• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.23 no.6
• /
• pp.482-488
• /
• 2011

Seadike is a coastal structure constructed in the rear region of the foreshore to maximize its usability by preventing direct effect of wave. The expected construction field is determined under the design wave and tidal condition where minor wave overtopping is anticipated. Thus, the location of seadike is generally fixed at the highest site of the surrounding area with seadike crest height controlling the permissible range of wave overtopping volume. But a lot of times, frontal sand beach of the seadike continuously deforms due to incident waves, resulting failure in maintaining its initial slope. The erosion and deposition of the seadike front cause changes in the crest height and volume of wave overtopping and decrease in the setting depth of the seadike, which endangers seadike region as a result. In this study, the relation of local scouring and setting depth of the seadike front in the run-up region is examined by using 2D hydraulic model tests and numerical simulations by modified SBEACH model. As a result, the study learned that if appropriate boundary condition is applied to the modified SBEACH model, it is possible to create practical estimations on the local scouring at the seadike foot when erosive waves flow into the region.

• Geophysics and Geophysical Exploration
• /
• v.13 no.4
• /
• pp.349-356
• /
• 2010

Analysis of high-resolution seismic profiles acquired from the southeastern continental shelf of Korea reveals that the late Quaternary transgressive deposits consist of six seismic units created in response to sea-level rise. These units with different seismic facies and geometry can be grouped into two distinct depositional wedges (paralic and marine) bounded by a ravinement surface. The paralic component underlying the ravinement surface consists of the sediment preserved from shoreface erosion and contains incised-channel fill, ancient beach-shoreface deposit and estuarine deposit. The top of paralic unit is truncated by a ravinement surface and overlain by marine component. The marine component consists of the sediment produced through shoreface erosion during landward transgression and contains mid-shelf sand sheet, mid-shelf sand ridge and inner shelf sand sheet. Such transgressive stratigraphic architecture of six sedimentary units is controlled by a function of lateral changes in the balance among rates of relative sea-level rise, sediment input and marine processes at any given time.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.32 no.1
• /
• pp.39-47
• /
• 2020

In order to investigate current characteristics at the Gungpyung beach, which is a macrotidal flat, field measurements were carried out in the summer and winter at the intertidal and the subtidal zones. The distribution of residual current at intertidal flat was dominant in the northward direction in the summer and dominant in the northward and southwestern directions in the winter. The direction and speed of the residual current in the winter are highly correlated with the significant wave height, and the turbidity is also highly correlated with the significant wave height. Therefore, in the winter, high sediment rates are suspended by high waves, and sediments are transporting due to the residual current in the southwest direction. On the other hand, it is expected that the northward residual current is predominant due to the small wave in the summer, and sediment transport does not occur largely due to less suspended sediments. In addition, sediment transport in the southern direction is blocked by the dock, which is the artificial structure, and the erosion occurs in the south side of the dock. The erosion pattern in the macrotidal zone of Yellow sea is dominated by seasonal waves, and blocking of sediments by artificial structure is very important.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.33 no.6
• /
• pp.308-320
• /
• 2021

An integrated sediment management approach that includes the recovery of the amount of declined sediment supply is effective as a fundamental solution to coastal erosion. During planning, it is essential to analyze the transfer mechanism of the sediments generated from estuaries (the junction between a river and sea) to assess the amount and rate of sediment discharge (from the river to sea) supplied back to the coast. Although numerical models that interpret the tidal sand bar flushing process during flooding have been studied, thus far, there has been no study focusing on the formation and development processes of tidal sand bars. Therefore, this study aims to construct wave deformation, flow regime calculation, and topographic change analysis models to assess the amount of recovered sediment discharge and reproduce the tidal sand bar formation process through numerical analysis for integrated littoral drift management. The tidal sand bar formation process was simulated, and the wave energy and duration of action concepts were implemented to predict the long-term littoral movement. The river flux and wave conditions during winter when tidal sand bars dominantly develop were considered as the external force conditions required for calculation. The initial condition of the topographic data directly after the Maeupcheon tidal sand bar flushing during flooding was set as the initial topography. Consequently, the tidal sand bar formation and development due to nearshore currents dependent on the incident wave direction were reproduced. Approximately 66 h after the initial topography, a sand bar formation was observed at the Maengbang estuary.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.16 no.2
• /
• pp.108-119
• /
• 2004

The breakwater extension at Anmok Harbor has resulted in erosional stresses along the wide range of shorelines immediately south of the harbor. In this study, therefore, the downdrift affects caused by the breakwater extension are investigated through both analytical and numerical approaches. In addition, this study stresses the need of monitoring and analysis system for the effective integrated coastal zone management and shows through the case study of Anmok Harbor how the numerical experiments are accomplished for the coastal zone management. The numerical model system, which predicts the seabed changes obtained from the difference between the rates of sediment pickup and settling due to gravity, is combined with the wave, wave-induced currents, and suspended sediment transport models. A new relationship between the near-bed concentration and the depth-mean concentration, which is required in estimating the settling rates. is presented by analyzing the vertical structure of concentration.

• 한국해양학회지
• /
• v.28 no.4
• /
• pp.339-346
• /
• 1993

Due to the natural increase of human population and the concentration of industrial complexes to coastal area, the uses of nearshore area were increased drastically, and the tendency will not stop for a while. Therefore, the loss of human life and property damages of the present days for a disaster of the same magnitude should be heavy as compared to those of the past. For the better utilization of the sea and the prevention of the frequent marine natural and man-made disaster, and for the preparedness for the ocean pollutions, through ocean researches are required. the circulation, tidal currents, storm surges, sea surface wind, waves and sea fogs of the Yellow Sea should be investigated first from the oceanographic point of view, and then the dispersion and diffusion of spilled oil and pollutants, beach erosion, red tide, and longterm sea level oscillations can be studied. International cooperation is crucial for the investigation of the sea because of the temporal and geographic scales of the oceanic phenomina.

• Journal of Ocean Engineering and Technology
• /
• v.24 no.2
• /
• pp.18-24
• /
• 2010

Submerged rubble structures include artificial reef and the mound part of the rubble mound breakwater. Artificial reef is a type of the submerged wave absorbing structure installed in a coastal zone to prevent beach erosion and designed to initially reduce the energy of incoming waves so that its run-up height and overtopping quantity can be decreased. In order to ascertain the stability of such submerged rubble structures, minimum weight of the rubble has to be calculated first from the incoming wave height using Hudson's formula or Brebner-Donnelly formula. Based on the calculated minimum weight, a model is built for use in a hydraulic model test carried out to check its stability. The foregoing two formulas used to calculate the minimum weight are empirically derived formulas based on the result of the tests on the rubble mound breakwater and it is, therefore, difficult for us to apply them directly in the calculation of the minimum weight of the submerged structures. Accordingly, this study comes up with a numerical simulation method capable of deformation analysis for rubble structures. This study also tries to identify the deformation mechanism of the submerged rubble structures using the numerical simulation. The method researched through this study will be sufficient for use for usual preparations of the design guidelines for submerged rubble structures.

• Journal of The Geomorphological Association of Korea
• /
• v.20 no.3
• /
• pp.27-39
• /
• 2013

This study grasped long-term changing tendency of shoreline during lately about 30 years in five region of South East coast, and analyzed long-term changing tendency of East coast shoreline and the factors that synthesized studies of Central and South East coast. As a result of calculating of shoreline variations using DSAS, each shoreline of Mangyangjeong and Josa region regressed mean 28.9m and 6.4m, but each shoreline of Goraebul, Daejin and Bonggil region progressed mean 25.0m, 10.6m and 18.8m. Synthesizing changing tendency of East coast shoreline, 1) progressive and regressive zones of shoreline in all regions seem to repeat. 2) looking at shoreline of south zone adjacent to lately constructed or extended breakwater progressed, because it is thought due to effect of a longshore current flowing north. 3) zones using beach relatively tends to regress shorelines. 4) progress and regress of shoreline in zones including estuary of stream are various features as change of deposit supply from a upstream region.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.35 no.6
• /
• pp.164-172
• /
• 2023

The grain size distribution of sand provides crucial information for understanding coastal erosion and sediment deposition. The commonly used sieve analysis for grain size distribution analysis has limitations such as time-consuming processes and the inability to obtain information about individual particle shapes and colors. In this study, we propose a grain size distribution analysis method using smartphone digital images, which is simpler and more efficient than the sieve analysis method. During the image analysis process, we effectively detect particles from relatively low-resolution smartphone digital images by extracting particle boundaries through image gradient calculation. Using samples collected from four beaches in Gyeongsangbuk-do, we compare and validate the proposed boundary extraction image analysis method with the analysis method that does not extract boundaries, against sieve analysis results. The proposed method shows an average error rate of 8.21% at D₅₀, exhibiting a 65% lower error compared to the method without boundary extraction. Therefore, grain size distribution analysis using smartphone digital images is convenient, efficient, and demonstrated accuracy comparable to sieve analysis.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.2
• /
• pp.117-126
• /
• 1999

Hampyong Bay is a semienclosed and macrotidal bay which opens to the eastern Yellow Sea through a narrow inlet in the southwestern coast of Korea. In order to understand the tidal-flat sedimentation in the semienclosed setting, morphology, sediments, accumulation rate and sea cliff erosion were investigated in the tidal flat of Hampyong Bay. The tidal flat of Hampyong Bay lacks intertidal drainage systems, and generally shows the concave-upward profile whose relief is designated by marked morphological features such as high-tide beaches, intertidal sand shoals and tidal creeks. Surfacial sediments of the tidal flat mainly consist of mud, sandy mud, gravelly mud, gravelly sand and muddy gravel, thus showing the textural characteristics of multimodal grain-size distribution, poorly sorting and positive skewness. The sediments generally coarsen landward due to the increase in coarse fraction content. Sedimentary structures are deeply bioturbated, but parallel lamination and lenticular bedding are locally found in the mudflat near mean low water line. Annual accumulation rates across the tidal flat (along Line SM) average -5.2 cm/yr with a range of -45.8~+4.2 cm/yr, indicating that the tidal flat is erosional. In general, erosion rates of upper and lower tidal flat are higher than those of middle tidal flat. Seasonally, the erosion rates are much higher during spring and winter when dominant wind direction corresponds to the long axis of Hampyong Bay. Sea cliffs are eroded at a rate of 1.4 m/yr. The biggest sea cliff erosion generally occurs 1~2 months later after tidal flats were extensively eroded. Such erosions of tidal Oats and sea cliffs in the semienclosed bay setting are interpreted to be due to wind waves coupled with local sea-level rise.