• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.157-164
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• 2008

A modeling and visualization system of flood inundation in natural river, FloodViz, has been developed. Unsteady river flow and flood inundation are calculated by FLDWAV model. FLDWAV model and HEC-RAS model have been applied to a flood event at the same time to check model reliability. Simulation results of the two models showed good agreements. Flood propagation and inundation process can be analyzed accurately and easily by using visualization function of the FloodViz. Even though FloodViz users don't know well about both hydraulics and hydrology, they can understand flood inundation phenomena easily. This system can be used as a useful tool in forecasting flood inundation and observing the simulation results. Countermeasures for natural disaster prevention due to flood inundation can be established rapidly by using the FloodViz.

• The Korean Journal of Ecology
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• v.18 no.1
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• pp.157-177
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• 1995

Monthly changes in communities of benthic macroinvertebrates collected in the Suyong and Soktae stream of the Suyong river were investigated from September 1993 to August 1994. The total number of species collected during the study period ranged from seven to seventy six species according to pollution levels at the study sites. Monthly changes in species richness appeared differently in different taxonomic assemblages. In chironomids differences in species richness responding to different levels of saprobity were shown consistently as time proceeded. In Ephemeroptera species richness at the relatively clean sites responded sensitively to slight enrichment. In connection with species richness the monthly changes in densities in taxonomic assemblages also appeared to effectively represent environmental impacts. Species diversity generally represented the pollution status also, however the monthly variations at the study sites appeared to be relatively high. The clustering analysis showed that the communities collected at polluted sites were grouped closely, and the communities collected at the relatively clean sites were clustered to the same stream although the degree of community association was low, Through the Principal Component Analysis, the impact of Pollution was reflected in a great degree in overall community variations.

• Water for future
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• v.24 no.2
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• pp.109-119
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• 1991

The river-bed variation and the sediment transport in an alluvial stream are very complicated physical phenomena, especially in a stream where the dam construction prevents the supply of earth and sand from upper tributaries Therefore, the mathematical modeling is needed to establish. The purpose of this study is to apply river-bed variation to the Han River downstream by the conception of gradually varied unsteady flow instead of that of steady flow in order to decrease errors. For the variation and forecast of river-bed, the numerical analysis has been made in this study by way of discharge variation and river-bed variation. In conclusion, the numerical analysis shows that river-bed variation, sediment transport , and their forecast have similarity to natural phenomena and that river-bed variation is greatly affected in sediment transport by discharge variation and retention time(duration). Therefore, the errors of numerical analysis can be reduced by the application of flood data instead of continuous discharge data.

• Journal of Korean Society on Water Environment
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• v.27 no.6
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• pp.822-829
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• 2011

The purpose of the present study is to estimate the ecological instream flow for conservation and restoration of fish habitat in running water ecosystem which has very important status for stream environment. Estimation of the ecological instream flow in the present study was carried out by application of a two-dimensional depth averaged model of river hydrodynamics, River2D model. It can model fish habitat in natural streams and rivers and assess the quality of physical habitat accoriding to the species preferences for habitat suitability. Zacco platypus and Zacco temmincki were selected as target fish species in the study area of the Seomjin river. The Habitat Suitability Criteria (HSC) developed by Sung et al. (2005) were used for target fish species, life stages and habitat conditions in the study. Weighted usable area (WUA) was computed by the River2D model considering preferences of target fish species for velocity, depth, and channel substrate. The result revealed that the ecological instream flow of $10.0m^3/s$ is needed to maintain the target fish habitat at each life stage in the river.

• Journal of Environmental Science International
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• v.3 no.4
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• pp.409-416
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• 1994

This study was Performed to evaluate the contents of heavy metals in water, sediment and soil of the 7 different sampling points along the West Nakdong river, The results were as follows: the concentrations of Zn, p, Pb, Cd, Mn, Cu and As in the sediment were 197.48, 551.85, 67.01, 2.54, 491.39, 42.95 and 10.52ppm, respectively. The concentrations of Zn, p, Pb, Cd, Mn, Cu and As in the soil was 83.32, 482.89, 17.15, 1.02, 226.02, 26.15 and 7.29ppm, respectively. The concentration ratios of heavy metals In the water to the sediment were 593 - 12700 (Cd >> Cu > Zn > Mn > As > Pb) and that of the water to the soil were 152 - 5100 (Cu > Cd > Zn > Mn > As >Pb). The correlation coefficients of Cu and Pb weve high among the water, sediment and soil. Because the accumulation amounts of heavy metal in the sediment were high, the concentration of heavy metals in the sediment was higher than in soil. The correlation coefficient of heavy metals among water, sediment and soil was high (0.79 - 0.95). Key Words Distribution Characteristics, heavy metals, West Nakdong River.

• Journal of Species Research
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• v.5 no.1
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• pp.157-165
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• 2016

The hyporheic zone is an ecologically important area for investigating habitat biodiversity. However, only few studies have been conducted on this aspect in Korea. This study aimed to investigate the distribution of arthropod communities in the hyporheic zone of Nakdonggang River between 2012 and 2013. The meiobenthic arthropod communities found in the hyporheic zone were identified using a stereomicroscope and classified into 9 taxanomic groups. The abundance of arthropod communities was higher in the hyporheic zones of streams having well-formed sandbanks and gravelly areas. The arthropod communities found along the Nakdonggang River differed depending on the conditions of levees and the regions of the river from where they were collected. The frequency of species of the order Harpacticoida was high in the Nakdonggang main stream and western downstream region. The abundance of species belonging to Cyclopidae was high in the upstream region, midstream region, and eastern downstream region of the river. The frequency of species of the order Bathynellacea was high in the riverside parks or cement levees, but that of species belonging to Cyclopidae was high in the natural levees and gabion levees. Our findings suggested that arthropod communities preferred natural levees.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.579-592
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• 1994

A case study is presented where a fluvial system is modeled in three dimensions and compared to data gathered from a study of the Arkansas River. The data is unique in that it documents changes that affected a straight channel that was excavated within the river by the U.S. Army Corps of Engineers. Excavation plan maps and sequential aerial photographs show that the channel underwent massive deposition and channel migration as it returned to a more natural, meandering path. These records illustrate that stability of fluvial system can be disrupted either by catastrophic events such as floods or by subtle events such as the altering of a stream's equilibrium base level or sediment load. SEDSIM, Stanford's Sedimentary Basin Simulation Model, is modified and used to model the Arkansas River and the geologic processes that changed in response to changing hydraulic and geologic parameters resulting from the excavation of the channel. Geologic parameters such as fluid and sediment discharge, velocity, transport capacity, and sediment load are input into the model. These parameters regulate the frequency distribution and sizes of sediment grains that are eroded, transported and deposited. The experiments compare favorably with field data, recreating similar patterns of fluid flow and sedimentation. Therefore, simulations provide insight for understanding and spatial distribution of sediment bodies in fluvial deposits and the internal sedimentary structure of fluvial reservoirs. These techniques of graphic simulation can be contributed to support the development of the new design criteria compatible with natural stream processes, espacially drainage problem to minimize environmental disruption.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.27 no.3
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• pp.57-66
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• 2024

Coastline changes evolution of different intensities at all times under the influence of natural and anthropogenic effects. In this paper, we extracted the coastline of the Tumen River estuary from 1985 to 2020 using the digitizing method, verified the accuracy using the visual interpretation results, and analyzed the changes of the coastline of the Tumen River estuary through the area method and the baseline method. The results showed that the coastline showed an erosion trend during 35 years, with an average erosion rate of 0.05 m/year, an average erosion distance of 3.06 m, and an erosion area of 19.25 ha. Among the human activities that retarded the erosion of the coastline, these activities had a long-term impact on the natural morphology of the coastline.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.537-545
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• 2018

Determination of the time parameters such as the travel time in the design flood is very important. The travel time is mainly used for flood and river management, and the travel time of non flood season is used for maintenance flow and management of the river. Estimation of travel time for natural rivers is mainly based on the geomorphological factors of the basin. In addition to the topographical factors, the travel time is calculated by considering the factors of the runoff curve, velocity and rainfall intensity. However, there is no study on the estimation of travel time considering both the rainfall condition and the soil moisture accounting by the frequency period. Therefore, the travel time calculation is divided into the case of setting the Hwanggang Dam and the Imjin bridge water level station of Imjin river as the natural river considering rainfall condition by the frequency period and the soil moisture accounting, and the case of traveling the Imjin bridge water level station according to the condition of outflow of the Hwanggang Dam. For the sections set as natural rivers, the results were verified by comparing with the newly developed travel time calculation method. Based on the results, the travel times of the Hwanggang Dam outflow conditions were calculated. The time to travel in this study can be secured flood control of the Imjin river basin and time to prepare for danger when outflowing the the Hwanggang Dam.

• Korean Journal of Ichthyology
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• v.34 no.4
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• pp.231-243
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• 2022

To investigate the taxonomic status of undescribed species Acheilognathus sp. HR from Korean Acheilognathidae discovered from the Dalcheon River, a tributary of the Hangang River, molecular phylogenetic and morphological characteristics were compared and analyzed with previous studies. As a result of molecular phylogenetic analysis, A. sp. HR formed the same genetic clade as the five subspecies of Acheilognathus tabira, but formed a separate monophyletic group based on the unique genotype, showing clear differences. As a result of morphological analyses, the dorsal fin color in males is grayish and the nuptial coloration of the outer edge of the anal fin is white. The outer edges of the dorsal and anal fins are convexly rounded. A black blotch is present on the dorsal fin of the juvenile, but there is a black blotch absent on the dorsal fin of the small adult female. In the counts, the number of branched dorsal rays is 12~13. In the measurements, the length of the barbels is short and the body depth is deep. Therefore, the A. sp. HR of Hangang River is considered at the level of a distinct species distinguished from each other by the five subspecies of A. tabira by molecular phylogenetic, morphological, and limited distributional characteristics.