• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5B
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• pp.415-429
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• 2011

Quantitative evaluation indexes for flood control effect of a multi-purpose reservoir used widely in Korea are the discharge control rate, reservoir release rate, reservoir storage rate, and flood control storage utilization rate. Because these indexes usually use and compare inflow, release, and storage data directly, the uncertainties included in these data are not considered in evaluation process, and the downstream flood control effects are not assessed properly. Also, since the acceptable partial failure in a design of water resources system is not considered, the development of a new flood control effect evaluation index is required. Fuzzy set theory is therefore applied to the development of the index in order to consider the data uncertainty, the downstream flood control effect, and the acceptable partial failure. In this study, the flood control effect of a multi-purpose reservoir is evaluated using the flood control effect index developed by applying fuzzy set theory. The Chungju reservoir basin was selected as a study basin and the storm events of July, 2006 are used to study the applicability of the developed index. The related factors for flood control effect are fuzzified, the acceptable failure region is divided from the system state to evaluate the flood control effect using developed flood control effect index. The flood control effect index were calculated by applying to the study basin and storm events. The results show that the developed index can represent the flood control effect of a reservoir more realistically and objectively than the existing index.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.559-569
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• 2009

Due to environmental, economical and the other limitations, it has been more difficult to construct new large hydraulic structure such as dam. For this reason, it has been tried to use small hydraulic structure such as washland as alternative of hydraulic facility. Because the flood control effect of small hydraulic structure are affected by runoff volume, hydrograph, storage capacity and weir crest elevation, and design frequency must be predetermined for the design of the hydraulic structure. Multiple washlands will be required to satisfy enough peak reduction effect so that considering washlands as a network, rather than individually, are critical to analysis of flood reduction effect. In this study, new index for determination of optimal location for washlands is presented and the existing model for this determination is modified by adopting the new index. Developed new model is applied to Ansung river basin for examination and the new model shows its' applicability as a decision making criteria for the determination of optimal location for washlands.

• Journal of Wetlands Research
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• v.18 no.2
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• pp.154-165
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• 2016

Recently, the frequency of extreme rainfall event has increased due to climate change and impermeable area also has increased due to rapid urbanization. Therefore, we ought to prepare countermeasures for flood reduction to reduce the damage. To consider climate change, the frequency based rainfall was calculated according to the aimed period(reference : 1971~2010, Target period I : 2011~2040, Target period II : 2041~2070, Target period III : 2071~2100) and the flood discharge was also calculated by climate change using HEC-HMS model. Also, the flood elevation was calculated by each alternative through HEC-RAS model, setting 5 sizes of drainage pumps and reservoirs respectively. The flood map was constructed using topographical data and flood elevation, and the economic analysis was conducted for reduction of flood damage using Multi dimension - Flood Damage Analysis, MD-FDA. As a result of the analysis on the flood control effect, a head of drainage pump was reduced by 0.06m up to 0.44m while it was reduced by 0.01m up to 1.86m in the case of a detention pond. The flooded area shrunk by up to 32.64% from 0.3% and inundation depth also dropped. As a result of a comparison of the Benefit/Cost index estimated by the economic analysis, detention pond E in period I and pump D in period II and III were deemed appropriate as an alternative for climate change. The results are expected to be used as good practices when implementing the flood control works considering climate change.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.516-520
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• 2004

Stream Naturalness means the index of natural state in stream's ecosystem. The evaluation of stream naturalness can evaluate relatively the effect of environmental damages by human and to show how significantly current stream has been apart from its natural state. And it could be show what is the meaning of importance in stream's ecosystem by such distinctions and it Is done by showing the need how a large scale of action for restoration to be restored to natural state of stream system. In this study, a set of index for Stream Naturalness evaluation is proposed, which is referred to and modified problems with domestic and foreign study cases. This methodology is supposed to show well the characteristics of stream in Korea. A case study of Hong-Chun River shows how this methodology is applied to the Stream Naturalness evaluation. For improving the function of river which are water use and flood control and for preserving the function of inhabitation, the proposed methodology is expected to be used a index of direction for a environmental project related stream improvement by evaluation of ecologically sound function in streams.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.312-316
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• 2010

현재 국내에서 주로 사용되고 있는 홍수기 다목적 댐의 홍수조절효과에 대한 정량적인 평가지표로는 유량조절률, 저수지 방류율, 저수지 저류율, 저수지 이용률 등이 있다. 이러한 평가지표들은 유입량, 방류량, 저류량 등의 자료를 단순 비교하는 방법을 사용하고 있는데, 홍수조절효과 평가지표 산정식에 사용되는 자료들이 가지는 불확실성이 평가에 고려되지 못하고 있으며, 다목적댐에서 얻을 수 있는 자료만을 사용함으로써 댐 하류 지점에서의 홍수조절효과를 평가하지 못하고 있다. 또한 수자원 시스템의 설계에 있어서 허용 가능한 부분적인 실패를 고려하지 못하는 등의 문제점이 존재하므로, 홍수조절효과를 정량화 할 수 있는 새로운 지표의 개발이 요구된다. 본 연구에서는 각종 변수들이 가지는 불확실성, 댐 하류지점에서의 홍수조절효과, 수자원 시스템에서 허용 가능한 부분적 실패를 고려하기 위하여 홍수조절효과 정량화 지표 개발에 퍼지집합 이론을 적용하였고, 충주댐 유역을 시험 유역으로 선정하여 연구를 수행하였다. 대상 홍수사상으로는 2006년도 7월의 홍수사상을 적용하였으며 그에 따른 인자들을 퍼지화하고 시스템의 상태로부터 허용 가능한 부분적인 실패 영역을 구분하였고, 통합 신뢰도-취약도 지수를 적용하여 홍수조절효과 정량화 지표를 개발하였다. 적용 결과, 본 연구를 통하여 개발된 통합 신뢰도-취약도 지수는 저수지의 홍수조절효과를 보다 구체적이고 객관화하여 나타낼 수 있었다.

• Journal of Korea Water Resources Association
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• v.45 no.9
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• pp.887-900
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• 2012

Drought is a non-negligible disaster of nature and it is mainly caused by rainfall shortage for a long time though there are many definitions of drought. 'Standard Precipitation Index' (SPI) that is widely used to express the level of meteorological drought intensity has a limit of not being able to consider the hydrological changes such as rainfall and evapotranspiration caused by climate change, because it does not consider the temperature-related variables other than the precipitation. Recently, however, 'Standardized Precipitation Evapotranspiration Index' (SPEI), a drought index of new concept which is similar to SPI but can reflect the effect of temperature variability as well as the rainfall change caused by climate variation, was developed. In this study, the changes of drought occurrence in South Korea were analyzed by applying SPEI for meteorological data (1973~2011) of 60 climate observatories under Korea Meteorological Administration (KMA). As the result of application, both of SPI and SPEI showed the trend of deepening drought in spring and winter and mitigating drought in summer for the entire nation, with SPI showing greater drought intensity than SPI. Also, SPI and SPEI with 12 months of duration showed that severe droughts with low frequency of around 6 years are generally being repeated.

• Journal of Convergence for Information Technology
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• v.10 no.10
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• pp.128-134
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• 2020

Recently, the damages by typhoons and heavy rains are increasing due to the climate change. However, we are still vulnerable to inundation disaster due to various causes such as poor physical flood control and lacks of disaster and safety management. Therefore, it is necessary to establish systems to ensure safety and prepare practical countermeasures that can minimize damage when an inundation occurs, thereby minimizing economic loss and casualty. In this study, hydrodynamic inundation modelings were implemented to analyze the "Noryangjin reservoir inundation accident" and "Choryang No. 1 underground road inundation accident." and spatial risk was assessed by a quantitative hazard index. In addition, cause and effect diagrams were provided to present the risk causes in terms of physical and managemental aspects.

• Journal of Wetlands Research
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• v.12 no.3
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• pp.1-13
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• 2010

Most of investigations about the effects of dam construction on the surrounding environments have focused mainly on the change of climate conditions and crop production. In order to research the effect of dam construction on the surrounding vegetation, we chose the Soyanggang dam whose storage capacity is the largest in Korea, and was built 33 years ago. We surveyed and analyzed the surrounding vegetation by using quadrat method and measured the soil moisture content among floodplain (FP), 5m above the flood plain (AFP) and control group (CG) which is 3km far from the lake through ridge. The largest value of mean importance percentage of the canopy~understory layer at FP was Salix koreensis (87.9%) and those of AFP and CG was Quercus mongolica (38.9% and 40.4% respectively) and the largest important percentage of the herb layer at FP was Artemisia capillaris (34.2%) and those of AFP and CG was Oplismenus undulatifolius var. undulatifolius (9.4% and 24.6% respectively). The Shannon-Wiener diversity index of shrub~canopy layer at FP (0.26) was lower than AFP (2.34) and CG (2.23) and there was not any significant difference in the herb layer among three groups. The S${\o}$rensen similarity index between FP and AFP, FP and CG was 0, and that of AFP and CG was relatively high. The highest density of tree and subtree with the DBH level of FP was S. koreensis of 5~10cm (240/ha), and that of AFP and CG was Quercus spp. of 15~20cm (400/ha and 466/ha respectively). And the highest density of seedlings of FP was Pinus densiflora (7,040/ha), and that of AFP and CG was Quercus spp. (720/ha and 400/ha respectively). The soil water content of FP (6.28%) was relatively lower than AFP and CG (11.13% and 10.14% respectively; p<.01). These results indicated that construction of Soyanggang dam changed the vegetation of the floodplain, without showing a change in its upland areas.