• Journal of Korean Society on Water Environment
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• v.24 no.6
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• pp.651-658
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• 2008

Estuary barrier is a hydraulic structure constructed to supply safely water as protecting chlorine penetration of sea water. However, the barrier brings about a problem which decreases original functions of estuary because hydraulic ecology was disrupted as obstructing natural water exchange between fresh water and sea water. It is important to supply Enough fresh water in the estuary ecosystem. But it is possible to reduce the problems brought from barrier throughout efficient water gate operation of estuary barrier. It was shown in this study that the environmental effect of estuary in Nakdong river was investigated according to the control of water level. Also, the basic information about the effective water gate operation was provided. The analysis results showed that the release rate of estuary was increased about 20% as changing the operational water levels. This helps supplying fresh water durably to the mixing zone. Also, CE-QUAL-W2 model was utilized to assess water quality. The values of BOD and COD were not changed in estuary area. From the result, it was analyzed the effect of water quality according to the water gate operation was not indicated.

• Journal of the Korean association of regional geographers
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• v.13 no.1
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• pp.43-53
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• 2007

Rapid geomorphic changes occur in Nakdong River deltaic coast which is composed of deltaic barrier islands and tidal flats. We investigate the pattern of these rapid geomorphic changes by analyzing the distributions of sediment grain size characteristics. The distributions of sediment grain size characteristics analysis is a very efficient method to explain geomorphic changes of deltaic barrier islands. In sediments from Jinwoo Island, Sinja Island, and Doyo Island which are composed of Nakdong River deltaic coast, mean particle size increases to onshore direction and become coarser in tidal inlets. All sediments are very well sorted. Though almost sediments show little negative skewness, several sediments from tidal inlets show negative skewness. These results provide that the stronger and more regular energies affect Nakdong River deltaic coast and make fine sediments selectively move toward tidal inlets. Because of this mechanism, the recurved spits of deltaic barrier islands enlarge.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.268-278
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• 2001

To investigate sedimentary facies and environmental changes of the Nakdong River Estuary and its adjacent coastal area, the grain size analysis and measurement of organic matter, calcium carbonate, clay mineral and metallic elements were carried out for forty surface sediment samples. Based on regional distribution pattern and characteristics of the surface sediments, sedimentary facies in the study area can be divided into sand facies (TYPE I), mud facies (TYPE II) and sand-mud mixed facies (TYPE III). TYPE III is the transition of TYPE I and TYPE II in every aspects of sediment characteristics. It suggests that TYPE III may have been formed by the mixture of two different source of sediment : one derived from Nakdong River and the other resuspended fine-grained sediments from the Jinhae Bay by winnowing action during floods or storms. Among many aspects of environmental change after the construction of the Nakdong Barrage, the most significant is the increase of sand content off the sand barrier region. It could be explained by several reasons including decreased input of fine-grained sediment from river, increased hydrodynamic energy level off the sand barrier region and artificial effects such as dredging and dumping.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.3
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• pp.112-124
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• 2016

In order to see the spatio-temporal distribution patterns of macrobenthic fauna in subtidal areas of Nakdong River estuary, benthic fauna samples were collected seasonally at 8 sites in subtidal areas of Nakdong River estuary from February, 2013 to November, 2015. Sandy sediment facies was found in the southern part of the barrier islands in Nakdong River estuary while muddy sediment facies occupied at sites in offshore areas. The bottom salinity of the study area was measured greater than 30 psu during the study period. The mean species richness and density were estimated as 266 species and $859ind\;m^{-2}$, respectively. Polychaete worms were the most abundant fauna group, and four polychaete species such as Goniada maculata, Sternaspis chinensis, Magelona japonica, and Heteromastus filiformis occurred as dominant species in this study area. Pseudopolydora kempi known as an opportunistic species occurred dominantly only in August, 2013. From the multivariate analyses, the macrobenthic fauna in the subtidal area of the Nakdong River estuary could be divided into 2 assemblages that each occupied sites near barrier islands and offshore areas by sediment facies.

• Ocean and Polar Research
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• v.35 no.1
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• pp.1-14
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• 2013

Shoreline data of the barrier islands in Nakdong River Estuary for the last three decades were assembled using six sets of aerial photographs and seven sets of satellite images. Canny Algorithm was applied to untreated data in order to obtain a wet-dry boundary as a proxy shoreline. Digital Shoreline Analysis System (DSAS 4.0) was used to estimate the rate of shoreline changes in terms of five statistical variables; SCE (Shoreline Change Envelope), NSM (Net Shoreline Movement), EPR(End Point Rate), LRR (Linear Regression Rate), and LMS (Least Median of Squares). The shoreline in Jinwoodo varied differently from one place to another during the last three decades; the west tail has advanced (i.e., seaward or southward), the west part has regressed, the south part has advanced, and the east part has regressed. After the 2000s, the rate of shoreline changes (-2.5~6.7 m/yr) increased and the east advanced. The shoreline in Shinjado shows a counterclockwise movement; the west part has advanced, but the east part has retreated. Since Shinjado was built in its present form, the west part became stable, but the east part has regressed faster. The rate of shoreline changes (-16.0~12.0 m/yr) in Shinjado is greater than that of Jinwoodo. The shoreline in Doyodeung has advanced at a rate of 31.5 m/yr. Since Doyodeung was built in its present form, the south part has regressed at the rate of -18.2 m/yr, but the east and west parts have advanced at the rate of 13.5~14.3 m/yr. Based on Digital Shoreline Analysis, shoreline changes in the barrier islands in the Nakdong River Estuary have varied both temporally and spatially, although the exact reason for the shoreline changes requires more investigation.

• Ocean and Polar Research
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• v.36 no.2
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• pp.87-101
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• 2014

Recently, more attention has been paid to the geomorphological changes in the Nakdong River Estuary, because those changes are caused by artificial activities including weirs, reclamation and construction. In order to analyze quantitatively the recent geomorphological variability in the Nakdong River Estuary, we surveyed the depth and elevation of submarine topography near Jinwoodo and Sinjado from March 2007 to February 2012. A statistical method (based on Digital Shoreline Analysis System) and an Empirical Orthogonal Functions method were used to evaluate the morphological changes. According to the statistical variables (DCE, NDC, EPR, LRR), the highest amount and rate of accumulation were recorded around the Gadeokdo whereas the greatest amount of erosion appeared around the coast off the eastern part of Sinjado. In particular, a dynamic variation of morphology was clearly observed in the vicinity of the sub-tidal channel located between Jinwoodo and Sinjado, which seems to be attributable to channel migration. As a result of the EOF method, the first mode (48.7%) is most closely related to the pattern of morphological variability that might be associated with the westerly movement of sediment by longshore current. The spatial variability of the second mode (16.6%) was high in the shoreface of Sinjado, showing a 4-year periodicity of temporal variability. The strong correlation (coefficient 0.73) between the time coefficient and suspended sediment discharge from Nakdong River emphasizes the role of sediment discharge to deposition in this area. The spatial variability of the third mode (11.3%) was distributed mainly around the coast off the eastern part of Sinjado, which is related to the movement of the coastline of Sinjado. Based on the last 5 year's data, our results suggest that the study area is characterized on the whole by a depositional pattern, but the extent of sedimentation is different locally.

• Journal of Wetlands Research
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• v.16 no.3
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• pp.355-362
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• 2014

Changes of soil properties due to sedimentation and erosion in the river estuary may lead changes in environmental factors that affect plant growth and distribution, Then habitats in the river estuary that provide various ecological functions can also be influenced. Topsoil samples were analyzed in order to understand the soil properties of important barrier islands and habitat types in the Nakdong river estuary. The samples were obtained from Phragmites communis and Scirpus planiculmis habitats, the tidal flats in the southern area of Eulsukdo, and in Mangeummerydeung, Baekhapdeung, and Doyodeung. Analyses results showed that bulk density, pH, organic matter content and total nitrogen concentration which were directly or indirectly affected by vegetation showed significant difference (p<0.05) with habitat types but no differences in water content and oxidation reduction potential which could be affected by soil texture and showed significant difference among barrier islands. Results suggested that soil properties on barrier islands in the Nakdong river estuary were influenced first by geomorphic changes due to sedimentation and erosion, and then by the presence or type of vegetation. A range of physical and chemical properties were analyzed; soil water content and bulk density (physical properties), and organic content and pH (chemical properties) were correlated with seven other soil properties, at a level of significance higher than 90%. These aspects played an important role in determining overall soil properties in the studied area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.1-11
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• 2020

This study investigated the mesozooplankton community and the related environmental factors in the Nakdong River Estuary in May and early October shortly after passage of the typhoon "DUJUAN" in 2015. The mesozooplankton community was dominated by barnacle nauplii, foraminiferans, and Noctiluca scintillans, and the environmental characteristics were characterized by freshwater inflow through the Nakdong River barrage, the intrusion of warm currents, and the effect of typhoon passage in October. In May, cladocerans, such as Evadne nordmanni and Podon polyphemoides, as indicator species of brackish water, prevailed throughout the study area. The surface salinity was lowest on the inner side of the barrier-islands and increased gradually to the outer side during the study. The average concentration of total suspended solids in October was higher than that in May, while the averaged concentration of nitrate and chlorophyll-a in May was higher than those in October. On the other hand, there was no temporal difference in the total averaged abundance of mesozooplankton. In contrast, the distributional pattern of the mesozooplankton community was associated with the salinity gradient in both seasons. These results suggest that the temporal difference of the mesozooplankton community depended on the extent of freshwater inflow by barrage opening, the intrusion intensity of warm currents, and typhoon passage in the Nakdong River estuary in 2015.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.3
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• pp.91-102
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• 2016

The spatio-temporal variations of the dissolved methane concentration were investigated and the methane budget was estimated in the Nakdong Estuary in January, September, and November of 2014. Dissolved methane showed seasonal variation (21~874 nM) with high concentration in summer due to enhanced temperature and fresh water discharge. Decreasing trends of dissolved methane from the river to the estuary were consistent in all seasons showing the main source of the estuarine methane is river discharge. However, the decreasing trends were modified seasonally due to the local sources such as organic-rich sediments in intertidal zone or near the estuarine barrage. Dissolved methane concentration in the Nakdong Estuary was high, compared to other estuaries probably due to the well developed wetland in Nakdong-river system and stagnation effect from barrages and dams. Dominant sink for the Nakdong estuarine methane was outflux into the atmosphere. Relatively long residence time (produced by barrier island and estuarine dam) in the estuary might provide the enough time for the outgassing.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.2
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• pp.161-168
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• 2010

We conducted a field survey of the generation and development of the delta area of the Nakdong River estuary, Korea. To examine deposition and erosion of the barrier islands, we observed the spatiotemporal variations of sediment transport and quantitatively estimated the settling velocity of coastal sediment. For the field survey, we established two survey sites off the coasts of Jinu Island and Doyodeung, which had shown rapid variations in deposition and erosion. At these sites, we measured the net surface elevation change of the bottom level at approximately 1-month intervals. Main findings were summarized as follows. (1) Calculated daily deposition and erosion velocity during the observation period ranged from -1.39 to 3.56cm/day at Jinu Island and from -4.0 to 3.07cm/day at Doyodeung, respectively. (2) Although two typhoons passed by the study area during the observation period, the maximum net surface elevation was larger in October than during the passage of those typhoons.