• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.3
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• pp.233-240
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• 1995

A large part of shoaling of navigation channel surrounded by fine sand is caused by suspended sediment in non-equilibrium state. We develop a numerical model for predicting shoaling of navigation channel where concentration of suspended sediment in such state is accurately simulated. In this study, effects of channel geometry on the shoaling of the channel are investigated numerically. A composite slope of navigation channel is also proposed to reduce non-equilibrium property of suspended sediment. It is found that the composite slope can effectively reduce non-equilibrium property of suspended sediment and the amount of sediment deposited in the main channel.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.1 s.28
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• pp.93-102
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• 2007

Particle materials sink in bottom and dissolved inorganic substances release from sediment and many kinds of materials continuously exchange in sediment and water column as well as transfer and transformation in sediment. The study of sediment quality means the state of sediment pollution relation of the water quality, sediment biota, materials fluxes between sediment and water column, transformation of materials in sediment is being important in recent. The state of sediment quality imply that the history of water pollution for long time, because the sediment quality does not change temporally. The sediment quality of bottom water can be used as a good indicator of pollution at present and in future. The major index of sediment qualities are the content of nutrients and hazard materials such as metals, Ignition Loss (IL), Total Sulfur (TS), Oxidation Reduction Potential (ORP), sediment COD, color, odor and the release of nutrients from sediment. However, there are some arguments between researchers about compare to estimation of sediment quality and sampling and analysis of sediment. In this study, I will introduce the method of sediment sampling, analyzing and estimating of the sediment pollution.

• Journal of Environmental Science International
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• v.22 no.3
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• pp.291-301
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• 2013

Sediment from the upstream channel has been deposited near the Nakdong River Estuary Barrage (NREB) due to the mild slope and decreased velocity. The annual mechanical dredging to ensure the flood capacity has been performed to remove the deposited sediment. However, the dredging method is not considered as an effective countermeasure due to high cost and long time to operate. Therefore, many methods for sedimentation reduction have been proposed for NREB. Especially, the channel contraction method to mitigate sedimentation problem by changing the channel geometry from 2 km to 3 km upstream of NREB has been recently suggested as an effective countermeasure. However, there is the possibility that the channel contraction method induces flood level increase compared to original condition. Therefore, it is necessary to investigate quantitatively the flood level changes in the upstream and downstream section due to the channel contraction method for NREB. In this study, water level changes by 10% channel contraction of whole width has been evaluated using the HEC-RAS model and simulated with and without channel contraction for various flood discharge. As a result, water level in the section where the channel was contracted was decreased by 0.02 m and flood level at the upstream of channel contracted was increased up to 0.015 m for the 500-year flood.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.923-932
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• 2012

The purpose of this study was to determine parameters of surface cover materials and evaluation the effects on runoff and sediment reductions with rice straw mat with PAM at watershed scale using the SWAT model. In this study, 1) regression equation of CN for rice straw mat + PAM using SCS curve number method was developed, 2) the USLE P factor, being able to reflect simulation of rice straw mat + PAM in the agricultural field, was estimated for various slope scenarios with VFSMOD-w. Then regression equation for CN and USLE P factor were used as input data in the SWAT model. Assuming rice straw mat + PAM is applied to radish and potato fields, occupying 24% of agricultural fields at the study watershed. Result of direct runoff without rice straw mat + PAM was $65,964,368\;m^3,$ with rice straw mat + PAM, direct runoff was $65,637,336\;m^3$, $327,031.8\;m^3$ reductions compared without it. Also, result of sediment without rice straw mat + PAM was 163,531 ton, with rice straw mat + PAM, sediment was 84,779 ton, 78,752 ton reduction compared without it. This analysis showed that about 48% sediment reductions would be expected with rice straw mat + PAM. As shown in this study, rice straw mat + PAM would be used as an efficient site-specific BMPs to reduce runoff and sediment discharge from field.

• Water for future
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• v.10 no.1
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• pp.95-100
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• 1977

The empirical area-reduction method by W.M. Borland and C.R. Miller and its revised procedure by W.T. Moody were made of fitting the area and storage curves to the Van't Hul distributions. It should be noted that the reservoir is classified into one of the four standard types on the basis of the topographical feature of the reservoir in application of the method. In other words, this method did not take into account several considerafble factors affecting the mode of sediment deposition, but only the shape of the reservoir as a governign factor. This is why the method occasionally creates ambiguity in classification and accordingly leads to unexpected mode of deposition. This paper describes a generating an formula to decide the standard classification of four types Van's Hul distributions, taking into consideration quantitatively sediment-loss percent and capacity-inflow ratio as well as the shape of the reservoirs by multiple regression analysis using the least square method to get a better fit to the design curves. The result is expressed as $Y=-1.95+55.8X_1+0.14X_2+0.12X_3$ in which the the values of Y locate the standard type I through type IV in the range from ten to forty with the interval of ten. The regression analysis was correlated well with the standard errors of estimate of around two except for the case of the type IV. This formula does not give big difference from the Borland's work in general sityation, but it demonstrates acceptable results, giving somewhat precise replys for the specific reservoirs. Its application to the Soyang Lake, one of the largest reservoirs in the country, defined clearly the type II, while the original method located it in the boundary of the type II and type III.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.521-526
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• 2016

Sediment dredging can permanently remove pollutants from an aquatic ecosystem, which is considered an effective approach to aquatic ecosystem restoration. In this study, we quantified the effects of sediment dredging on water quality in Masan Bay by calculation of oxygen demanding rate. We applied ecosystem model including water and sediment quality module in Masan Bay. The results showed that the increase of calculated oxygen demanding rate is significant due to sediment dredging of both inner part and outer part of Masan Bay. On the other hand, the increase is gradual due to decrease of anthropogenic load. It meant sediment dredging can improve water quality of Masan Bay more. Using correlation equation between oxygen demanding rate and sediment oxygen demand, we calculated that the area of sediment dredging which is equal to the effects of 10 % reduction of anthropogenic load. It is $1.68km^2$ in inner part and $3.15km^2$ in outer part of the Masan Bay. This Meant that to improve water quality of Masan Bay, sediment dredging in inner part is efficient method.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.6
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• pp.703-710
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• 2011

Odor emission from domestic sewer systems has become a serious environmental problem. An investigation on a sewer manhole revealed that anaerobic decay of sediment organic matters (SOMs) and related declines of oxidation reduction potential (ORP) in the sediment layer were the main reason of the production of volatile sulfur compounds. In addition, as the anaerobic decaying period continued, the odor intensity rapidly increased with increasing concentrations of $H_2S$ and dimethyl sulfide. As a feasible method to control SOMs and to minimize odor emission potentials, an electrolytic oxidation process has been employed to the sediment sludge phase. In this study, voltages applied to the electrolytic oxidation process were varied as a main system parameter, and its effects on odor removal efficiencies and reaction characteristics were investigated. At the applied voltages greater than 20 V, the system efficiently oxidized the organic matter, and the ORP in the sludge phase increased rapidly. As a consequence, the removal efficiency of hydrogen sulfide was found to be >99% within 60 minutes of the electrolytic oxidation. Overall, the electrolytic oxidation process can be an alternative to control odor emission from sewer systems, and a threshold input energy needs to be determined to achieve effective operation of the process.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.305-310
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• 1998

This research conducted concerning measures for the influence reduction to an investigation in the structure of offshore breakwater maintenance, an evaluation, a reexamination of the forecast, and a peripheral sediment transport environment. Furthermore, it aimed at the establishment of the beach transformation forecast method based on a hydraulic model study and a numeric simulation. A good result was obtained from a hydraulic model experiment and a numeric simulation as part of the basic research. And a qualitative evaluation of the flow field around the structure became possible since a numeric simulation examined flow field characteristics.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2016.11a
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• pp.391-392
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• 2016

본 연구에서는 우리나라 댐 저수지의 퇴사위 결정 방법에 대해 고찰해보고자 한다. 현재 우리나라에서 시행되고 있는 댐 저수지의 퇴사위 결정 방법에 대해서 조사하고 국외 여러나라에서의 퇴사위 결정 방법과의 비교를 통한 결과, 퇴사위 결정 방법에서는 경험적면적감소법(Empirical area reduction method)이 좀 더 논리적으로 기인한 것을 확인할 수 있었다. 향후, 댐 계획 및 설계시 구조적인 차원에서 짚고 넘어가야 할 문제일 것으로 판단되며, 설계기준 재정립시 이러한 사항을 수정 및 보완해야 할 것으로 사료된다.

• Journal of Wetlands Research
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• v.16 no.2
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• pp.173-185
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• 2014

Climate change has caused detrimental phenomena such as heavy rainfall which could aggravate soil erosion. Accordingly, it is needed to evaluate the groundwater recharge, baseflow, and soil erosion for the efficient management of water resources and quality. In this study, future climate change scenarios were applied to the H aean-myeon watershed which is a steep sloping watershed in South Korea to analyze groundwater recharge, baseflow, sediment. Also, the variation of groundwater recharge, baseflow, sediment was analyzed according to the change of slope (5 %). Simulated periods were divided into three terms (2013 ~ 2040 years, 2041 ~ 2070 years, 2071 ~ 2100 years). As a result of this study, average groundwater recharge and baseflow increased by 50 %, 42 %, and sediment decreased by 72 %, respectively. In these regards, the suggested method will positively contribute to hydro-ecosystem and reduction of muddy water at a steep sloping watershed.