 meteorological offices. Four parameters, applied to use for the combination method, were calculated by maximum likelihood method in location of 23 sites. There are high correlations of 0.99, 0.98 and 0.98 in rainfall days, rainfall probability and mean amount of daily rainfall between measured and simulated data in case of those parameters. In case of using parameters estimated from monthly precipitation, correlation coefficients in rainfall days, rainfall probability and mean amount of daily rainfall are 0.84, 0.83 and 0.96, respectively. We concluded that a combination method with parameter estimation from monthly precipitation data can be applied, in practical purpose such as assessment of climate change in agriculture and water resources, to get daily precipitation data in Korea.

Appropriateness analysis of design rainfall factors using the rainfall data of an inundated flood events (침수 홍수사상의 강우자료를 활용한 설계강우 요소의 적정성 분석)

  • Yu, Byeong-Wook;Kim, Seon-Ho;Bae, Deg-Hyo
    • Journal of Korea Water Resources Association
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    • v.53 no.4
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    • pp.237-247
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    • 2020
  • The purpose of this study is to analyze whether design rainfall and hyetograph, which are the main elements of design rainfall, can properly reflect the those of observed rainfalls through inundated rainfall events. The target areas were selected at seven large cities with high damages regarding to the flooding. Comparative analysis between probability and observed rainfall shows that 57% of the cases, in which rainfall amount through the IDF curve is estimated lower than the observed rainfall, do not properly reflect the observed rainfalls. In particular, this trend is exacerbated by the cases in low return period and the rain type of typhoon or frontal rain. The comparative results of rainfall intensity formula showed that the Talbot and Japanese formula were stable in the short- and long-term return periods, respectively. The comparison of hyetograph results also showed that the Mononobe method properly reflects the maximum rainfall intensity and the Huff method properly reflects the shape of rainfall pattern.