• 한국해양학회지
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• 제18권2호
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• pp.142-148
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• 1983

錦江河口의 6個定點에서 大.小潮기에 Instantaneous profiling技法으로 同時 觀測한 鹽分値를 분석하여 鹽分境界層의 變化特性을 밝혔다. 錦江河口를 鹽分境界層의 變化特性으로 分流해 본 缺課 定常波型河口(standing wave type estuary)임이 再次確認(Chung, 1981)되었으며 變化의 크기는 上流로 갈수록 커짐도 아울러 밝혀 졌다. 또한 鹽分境界層의 變化는 大潮期 보다 小潮期에 큼도 밝혀 졌다. 鹽分境界層(S<10%)의 持續時間은 小潮期에 越等히 긴데, Shinri-Saugke斷面 보다 上流域에서는 6時間以上 持續되고 Sochgot-Kupo斷面 사이에서는 0-3時間童 顔 持續됨이 밝혀 졌다. 따라서 錦江河口에서의 堆積作用은 持續時間의 分布特性에 따른 區域別의 Flocculation作用의 强弱에 의해 支配되고 있음도 아울러 밝혀 졌다.

• 대한토목학회논문집
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• 제26권1B호
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• pp.15-25
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• 2006

유역형상의 변화에 따라서 이동강우가 유출에 미치는 영향을 운동파이론을 적용하여 분석하였으며, 유역형상은 신장형유역과 정사각형유역 및 장방형유역에 대하여 분석하였고, 이동강우 분포형은 균등분포형, 전진형, 지연형, 중앙집중형을 사용하였다. 이와 같은 형상의 유역에 대하여 다양한 이동속도를 가진 강우가 유역내 하천의 상류방향, 하류방향, 횡방향으로 이동할 때 강우분포형에 따르는 유출수문곡선을 모의하여 그 특성을 비교분석하였다. 유출수문곡선의 모양과 첨두시간, 첨두유량은 시간적, 공간적으로 변화하는 강우와 유역형상에 의하여 크게 영향을 받는다. 횡방향의 이동강우에서는 상류방향과 하류방향의 경우보다 더 큰 첨두유량이 발생하며, 하류방향 이동강우의 첨두유량은 상류방향의 첨두유량보다 더 크게 나타났다. 신장형유역의 경우 하류방향 이동강우의 첨두시간은 상류방향과 횡방향의 경우보다 더 지체되며, 수문곡선의 총유출량과 기저시간은 강우속도가 증가함에 따라 감소하였다.

• Ocean Systems Engineering
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• 제6권1호
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• pp.23-60
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• 2016

The major objective of this study was to develop further understanding of 3D nearshore hydrodynamics under a variety of wave and tidal forcing conditions. The main tool used was a comprehensive 3D numerical model - combining the flow module of Delft3D with the WAVE solver of XBeach - of nearshore hydro- and morphodynamics that can simulate flow, sediment transport, and morphological evolution. Surf-swash zone hydrodynamics were modeled using the 3D Navier-Stokes equations, combined with various turbulence models (${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES). Sediment transport and resulting foreshore profile changes were approximated using different sediment transport relations that consider both bed- and suspended-load transport of non-cohesive sediments. The numerical set-up was tested against field data, with good agreement found. Different numerical experiments under a range of bed characteristics and incident wave and tidal conditions were run to test the model's capability to reproduce 3D flow, wave propagation, sediment transport and morphodynamics in the nearshore at the field scale. The results were interpreted according to existing understanding of surf and swash zone processes. Our numerical experiments confirm that the angle between the crest line of the approaching wave and the shoreline defines the direction and strength of the longshore current, while the longshore current velocity varies across the nearshore zone. The model simulates the undertow, hydraulic cell and rip-current patterns generated by radiation stresses and longshore variability in wave heights. Numerical results show that a non-uniform seabed is crucial for generation of rip currents in the nearshore (when bed slope is uniform, rips are not generated). Increasing the wave height increases the peaks of eddy viscosity and TKE (turbulent kinetic energy), while increasing the tidal amplitude reduces these peaks. Wave and tide interaction has most striking effects on the foreshore profile with the formation of the intertidal bar. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. Beach profile steepness modifies the nearshore circulation pattern, significantly enhancing the vertical component of the flow. The local recirculation within the longshore current in the inshore region causes a transient offshore shift and strengthening of the longshore current. Overall, the analysis shows that, with reasonable hypotheses, it is possible to simulate the nearshore hydrodynamics subjected to oceanic forcing, consistent with existing understanding of this area. Part II of this work presents 3D nearshore morphodynamics induced by the tides and waves.

• ALGAE
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• 제30권2호
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• pp.89-101
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• 2015

Ecklonia cava Kjellman is a common kelp found in shallow subtidal in warm-temperate waters in the northwest Pacific Ocean. This species has shown substantial morphological variation along with subsistence in different locations and local environments. We quantified the magnitude of morphological variation of E. cava from six populations along ~700 km of coastline from Jeju Island to Dokdo in Korea. In addition, we examined genetic distance among the populations using random amplified polymorphic DNA (RAPD) analysis. Most morphological characteristics investigated were significantly different among locations. Multivariate analyses indicated two phenetically distinct groups (nearshore, sheltered vs. offshore, exposed), indicating wave exposure with turbidity are presumably major factors for the separation. With RAPD data, results of Nei's diversity (H) and AMOVA showed considerable variations in within- and between-populations. Pairwise ${\Phi}_{ST}$ and $N_m$ values indicated moderate gene flow between the six locations. Results of Nei's analysis revealed three genetically distinct groups, not consistent with the morphological groupings, indicating that a time gap may exist between morphological and genetic variations. This study also suggests dispersal distance of this kelp may be longer than what is commonly thought and genetic similarity in the populations was largely reflected by the direction of ocean current rather than just geographical distance.

• Ocean and Polar Research
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• 제43권4호
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• pp.307-320
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• 2021

Udo Rhodolith Beach is a small-scale, mixed sand-and-gravel beach embayed on the N-S trending rocky coast of Udo, Jeju Island, South Korea. This study analyzes the short-term topographic changes of the beach during the extreme storm conditions of four typhoons from 2016 to 2020: Chaba (2016), Soulik (2018), Lingling (2019), and Maysak (2020). The analysis uses the topographic data of terrestrial LiDAR scanning and drone photogrammetry, aided by weather and oceanographic datasets of wind, wave, current and tide. The analysis suggests two contrasting features of alongshore topographic change depending on the typhoon pathway, although the intensity and duration of the storm conditions differed in each case. During the Soulik and Lingling events, which moved northward following the western sea of the Jeju Island, the northern part of the beach accreted while the southern part eroded. In contrast, the Chaba and Maysak events passed over the eastern sea of Jeju Island. The central part of the beach was then significantly eroded while sediments accumulated mainly at the northern and southern ends of the beach. Based on the wave and current measurements in the nearshore zone and computer simulations of the wave field, it was inferred that the observed topographic change of the beach after the storm events is related to the directions of the wind-driven current and wave propagation in the nearshore zone. The dominant direction of water movement was southeastward and northeastward when the typhoon pathway lay to the east or west of Jeju Island, respectively. As these enhanced waves and currents approached obliquely to the N-S trending coastline, the beach sediments were reworked and transported southward or northward mainly by longshore currents, which likely acts as a major control mechanism regarding alongshore topographic change with respect to Udo Rhodolith Beach. In contrast to the topographic change, the subaerial volume of the beach overall increased after all storms except for Maysak. The volume increase was attributed to the enhanced transport of onshore sediment under the combined effect of storm-induced long periodic waves and a strong residual component of the near-bottom current. In the Maysak event, the raised sea level during the spring tide probably enhanced the backshore erosion by storm waves, eventually causing sediment loss to the inland area.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2007년도 학술발표회 논문집
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• pp.1737-1741
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• 2007

강우분포형과 유역형상의 변화에 따라서 이동강우가 유출에 미치는 영향을 운동파이론을 적용하여 분석하였으며, 이동강우 분포형은 균등분포형, 전진형, 지연형, 중앙집중형을 사용하였으며, 유역형상은 신장형, 정4각형 및 장방형유역에 대하여 분석하였다. 이와 같은 형상의 유역에 대하여 다양한 이동속도를 가진 강우가 유역내 하천의 상류방향, 하류방향, 횡방향을 이동할때 유출수문곡선을 모의하여 그 특성을 비교분석하였다. 또한 총유출량을 동일하게 하기 이하여 강우강도를 변화한 경우와 강우길이를 변화한 경우의 수문곡선을 비교하였다. 강우강도를 변화시킨 경우, 모든 강우분포형에서 그리고 모든 유역형상에서 첨두유량은 강우이동속도에 따라 점차 커지고 첨두시간이 일찍 발생하여, 기저시간은 짧아 진다. 첨두시간은 상류방향과 하류방향에서는 신장형유역의 경우가 가장 길고 장방형유역이 가장 짧으며, 횡방향에서는 반대현상으로 장방형이 가장 길고 신장형이 가장 짧다. 강우길이를 변화시킨 경우, 상류방향과 하류방향에서는 신장형의 수문곡선의 변화가 가장 크고 장방향의 변화가 가장 작으나, 횡방향의 경우는 반대현상이 생기며, 모든 경우 정사각형의 이동속도에 따르는 수문곡선의 변화는 그 중간임을 알 수 있다.