• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.87-92
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• 2009

It has been considered only with the concerned regional damage costs whenever the restoration and flood control measures were established in Korea. If the relationship between regional flood frequency and damages is quantitatively analyzed, more resonable and reliable countermeasure for flood protection and restoration can be proposed. Historical data ('70~'07) about flood damage in Korea were utilized and analyzed to present such relationship using the point frequency analysis. Also, the quadrant analysis was employed to divide into 4 categories: high frequency-high damage, high frequency-low damage, low frequency-high damage, and low frequency-low damage. If the results from this study were utilized well in specific cities and counties in Korea, it would be helpful to establish the countermeasures and action plans for flood protection because it was possible to compare with the relationship between flood frequency and damage of each region. And it would be the fundamental data for estimating the effect of future flood protection plan.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.511-517
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• 2006

Flood damage is one of the most important and influential natural disaster which has an effect on human beings. Local concentrated heavy rainfall in urban area yields flood damage increase due to insufficient capacity of drainage system. When the excessive flood occurs in urban area, it yields huge property losses of public facilities involving roadway inundation to paralyze industrial and transportation system of the city. To prevent such flood damages in urban area, it is necessary to develop adequate inundation analysis model which can consider complicated geometry of urban area and artificial drainage system simultaneously. In this study, an urban flood analysis model adopting the unstructured computational grid was developed to simulate the urban flood characteristics such as inundation area, depth and integrated with subsurface drainage network systems. By the result, we can make use of these presented method to find a flood hazard area and to make a flodd evacuation map. The model can also establish flood-mitigation measures as a part of the decision support system for flood control authority.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.743-746
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• 2008

Recently, due to the effect of global warming and extreme rainfall, the magnitude of flood disaster and the frequency of flood is rapidly increasing. In order to mitigate the damage of human and property from this kind of meteorological phenomenon and manage water resources scientifically, effective operation of dam and reservoir is very important. In case of Andong dam which was not performed a flood control function needs to develop new types of dam safety management measure because of recent extraordinary flood by typhoons. In case of Andong dam and Imha dam, I am using HEC-5 model in order to apply reservoir simulation. In this case, complex conditions among 100-year floods , 200-year floods and PMF was used. Also, I modified the maximum outflow 3,800m3/s into 3,490m3/s and applied this modified discharge in order to secure freeboard in the downstream. In an analysis that I applied modified outflow by 100-year floods and 200-year floods to, the result showed that river didn't overflow in Andong area but some other places have relatively low freeboard. In the cases that I modified maximum outflow, results showed that freeboard of levee is larger than existed simulation. In the simulation that I applied 200-year floods and PMF to and under a condition connected with PMF, results showed overflowing the levees. Because of the difference between the frequency of dam outflow and the design flood in river, it is required to improve the existed flood plan in the downstream of Andong dam. As a result of this study, the optimal operation of reservoir systems can be proposed to mitigate the flood damage in the downstream of Andong dam and also can be used to establish the flood plans.

• Journal of Korea Water Resources Association
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• v.31 no.4
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• pp.469-481
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• 1998

A point frequency analysis is carried out for the Indogyo site at the Han river using 68 annual maximun flood data for the period of 1918-1992. Computed frequency discharges using the three parameter log-normal, type-I extreme value, type-III extreme value, and Pearson type-III computed as 35,500 m3/sec and 39,000 m3/sec, respectively, 33,500 m3/sec and 37,500 m3/sec of corresponding return periods are computed when the flood control effect of the dams are taken into account. The resulting flood discharge of 37,500 m3/sec is similar to the current design flood of 37,000 m3/sec in downstream reach of Han river, so, it could be desirable to keep the the current design flood, considering the increasing tendency of the flood due to the climate change. Keywords : frequency analysis, flood discharge, Han river.

• Journal of Environmental Impact Assessment
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• v.27 no.3
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• pp.251-266
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• 2018

This study predicted the effect of operation pattern of flood control dam on water quality. Flood control dam temporarily impound floodwaters and then release them under control to the river below the dam preventing the river ecosystem from the extreme flood. The Hydrological Simulation Program Fortran (HSPF) and the Environmental Fluid Dynamics Code (EFDC) were adapted to predict the water quality before and after the dam construction in the proposed reservoir. The non-point pollutant delivery load from the river basin was estimated using the HSPF, and the EFDC was used to predict the water quality using the provided watershed boundary conditions from the HSPF. As a result of water quality simulation, it is predicted that the water quality will be improved due to the decrease of pollution source due to submergence after dam construction and temporary storage during rainfall. There would be no major water quality issues such as the eutrophication in the reservoir since the dam would impound the floodwater for a short time (2~3 days). In the environmental impact assessment stage of a planned dam, there may be some limitations to the exact simulation because the model can not be sufficiently calibrated. However, if the reliability of the model is improved through the acquisition of actual data in the future, it will be possible to examine the influence of the water environment according to various operating conditions in the environmental impact assessment of the new flood control dam.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.3
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• pp.101-107
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• 2010

The purpose of this study is to evaluate the benefits of flood control reservoir and to derive the policy implication by significant variables of willingness to pay. As a result of analyzed using contingent valuation method, variables that affect the amount of willingness to pay are housing area, frequency of disasters, educational background, and family income. All variables are analyzed as the plus effect for the willingness to pay, and the annual benefits of flood control reservoir per family are estimated as approximately 32,000 won. The implication of this study is as followed. First, the value of the respondents about public goods is not small. Second, the contingent valuation method can be useful plan to estimate the value of public goods. Finally, the benefits should be compared with various aspects because of the wide deviation of the demand population.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.5
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• pp.68-76
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• 1999

The purpose of the study was to investigated the change of hydraulic characteristics like water surface profile and rivered section in the down stream of Keum river after the construction of esturary dam. The effect of esturary dam on the flood control in the Keum river was recognized with the data of two flood events happened in July, 1987 before the construction and in August, 1995 after the construction of estuary dam. For example , duration time above the water level of the warning -flood was changed from 46.5 to 42.8 hours and duration time above the eater level of the danger-flood was changed from 24.7 to 19.8 hours at the Kyuam station. The time difference to reach the water level of the designated -flood between Kyuam and Kangkyung was changed from 3 hours in 1987 to 12 hours and 20 minutes in 1995. The water surface slope of river decreased 25.6% between estuary dam and Kangkyung and increased 16.5% between Kangkyung and Kyuam, and decreased 8.8% between Kyuam and Kongju. As the result, velocity was getting faster and river bed was scoured in the reach of Kangkyung and Kyuam, and velocity was getting slower and river bed was sedimented in the reach of Kangkyung and estury dam.

• Journal of Korea Water Resources Association
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• v.41 no.7
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• pp.725-735
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• 2008

Due to recent climate change, flood damages have been increased, but it is difficult to construct large hydraulic structure for flood control such as dam because of environmental, economical and political problems. For this reason, several researches and studies have tried to use washland as an alternative of hydraulic facility. Because sizes of washlands are usually smaller than those of dams or reservoirs, there can be many available locations for washlands in a basin and proper combination of these locations can reduce flood disasters efficiently. However, in case there are many available locations for washland and many combinations to consider, it is very difficult to determine the optimal combination which yields to provide the maximum benefit. For the more, hydraulic approach that used in previous studies to calculate flood reduction effect needs a lot of time for calculation and sometimes can not give the final result. In this study, the flood reduction effect of washland is calculated by hydrologic approach and decision making model for optimal location of washland using genetic algorithm for determination of optimal solution is developed. The developed model has been applied to the Ansung River basin in order to examine the applicability and the application result shows that developed model can be used as decision making model for washland.

• Ecology and Resilient Infrastructure
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• v.10 no.2
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• pp.40-49
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• 2023

To reduce the damage of extreme flooding caused by climate change and to create flood mitigation sections in a nature-friendly riparian area, it is necessary to restore the floodplain area by referring to the past floodplain section of the current inland waterfront area before the levee was built. This study proposed a method of selecting a location for floodplain restoration using old maps of the Geum River study section and analyzed the effect of flood level reduction through unsteady flow numerical simulations using the floodplain as a flood mitigation space. As a result of analyzing changes in the river areas using old maps, the river section was estimated to gradually reduce by 27.8% (1,059,380 m²) in 2020 compared to 1919, and it was found to have an effective storage capacity of 2,200,868 m³ when restored to offline storage. The flood level and discharge control effects analyzed based on HEC-RAS unsteady flow simulation were 16 cm and 219.01 m³/s, respectively, in the downstream cross-section. In the numerical simulation in this paper, the flood mitigation space was applied as an offline reservoir. The effect of reducing the flood level may differ if levee retreat/relocation is applied.

• Journal of Korea Water Resources Association
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• v.47 no.1
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• pp.83-93
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• 2014

This research was carried out for suggesting design criteria and procedure for maximizing flood control capacity by building flood control facilities like flood retention basin built in connection with existing facilities in order to cope with increased uncertainty due to factors such as urbanization and climate change. We suggested the procedure for the analysis under the various scenarios applicable for the cases of determining retention basin capacity as provision for the flood water level increase in main river channel or estimating flood water level reduction effect when retention basin capacity is given. Procedure for estimating design flood hydrograph at any duration using Intensity-Duration-Quantity (IDQ) originated from the existing IDF, and its application example were provided. Based on rainfall estimated by the IDQ analysis, it is possible to calculate an equivalent peak hydrographs under various scenarios, e.g. lower frequency hydrograph under same rainfall duration with water level higher than existing hydrograph, hydrograph with same peak and higher volume due to increased rainfall duration, hydrograph with higher peak and volume than existing hydrograph, etc.