• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.102-102
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• 2021

광양만의 해수교환은 주로 여수해만을 통해 이루어지고, 만의 동측에는 노량수로를 통해 진주만으로의 해수교환이 일어나고 있으며, 만의 북측에는 섬진강을 끼고 있다. 광양항 건설 전 만내의 수심은 약 10 m 이내로 얕았으며, 만의 입구인 여수해만과 노량수로에서의 수심은 약 20 m 이상이었다. 광양만은 1982년 광양제철소의 건설을 시점으로 하여 광양항의 확장 개발, 폐기물처리장 건설 등으로 인한 매립이 진행되었다. 특히, 섬진강 하구는 광양만 개발 전에는 넓은 조간대 퇴적층의 발달로 다양한 생태계환경을 유지하고 있었으나, 광양항 건설 및 하구에서 모래 준설 등으로 인해 근래에 와서는 해수의 역류가 심각한 상태이다. 1982년 광양제철소 건설이후 계속적으로 광양만을 개발함으로써 해양환경에 큰 변화가 발생하였다. 따라서, 본 연구에서는 광양만 개발 전·후의 조석 및 해수유동의 변화특성을 해석하기 위해 조석 및 조류에 대한 현장관측과 3차원 해수유동 수치모형실험을 수행한 후 남해도를 둘러싸고 있는 광양만, 진주만 등의 조석 및 조류의 변동특성을 해석하였다. 광양만 개발 전·후의 해수유동의 변동특성을 해석하기 위해 김 등(1999)에 의해 개발된 3차원 layer·level 혼성 해수유동 모델을 광양만, 진주만을 포함하는 남해도 주변해역에 적용하여 30일간의 수치계산결과를 이용하여 해수유동의 변동특성을 해석하였다. 모델에서 격자간격은 동서-남북방향 동일하게 200 m, 시간간격은 20 sec, 계산영역은 동서방향으로 52 km, 남북방향으로 65 km인 260×325 격자체계로 구성 운영하였다. 외해 개방경계에서 조위는 수로국에서 관측한 조위와 본 연구에서 관측한 조위를 보간하여 사용하였다. 광양만 개발전·후의 조류의 변동특성을 수치해석한 결과 여수해만에서는 광만만 개발전이 개발 후보다 유속이 강하게 나타났으나, 노량수로에서는 개발 후가 개발전보다 유속이 훨씬 강하게 나타났다. 이와 같은 현상은 광양만 개발로 광양만으로 유입되는 조량이 감소함으로 인해 여수해만에서는 유속이 감소한 것으로 생각된다. 노량수로에서 개발 후가 개발전보다 유속이 증가한 것은 여수해만을 통해 유입한 해수가 개발 후에는 광양만의 해수면적 감소로 광양만의 서측으로 유입하는 조량이 감소한 반면에 광양만의 북측(섬진강 하구) 또는 동측(노량수로)으로 유입하는 조량이 많기 때문인 것으로 사료된다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.3
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• pp.321-331
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• 2008

A model has been constructed in this study for the investigation of physical characteristics of the Gyeonggi Bay and Han River estuary. MIKE 21 HD (HyDrodynamics) has been used for the uncertainty analysis of the tide of the Gyeonngi Bay and Han River estuary. A total of 15 model experiments have been performed for the hydrodynamic parts and the analysis of results have been made in terms of RMSD (Root-mean square deviation) which has been frequently employed in the suitability analysis of hydrological data since the introduction by NERC(1975), U.K. A smaller value of RMSD indicates the more suitability of a parameter to the model. Analysis of the hydrodynamic results has shown that RMSD of the mean tidal range has the largest value of 0.1148 at Yeomha channel while has the smallest value of 0.0400 at Yeonphyong-do, indicating that the uncertainty in the mean tidal range on near-shore side is larger than that of offshore side. Experiment with reduced water depth by 10% has produced a most significant increase in RMSD. It is therefore implied that the model response changes more sensitively to water depth rather than grid sizes, open boundary forcing and river discharge.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.179-186
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Pohang Old Harbor and Pohang New Port, etc. due to construction of New Port in Youngil Bay. This type of trial might be a milestone for port development in macroscale, where the induced impact analysis in the existing port due to the developemnt could be easily neglected.

• Journal of Navigation and Port Research
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• v.35 no.1
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• pp.45-49
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• 2011

The recent trend for numerical experiment requires more higher resolution and accuracy. Generally, in the wave field calculation, it starts with a large region formulation first and follows by a separated detailed region formulation by more denser grids for the main interest area considering the geographical and bathymetrical variation. The wave fields resulted from the large region calculation is being introduced into the detail region calculation as the incident waves. In this process there exists a problem of continuity. In order to get over such problem, method of variable gridding system or spectrum sampling, etc., is being used. However, it seems not enough to examine and analyze the related numerical errors. Therefore, it is investigated in this study the field applicability of the most pervasive use of wave model, the nested SWAN model. For this purpose, we made model experiment for two coastal harbours with different tidal environment, and compared and analyzed the result. From the analysis, it was found that both the extracted values, near the boundaries of the large and detail region and the nested formulation of SWAN model, show almost the same and no different between those with different tidal environment conditions. However it is necessary for reducing the numerical errors to set the boundaries for the detailed region outside of the rapid bathymetric change and deeper region.

• Journal of Navigation and Port Research
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• v.28 no.5
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• pp.421-428
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Pohang Old Harbor and Pohang New Port, etc. due to construction of New Port in Youngil Bay. This type of trial might be a milestone for port development in macroscale, where the induced impact analysis in the existing port due to the development could be easily neglected.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.3
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• pp.23-31
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• 2009

The border of the shorelines in a nation is an important factor in determining the border of a national territory, but Korea's shorelines are rapidly changing due to the recent rise in sea level from global warming and growth-centered economic policy over the decades of years. This research was done centering on the areas having well-preserved shorelines as they naturally are and other areas having damaged shorelines in their vicinities due to artificial structures at the two beaches located at the neighboring areas and having mutually homogeneous ocean conditions with each other. First, this research derived the shorelines using the aerial photographies taken from 1947 until 2007 and revised the tidal levels sounding data obtained from a hydrographical survey automation system consisting of Echosounder[Echotrac 3100] and Differential Global Positioning System[Beacon]by using topographical data and ships on land obtained by applying post-processing Kinematic GPS measuring method. In addition, this research evaluated the changes and dimensional variations for the last 60 years by dividing these determined shorelines into 5 sections. As a result, the Haewundae Beach showed a total of 29% decrease rate in dimension as of the year 2007 in comparison with the year 1947 due to a rapid dimensional decline centering on its west areas, while the dimension of the Gwanganri Beach showed an increase in its dimension amounting to a total of 69% due to the decrease in flow velocity by artificial structures built on both ends of the beach-forming accumulation; thus, it was found that there existed a big difference in deposition & accumulation tendency depending on neighboring environment in spite of the homogeneous ocean conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.926-932
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• 2017

Image distortion can occur when photographing deep sea targets with an optical camera. This problem arises because sunlight is not sufficiently transmitted due to seawater and various floating particles of dust. Particularly, color distortion takes place, causing green and blue color channels to be over emphasized due to water depth, while distortion of boundaries also occurs due to light refraction by seawater and floating particles of dust. These distortions degrade the overall quality of underwater images. In this paper, we analyze underwater images of the bottom of vessels. Based on the results, we propose a technique for color correction and edge enhancement. Experimental results show that the proposed method increases edge clarity by 3.39 % compared to the effective edges of the original underwater image. In addition, a quantitative evaluation and subjective image quality evaluation were concurrently performed. As a result, it was confirmed that object boundaries became clear with color correction. The color correction and contour enhancement method proposed in this paper can be applied in various fields requiring underwater imaging in the future.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.561-571
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• 2019

The Hupo Basin, continental marginal basin, of the East Sea extends to Uljin-gun and Yeongdeok-gun. The Hupo Bank, a terrain that is higher than the surrounding seabed, is located at the eastern boundary of the Hupo Basin. KIOST(Korea Institute of Ocean Science and Technology) conducted detailed bathymetry surveys in the northern, central and southern areas of the Hupo Basin from 2011 to 2013. The Hupo Basin, bounded by steep slopes of the Hupo Bank, is deepened from the west coast to the east and deepest to a maximum depth of about 250 m. A narrow seafloor channel appears in the northern, central, and southern areas with the deepest depths. Numerous pockmarks appear on the seafloor at depths of about 150 ~ 250 m in all the three areas of the detailed bathymetry surveys. These pockmarks generally have diameters of about 20 to 50 m and depths of about 4 to 6 m, with craterlike submarine topography of various sizes. Seafloor sediments in the pockmark areas consist of fine silt. Comparing the shape and size of the pockmark of the Hupo Basin with that of other regions of the world, it is considered to be classified as a normal pockmark. There are about 7 pockmarks/1 ㎢ in the northern part of the three areas and about 8 pockmarks/1 ㎢ in the central part. The southern part has about 5 pockmarks/1 ㎢. If the area with the possibility of pockmarks is extended to the depth area of about 150 ~ 250 m in the entire Hupo Basin, the number of pockmarks is estimated to be more than about 4800. The pockmark of the Hupo Basin is more likely to be generated by a fluid such as a liquid than a gas. But it is necessary to scrutinize the cause and continuously monitor the pockmark.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.477-486
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• 2017

In this study, we analyze precise seabed geomorphology and conditions for comparing the nearshore areas of the Dongdo(East Island) and the Seodo(West Island) using detailed bathymetry data and seafloor backscattering images, in Dokdo, the East Sea. We have been obtained the detailed bathymetry data and the seafloor backscattering data. The survey range is about $250m{\times}250m$ including land of islets to the nearshore areas of the southern part of the Dongdo and the Seodo. As a result of bathymetry survey, the southern area of the Dongdo(~50 m) is deeper than the Seodo(~30 m) in the water depth. The survey areas are consist of extended bedrocks from land of the Dongdo and the Seodo. The underwater rock region of the Seodo is larger than the Dongdo. In spite of similar extended rocks features from islets, there are some distinctive seabed characteristics between the southern nearshore areas of the Dongdo and the Seodo. The Talus-shaped seafloor environment formed by gravel and underwater rocks originating from the land of the Dongdo is up to about 15 m depth. And the boundary line of between extended bedrocks and seabottom is unclear in the southern nearshore of the Dongdo. On the other hand, the southern coast of the Seodo is characterized by relatively large scale underwater rocks and evenly distributed sediments, which clearly distinguish the boundary of between extended bedrocks and seafloor. This is because the tuff layers exposed to the coastal cliffs of the Dongdo are weak against weathering and erosion. It is considered that there are more influences of the clastic sediments carried from the land of the Dongdo compared with the Seodo. Particularly, the land of the Dongdo has been undergoing construction activities. And also a highly unstable ground such as faults, joints and cracks appears in the Dongdo. In previous study, there are dissimilar features of the massive tuff breccia formations of the Dongdo and the Seodo. These conditions are thought to have influenced the different seabed characteristics in the southern nearshore areas of the Dongdo and the Seodo.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.4
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• pp.301-306
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• 2011

This study was determined to analysis the characteristics of water mass in the Bottol Bada, Yeosu in August, 2010 based on the data from the distribution of water temperature and salinity. Sampling was carried out a total of three times (i.e. July 29, August 13, and August 30, 2010) and performed at three stations. Observation was done during the period of time 10:00-15:00, indicating the decreasing tidal height and turn of tide. In July 29, thermocline was found at 4 m in St. 1, but the stratification did not observe in August 13 and August 30. The remarkable water temperature between surface and bottom was found in St. 2 and St. 3, whereas St. 1 did not find. A particular finding during this study showed a cold water mass at bottom layer from St. 2 and St. 3, which was first occurred in July 29 and persisted in August 30 without any of destruction. Water temperature had a remarkable fluctuation between surface and bottom, whereas salinity had a unique in St. 1. St. 2 and St. 3 showed the increasing salinity according to water depth in August 13 and August 30. Transparency had considerable fluctuations in St. 1 and St. 3 depending to sampling date, but St. 2 did not fluctuate. Consequently, the Bottol Bada had a significantly different water mass between inner and outer waters. Furthermore, strong irradiance and weak wind play an important role in developing the stratification between surface and bottom, in particular the introduction of offshore waters contribute to highly developing the stratification in the Bottol Bada during the period of August in 2010.