• Journal of Environmental Science International
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• v.31 no.5
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• pp.431-445
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• 2022

The Gwangju Stream is a major tributary of the Yeongsan River. To maintain environmental and ecological functions in the stream, the flow is secured by natural water from the Mudeung Mountain as well as waters discharged from Lake Juam and the Gwangju sewage treatment plants. A substantial amount of water is supplied into the upper reaches of Gwangju Stream from Lake Juam. To examine the ecological effects of the water input from Lake Juam on the Gwangju Stream, a field survey of phytoplankton community species and an evaluation of water properties was conducted at five stations, from station GJ1 before the inflow to station GJ5 in the lower region. Nutrient levels decreased in the vicinity of the Lake Juam inflow, suggesting that this water inflow can contribute to the reduction of eutrophication in the stream. The phytoplankton community was mainly composed of Bacillariophyceae, Chlorophyceae, and Cyanophyceae, and the community structure was similar to that of the other study sites located near the water inflow regions. The inflow of water from Lake Juam can affect water quality and the phytoplankton community over a limited area, reducing eutrophication and increasing water flow in the Gwangju Stream.

• Journal of Ecology and Environment
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• v.41 no.8
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• pp.213-222
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• 2017

Background: This study was conducted to assess the physicochemical water quality and the altitudinal distribution of low-temperature and mountain epilithic diatom (LTMD) community in Buk and Hangae streams that are located in Seorak Mountain with the height of 1708 m in Korea. And the community characteristics of LTMD found in the Buk and Hangae streams were compared to that of LTMD from the Han River system. Results: The physicochemical water qualities of Buk and Hangae streams were determined to be very clean. As a result of analyzing the community composition, 135 taxa of epilithic diatoms were determined, and 22 taxa appeared including Hannaea arcus var. subarcus which are known to have low-temperature and mountain ecological characteristics in the literatures. The relative frequencies of LTMD were 37.0~0.9% range from the upper to lower regions. Although Diatoma tenuis, Eunotia minor, and Gomphonema affine are known to be ubiquitous in streams and lakes, in this research, the three taxa were added into low-temperature and mountain epilithic diatom, since D. tenuis and E. minor appeared only in altitudes above 600 m, and G. affine had the highest relative frequency during spring and fall in altitudes above 700 m, when water temperature was around $10^{\circ}C$. Conclusions: Among the 24 taxa of low-temperature and mountain epilithic diatom (LTMD) (including the 3 taxa added in this study), 14 taxa (Diatoma hyemalis, D. mesodon, D. tenuis, Hannaea arcus, H. arcus var. subarcus, Ulnaria inaequalis, Eunotia bilunaris, E. implicata, E. minor, E. muscicola, E. silvahercynia, E. septena, Delicata delicatula, and Gomphonema affine) represented the characteristics of LTMD very well; they grow best in water temperatures below $15^{\circ}C$ in Buk and Hangae streams and Han River system.

• Journal of Korean Society of Forest Science
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• v.101 no.3
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• pp.333-343
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• 2012

In-stream large wood (LW) has a critical impact on the geomorphic characteristics relevant to ecosystem management and disaster prevention, yet relatively little is known about variations in its dynamics and subsequent export on the watershed-scale perspective in Korea. Here we review variations in the dynamics and subsequent export of LW as a function of stream size, which is appropriate for Korean mountain streams. In upstream channels with narrow bankfull widths and low stream discharges, a massive amount of LW, resulting from forest dynamics and hillslope processes, may persist for several decades on valley floor. These pieces, however, are eventually transported during infrequent debris flows from small tributaries, as well as peak hydrology in main-stem channels. During the transport, these pieces suffer fragmentation caused by frictions with boulders, and stream bank and bed. Although infrequent, these events can be dominant processes in the export of significant amounts of LW from upstream channel networks. In downstream channels with wide bankfull widths and high stream discharges, LW is dominantly recruited by forest dynamics and bank erosion only at locations where the channel is adjacent to mature riparian forests. With the LW pieces that are supplied from the upstream, these pieces are continuously transported downstream during rainfall events. This leads to further fragmentation of the LW pieces, which increases their transportability. With decreasing stream-bed slope, these floated LW pieces, however, can be stored and form logjams at various depositional sites, which were developed by interaction between channel forms and floodplains. These pieces may decay for decades and be subsequently transported as particulate or dissolved organic materials, resulting in the limitation of LW fluvial export from the systems. However, in Korea, such depositional sites were developed in the extremely limited streams with a large dimension and no flood history for decades, and thus it does not be expected that the reduction of LW export amount, which can be caused by the long-term storage. Our review presents a generalized view of LW processing and is relevant to ecosystem management and disaster prevention for Korean mountain streams.

• Journal of agriculture & life science
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• v.50 no.5
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• pp.111-120
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• 2016

The objective of this study was to provide basic information for selecting the right timing and the right place of erosion control of stream on Gyeongsangnam-do. In order to achieve this objective, a total of 526 erosion control dams and 230 mountains stream conservation facilities on the constructed places and construction planned places for the erosion control were investigated on site, forest physiognomy, and hydrologic conditions. The erosion control dams and mountain stream conservation facilities were mostly constructed in the area, which has the sedimentary rock, 200-400m of altitude, a slope of 21~30°, and II of landslide hazard map. Among the forest environmental factors, it was only similar to the construction frequency in the areas that have small diameter class, III age class. Also, we investigated the hydrological environmental factors that determine the size and numbers of erosion control dam. The places constructed to the highest frequency were below 50ha in the area, 2.1~4.0km/㎢ of drainage density, longitudinal water system, 61~90mm of maximum precipitation per hour, and 201~300mm of day maximum precipitation. As the results, the sites and floodgate conditions between the constructed places and stream conservation facilities for the erosion control showed to be very similar. Therefore, these results indicate that the erosion control of the stream of the areas, which have the disruption of mountain peaks and the high erosion risk areas, should be used on both the erosion control dam and stream conservation facilities.

• Journal of Korea Water Resources Association
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• v.45 no.9
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• pp.853-860
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• 2012

It is well-known that loop effect of the stage-discharge relationship is formulated based on many field observations especially for the sand rivers. Theoretical understandings of the loop effect for the sand rivers have been widely provided, based on the facts that it is driven by the flood wave propagation and bed form changes over the given flood period. However, very few theoretical studies or field observations associated with loop-rating curves in the gravel or rock-bed mountain streams have been attempted so far, due particularly to the difficulties in the accurate discharge measurement during the flood in such field conditions. The present paper aims to report a unique loop-rating curve measured at a gravel and rock-bed mountain stream based on the flood discharge observation acquired during the typhoon, Muifa that passed nearby Jeju Island in summer of 2011. As velocity instrumentation, a non-intrusive Surface Velocity Doppler Radar to be suitable for the flood discharge measurement was utilized, and discharges were consecutively measured for every hour. Interestingly, the authors found that the hysteresis of the loop-rating curve was adverse compared to the typical trend of the sand bed streams, which means that the discharge of the rising limb is smaller than the falling limb at the same stage. We carefully speculate that the adverse trend of the loop-rating curve in the gravel bed was caused by the bed resistance change that works differently from the sand bed case.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.4
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• pp.52-64
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• 2010

This study was carried out to analyze the occurrence characteristics and the influence of forest environment factors on the debris flow of 3 national parks in korea. The results obtained from this study were summarized as follows; The total number of debris flow occurrence was 125 areas. The average length of the debris flow scar was 144m, average width was 20m. And the average area and sediment were $2,854m^2$ and $3,959m^3$ respectively. The factors influencing the debris flow were highly occurred in Metamorphic rock, mixed forest type. And also, slope gradient was $30{\sim}35^{\circ}$, aspect was NE, altitude was over 1,000m, vertical and cross slope was concave (凹), soil depth was below 15cm, stream order was 0 order. The variables of cross slope (complex), deciduous tree, soil depth (over 46cm), cross slope (concave), mixed forest type and altitude (801~1200m) in correlation analysis were significant at 1 % level. The landslide of high mountain area highly tend to change the debris flow in stream bed of torrent. The debris flow in national parks mainly occurred in high mountain area with long ridge and steep slope.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.4
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• pp.75-81
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• 2001

This project provides designs for renewal of the surrounding environment related to old fountains typically located in cities. In many cities, the fountain element has bee located with a strategic position in the city. Located in the central area of Cheongju, the Sajik Fountain Fountain has significant position in the local city. However, due to changes in the surrounding area and the old-fashioned form of the fountain, it has not contributed substantially to the cityscape. Including the historical Seomoon Bridge and Moosim-Cheon(stream) as Wooam-San(mountain) setting, the surrounding environment of our planning site appear to be a locally important place. In respect to building with a broad function, landscape designers focused on the reconsideration of symbolization as landmark, of the image of Cheongju city, of recognition by removing the horizontal line and of the substantial civil´s use rate. Achieved by working with a sculptor, a new function, the main facility, is managed sculpturally and imaged in a drop of water representing clear, fresh Cheongju city. This plan introduces the image of Wooam-San, Moosim-Cheon(stream), Sangdang-SanSung(A mountain fortress) and elicit a sense of peace, symbolic of Cheongju. The significance of this project is that as the current cities are increasingly developed, small areas left alone in city are reconsidered and offered to the public as efficient, resting and active outdoor space.

• Korean Journal of Environmental Biology
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• v.24 no.3
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• pp.230-239
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• 2006

Nutrient over-enrichment as a consequence of anthropogenic loading leads to eutrophication, which has the detrimental effects on river and stream ecosystems. To examine dynamics of factors causing cultural eutrophication in a over-licked mountain stream due to anthropogenic loading, physicochemical parameters were measured from 5 stations in the upper Daecheon stream, Busan, from January 2002 to May 2003. The five study sites were located along the stream gradient. DC1 is upper most clean site, and DC5 is located at the lowest area. Wastewater was released into the stream from just upstream of DC2 site. Water column ammonium and phosphate concentrations were higher during winter than other seasons, while water column nitrate +nitrite concentration did not show clear seasonal variation. Water column ammonium, nitrate+nitrite and phosphate concentrations were lowest at DC1 and highest at DC2 in which waste water loading occurred. TOC and DOC, conductivity, turbidity, and BOD in the water column were also increased drastically at DC2, and then decreased at DC5. Sediment pore water phosphate concentrations during winter and spring were higher than those in summer and fall, while sediment pore water ammonium and nitrate +nitrite concentrations showed no seasonal trend. Sediment pore water ammonium and phosphate concentration were also increased at DC2 and slightly decreased at DC5, while sediment pore water nitrate+nitrite concentration was highest at DC5. Organic matter and inorganic nutrients at up-stream of Daechon stream significantly increased as a result of wastewater discharge, and the nutrient concentrations decreased at low-stream suggesting self-purification ability of the stream.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.846-850
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• 2007

In this study debris like branch or trash are washed and flowed from land to stream by rainfall runoff at mountain or urban stream specially rainy season. These kinds of debris are accumulated at hydraulic construct on the way of flow along the stream. The shape or ratio of like these accumulated debris are various according to the location where it is accumulated and the material what it is, so that it is influenced to be varied to flow characteristics. To be simple of accumulated debris shape, it was made experiments though the variation of open ratio and the shape of accumulated debris by lab experiment using straight channel with two piers. From the result, the water level is inverse proportion to open ratio, and the water level more sensitive to the debris‘ width than length at the same area of accumulated debris.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.19-23
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• 2010

Life cycle and secondary production of Nymphs of Nemoura gemma Ham and Lee were estimated by using specimens collected from a stream in Mt. Jumbong in the central Korean peninsula. N. gemma in the study stream was univoltine. Youngest nymphs were collected in April. They appeared to grow continuously until the emergence in early spring next year. The cohort production interval for the species was estimated as 399 days. The annual secondary production (ash free dry weight) estimated by removal-summation and the size-frequency methods were 582 and $786\;mg\;m^{-2}\;yr^{-1}$, respectively. Gut content analysis showed that N. gemma was a shredder.