• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.507-522
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• 2015

In this study, some of the model verification results of STREAM (Spatio-Temporal River-basin Ecohydrology Analysis Model), a newly-developed hybrid watershed model, are presented for the runoff processes of nonpoint source pollution. For verification study of STREAM, the model was applied to a test watershed and a sensitivity analysis was also carried out for selected parameters. STREAM was applied to the Mankyung River Watershed to review the applicability of the model in the course of model calibration and validation against the stream flow discharge, suspended sediment discharge and some water quality items (TOC, TN, TP) measured at the watershed outlet. The model setup, simulation and data I/O modules worked as designed and both of the calibration and validation results showed good agreement between the simulated and the measured data sets: NSE over 0.7 and $R^2$ greater than 0.8. The simulation results also include the spatial distribution of runoff processes and watershed mass balance at the watershed scale. Additionally, the irrigation process of the model was examined in detail at reservoirs and paddy fields.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.491-506
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• 2015

Distributed models represent watersheds using a network of numerous, uniform calculation units to provide spatially detailed and consistent evaluations across the watershed. However, these models have a disadvantage in general requiring a high computing cost. Semi-distributed models, on the other hand, delineate watersheds using a simplified network of non-uniform calculation units requiring a much lower computing cost than distributed models. Employing a simplified network of non-uniform units, however, semi-distributed models cannot but have limitations in spatially-consistent simulations of hydrogeochemical processes and are often not favoured for such a task as identifying critical source areas within a watershed. Aiming to overcome these shortcomings of both groups of models, a hybrid watershed model STREAM (Spatio-Temporal River-basin Ecohydrology Analysis Model) was developed in this study. Like a distributed model, STREAM divides a watershed into square grid cells of a same size each of which may have a different set of hydrogeochemical parameters reflecting the spatial heterogeneity. Like many semi-distributed models, STREAM groups individual cells of similar hydrogeochemical properties into representative cells for which real computations of the model are carried out. With this hybrid structure, STREAM requires a relatively small computational cost although it still keeps the critical advantage of distributed models.

• Journal of the Korean earth science society
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• v.24 no.4
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• pp.290-302
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• 2003

This study was carried out to evaluate geochemical properties for stream sediments, surrounding soils, sludge collected in the drainage pipe of leachate and waters (stream water, groundwater, leachate) around the Pungam Landfill in Gwangju city. The stream sediments don't show any systematic trend of contents from upstream to downstream. The most enriched major element in the stream sediments is Fe (up to 7.08wt.% in GJ-23). Though stream sediment GJ-23 and GJ-34 were enriched by some heavy metals (eg. As, Cu, Zn), they do not constitute serious problems for environment consideration. The concentration of Fe (35.lwt.%) and As (38ppm) are significantly high in the GJ-8, which is soil specimen adjacent to leachate reservoir. The sludge (GJ-7) shows very high concentrations of As, Mn, Cr, Pb. In particular, the Cr content is 45.6 ppm, which exceeds the permitted level. The leachate is characterized by high TDS (2210-2470mg/L) and high electric conductivity (468, 530ms/cm), and enriched in both cation (Na, K) and anion (HCO$_3$). The leachate(PK-3) had a relatively high concentration of Cl, and is plotted in Na-Cl type on the Piper's diagram. The NO$_3$-N of the groundwater and stream water exceeded the permitted levels for drinking water.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.1 s.12
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• pp.51-56
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• 2004

In this study, the variation of water quality in Osan stream was investigated through continuous monitoring, and mass balance and metabolism occurred into water body were estimated to set up effective management plan for water quality of small urban stream. From the results of continuos investigation of water quality in Osan stream, the things written as follows must be previously done to improve water quality of main stream. Firstly, it need that effective management plan for tributaries must be set up to improve the water quality in main stream. Secondly, the counter plan for re-eruption of pollutants from sediment in main-stream is required to prevent inner pollution. In this study, we showed that small urban stream can be managed effectively by simple investigation to prevent deterioration of water quality. Therefore continuous monitoring for water quality in stream is important to improve water quality, furthermore matter cycle and mass balance happening in the stream environment must be correctly estimated to make up healthy stream environment.

• The Korean Journal of Ecology
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• v.19 no.5
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• pp.365-373
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• 1996

A survey was carried out to investigate the contamination of streams by the acid mine drainage originated from the abandoned coal mines and coal refuse piles. The physico-KDICical characteristics such as pH, sulfate and elements concentrations in the water and sediment in streams were analyzed. Microbial activity in the sediment was evaluated by measuring dehydrogenase activities. At sites contaminated by acid mine drainage, the pH of the water and sediment declined to acidic range from neutral due to the accumulation of sulfate. The dehydrogenase activity ranged from 12 to $170{\mu}g-TPF{\cdot}g-dry\;soil^{-1}{\cdot}24h^{-1}$ at the contaminated sites, whereas uncontaminated sites had activities of 1,176~4,259 ${\mu}g-TPF{\cdot}g-dry\;soil^{-1}{\cdot}24h^{-1}$. The dehydrogenase activity was significantly affected by low pH of the sediment, indicating that high concentration of sulfate inhibited microbial activity. The concentrations of heavy metals such as Pb and Fe in contaminated sdeiment (37~46 ppm Pb; 46,000~464,000 ppm Fe) were much higher than those in the uncontaminated sediment. The concentration of Al in the contaminated water acidfied by coal mine drainage was in the range of 11 to 42 ppm. Compared with those in the uncontaminated sediment, the concentrations of Mn, Mg and Ca in contaminated sediment were low because of the leaching from soil to water by the acidfied stream water.

• Journal of Wetlands Research
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• v.10 no.3
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• pp.27-35
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• 2008

Sediment cores were obtained from Upo and Mokpo in Upo Wetland and core samples were divided by depth into 20 ~ 21 subsamples. The heavy metal concentrations of Fe, Mn, Zn, AS, Cu, Cd, Ni, Pb, and Cr in the sediments of each depth were determined by ICP-MS. The texture of sediemnts from Upo Wetland appeared to be clayey silt with average grain size of $7.52{\sim}11.15{\mu}m$ for physical properties. It was found to have a clear tendency of depth profile with respect to TOC and ignition loss. Organics were stabilized in the range of 0.5 ~ 0.7 % TOC and 8 ~ 9 % ignition loss in 30 years, whereas, the surficial sediments have the highest concentrations of about 3.0 % of TOC and 13 ~ 15 % ignition loss. Those are much higher than the values of the main stream, the Nakdong River, which reflects the deposit of biodegradable organics from plants and other lifes. The vertical distribution of heavy metals in two sediment cores was investigated to elucidate historical trends of heavy metals deposited into Upo wetland. The depth profile concentrations of each heavy metal were compared and discussed with the Concensus-Based Sediment Quality Guidelines for freshwater ecosystems. All the Cd data for the vertical distribution in the sediments were detected above PEC value for Cd, which predict harmful effects on sediment-dwelling organisms expected to occur frequently. The concentrations of Zn, Cu, and Cr in all sediment samples for depth profile were detected below the TEC values, which provided a basis predicting the absence of toxicity by Zn, Cu, and Cr.

• 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 Geomorphological Association of Korea
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• v.26 no.3
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• pp.1-17
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• 2019

Naeseongcheon is Korea's representative sand stream, and it is one of the regions where the dynamic changes of various river topography developed in the sand bed can be observed. Most of drainage area near of the river channel are formed with Daebo granite, and the granite weathering zone is developed at the surface of hill. Due to the massive input of sediment flux, braided channel reaches are found some of the area. However, the results of the study shows that the alluvial layer is very thin in some reaches. In addition, bedrock or weathered materials, including the Tors are exposed at the channel beds. On the other hand, during the flood, a considerable amount of sediment was introduced, causing the massive sediment to be close to 1m thick. In addition, despite the short distance, large changes in the particle size and sorting of the sediment were observed. Vegetation, on the other hand, has been shown to have a significant effect on the development of the overall channel bed topography, as reported in previous studies. In small floods or low water levels, vegetation's protection role of the surface is predominates, but in large flood conditions, herbaceous loss at the surface of the point bars, accelerating the erosion of surface.

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.44-51
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• 2005

Fractional composition and mobility of some heavy metals in sediments from Okdong stream are investigated. The fractional scheme for heavy metals in the sediment was established for five chemically defined heavy metal forms as adsorbed fraction, carbonate fraction, reducible fraction, organic fraction, and residual fraction. The most abundant fraction heavy metals in the sediments is reducible and secondly abundant is organic fraction. Adsorbed fraction is minor part of the total heavy metals. Mobilization of heavy metals in the sediments from Okdong stream occur $19.8{\sim}56.7%$ of total cadmium concentrate. The most abundant fraction of the sediment metal is organic fraction in Cu, Pb metals investigated. Labile fraction of sediment metals are $0.5{\sim}48.5%$ of total Zn, $2.6{\sim}48.1%$ of total Pb, and $0.2{\sim}36.9%$ of total Cu, respectively. Most of labile fraction consists of reducible fraction for Cd, Zn, adsorbed fraction for Pb, reducible fraction for Cu, adsorbed fraction for Ni. The Mobilization of Zn and Cu is most likely to occur when oxygen depletes and that of Pb and Ni occurs when physical impact, oxygen depletion and pH reduction.

• Economic and Environmental Geology
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• v.33 no.4
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• pp.261-271
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• 2000

In order to evaluate the environmental impact of U anormaly in the drainage system around the Shinbo talc mine area, U contents, their distribution patterns, bioaccumulation and a-radioactivity in stream water, stream sediments and aquatic organisms were investigated. The U contents of stream water attenuated with increasing distance from the mine area. The same attenuation pattern is shown in stream sediments from mine to 0.75 km downstream, although these contain highly enriched U contents (24~83 mg/kg) comparing with the international average concentration of surface soils (0.79~11 mg/kg). However, U content increases abruptly in sediment at 1.5 km downstream, probably due to detrital migration and rediposition of U enriched sediments. Futhermore, enriched U in downstream sediments occur in high proportions of carbonate and Fe-Mn oxide bounded forms, which show high potential of a secondary pollution source. For aquatic organisms, bio accumulation degree of U are in the order: aquatic larvae>black snail>mountain frog>crawfish. Cultured trout by the U enrich groundwater (387 ${\mu}g$/l) shows U accumulation in the part of branchia (CRs 5.25) and bones (CRs 11.2) but not in flesh (CRs 0.03). Total a-radioactivity have been measured in the level as 0.47 nCi/l for groundwater, 2.94~18 nCi/kg${\cdot}$DW for organisms and 93~328 nCi/kg${\cdot}$DW for sediments.