• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.37-45
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• 2008

The purpose of this study is to quantify the settling velocities of cohesive sediments from Han estuary and to evaluate their local variation within Han estuary. This study also includes an estimation of their spatial variation, for which the settling velocities of cohesive sediments from Han estuary arecompared with those for sediments from other regions. At the same time, physical-chemical properties, such as grain size distribution, the percentage of organic contents, mineralogical composition etc are measured in this study in order to examine their correlation with settling velocities and their effect on settling velocities. Results from settling tests shaw that the settling velocities of Han estuary mud varies in the range of two orders of magnitude(from 0.01 to 1.5 mm/sec) over the corresponding concentration range of 0.1 to 80 g/L, and a feature of the settling velocity profile is quite different in quantity as compared to those of previous studies for muds from other regions. Particularly in the flocculated settling region, the settling velocity for Han estuary muds is shown to be larger than that of Saemankeum and Keum estuary sediments, while in the hindered settling region all three sediments are shown to have a similar settling velocity. However, local variability of the settling velocities within Han estuary is shown to be insignificant.

• Journal of Korean Society on Water Environment
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• v.33 no.2
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• pp.149-159
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• 2017

After the artificial barrage was constructed in 1990s, the Geumgang estuary has been experiencing considerable changes in nature as well as in socioeconomic and culture in the vicinity villages. In order to understand how the change of estuarine environment bring about conflicts among the local communities, and resolve the conflicts, the research investigated the causes of the conflicts in the Geumgang estuary using in-depth and semi-structured interview method. 100 local people who have lived in the vicinity of Geumgang estuary for more than 30 years were selected for the interviews. Results of the research shows that local people's jobs determine the opinions about the estuary barrage and the way of estuarine management. Understanding environmental change and local conflicts helps to develop a sustainable and integrated estuary management system in the region.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.1
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• pp.1-7
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• 2007

The purpose of this study was to investigate geochemical characteristics of surface sediments in the Keum river estuary adjacent to coastal area. For this study we collected the 21 surface sediments samples. Mean size of surface samples was $3.24{\sim}6.65{\phi}$ on inner estuary and was $2.15{\sim}3.42{\phi}$ on outside estuary. Surface samples were composed of silt on inner estuary and were composed of sand which was more larger than $4{\phi}$ on outside estuary. Most major elements except CaO, $Na_2O$ showed good relationships between variation of contents and grain size. Contents of $Al_2O_3$, $Fe_2O_3$, MgO, $K_2O$, $TiO_2$, $P_2O_5$ and $M_nO$ were increased predominately owing to the variation of mean size of surface samples. Contents of Co, Cr, Cu, Li, Sr, Zn, La, Ce, Pb, Rb, Nd have a good relationships with grain size but Ba, Th, Sm have not. All of major and minor elements contents except $K_2O$ and Ba were less than world mean contents of shallow surface sediments but apprehend a high pollution possibility on silt sediments in the estuaries.

• Journal of The Geomorphological Association of Korea
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• v.28 no.1
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• pp.35-50
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• 2021

In this study, we analyzed the changes in the topographical landscape and the sedimentary environment to evaluate the ecological value of the Dongcheon Estuary and protect the wetland, and presented the conservation management method of the Dongcheon Estuary. Based on the result of topographical landscape analysis, agricultural land tended to decrease continuously, and artificial structures gradually increased. Moreover, in sediment analysis, the Dongcheon Estuary showed both the characteristics of river sediments and coastal sediments, and in some areas problems such as acidification and nutritional imbalance appeared. Therefore, in order to protect and manage the Dongcheon Estuary with high ecological value, it is necessary to limit the development around micro topography and minimize the artificial damage in the Dongcheon Estuary. In addition, efforts such as securing facilities for reducing pollutants and freshwater wetlands for pollutants, that flow in from nonpoint pollutants are required.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.131-137
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• 2004

This paper is intended as an investigation of the deposition characteristics and mass transport flux estimation in the Nakdong estuary. In order to understand the effects of the tidal current circulation which influenced to an estuary terrain change, the seawater circulation calculation by the use of 2D numerical model for the three cases of without riverflow, mean and flood riverflow quantity condition practiced and each sectional net-flux of water quantity between sandbars(so called, dung) estimated. It may be that an estuary terrain change due to the large scale construction and reclamation at the Nakdong estuary influence to the long-time deposition characteristics. by the revim for the old research, we know that the development of the local sandbars has been moved toward the east-side from the west-side estuary area after the construction of the Nakdong river dike, at present the strong-acted location is the Bakhap-dung of the front sea of Tadea. The seawater circulation pattern at this large scale area of tidal flat bring on a change due to the water quantity outflowing from the Nakdong river. Base on the calculated results for the section net-flux of water quantity, we see that the accumulating action very strong at the local sea around Jangjado, Bakhapdung and Tadae for the case of flood riverflow quantity condition, but at the local sea around Jinudo for the another cases. Consequently, it is emphasized that in the Nakdong estuary the main sensitive regions which influenced from the discharge of riverflow were the local sea around Jangjado, Bakhapdung, Tadae and Jinudo.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.1
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• pp.55-64
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• 2005

Spatio-temporal variations of phytoplankton abundance and nutrient concentrations were investigated in the Namdaechon estuary, Yangyang, from April to December, 2003. A total of 51 phytoplankton species were identified with 32 diatom species in the study area. Phytoplankton abundance ranged from 14 cells/mL to 3,798 cells/mL. Small sized benthic and pennate-type diatoms like Cymbella spp., Fragilaria spp., Navicula spp., Synedra spp. were dominant at throughout the whole study area. Various planktonic species like Chlamydomonas sp., Peridinium spp., Euglena spp., Cryptomonas spp. etc. were abundant especially at the estuary of the Namdaechon, from May to August. Phytoplankton bloom (>3,000 \;cells/mL) occurred from the late May to mid June. After September when the sandbank of estuary was broken by the typhoon 'Maemi', planktonic species disappeared. These planktonic species were followed by oceanic diatoms, Skeletonema costatum and Chaetoceros spp.. Concentrations of dissolved inorganic nitrogen (DIN) and silicate were relatively high at the upstream in summer. In May, before phytoplankton bloom, high concentrations of phosphate $(>3.5\;{\mu}mol/L)$ were observed at all the study area. These results suggested that spatio-temporal variation of phytoplankton in the Namdaechon estuary was related to formation of sandbank at the mouth of the estuary, fluid speed affected by sandbank and nutrients supplied in spring. High correlation $(r^2=0.928)$ between chlorophyll a and biological oxygen demand (BOD) implies that BOD was related to phytoplankton abundance in the Namdaechon estuary.

• Korean Journal of Environment and Ecology
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• v.36 no.5
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• pp.468-480
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• 2022

Although the construction of the Nakdong River Estuary Barrage (NEB) improved the water supply in the region, it cut off the longitudinal connectivity of the estuary aquatic ecosystem. Thus, the social demands for opening the NEB have been continuously raised, and the efforts to restore the aquatic ecosystem of the Nakdong River estuary began in 2017. Many fish species have inhabited the Nakdong River estuary. Since their habitat and migration characteristics vary widely, the sluice gate operation considering them is essential for the restoration of the aquatic ecosystem. Therefore, in this study, we monitored the fish species living and migrating in the Nakdong River estuary and analyzed the possibility of smooth movement of for each fish species by calculating the average flow velocity according to the type and the height of the gate opening. Moreover, we selected the target fish species for each month and suggested the sluice gate operation according to the depth of the main habitat to present the measures that are ideal for optimal restoration of the aquatic ecosystem in the Nakdong River estuary area.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.5
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• pp.25-35
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• 2023

The estuary reservoir is a major source of agricultural water in Korea; for effective and sustainable water resource management of the estuary reservoir, it is crucial to comprehensively consider various water resource factors, including water supply, flood, and pollutant management, and analyze future runoff changes in consideration of environmental changes such as climate change. The objective of this study is to estimate the impact of future climate change on the runoff characteristics of an estuary reservoir watershed. Climate data on future Shared Socioeconomic Pathway (SSP) scenarios were derived from two Global Climate Models (GCMs) of the Coupled Model Intercomparison Project phase 6 (CMIP6). The Hydrological Simulation Program-Fortran (HSPF) was used to simulate past and future long-term runoff of the Ganwol estuary reservoir watershed. The findings showed that as the impact of climate change intensified, the average annual runoff in the future period was higher in the order of SSP5, SSP3, SSP1, and SSP2, and the ratio of runoff in July decreased while the ratio of runoff in October increased. Moreover, in terms of river flow regime, the SSP2 scenario was found to be the most advantageous and the SSP3 scenario was the most disadvantageous. The findings of this study can be used as basic data for developing sustainable water resource management plans and can be applied to estuary reservoir models to predict future environmental changes in estuary reservoirs.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1361-1362
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• 2005

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.6
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• pp.1842-1853
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• 2015

The behavior characteristics of the saltwater intrusion in the Seomjin River Estuary by the inflow of fresh water were analysed by the field observation using CTD in the neap tide in January, June, and August 2013 as well as a numerical model, EFDC (Environmental Fluid Dynamics Code). As a result, Seomjin River Estuary is found that the saltwater intrusion is sensitive to the tide and tidal and freshwater flow. The results of field observation and numerical model were similar in the range of salt, but the results of salt wedge distribution were quite different. The observation of tide and tidal current as well as hydrographic surveying the Seomjin River Estuary will be jointly conducted for the accurate analysis.