• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.3
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• pp.41-50
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• 1999

Derivatio of reasonable design floods was attempted by comparative analysis of design floods derived by Generalized Extreme Value(GEV) distribution using methods of L-moments and LH-moments for the annual maximum series at ten watersheds along Han, Nagdong. Geum, Yeongsan and Seomjin river systems, LH-coefficient of variation, LH-skewness and Lh-kurtosis were calcualted by KH-moment ration respectively. Paramenters were estimated by the Method of LH-Moments, Design floods obtained by Method of LH-Moments using different methods for plotting positionsi n GEV distribution and design floods were compared with those obtained using the Method of L-Moments by the Relative Mean Errors(RME) and Relative Absolute Errors(RAE). The results was found that design floods derived by the method of L-Moments and LH-Moments using Cunnane plotting position formula in the GEV distribution are much closer to those of the observed data in comparison with those obtained by methods of L-moments and LH-moments using the other formula for plotting positions from the viewpoint of Relative Mean Errors and Relative Absolute Errors. In viewpoint of the fact that hydrqulic structures including dams and levees are genrally using design floods with the return period of two hundred years or so, design floods derived by LH-Moments are seemed to be more reasonable than those of L-Moments in the GEV distribution.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.362-362
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• 2020

Flash flood is a dangerous weather phenomenon, affecting humans and the economy. The identification, forecast of the changing trend and its characteristics are increasingly concerned. In the world, there have many methods for determining the characteristics of flash floods, in which flash flood guidance (FFG) is a fast, effective and widely used method. The main source of flash floods is short-term rainfall. In this study, we used the data of cross-sectional measurement at the tributaries and the hourly rain data from the automatic rainfall measurement stations in the Geum river basin. Besides, we use a combination of the flash flood guidance and the best fit distribution function to estimate the repeatability of flash floods for head-water catchments in Geum river basin. In which, FFG determines the threshold of rainfall for flash floods. The study has determined the best hourly rainfall distribution function for the Geum river basin and estimated the maximum rainfall of 1hr according to the return periods.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.33-39
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• 2008

Most New Zealanders reside in coastal regions and four of the larger cities are situated on active floodplains. There have been many recent storm events with rainfall AEPs of 1/150 or rarer and there have been recent flood-related disasters. Insurance claim statistics indicate that the frequency of floods is increasing. Such statistics are alarming local government authorities, insurance companies and populations in low-lying areas. The underlying physical and hydrologic causes of the flood disasters are investigated. It is found that the present numbers of rare rainfall events are not unexpected and there does not appear to be any significant trend evident in the occurrence of river floods. What is revealed is that the river floods appear clustered in certain decades. The clusters do not occur at the same times in different parts of the county. Recently there have been more floods in the north of New Zealand which is where more of the population lives. Also, the increase in population has seen more houses built in locations prone to flooding. Thus the increase in flood-related insurance claims is attributed to more people getting in the way of floods, rather than an increase in the number of floods that have occurred.

• Journal of the Society of Disaster Information
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• v.9 no.4
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• pp.462-468
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• 2013

Walls for preventing floods using overturning or buoyancy method have been developed as replacement construction for preventing floods in and outside country. However, as they have some problems with pre-inspection and maintenance control, Eco-moving wall structure for preventing floods was studied and first developed using Glass Fiber Reinforced Composite which has not only light weight but outstanding strength. The developed wall structure for preventing floods offering structural stability and field applicability through numerical analysis was confirmed to reduce construction expenses by around 87~95% and secure waterproof property with the inside of the wall installed rubber water stopper.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.11a
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• pp.389-392
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• 2004

A recent unusual change in the weather is formed as a localized heavy rain in a short time. This phenomenon has caused a flash flood, and flash floods extensively have damaged human lives many times. In large river's case, the extent of loss of lives and properties has been decreased through the flood warning system by flood control stations of each stream. However, the extent of damage in other small rivers has increased reversely. Therefore, it is necessary to establish a new flood warning system against flash floods instead of the existing flood warning system. It is a specific character that the damage from flash floods in mountain streams brings much more loss of lives than large river's flood. The purpose of this study is calculating the characteristic of flash floods in streams, analyzing topographical characteristics of water basin through applying GIS techniques with the calculation as mentioned above and researching what topographical conditions have influence on hydrological flash floods in water basin. The flash flood prediction model we used is made by GIUH (geomorphoclimatic instantaneous unit hydrograph) with hydrologic-topographical technology. As applying the flash flood prediction model, this is a procedure for calculating topographical information in basin: we made a topological data up out of database with utilizing GIS, and we also produced a DEM (digital elevation model) and used it as a topographical data for determining amount of flash floods.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.2
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• pp.59-68
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• 1998

This study was conducted to derive optimal design floods by generalized gamma distribution model of the annual maximum series at eight watersheds along Geum, Yeongsan and Seomjin river systems. Design floods obtained by different methods for evaluation of parameters and for plotting positions in the generalized gamma distribution model were compared by the relative mean errors and graphical fit along with 95% confidence limits plotted on gamma probability paper. The results were analyzed and summarized as follows. 1. Basic statistics and parameters were calculated by the generalized gamma distribution model using different methods for parameters. 2. Design floods according to the return periods were obtained by different methods for evaluation of parameters and for plotting positions in the generalized gamma distribution model. 3. It was found that design floods derived by sundry averages method for parameters and Cunnane method for plotting position in the generalized gamma distribution are much closer to those of the observed data in comparison with those obtained by the other methods for parameters and for plotting positions from the viewpoint of relative mean errors. 4. Reliability of design floods derived by sundry averages method in the generalized gamma distribution was acknowledged within 95% confidence interval.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.5
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• pp.17-27
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• 2006

The objective of this study is to induce the design floods by the methodology of L-moment including test of homogeneity, independence and outlier of the data of annual maximum flood flows for 12 water level gaging stations of South Korea. To select appropriate distribution of the data for annual maximum flood flows, the distributions of Wakeby and Kappa are applied and the appropriateness is judged by Kolmogorov-smirnov (K-S) test. The parameters of selected Wakeby and Kappa distributions are calculated by the method of L-moment and the design floods are induced. Through the comparative analysis using the relative root mean square errors (RRMSE) and relative absolute errors (RAE) of design floods, the result shows that the design floods by Wakeby distribution are closer to the observed data than those obtained by the Kappa distribution.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.4
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• pp.49-55
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• 2009

This paper is to induce design floods through L-moment with 3 and 4 parameter Kappa distributions including test of independence by Wald-Wolfowitz, homogeneity by Mann-Whitney and outlier by Grubbs-Beck on annual maximum flood flows at 9 water level gaging stations in Han, Nakdong and Geum Rivers of South Korea. After analyzing appropriateness of the data of annual maximum flood flows by Kolmogorov-Smirnov test, 3 and 4 Kappa distributions were applied and the appropriateness was judged. The parameters of 3 and 4 Kappa distributions were estimated by L-moment method and the design floods by water level gaging station was calculated. Through the comparative analysis using the relative root mean square errors (RRMSE) and relative absolute errors (RAE) calculated by 3 and 4 parameter Kappa distributions with 4 plotting position formulas, the result showed that the design floods by 4 parameter Kappa distribution with Weibull and Cunnane plotting position formulas are closer to the observed data than those obtained by 3 parameter Kappa distribution with 4 plotting position formulas and 4 parameter Kappa distribution with Hazen and Gringorten plotting position formulas.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.479-485
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• 1999

This study was conducted to derived design floods by Generalized Extreme Value(GEV) distributiion for the annual maximum series at ten watersheds along Han, Nagdong, Geum , Yeongsan and Seomjin river systems. Adequency for the analysis of flood data used in this study was established by the test of Independence, Homogeneity , detection of Outliers. Coefficient of variation , skewness and kurtosis were calculated by the L-Moment, and LH-Moment ratio respectively. Parameters were estimated by the Method of L-Method of LH-Moment. Design floods obtained by Method of L-Moments and LH-Moments using different methods for plotting positions in GEV distributions and were compared with those obatined using the Method of L-Moments and LH-Moments by the Relative Mean Errors and Realtive Absoulte Errors. It was found that desgin floods derived by the method of L-Moments and LH-Moments using Cunnane plotting position foumula in the GEV distribution are much closer to those of the observed data in comparison with those obtained by methods of L-moments and LH-moments using the other formula for poltting postions from the viewpoint of Relative Mean Errors and Relative Absoulte Errors. In view of the fact that hydraulic structures indcluding dams and levees are generally usiong design floods with the return period of two hundred years or so, design floods derived by LH-Moments are seemed to be more reasonable than those of L-Moments in the GEV distribution.

• Water for future
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• v.7 no.2
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• pp.34-46
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• 1974

This paper provides a new geomorphological approach for survey of potential flood damages and for preparation of cartographically accurate flood maps. floods are possibly the worst disasters we have recorded in he past and may expect in the future. Interpretation of aerial photographs of river basin enables us to determine the nature of floods by investigating the maximum extent of inundated areas in the past. Most of the typical dangerous spots, highly susceptible for flood disasters can be systematically identified by analyzin lithologic, structural, and geomorphic cycle.