• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.98-98
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• 2016

본 연구에서는 유입량의 불확실성을 고려하여 미래 저수량을 확률론적으로 예측하였다. 월별 유입량을 표본으로 한 확률밀도함수를 핵밀도함수(kernel function)를 이용하여 추정하고, 추정된 확률분포로 월별 유입량을 모의 발생하였다. 모의 발생된 유입량을 통해 연속적인 조건부 확률을 산정하였고, 이의 누적확률분포(F(x))는 해당 저수량에 도달하지 못할 확률, 즉 실패확률을 의미하므로 1-F(x)로 해당 저수량 이상을 확보할 수 있는 확률을 산정하였다. 보령댐을 대상으로 분석한 결과 2016년 2월 말 저수량 27.8 백만$m^3$ 기준으로 3월부터 6월까지 정상용수공급환원 기준 저수량을 만족할 확률이 각각 2.3%, 12.5%, 24.2%, 33.5%로 나타났다. 지역적 가뭄에 대응하기 위해 하천유지용수 감량, 용수 대체공급, 자율 급수조정 및 금강-보령댐 도수로를 이용한 용수공급으로 20.6만$m^3/day$의 용수가 비축될 경우, 정상용수공급환원 기준 저수량을 만족할 확률이 10.2%, 40.3%, 73.8%, 78.7%로 용수비축의 효과가 크게 나타나는 것을 확인하였다. 저수량의 확률론적 예측을 통해 미래 저수량의 확률적 발생가능성을 추정할 수 있으며, 가뭄이 발생할 경우, 가뭄 대응효과를 정량적으로 나타낼 수 있어 가뭄 위험 상황 전달 및 용수공급조정 의사결정 시 활용할 수 있을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.37-37
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• 2016

기후변화는 댐유입량의 시공간적 변화를 야기할 것으로 전망된다. 따라서 기후변화에 따른 댐 유입량의 영향을 정량적으로 평가하고 그에 적응할 수 있는 댐 운영 방안이 필요하지만 영향평가 시 많은 불확실성이 발생하기 때문에 불확실성을 정량적으로 평가할 수 있는 기술 개발이 요구된다. 본 연구에서는 기후변화에 따른 댐 유입량 전망 시 발생하는 불확실성을 평가 단계별로 분해할 수 있는 기법을 이용하여 계절별 댐 유입량 전망 결과의 불확실성을 평가하였다. 이를 위해 현재 국내에서 가용한 CORDEX East Asia에서 제공하고 있는 5개 RCM 결과를 이용하였으며, 5가지 통계적 후처리기법, 2가지 수문모형을 이용하였다. 대상지역은 충주댐 유역으로 선정하였으며, 계절 댐 유입량에 대한 과거기간 대비 미래기간의 전망 결과에 대해 분석하였다. 평가결과, 겨울철을 제외한 모든 계절에서 RCM이 29.3~68.9%로 가장 큰 비중을 차지하는 것으로 나타났으며, 겨울철은 수문모형이 46.5%를 차지하는 것으로 나타났다. 이는 홍수기의 댐 유입량은 강수량에 직접적인 영향을 받으나 이수기에는 강수량 이외에 그 당시의 토양상태, 기후환경 등의 영향에 따른 수문순환 전반적인 영향이 물가용성에 영향을 미친다. 따라서 이수기는 수문모형에 더욱 영향이 큰 것으로 나타났으며, 홍수기는 기후 모델링 부분의 영향이 큰 것으로 사료된다. 이러한 분석을 통해 특정 RCM이나 통계적 후처리기법, 수문모형 등의 선정에 따라 전체 불확실성에 미치는 영향을 분석할 수 있으며, 이를 통해 불확실성을 저감할 수 있는 방안을 마련할 수 있을 것으로 기대된다.

• Journal of Korea Water Resources Association
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• v.47 no.10
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• pp.853-865
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• 2014

Hydrologic dam risk analysis depends on complex hydrologic analyses in that probabilistic relationship need to be established to quantify various uncertainties associated modeling process and inputs. However, the systematic approaches to uncertainty analysis for hydrologic risk analysis have not been addressed yet. In this paper, two major innovations are introduced to address this situation. The first is the use of a Hierarchical Bayesian model based regional frequency analysis to better convey uncertainties associated with the parameters of probability density function to the dam risk analysis. The second is the use of Bayesian model coupled HEC-1 rainfall-runoff model to estimate posterior distributions of the model parameters. A reservoir routing analysis with the existing operation rule was performed to convert the inflow scenarios into water surface level scenarios. Performance functions for dam risk model was finally employed to estimate hydrologic dam risk analysis. An application to the Dam in South Korea illustrates how the proposed approach can lead to potentially reliable estimates of dam safety, and an assessment of their sensitivity to the initial water surface level.

• Journal of Korea Water Resources Association
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• v.44 no.10
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• pp.843-851
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• 2011

In hydrology, it is appropriate to use probabilistic method for forecasting mid/long term streamflow due to the uncertainty of input data. Through this study, it is expanded mid/long term forecasting system more effectively adding priory process function based on PDF-ratio method to the RRFS-ESP system for Guem River Basin. For implementing this purpose, weight is estimated using probabilistic weather forecasting information from KMA. Based on these results, ESP probability is updated per scenario. Through the estimated result per method, the average forecast score using ESP method is higher than that of naive forecasting and it confirmed that ESP method results in appropriate score for RRFS-ESP system. It is also shown that the score of ESP method applying revised inflow scenario using probabilistic weather forecasting is higher than that of ESP method. As a results, it will be improved the accuracy of forecasting using probabilistic weather forecasting.

• Journal of Korea Water Resources Association
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• v.38 no.9 s.158
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• pp.761-770
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• 2005

This study applied the fuzzy logic control for the construction of the reservoir operation model which can consider uncertainty of the predicted inflow in determining reservoir release during flood period. The control rule is usually constructed based on the opinion of experts which is a general technique. To improve the drawback of general technique, this study constructed the Fuzzy-Tabu search model automatically established by the fuzzy rule using Tabu search which is a global optimization technique. As the results, the peak release is decreased and the flood control efficiency is improved. The total release is also decreased and this represents the benefit in water use. Consequently, it is confirmed that the effect of flood control can be increased through the constructed model. It also shows that the available water resources after the flood is more increased. So, the proposed Fuzzy-Tabu search model could be better than the actual reservoir operation methodology in the aspect of water use.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.1-15
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• 2008

Recently, because of the various factors by uncertainty of underground, the risks in tunnelling have been occurred increasingly. Therefore, it is very important to estimate and control the risks considering geotechnical conditions for tunnel stability and environmental problems by tunnel construction. In this study, the risk analysis for tunnel stability was carried out by classifying the risk factors such as ground support capacity, ground settlement, the inflow of groundwater into the tunnel and the damage by the earthquake. Also, the risk assessment for the environmental problems was performed by calculating the vibration and noise by blasting and the drawdown of the groundwater level caused by tunnel construction. Each risk factor was evaluated quantitatively based on the probabilistic and statistic technique, then it was analyzed the distribution characteristic along overall tunnel site. Finally, it was evaluated that how much each risk factor influences on the construction cost with a period for tunnel construction, so it is possible to perform reasonable tunnel design which was capable of minimizing the risks in the tunnel construction.

• Journal of Korea Water Resources Association
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• v.57 no.4
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• pp.249-261
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• 2024

Climate change has intensified the severity of extreme floods, presenting substantial challenges to dam management and operation. Traditionally, flood control strategies for dam operations have been based on theoretical scenarios, such as designed floods, without taking into account downstream conditions. However, in practice, managing floods involves operating dams based on climate forecasts. This strategy encounters challenges due to the limited predictability of climate forecasts, which in turn leads to uncertainty in decisionmaking among dam managers. This study proposes a flood control approach for dam operations that involves gradually increasing the outflow, considering the operational constraints and potential downstream damage, based on inflow data. The effectiveness of this method was assessed through simulation, employing both a designed flood and data from the most significant historical flood. The dam operation strategy for flood control presented in this study provides a framework for dam operators, facilitating consistent decisionmaking in flood management by integrating realistic dam operational conditions.

• 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.56 no.6
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• pp.419-429
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• 2023

The objective of this study was to determine the management water level of an estuary reservoir considering three aspects: the water use, flood control and water quality, and to use a robust decision-making to consider uncertainty due to climate change. The watershed-reservoir linkage model was used to simulate changes in inflow due to climate change, and changes in reservoir water level and water quality. Five management level alternatives ranging from -1.7 El.m to 0.2 El.m were evaluated under the SSP1, 2, 3, and 5 scenariosof the ACCESS-CM2 Global Climate Model. Performance indicators based on period-reliability were calculated for robust decision-making considering the three aspects, and regret was used as a decision indicator to identify the alternatives with the minimum maximum regret. Flood control failure increased as the management level increased, while the probability of water use failure increased as the management level decreased. The highest number of failures occurred under the SSP5 scenario. In the water quality sector, the change in water quality was relatively small with an increase in the management level due to the increase in reservoir volume. Conversely, a decrease in the management level resulted in a more significant change in water quality. In the study area, the estuary reservoir was found to be problematic when the change in water quality was small, resulting in more failures.