• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.15-25
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• 2006

Using kinematic wave equation, the influence of moving storms to runoff was analysised with a focus on watersheds. Watershed shapes used are the oblong, square and elongated shape, and the distribution types of moving storms used are uniform, advanced and intermediate type. The runoff hydrographs according to the rainfall distribution types were simulated and the characteristics were explored for the storms moving down, up and cross the watershed with various velocity. The shape, peak time and peak runoff of a runoff hydrograph are significantly influenced by spatial and temporal variability in rainfall and watershed shapes. A rain storm moving in the cross direction of channel flow produces a higher peak runoff than in the downstream direction and upstream direction. A peak runoff from a storm moving downstream exceeds that from a storm moving upstream. For storms moving downstream peak time was more delayed than for other storm direction in the case of elongated watershed. The runoff volume and time base of the hydrograph decreased with the increasing storm speed.

• Journal of Environmental Science International
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• v.8 no.4
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• pp.431-441
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• 1999

In this study, the regional frequency analysis is used to determine each subbasin drought frequency with reliable monthly precipitation and the L-Moments method which is almost unbiased and has very nearly a normal distribution is used for the parameter estimation of monthly precipitation time series in Nakdong river basin. As the result of this study, the duration of '93-'94 is most severe drought year than any other water year and the drought frequency is established as compared the regional frequency analysis result of cumulative precipitation of 12th duration months in each subbasin with that of 12th duration months in the major drought duration. The Linear regression equation is induced according to linear regression analysis of drought frequency between Nakdong total basin and each subbasin of the same drought duration. Therefore, as the foundation of this study, it can be applied proposed method and procedure of this study to the water budget analysis considering safety standards for the design of impounding facilities large-scale river basin and for this purpose, above all, it is considered that expansion of reliable preciptation data is needed in watershed rainfall station.

• Journal of Korean Society on Water Environment
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• v.32 no.3
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• pp.281-290
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• 2016

In the northernmost basin of the Bukhan River, pollution sources can have a concentrated distribution. In these basins, small streams show low flow with various and rapid water quality change in low pollutants load. Therefore, a water quality improvement plan of small streams and main stem will be necessary to establish the characteristics of small streams. This study selected a representative Hwacheon-gun in the northernmost basin of the Bukhan River. Hydro analysis was performed with GIS tools using DEM. A total of 152 small streams were listed. A total of 51 survey locations were selected after applying the selection criteria. Flow rate and water qualities were investigated. Pollution sources and pollutants loads were calculated for each basin. Pollution grade and typological classification were performed by cluster analysis using standardized environmental condition factors. As a result, G04, G01, H01 locations were found to have the worst pollution grades whereas J01, P01, and P02 had less pollution. Typological analyses were able to classify six types for the surveyed small streams. An effective water quality improvement plan was obtained based on the results of pollution grade and typological analysis using environmental condition factors of this study.

• The Journal of Engineering Research
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• v.8 no.1
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• pp.107-118
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• 2006

The difficulties to build a 3-dimensional water quality model for the coastal water quality improvement and the environmental recovery estimation are the lack of periodic observed data and the many problems to observe continuously. I observed the rainfall and non-point pollutants outflow patterns in Jinhae-Masan basin as mid-step researches for the water quality simulation and management method development in a coastal area. I applied Landsat image system and Geographic Information System to analyze the runoff and non-point pollutants outflow patterns. A water quality simulation model (SWMM) applied to Jinhae-Masan basin with results of the land use distribution, non-point pollution loads, and watershed informations from GIS(IDRISI used). I proposed some improved survey and GIS application methods reflect upon the pollutant characteristics from the observed non-point pollutant outflow patterns.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2003.04a
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• pp.517-522
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• 2003

Exact estimation of evapotranspiration is important to understand natural phenomena and social issues associated with the climate such as irrigation scheme, reservoir water management, and many other meteorological and climatological problems. To overcome limits of point measurement of evapotranspiration, several models have been developed through the techniques of remote sensing and Geographical Information System. SEBAL model is one of them, based on the energy balance equation, and it has a lot of advantages such as that it requires relatively small empirical relations. In this study, the SEBAL model has been calibrated and validated in Geumgang upper basin, Bochung-stream basin, Korea with 5 satellite images Landsat 5 TM. In validation, the results of SEBAL model were compared with those by Merton method. After validation, the spatial and temporal characteristics of the distribution of evapotranspiration within the basin were analyzed with 3 factors, the aspect of slope, the angle of slope, and the land cover.

• Journal of environmental and Sanitary engineering
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• v.12 no.3
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• pp.31-39
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• 1997

The seasonal and spatial changes in dissolved organic carbon(DOC) in Lake Kasumigaura, a shallow and eutrophic lake, were analyzed from October 1992 to October 1995. The proportion of T-DOC was classified by labile(L-DOC) and refractory DOC(R-DOC) on the basis of long-term incubation, fractionated the molecular weight of T-DOC by ultrafiltration. The porewater DOC were measured at sedimental surface of the central basin in order to evaluate the DOC released from the sediment. The proportion of L-DOC and R-DOC were accounted for about 15% and 85% of T-DOC in the central basin, respectively. The molecular weight(MW) distribution occupied some 60% of the low and medium MW. The horizontal variation of T-DOC concentrations trended to higher in the central basin than in the inlet of influent rivers, because of contribution by autochthonous organic carbon loading. The seasonal variation of T-DOC showed to higher summer than winter in the inlet of influent, but at the central basin it fluctuated little seasonally. During the high increase of porewater DOC in 1994 evaluated the high release possibility from the sediment surface (10cm). The present study suggests that autochthonous organic carbon loading must be controlled for improving the water quality of the eutrophic lakes.

• Journal of The Geomorphological Association of Korea
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• v.26 no.1
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• pp.79-91
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• 2019

This study analyzed the distribution of fluvial landforms, fault-related geomorphic features and lineaments around the area of Ungchon-Ungsang in the Dongrae Fault, and discusses the charateristics of geomorphic development based on those. As a result, the NE-SW lineaments are predominantly developed in many numbers within the study area, and the NW-SE or N-S secondary lineaments are developed induced by multiple deformation with the Yangsan Fault. Geomorphologically, the early tectonic history of the Ungchon-Ungsang basin is largely divided into three stages ; 1) the Tertiary fault activity and formation of fracture zone, 2) development of erosional basin, 3) local crustal movements and development of fault-related topography. It is assumed that alluvial fans, deflected channel and stream piracy were formed by local tectonic movements related to faultings during the Quaternary.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.2
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• pp.207-218
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• 2017

Seawater with salinity of 32.5 psu or less is observed in the southern Japan/East Sea (JES) every autumn. It is confined to a surface layer 30-45 m in depth that expands to cover the entire JES in October. Two sources of "autumn low-salinity water" have been identified from historical hydrographic data in the western JES: East China Sea (ECS) water mixed with fresh water discharge from the Yangtze River (Changjiang) and seawater diluted with melted sea ice in the northern JES. Low-salinity water inflow from the ECS begins in June and reaches its peak in September. Low-salinity water from the northern JES expands southward along the coast, and its horizontal distribution varies among years. A rare observational study of the entire JES in October 1969 indicated that water with salinity less than 33.0 psu covered the southwestern JES; the lowest salinity water was found near the Ulleung Basin. In October 1995, the vertical distribution of salinity observed in a meridional section revealed that water with salinity of 33.6 psu or less was present in the area north of the subpolar front.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.233-242
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• 2011

This study quantified directional properties of channel network and hill slope for a river basin by applying the von Mises distribution, also examined the relation between them. Ultimately, it was examined that whether the directional properties of channel network and hill slope have a certain relation, which might be considered to the rainfall-runoff modeling. From the results derived by analyzing the Naesung stream basin, the von Mises distribution was found well to explain the directional characteristics of directional properties of channel network. There was a clear relation between directional properties of channel network and hill slope. The higher-order streams also showed very obvious modal characteristics. The results derived in this study could be helpful to estimate more quantitatively the difference in the runoff response with respect to the directional properties of channel network and hill slope.

• Water for future
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• v.15 no.3
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• pp.37-47
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• 1982

In the past, the design flow of the urban storm drainage systems has been used largely on a basis of empirical and experience, and the rational formula one of empirical method has been widely used for our country, as well as world wide. But the empirical method has insufficient factor because minimal consideration is given to the relationship of the parameters in the equation to the processes being considered, and considerable use of experience and judgment in setting values to the coefficients in the equation is made. The postcomputer era of hydrology has brought an acceleration development of mathematical methods, thus mathematical models are methods which will greatly increase our understanding in hydrology. On this study, a simple mathematical model of urban presented by British Road Research Laboratory is tested on urban watersheds in Ju An Ju Gong Apartment. The basin is located in Kan Seog Dong, Inchon. The model produces a runoff hydrograph by applying rain all to only the directly connected impervious area of the basin. To apply this model the basin is divided into contributing areas or subbasins. With this information the time area for contributing is derived. The rainfall hyetograph to design storm for the basin flow has been obtained by determination of total rainfall and the temporal distribution of that rainfall determined on the basis of Huff's method form historical rainfall data of the basin. The inflows from several subbaisns are successively routed down the network of reaches from the upstream end to the outlet. A simple storage routing technique is used which involves the use of the Manning equation to compute the stage discharge curve for the cross-section in question. To apply the model to a basin, the pattern of impervious areas must be known in detail, as well as the slopes and sizes of all surface and subsurface drains.