• Journal of Environmental Impact Assessment
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• v.14 no.2
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• pp.63-73
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• 2005

This study was performed to characterize stormwater runoff of pollution material from nonpoint sources during rainfall in drainage basins of Hongjechun watershed, and to suggest management methods to control the first flush of nonpoint sources. We conducted 4 times of field surveys including 3 times of wet period and 1 times of dry period for 5 stations, which consist of 3 stations in main stream of Hongjechun and 1 station in tributaries of Sinyoungchun and Gukichun, respectively. The variation of pollutant concentrations in terms of BOD, COD, SS and TP was large depending on the flow rate of stormwater, while a little change of TN concentration was investigated. Depending on the rainfall event, the difference of flowrates, and runoff loadings was large, while the difference of those for dry wether period was not noticeable for various sub-basins. In the results of unit load calculation, the range of 153-277 kg/ha/yr for BOD, 222-422 kg/ha/yr for COD, 264-432 kg/ha/yr for SS, 40-70kg/ha/yr for TN, and 13-25 kg/ha/yr for TP was obtained for Hongjechun, Sinyoungchun, and Gukichun sub-basins. Compared with the previous studies, the result of this study was founded to be acceptable.

• Korean Journal of Remote Sensing
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• v.22 no.5
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• pp.407-413
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• 2006

To investigate the streamflow impact of land cover changes by a typhoon, HEC-l storm runoff model was applied by using land cover information before and after the typhoon. The model was calibrated with three storm events of 1985 to 1988 based on 1985 land cover condition for a $192.7km^{2}$ watershed in northeast coast of South Korea. After the model was tested, it was run to estimate impacts of land cover change by the typhoon RUSA occurred in 2002 (31 August-1 September) with 897.5 mm rainfall. The land covers before and after the typhoon were prepared using Landsat 7 ETM+ of September 11 of 2000 and Landsat 5 TM of September 29 of 2002 respectively. For the $6.9km^{2}$ damaged area (3.6 % of the watershed), the peak runoff and total runoff by the changed land cover condition increased 12.5 % and 12.7 % for 50 years rainfall frequency and 1.4 % and 1.8 % for 500 years rainfall frequency respectively based on AMC (Antecedent Moisture Condition)-I condition.

• Journal of Environmental Impact Assessment
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• v.3 no.2
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• pp.57-67
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• 1994

The National Park should be preserved as described in the regulation. However, the development has resulted in degrading the environment in the park. Especially, the collective facility area has been developed for the commercial benefit rather than for the preservation. So, it is necessary to figure out the impact of the development plan proposed. Thus, the purpose of this study is to explore the hydrologic effects due to the collective facility area development in the National Park. The study site is the second collective facility area of Mt. Kyeryong National Park. The analysis of hydrologic effects due to the development has been carried out using the GIS in this study. The Rational Method and Soil Conservation Service(SCS) were used to estimate the runoff volume. During this procedure, GIS software, ARC/INFO was used to integrate, manipulate, and calculate the attribute value of a number of ploygons which represen each land use characteristic. A program was written to compute the attribute value of each polygon and to estimate the difference of peaktime runoff volume before and after development.

• Journal of Korea Water Resources Association
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• v.44 no.8
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• pp.683-694
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• 2011

To analyze the regional impact of air temperature increase and precipitation variation on water resources, the variability of precipitation-effectiveness (P-E) ratio which is estimated using precipitation and air temperature data of 59 weather stations operated by the Korean Meteorological Administration (KMA) during 1973~2009 was analyzed. Also runoff data resulting from the Precipitation-Runoff Modelling System (PRMS) modelling were analyzed during 1966~2007. The overall spatio-temporal variability of P-E ratio and runoff data in South Korea is corresponding to the variability of precipitation amount. However some region shows that the P-E ratio decreases even though the trend of precipitation amount increases which may be caused by the air temperature increase. Runoff trend is similar to that of P-E ratio. Precipitation and P-E ratio have decreased all seasons except summer season and it means the reduction of available water resources during those seasons. These variability should be reflected in the spring, fall, and winter water supply strategy.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.6
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• pp.65-71
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• 2018

The Long-Term Hydrologic Impact Assessment (L-THIA) model is a quick and straightforward analysis tool to estimate direct runoff and nonpoint source pollution. L-THIA was originally implemented as a spreadsheet application. GIS-based versions of L-THIA have been developed in ArcView 3 and upgraded to ArcGIS 9. However, a major upgrade was required for L-THIA to operate in the current version of ArcGIS and to provide more options in runoff and NPS estimation. An updated L-THIA interfaced with ArcGIS 10.0 and 10.1 has been developed in the study as an ArcGIS Desktop Tool. The model provides a user-friendly interface, easy access to the model parameters, and an automated watershed delineation process. The model allows use of precipitation data from multiple gauge locations for the watershed when a watershed is large enough to have more than one precipitation gauge station. The model estimated annual direct runoff well for our study area compared to separated direct runoff in the calibration and validation periods of ten and nine years. The ArcL-THIA, with a user-friendly interface and enhanced functions, is expected to be a decision support model requiring less effort for GIS processes or to be a useful educational hydrology model.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.886-895
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• 2009

The guideline of selection of Integrated Management Practices (IMPs), such as wood, green roof, lawn, and porous pavement, for Low Impact Development (LID) design was proposed by ranking the reduction rate of surface runoff using LIDMOD1.0. Based on the guideline, LID was designed with several scenarios at two apartment complexes located at Songpa-gu, Seoul, Korea, and the effect of LID on surface runoff was evaluated during last 10 years. The effect of runoff reduction of IMP by land use change was highly dependent on the kind of hydrologic soil group. The wood planting is the best IMPs for reduction of surfac runoff for all hydrologic soil groups. Lawn planting is an excellent IMP for hydrologic soil group A, but reduction rate is low where soil doesn't effectively drains precipitation. The green roof shows constant reduction rate of surface runoff because it is not influenced by hydrologic soil group. Compared to the rate of other IMPs, the green roof is less effect the surface runoff reduction for hydrologic soil group A and is more effect for hydrologic soil group C and D followed to planing wood. The porous pavement for the impervious area is IMPs which is last selected for LID design because of the lowest reduction rate for all hydrologic soil group. As a result of LID application at study areas, we could conclude that the first step of the strategy of LID design at apartment complex is precuring pervious land as many area as possible, second step is selecting the kind of plant as more interception and evapotranspiration as possible, last step is replacing impervious land with porous pavement.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.61-70
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• 2010

The increase of impervious cover (IC) in a watershed is known as an important factor causing alteration of water cycle, deterioration of water quality and biological communities of urban streams. The study objective was to assess the impact of IC changes on the surface runoff characteristics of Kap Stream basin located in Geum river basin (Korea) using the Storm Water Management Model (SWMM). SWMM was calibrated and verified using the flow data observed at outlet of the watershed with 8 days interval in 2007 and 2008. According to the analysis of Landsat satellite imagery data every 5 years from 1975 to 2000, the IC of the watershed has linearly increased from 4.9% to 10.5% during last 25 years. The validated model was applied to simulate the runoff flow rates from the watershed with different IC rates every five years using the climate forcing data of 2007 and 2008. The simulation results indicated that the increase of IC area in the watershed has resulted in the increase of peak runoff and reduction of travel time during flood events. The flood flow ($Q_{95}$) and normal flow ($Q_{180}$) rates of Kap Stream increased with the IC rate. However, the low flow ($Q_{275}$) and drought flow ($Q_{355}$) rates showed no significant difference. Thus the subsurface flow simulation algorithm of the model needs to be revisited for better assessment of the impact of impervious cover on the long-term runoff process.

• Journal of Environmental Impact Assessment
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• v.20 no.4
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• pp.509-521
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• 2011

The purpose of this study is to estimate overall reliability and applicability of the watershed modeling for systematic management of point and non-point sources via water quality analysis and prediction of runoff discharge within watershed. Recently, runoff characteristics and pollutant characteristics have been changing in watershed by anomaly climate and urbanization. In this study, the effects of watershed scale were analyzed in runoff and water quality modeling using HSPF. In case of correlation coefficient, its range was from 0.936 to 0.984 in case A(divided - 2 small watersheds). On the other hand, its range was form 0.840 to 0.899 in case B(united - 1 watershed). In case of Nash-Sutcliffe coefficient, its range was from 0.718 to 0.966 in case A. On the other hand, its range was from 0.441 to 0.683 in case B. As a result, it was judged that case A was more accurate than case B. Therefore, runoff and water quality modeling in minimum watershed scale that was provided data for calibration and verification was judged to be favorable in accuracy. If optimal watershed dividing and parameter optimization using PEST in HSPF with more reliable measured data are carried out, more accurate runoff and water quality modeling will be performed.

• Journal of Korea Water Resources Association
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• v.47 no.6
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• pp.513-522
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• 2014

Climate change and urbanization have affected a increase of peak discharge and water pollution etc. In a view of these aspects, the LID(Low Impact Development) technology has been highlighted as one of adjustable control measures to mimic predevelopment hydrologic condition. Many LID technologies have developed, but there is a lack of studies with verification of LID technology efficiency. Therefore this study developed a rainfall-runoff simulator could be possible to verify LID technology efficiency. Using this simulator, this study has experimented the rainfall verification through the rainfall distribution experiment and the experiment to show the relation between inflow and effective rainfall in order to sprinkle the equal rainfall in each unit bed. As a result, the study defined the relation between allowable discharge range and RPM by nozzle types and verified the hydrologic cycle such as the relation between infiltration rate, surface runoff and subsurface runoff at pervious area and impervious area through the rainfall-runoff experiment.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.130-130
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• 2021

The increasing effect of urbanization has been more apparent through flooding and downstream water quality especially from heavy rainfalls. In response, stormwater runoff management solutions have focused on runoff volume reduction and treatment through infiltration. However, there are areas with low infiltration soils or are experiencing more dry days and even drought. In this study, a lab-scale infiltration system was used to compare the applicability of two types of soil as base layer in gravel-filled infiltration systems with emphasis on runoff capture and suspended solids removal. The two types of soils used were sandy soil representing a high infiltration system and clayey soil representing a low infiltration system. Findings showed that infiltration rates increased with the water depth above the gravel-soil interface indicating that the available depth for water storage affects this parameter. Runoff capture in the high infiltration system is more affected by rainfall depth and inflow rates as compared to that in the low infiltration system. Based on runoff capture and pollutant removal analysis, a media depth of at least 0.4 m for high infiltration systems and 1 m for low infiltration systems is required to capture and treat a 10-mm rainfall in Korea. A maximum infiltration rate of 200 mm/h was also found to be ideal to provide enough retention time for pollutant removal. Moreover, it was revealed that low infiltration systems are more susceptible to horizontal flows and that the length of the structure may be more critical that the depth in this condition.