• Title/Summary/Keyword: flood frequency analysis

Search Result 302, Processing Time 0.031 seconds

Derivation of Flood Frequency Curve with Uncertainty of Rainfall and Rainfall-Runoff Model (강우 및 강우-유출 모형의 불확실성을 고려한 홍수빈도곡선 유도)

  • Kwon, Hyun-Han;Kim, Jang-Gyeong;Park, Sae-Hoon
    • Journal of Korea Water Resources Association
    • /
    • v.46 no.1
    • /
    • pp.59-71
    • /
    • 2013
  • The lack of sufficient flood data being kept across Korea has made it difficult to assess reliable estimates of the design flood while relatively sufficient rainfall data are available. In this regard, a rainfall simulation based derivation technique of flood frequency curve has been proposed in some of studies. The main issues in deriving the flood frequency curve is to develop the rainfall simulation model that is able to effectively reproduce extreme rainfall. Also the rainfall-runoff modeling that can convey uncertainties associated with model parameters needs to be developed. This study proposes a systematic approach to fully consider rainfallrunoff related uncertainties by coupling a piecewise Kernel-Pareto based multisite daily rainfall generation model and Bayesian HEC-1 model. The proposed model was applied to generate runoff ensemble at Daechung Dam watershed, and the flood frequency curve was successfully derived. It was confirmed that the proposed model is very promising in estimating design floods given a rigorous comparison with existing approaches.

Comparison of flood inundation simulation between one- and two-dimensional numerical models for an emergency action plan of agricultural reservoirs

  • Kim, Jae Young;Jung, Sung Ho;Yeon, Min Ho;Lee, Gi Ha;Lee, Dae Eop
    • Korean Journal of Agricultural Science
    • /
    • v.48 no.3
    • /
    • pp.515-526
    • /
    • 2021
  • The frequency of typhoons and torrential rainfalls has increased due to climate change, and the concurrent risk of breakage of dams and reservoirs has increased due to structural aging. To cope with the risk of dam breakage, a more accurate emergency action plan (EAP) must be established, and more advanced technology must be developed for the prediction of flooding. Hence, the present study proposes a method for establishing a more effective EAP by performing flood and inundation analyses using one- and two-dimensional models. The probable maximum flood (PMF) under the condition of probable maximum precipitation (PMP) was calculated for the target area, namely the Gyeong-cheon reservoir watershed. The breakage scenario of the Gyeong-cheon reservoir was then built up, and breakage simulations were conducted using the dam-break flood forecasting (DAMBRK) model. The results of the outflow analysis at the main locations were used as the basis for the one-dimensional (1D) and two-dimensional (2D) flood inundation analyses using the watershed modeling system (WMS) and the FLUvial Modeling ENgine (FLUMEN), respectively. The maximum inundation area between the Daehari-cheon confluence and the Naeseong-cheon location was compared for each model. The 1D flood inundation analysis gave an area of 21.3 km2, and the 2D flood inundation analysis gave an area of 21.9 km2. Although these results indicate an insignificant difference of 0.6 km2 in the inundation area between the two models, it should be noted that one of the main locations (namely, the Yonggung-myeon Administrative and Welfare Center) was not inundated in the 1D (WMS) model but inundated in the 2D (FLUMEN) model.

Regional Frequency Analysis for Future Precipitation from RCP Scenarios (대표농도경로 시나리오에 의한 미래 강수량의 지역빈도해석)

  • Kim, Duck Hwan;Hong, Seung Jin;Choi, Chang Hyun;Han, Dae Gun;Lee, So Jong;Kim, Hung Soo
    • Journal of Wetlands Research
    • /
    • v.17 no.1
    • /
    • pp.80-90
    • /
    • 2015
  • Variability of precipitation pattern and intensity are increasing due to the urbanization and industrialization which induce increasing impervious area and the climate change. Therefore, more severe urban inundation and flood damage will be occurred by localized heavy precipitation event in the future. In this study, we analyze the future frequency based precipitation under climate change based on the regional frequency analysis. The observed precipitation data from 58 stations provided by Korea Meteorological Administration(KMA) are collected and the data period is more than 30 years. Then the frequency based precipitation for the observed data by regional frequency analysis are estimated. In order to remove the bias from the simulated precipitation by RCP scenarios, the quantile mapping method and outlier test are used. The regional frequency analysis using L-moment method(Hosking and Wallis, 1997) is performed and the future frequency based precipitation for 80, 100, and 200 years of return period are estimated. As a result, future frequency based precipitation in South Korea will be increased by 25 to 27 percent. Especially the result for Jeju Island shows that the increasing rate will be higher than other areas. Severe heavy precipitation could be more and more frequently occurred in the future due to the climate change and the runoff characteristics will be also changed by urbanization, industrialization, and climate change. Therefore, we need prepare flood prevention measures for our flood safety in the future.

Regional Frequency Analysis of South Korean Rainfall Data Using FORGEX Method (FORGEX 기법을 이용한 한국 강우자료의 지역빈도해석에 관한 연구)

  • Kim, Jung-Won;Nam, Woo-Sung;Shin, Ju-Young;Heo, Jun-Haeng
    • Journal of Korea Water Resources Association
    • /
    • v.41 no.4
    • /
    • pp.405-412
    • /
    • 2008
  • Rainfall quantiles were estimated by applying the FORGEX method. The circle network and two elliptical ones with the ratios of 1 to 1.5 and 1 to 2.0 were used and compared to find appropriate one for rainfall data. Annual maximum data were collected from 376 sites and standardized by the median. The networks were organized from the subject sites and then pooled and netmax data were collected from each network. Then, the growth curves and quantiles were estimated. When the subject site had small differences of quantiles from index flood method and at-site frequency analysis, those of the estimated quantiles from circle and elliptical networks were small. In contrast, the sites where the quantile differences are big have big differences of quantiles from circle and elliptical networks. The estimated quantiles from the elliptical network are more accurate than those from the circle network, because the ellipse network contains more sites in South Korea. Moreover, the ellipse with ratio of 1 to 2.0 shows closer quantiles to those from index flood method than one with ratio of 1 to 1.5. It is, therefore, found that the FORGEX method with 1 to 2.0 ellipse network is appropriate regional frequency analysis in South Korea.

Study on the Inundation at the Merging Area of Osipcheon and Local Stream Using a Two-Dimensional Model (2차원 모형을 이용한 삼척오십천 소하천 합류 지점 침수해석에 관한 연구)

  • Do Jin Kim;Kye Won Jun
    • Journal of Korean Society of Disaster and Security
    • /
    • v.16 no.4
    • /
    • pp.61-66
    • /
    • 2023
  • In this study, we analyzed the flooded area around Samcheok Middle School caused by typhoons MAYSAK·HAISHEN in September 2020. To analyze the confluence of Samcheok Osipcheon, local stream Deungbongcheon, we utilized Iber, a two-dimensional hydraulic model. We simulated the water depth and flood extent based on the peak flows on September 3 and September 7, 2020, and the 80 year and 100 year frequency floods. The simulation results showed that the 80-year frequency flood and the 100-year frequency flood on September 7 were insignificantly different, but the maximum flow rate from September 3 to September 7 was significantly different at 401 m3/s, resulting in a difference of 0.8 m in water depth and 7.1 m2 in flood area. In addition, the analysis that considered only the contour lines using contour lines predicted inundation of not only the Samcheok Middle School playground but also the building, confirming the need to apply DSM.

Palaeoflood Study by using the Slackwater Deposits (Slackwater 퇴적물을 이용한 고범람 연구)

  • KIM, SongHyun;TANAKA, Yukiya
    • Journal of The Geomorphological Association of Korea
    • /
    • v.18 no.4
    • /
    • pp.163-175
    • /
    • 2011
  • Slackwater deposits are fine-grained flood sediments that deposited in areas of reduced velocity during flood period. These deposits have been used in numerous studies to estimate the magnitude and frequency of discrete flood events as the most commonly utilized PSIs (palaeostage indicators) in palaeoflood hydrology. Palaeoflood data by analysis of the slackwater deposits contribute to improve the estimation of flood-probability and reconstruct the palaeo-environment and past fluvial process. However, very few studies of these flood deposits have been carried out in Korea. Therefore, this study attempts to review the studies about slackwater deposits analysis and to investigate the characteristics, the research methods of slackwater deposits and the research-provability in Korea.

Analysis of Flood Control Capacity of Agricultural Reservoir Based on SSP Climate Change Scenario (SSP 기후변화 시나리오에 따른 농업용 저수지 홍수조절능력 분석)

  • Kim, Jihye;Kwak, Jihye;Hwang, Soonho;Jun, Sang Min;Lee, Sunghack;Lee, Jae Nam;Kang, Moon Seong
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.63 no.5
    • /
    • pp.49-62
    • /
    • 2021
  • The objective of this study was to evaluate the flood control capacity of the agricultural reservoir based on state-of-the-art climate change scenario - SSP (Shared Socioeconomic Pathways). 18 agricultural reservoirs were selected as the study sites, and future rainfall data based on SSP scenario provided by CMIP6 (Coupled Model Intercomparison Project 6) was applied to analyze the impact of climate change. The frequency analysis module, the rainfall-runoff module, the reservoir operation module, and their linkage system were built and applied to simulate probable rainfall, maximum inflow, maximum outflow, and maximum water level of the reservoirs. And the maximum values were compared with the design values, such as design flood of reservoirs, design flood of direct downstream, and top of dam elevation, respectively. According to whether or not the maximum values exceed each design value, cases were divided into eight categories; I-O-H, I-O, I-H, I, O-H, O, H, X. Probable rainfall (200-yr frequency, 12-h duration) for observed data (1973~2020) was a maximum of 445.2 mm and increased to 619.1~1,359.7 mm in the future (2011~2100). For the present, 61.1% of the reservoirs corresponded to I-O, which means the reservoirs have sufficient capacity to discharge large inflow; however, there is a risk of overflowing downstream due to excessive outflow. For the future, six reservoirs (Idong, Baekgok, Yedang, Tapjung, Naju, Jangsung) were changed from I-O to I-O-H, which means inflow increases beyond the discharge capacity due to climate change, and there is a risk of collapse due to dam overflow.

Design Flood Estimation using Historical Rainfall Events and Storage Function Model in Large River Basins (과거강우사상과 저류함수모형을 이용한 대유역 계획홍수량 추정)

  • Youn, Jong-Woo;Lee, Dong-Ryul;Ahn, Won-Sik;Rim, Hae-Wook
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.29 no.3B
    • /
    • pp.269-279
    • /
    • 2009
  • The design flood estimation in a large river basin has a lot of uncertainties in areal reduction factors, time-spatial rainfall distribution, and parameters of rainfall-runoff model. The use of historical concurrent rainfall events for estimating design flood would reduce the uncertainties. This study presents a procedure for estimating design floods using historical rainfall events and storage function model. The design rainfall and time-spatial distribution were determined through analyzing concurrent rainfall events, and the design floods were estimated using storage function model with a non-linear hydrology response. To evaluate the applicability of the procedure of this study, the estimated floods were compared to results of frequency analysis of flood data. Both floods gave very similar results. It shows the applicability of the procedure presented in this study for estimating design floods in practices.

Estimating design floods in ungauged watersheds through regressive adjustment of flood quantiles from the design rainfall - runoff analysis method (설계강우-유출 관계 분석법에 의한 확률홍수량의 회귀보정을 통한 미계측 유역의 설계홍수량 산정)

  • Chae, Byung-Seok;Lee, Jin-Young;Ahn, Jae-Hyun;Kim, Tae-Woong
    • Journal of Korea Water Resources Association
    • /
    • v.50 no.9
    • /
    • pp.627-635
    • /
    • 2017
  • It is required to estimate reliable design floods for hydraulic structures in order to respond more effectively to recent climate change. In this study, differences of design floods that were estimated the flood frequency analysis (FFA) and the design rainfall-runoff analysis (DRRA) were analyzed. In Korea, due to lack of measured flood data, the DRRA method is used in practice to determine the design floods. However, assuming the design floods estimated by the FFA as true values, the DRRA method over estimated the design floods by 79%. Thus, this study proposed a practical method to estimated design flood in ungauaged watersheds through regressive adjustment of flood quantiles estimated from the DRRA method. To this end, after investigating the differences between design floods acquired from the FFA and the DRRA method, nonlinear regression analyses were performed to develop the adjustment formulas for 8 large-dam watersheds. Applying the adjustment formula, the accuracy was improved by 65.0% on average over the DRRA method. In addition, when considering the watershed size, the adjustment formula increases the accuracy by 2.1%p on average over when not considering the watershed size.