• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.262-272
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• 2005

This study was undertaken to obtain design concentrations for the natural system treating stream water flowing into estuarine lake(Sapgyo). This lake has three major, so called, national-class streams: one is Gokgyo flowing through two medium-size municipal areas and the others are Muhan and Sapgyo placed in mostly rural area nested with some small towns. The results of three year's investigation showed big changes in water quality during the period between dry and wet seasons. Nitrogen concentration usually decreases as the flow rate increases. The change of phosphorus concentration in Gokgyo was the same pattern as nitrogen, but in other two streams it was inversely related with flow rates. This is probably due to the chemical property of the particles washed out from the different stream basins during wet season. It was found that about 40 to 60% of the total nitrogen are in soluble form and on average, 35% of the total phosphorus consists of dissolved-P. Representative concentration of these streams has to be separately determined based on dry and wet season. TDS and SS could be indicating parameters useful to depict and characterize a change of water quality with respect to flow rate because their measurement is easy and also includes a small analytical error. TDS values measured during dry season are related with high nitrogen concentration while during wet season, SS values effectively reflect a high concentration of phosphorus. For design purpose, cumulative concentration distribution graph presented in this paper can be directly or indirectly applied to other streams through a brief comparative and verificative study.

• Spatial Information Research
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• v.6 no.1
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• pp.91-102
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• 1998

The objectives of this research were to develop fish-habitat relationship models which can be used to estimate fish species riclmess of small and medium rivers in Korea, and test the accuracy of the models. The models are based on the Aquatic GAP Analysis model in the New York Cooperative Fish & Wildlife Research Unit (19%), and they employ three habitat factors; river size, physical habitat, and water quality of each river segment. Model 1 and model II are based on the water quality standard for life support of EP A and the water quality class of Korea, respectively. Test sites for this study include one urban stream and three less spoiled tributaries of the Han River. The results of this research can be summarized as follows. First, the number of habitat types identified by model I and model II are nine and 14, respectively. Second, the average accuracy of the three distribution maps of rare or endangered fish species are 80.6% (model 1) and 81.2% (model II). Third, the accuracy of fish species richness are 94% (model 1) and 95% (model II), and the water quality is the most important factor affecting fish species richness. Fourth, the accuracy of fish species list are 50.5% (model 1) and 68.7% (model II), but the accuracy of less spoiled stream segments and that of polluted stream segments are 67.1% and 86.5%, respectively. Finally, it can be concluded that the overall performance of model II is better than that of model I at our test sites.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1181-1194
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• 2018

This study suggests a novel approach of estimating stream flow discharge using the Synthetic Aperture Radar (SAR) images taken from 2015 to 2017 by European Space Agency Sentinel-1 satellite. Fifteen small to medium sized rivers in the Han River basin were selected as study area, and the SAR satellite images and flow data from water level and flow observation system operated by the Korea Institute of Hydrological Survey were used for model construction. First, we apply the histogram matching technique to 12 SAR images that have undergone various preprocessing processes for error correction to make the brightness distribution of the images the same. Then, the flow estimation model was constructed by deriving the relationship between the area of the stream water body extracted using the threshold classification method and the in-situ flow data. As a result, we could construct a power function type flow estimation model at the fourteen study areas except for one station. The minimum, the mean, and the maximum coefficient of determination ($R^2$) of the models of at fourteen study areas were 0.30, 0.80, and 0.99, respectively.

• Current Research on Agriculture and Life Sciences
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• v.29
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• pp.11-19
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• 2011

This research gives weight to establish practical improvement based on analysis of the landscape ecological character and value to realize the importance of small wetland and stream in cultivated areas functioning as a residual landscape element in rural landscape and to deal with ecological depression effectively. The results of summary are as follows. 1) The results of landscape ecological character analysis of wetlands biotop in total of 7 sites, for example, size of surface in site 5 was widely formed about $10,600m^2$, which was assessed satisfactory in terms of slope of waterfront, width of hedgerow, vegetation condition of composition and so on. Also, The number of flexibility showed 2 in site 8-1, the highest, and morphological diversity showed 1.47, the highest. 2) The results of problem analysis of wetland biotop, most of wetlands are analyzed that the width of hedgerow was below 1m. Also, the 4 wetlands in site 8 are appeared that hard to live slope vegetation in there because of slope of waterfronts are above $45^{\circ}$. 3) The results of landscape ecological character analysis of stream in total of 6 sites, for example, width of waterfront in site 4 showed 55m, the widest, and investigated consist of natural ingredients such as soil, rock, gravel. However, width of waterfront in site 2-2 showed 4m, the narrowest, and inclined angle of slope was formed a right angle. 4) The results of problem analysis of stream, width of waterfront hedgerow in site 2-1 showed about 5m, which was very narrower than width of waterfront, and toxic chemicals discharged from near cultivated area without any filtering. Also, all areas of site 2-2 was formed concrete, and was assessed dissatisfactory in terms of capacity of nature purification, flood control, habitat living space because of straight stream. 5) Based on the result above landscape ecological character and problem analysis, main improvement guidelines are set in terms of shape, vegetation, topography in case of wetlands, and which are set in terms of vertical, horizontal structure in case of stream.

• Korean Journal of Ichthyology
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• v.22 no.4
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• pp.230-237
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• 2010

Histological observation on the seasonal variation of mucus cells of the mud loach Misgurnus mizolepis inhabiting a natural stream was carried out on three skin regions (dorsal, lateral and occiput) from March 2008 to February 2009. Our results showed no differences in general morphology by season, but the mucus cells of the epidermis showed significant seasonal change in their size and number as the water temperature changed. The ratio of surface area of the mucus cell layer and mucus cells, and the number of mucus cells in surface area of the epidermis were the greatest in the cold winter and the least in the hot summer in all regions of the epidermis. In particular, the occiput seemed to be a very sensitive region in response to environmental change, showing wide fluctuations in the size of mucus cells throughout the year and a great change in between seasons, especially from late autumn to early winter when the temperature decreased. As the temperature became colder, a small and spherical-shaped mucus cell was transformed into a large and elongated columnar form with a lot of secreted mucus material in a superficial layer of the epidermis. From our results, we can safely surmise that cold temperature is an important environmental factor having a close relationship with the modification of mucus cells of M. mizolepis in winter.

• Journal of the Korean association of regional geographers
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• v.12 no.3
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• pp.352-363
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• 2006

The purpose of this paper is to analyze changes in the depositional landform in the channel of Cha-cheon, a branch stream of Nakdong river(main stream) since the artificial straight channel has been constructed in 1973. The results of analyses are as follow. First, the Cha-cheon has flooded over one time in a year, and flowed backward over three times annually, according to analyze the data of the Hyeonpoong Gauging Station of rainfall and water level during a decade(1993$\sim$2002). Second, the flood plain within the artificial straightened channel has a nearly plain profile between the small dike and last riffle(point A). Deposits thickness of flood plain reduce gradually toward upstream. Third, grain size distribution of the flood plain deposits(0$\sim$20cm) within the artificial straightened channel has a coarsening trend in downstream reach of C point. It implies that the backward flow of Nakdong river(the main stream of Cha-cheon) make effect on the depositional mechanism of lowest reach in Cha-cheon. Finally, the result of analyzing grain size distribution of the flood plain deposits(0$\sim$20cm) within the artificial straightened channel implies that the c-point is the boundary between the vertical deposition of suspended load due to the backward flow of Nakdong river and the deposition of bed load supplied from hillslope of Cha-cheon basin.

• Korean Journal of Ichthyology
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• v.33 no.4
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• pp.278-286
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• 2021

The habitat characteristics and feeding ecology of the Siberian stone loach Barbatula toni were investigated in Bukcheon (Stream), Eocheonri, Ganseong-eup, Goseong-gun, and Gangwon-do, Korea from January to December 2013. B. toni lived in rapids or slow rapids from the upper stream to downstream, with the largest number of inhabitants in the middle-downstream regions. As a result of analyzing habitat preferences by age, 0+ and 1+ to ≥3+ showed differences. Ages of 0+(juveniles) lived mainly in rapidly flowing water (37.6±26.79 cm/sec) and low water depths (13.3±9.47 cm) in the pebble bottoms (substratum particle size 9.5±6.66 cm), but ages 1+ to ≥3+ lived mainly in relatively slowly flowing water (13.3±17.33 cm/sec) and relatively deep depths (25.9±10.31 cm) in stone and large stone bottoms (substratum particle size 18.0±7.63 cm). B. toni was mainly eaten from March to December when the temperature was above 5℃, and the amount of food eaten peaked in June and October. Their main food sources analyzed by the index of relative importance (IRI) included Diptera (57.0%), Ephemeroptera (29.3%), and Trichoptera (13.5%). The juveniles (age 0+) fed on small-sized prey such as Diptera and Trichoptera whales, but as they grew, they mainly ate large-sized Ephemeroptera. These feeding habits and changes in food according to the growth of B. toni were very similar to those of sibling species, B. nuda.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.1009-1022
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• 2004

Smoothing is a transmission plan where variable rate video data is converted to a constant bit rate stream. Among them are CHA, MCBA. MVBA, e-PCRTT and others. E-PCRTT algorithm, which was improved from PCRTT, restricts the number of rate changes with fixed-size run. This causes unnecessary rate changes and may not guarantee QoS when buffer size is small. In this paper. a smoothing algorithm is pro-posed, where the number of rate changes are not limited and the size of run can be flexible, in order to overcome the shortcomings of e-PCRTT. Experiments demonstrated that the proposed algorithm such as e-PCRTT. In order to show the performance, var-ious evaluation factors were used such as the nember of rate changes, buffer size to maintain QoS, and so on.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.627-637
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• 2022

To know the magnitudes of extreme floods for various sizes of watersheds, massive streamflow data is fundamentally required. However, small/medium-size watersheds missed streamflow data because of the lack of gauge stations. In this study, the Streamflow Propagation Method (SPM) was applied to generate streamflow data for small/medium size watersheds with no measurements. Based on the generated streamflow data for ungauged watersheds at three different locations (i.e., Chungju Dam (CJD), Seomjin Dam (SJD), and Andong Dam (ADD) watersheds), the scale ranges of extreme floods were evaluated for different sizes of ungauged watersheds by using the specific flood distribution analysis. As a general result, a range of specific floods decreases with increasing watershed size. The distribution of the specific flood in the same size of a watershed possibly depends on the size and topography of the watershed area. The delivered equations were compared to show the relations between the specific flood and sizes of watersheds. In the comparisons of equations, the Creager envelope curve has the higher potential to represent the maximum flood distribution for each watershed. For the generalization of the maximum flood distribution for three watersheds, optimized envelop curves are obtained with lower RMSE than that of Creager envelope curve.