• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.409-422
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• 2019

In this study, we carried out the 3D numerical simulation to investigate the hydraulic characteristics of Synchronous Edge wave known as the driving mechanism of beach cusp using the Tool Box called the ihFoam that has its roots on the OpenFoam. As a wave driver, RANS (Reynolds Averaged Navier-Stokes equation) and mass conservation equation are used. In doing so, we materialized short-crested waves known as the prerequisite for the formation of Synchronous Edge waves by generating two obliquely colliding Cnoidal waves. Numerical results show that as can be expected, flow velocity along the cross section where waves are focused are simulated to be much faster than the one along the cross section where waves are diverged. It is also shown that along the cross section where waves are focused, up-rush is moving much faster than its associated back-wash, but a duration period of up-rush is shortened, which complies the typical characteristics of nonlinear waves. On the other hand, due to the water-merging effect triggered by the redirected flow toward wave-diverging area at the pinacle of run-up, along the cross section where waves are diverged, offshore-ward velocity is larger than shore-ward velocity at the vicinity of shore-line, while at the very middle of shoaling process, the asymmetry of flow velocity leaned toward the shore is noticeably weakened. Considering that these flow characteristics can be found without exception in Synchronous Edge waves, the numerical simulation can be regarded to be successfully implemented. In doing so, new insight about how the boundary layer streaming occur are also developed.

• Journal of The Geomorphological Association of Korea
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• v.19 no.1
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• pp.17-27
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• 2012

Coastal dunes help stabilize the coastal landscape and protect the hinterland through dynamic interaction with sand beaches. Sometimes dune erosion occurs during the tropical cyclones, while dune recovery may naturally follow after the event. As the typhoon Kompasu passed through the Korean Peninsula early-September in 2010, it caused a rise in water in association with the storm, wave run-ups, and heavy rains in coastal areas. As the result, coastal dunes along the west coast of Korea were severely damaged during the storm. However, the degree and extent of erosion and recovery of dunes were found to be related with the condition of beach-dune systems including gradients of foreshore and front slope of the dune, sediment supply, vegetation, wind activity, and human interferences. Some dunes retreated landward more and more after the erosional event, while others recovered its original profile by aeolian transport processes mainly during the winter season. Vegetated dunes with pine trees were less recovered after the erosion than grass-covered dunes. In addition, dunes with artificial defense were more eroded and less recovered than those without hard constructions. According to the observation after the severe storm, it is likely that the sand transport process is critical to the dune recovery. Therefore, the interactions between beach and dune must be properly evaluated from a geomorphological perspective for the effective management of coastal dunes, including natural recovery after the erosion by storm events.

• Journal of the Korean Association of Geographic Information Studies
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• v.3 no.2
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• pp.48-60
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• 2000

This study is aimed to clarify the distribution chracteristics of marine terraces and extract the specific surface at Gampo-eup, Gyeongju city on the map of 1:5,000 using GIS. The effects and problems occurred on the process of using GIS were investigated for the research of marine terrace. The longitudinal profile analysis was carried out along the 12 sections on the geomorphic surfaces of the study area, and actually High higher surface(HH-surface) was found over 100m a.s.l., which has not been reported till now. And the occupancy rate could be calculated by substitution on the height between 4m and 87m a.s.l. for each mean slope degree $1-5^{\circ}$ obtained from the actual measuring along four sections. Consequently the lower-I surface was highly reliable to use as the key bed for studying marine terraces. The accurate and detail analysis about the marine terraces is able to be accomplished on the basis of meaningful actual measuring, though its general possible distribution area can be extracted from GIS with the less effort. Namely the quantified results obtained from GIS could offer the basis for the objective analysis of the geomorphic surfaces. And we can look over the landscape and investigate the surfaces with reliefs effectively in relation to the real geomorphology on the study area, where in situ approach is difficult. But the digital map with a large scale should be offered first of all in order to raise the accuracy of the analysis.

• Journal of the Korean association of regional geographers
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• v.13 no.1
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• pp.32-42
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• 2007

In Sagye coast of Andeok-myeon, southwestern Jeju, shore platform of noncohesive Hamori Formation, marine terrace deposit of round gravels, coastal dune composed of shell sand and volcanic sand, and back lake are linked closely with each other. In this paper, the formation process of Sagye coastal geomorphic system analysed by using OSL dating method is as follows: Firstly, Hamori Formation is a horizontal stratum filed up of tuff reworked by submarine volcanic eruption during 3$\sim$7.6 ka BP. Hollow at the boundary between Hamori Formation' flat and Kwangheak Basalt's gentle slope become a back lake when block is appeared over the sea level by uplift. Secondly, while Hamori Formation was laid below sea level, gravels which had been broken and abraded at southwestern rocky coast composed of Kwangheak basalt or been transported through the small stream from adjacent hillslope were deposited in rapid flow environment. Thirdly, deposition of round gravels was ceased by earth uplift, and shore platform was constructed by abrasion process of energy of swash moving forward. As altitude of shore platform is equal to high tidal level of spring tide, compared it with present high tidal level of study area, earth is uplifted about 105m since shore platform was formed. Fourthly, much sandy sediments transported from offshore bottom covered shore platforms and marine terrace deposits. Lighter sediments among sandy sediments was blown to back, formed secondary sand dune since about 500 year.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.4
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• pp.287-294
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• 2012

Sedimentary environment in coastal zone has been changing due to a large number of coastal structures and continuous coastal development. As a result, the environment has been changing. In particular, the economic and environmental damage can occur due to cohesive sediment transport closely related with the fate of pollutants. Due to large sea wall construction the ebb dominance in the Mokpo coastal waters has been clearer. Cohesive sediment transport was simulated by the EFDC model. The simulated SS showed good agreements with the observed SS. From the sensitivity analysis of sediment parameters, we found out that the erosion rate, the critical shear stresses for erosion and deposition, and the settling velocity are important factors in cohesive sediment transport modeling.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.209-210
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• 2001

공장 굴뚝이나 차량과 같은 오염원에서 배출된 오염물질은 대기 중에서 확산과정을 거쳐 수용체(Receptor)에 도달하여 영향을 미치게 되는데, 확산을 결정하는 주요인자로는 오염물 배출조건 및 농도, 대기 기상조건, 주변지형조건, 오염물의 반응성 및 침착성 등이 있다. 대기환경 영향평가 및 대기질 관리성책수립 등을 위해서 복잡한 대기확산 과정을 거쳐서 수용체에 도달하는 오염물질의 농도에 대한 정량적인 값의 추정이 필요하다. (중략)

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.512-519
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• 2015

Although Quaternary marine terraces and onshore paleo-shoreline records provide clues to our understanding for the mode and nature of neotectonics in the Korean peninsula, it cannot be accomplished without knowledge on both independent information of the past sea level records and tectonic deformation field together with precise results of numerical dating for higher terraces. This study reported cosmogenic radionuclides ($^{10}Be$) dating results conducted in higher terraces in the eastern and western coasts of the Korean peninsula. As a result, the measured concentration ratio of $^9Be/^{10}Be$ and the exposure ages were much younger than expected. It implies that either there is possibility of error in experimental processes or the samples experienced a complex exposure history probably included a burial at some stage. Considering the past climatic conditions around the Korean peninsula and a possible complex exposure history after the emergence of marine terrace, the discovery of a suitable study area and a sampling site are an essential part of successful $^{10}Be$ dating technique.

• Korean Journal of Environmental Biology
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• v.35 no.3
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• pp.380-388
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• 2017

Factors affecting spatial distribution of halophytes were analyzed in June 2012 at the Goraebul coastal dunes. In the Goraebul sand dune, distribution of halophytes was divided into three groups. The first group belonging to Elymus mollis, Carex kobomugi, Calystegia soldanella, Ixeris repens and Glehnia littoralis was distributed in the ridge of primary sand dune and dune slack. The second group belonging to Lathyrus japonicus and Zoysia macrostachya was distributed in the dune slack. The third group belonging to Pinus thunbergii, Vitex rotundifolia and Linaria japonicus was distributed in the pine forest of the secondary sand dune. E. mollis, C. kobomugi, C. soldanella, I. repens and G. littoralis was distributed in relatively unstable habitat of sand dunes due to the large amount of sand movement. V. rotundifolia was distributed in a relatively stable habitat. Factors that have the greatest influence on distribution of halophytes in the Goraebul sand dunes are distance from the seashore, topography, and the pine forest. The Goraebul sand dune is a relatively well-preserved area with minimal human intervention. Therefore, different distribution of physico-chemical factors by natural processes is essential to spatial distribution of halophytes than other sand dunes in Korea. Significant natural processes in the Goraebul sand dunes were advance and retreat of coastlines from waves, erosion and sedimentation of sand due to wind and waves, and dispersal of seawater.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.2
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• pp.73-78
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• 2010

Wave energy is dissipated mainly by friction on the seabed until the waves reach the surf zone. Many researchers have investigated the mechanism of wave friction and the bottom shear stress induced by wave motion at a certain point is now well estimated by introducing the wave friction factor related to the near bed velocity given by linear wave theory. The variation of wave energy or wave height over a long distance can be, however, estimated by an iteration process when the propagation of waves is strongly influenced by bed friction. In the present study simple semi-theoretical equation has been developed to compute the variation of wave height for the condition of wave propagation on a constant beach slope. The ratio of wave height is determined by the product of shoalng factor and wave height friction factor (frictional wave energy dissipation factor). The wave height estimated by the new equation is compared with the wave height estimated by the solution of numerical integration for the condition that the waves propagate on a constant slope.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.302-306
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• 1993

Assuming Gaussian distribution of the density difference between a turbulent jet river plume and its ambient saline water, a hydrodynamic solution for the lateral spreading of a river plume is developed. Two advantages can be expected from the assumption we made. Firstly, we need not consider mixing processes in the plume in dealing with this Problem. Secondly, by Putting pressure gradients which can be obtained from the density distribution, into the equation of motion, we can solve them easily. We compared the analytic solution with the fold data of the Nakdong river plume and found reasonably good correspondence.