• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4B
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• pp.243-251
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• 2012

To investigate the characteristics of rip current occurring at Haeundae beach, observations obtained from a buoy and a CCTV were analyzed and numerical experiments were conducted. During observed rip-current events, the CCTV images showed that a couple of wave-trains, which are close to regular waves with slightly different directions, propagated to the beach, and wavelet analyses of data from the buoy showed very narrow-banded spectra with a peak frequency. From the evidences, it was inferred that a known mechanism of generating rip current due to the nodal line area of honeycomb-patterned wave crest was one of the significant factors of rip current occurrences of Haeundae beach. The mechanism has been explained by the following: When two wave-trains with slightly different directions propagate to a beach, wave crests of the incident wave-trains form honeycomb pattern due to nonlinear interaction. The nodal lines of honeycomb pattern are developed in the cross-shore direction. And longshore currents flow toward the nodal line area which has very low wave energy. Consequently their mass flux is expelled through the area toward the sea direction. To confirm the generation, numerical experiments were performed using a nonlinear Boussinesq equation model. In the cases with two incident wave-trains with slightly different directions and with a monochromatic wave propagating over a submerged shoal, it was seen that the honeycomb pattern of wave crests was well developed, and thus rip currents were evolved along the nodal lines.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4D
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• pp.407-419
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• 2012

It is difficult to obtain the accurate and homogeneous height information over the whole Korea due to the effect of different vertical datums have been divided into land and sea part. In this study, we tried to unify the different vertical datums using the precise spirit leveling between TBM (tidal bench mark) and BM (bench mark) in order to solve the problems caused by different vertical datums. For this, the vertical datum offsets at observed points which were calculate from leveling results and then transformation model of vertical datum will be modelled using calculated offsets along the coastal line. For suggesting the precise modelling method to vertical datum transformation, we analyzed results from various interpolation methods such as Spline and LSC method. As the results from analysis, the LSC method combined with 4-parameters trend model is more suitable for modelling the offsets between vertical datums. The final transformation model of vertical datum using the combination of LSC and 4-parameter model which provides the transformation accuracies of ${\pm}10.4cm{\sim}14.8cm$ level. And, the software for vertical datum transformation that was also developed using the final model in order to convert the height information included in various spatial data effectively. Therefore, the transformation model between vertical datums of land and sea part, which is developed in this study, is expected to minimize the confusion caused by mismatch of height information in the use of spatial data, and it also can be minimize economic and time losses in various application fields such as coastal development project, coastal disaster prevention, etc.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.1
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• pp.101-115
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• 2006

As coastal erosion is increasing sharply because of sudden changes in the natural environment and increases in artificial development, the problem of coastal erosion become an important issue, socially and economically. To building the data which needed to grasp the situation and find a solution, we need the monitoring system for long-term. In this study, we analyzed the coastal topography and land cover changes in the Haeundae Beach during 60 years. The Haeundae Beach is the most famous beach in the country and coastal erosion are going on. First, we analyzed the change of coastal topography by calculated the coastline and area of the beach using aerial photos during 60 years. We extracted the coastline by digitized on aerial photo and corrected the height of tide level using sounding and GPS survey data. And we computed the area of beach and analyzed the change of area during 60 years. Second, we analyzed the change of land cover using landcover map. We made the detailed landcover map by on-screen digitizing and estimated the soil loss for the area nearby Haeundae Beach. As a result, we could see that the coastline get nearer to land and the area of beach has been reduced in general. We think that interception of sand supply by the development is the artificial cause of coastal erosion. The result of this study would be useful in long-term coastal monitoring and to analyze the cause of coastal environment change. We expect that the result is available on the coastal information system.

• Journal of Navigation and Port Research
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• v.38 no.4
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• pp.357-366
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• 2014

On December of 2003, IMO's $23^{rd}$ Assembly discussed 'Guidelines on places of refuge for ships in need of assistance' At the discussion, Res. A.949(23) has been selected to appoint recommended place of refuge for countries signatory to the IMO Convention. IMO defines "Places of Refuge" as a places where a ship in need of assistance can take action to enable it to stabilize its condition and reduce the hazards to navigation, and to protect human life and the environment. Appointing and managing a Place of refuge can be a delicate problem because of its close connection to each country's coastal and environmental protection policies. However, in case of marine accident, the appointment or management of the place of refuge has a potential to avoid further damage and reduce to the minimum any environmental and estate losses. Currently a number of foreign countries, designated and operated a place of refuge. But, place of refuge selected method criteria were different by country and also does not have any standardized designating place of refuge model. Therefor, this study suggested the model of assigned places of refuge according to objective indication in order to assign reasonable and efficient places of refuge in domestic waters in the future by investigating and analyzing imported facts in considering the assignment of places of refuge in foreign countries and describing these imported data into quantitative value. In designating the model place of refuge, the final place of refuge location was presented by evaluating the probability of marine accidents, analyzing the location, and evaluating the supporting establishment.

• Clean Technology
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• v.7 no.4
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• pp.251-263
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• 2001

This study was conducted to provide a basic information for recovery plan of Seung-Gi Stream which is a major stream of Incheon metropolitan area. Source and characteristics of pollutants were analyzed and studied. Samples were taken 10 rounds in 5 sections in Seung-Gi stream. Annual pollutants loads and sectional characteristics of pollutants loads were investigated regarding flow rate, pH, DO, SS, $BOD_5$, $COD_{Cr}$, T-P, TKN and concentrations of Zn, Cd, Cu, Cr atoms which enter into Seung-Gi stream during rainy and dry season respectively. As one came close to the Nam-Dong Industrial Complex, sectional discharge loads were heavy and water quality was failed to meet the standard by "Environmental Standard of River Quality". As a result, heavy load of pollutants in Seung-Gi stream was considered to influence negatively the sea water quality of Incheon. Solution plans to solve problems are as follows. First, circulation of treated water at Seung-Gi WWTP(Wastewater Treatment Plant) and retreated water by URC(ultra rapid coagulation) process treat with that. Second, sewage and wastewater is gathered, make it disposed. After then, we circulate treated water. If solution plans be applied, we can predict water quality. Then we could grope for how make to recovery role of Seung-Gi stream as stream.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.401-409
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• 2013

In the present study, numerical analysis was performed for hydrodynamic motion and structural performance on four different concrete floating structures, which have same cross-section but different length. The hydrodynamic analysis of floating structures is carried out using ANSYS AQWA with the different 34 wave load on regular wave period from three seconds to ten seconds in 35 m water depth. In order to evaluate structural performance of floating structures under the critical wave load which obtained from hydrodynamic analysis. The integrated analysis is also carried out through the mapping method, which can directly connect the wave-induced hydraulic pressure obtained form ANSYS AQWA to Finite Element Model in ANSYS Mechanical. As a results of this study, the hydrodynamic motion of floating structures is decreased as the length of structure increased. It means that the effect of wave-structure interaction is strongly dependent on the relationship between a wave period and a length of structure. Moreover, it is found that tension stress on bottom slab of floating structure is occurred by the critical wave load, the sectional force is not influenced by length of a structure.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.4
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• pp.315-326
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• 2015

Temporal and spatial variations of surface water temperature in Jinju Bay for the period of 2010~2011 were studied using the data from temperature monitoring buoys deployed at 17 stations in the south coast of Korea. Water temperature shows the maximum late in January and the minimum early in August. Seasonal variation of water temperatures at the north part of the bay is smaller than the middle and the south. In summer, the lowest and the highest of maximum water temperature are distributed around Jijok Channel which is located at the south of the bay. The fluctuations of water temperatures at Noryang and Daebang Channel are smaller than others because of vertical mixing caused by passage of strong tidal currents. Wind and strong currents affect on the stratification of the surface water layer near Daebang Channel. High temperatures come in frequently around the north area when eastward constant flows appear at neap tide as blowing westerly in the springtime at Noryang Channel. Spectral analyses of temperature records show significant peaks at 7~20 day periods at Noryang Channel, 7~20 day and semidiurnal at the west coast of Changsun Island and Jijok Channel and 7~20 day and diurnal at the middle of the bay. Temperature fluctuation at Noryang Channel shows high coherence and has leading phase with those at other stations in the bay. However, the phase of temperature fluctuation at Noryang Channel falls behind that at Daebang Channel. Daebang Channel has an influence on the temperature fluctuation only at the west and middle part of the bay. Cross-correlation analyses for the temperature fluctuation show that Jinju Bay could be classified into six areas; Noryang Channel, the area of convergence and divergence at the north, Daebang Channel, the west coast of Changsun Island, the mixing area at the middle of the bay and the south inside of the bay, respectively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.4
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• pp.372-380
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• 2015

In order to study the characteristics of physical environment in water column around the artificial upwelling structure, CTD and currents measurements were carried out along line observations. Before installation of artificial upwelling structure was installed, the stratification of water column existed 30m in water depth. After installation of artificial upwelling structure, however, stratification formation depth and strength changed depending on currents directions. It seems that the change of stratification has a close relation with upwelling of lower temperature water. After installing the artificial upwelling structure, the distributions of vertical flows were analyzed. Local upwelling and downwelling flows showed a distinct time and spacial changes. Local upwelling flows caused by artificial upwelling structure appeared 100 times larger than coastal upwelling in the South-East Sea of Korea. Upwelling flows generated by the artificial structure raised the high concentration of nutrients to upper layer from lower layer breaking stratification in the summer. Thus, upwelling structure plays an important role for vertical water circulation improving the food environments by increasing primary production.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.4
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• pp.393-403
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• 2011

In this study, we suggested the period of tide observations is proper to calculate the mean sea level(MSL) precisely on Incheon tide station using wavelet analysis, and newly determined then the vertical reference surface of Korea using the calculated MSL. In order to calculate the height difference between the calculated MSL and specific ground station (ICGP) near the Incheon tide stations, we performed the laser measurements directly to the sea surface where located below ICGP. The orthometric-height of ICGP was determined that corrected the height difference to the calculated MSL using linear interpolation method. Finally, we connected the orthometric-height of ICGP with the original benchmark (ORBM) using GPS leveling methods for determining the new orthometric-height of ORBM. As the results, there is a variation amount of 0.026m between the new MSL was calculated in this study and old MSL was calculated in 1910's. Also, there is a difference of 0.035m between the new and old orthometric-heights of ORBM. The connection (or leveling) error of 0.009m was revealed in new orthometric height of ORBM with consideration of MSL variation which may caused by the error of GPS ellipsoid height and/or geoid model. In this study, we could be determined precisely the orthometric-height of ORBM based on the new MSL of Incheon Bay using only GPS leveling method, not a spirit leveling method. Therefore, it is necessary to determine the vertical datum strictly using long-term and continuously tide observations more than 19 years and to use the GPS leveling method widely in the height leveling work for the effective changeover from the orthonormal to the orthometric in national height system.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.4
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• pp.224-229
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• 2011

Recently, the management of the marine invasive alien species introduced by ballast water has come to the core as an urgent task. Because, hazardous organisms cause harmful effects on the ecosystem. Hazardous organisms also negatively affect fisheries, commercial shipping activities, and marine resources. In this regard, IMO used to operate GloBallast, Ballast Water Risk Assessment System, in order to manage the introduction of invasive species by ballast water. GloBallast is constructed to assess the relative risk due to the movement of ballast water between nations, using the volume and the number of times of ballast water discharge, the environmental similarity between ports, and the abundance of hazardous species as the main factors. According to the results of the demo-operation of GloBallast, it was found out that the environmental similarity factor had affected most highly the results of risk assessment. Therefore, in this study, the correlation between the main factors used in GloBallast risk assessment were re-examined, and some methods were suggested in order to reflect these main factors in the risk assessment more reasonable.