• 한국해양공학회지
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• 제15권2호
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• pp.33-38
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• 2001

The subsidence characteristics of artificial reef (AFR) in the unsteady flow such as tidal flow were investigated. The scour and subsidence characteristics were confirmed in the steady flow field. In a main study, the interaction of "Flow - Sediment Movement - Structure Behavior" and scou $r_sidence mechanism were discussed int he unsteady flow field. AFR subsidence characteristics was discussed with Reynolds number(Re*), Shields number(Sn*), dimensionless acceleration of flow (af/g) and dimensionless time (t/T). Most of all, the continuous AFR subsidence from the scour was occurred by periodic behavior of AFR. This behavior is result from the asymmetric ground, and is influenced by maximum velocity, duration time and direction of flow.ow.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.157-162
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• 2003

Nakdong estuary is located at south-eastern coast of the Korea. A lot of sediment from upper river were deposited at this area. It has cause many problem such as changes in topography and tidal current. Changes of characteristic of deposition were cause by topographic change of nakdong estuary. Analyzing and evaluating data, we could predict the direction of movement of the sand bar and the growth toward south-eastern of Nakdong estuary. It was caused by decreasing river discharge after construction of Nakdong-kang barrage.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.728-733
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• 2002

The measurement of river discharge is among the most fundamental observations and is necessary for understanding many water-related issues, such as flooding hazards, sediment transportation, and nutrient movement. Traditionally river discharge is estimated by measuring the water stage and converting the measurement to discharge using a stage-discharge rating curve. The possibility of monitoring river discharge from satellites has been largely ignored, because it is difficult to measure water surface information from space with sufficient precision. In this paper, an efficient approach to discharge estimation using mainly satellite data is developed and described. The proposed method, which focuses on the measurement of water-surface width coupled with river width-stage and stage-discharge relationships, is applied to the Yangtze River with good results.

• 한국지반환경공학회 논문집
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• 제16권6호
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• pp.39-43
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• 2015

This study extends the Distributed Temperature Sensing (DTS) application to delineate the saturated zones in shallow sediment and evaluate the groundwater flow in both downward and upward directions. Dry, partially and fully saturated zones and water level in the subsurface can be recognized from this study. High resolution seepage velocity in vertical direction was estimated from the temperature data in the fully saturated zone. By a single profile, water level can be detected and seepage velocity in saturated zone can be estimated. Furthermore, thermal gradient analysis serves as a new technique to verify unsaturated and saturated zones in the subsurface. The vertical seepage velocity distribution in the recognized saturated zone is then analyzed with improvement of Bredehoeft and Papaopulos' model. This new approach provides promising potential in real-time monitoring of groundwater movement.

• 한국제4기학회지
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• 제18권2호통권23호
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• pp.19-22
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• 2004

Seasonal changes of topograpy, sediment grain size and accumulation rate on the Gomso-Bay tidal flat(Fig. 1), west coast of Korea, have studied in order to understand the seasonal accumulation pattern and preservation potential of tidal-flat sediments. Seasonal levelings across the tidal flat show that the landward movement of both intertidal sand shoals and cheiers accelerates during the winter and typhoon period, but it almost stops in summer when mud deposition is instead predominant on the middle to upper tidal flat. Seasonal variations of mean grain size were largest on the upper part of middle tidal flat where summer mud layers were eroded during the winter and typhoon periods(Fig. 2). Measurements of accululation depths from sea floor to basal plate reveal that accumulation rates were seasonally controlled according to the elevation of tidal-flat surface(Table 1) : the upper flat, where the accumulation rate of summer was generally higher than that of winter, was characterized by a continuous deposition throughout the entire year, whereas on the middle flat, sediment accumulations were concentrated in winter realtive to summer, and were intermittently eroded by typhoons. The lower tidal flat were deposited mostly in winter and eroded during summer typhoons. Cancores taken across the tidal flat reveal that sand-mud interlaers resulting from such seasonal changes of energy regime are preserved only in the upper part of the deposits and generally replaced by storm layers downcore(Fig. 3). Based on above results, it is suggested that the storm deposits formed by winter stors and typhoons would consist of the major part of the Gomso-Bay deposits(Fig. 4).

• 한국게임학회 논문지
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• 제15권6호
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• pp.171-182
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• 2015

지형에 대한 기존의 침식 시뮬레이션은 주로 소규모의 지형 변화에 초점을 맞추고 있다. 이 논문에서는 물에 의한 침식과 열적 침식과정을 결합하여 강의 네트워크와 산들로 이루어진 자연스러운 대규모의 지형을 형성하는 방법을 제안한다. 물의 흐름에는 shallow water 시뮬레이션의 파이프 모델을 사용하며, 강물의 줄기가 쉽게 형성되게 하기 위해 속도에 의존하는 침식을, 강줄기 주변에 V자형 골짜기가 생성되게 하기 위해 열적 침식을 적용한다. 시뮬레이션 결과 $K_c$(퇴적물 수용상수)와 $K_v$(속도의존 침식강도)의 값이 적당한 범위에 있을 때만 목적한 모양의 지형이 생성되며, 이렇게 생성된 대표적인 자연스러운 모양의 지형을 예시한다. 또한 기존의 열적 침식 방법의 개선과 $K_c$가 큰 값일 때 발생하는 문제점을 해결할 방안을 제시한다.

• 대한환경공학회지
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• 제32권5호
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• pp.427-436
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• 2010

본 연구는 마산만 특별관리해역 관리범위에 속해있는 총 18개 지점을 선정하여 표층 퇴적물 내 폴리브롬화디페닐에테르(PBDEs)의 공간적 농도분포와 오염경로를 조사하였다. 22개의 PBDE 이성질체가 검출되었으며, BDE-209는 가장 주된 이성질체로 검출되었다. BDE-209와 ${\Sigma}_{21}$PBDEs (BDE-209를 제외한 나머지 이성질체의 합)의 농도범위는 각각 2.32~64.2 ng/g, 0.72~8.24 ng/g이었다. 마산만에서 BDE~209 및 ${\Sigma}_{21}$PBDEs의 공간적 농도분포는 내만에서 외만으로 갈수록 감소하였다. PBDEs의 주오염원은 내만의 유입하천수과 하수처리장 방류수이었다. 마산만에서 PBDEs의 오염 수준을 결정하는 주요 인자는 육상기인 오염원 거리와 해수의 유동에 따른 퇴적물의 이동성 및 특성으로 나타났다.

• Ocean and Polar Research
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• 제35권1호
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• pp.27-37
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• 2013

The western coast of Anmyeondo is open toward the Yellow sea and the northern and southern coasts are sandy and have simple coastlines. In this study, we investigated the spatial distribution and community structure of the macrobenthos that inhabit the sandy shore of Anmyeondo. For the study, we chose 8 sites encompassing 44 stations. In total, we have recorded 62 species, and collected 747 inds./$m^2$ on average. Zonation pattern did not appear because the mean grain size and organic contents of the study sites were similar among the macrobenthos. Polychaetes were most frequently recorded, but amphipods appeared in higher mean density. Macrobenthic community is classified into 3 groups largely based on the density difference among the dominant species and the groups were not influenced by environmental factors. The aggregated distribution of macrobenthos did not show a clear regional spatial difference but exhibited classification pattern emphasizing the density difference of the dominant species. The sandy shores of Anmyeondo are relatively more influenced by waves compared to other regions and the sediment moves more due to strong winds, etc. at low tide. We presume that the movement of sediment resulted in a relatively even sedimentary environment and consequently weakened environmental variables that change with the tide level. We concluded that the macrobenthic community does not show the zonation pattern in the sandy shores of Anmyeondo due to such influences.

• Ocean and Polar Research
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• 제25권4호
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• pp.529-543
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• 2003

Deep-sea surface sediments, acquired from 1997 to 2002 in the Clarion-Clipperton fracture zone of the northeast equatorial Pacific, were analyzed for index and geotechnical properties to provide background information for the design of manganese nodule minor. The sediments were classified into 16 types based on the measured properties and evaluated in terms of miner maneuverabillity and potential environmental impacts arising from mining activities. It was found that the middle part of the study area covered with coarse siliceous sediments is more favorable to the commercial production than the northern part of pelagic red clay. In particular, Area B2 in the middle part is considered the best mining site since it shows the highest abundance as well as it consists mostly of normally to over consolidated (types B, C, D) coarse siliceous sediments that are appropriate for effective minor movement and accompany weak environmental impacts. Taking account of all the analyzed core logs, the average shear-strength values are proposed as a practical guideline fur movements of a manganese nodule miner: 6.0 kPa at 10cm and 7.0kPa at 40cm below the seabed.

• Journal of the korean society of oceanography
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• 제32권4호
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• pp.181-190
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• 1997

A large subtidal sand ridge (Jungang Satoe) in Asan Bay, on the west coast of Korea, was studied in order to understand the morphology and sediment transport trend in a macrotidal setting, by means of analyzing sediment samples, current data, side-scan sonographs and seismic profiles. The ridge is about 15 km long and 2-5 km wide, with a relief of about 15 m. It is elongated in the flow direction of flood (SE) and ebb (NW) tidal currents, but asymmetrical in cross section. The western and southwestern side of the ridge is characterized by relatively gentle slopes averaging 0.4$^{\circ}$, whereas on the northeastern side, relatively steep slopes were mapped with 1.6$^{\circ}$ slope angles. Tidal currents associated with the ridge are very strong; maximum surface velo-cities range from neap values of 50 cm/s to spring values of 130 cm/s. The shear velocities during flood and ebb are strong enough to erode and transport sands on the ridge. Sand waves and megaripples (dunes) are the most common bedforms produced by the tidal currents, which show regional differences in shape and size on the ridge. The distribution pattern of these bedforms in-dicates that the flood tidal currents are dominant on the offshore (northwest) side of the ridge, whereas the onsho.e (southeast) side of the ridge is ebb-dominated. The sand transport path as inferred from bedform orientations is directed toward the ridge crest on the flanks, whereas on the crest, it is near-longitudinal to the ridge axis. The convergent, upslope movement of sands on the ridge flanks appears to be important in sand ridge building and maintenance. A significant ridge migration toward the northeast can be suspected on the basis of the ridge morphology, which may cause offshore hazards for navigation.