• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.275-275
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• 2020

홍수빈도분석의 실용적 측면의 목적은 특정 재현기간에 대하여 발생 가능한 홍수량을 설계홍수량(design flood)으로 설정함으로써 댐, 제방, 배수시설, 하수관거 등의 치수기능을 가진 치수시설물이 설계홍수량 내에서 홍수로 인한 피해를 발생시키지 않도록 그 규모와 기능을 설계함에 있다. 이와 같은 중요한 기능을 담고 있는 홍수빈도분석의 기술적 절차는 해외 및 국내의 기존 연구자들에 의해 많은 연구가 진행된 바 있으나, 보다 적절한 설계홍수량 산정절차 및 설계홍수량의 최종 결정을 위한 기술적 수단의 제공을 위한 연구가 많은 연구자들에 의해 지금도 진행 중에 있다. 그러나 이와 같이 결정된 설계홍수량이 특정유역에서 발생될 수 있는 피해규모에 대해 얼마나 적정한 지의 여부를 과학적으로 판단하기 위한 연구는 많지 않다. 따라서 본 연구에서는 홍수빈도분석을 통해 산정된 설계홍수량의 적정성 여부를 과학적으로 판단하기 위해 비용-편익분석 기법을 이용하여 최적설계홍수량을 결정하였다. 특히 본 연구에서는 불확실성으로 발생되는 범위를 고려한 최적설계홍수량을 산정하기 위하여 Metropolis-Hastings 알고리즘을 사용하였으며, 자료의 종류에 따른 홍수량의 변화를 분석하기 위하여 년최대계열 및 부분시계열 자료를 각각 적용하였다. 한강유역에서 가평대성, 여주 및 한강대교 수위표 지점에서 측정된 자동관측유량장치에 의한 홍수량 자료를 활용하였으며, 최적설계홍수량이 기존 설계홍수량에 비해 크게 산정됨을 알 수 있었다.

• Journal of Korea Water Resources Association
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• v.52 no.6
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• pp.411-420
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• 2019

The objective of this study is to evaluate the appropriateness of methodology for designing urban sewer system using a rational method-based model, Makesw and an urban runoff model, SWMM. The Gunja basin was selected as a study area and precipitation, runoff, vegetation, soil, imperviousness data were used to estimate floods. The appropriateness of methodology was evaluated based on comparison analysis between floods estimated from Makesw and SWMM. The comparison analysis was conducted between floods estimated from Makesw and SWMM, which were simulated using design rainfall and measured rainfall from past inundation events. The comparison results showed that in the case of design rainfall, the rational method-based floods were larger than that based on SWMM in all main lines. However in several branch lines, the rational method-based floods were smaller than thoes based on SWMM. In addition, for the case of measured rainfall from past inundation events, it was easily to find the main and branch lines where the rational method-based floods were smaller than SWMM based ones. Especially, the lines where rational method-based floods were underestimated, were mostly main, $1^{st}$, $2^{nd}$ lines. It was concluded that the rational method-based results were not conservative. Based on rational method (steady flow analysis) and SWMM (unsteady flow analysis), the more conservative results the method provides, the more highly it is recommended to use in designing an urban sewer system.

• Solar Energy
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• v.18 no.2
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• pp.91-104
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• 1998

This study carried out a numerical analysis on a heat pump assisted dryer using HFC134a. Under the constant degree of superheat and that of subcooling, we analyzed the performance of heat pump assisted dryer with varying an air mass velocity, bypass air ratio, compressor speed and an inlet bulb temperature of dryer. Simulation results were compared with experimental results, so they were maximally agreed in the range of 10%. There was the proper bypass air ratio with varying an air mass velocity. As for the effect of SMER having the inlet temperature $35^{\circ}C$ and compressor speed 1360rpm, bypass air ratio was 30% at the front velocity 0.5kg/s, 40% at the front velocity 0.7kg/s and 50% at the front velocity 0.9kg/s and 1.1kg/s. As the compressor speed was increased, SMER decreased and COP increased. As the inlet bulb temperature was increased, SMER and COP decreased.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.469-469
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• 2021

낙동강을 취수원으로 사용하고 있는 국민들은 과거부터 꾸준히 발생해온 수질사고로 인하여 낙동강 수질에 대한 관심이 매우 높다. 이에 낙동강 본류를 취수원으로 이용하고 있는 중·하류 지방자치단체들은 낙동강 유역 내 댐이나 상류로의 취수원 이전을 요구하고 있다. 이러한 요구들은 지역·지방간의 갈등이 유발되었으며 가장 대표적인 사례가 부산광역시의 취수원 이전 문제이다. 부산광역시는 낙동강 본류 수질 악화와 녹조발생으로 인한 원수에 대한 시민들의 불신, 수질 악화로 인한 정수비용 증가 등의 문제를 제기하였고 이를 해결하고자 남강 상류 또는 낙동강 지류로 취수원 이전하여 시민들에게 상수 공급하기를 원하고 있다. 하지만 타 지방자치단체와의 이해, 경제성 등의 문제로 마찰을 빚고 있다. 지역간의 갈등을 최소화하면서 적정 수량 확보가 가능한 대체 수자원 확보를 위해 강변여과수, 지하수저류지, 인공함양, 인공습지, 해수담수화 같은 방법들이 논의 되었지만 본 연구에서는 낙동강 중·하류에 인공습지 적용이 가능한 지점들을 선정하고 목표 유량 및 수질 확보 가능성을 평가하였다. 기 연구된 경남, 부산권 광역상수도 사업 타당성 조사(2011, 국토교통부)에 의하면 낙동강 하류지역에 안전한 상수원 확보를 위한 원수 대체 필요량은 전체 약 1,330,000 m³/day 이다. 이를 확보하기 위해 강정고령보 상류 ~ 창녕함안보 하류구간 내 21개의 인공습지 후보지를 선정하고 유량확보 가능량, 수질, 오염부하량, 조류, 공간확보 항목에 대하여 평가하였다. 그 결과 21개 후보지에 대해 유량확보, 수질, 조류 항목에 대한 평가 결과 큰 차이가 없었지만 오염부하량과 공간확보 항목에 대한 평가 결과가 인공습지 후보지 선정에 영향을 미치는 것으로 분석 되었다. 향후 낙동강 중·하류에 인공습지를 활용한 취수원 개발을 위해서는 낙동강 본류와 지류에 대한 정확한 수질 조사와 인공습지 후보지에 대한 면적조사, 경제성 평가가 수행되어야 할 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.250-254
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• 2005

국내의 상수원수 확보는 대부분을 표류수에 의존하고 있으나, 표류수의 경우 수질오염의 증가와 돌발 수질 오염 사고에 대한 대응 등의 취약점을 가지고 있다. 이러한 문제점을 해결하기 위해 근본적으로 깨끗한 상수원수를 확보하기 다양한 방법이 모색되어지고 있다. 수량적으로 안정적이고, 수질적으로 안전한 상수원수 취득 방법으로 강변여과수, 지하댐, 인공함양기법 등이 실질적으로 계획되어 시행되어지고 있다. 특히 강변 충적층의 자연정화 기능을 이용한 강변여과수 개발은 지하수 개발과 달리 수량적으로 안정적이고, 수질적으로 안전한 강변여과수 개발 방안이 적극적으로 진행되고 있다. 낙동강 하류 지역인 함안군, 창원시, 김해시 등은 대부분 하천 표류수에 의존하였으나, 유역내 충적층 발달 지역이 분포해 있고, 하상경사, 하상계수 등의 하천공학적 측면에서 강변여과수 개발에 유리한 입지조건을 가지고 있어 강변여과수 개발이 진행되고 있다. 현재 창원시 대산면 일대에서 국내최초로 방사형집수정을 이용한 강변여과수 개발이 진행되고 있으며, 현재 방사형 취수정 1기가 시공 완료되어 시험 가동 중에 있다. 본 연구에서는 창원시 대산면 일대에서 진행되고 있는 방사형 집수정 설치에 따른 양수시험을 실시하여 양수량에 따른 수위하강 겋항 등을 분석하여 적정 산출량을 결정하였고, 계획단계에서 적정 산출량 예상시 사용한 경험식(Petrovic, Milojevic 경험식)의 적합성 여부에 중점을 두어 진행 되었다. 연구대상 지역인 창원시 대산면 일대는 지하수위가 하천수위보다 높은 이득하천의 형태로 건기시 하천특성을 뚜렷하며, 양수실험을 위한 대용량 양수펌프 설치, 유량검증을 위한 대형 웨어 설치, 수위변화 측정을 위한 디지털 수위계 등을 설치하여 실험을 수행하였다. 단계/장기양수시험을 통하여 양수량-수위하강 경향을 분석하여 방사형 집수정 1기의 적정 양수량은 약 $16,000m^3/day$로 예상하였으며, 계획 시 사용한 경험식(Milojevic)으로 산정된 산출예상량과 유사한 특성을 나타내었다.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.821-826
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• 2013

The purposes of this research are to study on optimal distance between positive and negative electrodes in dust removal chamber. The experiments were performed with electrode-plate gab arranging in order of 3 cm, 2 cm, 1 cm in series while varying influent flow-rate. From the experimental results of dust removal the optimal influent linear velocity was 6 cm/sec and the total mass of attached dust on the surface of electrode-plate was increased as electrode-plate gab is closer. But in case of electrode-plate gab being very close about 1 cm or so, the attached dust on the surface of electrode-plate was shown releasing from electrode-plate due to dust electric-charge changing (reverse ionization). Evantually. optimal distance between positive and negative electrode-plates was about 2 cm and also optimal dust loading rate was about $24mg/min{\cdot}m^2$.

• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1251-1260
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• 2022

Recently, due to the deterioration of watermains and the detachment of scale which is accumulated on the watermain surface, water quality accidents in a water supply network occur frequently. As scale accumulated on watermains is stabilized, it may not cause water quality accidents under the normal operating condition. However, due to water hammer or transient flow caused by the abrupt velocity and/or direction of flow change, it can be detached from the watermain surface resulting in water quality accidents. To prevent these kinds of water quality accidents, it is required to remove scale by watermain cleaning regularly. Many researches about flushing which is the most popular water cleaning method are focused on the desirable velocity criteria and the cleaning condition to accomplish the effect of flushing whereas less amount of research effort is given to develop a method to consider whether the desirable velocity for flushing can be obtained before flushing is performed. During flushing, the major and minor headloss is occurred when flushing water flows through a hydrant or drain valve. These headloss may slow down the velocity of flushing water so that it can reduce the flushing effect. Thus, in this study, we suggest a method to simulate the flow velocity of flushing water using "MinorLoss Coefficient" and "Emitter Coefficient" in EPANET. The suggested method is applied to a sample network and the water supply network of "A" city in Korea to compare the flushing effect between "flushing through a hydrant" and "flushing through a drain valve". In case of "flushing through a hydrant", if the hydraulic condition ocurring from a watermain pipe connecting to the inlet pipe of a hydrant to the outlet of a hydrant is not considered, the actual flowrate and velocity of a flow is less than the simulated flowrate and velocity of a flow. In case of "flushing through a drain valve", the flushing velocity and flowrate can be easily simulated and the difference between the simulated and the actual velocity and flowrate is not significant. Also, "flushing through a drain valve" is very effective to flushing a long-length pipe section because of its efficiency to obtain the flushing velocity. However, the number and location of a drain valve is limited compared to a hydrant so that "flushing through a drain valve" has a limited application in the field. For this reason, the engineer should consider various field conditions to come up with a proper flushing plan.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.465-480
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• 2003

The interception capabilities of storm water grate inlet were analyzed in this paper. The hydraulic model lot gutter flow was used to estimate the interception capability. With the consideration of width and length of road, gutter discharges were ranged of 4-15l/sec. The transverse slopes of gutter were selected 4, 7 and 10%. The longitudinal slopes were 0, 2, 5 and 7%. The four sizes of storm water grate inlet were used in this experiments ($30\times40cm,\;40\times50cm,\;40\times100cm,\;40\times150cm$). The total number of experimental cases were 240. As the transverse slopes of gutter increased, the interception capability also increased. As the flow width in gutter and the discharge were lower, the interception efficiencies increased and the longitudinal slopes of road increased, the interception efficiencies decreased. The empirical formula with the factors of total inflow discharge, the longitudinal slope and the transverse slope of gutter were derived. These equations could be used to estimate the intercepting discharge of grate inlet. The reasonable construction space of grate inlet for the road widths, the longitudinal slopes, the transverse slopes and the grate inlet sizes were suggested.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.1-8
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• 2019

River works for water utilization have substantially altered the natural flow regime, and it has resulted in deformation of healthy river ecosystems. In Korea, river restoration projects have conducted actively since 1990's. Major purposes of the river restoration are the rehabilitation of modified river channel, improvement of water quality, and creation of aquatic habitats as well as recreational spaces using natural material for river work. However, there have been little interests about the restoration of flow regime which influences to most aspects of river ecosystems. The restoration of natural flow regime has received much attention in preservation of aquatic ecosystems. It should be needed to explore the relationship between flow regime and river ecosystems, and the restoring flow regime is essential. This paper introduce the concept of environmental flow through the interrelation between flow regime and river ecosystem. It provides rolls of flow regime and addresses the method of establishing target flow regime using the RVA(Range of Variability Approach) that suggested by Richter et al.(1997) through analysis of altered flow pattern case of Han river basin.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.333-342
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• 2022

Due to climate change, increased heavy rainfalls result in flood damage every year. To investigate the storm-runoff reduction effects of Low Impact Development (LID), this study performed runoff analyses using the U.S. Environmental Protection Agency (EPA) Storm Water Management Model (SWMM) for past and future representative storm events of the Yongdu Rainwater Pumping Station basin. As a result, the infiltration loss for representative future rainfalls increased by 3.17 %, and the surface runoff and peak runoff rate increased significantly by 32.50 %, and 128.77 %, respectively. To reduce the increased surface runoff and peak runoff rates, this study investigated the applicability of LID approaches, including a permeable pavement, green roof, and rain garden, by adjusting the LID parameters and the ratio of installation area. We identified the ranges of LID parameters that decreased peak runoff rate and surface runoff, and increased infiltration. In addition, when the application ratio of permeable pavement, green roof, and rain garden was 2:1:3, best performance was attained, leading to a reduction of peak runoff of 26.85 %, infiltration loss 12.01 %, surface runoff 15.11 %, and storage 509.47 %. Based on analyzing the effect of storm runoff reductions for various return periods, it was found that as the return period increased, the proportion of peak runoff and surface runoff increased and the proportion of infiltration loss and storage decreased.