• Journal of Korea Water Resources Association
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• v.40 no.5
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• pp.383-396
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• 2007

The studies on efficiency of flood control reservoir has been introduced into four categories including direct flood control contribution by reservoir, flow-duration change and environmental-ecological change in downstream of dam and flood damage estimation of flood plain. In spite of all the previous approaches, the quantification of the effect of reservoir on the flood control in planning stage is quite complex due to lack of a standard for quantifying feasibility of project. In this study, we develop a methodology that can clearly and accurately quantify the flood damage reduction together with the existing flood level reduction at downstream. The proposed approach uses three appraisal standards of flood control: 'potential safety', 'relative risk' and 'absolute risk' according to the risk by stage. The developed methodology was applied to the Namhan river basin with the storm event of July, 2006. The result shows the damage reduction of 4,189 billion won was estimated. The economic benefits for the flood control effect by dam will greatly contribute to the public understanding of the importance and the effect of the flood control by dam.

• Journal of Korea Water Resources Association
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• v.30 no.5
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• pp.527-537
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• 1997

Reliability, resiliency and vulnerability for the risk analysis are mathematically defined as the evaluation standard of risk level to characterize the risk which influences water resources management and optimal reservoir operations. Monthly inflows are synthetically generated by stochastic generation model for a long-term reservoir water budget analysis, and this method is applied to the Dae-Cheong Multipurpose Dam. As a result of study, reliability based on occurrence, time and quantity are derived respectively. Also resiliency, vulnerability and resiliency inc\dices are estimated to evaluate the performance of water supply on reservoir system, and their relationships are evaluated.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.3
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• pp.101-112
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• 2019

This study developed selection criteria of small-scales reservoirs, having under $300,000m^3$ storage capacity, for the Emergency Action Plan(EAP) establishment in order to reduce the disaster risks of the reservoir's failures. Those reservoirs are out of ranges of Korean EAP establishment standard, but have potential risk of disasters as they have often failed by the recent extreme rainfall events and earthquakes, causing economical and life losses. The problem of reservoir aging is also one of the reasons of them. In this study, the developed selection criteria of small reservoirs for EAP establishment are storage capacity, embankment height, reservoir age, heavy rain factor and earthquake factor. These criteria were selected based on the review of the existing EAP establishment guidelines, analysis of the past dam failure cases, and the previous related studies. The quantification of these criteria were conducted for the practical applications in the fields, and applied to 67 previous failures in order to investigate the relation of each criteria with these failures. The earthquake factor found to be the highest relations followed by heavy rain factors, combination of earthquake and heavy rain factors, and reservoir age. The classification was made as observation and review groups for EAP establishments based on overlapping numbers of each criteria. This classifications applied to 354 reservoirs designated as having the potential disaster risk by MOIS, and showed 38.4% of observation and 11.9% of review groups. Anticipatory monitoring and regular inspection should be made by professional facility managers for the observation group, and necessity of EAP establishment should be assessed for the review group based on the downstream status and financial budget.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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• pp.413-427
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• 2006

It is necessary to study and develop guidelines for providing comfort and health indoor air quality for office workers since air-tight envelope system of current office building may cause poor indoor air quality. The purpose of this study is to propose guideline for volatile organic compounds in office base on the field study, human health risk assessment and cost-benefit analysis. The field study was conducted to survey the concentrations of volatile organic compounds in indoor air of 69 offices from June to September, 2005 in Seoul and Gyeonggi-do. The rate of excess to guideline of volatile organic compounds in indoor air of new apartment on the Ministry of Environment in Korea(MOE) was surveyed 37.6% for benzene, 6.8% for toluene, and 1.5% for ethylbenzene. As the result of human health risk assessment, mean cancer risk did not exceed 10-6 which is guideline of US.EPA. Also, total hazard index did not exceed 1 which is guideline of US.EPA. Through the cost-benefit analysis of angle on the social-economics to verify the necessary to establish the standards of volatile organic compounds for improvement and development of indoor air quality in office, the present value of benefit was higher than the present value of cost. With the above considerations in mind, it is suggested that the field study for indoor air quality in offices should be expanded and human health risk assessment and cost-benefit analysis be performed th offer scientific data for decision-making of policy for improvement and management of indoor air quality in office.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.5
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• pp.67-73
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• 2010

Relatively high density of population and buildings exists in urban area mainly because of broad job opportunities and conveniences available. In other words, if happened, there might be high possibility of disaster which can not be easily recovered. The purpose of this study is to show evaluation approach of the risk degree resulted from the disaster, which considers the attributes of urban area. Cheongju-city in Chungcheongbuk-do is selected as sample district to be estimated. The degree of overall risk including fire risk, building collapse risk, evacuation risk and gas explosion risk etc. is analyzed in the designated area. The analysis suggests the highest risk degree in Bukmun-ro district which also shows CBD decline phenomenon. Therefore, it can be not only predicted that this area as old downtown has not been provided with disaster prevention operation and urban renewal project, but also judged that administrative assistances for the disaster are required possibly soon.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.5
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• pp.49-62
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• 2021

The objective of this study was to evaluate the flood control capacity of the agricultural reservoir based on state-of-the-art climate change scenario - SSP (Shared Socioeconomic Pathways). 18 agricultural reservoirs were selected as the study sites, and future rainfall data based on SSP scenario provided by CMIP6 (Coupled Model Intercomparison Project 6) was applied to analyze the impact of climate change. The frequency analysis module, the rainfall-runoff module, the reservoir operation module, and their linkage system were built and applied to simulate probable rainfall, maximum inflow, maximum outflow, and maximum water level of the reservoirs. And the maximum values were compared with the design values, such as design flood of reservoirs, design flood of direct downstream, and top of dam elevation, respectively. According to whether or not the maximum values exceed each design value, cases were divided into eight categories; I-O-H, I-O, I-H, I, O-H, O, H, X. Probable rainfall (200-yr frequency, 12-h duration) for observed data (1973~2020) was a maximum of 445.2 mm and increased to 619.1~1,359.7 mm in the future (2011~2100). For the present, 61.1% of the reservoirs corresponded to I-O, which means the reservoirs have sufficient capacity to discharge large inflow; however, there is a risk of overflowing downstream due to excessive outflow. For the future, six reservoirs (Idong, Baekgok, Yedang, Tapjung, Naju, Jangsung) were changed from I-O to I-O-H, which means inflow increases beyond the discharge capacity due to climate change, and there is a risk of collapse due to dam overflow.

• Journal of Korea Water Resources Association
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• v.42 no.8
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• pp.591-605
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• 2009

In this study the risk integrated erosion and seepage failure factor and combined risk of the levee embankment were assessed. For the research of the reliability, the risk assessment of erosion, seepage and both of them combined for the levee embankment were conducted using discharge curve and stage hydrograph generated by stochastic rainfall variation method during typhoon and monsoon season. The risk of erosion was evaluated using tractive force and the seepage analysis was performed by selecting representative cross sections for SEEP/W model analysis. And the probability of seepage failure was assessed with MFOSM analysis using critical hydraulic gradient method. Unlike deterministic analysis method, quantitative risk could be obtained and the characteristics of realistic rainfall variation patterns as well as a variety of factors contributing to levee failure could be reflected in this research. The results of this study show significantly enhanced applicability for the combined risk. As this model can be employed to determine dangerous spots for levee failure and to establish flood insurance linked with flood risk map, it will dramatically contribute to the establishment of both efficient and systematic measures for integrated flood management on a watershed.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.149-156
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• 2019

Assessing the hydrological safety of existing dams against climate change and providing appropriate adaptation measures are important in terms of sustainable water supply and management. Korean major dams ensure their safety through periodic inspections and maintenance according to 'Special Act on the safety control and maintenance of establishments'. Especially when performing a full safety examination, principal engineer must assess the hydrological safety and prepare for potential risks. This study employed future probable maximum precipitation (PMP) estimated using outputs of regional climate models based on RCP4.5 and RCP8.5 greenhouse-gas emission scenarios to assess climate change impact on existing dam's future hydrological safety. The analysis period was selected from 2011 to 2040, from 2041 to 2070, and from 2071 to 2100. Evaluating the potential risk based on the future probable maximum flood (PMF) for four major dams (A, B, C, I) showed that climate change could induce increasing the overflow risk on three dams (A, B, I), although there are small differences depending on the RCP scenarios and the analysis periods. Our results suggested that dam managers should consider both non-structural measures and structural measures to adapt to the expected climate change.

• Journal of Environmental Impact Assessment
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• v.20 no.2
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• pp.227-234
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• 2011

In the study, CE-QUAL-W2 was used and its examination and correction were conducted targeting 2001 and 2003 when the condition of rainfall was contradicted. Using the proved model in 2003, a scenario was implemented with management of locations for dewatering outlets and actual data for dam management in 1987 when inflow and outflow level were almost same. In case of the scenario which the location of dewatering outlets was 5m higher than usual location, exclusion efficiency for turbid water inflow at the beginning of precipitation was good. In case of the scenario which the location of dewatering outlets was 10m lower than usual location, exclusion efficiency for excluding turbid water remained in a reservoir after the end of precipitation. However, the scenario applying dam management data in 1987, exclusion efficiency was relatively low. In the scenario, power-generating water release spot at EL.57m for first four days after the beginning of precipitation, EL.52m for 5th to 8th and EL.42m from 9th days. An analysis of the scenario reveals that both excessive days exceeded 30 NTU and average turbidity levels were decreased comparing before and after the alteration on outlets. The average turbidity levels were decreased by minimum of 55% to maximum of 70% and 30NTU exceeding days were decreased by 45 days at maximum. Also, since it could exclude most of turbid water in a reservoir before the destatifcation, the risk for turbid water evenly distributed in a reservoir along with turn-over could be decreased as well.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.458-461
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• 2006

Early age cracking of concrete is a widespread and complicated problem, and diverse applications in practical engineering have focused on this issue. Since massive concrete base slab composes the infrastructure of other concrete structures such as pier, concrete dam, and high rise buildings, early age cracking of that is considered as a crucial problem. In this study, finite element analysis (FEA) implemented with the age-dependent microplane model was performed. For a massive concrete base slab, cracking initiation and propagation, and deformation variation were investigated with concrete age. In massive concrete slab, autogenous shrinkage increases the risk of early age cracking and it reduces reinforcement effect on control of early age cracking. Gradual crack occurrence is experienced from exterior surface towards interior of the slab in case of combined hydration heat and autogenous shrinkage. FEA implemented with enhanced microplane model successfully simulates the typical cracking patterns due to edge restraint in concrete base slab.