• Journal of the Korean Society of Environmental Restoration Technology
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• 제21권6호
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• pp.55-69
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• 2018

As disaster risk and climate change volatility increase, there are more efforts to adapt to disasters such as forest fires, floods, and landslides. Most of the research, however, is about influence of human activities on disaster and there is few research on disaster adaptation for species. Previous studies focusing on biodiversity in selecting conservation areas have not addressed threats of disaster in the habitats for species. The natural disasters sometimes play role of drivers of ecological successions in the long run, but they might cause serious problems for the conservation of vulnerable species which are endangered. The purpose of this study is to determine whether soil loss (SL) is effective in selecting habitat management areas for amphibians and reptiles. RUSLE model was used to calculate soil loss (SL) and the distribution of each species (SD) was computed with MaxEnt model to find out the biodiversity index. In order to select the habitat management area, we estimated the different results depending if value of soil loss was applied or not by using MARXAN, a conservation priority selection tool. With using MARXAN, conservation goals can be achieved according to the scenario objectives, and the study has been made to meet the minimum habitat area. Finally, the results are expressed in two; 1) the result of soil loss and biodiversity with MATRIX method and 2) the result of regional difference calculated with MARXAN conservation prioritization considering soil loss. The first result indicates that the area with high soil loss and low species diversity have lower conservation values and thus can be managed as natural disturbances. In the area where soil loss is high and species diversity is also high, it becomes where a disaster mitigation action should be taken for the species. According to the conservation priorities of the second result, higher effectiveness of conservation was obtained with fewer area when it considered SL in addition to SD, compared to when considered only biodiversity. When the SL was not taken into consideration, forest area with high distribution of species were important, but when SL considered, the agricultural area or downstream of the river were represented to be a major part of habitats. If more species data or disaster parameters other than soil loss are added as variables later, it could contribute as a reference material for decision-making to achieve various purposes.

• Journal of the Korean Association of Geographic Information Studies
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• 제13권2호
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• pp.64-73
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• 2010

This research collected some multi-image information of Nakdong River Estuary Eulsukdo area in last 30 years, which are used as the basis information in running the qualitative analysis of the topography relief's deformation. First, to obtain the data, this research carried out a field survey and GCP measurement, then classified and collected the image information by analog and digital image. The acquired images which have passed a high-precise scan process and geometric correction is manufactured by Ortho Mosaic image, then divided them into 9 sections time period classification before we run a qualitative analysis. In late of 1980's there are many changes of environmental topography deformation of the Eulsukdo area which caused by large scale building constructions, appeared to be known through this research. And then in late of 1990's, we organized the wild cultivated lands, started the wetland restoration of the artificial ecology, in 2000's we are able to know the existence of topograph relief change which caused by big scale of bridge construction. Hereafter, in this quick process of the environmental and topographical change of this area caused by the 4 major rivers restoration project, the analysis results of this experiment are expected to be something applicable as important basic data.

• Journal of Environmental Impact Assessment
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• 제24권1호
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• pp.1-15
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• 2015

To mitigate the impacts of climate change on agricultural ecosystems, development of agricultural management for enhanced soil carbon sequestration is required. In this study, the effects of fertilizer types (chemical fertilizer and manure compost), cropping systems, and crop residue management on SOC(Soil Organic Carbon) sequestration were investigated. Summer corn and winter barley were cultivated on experimental plots under natural rainfall conditions for two years with chemical fertilizer and manure compost. Soil samples were collected conducted and analyzed for SOC for soil. To estimate long-term variation patterns of SOC, DNDC was run with the experimental data and the weather input parameters from 1981 to 2010. DNDC simulation demonstrated SOC reduction by chemical fertilizer treatment unless plant residues are returned; whereas compost treatments increased SOC under the same conditions and SOC increment was proportional to compost application rate. In addition, SOC further increased under corn-barley cropping system over single corn cropping due to more compost application. Regardless of nutrient input type, residue return increased SOC; however, the magnitude of SOC increase by residue return was lower than by compost application.

• Journal of Korea Water Resources Association
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• 제40권12호
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• pp.985-994
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• 2007

Small hydropower is the one of the cleanest one among new and renewable energy with less green house gas emissions. Recently, the necessity of developing small hydropower is emerging since its remaining potential resources in this country are abundant. However, a survey or research on the small hydropower development has been hardly performed since the 1990#s. These circumstances encourages a systematic approach for the small hydropower development. The purpose of this study is to propose a methodology of the location analysis for developing small hydropower. To this end, constraint and location criteria with weights are established and quantification method of each factor is presented. Especially, the analysis procedure is established on the basis of GSIS. Also the study focus on raising the objectivity and precision of analysis by developing system model with automatic search. The proposed methodology is applied to Bochung stream in Keum Riverbasin. The result selects the four and two locations of dam type and run-of-river type respectively. This study will be beneficial to the future activation of small hydropower development as a fundamental work.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제30권5호
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• pp.730-743
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• 1997

Community structure and distribution patterns of benthic polychaetes were studied in Aug. 1983 and Feb. 1984 in Kwangyang Bay, Korea. During the study period, the large-scale reclamation and dredging operations were taking place. Polychaetes were composed of 76 species with a mean density of $342\;ind.{\cdot}m^{-2}$ during the summer 1983 and 77 species with a mean density of $437\;ind.{\cdot}m^{-2}$ during the winter 1984. Community structure indices were applied to the seasonal data. The stations influenced by the Seomjin river are characterized by a low species number and low diversity, while the stations located in channel regions represent high species richness and highdiversity. The inner bay stations showed the intermediate level in terms of species richness and diversity. On the basis of taxa composition and abundance in summer, the cluster analysis indicated that the study area was divided into live regions. The main factors that govern the polychaete distributions appeared to be the fresh water run-off and bottom sediment composition. However, a slight difference was observed in winter community, and changes in composition of the dominant species were found from Lagis bocki and Chone teres to Glycinde gurjanovae and Heteromastus filiformis. As a result, the broad scale reclamation and dredging activities may have played a role in changes of the polychaete community structure and the dominant species composition in Kwangyang Bay.

• Journal of Navigation and Port Research
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• 제44권4호
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• pp.305-311
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• 2020

Rising sea levels along the coast from global warming causes the increase of wave energy along the coast. This rise in sea levels results in relatively deep water levels, which would incur the loss of sand that had not occurred in the past from erosion in coastal areas. Generally, it has been challenging to protect against coastal erosion, and the slope, cross-sectional shape, and materials are selected for the site conditions depending on the change in external forces. However, the application of counter measures based on insufficient understanding of the phenomenon is causing various damage, indicating the need for technological development and converging technologies to improve credibility. In this study, we developed eco-friendly permeable biopolymer concrete blocks to control the coastal erosion by using the Bio-Coast, an effective porous structure that mitigates the destructive erosion caused by the rising sea levels. The hexagonal design of Bio-Coast was derived from the honeycomb, columnar joints, and clover, which are durable and stable structures in nature, and the design was changed to apply bumps on the Bio-Coast filling in the form of a clover to reduce wave overtopping and run-up. Applying the field condition of beaches on the east coast of Korea, the block weight and size were decided and the prototype blocks were manufactured and are ready for field placement. In particular, it is intended to protect coastal areas from destructive erosion by natural and artificial external forces, and to extend the design to river,s lakes, and natural walking trails, to improve the efficiency of quality control and process control through the use of blocks.

• Transactions of the Korean hydrogen and new energy society
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• 제33권1호
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• pp.95-104
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• 2022

Micro hydropower is a readily available renewable energy source that can be harvested utilizing hydrokinetic turbines from shallow water canals, irrigation and industrial channel flows, and run-off river stream flows. These sources generally have low head (<1 m) and low velocity which makes it difficult to harvest energy using conventional turbines. A horizontal-axis screw turbine was designed and numerically tested to extract power from such low-head water sources. The 3-bladed screw-type turbine is placed horizontally perpendicular to the incoming flow, partially submerged in a narrow water channel at no-head condition. The turbine hydraulic performances were studied using Computational Fluid Dynamics models. Turbine design parameters such as the shroud diameter, the hub-to-shroud ratios, and the submerged depths were obtained through a steady-state parametric study. The resulting turbine configuration was then tested by solving the unsteady multiphase free-surface equations mimicking an actual open channel flow scenario. The turbine performance in the shallow channel were studied for various Tip Speed Ratios (TSR). The highest power coefficient was obtained at a TSR of 0.3. The turbine was then scaled-up to test its performance on a real site condition at a head of 0.3 m. The highest power coefficient obtained was 0.18. Several losses were observed in the 3-bladed turbine design and to minimize losses, the number of blades were increased to five. The power coefficient improved by 236% for a 5-bladed screw turbine. The fluid losses were minimized by increasing the blade surface area submerged in water. The turbine performance was increased by 74.4% after dipping the turbine to a bottom wall clearance of 30 cm from 60 cm. The final output of the novel horizontal-axis screw turbine showed a 2.83 kW power output at a power coefficient of 0.63. The turbine is expected to produce 18,744 kWh/year of electricity. The design feasibility test of the turbine showed promising results to harvest energy from small hydropower sources.

• Journal of Korea Water Resources Association
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• 제39권3호
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• pp.241-252
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• 2006

Numerical models for seepage analysis are useful tools to analyze problems and design protection techniques that are related to seepage through a levee. Though every model may have its own limitations and shortcomings, there were no generalized verifications or calibrations for the commercial models. It means that users can run the model and get the result without understanding nor taking any enough training. This paper Investigates applicability and suitability of some seepage numerical models by comparing analytical solutions with experiments in the user's viewpoint. The results showed that it is more desirable to use analyses with unsaturated-unsteady condition rather than those with saturated-steady conditions, since seepage phenomenon of real levees are changed according to water level and soil property. This study also compared the calculated unsteady solutions with the calculated steady solutions for the levee at Koa of the Nakdong River The comparison revealed that as the result, the safety factor of $2.0{\sim}3.5$ has the same effects for seepage protection techniques when they are designed on the basis of steady-state analysis.

• Journal of the Korean Geographical Society
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• 제43권6호
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• pp.808-823
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• 2008

Sediment abrasion in rivers is caused by the interaction between bedrock channel bed and sediment particles transported through the river. Abrasion rate of sediment particles in rivers is controlled by two major factors; Sediment transport conditions including hydraulic conditions form the erosive forces and physical and chemical strengths of the particles form a resistance force against abrasion and other erosional processes. Physical experiments were performed to find the role of each variable on sediment abrasion process. Total 266 sediment particles were used in this experiment. All sediment particles were divided into 11 independent sediment groups with sediment particle size and sediment loads. Each sediment groups were abraded in tumbling mill for up to 8 hours. Changes in weight were recorded by run and total: 2,128 cases of abrasion rate were recoded. Physical strength of rock particles was measured with point load strength index. It is found that sediment abrasion rate has a negative functional relationship point load strength index ($I_{a(50)}$) ($R^2=0.22$). It was suggested that physical strength of sediment particles set the "maximum possible abrasion rate'. As sediment flux increases, abrasion rates of sediment particles with similar point load strength index were changed. It could be concluded that not only physical characteristics of sediment particles, but also sediment transport conditions control sediment abrasion rates.

• Korean Journal of Environment and Ecology
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• 제26권6호
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• pp.884-891
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• 2012

The characteristic of fish fauna and distribution by habitat type in the Yanghwa stream were investigated from August, 2008 to June, 2009. During the surveyed period, 30 species belonging 8 families were collected. And there were 10 Korea endemic species(33.3%), including Rhodeus uyekii et and so on. Dominant species was Rhodeus notatus, and subdominant species was Pseudorasbora parva. Dominant species according to habitat type was Pseudorasbora parva in Dam type pool and Channel conected pool, Pseudogobio esocinus(Run), Zacco platypus(Riffle), Rhodeus notatus(Side channel and Substrate type pool), Squalidus gracilis majimae(Meander type pool), and Carassius auratus(Channel unconnected pool), respectively. As a results of community analysis in the Yanghwa Stream, diversity, richness, and abundance indices showed relatively high values, indicating that studied stream have relatively stable community structure. Moreover, cluster and principal component analysis were divided by two groups(lotic and lentic habitats), suggest that species and individuals were different among habitat types.