• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.601-610
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• 2021

The tidal current patterns at Keum River Estuary before and after the construction of coastal structures were compared according to the CASES. The depth-integrated and tidal difference treatment applied FLOW2DH numerical model was used for the tidal current predictions. The test conditions consisted of before construction of coastal structures (CASE1), after construction of coastal structures (CASE2), and the addition of watergate operation(CASE1Q and CASE2Q), and present (CASE3). CASE1 showed a stable tidal current pattern, such as a natural estuary. In CASE2, the tidal current velocities and directions of the Keum River Estuary were changed due to the installed coastal structures. In particular, the tidal current velocities of the Gaeya open channel sections (P5~P9) in CASE2 were calculated to be 10~30% larger than that of CASE1. In the case of the Gunsan Inner Harbor (P4), which is closest to the Geum River Estuary, the ebb flow rate was approximately 250~300% faster than that of other CASEs due to the discharge of the watergate operation for 2.7 hours during the ebb of CASE1Q and CASE2Q. This will affect sediment transport, and it is predicted to lead to seabed changes. CASE3 is considered to be entering the stabilization stage according to the simulation of the tidal current velocities and directions of the Keum River Estuary and the surrounding coastal area.

• Journal of Korean Society of Rural Planning
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• v.8 no.2 s.16
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• pp.42-49
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• 2002

Since legislation of Rural Minor Road Improvement Act 1990, a quarter of its total length had been paved now. However, over 80% of arterial road length(national+provincial roads) had been paved, so, road improvement policy should be focussed on the local road(county+rural minor roads) from now. Generally, in the greater part of coastal plain and island areas, arterial road intensity(total road length/total catchment area) is relatively low, but local road intensity is relatively high. So, in terms of balanced development, much more efforts for rural minor road improvement should be concentrated in coastal plain and islands areas. In Chonnam Province, the maximum differentials of minor rural road improvement ratio was over 20%(the lowest; 14.1% in Goheung, the highest; 35.6% in Goksung) in 1999, but the improvement budget have been allocated in proportion to unpaved road length of each county by the provincial government. However, the differentials should not be fairly narrowed in the near future if the present budget allocation policy be maintained. To solve this problem, target differentials of rural minor road improvement between regions should be set up for each planning year and road improvement budget be allocated according to this policy change.

• Journal of Korean Port Research
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• v.8 no.2
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• pp.37-56
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• 1994

The effects of wave energy focusing by a submerged berm type of structure is examined. The fundamental idea is based on the phenomenon of refraction by a lens-shaped crescent structure which results in the focusing of wave energy on the center line of the structure. The shape of the submerged structure is a complex curve combining circular with elliptical elements. Based on the design procedure, a special configuration of structure(termed herein as a triple crescent structure) is introduced. Next, some hydraulic model tests are performed to confirm the wave focusing effect in laboratory. In addition, in order to interpret the wave focusing performance behind the structure, a numerical procedure by the hybrid element method is used on the basis of the conventional mild slope equation but modified and extended to allow for steeper bottom slopes and higher curvature. The modified refraction and diffraction provide additional mechanism for wave height amplification and the maximum amplification for triple crescent structure is presented. It also allows for the possibility of wave energy scattering with the change of the incident wave direction. Comparisons with previous theoretical results involving a submerged crescent shape structure are described.

• Ocean and Polar Research
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• v.23 no.2
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• pp.109-119
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• 2001

Meiobenthic community structure of tidal flats near the Yeonggwang Nuclear Power Plant have studied during summer (June) and fall (October) 1997. Examination of sediment samples collected along the transects showed that there were 18 different types of meiobenthos in the study area. The most abundant meiobenthic animals belonged to Phylum Nematoda in both seasons and all transects. However, sediment samples collected near discharge areas, transects A and B, showed relatively lower abundance than other general coastal areas. Another abundant meiobenthic organism is benthic Harpacticoids which is very sensitive to any environmental changes. Polycheats and Ostracods were next abundant meiobenthos which also showed the difference between the study area and other general coastal areas. Only transect C maintained similar meiobenthic abundance and diversity to other coastal areas. Horizontal distribution for transects A and B showed higher densities in upper and mid tidal flat zones. On the other hand, transect C which is located furtherest from the discharges showed an increasing trend in abundance from upper to lower areas. For size distribution analyses showed that animals which fit into the meshsize of 0.125 mm were abundant, Vertical distribution of meiobenthic animals within the sediments for both sampling seasons showed the highest individual numbers in the surface sediment layers of 0-1 cm depth and showed a decreasing trend as sediment gets deeper. Each class of meiobenthos had different vertical profiles. When comparing survey transects A and B with other similar tidal flat areas, this sites seems to a very unstable environment of tidal flats near the Yeonggwang Nuclear Power Plant.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.92-96
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• 2001

Although the problem of seawater intrusion at the coastal aquifer was recognized before over one hundred years at the coastal aquifer, much groundwater keep on being salinitized by several reasons such as groundwater exhaustion, coastalline change, and human activities. The horizontal and vertical electrical soundings and geostatistical methods were used to define the local characteristics of saltwater intrusion and to estimate the saltwater interface in the southeastern area of the Pusan City. The 24 points of the Schlumberger vertical electrical soundings(VES) to loom depth and the 2 lines of dipole-dipole horizontal soundings are peformed. The resistivity data have lognormal distributions. The horizontal extents of saline water intrusion were estimated from the inversion of horizontal prospecting data. Lognormal ordinary kriging is used in A-A' resistivity profiles on May and July because the data have stationary models in semivariograms. Lognormal IRF-k kriging is used for the isopleth maps using vertical resistivity data. The 10 ohm-m resistivity line on the isopleth maps of 21m, 30m, 50m, and 70m depth using resisitivity data measured in July is sifted to the east, cpomparing that of the isopleth maps measured in May. The kriged vertical and horizontal resistivity isopleth maps suggested that the geostatistical methods can be used to define the variation of earth resistivity distribution at the saltwater interface.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.444-455
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• 2009

Great concerns on geotechnical risk & hazard assessment have been increased due to human and economic damage by natural disasters with recent global climate changes. In this paper, geotechnical problems in particular, landslides which is interested in European countries and North America, were mainly discussed. For these, 18 key topics on geotechnical risk and hazards which had been discussed at the LARAM 2008 workshop in Italy were analyzed after grouping by subjects. Main topic contents consisted of applications such as field measurement, early warning systems, uncertainty analysis of parameters using radar, optical data and statistical theory and so on. And the problems related to analysis of vulnerability and deformation due to earthquakes, investigation of gas zone using seismic reflection data in a landslide area, risk quantification and hazard assessment of landslide movements and multi-dimensional analysis for stability of complex slopes were attracted. Also, there were studies on risk matters of cultural heritage, the blockglide of clayey ground, simulations of debris flows based on GIS, quantification of the failure processes of rock slopes, a meshless method for 3D crack modelling, and finally risk assessment for cryological processes due to global warming.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.43-55
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• 2018

The biggest change in the field of coastal ship safety control since the accident of passenger ship Sewol has been the introduction of the maritime safety supervisor system. With its introduction, the safety control system in coastal passenger ships was changed from consisting of operation managers and marine police to operation managers and a newly-introduced maritime safety supervisor. The safety control system for coastal cargo ships was also converted from relying on ship inspection officers to having a maritime safety supervisor and ship inspection officers. However some negative elements have surfaced due to confusion related to the scope of work in the coastal cargo shipping field. These have been caused by dividing the supervisory agency, a lack of work continuity given non-permanent public official status, low supervisor qualifications overlooking reality, and limitations of the order for improvement to secure seaworthiness. It is essential that the maritime safety supervisor system be solidified to reinforce coastal ship safety control. Therefore, systematic safety control in the coastal cargo shipping industry should be conducted by a single, integrated government agency, and the area covered by the order for improvement to secure seaworthiness should be extended. Also limitations of the supervisor recruitment system due to non-permanent public official status should be simultaneously improved. In addition, it is necessary to upgrade supervisor qualifications to require experience with surveyors of international class, ship captains, and chief engineers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.2
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• pp.174-184
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• 1996

In the present study, for fully-open rectangular harbors, sensitivity analyses are made for the major parameters which are relevant to the practical application of a hybrid element model widely used fur the analysis of harbor oscillation. The results show that it is desirable to extend the finite element region to the area in which depth change is not large and that it is appropriate to take the depth of the outer region for analytic solution as the average along the boundary between the two regions. It is expected that the number of Fourier components of the analytic solution may not be important for a constant-depth simple-shaped harbor but its significance may increase for harbors of varying depth and complex geometry. It is found that the effect of incident wave direction is not significant for the first resonance mode but its effect becomes important as the bottom slope increases, especially for the higher resonance modes.

• Proceedings of KOSOMES biannual meeting
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• 2003.11a
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• pp.167-174
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• 2003

Oceanic conditions of the Tsushirm Wann Current (1WC) region in the southern area if the East Sea (the Japan Sea) are examined using data obtained from a CREAMS (Circulation Research if the East Asian Marginal Seas) cruise in June 1996. In 1990s, a lower temperature appears in $19\%$ and in this period, two branch of the TWC exist and the first branch of the TWC flows inshore if the Japanese coastal region compared to tfr1t in the other years, especially in the sfr1llower water layer at less th:1n about 2mm. The TWC cored with the higher salinity (>34.6 psu) is clearly observed over the continental shelf zone in the Japanese coastal region and offshore and identified by geostrophic calculation Intrusion if the TWC into the East Sea through the Korea Strait (the Tsushima Strait) makes the density structure in the water column change and the water mass in the TWC region is unstable based on Brunt- Vaisala frequency.

• Korean Journal of Agricultural and Forest Meteorology
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• v.14 no.4
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• pp.179-188
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• 2012

A kiwifruit cultivar 'Hayward' has been grown in Jeju Island where the current climate is suitable for growth and development of this crop. Prediction of the geographical shift in the phenology can help the kiwifruits growers to adapt to the local climate change in the future. Two phenology models (i.e., chill-day and DVS) were parameterized to estimate flowering date of kiwifruits 'Hayward' based on the data collected from field plots and chamber experiments in the southern coastal and island locations in South Korea. Spatio-temporally independent datasets were used to evaluate performance of the two models in predicting flowering date of 'Hayward'. Chill-day model showed better performance than DVS model (2.5 vs. 4.0 days in RMSE). Daily temperature data interpolated at a higher spatial resolution over Jeju Island were used to predict flowering dates of 'Hayward' in 2021-2100 under the A1B scenario. According to the model calculation under the future climate condition, the flowering of kiwifruits shall accelerate and the area with poor flowering might increase due to the warmer winter induced insufficient chilling. Optimal land area for growing 'Hayward' could increase for a while in the near future (2021-2030), whereas such areas could decrease to one half of the current areas by 2100. The geographic locations suitable for 'Hayward' cultivation would migrate from the current coastal area to the elevated mountain area by 250 m.