• Journal of Ecology and Environment
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• v.34 no.4
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• pp.333-345
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• 2011

Aquatic macrophytes, often also called hydrophytes, are key components of aquatic and wetland ecosystems. This review is to briefly summarizes various macrophyte classifications, and covers numerous aspects of macrophytes' role in wetland ecosystems, namely in nutrient cycling. The most widely accepted macrophyte classification differentiates between freely floating macrophytes and those attached to the substrate, with the attached, or rooted macrophytes further divided into three categories: floating-leaved, submerged and emergent. Biogeochemical processes in the water column and sediments are to a large extent influenced by the type of macrophytes. Macrophytes vary in their biomass production, capability to recycle nutrients, and impacts on the rhizosphere by release of oxygen and organic carbon, as well as their capability to serve as a conduit for methane. With increasing eutrophication, the species diversity of wetland macrophytes generally declines, and the speciose communities are being replaced by monoculture-forming strong competitors. A similar situation often happens with invasive species. The roles of macrophytes and sediment microorganisms in wetland ecosystems are closely connected and should be studied simultaneously rather than in isolation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.4
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• pp.80-91
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• 1982

To precict the suspended sediments which are 80% of total sediments in a flood disch- arge, an equation representing vertical distribution of sediment concentration was derived based upon the diffusion theory and the logalithmic velocity distribution function in the tubulent flow mechanism. The hypothesis that the uniform mass transfer is occurred at upper part along the center line of water depth, was established as a preconition to solve the problem. The theorecal and the observed values were compared. And the theoretical equation was modified to be fit the theoretical values the observed values. Observed results are as follow; 1) Equation 12) is the theoretical equation representing the vertical concentration distri- bution of suspended sedimenta 2) Rous&exonential type vertical concentration distribution equation shows signification errors near the water surface. But the equation 12) shows substation cocentration values near the water surface. 3) Equation 15) is the modified theoretical equation which is possible to predict the vertical concentration distribution of suspended sediments.

• The Korean Journal of Malacology
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• v.23 no.1
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• pp.9-16
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• 2007

Data obtained from field observation revealed that the degree of shell bioerosion of the scallop, Patinopecten (Mizuhopecten) yessoensis, by endolithic organisms significantly higher on the muddy sand than on the sand. At the area studied, the polychaete worm, Polydora brevipalpa (=Polydora ciliata brevipalpa, Polydora ciliata Okuda, Not Johnston, Polydora variegata), which is common symbiotic species for the scallop made 95-100% of total scallop shell bioerosion at the area studied. The muddy bottom sediments enriched by organic matter create favourable conditions for development of microphytobenthos and bacteria, which are predominantly consumed by P. brevipalpa. Linear regressions for the degree of shell bioerosion on the scallop shell height, total wet weight and adductor muscle wet weight revealed negative relationships between them for the scallops inhabiting both sand and muddy sand. The influence of polychaetes on scallops is complex. They may be food competitors. Polychaete can directly affect the host through their boreholes. Scallop expends energy for shell regeneration to prevent the polychaete penetration into its interior cavity. It was found that the degree of shell bioerosion increased considerably with scallop age.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.349-352
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• 2007

Estimating the physical properties of the survey area and mapping the geotechnical basement play an important role in ocean engineering and construction field. In this study, we performed marine seismic reflection and refraction survey as an engineering application at shallow marine. We made use of the dual boomer - single channel streamer as a source-receiver in reflection seismic survey and air-gun source - the manufactured OBC(Ocean Bottom Cable)-type streamer in refraction survey. In the seismic reflection data, we could easily find the geological layers and basement. Moreover, seismic refraction data could present sediment thickness and velocity distribution.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.233-233
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• 2019

본 연구에서는 3형식 다공성 인공어초의 국부세굴 발생에 따른 인공어초의 안정성 검토를 위하여 3차원 수치모형인 FLOW-3D의 Sediment 모듈을 적용하여 분석을 실시하였다. 실험파랑 설정을 위하여 인공어초 설치 예정지인 서해 대상해역(대청도, 연평도 인근)의 100년 빈도 설계파랑을 적용하였으며, Bretschneider-Mitsuyasu 스펙트럼 기법을 통하여 파랑을 재현하였다. 원형상격자 조건은 최대 0.1m~2.0m에 해당하며, 수치모형실험 해석 시간을 고려하여 입사파랑의 진행방향으로 인공어초의 1/2 폭에 해당하는 X축(190개), Y축(80개), Z축(110~180개) 영역에 대한 격자조건 설정하고 분석을 실시하였다. 분석은 인공어초 하중에 따른 동적 거동을 반영하는 FSI(Flood Structure Interaction)기법을 적용하였으며, 분석결과 인공어초 구조물 하단의 돌출부분에서 세굴발생이 확인되었으며, 최대세굴심은 3형식 인공어초의 규격 및 단위체적당 중량이 클수록 높게 발생하였다.

• Journal of the Korean earth science society
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• v.44 no.4
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• pp.264-274
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• 2023

The Korea Strait comprises a continental shelf in a shallow sea that experienced glacio-eustastic sea-level changes during the Quaternary period. A long core of 76.6 m in length was acquired at the South Sea Drilling Project site (SSDP-101; 34°19.666'E and 128°16.335'N) with a 60 m water deep. The uppermost massive sand beds were interpreted as sandy sediments of the nearshore marine sand ridge in the shallow sea during the transgression of sea level, whereas the lower parts of alternating sandy and muddy beds were interpreted as deposits in marsh, estuary, and tidal flat environments. A three-layered geoacoustic model was reconstructed for the sedimentary succession in the high-resolution seismic profile based on a 140-grain size and sediment type of core SSDP-101. For the actual underwater simulation and experiments, the in-situ P-wave speeds were calculated using the sound speed ratio of the Hamilton method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.85-96
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• 2016

A series of tests were conducted to examine the filled tube shape with respect to the filling module type used and to investigate cone resistance properties of a dredged-soil-filled geotextile tube under water and drained conditions. Results based on the filling observation showed that the distribution of the accumulated fills inside the acrylic cell and vinyl tubes differs with respect to the type of filling modules. A crater formation around the inlet area was found during the test using I-type filling module and a horizontal sediment distribution was found during the test using inverse T-Type filling module. The dredged fill material was obtained from the Saemangeum area. The geotextile tube deformation of each filling stage was almost converged when the tube was fully drained. The cone resistance of the dredged fill in the geotextile tube under drained condition is large and is approximately 2~6 times that of the tube under water condition.

• Journal of Korean Society on Water Environment
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• v.29 no.5
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• pp.656-665
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• 2013

This research was conducted to investigate pollutant load unit factor from aquacultural farms. Pollutant load unit factors were investigated on the 13 kinds of fish type, i.e., Trout, Leather Carp, Eel, Carp, Cartfish, Freshwater Eel, Crucian Carp, Colored Carp, Sturgeon, Marsh Snail, Sweetfish, Pond Snail, Eriocheir Sinensis. Water qualities in aquacultural farms were investigated wide range of values by fish type and pollutant items. High BOD and COD values were observed at the Leather Carp (Ponded water system), Cartfish (Ponded water system) and Freshwater Eel (Recirculating System). TOC and DOC values were relatively high at the Freshwater Eel (Recirculating System) and Eriocheir Sinensis (Extensive). Eel (Ponded water system) and Freshwater Eel (Recirculating System) produced high concentrated nutrient pollutants, i.e., T-N, T-P. Pollutant load unit factors are dependent on fish type, aquacultural type, water quality items, etc. If some fishes have similar basic unit values, those could be applied for TMDLs as a group of fish having same pollutant load unit. The water quality concentrations of post treatment facilities' (mainly reservoir tank) effluent were higher than those of fish raising bath because of extracting pollutant from sediment in the reservoir tank. Therefore, it needs to the management and regulations about post treatment facilities.

• Journal of Navigation and Port Research
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• v.45 no.3
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• pp.165-172
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• 2021

Breaking wave is one of the important design factors in the design of coastal and port structures as they are directly related to various physical phenomena occurring on the coast, such as onshore currents, sediment transport, shock wave pressure, and energy dissipation. Due to the inherent complexity of the breaking wave, many empirical formulas have been proposed to predict breaker indices such as wave breaking height and breaking depth using hydraulic models. However, the existing empirical equations for breaker indices mainly were proposed via statistical analysis of experimental data under the assumption of a specific equation. In this study, a new Munk-type empirical equation was proposed to predict the height of breaking waves based on a representative linear supervised machine learning technique with high predictive performance in various research fields related to regression or classification challenges. Although the newly proposed breaker height formula was a simple polynomial equation, its predictive performance was comparable to that of the currently available empirical formula.

• Journal of the Korean earth science society
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• v.21 no.2
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• pp.174-187
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• 2000

The Quaternary coarse-grained sandy sediments are distributed along the channels of Seomjin River. The fluvial sediments were sedimentologically studied in horizontal and vertical distributions. To analyze depositional environments and facies changes in the sediments, sediment sampling from river mouth to upper stream and desctriptive approaches to the sediment profiles outcropped near Kurye were carried out. The sediments along the stream lines of the river are assigned to very coarse to coarse sand in grain size. The sediment grains are widely scattered in sorting and moderately sorted in average. For skewness and kurtosis, the sediments ranges from very fine to very coarse skewed and from very lepto-kurtic to extremelyl epto-kurtic states, respectively. The sediments are divided into slightly gravelly sand, gravelly sand and sandy gravel in sediment type. The pain shape in the sandy sediments are dominant in equant and tabular forms showing wide varieties. The sandy sediments are mostly poorly sorted and are highly variable in surface texture with SEM. Some smaller grains in the sediments ordinarily show polished surfaces. Of those grains, quartz ones are commonly angular to surounded. On the basis of facies changes and sedimentary structures, outcropped fluvial sediment profiles in Kurye are classified into xGyS, mGyS, gGyS, xSM, xS, mS, mGyM, IgM in facies. These eight facies are reformed as facies assemblage I and ll. The facies assemblage I and II are interpreted as the products of the channel deposits in braided stream and flood plain ones besides channels, respectively. The change facies assemblage I with facies assemblage ll imply that depositional environments hadbeen migrated from braied sream to flood plain ones.