• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1011-1015
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• 2010

하천의 이용과 관리적 측면에서 가장 빈번하게 발생하는 하도의 직선화, 홍수량의 변화, 하상굴착, 하폭의 확대 축소 및 횡단구조물 등은 중규모 스케일의 하천지형을 인위적으로 교란시키는 대표적인 사례이다. 따라서, 이러한 인위적 교란은 하천생태계의 기반인 하천의 물리적 구조를 크게 변화시키므로 하도지형의 응답방향을 규명할 필요가 있다. 하천 유역의 지형은 여러 가지 스케일의 지형단위가 조직화되어 있는 것이므로 대(大) 중(中) 소(小)의 3가지 스케일 지형단위로서 계(系, system)를 계층화하고, 작은 계층의 계(系)에서는 큰 계층의 계(系)를 고정적인 경계조건으로 하여, 그 내부의 여러 가지 특징이나 변화를 규정하는 주요 인자를 이용하여 분석해야 한다. 또한 대(大) 스케일은 유역스케일의 지형스케일이며, 하도의 수계망이나 하도종단형 형상 등이다. 중(中) 스케일은 segment에서 reach 스케일의 지형이며 사행형상, 하천 폭 등이다. 소(小)스케일은 수심의 10배 정도이하의 지형스케일이며, 소규모 하상파 등의 미지형(微地形)이다. 따라서, 본 연구에서는 남강과 황강을 대상하천으로 유량 조절과 유사공급이 차단되는 댐하류 및 골재채취와 같은 인위적 교란요인에 의한 중규모(segment scale) 하도지형의 변화와 응답방향을 조사, 분석하였다. 연구결과 유량 및 유사공급량의 변동의 크기에 따라 전체적인 하상저하와 더불어 사주와 소가 소멸되면서 여울과 소가 사라지는 현상이 동조하는 것으로 분석되었으며, 하상의 평탄화에 의하여 저수로의 폭이 넓어져 복열사주가 발달하면서 수심 및 유속의 다양성이 감소되는 것으로 분석되었다.

• Journal of the Korean Institute of Landscape Architecture
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• v.24 no.4
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• pp.123-131
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• 1997

Since the industrial revolution. the growth of cities has been especially apid and the rate of ulbanization has been high. This urban development is encroaching on the natural environment because the cities are developed with not only residential estates, industrial area and buildings but also with infrastructure. The surface area of the city is sealed ,with pavement whereas nature is disturbed and modified. The hydrological cycle in the city is inf1uenced by the change of land use I. e., from forest to agricultural land, talc draining of wetlands and above all the increase of built-up areas. The surface retention and interception of precipitation in the city is reduced. because the surface area is now smooth and solid. The characteristics of the hydrological cycle in the city are increased runoff, reduced evapotranspiration and infiltraction . We have too much faith in technology although it may cause more unforseen problems. We build more river banks and 'emulation dams and straighten rivers and streams in order to protect ourselves from disasters.. However. the results of hose developments are often higher$.$ water levels, the disturbance of aquatic ecosystems and the reduction of biodiversity. Therefore, we should examine problems from the hydrological cycle in cities and study a natural system as close cities to nature as possible. This paper shows the problems caused by the hydrological cycle in the city. The ecology-oriented method and design must be used in order to protect our environment from dicturbance.

• 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.53-61
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• 2021

Distribution of fish community depends largely on environmental disturbance such as habitat change. In this study, we evaluated the impact of environmental variables and microhabitat patch types on fish distribution in Yudeung Stream at 15 sites between early May and late June 2019. We used non-metric multidimensional scaling to examine the distribution patterns of fish in each site. Gnathopogon strigatus, Squalidus gracilis majimae, Zacco koreanus, and Zacco platypus were associated with riffle and boulder areas, whereas Iksookimia koreensis, Acheilognathus koreensis, Coreoleuciscus splendidus, Sarcocheilichthys nigripinnis morii, and Odontobutis interrupta were associated with large shallow areas. In contrast, Cyprinus carpio, Carassius auratus, Lepomis macrochirus, and Micropterus salmoides were found at downstream sites associated with large pool areas, sandy/clay-bottomed areas, and vegetated areas. On the basis of these results, we suggest that microhabitat patch types are important in determining the diversity and abundance of fish communities, since a mosaic of different microhabitats supports diverse fish species. As such, microhabitat patches are key components of freshwater stream ecosystem heterogeneity, and a suitable patch composition in stream construction or restoration schemes will support ecologically healthy food webs.

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.11-21
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• 2013

In-situ test to find the change of $Fe^{2+}$ and $Mn^{2+}$ concentrations and ion contents in groundwater was conducted during two pumping tests at the riverbank filtration site, where is the riverine area of the Nakdong River in Changnyeong-Gun. Groundwater was sampled at one pumping well and 10 monitoring wells during a 5 steps drawdown pumping test with the rates from $500m^3/day$ to $900m^3/day$ and a constant pumping test with $800m^3/day$. The change in ion concentration of groundwater was more remarkable during a step drawdown pumping test than a constant pumping test. Especially, the decrease in $Fe^{2+}$ and $Mn^{2+}$ concentrations was distinct in a step drawdown pumping test and it happens predominantly along the direction that the radius of pumping influence was small due to a good aquifer connectivity to a pumping position. The precipitation and the oxidation of iron and manganese were caused by an air inflow and a disturbance in groundwater flow due to an abrupt change in pumping rate. The pumping rate and spatial distribution of an aquifer around a pumping well need to be considered as an important factor for the development of in-situ iron and manganese treatment technology.

• Journal of the Korean Association of Geographic Information Studies
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• v.7 no.3
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• pp.22-34
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• 2004

An artificial disturbance like fragmentation in watershed forest has impacted a sustainability of watershed ecosystem, therefore this research quantified the landscape structure in the Geumho river watershed using landscape indices and GIS. Landscape indices were calculated from the forest distributed maps for 24 subwatersheds. Three common factors, which explained about 85% of the variation in the original data, were extracted by a factor analysis. The fragmentation gradient in forest landscape, which was calculated from the factor scores, was correlated with proportion of urban land (r=0.827, p<0.01, $R^2$=0.685), elevation (r=-0.637, p<0.01) and slope gradient (r=-0.593, p<0.01). The result of the study presented that the methodology and the values of landscape indices to assess the structural patterns of forest landscape for the Geumho river watershed management. Future research will be directed towards the detection of impacts of landscape patterns and their changes on the integrity of watershed environments.

• Journal of Wetlands Research
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• v.19 no.3
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• pp.327-334
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• 2017

The flood pulse in streams enhances the biodiversity and ecosystem services of the channel-floodplain ecosystems by exchanging water, nutrients, sediments and organisms. However, the lateral connectivity in most streams of Korea has been disrupted by the levee constructions for the purpose of flood control and land use of floodplains. To compare the characteristics of floodplain vegetation according to existence of lateral connectivity in streams, we investigated the geomorphological and soil environmental factors and structures and distribution of vegetation in the floodplains connected and isolated by levee to the channel in Cheongmi Stream, Seom River, Hwangguji Stream, Mangyeong River, Gomakwon Stream, and Boseong River, Korea. In comparison of soil environments, moisture and clay contents were higher in the isolated floodplain than in the connected floodplain. According to the result of principal component analysis (PCA) using environmental data, the environments of the connected floodplain and the isolated floodplain were separated by soil moisture contents, soil texture and distribution altitude of the vegetation. The results of detrended correspondence analysis (DCA) using vegetation data showed that the isolated floodplain was dominated by the hydropythic communities of diverse life form and that the connected floodplain was dominated by the hygrophytic communities that endure disturbance. In conclusion, it is thought that the vegetation of the floodplain changed to the lentic wetland vegetation dominated by diverse hydrophytes as the floodplain was isolated from the channel by artificial levees.

• Journal of Korean Society on Water Environment
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• v.33 no.5
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• pp.511-524
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• 2017

This study was carried out for the purpose of creating a restoration plan to improve the ecological quality of the Changwon and Nam streams. Based upon the results of comprehensive diagnostic assessment, restoration priority was given to the upstream reach, where conservation status is relatively superior. Restoration level was usually determined to practice active restoration as conservation, and the states of both Changwon and Nam streams were not so good. Restoration plans, by reach, were classified into "upstream", "midstream", and "downstream" were suggested in both terms of horizontal section frame and vegetation-based on the result of diagnostic assessment and the reference information. "Upstream", "mid-stream" and the "downstream" of Changwon and Nam streams were classified into "small-gravel- mountainous", "small-sand-plain", and "small-clay-plain streams" respectively (based on scale, and substrate and slope of river bed). The spatial arrangement of vegetation was laid out in diagram form by reflecting micro-topography and the water level of the horizontal section of river. Information regarding species composition was recommended as dominant species, which appear frequently in three vegetation zones composed of herbaceous plants, shrubs and trees and sub-tree- dominated zones divided by reflecting disturbance regime, depending on position on the horizontal section of river. Moreover, there have been prepared not only plans to improve the terrestrial ecosystems around the streams but also plans to create ecological networks, which can serve to improve the ecologic quality of the whole regional environment by serving to connect streams and terrestrial ecosystems, a process probably necessary and definitely recommended to realize true (genuine) restoration. Plans for ecological parks and networks were prepared by mimicking the species composition of Alnus japanica community, Zelkova serrata community, Carpinus laxiflora community, Quercus aliena community, and Q. serrata community.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.184-192
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• 2007

This study was to evaluate ecological health of Sumjin River during April${\sim}$June 2006. The ecological health assessments was based on the Index of Biological Integrity (IBI), Qualitative Babitat Evaluation Index (QHEI), and water chemistry. For the study, the models of IBI and QHEI were modified as 10 and 11 metric attributes, respectively. We also analyzed spatial patterns of chemical water quality over the period of $2002{\sim}2005$, using the water chemistry dataset, obtained from the Ministry of Environment, Korea. In Sumjin River, values of IBI averaged 33 (n= 12), which is judged as a "Fair${\sim}$Good" condition after the criteria of Barbour at al. (1999). There was a distinct spatial variation. Mean IBI score at Site 5 was estimated as 40, indicating a "Good" condition whereas, the mean at Site 3 was 23, indicating a "Poor${\sim}$Fair" condition. Habitat analysis showed that QHEI values in the river averaged 109 (n=6), indicating a "Marginal" condition after the criteria of Harbour et al. (1999). Values of BOD and COD averaged 1.3 mg $L^{-1}$ (scope: $0.9{\sim}1.8$ mg $L^{-1}$) and 3.3 mg $L^{-1}$ (scope: $2.8{\sim}4.0$ mg $L^{-1}$), respectively during the study. It was evident that chemical pollutions by organic matter were minor in the river. Total nitrogen (TN) and total phosphorus (TP) averaged 2.5 mg $L^{-1}$ and 0.067 mg $L^{-1}$, respectively, and the nutrients did not show large longitudinal gradients between the upper and lower reach. Overall, dataset of IBI, QHEI, and water chemistry suggest that river health has been well maintained, compared to other major watersheds in Korea and should be protected from habitat disturbance and chemical pollutions.

• Korean Journal of Ecology and Environment
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• v.42 no.2
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• pp.183-191
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• 2009

This study was to evaluate ecological health of Dongjin River in October 2007. The ecological health assessments was based on the Index of Biological Integrity (IBI), Qualitative Habitat Evaluation Index (QHEI), and water chemistry. For the study, the models of IBI and QHEI were modified as 8 and 11 metric attributes, respectively. We also analyzed spatial patterns of chemical water quality over the period of 2005${\sim}$2008, using the water chemistry dataset, obtained from the Ministry of Environment, Korea. In Dongjin River, values of IBI averaged 19 (n=3), which is judged as a "Fair" condition after the criteria of Barbour et al. (1999). There was a distinct spatial variation. IBI score at Site 1 was estimated as 28, indicating a "Good" condition whereas, IBI at Site 2 and Site 3 were as 18 and 12, indicating "Fair" and "Poor" condition, respectively. Habitat analysis showed that QHEI values in the river averaged 117 (n=3), indicating a "Fair${\sim}$Good" condition after the criteria of Barbour et al. (1999). Values of BOD and COD averaged 2.3 mg $L^{-1}$ (scope: 0.1${\sim}$8.9 mg $L^{-1}$) and 5.5 mg $L^{-1}$ (scope: 1.8${\sim}$12.6 mg $L^{-1}$), respectively during the study. Total nitrogen (TN) and total phosphorus (TP) averaged 2.7mg $L^{-1}$ and 0.127mg $L^{-1}$, respectively, and the nutrients showed large longitudinal gradients between the upper and lower reach. Overall, dataset of IBI, QHEI, and water chemistry showed that river health was a gradual decline at upstream to downstream. So, Dongjin River should be protected from habitat disturbance and chemical pollutions.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.194-205
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• 2022

Sandbars formed by sediment transportation and sedimentation are some of the most important habitats for specific wildlife and they provide an aesthetic landscape in streams. The purpose of this study was to understand the successional process of the colonization and development of early vegetation over time on sandbars exposed by the opening of a gate at a downstream weir. We selected the following four study sites in the Geumgang River, South Korea: three weir-upstream sites with different gate-opening times and a control site that was not affected by weir operation. Changes in the structural characteristics and spatial distribution of the riparian vegetation on the sandbars exposed after opening the gate at the weir were surveyed according to the different exposure periods of the sandbars at the study sites. The newly formed sandbars accounted for more than 33% of the area of the existing floodplain in the three weir-upstream sites of the Geumgang River after opening the gate at the weir. Nine main plant communities were distributed on the exposed sandbars. These communities were classified as annual mesophytic, perennial hydrophytic, perennial hygrophytic, subtree, and tree vegetation based on their species traits. As the duration of exposure of the sandbar increased, the area of the bare sandbar and the annual herbaceous and perennial hydrophytic communities decreased, and the areas occupied by perennial hygrophytic, subtree, and tree communities increased. Changes in vegetation on the sandbar were classified into three types of succession according to the condition of the aquatic habitat before the gate-opening and the degree of physical disturbance caused by the water flow after the gate-opening. The types of succession were: 1) succession starting from hydrophytes in the lentic aquatic zone, 2) succession starting from annual herbaceous hygrophytes in the lotic aquatic zone, and 3) willow-dominated succession in the disturbed channel side. Our results suggested that the dynamics of successional changes in vegetation should be considered during weir operation to ecologically manage the habitats and landscape of the fluvial landforms, including sandbars in streams.