• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.353-353
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• 2021

메가가뭄으로 인한 적응전략 수립은 국민의 물 안보 및 수자원 재해에 대한 안전 증대에 매우 중요한 핵심기술임에도 불구하고 메가가뭄의 정량적인 평가지표는 개발 중인 상황이다. 본 연구에서는 국내/외 메가가뭄 분석 및 영향평가 관련 선행연구사례를 분석하여 메가가뭄 확산 단계별 평가지표를 도출하고자 하였다. 메가가뭄을 평가하기 위해 선행연구에서는 이상 강수량과 이상기온을 함께 고려하는 방법을 지속적으로 제안해 왔다. 이상 강수량은 기상학적 가뭄과 토양수분의 저하, 수문학적 가뭄, 사회경제적 영향에 이르기까지 가뭄을 평가할 수 있는 지표로써 활용할 수 있으며, 이상 기온은 폭염 등 기온 상승으로 인한 증발산량의 증가로 토양수분 저하와 저수량 감소 등의 영향을 평가할 수 있는 지표이다. 본 연구에서는 메가가뭄의 확산을 4단계로 구분하고 확산단계별 평가지표를 개발하였다. 또한 가뭄유형을 기상, 농업, 수문, 사회경제적 가뭄으로 구분하여 메가가뭄의 발생 단계와 그에 따른 가뭄의 확산 분야별 영향 분석을 수행하도록 제시하였다. 가뭄단계는 메가가뭄의 징후기, 진입기, 확산기, 지속적인 메가가뭄으로 인한 국가적 위기 4단계로 구분하였다. 메가가뭄은 1년 주기의 분석이 아닌 Carry over되는 연속적인 사상임에 따라 본 연구에서는 메가가뭄의 단계를 각각 2년, 3년, 4년 연속적으로 지속하였을 때로 구분하였으며, 이에 따른 기상, 농업, 수문, 사회경제적 평가지표를 제시하였다. 기상학적 메가가뭄 평가지표는 누적강수량을 이용한 강수량 부족으로 인한 가뭄, 이상기온(폭염)으로 인한 폭염으로 구분하였다. 농업적 메가가뭄 평가지표는 농업용수를 공급하는 농업용 저수지와 밭작물 생육에 영향을 미치는 토양수분에 관련한 평가항목을 이용하였으며, 수문학적 메가가뭄 평가지표는 다목적댐의 저수율과 하천 갈수량을 이용한 하천건천화 지수를 이용한 평가지표를 제시하였다. 사회경제적 메가가뭄 평가지표는 국민이 실제로 체감할 수 있는 지표로써 농작물 가격과 생·공용수의 제한급수 발생 현황을 이용한 평가가 가능하도록 제시하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3B
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• pp.311-317
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• 2009

Similarity indices between sampling sites are calculated and cluster analysis of fish community is carried out by UPGMA based on investigating fish fauna and water environment. The restoration indicators as target species of Wonju stream are selected Cottus poecilopus, Zacco temmincki, and Zacco platypus along upper, middle, and lower streams, respectively. For better habitat suitability, low flow increasing and induced water quality improving must be secured by sewer system rearrangement and watershed management. Composite habitat suitability of Zacco temmincki as target species at middle stream of Wonju stream improve significantly by low flow increasing, which is very important factor to improve habitat suitability. The changes of hydraulics of depth and velocity govern the habitat suitability in general, but the effects are not significant. Low flow increasing with the change of 10% reducing of lower channel improves the composite habitat suitability of 0.37~0.78 to their origin of 0.1~0.25, which represent the channel restoration scheme of Wonju stream for enhancing the habitat suitability of fish community.

• Journal of Korea Water Resources Association
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• v.53 no.12
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• pp.1193-1201
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• 2020

This study aims to develop a regression model that estimates a low-flow index that can be applied to ungauged basins. A total of 30 midsized basins in South Korea use long-term runoff data provided by the National Integrated Water Management System (NIWMS) to calculate average low-flow, average minimum streamflow, and low-flow index duration and frequency. This information is used in the correlation analysis with 18 basin factors and 3 climate change factors to identify the basin area, average basin altitude, average basin slope, water system density, runoff curve number, annual evapotranspiration, and annual precipitation in the low-flow index regression model. This study evaluates the model's accuracy by using the root-mean-square error (RMSE) and the mean absolute error (MAE) for 10 ungauged, verified basins and compares them with the previous model's low-flow calculations to determine the effectiveness of the newly developed model. Comparative analysis indicates that the new regression model produces average low-flow, attributed to the consideration of varied basin and hydrologic factors during the new model's development.

• Korean Journal of Ecology and Environment
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• v.46 no.1
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• pp.94-102
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• 2013

This study was carried out to determine the variation of the water level and crosssection area for investigating changes of stream foreland, and to determine the correlation between the average flow velocity and cross-section area so as to understand the hydrological characteristics of the stream. The slope of the cross-sectional area was changed in water levels of 0.6~1.0 m and 1.8~2.0 m. The first change occurred in the low-water level season, and the second change occurred in the high-water level seasons. It is assumed that the changes occurred due to the geological transfigure. The correlation between the cross-sectional area and the average flow velocity was 0.22~0.86 in the exponential equation and 0.20~0.87 in the linear equation. The low water level had a higher correlation than the high water level, and free weirs in the upper stream showed a very low correlation. Therefore, this study provides novel information for the management of water quality in the riverside, using correlation equations of the water level and flow velocity with the cross section area.

• Journal of Life Science
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• v.25 no.5
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• pp.533-538
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• 2015

Four sites and one site were used to analyze fish diversity at the water systems of the Sineun reservoir and the Jeonchon reservoir, respectively. The field experiments were conducted to test the density dependence that could lead to population regulation by artificial inferences and environmental changes. We examined the effects of environmental factors on fish densities using SMATR freeware. It was estimated to be reduced to the density effect at four sites in 2012. Shannon-Weaver indices of the diversity (H’) of the Sineun reservoir were similar to those of the Jeonchon reservoir. Species diversity was in a range of 0.645 to 2.105. The H’ value of the upper region was higher than those of middle and low regions were, and values of richness were lower in downstream than upstream. Using the maximum likelihood solution for the removal estimators of two low regions of the river stations, the estimated migration probabilities from the resident fish to the migrated fish for five species (Cyprinus cuvieri, Carassius auratus, Pseudorasbora parva, Misgurnus mizolepis, and Oryzias latipes) had a mean of 0.623. Especially, migration probabilities from the Jeonchon reservoir to the Sineun reservoir for five species were high (a mean of 0.681). The period of migration was suggested to be about one month because of short geographical distances (50 m). We found no significant difference between the three categories in the distribution of the other four species, indicating the species probability was similar among stations.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.667-677
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• 2020

This study was conducted to investigate the fish fauna and characteristics of the Carassius auratus population in the Boryeong Reservoir in Chungcheongnam-do from October 2017 to June 2018. The collected fish were identified as 3,506 individuals of 15 species from a total of nine families. The dominant and subdominant species were H. nipponensis with 1,706 (48.6%) individuals and C. auratus with 1,021 (29.1%) individuals, respectively. The biomass of C. auratus (246,130g), P. fulvidraco(50,610g), C. cuvieri (14,730 g), S. asotus (11,560 g), and C. carpio (10,930 g) was analyzed. The results of the community analysis showed a dominant index value of 0.87 (±0.2), a diversity index value of 0.78 (±0.5), an evenness index value of 0.47 (±0.2), and a richness index value of 0.99 (±0.5). The length-weight analysis of C. auratus showed a regression coefficient b of 3.06, and a condition factor (K) of 0.0004 with a positive slope. The frequency distribution of the total length analysis of the C. auratus population inhabiting the Boryeong Reservoir showed a high distribution of lengths between 140-160 mm and a low distribution between 230-280 mm. The normalized difference water index (NDWI) was analyzed over the Boryeong Reservoir water surface from 2013 to 2014 using Landsat 8 channel data. The areas where the NDWI was decreased were located at the inflow site of Ungcheon Stream.

• Journal of Wetlands Research
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• v.24 no.4
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• pp.354-366
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• 2022

To analyze the distribution of plant communities growing in river wetlands and the relationship between biotic and abiotic environmental factors, plant communities and environmental factors were investigated in river wetlands in the Boseong River. The Boseong River Wetland, the research site, consists of Hwapyeong Wetland, Bangujeong Wetland, and Seokgok Wetland. From June to September 2022, a plant community survey was conducted from the perspective of physiognomical vegetation, and the coverage of the emerging species followed the Braun-Blanquet scale. Plant species and the coverage of each species were recorded in the quadrant for plant community survey, and the cover of the quadrant, the total number of species, and the number of exotic species were measured as biological factors. As abiotic factors, altitude, orientation, inclination, soil texture, litter layer depth, dominant species diameter at breast height, and topography were recorded. In a total of 50 square plots, the most common Salix koreensis and Phragmites japonicus communities were found, and the community with the highest Shannon species diversity index was Phragmites japonicus-Echinochloa caudata community. As a result of ordination analysis by DCCA, the most significant clusters were separated according to topographic factors such as leeve, leeve slope, upper floodplain, lower floodplain, upper waterside, middle waterside, lower waterside, river island and opem water. As rare plants that need to be preserved in river wetlands, Hydrocharis dubia and Penthorum chinense were found in lower waterside, and it was found that the management of the river in the reservoir is necessary in line with the topographical distribution of ecosystem-disrupting plants, such as Paspalum distichum var. indutum.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.4 s.11
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• pp.131-143
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• 2003

The purpose of this study was to develop a new method for evaluation of stream naturalness in order to promote stream managers' understanding on importance of improving stream naturalness, and in order to appraise and prescribe for streams effectively in the process of ecological restoration of stream corridors. In order to analyze the evaluation method of stream naturalness and its applicability to streams, stream naturalness index(SNI) which has seven factors such as channel development, longitudinal profile, lateral section, stream bed structure, low flow channel structure, stream surroundings and water quality was suggested in this paper. For case studies, Bokha stream was selected for the evaluation of stream naturalness. At the Bokha stream, the scores of SNI factors were in range of $2.2{\sim}3.8$, and the average of SNI was 3.1, and the most frequent grade of SNI factors was grade 3. Among the 7 factors, the best was lateral section, and the worst was channel development. In this study, SNI grade can represent the characteristics of stream naturalness well and select the streams which will be restored, and can also decide the segment and the method of restoration for deteriorated streams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.427-437
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• 2016

The objective of this study is to develop the regional regression models based on the physiographical and climatological characteristics for estimating flow duration curve (FDC) in ungauged bsisns. To this end, the lower sections with duration from 185 to 355 days of FDCs were constructed from the 16 gauged streamflow data, which were fitted to the two-parameter logarithmic type regression equation. Then, the parameters of the equation were regionalized using the basin characteristics such as basin area, basin slope, drainage density, mean annual precipitation, mean annual streamflow, runoff curve number in order that the proposed regression model can be used for ungauged basin. From the comparison of the estimated by the regional regression model with the observed ones, the model with the combination of basin area, runoff curve number, mean annual precipitation showed the best performance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.805-812
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• 2014

This study investigates the impact of morphological change on the physical habitat simulation. For this, CCHE2D model is used for the hydraulic analysis including the morphological change, and the physical habitat suitability is assessed with habitat suitability curves. The model is applied to a 2.5km long reach downstream of the Goesan Dam, from Sujeon Bridge to Daesu Weir. Flow data of discharge and stage in July, 2006 are used in the computation. The numerical model is verified by means of comparison with the measured water surface elevation data, and the variation of the river bed is not verified in this study. Adult Zacco platypus is chosen for the dominant species. Physical habitat simulations result in composite habitat suitability and weighted usable area for drought, low, normal, and averaged-wet flows. The simulation results indicate that the composite suitability index increased at reaches right downstream of the Sujeon Bridge and around the bend. This also increased weighted usable area by 5.4-11.3%.