• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.59-62
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• 2008

Scour vulnerability evaluation for shallow foundations was performed to assure bridge safety against scour in the national capital region. The case studies for 26 shallow foundations consisted of site investigation including boring test, bridge scour analysis for the design flood, bearing capacity evaluation of the bridge foundation before and after scour, and comprehensive evaluation of bridge scour vulnerability. Bridge scour vulnerability was determined based on the interdisciplinary concept considering predicted scour depth for the design floods and bearing capacity of foundation as well as dimensions of foundation. Nine of 26 shallow foundations showed the potential future vulnerability to scour with significant decrease in the bearing capacity of foundations due to scour and the remaining 17 were expected to maintain their stability against scour.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2004.11a
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• pp.84-84
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• 2004

• Magazine of the Korean Society of Agricultural Engineers
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• v.28 no.3
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• pp.69-78
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• 1986

This studies were established to find out the characteristics of frequency distributiom for the number of occurrence and magnitude, probable flood flows according to the return periods, design floods, and design frequency factors for the studying basins in relation to the risk levels which can be correlated with design return period and the life of structure in the non-annual exceedance series. Eight watersheds along Han, Geum, Nak Dong and Seom Jin river basin were selected as studying basins. The results were analyzed and summarized as follows. 1. Poisson distribution and Exponential distribution were tested as a good fitted distributions for the number of occurrence and magnitude for exceedance event, respectively,at selected watersheds along Han, Geum, Nak Dong and Seom Jin river basin. 2.Formulas for the probable flood flows and probable flood flows according to the return periods were derivated for the exponential distribution at the selected watersheds along Han, Geum, Nak Dong, and Seom Jin river basin. 3.Analysis for the risk of failure was connected return period with design life of structure in the non-annual exceedance series. 4.Empirical formulas for the design frequency factors were derivated from under the condition of the return periods identify with the life of structure in relation to the different risk levels in the non-annual exceedance series. 5.Design freguency factors were appeared to be increased in proportion to the return periods while those are in inverse proportion to the levels of the risk of failure. Numerical values for the design frequency factors for the non-annual exceedance series ware appeared generally higher than those of annual maximum series already published by the first report. 6. Design floods according to the different risk levels could be derivated by using of formulas of the design frequency factors for all studying watersheds in the nor-annual exceedance series.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1182-1186
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• 2006

The decision of design flood in river basins is very important in the aspect of flood control. The design flood of rivers was estimated according to the size and importance of basins. As the damage of floods increases more and more and the importance of defense against floods increases further, the presumption of design flood can be very important. Especially, what influences most greatly flood is rainfall. However, in spite of equal rainfall, the estimated flood differ according to the features of basins. The fact that the features of basins influence greatly the estimation of flood was confirmed by the preceding research results and experiences. However, although many rivers have their own basin features, the research on how these basin features are related to the estimation of design flood, is not yet sufficient. The purpose of this study is to identify how the design flood estimated previously by river arrangement basic plan is correlated with topography factors, and so investigate the correlation between basin topography factors and design flood in order to provide the additional information for the unmeasured basins or the middle/small river basins where their river plan is not established.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.141-150
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• 1992

In this study, six gaging stations(T/M bureau) in the Han River basin were selected for flood frequency analysis and was carried out frequency analysis by POT(peaks Over a Threshold) model where existing flood data of short record length are available. Frequency and magnitudes of each station floods in the river basins were estimated by POT model based on statistical method, and also were compared with standard errors to verify applicability of the estimates by POT model. Furthermore, in order to evaluate for the adequate design flood which is needed for the design of the hydrologic structures in the ungaged watersheds, it is considered to be possible to develop the statistical regionalized model by regional frequency analysis.

• Ecology and Resilient Infrastructure
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• v.3 no.2
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• pp.117-125
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• 2016

Current cities encounter various types of water problems due to rapid urbanization and climate change. The increasing significance of urban water problems calls for the establishment of resilient alternatives to prevent and minimize social loss that results from these phenomena. As a background research for establishing resilient infrastructures for the mitigation of urban water problems, we evaluated the robustness of structural alternatives for urban flood as a representative case. Combining the robustness index (RI) and the cost index (CI), we suggested the robustness-cost index (RCI) as an indicator of the robustness of structural alternatives, and applied the index to assess the existing infrastructures and structural alternatives (i.e., sewer network expansion, additional storage tank construction, and green roof construction) at a site prone to floods located around Gangnam-station, Seoul, Korea. At a rainfall intensity frequency range of 2 to 20 years, the usage of a storage tank and a green roof showed relatively high RCI value, with a variation of an alternative showing greater RCI between the two depending on the size of design rainfall. For a rainfall intensity frequency of 30 years, installing a storage tank with some green roofing was the most resilient alternative based on the RCI value. We proposed strategies for establishing resilient infrastructures for the mitigation of urban floods by evaluating the robustness of existing infrastructures and selecting optimal structural alternatives with the consideration of scales of design disaster.

• Journal of Korea Water Resources Association
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• v.55 no.10
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• pp.737-748
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• 2022

Due to the lack of flood data, the water engineering practice calculates the design flood using rainfall frequency analysis and rainfall-runoff model. However, the rainfall frequency analysis for arbitrary duration does not reflect the regional characteristics of the duration and amount of storm event. This study proposed a practical method to calculate the design flood in a watershed considering the characteristics of storm event, based on the bivariate rainfall frequency analysis. After extracting independent storm events for the Pyeongchang River basin and the upper Namhangang River basin, we performed the bivariate rainfall frequency analysis to determine the design storm events of various return periods, and calculated the design floods using the HEC-1 model. We compared the design floods based on the bivariate rainfall frequency analysis (DF_BRFA) with those estimated by the flood frequency analysis (DF_FFA), and those estimated by the HEC-1 with the univariate rainfall frequency analysis (DF_URFA). In the case of the Pyeongchang River basin, except for the 100-year flood, the average error of the DF_BRFA was 11.6%, which was the closest to the DF_FFA. In the case of the Namhangang River basin, the average error of the DF_BRFA was about 10%, which was the most similar to the DF_FFA. As the return period increased, the DF_URFA was calculated to be much larger than the DF_FFA, whereas the BRFA produced smaller average error in the design flood than the URFA. When the proposed method is used to calculate design flood in an ungauged watershed, it is expected that the estimated design flood might be close to the actual DF_FFA. Thus, the design of the hydrological structures and water resource plans can be carried out economically and reasonably.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.758-763
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• 2006

Statistical concepts and methods are routinely utilized in a number of design and management problems in engineering hydrology. This is because most of hydrological processes have some degree of randomness and uncertainty. Thus, the concepts of risk and uncertainty are commonly utilized for designing and evaluating hydraulic structures such as spillways and dikes. Therefore, in this study, uncertainty analysis considering the variance of design floods is performed to evaluate the uncertainty of the hydrologic risk of flood related hydraulic structures using frequency analysis.

• Journal of Korea Water Resources Association
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• v.49 no.8
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• pp.645-656
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• 2016

The study performed a regional flood frequency analysis and proposed a regression equation to estimate design floods corresponding to return periods for ungauged basins in Geum-river basin. Five preliminary tests were employed to investigate hydrological independence and homogeneity of streamflow data, i.e. the lag-one autocorrelation test, time homogeneity test, Grubbs-Beck outlier test, discordancy measure test ($D_i$), and regional homogeneity measure (H). The test results showed that streamflow data were time-independent, discordant and homogeneous within the basin. Using five probability distributions (generalized extreme value (GEV), three-parameter log-normal (LN-III), Pearson type 3 (P-III), generalized logistic (GLO), generalized Pareto (GPA)), comparative regional flood frequency analyses were carried out for the region. Based on the L-moment ratio diagram, average weighted distance (AWD) and goodness-of-fit statistics ($Z^{DIST}$), the GLO distribution was selected as the best fit model for Geum-river basin. Using the GLO, a regression equation was developed for estimating regional design floods, and validated by comparing the estimated and observed streamflows at the Ganggyeong station.

• Proceedings of the Korea Contents Association Conference
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• 2006.11a
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• pp.403-407
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• 2006

This research aims to reduce severe damages to human beings and properties from floods that ravage Korea every year, by estimating right time to hydraulic structures based on the characteristics of variations in flood flows. To establish this permanent means for the flood mitigation, this research analyse design floods of various dams and hydraulic structures in connection with time of occurrence of the weather abnormalities in Korea. This research was derived the optimal regionalization of the precipitation data which can be classified by the climatologically and geographically homogeneous regions in Korea. Using the L-moment ratios and Kolmogorov-Smimov test, the underlying regional probability distribution was identified to be the GEV distribution among applied distributions. The regional and at-site analyses using L-moment for the design rainfall were tested by Monte Carlo simulation. Error tests were computed and compared with those resulting from at-site Monte Carlo simulation. Consequently, optimal design rainfalls following the regions and consecutive durations were derived by the regional frequency analysis.