• Title/Summary/Keyword: Rainfall depth

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Inundation Analysis of Agricultural Basin Considering Agricultural Drainage Hydrological Plan and Critical Rainfall Duration (농지배수 수문설계 기준과 임계지속기간을 고려한 농업 소유역 침수분석)

  • Kim, Kwihoon;Jun, Sang-Min;Kang, Moon Seong;Choi, Jin-Yong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.65 no.4
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    • pp.25-32
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    • 2023
  • KDS (Korean Design Standard) for agricultural drainage is a planning standard that helps determine the appropriate capacity and type of drainage facilities. The objective of this study was to analyze the inundation of the agricultural basin considering the current design standard and the critical rainfall duration. This study used the rainfall durations of 1-48 hour, and the time distribution method with the Chicago and the modified Huff model. For the runoff model, the NRCS (Natural Resources Conservation Service) unit hydrograph method was applied, and the inundation depth and duration were analyzed using area-elevation data. From the inundation analysis using the modified Huff method with different rainfall durations, 4 hours showed the largest peak discharge, and 11 hours showed the largest inundation depth. From the comparison analysis with the current method (Chicago method with a duration of 48 hours) and the modified Huff method applying critical rainfall duration, the current method showed less peak discharge and lower inundation depth compared to the modified Huff method. From the simulation of changing values of drainage rate, the duration of 11 hours showed larger inundation depth and duration compared to the duration of 4 hours. Accordingly, the modified Huff method with the critical rainfall duration would likely be a safer design than the current method. Also, a process of choosing a design hydrograph considering the inundation depth and duration is needed to apply the critical rainfall duration. This study is expected to be helpful for the theoretical basis of the agricultural drainage design standards.

Estimation of Probable Maximum Precipitation in Thailand Using Geographic Information System

  • Kingpaiboon, Sununtha;Netwong, Titiya
    • Proceedings of the KSRS Conference
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    • 2003.11a
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    • pp.804-806
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    • 2003
  • Probable Maximum Precipitation (PMP) is essential in the design of hydraulic structures such as dams, weirs and flood control structures. Up to the present, PMP has been derived from any proper single storm which can have a large error. PMP values should be evaluated from many historic heavy storm events from all over the country. Since this can be done at the spots of storm occurring and the calculated PMP from all spots in the country can be correlated. The objectives of this study are therefore to evaluate PMP from historic heavy storm data from 1972 to 2000 by using meteorological method, then to correlate and to present the results using GIS. The maximized rainfall depths can be calculate from depth of heavy rainfall and dew point temperature, and then can be analyzed for each rainfall duration to obtain spatial rainfall distribution by using GIS. The depth-area-duration relationship of maximized rainfall can be obtained and this helps to develop enveloped curves . The results from this study are a set of contour maps of PMP for each rainfall duration for all over the country and the depth-area-duration relationships for the area of 100 to 50,000 km.$^{2}$ at duration of 1, 2 and 3 days.

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Saturation Depth and Slope Stability considering Unsteady Rainfall in Natural Slope (비정상강우를 적용한 자연사면에서의 포화깊이 산정 및 사면안정성 평가)

  • Kim, Sang-Hoon;Kim, Seong-Pil;Son, Young-Hwan;Heo, Joon;Chang, Pyoung-Wuck
    • Journal of The Korean Society of Agricultural Engineers
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    • v.49 no.1
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    • pp.57-65
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    • 2007
  • In Korea, most landslides occurr during the rainy season and have shallow failure planes parallel to the slope. For these types of rainfall-induced failures, the most important factor triggering slope unstability is decrease in the matric suction of unsaturated soils with increasing saturation depth by rainfall infiltration. For this reason, estimation of cumulative infiltration has a significance. In this study, infiltration rate and cumulative infiltration are estimated by using both Mein & Larson model based on Green-Ampt infiltration model and using modified Mein & Larson model to which unsteady rainfall is applied. According to the results, the modified model is more reasonable than Mein & Larson method itself in estimation of infiltration rate and saturation depth because of considering real pending condition.

A Study on Depth-Area-Duration Models of Heavy Rainfall, 1999 in the Im-Jin River Basin (1999년 임진강 유역의 집중호우에 대한 DAD모형의 연구)

  • 박상우;김백조;장석환
    • Journal of Environmental Science International
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    • v.11 no.7
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    • pp.621-626
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    • 2002
  • Depth-area-duration(DAD) relations are important to hydrological plans and designs for the water resources as well as the flood defence. And these relations have been still in analysis and use today because they can be applied to readily available data. In this paper, rational and consistent DAD models were developed using the multiple regression analysis and basic relationships of area ratio-runoff volume about heavy rainfall occurring in the Im-Jin river basin, 1999. In addition, revised DAD models and curves that can convert a maximum point rainfall to mean area rainfall were developed and evaluated. As results, these models seem to have predictive value in order to plan and design hydrological structures of flood defence in the Im-Jin river basin.

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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A Study on Flash Flood Warning Trigger Rainfall in Mountainous Area (산악지역 돌발홍수 기준우량 결정에 관한 연구)

  • Jun, Kye-Won;Oh, Chae-Yeon
    • Journal of the Korean Society of Safety
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    • v.24 no.1
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    • pp.89-94
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    • 2009
  • The purpose of this study is to estimate the critical flood discharge and flash flood trigger rainfall for alarm system providing for a flash flood in mountainous area. The flash flood need non-linear approaching method, because rainfall-runoff is nonlinear and it is difficult to explain the existing linear rainfall-runoff. Hydrological characteristics would be utilized to apply such as hydrologic modelling or basin management. This study was effectively estimated a topographic characteristic factor of basin using the GIS. Especially, decided stream order using GIS at stream order decision that is important for input variable of GCIUH. A flash floods defined as a flood which follows shortly after a heavy or excessive rainfall event, with a few hours. In this study, we gave a definition that a critical flood for alarm is the flood when valley depth judging dangerous depth is over 0.5m depth from the bottom of channel. Result that calculate threshold discharge to use GCIUH, at the Mureung valley basin, flash flood trigger rainfall was 16.34mm in the first 20minutes when the threshold discharge was $14.54m^3/sec$.

Maximum Areal Rainfall of Korea in the 20th Century (20세기 우리나라 관측최대강수량의 특성)

  • Kim, Nam-Won;Won, Yoo-Seung
    • Journal of Korea Water Resources Association
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    • v.37 no.5
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    • pp.425-435
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    • 2004
  • Mainly, observed maximum rainfall has been evaluated by point rainfall, but actually it should be considered by means of average areal rainfall. Average areal rainfall is an estimated value computed through DAD(rainfall Depth-Area-Duration) analysis. By using this value, an average and maximum areal rainfall according to area-duration relationship could be computed. In this study, we assume that the whole Korea region is hydrologically homogeneous, and then analyze using the storm-centered DAD(moving-area DAD) method for the past century data. From this analysis, we evaluate the yearly variation of observed maximum areal rainfall through area-duration relationship. And we also construct an IDF(rainfall Intensity-Duration-Frequency) curve by using the annual time series data which is composed of maximum areal rainfall. The characteristics of IDF and observed maximum areal rainfall is also evaluated.

우리나라 주요지점에 있어서의 강우해석에 관한 수문통계학적 연구

  • 이원환
    • Water for future
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    • v.5 no.2
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    • pp.30-43
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    • 1972
  • The paper describes on the hydrologic analysis of point rainfall data of the three major areas, such as in Seoul, Pusan and Taegu. Scheme of the paper is analyzed five research cases. Contents of the analysis are carried out five kinds of transformed variables for determination of rainfall distribution types and two kinds of reliability tests on unusual(extraordinary) values each rainfall durations:short durations, long durations, long durations, monthly and yearly. Rainfall depth probability had been computed methods of hydrologic amounts analysis namely logarithmic transformations or Gumbel-Chow method and so on, but in this paper it is calculated log xi, n-square root transformations by using normal distribution function and normalization of rainfall distributions is examined graphical tests and $X^2-test$(chi-square test). Furthermore, rainfall depth probability is calculated taking into account the safty factors of project life of hydraulic structures. We think it is advanced contents that considering priceless experiences, the life of structures, conditions and more problems of planning engineers and designers, proposed rainfall amounts(proposed values) are presented charts or figures.

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Bivariate Frequency Analysis of Rainfall using Copula Model (Copula 모형을 이용한 이변량 강우빈도해석)

  • Joo, Kyung-Won;Shin, Ju-Young;Heo, Jun-Haeng
    • Journal of Korea Water Resources Association
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    • v.45 no.8
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    • pp.827-837
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    • 2012
  • The estimation of the rainfall quantile is of great importance in designing hydrologic structures. Conventionally, the rainfall quantile is estimated by univariate frequency analysis with an appropriate probability distribution. There is a limitation in which duration of rainfall is restrictive. To overcome this limitation, bivariate frequency analysis by using 3 copula models is performed in this study. Annual maximum rainfall events in 5 stations are used for frequency analysis and rainfall depth and duration are used as random variables. Gumbel (GUM), generalized logistic (GLO) distributions are applied for rainfall depth and generalized extreme value (GEV), GUM, GLO distributions are applied for rainfall duration. Copula models used in this study are Frank, Joe, and Gumbel-Hougaard models. Maximum pseudo-likelihood estimation method is used to estimate the parameter of copula, and the method of probability weighted moments is used to estimate the parameters of marginal distributions. Rainfall quantile from this procedure is compared with various marginal distributions and copula models. As a result, in change of marginal distribution, distribution of duration does not significantly affect on rainfall quantile. There are slight differences depending on the distribution of rainfall depth. In the case which the marginal distribution of rainfall depth is GUM, there is more significantly increasing along the return period than GLO. Comparing with rainfall quantiles from each copula model, Joe and Gumbel-Hougaard models show similar trend while Frank model shows rapidly increasing trend with increment of return period.

Development Method of Early Warning Systems for Rainfall Induced Landslides (강우에 의한 돌발 산사태 예·경보 시스템 구축 방안)

  • Kim, Seong-Pil;Bong, Tae-Ho;Bae, Seung-Jong;Park, Jae-Sung
    • Journal of The Korean Society of Agricultural Engineers
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    • v.57 no.4
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    • pp.135-141
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    • 2015
  • The objective of this study is to develop an early warning system for rainfall induced landslides. For this study, we suggested an analysis process using rainfall forecast data. 1) For a selected slope, safety factor with saturated depth was analyzed and safety factor threshold was established (warning FS threshold=1.3, alarm FS threshold=1.1). 2) If rainfall started, saturated depth and safety factor was calculated with rainfall forecast data, 3) And every hour after safety factor is compared with threshold, then warning or alarm can issued. In the future, we plan to make a early warning system combined with the in-situ inclinometer sensors.