• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.163-167
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• 2004

Creeks, defined by creek's improvement law, have strong localities in the flow characteristics and environmental condition. During the recent ten-years, lots of flood damages have occurred rather in the creeks. However, quantity and stream design information are poor while the national-class and local-class streams have sufficient. This causes a problem on improving the safety from flood. This study focuses on assessment of practical applicability for design flood estimation models. For this, Rational formula, Clark's model and Nakayath synthetic unit hydrograph method are estimated by data of the creek comprehensive improvement plan report, etc.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1172-1175
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• 2006

Generally, the estimation of design flood uses basin rainfall data, water level data, and runoff data, and so forms rainfall-runoff model. Because owing to the lack of hydrological data, the decision of representative unit hydrograph about the basin is difficult, the estimation of design flood uses topography feature data, and so presumes variables, and then applies the presumed variables to the model. In estimating design flood by using the model, it is considerably difficult to analyze how the model input variables estimated by topography factors, or the design flood data estimated previously are related to basin feature factors as the basic data, and presume design flood in the unmeasured basins or the basins where river arrangement basic plan is not established. The purpose of this study is to analyze how the design flood estimated previously by river arrangement basic plan is correlated with topography factors in presuming design flood, and so examine the presumption measures of design flood by using topography feature data and probability rainfall data.

• 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.

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.132-137
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• 2018

Compared with general rivers, fluctuations of the water level and the river bed are severe in the tidal river. In hydro-dynamic aspect, such fluctuation gives different river-bed data to us according to observing period. The time-dependent river-bed data and pre-estimation of the Manning's roughness coefficient which is the key factor of numerical modelling induces uncertainty of evaluating the design flood level. Thus it is necessary to pay more attention to calculate the flood level at tidal rivers than at general rivers. In this study, downstream of the Imjin River where is affected by tide of the West Sea selected as a study site. From the numerical modelling, it was shown that the unsteady simulation gave considerable mitigation of the water level from the starting point to 15 km upstream compared to the steady simulation. Either making a detention pond or optional dredging was not effective to mitigate the flood level at Gugok - Majung region where is located in the downstream of the Imjin River. Therefore, a more sophisticated approach is required to evaluate the design flood level estimation before constructive measures adopted in general rivers when establishing the flood control plan in a tidal river.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.3
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• pp.68-80
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• 2013

The purpose of this study is to evaluate the applicability of UK design flood estimation model, FEH-ReFH through rainfall-runoff simulation of Korean watershed. For the Nam stream watershed($165.12km^2$), the model was calibrated using 6 storm events. The watershed and hydrological characteristics for the model requirements was prepared by developing input data pre-processors based on open GIS. The parameters of rainfall loss rate and unit hydrograph were calibrated from the observed data. The results can be used for improving and standardizing the Korean design flood estimation method.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.107-113
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• 2009

The purpose of this study is to estimate the design flood runoff for ungaged forest watershed to reduce the flood damage in national park. Daewonsa watershed in Jirisan National Park was selected as study watershed, of which characteristic factors were obtained from GIS data. Flood runoff was simulated using SCS unit hydrograph module in HEC-HMS model. SCS Curve Number (CN) was calculated from forest type area weighted average method. Huff's time distribution of second-quartile storm of the Sancheong weather station, which is nearest from study watershed, was used for design flood runoff estimation. Critical storm duration for the study watershed was 3 hrs. Based on the critical duration, the peak runoff for each sub-watershed were simulated. It is recommended to monitor the long-term flow data for major stream stations in National Park for a better reliable peak runoff simulation results.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.937-942
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• 2005

It is necessary to estimate the runoff hydrograph and peak flood discharge using law of probability for synthetic flood control policy and design of hydraulic structures. Rainfall analysis is needed in the process of peak flood discharge estimation and the time distribution of a design rainfall is a very important process in the analysis. In this study, we estimate design flood for a small urban basin and a rural basin of medium scale which have different travel times. The Huff method is widely used in Korea for the time distribution of design rainfall to estimate design flood. So, we use Huff method and a conceptual method which is suggested in this study for the comparative purpose. The 100-year frequency rainfall is used to estimate design flood for each basin and the design flood is compared with the existing design flood. As the result, the design flood is overestimated $14.6m^3/sec$ by Huff method and is underestimated $70.9m^3/sec$ by a conceptual method for the rural basin. For the small urban basin, the design flood is excessively overestimated $294.65m^3/sec$ by Huff method and is overestimated $173m^3/sec$ by a conceptual method. The reason of excessive overestimation by Huff method in the small urban basin is that the increased rate of rainfall intensity according to the decrease of duration is large and the duration exceeds the time of concentration when the increased rainfall intensity is concentrated in a quartile. Therefore, we suggested a conceptual method for the time distribution of design rainfall by considering the rainless period and duration. Especially, the conceptual method might be useful for the small urban basin with short concentration time which the design flood is overestimated by Huff method.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1191-1195
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• 2006

Now days, heavy storm occur to be continue. It is hard to use before frequency based on flood discharge for decision that design water pocket structure. We need to estimation of frequency based on flood discharge on the important basin likely city or basin that damage caused by flood recurrence. In this paper flood discharge calculated by Clark watershed method and SCS synthetic unit hydrograph method about upside during each minute of among time distribution method of rainfall, Huff method choosing Bocheong Stream basin that is representative basin of International Hydrologic Project (IHP) about time distribution of rainfall that exert big effect at flood discharge estimate to research target basin because of and the result is as following. Relation between probability flood discharge that is calculated through frequency analysis about flood discharge data and rainfall - runoff that is calculated through outward flow model was assumed about $48.1{\sim}95.9%$ in the case of $55.8{\sim}104.0%$, SCS synthetic unit hydrograph method in case of Clark watershed method, and Clark watershed method has big value overly in case of than SCS synthetic unit hydrograph method in case of basin that see, but branch of except appeared little more similarly with frequency flood discharge that calculate using survey data. In the case of Critical duration, could know that change is big area of basin is decrescent. When decide time distribution type of rainfall, apply upside during most Huff 1-ST because heavy rain phenomenon of upsides appears by the most things during result 1-ST about observation recording of target area about Huff method to be method to use most in business, but maximum value of peak flood discharge appeared on Huff 3-RD too in the case of upside, SCS synthetic unit hydrograph method during Huff 3-RD incidental of this research and case of Clark watershed method. That is, in the case of Huff method, latitude is decide that it is decision method of reasonable design floods that calculate applying during all $1-ST{\sim}4-TH$.

• Proceedings of the Korea Water Resources Association Conference
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• 1989.07a
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• pp.17-30
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• 1989

In this study, more exact runoff phenomina of the watersheds were comprehened and the relationships between geographical factors of the selected watershed and the unit hydrograph characteristic variables representing runoff processes, were also established. Moreover, the estimation of the adequate design flood was presented, which is needed for the design of the hydrologic structures in the ungauged watersheds. And owing to these results, it is considered to be possible to execute the effective flood control projects of the river and the efficient water resources management.

• Water for future
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• v.22 no.4
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• pp.423-433
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• 1989

In this study, more exact runoff phenomina of the watersheds were comprehended and the relationships between geographical factors of the selected watershed and the unit hydrograph characteristic variables representing runoff processes, were also established. Moreover, the estimation of the adequate design flood was presented, which is needed for the design of the hydrologic structures in the ungauged watersheds. And owing to these results, it is considered to be possible to execute the effective flood control projects of the river and the efficient water resources management.