• Journal of Environmental Science International
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• v.14 no.12
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• pp.1185-1194
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• 2005

The runoff characteristics of non-point source pollutions in the municipal area of Jeonju were investigated and analyzed by using the SWMM (Storm Water Management Model). The flow rates and water qualities of runoff from two types of drainage conduits were measured respectively. One was a conventional combined sewer system and the other was a separated sewer system constructed recently From August to November in 2004, investigations on two rainfall events were performed and flow rate, pH, BOD, COD, SS, T-N and T-P were measured. These data were also used for model calibration. On the basis of the measured data and the simulation results by SWMM, it is reported that $80-90\%$ of pollution load is discharged in the early-stage storm runoff. Therefore, initial 10-30 mm of rainfall should be controlled effectively for the optimal treatment of non-point source pollution in urban area. Also, it was shown that the SWMM model was suitable for the management of non-point source pollution in the urban area and for the analysis of runoff characteristics of pollutant loads.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.3
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• pp.17-27
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• 2008

In this study, three different unit hydrograph methods (Snyder, SCS, Clark) in the HEC-HMS were compared to find better fit with the observed data in the small agricultural watershed. Baran watershed, having $3.85km^2$ in size, was selected as a study watershed. The watershed input data for HEC-HMS were retrieved using HEC-GeoHMS which was developed to assist making GIS input data for HEC-HMS. Rainfall and water flow data were monitored since 1996 for the study watershed. Fifty five storms from 1996 to 2003 were selected for model calibration and verification. Three unit hydrograph methods were compared with the observed data in terms of simulated peak runoff, peak time and total direct runoff for the selected storms. The results showed that the coefficient of determination ($R^2$) for the observed peak runoff was $0.8666{\sim}0.8736$ and root mean square error, RMSE, was $5.25{\sim}6.37\;m^3/s$ for calibration stages. In the model verification, $R^2$ for the observed peak runoff was $0.8588{\sim}0.8638$ and RMSE was $9.57{\sim}11.80\;m^3/s$, which were slightly less accurate than the calibrated data. The simulated flood hydrographs were well agreed with the observed data. SCS unit hydrograph method showed best fit, but there was no significant difference among the three unit hydrograph methods.

• Journal of Environmental Health Sciences
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• v.31 no.6
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• pp.467-474
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• 2005

The runoff characteristics of combined sewer overflow(CSO) in the urban area of Jeonju were investigated and analyzed by using the SWMM (Storm Water Management Model) and GIS. From August to November 2004, investigations on two rainfall events were performed and flowrate, pH, BOD, COD, SS, T-N and T-P were measured. these data were used for model calibration. Using GIS technique, watershed characteristics of study area were calculated. that is, divide into sub_basin, total width, slope, make soil map etc. On the basis of the measured data and the simulation results by SWMM, it could be known that the $80-90\%$ of pollution load are discharged in early-stage storm runoff. SMC(site mean Concentration) for combined sewer system area were BOD 28.1, COD 31.5, SS 186 ppm etc. this is shown that during the rain fall, high concentration of waste was loaded to receiving water. Unit loads of combined sewer system area were BOD 306, COD 410, SS 789, T-N 79, T-P 6.8 kg/ha/yr.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1443-1454
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• 2014

In this study, we assess impact of spatial resolution of radar rainfall and a distributed hydrologic model on parameter estimation and rainfall-runoff response. Radar data measured by S-band polarimetric radar located at Mt. Bisl in the year of 2012 are used for the comparative study. As different rainfall estimates such as R-KDP, R-Z, and R-ZDR show good agreement with ground rainfall, R-KDP are applied for rainfall-runoff modeling due to relatively high accuracy in terms of catchment averaged and gauging point rainfall. GRM (grid based rainfall-runoff model) is implemented for flood simulations at the Geumho River catchment with spatial resolutions of 200m, 500m, and 1000m. Automatic calibration is performed by PEST (model independent parameter estimation tool) to find suitable parameters for each spatial resolution. For 200m resolution, multipliers of overlandflow and soil hydraulic conductivity are estimated within stable ranges, while high variations are found from results for 500m and 1000m resolution. No tendency is found in the estimated initial soil moisture. When parameters estimated for different spatial resolution are applied for other resolutions, 200m resolution model shows higher sensitivity compared to 1000m resolution model.

• Korean Journal of Remote Sensing
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• v.11 no.2
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• pp.1-16
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• 1995

This study is conducted to eveluate the potential of a GIS to assist an application problem. GIS has been applied to rainfall-runoff modeling over Soyang area. Various rainfall-runoff models have been developed over the years. A distributed rainfall-runoff model is selected because it considers the topographic characteristics over the basin. GIS can handle the spatial data to enhance the modeling. GRASS-a public domain GIS S/W-is used for GIS tools. Digital database is generated, including soil map, vegetation map, digital elevation model, basin and subbasin map, and water stream. The inpu data for the model has been generated and manupulated using GIS. The database, model and GIS are integrated for on-line operation. The inflow hydrographs are tested for the flood of Sept., 1990. This shows the promising results even without the calibration.

• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.285-300
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• 2003

An event-based, kinematic, infiltration-excess, and distributed rainfall-runoff model using weather radar and Geographic Information System(GIS) was developed to acknowledge and account lot the spatial variability and uncertainty of several parameters relevant to storm surface runoff and surface flow The developed model is compatible with raster GIS and spatially and temporally varied rainfall data. To calibrate the model, Monte Carlo simulation and a likelihood measure are utilized; allowing for a range of possible system responses from the calibrated model. Using rain gauge adjusted radar-rainfall estimates, the developed model was applied and evaluated to a limited number of historical events for the Ralston Creek and Goldsmith Gulch basins within the Denver Urban Drainage and Flood Control District (UDFCD) that contain mixed land use classifications. While based on a limited number of Monte Carlo simulations and considered flood events, Nash and Sutcliffe efficiency score ranges of -0.19∼0.95 / -0.75∼0.81 were obtained from the calibrated models for the Ralston Creek and Goldsmith Gulch basins, based on a comparison of observed and simulated hydrographs. For the Ralston Creek and Goldsmith Gulch basins, Nash and Sutcliffe efficiency scores of 0.88/0.10, 0.14/0.71, and 0.99/0.95 for runoff volume, peak discharge, and time to peak, respectively, were obtained from the model.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.3
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• pp.103-118
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• 2012

A distributed model can easily obtain discharge at any grids spatially distributed in a watershed. But if there are subwatersheds which have various characteristics in a watershed, it is needed to apply a model calibrated at each subwatershed to obtain reliable simulation results for each subwatershed. In this study, a multi-site calibration module that can calibrate a distributed model at each subwatershed using observed flow data was developed. Methods to select multi-site calibration parameters, to apply subwatershed parameters, and to set subwatershed network information are suggested. Classes to implement multi-site calibration technique are designed and a GUI was developed, and procedures for runoff modelling using subwatershed parameters were established. Multi-site calibration module was applied to Sunsan watershed($977km^2$) of Nakdong river basin. Application results showed that the multi-site calibration technique could be applied effectively to model the calibration for each subwatershed, and the simulation results of subwatershed were improved by the application of multi-site calibration.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.3_4
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• pp.34-47
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• 1995

It is experienced fact as a regular annual event that the structure to he designed on unreasonable flood for the agricultural structures including reservoirs have been brought not only loss of lives, but also enormous property damage. For the solution of this problem at issue, this study was conducted to develop an optimal runoff hydrograph model by comparison of the peak flows and time to peak between observed and simulated flows derived by linear time-invariant and linear time-variant models under the condition of having a short duration of heavy rainfall with uniform rainfall intensity at nine small watersheds which are within the range of 55.9 to 140.7 square kilometers in area in Han, Geum, Nagdong and Yeongsan Rivers. The results obtained through this study can be summarized as follows. 1. Storage constants and Gamma function arguments were calculated within the range of 1.2 to 6.42 and of 1.28 to 8.05 respectively by the moment method as the parameters for the analysis of runoff hydrograph based on linear time-invariant model. 2. Parameters for both linear time-invariant and linear time-variant models were calibrated with nine gaged watershed data, using a trial and error method. The resulting parameters including Gamma function argument, N and storage constant, K for linear time-invariant model were related statistically to watershed characteristic variables such as area, slope, length of main stream and the centroid length of the basin. 3. Average relative errors of the simulated peak discharge of calibrated runoff hydrographs by using linear time-variant and linear time-invariant models were shown to be 0.75 and 5.42 percent respectively to the peak of observed runoff hydrographs. Correlation coefficients for the statistical analysis in the same condition were shown to be 0.999 and 0.978 with a high significance respectively. Therefore, it can be concluded that the accuracy of a linear time-variant model is approaching more closely to the observed runoff hydrograph than that of a linear time-invariant model in the applied watersheds. 4. Average relative errors of the time to peak of calibrated runoff hydrographs by using linear time-variant and linear time-invariant models were shown to be 16.44 and 19.89 percent respectively to the time to peak of observed runoff hydrographs. Correlation coefficients in the same condition were also shown to be 0.999 and 0.886 with a high significance respectively. 5. It can be seen that the shape of simulated hydrograph based on a linear time- variant model is getting closer to the observed runoff hydrograph than that of a linear time-invariant model in the applied watersheds. 6. Two different models were verified with different rainfall-runoff events from data for the calibration by relative error and correlation analysis. Consequently, it can be generally concluded that verification results for the peak discharge and time to peak of simulated runoff hydrographs were in good agreement with those of calibrated runoff hydrographs.

• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.365-376
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• 2013

The purpose of this study was to evaluate effects of spatio-temporal changes in land uses and rainfall magnitude using the Soil and Water Assessment Tool (SWAT). Prior of application of the model to real-world problem, the model should be calibrated and validated properly. In most modeling approaches, the validation process is done assuming no significant changes occurring at the study watershed between calibration and validation periods, which is not proper assumption for agricultural watersheds. If simulated results obtained with calibrated parameters match observed data with higher accuracy for validation period, this does not always mean the simulated result represents rainfall-runoff, pollutant generation and transport mechanism for validation period because temporal and spatial variables and rainfall magnitude are often not the same. In this study SWAT was applied to Mandae study watershed in Korea to evaluate effects of spatio-temporal changes in landuses using 2009 and 2010 crop data for each field at the watershed. The Nash-Sutcliffe model efficiency (NSE) values for calibration and validation with either 2009 or 2010 was evaluated and the NSE value for calibration with 2009 and calibration with 2010 were compared. It was found that if there is substantial change in land use and rainfall, model calibration period should be determined to reflect those changes. Through these approaches, inherent limitation of the SWAT, which does not consider changes in land uses over the simulation period, was investigated. Also, Effects of changes in rainfall magnitude during calibration process were analyzed.

• Proceedings of the KSRS Conference
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• v.1
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• pp.239-242
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• 2006

Impervious surface is an important index for the estimation of urbanization and environmental change. In addition, impervious surface has an influence on the parameters of rainfall-runoff model during rainy season. The increase of impervious surface causes peak discharge increasing and fast concentration time in urban area. Accordingly, impervious surface estimation is an important factor of urban rainfall-runoff model development and calibration. In this study, impervious surface estimation is performed by using remote sensing images such as landsat-7 ETM+ and high resolution satellite image and regression tree algorithm based on case study area ? Jungnang-cheon basin in Korea.