• 생태와환경
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• 제41권4호
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• pp.431-440
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• 2008

Turbid water or suspended sediment is associated with negative effects on aquatic organisms; fish, aquatic invertebrate, and periphyton. Effects of turbid water on fish differ depending on their developmental stage and a level of turbidity. Low turbid water may cause feeding and predation rates, reaction distance, and avoidance in fish, and it could make fish to die under high turbidity and long period. Therefore, it is very important to find out how turbid water or suspended sediment can affect fish in domestic watersheds. The objectives of this study were 1) to introduce international case studies and their standards to deal with suspended sediment, 2) to determine acute toxicity in 4 major freshwater fishes, and 3) to determine in relation to adverse effect of macroinvertebrates and fish. Impacts of turbid water on fish can be categorized into direct and indirect effects, and some factors such as duration and frequency of exposure, toxicity, temperature, life stage of fish, size of particle, time of occurrence, availability of and access to refugia, etc, play important role to decide magnitude of effect. A review of turbidity standard in USA, Canada, and Europe indicated that each standard varied with natural condition, and Alaska allowed liberal increase of turbidity over natural conditions in streams. Even though acute toxicity with four different species did not show any fatal effect, it should be considered to conduct a chronic test (long-term) for more detailed assessment. Compared to the control, dominance index of macroinvertebrates was greater in the turbid site, whereas biotic index, species diversity index, species richness index, and ecological score were smaller in the turbid site. According to histopathological analysis with gills of macroinvertebrate and fishes, morphological and physiological modification of gills due to suspended sediments can cause disturbance of respiration, excretion and secretion. In conclusion, in order to maintain good and healthy aquatic ecosystem, it is the best to minimize or prevent impact by occurrence of turbid water in stream and reservoir. We must make every effort to maintain and manage healthy aquatic ecosystem with additional investigation using various assessment tools and periodic biomonitoring of fish.

• 한국수자원학회논문집
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• 제51권8호
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• pp.713-727
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• 2018

본 연구는 국내 하천의 고유성을 반영할 수 있는 물리적 환경평가 체계를 개발하는 것이다. 하천유형 분류, 평가구간 선정, 평가 항목 및 지표에 대하여 종합적으로 요약하였다. 하천의 물리적 구조는 하천 유수력에 의한 반응의 결과이므로 하도경사, 하상재료의 입경 및 하도지형의 특성에 따라 하천을 3가지 유형으로 분류하였다. 평가구간은 각 하천 유형의 대표적인 특징인 step 또는 여울출현 간격, 사행도에 따라 저수로 폭의 10배와 25배 기준으로 선정하였다. 평가지표는 하도 안정성, 흐름 상태, 횡단면 형상, 하안 안정성, 하도개수 및 하천횡단구조물과 같은 공통지표와 유효 서식지, 하상 매몰도, 흐름의 다양성 및 step과 여울 출현빈도와 같은 하천 유형별 특성지표로 구성되어 있다. 적용성 검토를 위하여 개발된 평가체계를 9개의 하천에 적용하고 그 결과를 제시하였다.

• 한국환경생태학회지
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• 제34권3호
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• pp.249-258
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• 2020

이 연구는 강원도 산림유역 내 수계(총 11개 계류)를 대상으로 유목의 전수조사를 실시하고, 유목의 발생기원 추적과 함께 하천차수별 현존량과 분포형태를 분석하여 효과적인 산림유역관리기술의 마련을 위한 기초자료를 제공하고자 실시하였다. 총 1,207개 유목의 개체목 형태를 3가지 유형으로 구분하여 분석한 결과, (1) 수간만 있는 것 1,142개(95%) 및 수간과 근주가 함께 있는 것 65개(5%), (2) 자연목 1,015개(84%) 및 벌채목 192개(16%), (3) 침엽수 1,050개(87%) 및 활엽수 157개(13%)로 나타났다. 유목의 현존량(㎥/ha)은 1차수 105.4, 2차수 71.3 및 3차수 35.6으로 하류로 갈수록 점차 감소하였다. 반면 유목의 총량에 대한 유목군의 비율은 1차수 11%, 2차수 43% 및 3차수 49%로 하류로 갈수록 증가하였다. 이 연구에서 조사된 유목의 현존량을 해외의 선행연구와 비교하면, 비록 각 국가·지역별로 기후·지형·산림토양·임분의 구조와 생장량·산림의 교란정도와 관리상태가 다르지만, 유목의 현존량은 임령과 정의 상관관계를 갖는 것으로 나타났다. 이 연구의 결과는 유목을 산림생태계의 산물이자 산지수변림 교란의 지표로서 인식할 필요가 있음을 시사한다. 이를 토대로 앞으로는 산림유역의 생태계뿐만 아니라 하류의 수계환경까지 고려하여 숲가꾸기 산물의 처리나 수변지역의 임분밀도관리 등을 포함한 산림관리기술이 정립되어야 할 것으로 판단된다.

• Journal of Ecology and Environment
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• 제32권3호
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• pp.197-206
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• 2009

Benthic macroinvertebrate communities were collected from six different sites in the Dobong Stream in Seoul, Korea to investigate spatial and temporal changes in benthic macroinvertebrate communities in response to natural disturbances such as floods and droughts. We collected samples monthly or semimonthly with a Surber net ($30cm{\times}30cm$), and measured environmental factors, including stream temperature, discharge, width, conductivity, dissolved oxygen and pH at each sampling site. Benthic macro invertebrates were strongly affected by floods as well as droughts. In addition, benthic macroinvertebrate communities displayed different responses to the onset of the rainy season in summer 2006 and 2007, apparently due to differences in the intensity and amount of precipitation. Chironomids were particularly sensitive to heavy rain. Floods and droughts also affected the proportions of functional feeding groups during the survey period: the proportion of scrapers was high right after heavy rains, while the proportion of predators tended to increase in intermittent-type streams as the riffle zone decreased. Finally, although species richness and abundance were strongly influenced by heavy rain, they recovered to background levels for within one month, and varied consistently among stream types, indicating habitat stability.

• 환경영향평가
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• 제20권1호
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• pp.1-11
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• 2011

This study was carried out to suggest the baseline data necessary for vegetation restoration at riverine wetland within stream corridor. We used the prevalence index for wetland assessment by applying the method of weighted averages with index values based on five hydrophyte indicator status as defined by estimated probability occurred in wetland. We selected near nature and urbanized reach of Gap and Yanghwa streams as experimental site. Although two sites have some different disturbance and characteristics of watershed, they showed that similarity of vegetation community including three dominant species - Salix koreensis, Phragmites communis, Miscanthus sacchariflorus - was very high. But in case of Yanghwa stream, various kinds of emergent plants along wetted condition were distinctly occurred, resulted from difference of hydrological regime and substrate, etc. Degree of naturalness of vegetation at the sampled areas indicated that near nature area of Gap stream and all area of Yanghwa stream were fitted as riverine wetland, while urbanized area of Gap stream has changed into upland condition. In conclusion assessment system using prevalence index would be considered an effective method for evaluating of natural states of riverine wetland, but further integrated consideration of physical, hydrological, and biological factors of stream process, and also with considering the difference between those qualitative data of vegetation community.

• 대한기계학회논문집B
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• 제33권7호
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• pp.527-534
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• 2009

Flame stabilization characteristics were experimentally investigated in a fuel-air cross flowing mixing layer. A combustor consists of a narrow channel of air steam and a cross flowing fuel. Depending on the flow rates of methane and air, flame can be stabilized in two modes. First is an attached flame which is formulated at the backward step where the methane and air streams meet. Second is a lifted-flame which is formulated within the mixing layer far down steam from backward step. The heights and flame widths of the lifted flames were measured. Flame shapes of the lifted flames were similar to an ordinary edge flame or a tribrachial flame, and their behavior could be explained with the theories of an edge flame. With the increase of the mixing time between fuel and air, the fuel concentration gradient decreases and the flame propagation velocity increases. Thus the flame is stabilized where the flow velocity is matched to the flame propagation velocity in spite of a significant disturbance in the fuel mixing and heat loss within the channel. This study provides many experimental results for a higher fuel concentration gradient, and it can also be helpful for the development and application of a smaller combustor.

• Journal of Forest and Environmental Science
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• 제32권4호
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• pp.377-383
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• 2016

We obtained a total of 36 GPS coordinates of the seven bat species of Rhinolophus ferrumequinum, Myotis ikonnikovi, M. nattereri, M. petax, Murina ussuriensis, Plecotus auritus, and Pipistrellus abramus. Characteristics of forests (forest type, age class, DBH class and crown density), terrain (aspect, slope and distance from mountain stream) and disturbance factors (distance from human residential areas and distance from cultivated areas) that bats have used as their habitats were revealed from the GIS analysis based on GPS coordinates of the 36 positions that bats were found. The bats-preferred forest type is broad-leaf forests (43%) with the trees of the 2th (31%) and 5th (31%) age class, the trees of sapling (36%) and large DBH class (31%), and sparse crown density (67%). Bats prefer the slop direction of the east (39%), the gradient below $15^{\circ}$ (61%), the ranges within 200 m from the mountain streams (92%), the ranges within 200 m near roads (89%), the ranges of 200-400 m from human residential areas (28%), and the ranges within 200 m from cultivated areas (36%).

• 설비공학논문집
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• 제16권11호
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• pp.1084-1091
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• 2004

In automotive air handling system, mixing of air streams by the cooler and the heater affects the comfort of cabin room. In the present study, computer-aided analysis is done to improve the thermal comfort and for the optimal design of automotive HVAC system. The simulation software used was FLUENT, and complicate geometries were created by three dimensional CAD. Air flow volume, fir distribution rate and temperature controllability and temperature differences between upper and lower discharge air are analyzed through numerical simulation at vent, floor and defrost mode. Also, velocity vector of sirocco fan is investigated through the scroll housing. The velocity vector magnitude is larger at lower region of fan than that at any other regions. Recirculation and disturbance of air is relatively high near the cut-off edge in the scroll housing. By using the results of this study, the time for prototype production can be reduced and timely decisions can be made to determine initial design directions.

• Spatial Information Research
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• 제10권4호
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• pp.501-513
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• 2002

Eurasian otter (Lutra lutra) is one of endangered wildlife species whose population size is declining in Korea. To manage and conserve habitat for Eurasian otter, it is crucial to understand which habitat components affect otter habitat qualities. The objectives of this study were to develop a habitat suitability model of Eurasian otter in Soraksan National Park, to validate the model in Odaesan National Park. The research methods of this study were as follows. First, trace data and characters of Eurasian otter habitat were collected with Geographic Information System (GIS) data and Global Positioning System (GPS) receivers between 2000 and 2002. Second, the habitat use factors were identified as habitat characteristics of Eurasian otter and classified with habitat use and availability analyses. Third, significant factors of habitat model were extracted by Chi-square test. The last, Eurasian Otter Habitat Suitability Model (EOHSM) was employed by logistic regression method. Otter habitat use was positively associated with the reeds and shrubs areas adjacent to streams, the size of boulders, and low human disturbance in Soraksan National Park by EOHSM. This model had a classification accuracy of 74.4% at cutoff value of 0.5. Model validation showed a classification accuracy of 86.6 % at cut off value of 0.5 for otter habitat in Odaesan National Park.

• 한국조경학회지
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• 제24권4호
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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.