• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.329-337
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• 2006

A small hydro-power plant operated by cooling water discharged from the power plant is under construction. In this study, the flow characteristics of the effluent channel and the outfall coastal zone in which the facilities are constructed have been measured and analysed. The flow pattern is highly dependent on the effluent discharge and clearly classified as these typical areas; the upstream and downstream areas of the weir, and the outfall coastal zone. The discharge and the width of the channel in the upstream area of the weir are increased step by step, so the water level fluctuation is small. The flow overtopping the weir is rapidly changing and has highly vertical fluctuation patterns after hydraulic jump just below the weir. The flow pattern in the outfall zone is directed toward the seaward direction and the velocity is dominated by the tidal level fluctuation. The mean tidal range in this area is about 10% greater than that of the Tongyeong tidal gauging station and the wave effects are negligible because of the sheltering effects of this area.

• The Korean Journal of Quaternary Research
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• v.13 no.1
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• pp.67-78
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• 1999

In present, the terminal area of the Nagdong River Delta consists of micro-depositional landforms with sand barrier islands, sand bars and tidal flats which are arranged parallel to the present shoreline, and have rapidly shifted toward sea during last 100 years due to human activities such as construction of estuary dam, industrial complex and residential area. To clarify the landform changes of the area, the author traced the morphologic change pattern based on interpretation of air-photos, topographic maps and old Korean traditional map, and the results are as follows ; Based on the Daedongyeojido, one of the old Korean map, published in 1861, the area including upper part of the delta was underlying by sea level except two larger sand barriers, which means the Nagdong River Delta was not completely formed as the present outline of morphology by 1860s. According to the topographic map(1 :50,000) of 1916, the delta resembled to the present morphology pattern was exposed in 1916, and at this time the area was mainly composed of one sand barrier island, four sand bars and tidal flats, which had slowly elongated southwards before construction of the Nagdong River Estuary Dam in 1987. But after 1987, the area has been rapidly and drastically shifted southwards in arrange with one chain of sand barrier islands (Elsugdo -Myeonghodo-Sinhodo ) and four chains of sand bars (first chain ; Jinwoodo -Daemadeung-Maenggeummeorideung, second chain : Jangjado-Baeghabdeung, third chain ; Saedeung-Namusitdeung, fourth : Doyodeung-Dadaedeung) parallel to shoreline. This rapid landform change of the area is now occurring, and is seemed to ascribed firstly, to the construction of the Nagdong River Estuary Dam on Elsugdo in 1987, the Sinho Industrial Complex on Sinhodo and Myeongji Residential Area on Myeonghodo in 1992, secondly, to artificial alteration of drainage channel and consequential breakdown of former energy system between riverflow and tidal-and wave-energy. From these facts, it is inferred that the landform change pattern of the area will continue until a new equilibrium between the factor available to this energy system is accomplished.

• Journal of the Korean earth science society
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• v.22 no.2
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• pp.120-129
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• 2001

A sand shoal (1300 m long and 400 m wide) with an orientation of north-south is formed on the lower tidal flat of Gomso Bay, southwestern coast of Korea. Surface bedforms, sedimentary structures, sedimentation rate, grain size distribution and can-corer sediments have been measured and analysed along the sand shoal proper zone B and its offshore zone A and onshore zone C during the period of 14 months. These three zones can be differentiated based on sedimentological characteristics: A zone - fine sand (3${\varphi}$ mean), linguoid-type ripples, 70 mm/month in sedimentation rate and no bioturbation, B zone - medium sand (2.5${\varphi}$ mean), dunes (4${\sim}$5 m in wavelength), 30 mm/month in sedimentation rate and no bioturbation, and C zone - coarse silt (5${\varphi}$ mean), sinuous-type ripples, 10 mm/month in sedimentation rate and well-developed bioturbation. These characteristics indicate that the zone C represents a relatively low-energy regime environment whereas the zone A corresponds to a relatively high-energy environment. The zone B would play an important role for a barrier to dissipate the approaching wave energy, resulting in maintaining of low-energy conditions in the inner part of Gomso-Bay intertidal flat behind.

• Journal of Navigation and Port Research
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• v.27 no.2
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• pp.233-238
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• 2003

Due to the impermeability of outer wall facilities such as Breakwaters which dissipates the wave energy and keeps harbor tranquility, the enclosed area of harbor becomes partially blocked and the water exchange can be reduced. Recent trends of port development protect water quality and emphasize Water-Front, so the method which enhances the circulation of harbor waters and the dilution of the water pollutants are studied. The best improvement of water quality is a remove of pollutant source on land, but an enclosed port must be enhanced the tidal exchange. For this end, the best improvement may be made a drain-route on the existing outer wall facilities. In this study, the numerical computations were carried out to predict the circulation of harbor waters and the tidal exchange through the drain-rout in the polluted harbor(Samchonpo-guhang) located at the east coast of South Sea. Computational models adopting FDM(Finite Difference Method) were used here and were already verified from the previous studies und ocean survey. As a result of this study, circulation and the tidal exchange at the harbor before and after introduction of drain-route were assessed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.452-455
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• 2009

The Nakdong Delta can be identified by two different geomorphic units. The first one is the upper delta. This is mostly composed of inter-distributary islands that are largely influenced by fluvial processes and attributed to the development of these islands along the river. The other one is the lower delta which is mostly composed of beach ridges. Barrier islands are largely effected by wave processes promoted by the development almost at a right angle to the river. Influenced by the longshore current which flows to the same direction, barrier islands located in the Nakdong river estuary are developing from east to west direction. As a result, the eastern end of the barrier islands are growing toward the north-west direction effected by tidal current which moves toward the same direction. Barrier islands include the Sinho Island, the Jinwoo Island, the Daema deung, the Janga Island, the Baghap deung, the Sae deung, and the Chulsae deung(Doyeo deung). They have orderly emerged from the sea since 1861. Since 2008, a new Deung, a sand dune growing under sea, has been developing rapidly from Chulsae deung to the Dadaepo beach. It made the sailing of small fisher boats impossible. Tidal currents transported a lot of sand and silt around the barrier islands. The landscape of Nakdong river estuary where many barrier islands are distributed will change rapidly affecting land environment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.140-148
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• 2014

A storm surge barrier is a specific type of floodgate, designed to prevent a storm surge or spring tide from flooding the protected area behind the barrier. A surge barrier is almost always part of a larger flood protection system consisting of floodwalls, dikes, and other constructions. Surge barriers allow water to pass under normal circumstances but, when a (storm) surge is expected, the barrier can be closed. Among the various means of closing, buoyant flap typed storm surge barrier which was indicated by MOSE project in Italy is chosen for Masan bay protection, and the motion of the surge barrier under the action of storm surge and wave is examined using FLOW-3D, a computational fluid dynamics software analyzing various physical flow processes. Numerical result shows that storm surge barrier is successfully operated under wave height 3 m, and tidal range 2 m.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.4
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• pp.145-152
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• 2008

The initial wave lengths of tsunamis can be several tens to hundreds kilometers. Thus, the importance of the frequency dispersive effects in proportion to variation of the wave length, and should be properly considered in numerical simulation of tsunami propagation for a better accuracy. Recently, a practical dispersion-correction scheme has been developed by adding dispersion-correction terms(Cho et al., 2007). The new model employing the numerical technique has been verified by comparing numerical results with available analytic solutions, however, the new model has not yet been applied on a real topography. In this study, the new model is applied on a real topography and its applicability is examined. To study the applicability of the new model, two historical tsunami events are simulated for Sokcho, Mukho and Pohang harbors, with the tide gage records. Numerical results, the arrival time and the maximum water level at the tidal stations, are compared with observed data at each harbor.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1191-1201
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• 2014

The rip current warning index function, which estimates the likelihood of dangerous rip current in the real-time rip current warning system operating to help mitigate against rip current accidents at Haeundae beach, was studied. The rip current warning index evaluated as a function of various real-time observations was developed based on Choi et al. (2013b). This study shows a version of rip current warning index improved by including the effect of wave direction and spreadings of frequency-directional spectrum on rip current likelihood. The wave and tidal observations in 2012 at Haeundae coast were applied to the rip current index function, and its performances at several real events found based on CCTV images were presented and analyzed.

• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.54-60
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• 2006

This study discusses characteristic of spatiotemporal changes of the sand barrier in the Nakdong estuarine for the last century, focusing on geomarphologic evolution and mobility of sand barriers in the view of coastal engineering. The Nakdong estuarine, the research subject, has a complexly changing natural environment by interaction between ground and marine elements such as ocean wave, tidal current, sediment, etc. Moreover, recently, unnatural geomorphologic changes (e.g., seaside reclamation, new harbor construction, etc.) has been radically increased in this area with increasing desire for coastal development. Because of this, its sand barrier has developed quite unstable condition. Therefore, to identify the development process of geomorphologic changes in this area, required is a close examination on historical characteristics of spatiotemporal changes of the sand barrier in relation to surrounding seaside reclamation and physical environmental changes. This study, based on the marine charts published in between 1927 and 1995 year, analyzes the length and area of the sand barrier for the last hundred years, and investigates the cause of the changes by looking into the change of water depth for the last two years and doing ocean-physical site observations. In conclusion, the sand barrier of the Nakdong estuarine expands toward the open sea by $7.4{\sim}26m$ in annual average, maintaining a fixed distance of $1,241{\sim}1.279m$, and its area is expected to increase about $2.8km^2$ annually. This is characterized by the wocean wave from the open sea and the discharge of Nakdong River.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.1
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• pp.34-40
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• 1999

Models of beach response due to sea level rise were verified by experiments and potential shoreline retreat around Korea and Japan was predicted. Wave tank experiments demonstrated that not only static retreat by water level rise but also additional retreat by wave action plays an important role in total retreat and additional retreat becomes important on the condition of high waves. The result of long-term analysis of tidal data over past 3 decades shows the tendency toward rise by an average of 1.79 mm/year, which is the result of rise in 29 regions and fall in 12 regions. Based on analyzed rate of long-term sea-level rise, potential shoreline retreats of study area after 50 years were calculated and the result shows serious loss of beach.