• Korean Journal of Ecology and Environment
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• v.46 no.2
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• pp.205-214
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• 2013

In Yeongsan River estuary, located in the southern West Coast, a dike was constructed in December 1981. After the construction of a dike, discharge mechanism of fresh water has been changed, the water quality and chlorophyll-a are expected to be influenced by fresh water discharge. We investigated temporal and spatial variations and long-term trend of phytoplankton biomass (chlorophyll-a) and environmental factors. The concentrations of nutrient and chlorophyll-a were generally high in summer and the concentrations were increased toward downstream. Surface/bottom salinity difference was negatively correlated with salinity in surface water but positively with nutrient and chlorophyll-a. TN, TP and DIN concentrations were generally increased over 10 years. This study can provide information for better management of water quality for Youngsan River estuary.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.145-153
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• 2009

This research utilized the manual to calculate the structural scale of stone and gabion, which was developed through comparison and verification of the results drawn by hydraulic model experiment and existing empirical formula. Appropriate structural scale of stone according to the construction site when the critical velocity was exceeded, utilizing the previously expected and recorded data on current velocity per day and per hour during the final closure period for Saemangeum sea dike. Also, the scale of rocks was presented, considering the altercation in water depth according to the construction. The developed manual offered appropriate rate of mixed use of stone and gabion that suits various flow velocities, which will minimize any loss of stone-gabion and contribute to successful final closure, and proved the utility and application of the manual.

• Journal of the Korean Institute of Gas
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• v.24 no.2
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• pp.29-35
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• 2020

The Chemical Control Act has revised in 2015 to promote chemical safety, particularly enhancing the standards for the installation and management of hazardous chemical handling facilities. However, in some existing facilities, it was difficult to comply with some facility standards because of lack of land, safety accident possibility during rebuilding. In this study, we attempted to provide a more rational approach of dike standard which was the highest(2017: 117, 2018: 83) complaint for two years(2017~2018, 1,087) by prior study, FLACS simulation, analyze safety management standard and conduct a survey. Therefore, considering the purpose of installing the discharge wall only at existing facilities in operation, additional sensors that can detect chemical leakage and leakage were recognized as an additional alternative to installing and operating closed circuit television (CCTV). This will help the safety and cost aspects of small or medium-sized businesses or small and medium-sized enterprises that cannot secure legal grounds or fail to enforce legal regulations due to economic problems such as construction costs.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.1
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• pp.71-79
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• 1999

As part of an on-going project investigating flux of materials in the Keum River Estuary, we have monitored seasonal variations of nutrients, suspended particulate matter (SPM), chlorophyll, and salinity since 1997. Meteorological data and freshwater discharge from the Keum River Dike were also used, Our goal was to answers for (1) what is the main factor for the seasonal fluctuation of nutrients in the Keum River Estuary? and (2) are there any differences in nutrient distributions before and after the Keum River Dike construction? Nitrate concentrations in the Keum River water were kept constant through the year. Whereas other nutrients varied with evident seasonality: high phosphate and ammonium concentrations during the dry season and enhanced silicate contents during the rainy season. SPM was found similar trend with silicate. During the rainy season, the freshwater discharged from the Keum River Dike seemed to dilute the phosphate and ammonium, but to elevate SPM concentration in the Keum Estuary. In addition, the corresponding variations of SPM contents in the estuarine water affected the seasonal fluctuations of nutrients in the Estuary. The most important source of the nutrients in the estuarine water is the fluvial water. Therefore, the distribution patterns of nutrients in the Estuary are conservative against salinity. Nitrate, nitrite and silicate are conservative through the year. The distribution of phosphate and ammonium on the other hand, display two distinct seasonal patterns: conservative behavior during the dry season and some additive processes during the rainy days. Mass destruction of freshwater phytoplankton in the riverine water is believed to be a major additive source of phosphate in the upper Estuary. Desorption processes of phosphate and ammonium from SPM and organic matter probably contribute extra source of addition. Benthic flux of phosphate and ammonium from the sediment into overlying estuarine water can not be excluded as another source. After the Keum River Dike construction, the concentrations of SPM decreased markedly and their role in controlling of nutrient concentrations in the Estuary has probably diminished. We found low salinity (5~15 psu) within 1 km away from the Dike during the dry season. Therefore we conclude that the only limited area of inner estuary function as a real estuary and the rest part rather be like a bay during the dry season. However, during the rainy season, the entire estuary as the mixing place of freshwater and seawater. Compared to the environmental conditions of the Estuary before the Dike construction, tidal current velocity and turbidity are decreased, but nutrient concentrations and chance of massive algal bloom such as red tide outbreak markedly increased.

• Korean Journal of Environmental Biology
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• v.29 no.3
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• pp.212-224
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• 2011

The Yeongsan River estuary, located in the south west coast, was a typical estuary before a dike was constructed in December 1981. After the construction, the water quality and plankton communities are expected to change. We investigated the change of phytoplankton community and environmental properties in the Yeongsan River estuary by comparing the data collected recently with the results reported before and/or shortly after the construction. Concentrations of $NH_4$-N were significantly increased in the freshwater zone. Concentrations of DO at the surface, $NO_2+NO_3$ and $NH_4$-N were increased while the concentrations of $PO_4$ at the surface were decreased in the seawater zone. The number of green algae species was decreased in the freshwater zone. The number of diatom species was decreased while the numbers of green algae and dinoflagellates were increased in the seawater zone. This study can provide information for better management of the Yeongsan River estuary since no comparison study has been documented between the phytoplankton community before and after the construction of the dike in the estuary.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.258-271
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• 2010

In order to figure out hydrodynamic and water quality changes after completion of dike construction of the Saemangeum, which behaves as a semi-enclosed estuarine lake, numerical simulations based on fine grid structure by using EFDC were intensively carried out. In this study some limitations of precedent study has been improved and gate operation were considered. Also 3 phases such as air-water-sediment interaction modeling was considered. It is clear that inner mixing of the Saemangeum is dominated by Mankyeong and Dongjin riverine discharges rather than the gate opening influence through the Lagrangian particle tracking simulations. Vertical DO structure after the dike completion shows steep gradient especially at Dongjin river estuary due to lessen of outer sea water exchange. Increasing SOD at stagnantly changed man-made reservoir might cause oxygen deficiency and accelerating degradation of water quality. According to TSI evaluation test representing eutrophication status, it shows high possibility of eutrophication along Mankyeong waterway in spite of dike completion, while the index is getting high after final closing along Dongjin waterway. Numerical tests with gate operations show significant differences in water quality. Thus it should be noted that proper gate operation plays a major role in preserving target water quality and management for inner development plan.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.3
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• pp.115-125
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• 2001

To examine the movement of the freshwater discharged artificially into the estuary during ebbing period in the Keum River dike we observed surface salinity variations in three stations along the estuary channel in May 1998 and July 1997 and surface temperature and salinity along the ferry-route between Kunsan and Changhang during eighteen days in July 1999. Based upon the typical features of observed salinity variation, we analyzed the excursion and decay processes of the discharged water. When freshwater is discharged, the low-salinity water forms strong salinity front over the entire estuary width, which basically moves forth and back by tidal modulation along the channel, producing the sudden change of surface salinity with the front passage. Salinity distribution along the channel, which is deduced from time variation of mean salinity over the estuary width, after one tidal period from gate operation suggests that diluted low-salinity water is trapped to the front and surface salinity increases gradually toward the upstream region. This frontal distribution of salinity is interpreted to be produced by the sudden gate operation supplying and stopping of freshwater within about two hours. Daily repeat of freshwater discharge produces separation (double front) or merge between decaying and new-generated fronts depending on dike-gate opening time, and the front decays with salinity increasing if the freshwater supply is stopped more than two days. In addition, the observed fluctuations and deviations in surface salinity variation is explained in terms of the differences of fronts intensity, their transition time and temporal salinity front running along the channel, which can be generated due to artificial gate-operation for the discharging time and water volume in the estuary dike.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.257-261
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• 2002

We have carried out integrated research including field survey and numerical modeling to appraise the applicability of SP method to the leakage problems of irrigation facilities. The leakage pattern of the dike studied here can be classified into the three categories: leakage through the abutment, leakage by piping through dike, and leakage due to the composite effects of landslide and distortion of the dike structure. for the numerical modeling to interpret quantitatively SP survey results acquired at dike, we have modified the computer code proposed by Sill (1983) to apply to the leakage problems. The numerical studies match the characteristic patterns of SP anomalies according to the leakage types and appear to be very useful to interpret the leakage zone and path. The SP monitoring results were also well coincided with tidal variations observed at every embankment so we found the SP method is quite effective not only to detect the leakage zone but also to determine the leakage trend. The numerical modeling results also reproduced the SP anomalies due to seawater leakage in the embankment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.295-306
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• 2004

Spatial patterns in the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike and environmental variables were examined in August 2001, In total, 156 macrobenthic species(123 intertidal species and 90 subtidal species) were recorded during this study, predominately polychaetes $(40{\%})$, bivalves $(22{\%})$, and crustaceans $(22{\%})$. Polychaetes made up less than $40{\%}$ of the intertidal communitr, but more than $50{\%}$ of the subtidal community. The mean density during this study was $1,456ind./m^{2}.$ Multivariate analysis (multidimensional scaling) revealed significant differences in community structure among four regions: near the Iwon dike (B1), the high and middle intertidal zone (B2), low intertidal zone (Al), and subtidal zone (A2). The number of species, total density, and diversity (H') varied significantly among the four regions. The distribution of macrobenthic community was affected by environmental variables, such as ${\%}$ silt/clay content, total sulfide, lose of ignition, and chemical oxygen demand. These environmental variables were negatively correlated with the dominant species (Nephtys polybranchia, Umbonium thomasi, and Scoloplos armiger) in the intertidal area, but positively correlated with the dominant species (Lumbrineris cruzensis, Notomastus latericeus, and Moerella sp.) in the subtidal area. Environmental variables $({\%}\;silt/clay content and total sulfide)$ were positively correlated with the dominant species (Heteromastus filiformis) in region Bl, but negatively correlated with the dominant species (Umbonium thomasi and Scoloplos koreanus) in region B2. Amphipods Urothoe spp. and Monoculodes koreanus were the dominant species in region Al. Umbonium thomasi, the dominant species in region B2, was not found in regions Bl or Al. We suggest that the inter-specific competition for territory and exposure to seawater may be important factors controlling the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2004.08a
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• pp.282-285
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• 2004