• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.296-304
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• 2010

The shoreline change caused by the construction of shore protection structures are discussed based on the example of Youngrang coast, Sokcho where the coastal erosion control system(CECS), three artificial headlands and two submerged breakwaters are being constructed. The study qualitatively analyzed the shoreline changes of Youngrang coast using available satellite/aerial photographs and camera photographs taken during the construction period of 6 years since 2002 for the artificial headlands construction. The main results from the study are as following. (1) Before the installation of the middle artificial headland, longshore drifts along Youngrang coast are transported in the NW-SE direction according to the seasonally different wave characteristics. (2) During the CECS construction the shoreline is continuously changed by altering the local longshore drift budget. Especially, the middle artificial headland induces considerable change of shoreline by blocking the sediment supply from the southern pocket beach to the northern pocket beach and by accelerating the sediment accretion at the wave shadow zone behind its head. It induces the asymmetry on the net longshore drift causing the significant erosion at the center of the southern pocket beach. (3) The study demonstrates that serious unintended erosion/accretion problem are possibly occurred due to local changes on the wave transformation and the sediment transport by the construction of coastal erosion control system.

• Journal of the Korean Geographical Society
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• v.40 no.4 s.109
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• pp.416-427
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• 2005

This paper aims to investigate morphological changes of deltaic barrier islands in the Nakdong Estuary and especially their spatial variations after barrage construction. We analyzed shorelines, geometrical centroids, and areas to reveal the changes of barrier islands. Here, we suggest three interesting points from this study. First, each individual barrier island in the Nakdong estuary goes through a different stage of the geomorphic cycle. The frontal barrier islands such as Sinja-do and Doyo-deung grow because they are located in front of the gates of the barrage. Sediments in water out of the gates are moved to offshore and then reworked by coastal processes such as waves and tides. Second, on the contrary, Baekhap-deung located behind Doyo-deung now diminishes indicating that sediments mainly move to the frontal growing island. Third, there is no morphological change in several barrier islands far away from the main flow of the Nakdong river such as Jinwoo-do, Daema-deung, and Jangja-do. In conclusion, barrier islands in the Nakdong estuary show distinct spatial variations. As a barrier island is closer to the main channel or is in the frontal location, there happens a very dynamic change in the morphology of the island.

• Economic and Environmental Geology
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• v.41 no.2
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• pp.243-252
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• 2008

The Iho and Hamdeok beaches, the major coastal beaches in Jeju Island, have been studied through size analysis and using an experimental extension pole and sediment trap in beach profile, in order to understand their textural characteristics, migration patterns, and seasonal change in beach geometry. The Iho beach is composed of coarse and medium sands, 590 m in total length. The foreshore slope is 12.3$^{\circ}$ in summer and 10.8$^{\circ}$ in winter, which shows more steeper in summer. The Hamdeok beach consisting mostly of shell fragments is 950 m long, $5.7{\sim}7.4^{\circ}$ steep and 97.4${\sim}$114.5 m wide, respectively. The suspended load drift concentrations in the studied beaches showed 4.5 mg/l during the period of summer and 33.2 mg/l in winter, and those of fine-grained sediments are derived mostly from the marine of northeastward direction. The typical beach transformation of the Iho beach is resulting from the construction of jetties in the west side that built up the sand inside the jetties, whereas the erosion is occurring on the east side of beach. The center and berm sides of the sand in the Hamdeok beach drift into the dune side during the period of the stormy winter season.

• Journal of the Korean association of regional geographers
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• v.22 no.1
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• pp.211-224
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• 2016

Natural lakes are estimated in variety with that's function or value depending on age environment or geographical characteristics. There are many kind of natural lakes, but the kind of natural lake is limited in rivers in korea flowing into East Sea. However, Yeonho lake in Uljin has different geographical characteristics with oxbow lake or lagoon which is common in korea's river flowing into East Sea. Therefore the purpose of this study is to analyze geographical characteristics due to the process of Yeonho's formation. Further more research for protecting wetland is needed to adequately preserve, depending on the geomorpologic process. To analyze geographical characteristics, it was essential to compare and analyze topographical map of 1918 1956 2012 and I pictured estinated line of bedrock and longitudinal section of Nam-dae cheon(Riv) Yeonho cheon(Riv). In addition, I denoted flooded areas through design flood level of Nam-dae cheon(Riv) Yeonho cheon(Riv) and analyzed particle size distribution of deposited sediment due to consider deposit environment. The results of study are as follows. In conclusion, Yeonho lake is floodbasin which was not researched at river flowing into East Sea. Through this study, my opinion is that floodbasin can be formed in the river that is steep and short. I argue that preservation methods will be seeked by geomorphologic process of floodbasin and development of downtown.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1058-1062
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• 2007

본 연구에서 이동상 모래하천에서 식생의 변화과정을 연구하였다. 연구 대상 하천은 낙동강 상류 하회지구를 대상으로 하였다. 이 지역은 우리나라에서 대표적인 모래하천으로서 지형적인 요인으로 형성된 사행하천의 만곡부에 해당하고 있다. 특히 상류에 댐과 취수보 등 수자원개발시설이 건설되면서 수십 년 동안 물과 유사의 공급이 조절되어 안동시권역에서부터 하류방향으로 향하면서 점차 바뀌어 가고 있는 실정이다. 이 가운데, 이동성을 지니고 있던 사주부에 식생이 유입되고, 식생역이 확장되면서 사주가 고정화되는 경향을 보이고 있다. 이러한 이동상 하도에서 이동사주내 식생역의 발달과정을 파악하기 위하여 사주내 토양의 물리화학적 조사를 수행하였다. 연구 결과, 안동 하회지구내 모래사주에서 식생이 정착 발달 확장 되어가는 과정을 파악할 수 있었다. 하회지구의 식생역의 발달은 시기적으로 홍수기와 비홍수기의 반복적인 출현에 영향을 받고 있었다. 그리고 공간적으로는 홍수기 동안의 유사의 퇴적과 세굴과정과 밀접한 관련이 있는 것을 확인할 수 있었다. 식생역의 확장과정은 이러한 시공간적 상황으로 인해 유발되는 토양의 물리화학적 특성과 높은 상관성이 있음을 확인할 수 있었다.

• Journal of Korea Water Resources Association
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• v.33 no.2
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• pp.181-193
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• 2000

This paper presents the flow and the suspended sediment movement over ripples for oscillatory flows. A new numerical model system is developed, and applied to a laboratory experimental condition of regular waves and a fictitious condition of irregular waves. The flow field is obtained from a programme proposed by Kim et. al.(1994), which is a modified version of SOLA based on SMAC scheme. The sub-model solves the continuity and Reynolds momentum equations in the x-z plane. The wave orbital velocities, shear stresses, and pressure are all reasonably reproduced by the model. The model results on the vertical velocity component show good agreement with the measurements. The suspended sediment transport sub-model is newly set up to solve the advection-diffusion equation of suspended sediment using a split method, and involving a special shear entrainment from the whole ripple surface. The calculated suspended sediment concentrations for regular waves show reasonable agreement with measurements at Deltaflume. The model results for random waves show that the suspended sediment concentration is higher than those for regular waves and that the sediment diffuses higher than for regular waves with the significant wave height and the peak wave period of the irregular waves.

• Journal of The Geomorphological Association of Korea
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• v.19 no.1
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• pp.29-40
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• 2012

The sand dunes at the lower reach of the Duman river indicate that their distribution patterns and directions conform to the dominant northwestern winter wind. On the riverbed of the Duman river at the surroundings of sand dunes form sandy point bars and mid-stream islands. The geomorphic processes of sand dunes can be classified into two types according to the depositional environments via analyses of the sand grain size and stratigraphic profiles. First, the sand dunes of Hoelyongbong, Kyeongshin-Wonjeong, and the riverside areas of the Duman river, have formed by alluvium of the Duman river which deposits and accumulates on the riverbed, then being wind blown to the nearby sand bars, terraces and higher eroded hills. The second type is the active sand dune of the Bangcheon-Nodongja District which develops similarly as to the formation of the first type, but the fixed sand dunes of the district seem to have formed in the underwater condition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.1
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• pp.43-55
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• 1997

Existing theories and experimental results on mud bed consolidation, fluidization and erosion are briefly reviewed. The importance of the history of bed shear strength profile which experiences periodic and random consolidation and fluidization is qualitatively discussed by reanalyzing a field data set in Youngkwang area of Korea. According to the results of existing laboratory experiments and the reanalyzing, the numerical modelling of mud or pollutant transport without considering consolidation and fluidization may cause the time lag between the hydrodynamic forcing and the increment of sediment and bed-originated pollutant concentrations in water column. The time lag can derive serious error in the transport direction, consequently in the budget of a heavy-concentrated bottom-originated substance, especially in macrotidal environments with relatively high wave energy.

• Water for future
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• v.28 no.1
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• pp.107-120
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• 1995

This study is concerned with the hydraulic experiments of Modi Khola Hydroelectric in Nepal. The experimental domain consists of the intake structure and the settling basin. The intake structure was made by the undistorted model with the scale of 1:20, the settling basin by the distorted model with the scale of 1:10(vertical) and 1:15(horizontal). Based on the movable bed model theory, the 'Anthracite'($\rho_s$ =1.48) is chosen as a model material. According to the model tests, the installation of the guide wall with proper height and the proper control of the flushing gate are required for the effective flushing in the intake structure. In the settling basin a more proper design of the inlet in order to constrain the turbulence flow is required for an efficient sedimentation and the installation of another flushing pipe near the maximum sedimental area is required. Since the trap efficiency is measured about 95%, it is concluded that the design of the settling basin is proper.

• Journal of the Korean earth science society
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• v.45 no.3
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• pp.203-213
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• 2024

This study aimed to investigate the seasonal patterns of multiple bar formation in summer and flattening in winter on the macrotidal Sinduri beach in Taean, and to understand the processes their formation and subsequent flattening. Beach profiling has been conducted regularly over the last four years using a VRS-GPS system. Surface sediment samples were collected seasonally along the transectline, and grain size analyses were performed. Tidal current data were acquired using a TIDOS current observation system during both winter and summer. The Sinduri macrotidal beach consists of two geomorphic units: an upper high-gradient beach face and a lower gentler sloped intertidal zone. High berms and beach cusps did not develop on this beach face. The approximately 400-m-wide intertidal zone comprises distinct 2-5 lines of multiple bars. Mean grain sizes of sand bars range from 2.0 to 2.75 phi, corresponding to fine sands. Mean sizes show shoreward coarsening trend. Regular beach-profiling survey revealed that the summer profile has a multi-barred morphology with a maximum of five bar lines, whereas, the winter profile has a non-barred, flat morphology. The non-barred winter profiles likely result from flattening by scour-and-fill processes during winter. The growth of multiple bars in summer is interpreted to be formed by a break-point mechanism associated with moderate waves and the translation of tide levels, rather than the standing wave hypothesis, which is stationary at high tide. The break-point hypothesis for multi-bars is supported by the presence of the largest bar at mean sea-level, shorter bar spacing toward the shore, irregular bar spacing, strong asymmetry of bars, and the 10-30 m shoreward migration of multi-bars.