• Ocean and Polar Research
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• v.39 no.2
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• pp.159-168
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• 2017

To evaluate the accuracy of UAV photogrammetry for Hyangho coast, eastern coast of Korea, we conducted a field experiment wherein UAV photogrammetry test was repeated three times. Since the Haygho coast is located within a military reservation zone, it was necessary to obtain permission to gain access to the beach and to have sensitive aerial photographs showing military facilities inspected and cropped. The standard deviation of the UAV shooting position between the three tests was less than 1 m, but repeatability of footprint on the ground was low due to wind-driven variability of the UAV pose. Self-calibrating bundle adjustment(SCBA) of implementing non-metric camera calibration was failed in one test. In two tests, the vertical error was twice as large as the pixel size except for those areas that were subject to security inspection and cropping. Given the problems that can arise with regard to the repeatability of the shooting area as well as the possibility of failure with regard to SCBA, we strongly recommend that UAV photogrammetry in coastal areas needs to be repeated at least twice.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.91-107
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• 1995

In this paper, previously proposed mechanisms of generation and maintenance of rip currents are grouped into three broad categories; (1) prismatic topography models, (2) non-prismatic topography models and (3) structural controls by natural and/or constructed features, such as headlands, piers. groins, jetties. etc. The prismatic models can explain the occurrence of a rip current on a planar beach, while non-prismatic model needs undulatory topography inside the surf zone to generate and maintain a rip current. Yet more detailed and thorough studies need to be conducted to include all relevant variables and to clarify the mechanism(s) governing rip current. Next a simple model is presented to predict mean longshore currents behind a longshore bar (or submerged breakwaters) by considering mass transport over the bar and the bar morphology. This hydrodynamic model could be extended to include the sedimentary feedback mechanism.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.2
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• pp.171-181
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• 2002

Among various numerical methods of wave transformations including wave breaking by structure, models using VOF(Volume Of Fluid) method to trace free surface are getting into the spotlight recently. In order to analyze wave transformations and velocity of the wave fields due to the permeable submerged breakwater(PSB), This study applied VOF method to the two-dimensional wave channel installed line-source to generate waves and added dissipation zone to offer a non-reflective boundary. Hydraulic experiments was performed to obtain the application of two-dimensional numerical wave channel. The results of numerical experiments using the two-dimensional wave channel agree well with the experimental data. It was shown that vortices are formed behind the PSB, and in case of the 2-rowed PSB they also are occurred in between PSBs, strongly non-linear waves are developed on the crown of the PSB, and the direction of velocities in porous media is determined by the shape of free surface.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.112-123
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• 2006

Double-peak normal distribution function was suggested as the probability density function of the non-tidal components (NTC) data in Korean coastal zone. Frequency distribution analysis of the NTC data was carried out using hourly tidal elevation data of the ten tidal gauging stations, i.e., Incheon, Gunsan, Mokpo, Jeju, Yeosu, Masan, Gadeokdo, Busan, Pohang, and Sokcho which were served through the Internet Homepage by the National Ocean Research Institute. NTC data is defined as the difference between the measured tidal elevation data and the astronomical tidal elevation data using 64 tidal constituents information. Based on the RMS error and R2 value comparison analysis, it was found that this suggested function as the probability density function of the NTC data was found to be more appropriate than the normal distribution function. The parameters of the double-peak function were estimated optimally using Levenberg-Marquardt method which was modified from the Newton method. The standard deviation and skewness coefficient were highly correlated with the non-tidal constants of the tidal gauging stations except Mokpo, Jeju and Sokcho stations.

• Journal of Environmental Impact Assessment
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• v.19 no.5
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• pp.453-464
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• 2010

We evaluated the status and problems of golf course developments in the southern coast of Korea. It's adjacent waters supports nursery and fishing grounds for commercially-important fisheries species, and various sites are designated and protected as marine protection area(MPA), fisheries reserve, or clean area(blue belt) for producing shellfish. We proposed key assessment items for environmental impact assessment(EIA) and checklists in selecting golf course locations. For the protected areas, we suggest that it is essential to limit golf course establishment while setting a minimal distance from the coast to secure a buffer zone for mitigating the environmental impacts. To efficiently utilize existing regional coastal management plans, it is necessary to diagnose how a golf course development will potentially modify geomorphology and scenery, amplify pollutant loads from non-point sources, and disrupt the functions of coastal ecosystem. Especially, continued monitoring and assesssing input loads of hazardous materials originating from agricultural chemicals should be obligatory. Finally, measures for improving the QA/QC analysis were discussed to enhance reliability of environmental data with respect to golf courses and adjacent coastal waters.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.4
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• pp.83-91
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• 2018

Land reclamation, coastal construction, coastline extension and port construction, all of which involve dredging, are increasingly required to meet the growing economic and societal demands in the coastal zone. During the land reclamation, a portion of landfills are lost from the desired location due to a variety of causes, and therefore prediction of sediment transport is very important for economical and efficient land reclamation management. In this study, laboratory disposal tests were performed using an open channel, and suspended sediment transport was analyzed according to flow velocity and grain size. The relationships between the average and standard deviation of the deposition distance and the flow velocity were almost linear, and the relationships between the average and standard deviation of deposition distance and the grain size were found to have high non-linearity in the form of power law. The deposition distribution of sediments was demonstrated to have log-normal distributions regardless of the flow velocity. Based on the experimental results, modeling of suspended sediment transport was performed using deep neural network, one of deep learning techniques, and the deposition distribution was reproduced through log-normal distribution.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.3
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• pp.152-161
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• 2004

Double-peak normal distribution function was suggested as the probability density function of the tidal elevation data in Korean coastal zone. Frequency distribution analysis was carried out using hourly tidal elevation data of the ten tidal gauging stations, i.e., Incheon, Kunsan, Mokpo, Cheju, Yeosu, Masan, Gadeokdo, Pusan, Pohang, and Sokcho which were served through the Internet Homepage by the National Ocean Research Institute. Based on the RMS error and $R^2$ value comparison analysis, it was found that this suggested function as the probability density function of the tidal elevation data was found to be more appropriate than the normal distribution function. The parameters of the double-peak function were estimated optimally using Levenberg-Marquardt method which was modified from the Newton method. The estimated parameters were highly correlated with the non-tidal constants of the tidal gauging stations.

• Journal of Korean Port Research
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• v.12 no.1
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• pp.75-86
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• 1998

To design a coastal structure in the nearshore region, engineers must have means to estimate wave climate. Waves, approaching the surf zone from offshore, experience changes caused by combined effects of bathymetric variations, interference of man-made structure, and nonlinear interactions among wave trains. This paper has attempted to find out the effects of two of the more subtle phenomena involving nonlinear shallow water waves, amplitude dispersion and secondary wave generation. Boussinesq-type equations can be used to model the nonlinear transformation of surface waves in shallow water due to effect of shoaling, refraction, diffraction, and reflection. In this paper, generalized Boussinesq equations under the complex bottom condition is derived using the depth averaged velocity with the series expansion of the velocity potential as a product of powers of the depth of flow. A time stepping finite difference method is used to solve the derived equation. Numerical results are compared to hydraulic model results. The result with the non-linear dispersive wave equation can describe an interesting transformation a sinusoidal wave to one with a cnoidal aspect of a rapid degradation into modulated high frequency waves and transient secondary waves in an intermediate region. The amplitude dispersion of the primary wave crest results in a convex wave front after passing through the shoal and the secondary waves generated by the shoal diffracted in a radial manner into surrounding waters.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.4
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• pp.302-313
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• 2012

Concentrations of selected heavy metals (Al, Fe, Mn, Cr, Cu, Ni, Zn, Pb, As and Cd) in surface sediments from 96 sites in Masan and Jinhae Bay were studied in order to understand metal contamination. Results show that the surface sediments were mainly enriched by Cu (18-294 ppm), Zn (67-568 ppm), Pb (10-120 ppm) and Cd (0.2-3.5 ppm). The coastal zone of Masan Bay was significantly more contaminated than the non-coastal zone, and spatial distribution pattern suggested additional sources of heavy metal input in the coastal area. The enrichment ratio and geoaccumulation index ($I_{geo}$) have been calculated and the relative contamination levels assessed in the study area. The enrichment ratios of Cu, Zn, Pb and Cd in Masan Bay have been observed to be relatively high. $I_{geo}$ results reveal that the study area is not contaminated with respect to Fe, Mn, Cr and Ni; moderately to strongly contaminated with Cu, Zn and Pb; and strongly to strong contaminated with Cd. The high contents of Cu, Zn, Pb and Cd in the study area result from anthropogenic activities in the catchment area. Based on the eight different sediment quality guideline values from USA (ERL, ERM), Canada (TEL, PEL), Australia/New Zealand (ISQG-high, ISQG-low) and Hong Kong (ISQV-low, ISQV-high), sediment quality of Masan and Jinhae Bay was also assessed and characterized.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.4
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• pp.313-325
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• 2011

Finite element grid system using h-refinement on the Yellow Sea was constructed based on previous study (Suh, 1999b) from 14 K to 210 K and special attention was concentrated on refining the coastal zone. In grid generation, depth change between adjacent points and non-dimensional tidal wave length ratio were considered. As a result approximately a quarter of the total nodes are located nearby 5 m of shallow area. Accurate bathymetry data using 30's and ETOPO1 with open boundary conditions of 8 major tidal constituents extracted automatically from FES2004 have been applied. In tidal simulation a 3-dimensional nonlinear harmonic model was setup and tidal amplification due to changes in vertical turbulent and bottom friction were simulated. In this study not only 8 major tidal constituents but also nonlinear shallow tides $M_4,$, $MS_4$ and long period $M_f,$, $M_{sf}$ were reproduced. It is found that implication of spatial variation of friction coefficient plays a very important role in reproduction of astronomical and shallow tides which are computed by iterative computation of nonlinear terms. Also it should be considered differently with respect to tidal periods. To understand the distribution of tidal asymmetry, amplitude ratio of $M_4/M_2$ and phase differences $2g(M_2)-g(M_4)$ were calculated. Tidal distortion ratio marks up to 0.2 on the west coast showing shallow coastal characteristics and somewhat wide range of ebb-dominances in front of Mokpo area are reproduced.