• Title/Summary/Keyword: Estuaries

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Effects of Wave-Current Interactions on 3-D Flow Fields in a River Mouth (하구에서 파랑-흐름 상호작용이 3차원 흐름특성에 미치는 영향)

  • Lee, Woo-Dong;Jeon, Ho-Seong;Park, Jong-Ryul;Hur, Dong-So
    • Journal of Ocean Engineering and Technology
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    • v.31 no.1
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    • pp.36-46
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    • 2017
  • Most of the studies on the hydraulic characteristics of wave-current interaction have used 2-D hydraulic experiments or 2-D numerical simulations. However, it is difficult to understand the wave-current interaction found in actual estuaries using these. Therefore, a numerical water tank was constructed in this study to perform simulations involving a 3-D river mouth. The result showed a change in the water surface at the river mouth from the wave-current interaction. With an increase in the ratio ($V_c/C_i$) between the river current and wave celerity, the wave height and mean water level of the river increased at the wave and current meeting point. A higher $V_c/C_i$ caused a stronger wave-current interaction and increased the turbulence kinetic energy. Thus, the wave height attenuation became larger by the wave-current interaction with a higher $V_c/C_i$. In addition, it was possible to understand the flow characteristics in the vicinity of the river mouth as a result of the wave-current interaction using the mean flow and mean time-averaged velocity at the mid-cross section of river.

Growth Dynamics of Zostera marina Transplants in the Nakdong Estuary Related to Environmental Changes (낙동강 하구에 이식된 잘피(Zostera marina)의 환경변화에 따른 성장특성)

  • Park, Jung-Im;Lee, Kun-Seop;Son, Min-Ho
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.44 no.5
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    • pp.533-542
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    • 2011
  • Numerous seagrass habitat restoration projects have been attempted recently due to the remarkable decline in seagrass coverage. Seagrass transplants tend to adapt to a new environment after experiencing transplanting stress during the early stages of transplantation. Once acclimated, the transplants grow into healthy seagrass beds via vegetative propagation. The establishment and growth dynamics of transplanted seagrasses in bays and coasts are widely reported, but few studies have been conducted on estuaries in Korea. We transplanted Zostera marina in November 2007 and November 2008 in the Nakdong estuary using the staple method, and monitored the survival, adaptation, and growth dynamics of the transplants as well as environmental factors every month for 1 year. Both transplants adapted well to the new environment without initial losses and showed rapid productivity during early summer. However, density of transplants increased 320% in 1 year from the previous year's transplants but that decreased to 59% during the following year. This significant reduction in density in the second year may have been caused by exposure to low salinity (10 psu) for 3 weeks during the unusually long monsoon season. While the survival and growth dynamics of seagrass transplants planted in bays and coasts are mainly controlled by underwater photon flux density and water temperature, salinity was the critical factor for those planted in Nakdong estuary.

Study on distribution characteristics of brominated flame retardants in sediments (퇴적물 중 브롬화난연제 농도분포 특성에 관한 연구)

  • Kim, Tae-Seung;Shin, Sun-Kyoung;Oh, Jung-Keun;Park, Jong-Eun
    • Analytical Science and Technology
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    • v.25 no.4
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    • pp.242-249
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    • 2012
  • Total 11 samples of sediments from the Geum river and the Nakdong river and its estuaries were analyzed to investigate the distribution characteristics of PBDEs and HBCD. Concentration of PBDEs in sediments ranged from 2.19~101.34 (average 30.70, median 20.91) ng/g-dw. The concentration range of PBDEs in river sediments is greater than those of estuary sediments. The HBCD concentration was ranged from N.D.~7.85 (average 1.47, median 0.32) ng/g-dw. HBCD concentrations compared with PBDEs are approximately 1/20 level, which is associated with low domestic usage. Isomer patterns of PBDEs and HBCD suggested that not only the use of commercial products, but the physicochemical properties of these materials, environmental degradation, and environmental behavior could affect the distribution characteristics of these chemicals and their isomers.

Studies on probability extinction of Peregrine falcon species wintering around Jang Hang wetlands in the Han river (겨울철 한강 장항습지에 서식하는 매 멸종확률 예측에 대한 연구)

  • LEE, Sangdon
    • Journal of Wetlands Research
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    • v.18 no.3
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    • pp.282-285
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    • 2016
  • Peregrine falcon (Falco peregrinus) are listed as endangered species and Natural monument #323 in Korea, and this study examined the possibility of extinct of peregrine falcon in Jang Hang wetland near Han river using with the application of Population Viability Analysis (PVA) technique. In Jang Hang wetland areas population was monitored during 1999-2005 averaging 10.8 individuals and PVA analysis was done for the 5 years (2015-2020) using the average population size. Using the initial population was estimated 20% of extinct rate during the time. This estimation was quite low considering water pollution and loss of habitat. Also PVA only used population size lacking in other life history information. Nonetheless falcon population can be in risk of extinction if the current construction of crossovers in the river, cement bank are maintained. Long term information regarding life history needs essential.

The Distribution and Standing Crop of Phytoplankton at the Estuaries of Galgok Stream and Incheon River in Jeollanam-do (전남 갈곡천과 인천강 하구역의 식물플랑크톤의 분포 및 현존량)

  • Lee, Ok-Min;Yoo, Mi-Sun;Lee, Byung-In;Lim, An-Suk
    • ALGAE
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    • v.23 no.4
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    • pp.257-268
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    • 2008
  • Species composition, standing crop and dominant species of phytoplankton were investigated at 6 sites of Galgok stream and Incheon river which run into Gomso Bay, Jeollanam-do in April, August and November 2007. Total of 210 taxa were found which were classified as 6 classes, 12 orders, 25 families, 66 genera, 177 species, 27 varieties, 5 forms and 1 unidentified species. These river and stream had lower concentration of T-N and T-P compared to that of others; however, the site 2 of Galgok stream in summer was hypertrophic in T-P and also near hypertrophic in TN, and the site 1 in Incheon river during fall appeared to be hypertrophic in T-N, and the site 3 in summer showed near hypertrophic level in T-P. Determining the trophic status of the water quality based on chlorophyll a (chl-a), the site 3 of Galgok stream in spring and the site 3 of Incheon river in fall were oligotrophic; moreover, 6 sites including the site 2 and 3 of Galgok stream in summer were mesotrophic, and 9 sites including all sites of Galgok stream in fall turned out to be eutrophic. Particularly, the site 1 of Galgok stream in summer was hypertrophic, having 58.19 mg chl-a m$^{-3}$. There was a conspicuous difference between two values of standing crops based on chl-a and cell counting. This discrepancy may have occurred because of abundant cyanophytes and exclusion of picoplankton cells in cell counting. In the study, 5 cyanophytes, Synechocystis aquatilis, Microcystis aeruginosa, M. flos-aquae, Oscillatoria angustissima, O. limnetica and 2 diatoms, Thalassiosira bramaputrae and Navicula viridula var. rostellata were abundant. Based on the T-N, T-P values, standing crops and cell counting in Galgok stream and Incheon river were between mesotrophic and eutrophic conditions.

Seasonal Variation of Dissolved Methane Concentration and Flux in the Nakdong Estuary (낙동강 하구의 용존 메탄 분포와 메탄 플럭스의 계절변화)

  • RYU, JEHEE;AN, SOONMO
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.21 no.3
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    • pp.91-102
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    • 2016
  • The spatio-temporal variations of the dissolved methane concentration were investigated and the methane budget was estimated in the Nakdong Estuary in January, September, and November of 2014. Dissolved methane showed seasonal variation (21~874 nM) with high concentration in summer due to enhanced temperature and fresh water discharge. Decreasing trends of dissolved methane from the river to the estuary were consistent in all seasons showing the main source of the estuarine methane is river discharge. However, the decreasing trends were modified seasonally due to the local sources such as organic-rich sediments in intertidal zone or near the estuarine barrage. Dissolved methane concentration in the Nakdong Estuary was high, compared to other estuaries probably due to the well developed wetland in Nakdong-river system and stagnation effect from barrages and dams. Dominant sink for the Nakdong estuarine methane was outflux into the atmosphere. Relatively long residence time (produced by barrier island and estuarine dam) in the estuary might provide the enough time for the outgassing.

Prediction of Long-Term River Bed Changes in Saemangeum Area (새만금지구 장기 하상변동 예측)

  • Jung, Jae-Sang;Song, Hyun Ku;Lee, Jong Sup;Kim, Gweon Su
    • Proceedings of the Korea Water Resources Association Conference
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    • 2016.05a
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    • pp.394-398
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    • 2016
  • Numerical analysis was conducted using Delft3D developed by Deltares in Netherlands to predict long-term river bed changes in Saemangeum Area. Tidal flow, discharge through the drainage gates and river bed changes in numerical model was verified by comparing to the results of field observation and hydraulic experiments. We calculated long-term river bed changes in Saemangeum area for 10 years from 2031 to 2040 after completion of development in Saemangeum. It is shown that 70 cm and 139 cm of accumulation occur in estuaries of Dongjin River and Mankyong River, respectively. Variation of flood level was also investigated considering long-term river bed changes. There was no change in estuary of Dongjin River but maximum flood level in estuary of Mankyong River increased 81 cm.

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Population Trends of Wintering Whooper Swans(Cygnus cygnus) in South Korea: Data from the Winter Waterbird Census Program

  • Choi, Jieun;Kim, Ji Yoon;Do, Yuno;Joo, Gea-Jae
    • Korean Journal of Ecology and Environment
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    • v.51 no.4
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    • pp.365-372
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    • 2018
  • The Wintering Waterbird Census of Korea was started in 1999 and monitors 200 major migratory sites in South Korea. Waterfowl counts have been undertaken for more than 20 years since; however, a limited number of studies have analyzed the temporal patterns of waterfowl population. In this study, we analyzed population size changes of wintering whooper swan (Cygnus cygnus) at 112 monitoring sites from 2001 to 2018. The average number of whooper swans was $4,296{\pm}42.66$ and there was a trend for an increase in population size across the survey period. We found that the population in the Nakdong River Estuary, one of the major wintering sites over 18 years (26.22% of the national population), had rapidly decreased (-0.77% per year). Conversely, the whooper swan population in the Junam Reservoir and Sihwa Lake increased (+1.64%, +0.54% per year, respectively). Estuaries showed the highest dominance of whooper swans among the five different habitat types, accounting for 32.13% of the population. Reservoir/lakes had 30.60% of the total population and reclaimed lakes(18.24%), river (13.11%), and coast (5.93%) followed. The annual distribution of the whooper swan population in South Korea has been affected by various habitat conditions resulting from human activities and urbanization. To better understand the complex factors that can cause rapid changes in wintering waterfowl populations, it is necessary to integrate the data from the bird census program with environmental conditions to conduct in-depth pattern analyses over longer time periods.

Distribution of Fish Species in Wetland Protected Areas in South Korea

  • Chu, Yeounsu;Yoon, Jungdo;Cho, Kwang-Jin;Kim, Mijeong;Lim, Jeongcheol;Lee, Changsu
    • Proceedings of the National Institute of Ecology of the Republic of Korea
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    • v.2 no.1
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    • pp.42-52
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    • 2021
  • In order to secure basic data on biodiversity for wetland conservation and management used the data from Wetland Protected Area surveys conducted in South Korea (2015-2019) to analyze the distribution of fish from a total of 15 orders, 45 families, 134 species, and 12,972 individuals. The predominant species identified were Zacco platypus (Temminck and Schlegel) (19.47%) and Zacco koreanus (Kim, Oh and Hosoya) (8.16%). Of all emergent species, 52.9% (n=71 species) were freshwater species, 26.9% (n=36) were brackish species, 3.0% (n=4) were migratory species, 27% (n=36) were marine species, and 9.0% (n=12) were riffle benthic species. Overall, 5.2% (n=7 species) were endangered species, 3.0% (n=4) were exotic species, and 23.1% (n=31) were Korean endemic species. The eight identified Wetland Protected Areas (WPA) were classified based on their habitat characteristics and on the analysis of their emergent fish communities, as estuarine (n=2), coastal dune (n=1), marsh (n=2), stream (n=2), and stream-marsh (n=1) types. The environmental factors revealed to have the greatest influence on the species diversity of emergent fish were maintenance and repair, installation of reservoirs, and construction of artificial wetlands around them. The present study offers basic information on the diversity of fish species in different Wetland Protected Area types that can be used to inform conservation and management decisions for WPA.

Analysis on the Legal System for Wetland Restoration in ASEAN+3 countries and Further Suggestions (아세안+3 습지 복원을 위한 법 제도 분석 및 제언)

  • Park, Hyekyung;Jeong, Hyeon Jin;Bae, Young Hye;Kim, Jae Geun;Kang, Sung-Ryong
    • Journal of Wetlands Research
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    • v.23 no.2
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    • pp.163-172
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    • 2021
  • This study aims to draw the limitations of wetland restoration related legal systems of ASEAN+3 countries and suggest the improvements. In the case of Korea, there is no integrated law or integrated management organization for wetland restoration, and the legal basis for estuaries restoration is insufficient. As many ASEAN countries depend on wetlands for their livelihood, public support for sustainable use and conservation of wetlands should be preceded through raising awareness about the value of wetlands. Some countries need to establish a specific wetland definition, while developing countries need to strengthen national capacities through international cooperation. A legal basis is needed to eliminate the impacts on peatlands and mangrove forests and conserve them.