• Title/Summary/Keyword: Peak rainfall

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A Sensitivity of Simulated Runoff Characteristics on the Different Spatial Resolutions of Precipitation Data (강우자료의 공간해상도에 따른 모의 유출특성 민감도 고찰)

  • Lee, Dogil;Hwang, Syewoon
    • Journal of The Korean Society of Agricultural Engineers
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    • v.65 no.6
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    • pp.37-49
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    • 2023
  • Rainfall data is one of the most important data in hydrologic modeling. In this study, the impacts of spatial resolution of precipitation data on hydrological responses were assessed using SWAT in the Santa Fe River Basin, Florida. High correlations were found between the FAWN and NLDAS rainfall data, which are observed weather data and simulated weather data based on observed data, respectively. FAWN-based scenarios had higher maximum rainfall and more rainfall days and events compared to NLDAS-based scenarios. Downstream areas showed lower correlations between rainfall and peak discharge than upstream areas due to the characteristics of study site. All scenarios did not show significant differences in base flow, and showed less than 5% of differences in high flows among NLDAS-based scenarios. The impact of resolution will appear differently depending on the characteristics of the watershed and topography and the applied model, and thus, is a process that must be considered in advance in runoff simulation research. The study suggests that applying the research method to watersheds in Korea may yield more pronounced results, and highlights the importance of considering data resolution in hydrologic modeling.

A Study on the Modification Value for Estimation of Traveling Speed During Rainfall in Interrupted Traffic Flow (단속교통류에서 강우시 평균통행속도 산정을 위한 보정계수에 관한 연구)

  • Mo, Moo Ki;Lee, Seung Joo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.5
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    • pp.837-844
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    • 2017
  • Generally, V/C ratio in uninterrupted traffic flow and average travel speed in interrupted traffic flow are utilized as measure of effect for assessing operational situation of roads. The set of road conditions and traffic conditions are considered to be major variables for assessing operational situation in the traffic flow. However, weather conditions such as rainfall also affect the operational situation of roads. The studies reflected by the rainy situation are conducted in the uninterrupted flow, but the related studies are insufficient in the interrupted flow. In this study, the modification factors during rainfall in the interrupted flow were suggested, and the factors could be used when calculating the average travel speed during rainfall in the interrupted flow. By utilizing the data that were investigated in the same road and traffic conditions and the different weather conditions (rainy day or clear day), the modification factors were founded on regression analysis of the travel speed during rainfall as a dependent variable. Modification factors was suggested in dividing peak time, non-peak time, and whole period. Based on this study, the modification factors can be used to complementing the average travel speed model for assessing the operational situation of urban streets during rainfall.

Application of Very Short-Term Rainfall Forecasting to Urban Water Simulation using TREC Method (TREC기법을 이용한 초단기 레이더 강우예측의 도시유출 모의 적용)

  • Kim, Jong Pil;Yoon, Sun Kwon;Kim, Gwangseob;Moon, Young Il
    • Journal of Korea Water Resources Association
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    • v.48 no.5
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    • pp.409-423
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    • 2015
  • In this study the very short-term rainfall forecasting and storm water forecasting using the weather radar data were implemented in an urban stream basin. As forecasting time increasing, the very short-term rainfall forecasting results show that the correlation coefficient was decreased and the root mean square error was increased and then the forecasting model accuracy was decreased. However, as a result of the correlation coefficient up to 60-minute forecasting time is maintained 0.5 or higher was obtained. As a result of storm water forecasting in an urban area, the reduction in peak flow and outflow volume with increasing forecasting time occurs, the peak time was analyzed that relatively matched. In the application of storm water forecasting by radar rainfall forecast, the errors has occurred that we determined some of the external factors. In the future, we believed to be necessary to perform that the continuous algorithm improvement such as simulation of rapid generation and disappearance phenomenon by precipitation echo, the improvement of extreme rainfall forecasting in urban areas, and the rainfall-runoff model parameter optimizations. The results of this study, not only urban stream basin, but also we obtained the observed data, and expand the real-time flood alarm system over the ungaged basins. In addition, it is possible to take advantage of development of as multi-sensor based very short-term rainfall forecasting technology.

The Characteristics of Heavy Rainfall over the Korean Peninsular - Case Studies of Heavy Rainfall Events during the On- and Off- Changma Season- (장마기와 장마 후의 한반도 집중호우 특성 사례분석)

  • Chung, Hyo-Sang;Chung, Yun-Ang;Kim, Chang-Mo;Ryu, Chan-Su
    • Journal of Environmental Science International
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    • v.21 no.12
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    • pp.1511-1521
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    • 2012
  • An attempt is made to analyse characteristic features of heavy rainfalls which occur at the metropolitan area of the Korean peninsular the on- and off- Changma season. For this, two representative heavy rainfall episodes are selected; one is the on-Changma season wherein a torrential rain episode happened at Goyang city on 12 July 2006, and the other is the off-Changma season, a heavy rainfall event in Seoul on 21 September 2006. Both recorded considerable amounts of precipitation, over 250mm in a half-day, which greatly exceeded the amount expected by numerical prediction models at those times, and caused great damage to property and life in the affected area. Similarities in the characteristics of both episodes were shown by; the location of upper-level jet streak and divergence fields of the upper wind over heavy rainfall areas, significantly high equivalent potential temperatures in the low atmospheric layer due to the entrainment of hot and humid air by the low-level jet, and the existence of very dry air and cold air pool in the middle layer of the atmosphere at the peak time of the rainfall events. Among them, differences in dynamic features of the low-level jet and the position of rainfall area along the low-level jet are remarkable.

Estimation of Trigger Rainfall for Threshold Runoff in Mountain River Watershed (산지하천 유역의 한계유출량 분석을 위한 기준우량 산정)

  • Kim, Dong Phil;Kim, Joo Hun;Lee, Dong Ryul
    • Journal of Wetlands Research
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    • v.14 no.4
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    • pp.571-580
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    • 2012
  • This study is on the purpose of leading Geomorphoclimatic Instantaneous Unit Hydrograph(GcIUH) by using GIS Techniques, and estimating trigger rainfall for predicting flash flood in Seolmacheon catchment, mountain river watershed. This study leads GcIUH by using GIS techniques, calculates NRCS-CN values for effective rainfall rate, and analyzes 2011 main rainfall events using estimated GcIUH. According to the results, the case of Memorial bridge does not exceed the amount of threshold runoff, however, the case of Sabang bridge shows that simulated peak flow, approximately $149.4m^3/s$, exceeds the threshold runoff. To estimate trigger rainfall, this study determines the depth of 50 year-frequency designed flood amount as a threshold water depth, and estimates trigger rainfall of flash flood in consideration of duration. Hereafter, this study will analyze various flood events, estimate the appropriateness of trigger rainfall as well as threshold runoff through this analysis, and develop prototype of Flash Flood Prediction System which is considered the characteristics of mountain river watershed on the basis of this estimation.

Assessment of Flood Probability Based on Temporal Distribution of Forecasted-Rainfall in Cheongmicheon Watershed (예보강우의 시간분포에 따른 청미천 유역의 홍수 확률 평가)

  • Lee, Hyunji;Jun, Sang Min;Hwang, Soon Ho;Choi, Soon-Kun;Park, Jihoon;Kang, Moon Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.62 no.1
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    • pp.17-27
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    • 2020
  • The objective of this study was to assess the flood probability based on temporal distribution of forecasted-rainfall in Cheongmicheon watershed. In this study, 6-hr rainfalls were disaggregated into hourly rainfall using the Multiplicative Random Cascade (MRC) model, which is a stochastic rainfall time disaggregation model and it was repeated 100 times to make 100 rainfalls for each storm event. The watershed runoff was estimated using the Clark unit hydrograph method with disaggregated rainfall and watershed characteristics. Using the peak discharges of the simulated hydrographs, the probability distribution was determined and parameters were estimated. Using the parameters, the probability density function is shown and the flood probability is calculated by comparing with the design flood of Cheongmicheon watershed. The flood probability results differed for various values of rainfall and rainfall duration. In addition, the flood probability calculated in this study was compared with the actual flood damage in Cheongmicheon watershed (R2 = 0.7). Further, this study results could be used for flood forecasting.

The Study on Development and Verification of Rainfall-Runoff Simulator for LID Technology Verification (LID 기술의 효율성 검증을 위한 강우-유출 모의장치 개발 및 검증실험에 관한 연구)

  • Jang, Young Su;Kim, Mi Eun;Baek, Jong Seok;Shin, Hyun Suk
    • Journal of Korea Water Resources Association
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    • v.47 no.6
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    • pp.513-522
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    • 2014
  • Climate change and urbanization have affected a increase of peak discharge and water pollution etc. In a view of these aspects, the LID(Low Impact Development) technology has been highlighted as one of adjustable control measures to mimic predevelopment hydrologic condition. Many LID technologies have developed, but there is a lack of studies with verification of LID technology efficiency. Therefore this study developed a rainfall-runoff simulator could be possible to verify LID technology efficiency. Using this simulator, this study has experimented the rainfall verification through the rainfall distribution experiment and the experiment to show the relation between inflow and effective rainfall in order to sprinkle the equal rainfall in each unit bed. As a result, the study defined the relation between allowable discharge range and RPM by nozzle types and verified the hydrologic cycle such as the relation between infiltration rate, surface runoff and subsurface runoff at pervious area and impervious area through the rainfall-runoff experiment.

Installation and operation of automatic nonpoint pollutant source measurement system for cost-effective monitoring

  • Jeon, Jechan;Choi, Hyeseon;Shin, Dongseok;Kim, Lee-hyung
    • Membrane and Water Treatment
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    • v.10 no.1
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    • pp.99-104
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    • 2019
  • In Korea, nonpoint pollutants have a significant effect on rivers' water quality, and they are discharged in very different ways depending on rainfall events. Therefore, preparing an optimal countermeasure against nonpoint pollutants requires much monitoring. The present study was conducted to help prepare a method for installing an automatic nonpoint pollutant measurement system for the cost-effective monitoring of the effect of nonpoint pollutants on rivers. In the present study, monitoring was performed at six sites of a river passing through an urban area with a basin area of $454.3km^2$. The results showed that monitoring could be performed for a relatively long time interval in the upstream and downstream regions, which are mainly comprised of forests, regardless of the rainfall amount. On the contrary, in the urban region, the monitoring had to be performed at a relatively short time interval each time when the rainfall intensity changed. This was because the flow rate was significantly dependent on the rainfall's intensity. The appropriate sites for installing an automatic measurement system were found to be a site before entering the urban region, a site after passing through the urban region, and the end of a river where the effects of nonpoint pollutant sources can be well-decided. The analysis also showed that the monitoring time should be longer for the rainfall events of a higher rainfall class and for the sites closer to the river end. This is because the rainfall runoff has a longer effect on the river. However, the effect of nonpoint pollutant sources was not significantly different between the upstream and the downstream in the cases of rainfall events over 100 mm.

Impact of Different Green-Ampt Model Parameters on the Distributed Rainfall-Runoff Model FLO-2D owing to Scale Heterogeneity (분포형 강우-유출 모형에서 토양도 격자크기 효과가 Green-Ampt 모형의 매개변수와 모의된 강우손실에 미치는 영향)

  • Hwang, Ji-hyeong;Lee, Khil-Ha
    • Journal of Environmental Science International
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    • v.29 no.1
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    • pp.15-23
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    • 2020
  • The determination of soil characteristics is important in the simulation of rainfall runoff using a distributed FLO-2D model in catchment analysis. Digital maps acquired using remote sensing techniques have been widely used in modern hydrology. However, the determination of a representative parameter with spatial scaling mismatch is difficult. In this investigation, the FLO-2D rainfall-runoff model is utilized in the Yongdam catchment to test sensitivity based on three different methods (mosaic, arithmetic, and predominant) that describe soil surface characteristics in real systems. The results show that the mosaic method is costly, but provides a reasonably realistic description and exhibits superior performance compared to other methods in terms of both the amount and time to peak flow.

An Analysis of Runoff Reduction Effect of Infiltration Facilities in Urban Area (도시유역에서 침투시설의 우수유출저감효과 분석)

  • Lee, Jae-Joon;Kim, Ho-Nyun;Kwak, Chang-Jae;Lee, Sang-Won
    • 한국방재학회:학술대회논문집
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    • 2007.02a
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    • pp.628-631
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    • 2007
  • One of the structural measures for the peak flow reduction is infiltration facilities. There are many types in infiltration facilities - infiltration basin, trench, bed, porous pavement, percolated subdrain, dry well. In this study runoff reduction effect of infiltration trench is analyzed by WinSLAMM. Runoff reduction effect is investigated by each design rainfall and temporal pattern of rainfall particularly. The biggest reduction is shown in Yen and Chow's temporal pattern of design rainfall and the smallest reduction is shown in Huff's first quartile pattern. Runoff reduction rate is presented about 6 to 14 percentage, and the larger return period, the smaller runoff reduction rate.

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