• Journal of Environmental Impact Assessment
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• v.24 no.2
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• pp.163-174
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• 2015

Urbanization caused various environmental problems like destruction of natural water cycle and increased urban flood. To solve these problems, LID(Low Impact Development) deserves attention. The main objective of LID is to restore the water circulation to the state before the development. In the previous studies about the LID, the runoff reduction effect is mainly discussed and the effects of each techniques of LID depending on rainfall types have not fully investigated. The objective of this research is to evaluate the effect of LID using the quantitative simulation of rainwater runoff as well as an amount of infiltration according to the rainfall and LID techniques. To evaluate the water circulation of LID on the development area, new land development areas of Hanam in South Korea is decided as the study site. In this research, hydrological model named STORM is used for the simulation of water balance associated with LID. Rainfall types are separated into two categories based on the rainfall intensity. And simulated LID techniques are green roof, permeable pavement and swale. Results of this research indicate that LID is effective on improvement of water balance in case of the low intensity rainfall event rather than the extreme event. The most effective LID technique is permeable pavement in case of the low intensity rainfall event and swale is effective in case of the high intensity rainfall event. The results of this study could be used as a reference when the spatial plan is made considering the water circulation.

• Journal of Wetlands Research
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• v.10 no.2
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• pp.105-114
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• 2008

Growth in population and urbanization has progressively increased the loadings of pollutants from non-point sources as well as point sources. Separated sewer overflows(SSO) have been considered as a major cause of water-quality deterioration of natural water-courses in the vicinity of the heavily urbanized areas. The factors defining the magnitude and occurrence of SSO are site-specific. It is important to know exact properties of pollutants contained in SSO to address water quality impacts that are caused by SSO inputs to the receiving waters. Site and event parameters found to have significant influences on urban runoff pollutant EMCs include total event rainfall, antecedent dry period, rainfall intensity. In this study, a field survey was carried out in some selected areas of Cheongju city. Literature from previous similar studies was consulted and some important factors affecting the runoff characteristics of urban drainage areas were analyzed for some selected survey points. It was found that the factors most affecting BOD are the number of dry days prior to rainfall and the intensity of the rainfall. The factor most affecting CODcr is the number of dry days prior to rainfall. The factors most affecting SS are the amount of rainfall and the number of dry days prior to rainfall. The factor most affecting TN is the amount of rainfall. The factor most affecting TP is the amount of rainfall and the number of dry days prior to rainfall.

• Journal of Environmental Science International
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• v.16 no.7
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• pp.805-811
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• 2007

The purpose of this study was to invesitigate relationship between rainfall water quality and precipitation characteristic during the accumulated rainfall and rainless period. As the results of the analysis, rainfall water quality was improved in the rainfall duration. Correlation coefficients between rainwater quality and accumulated rainfall were $0.88{\sim}0.99$ except $Cl^-$. and that between rainless period and initial rainfall water quality were $0.62{\sim}0.75$. During the Asian dust event, concentration of the turbidity, BOD and electric conductivity were high. Therefore, it shows that the rainfall water quality is effected by atmospheric conditions before the rainfall events.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.4
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• pp.9-17
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• 2012

This study was aimed to characterize non-point source (NPS) pollutant runoff and estimate event mean concentrations (EMCs) from a small rural watershed located at the headwater area of the Gyeongan stream. The study watershed consists of the two major landuse, forest (72 %) and paddy field (28 %). The nine rainfall events ranging from 18.5 to 192.6 mm in amount were monitored in this study. Stream flow was measured at the watershed outlet using a water level gauge, while a number of water samples for each event were collected and analysed for water quality. Event pollutant loads varied greatly depending on rainfall events varying from 22.6 to 3,134.2 mg/L, 0.32 to 24.56 mg/L, 0.090 to 1.320 mg/L, and 2.3 to 149.8 mg/L for SS, TN, TP, and COD, correspondently. The respective mean EMCs were estimated by 104.2, 1.00, 0.168, and 7.9 mg/L. The Pearson correlation analysis showed that COD EMC was significantly correlated with those of SS, TN, and TP. Rainfall runoff ratio appeared to be negatively correlated with EMCs of SS, TP, and COD, although not statistically significant. The event loads from the largest rainfall was greater than the sum of those from the remaining eight events. The study results suggest that the appropriate management of intensified storm events are of greater importance in curbing NPS loads, while the estimated EMCs provide base data for the unit pollutant loads determination for the forest-paddy composite upstream watershed.

• Journal of Korean Society on Water Environment
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• v.37 no.2
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• pp.103-113
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• 2021

In this study, an Excel-based model (ROADMOD) was developed to estimate pollutant loading from the road and evaluate BMPs. ROADMOD employs the Chezy-Manning equation and empirical expression for estimating surface runoff, and power function for pollutant buildup, and exponential function for pollutant washoff in SWMM. The results of model calibration for buildup and washoff using observed data revealed a good match between the simulation results and the observed data. The long-term surface runoff and sediment simulated by ROADMOD demonstrated a good match with those by SWMM with 2 ~ 14% of relative error. The shorter sweeping interval (within 8 days) remarkably decreased sediment loads from the road. It was found that the effect of reducing sediment loads from the road was greatly affected not only by the sweeping interval but also by sweeping on the day before a rainfall event. The 48% of removal efficiency of sediment loads from the road was achieved with 26 times of road sweeping per year when sweeping was performed on the day before the rainfall event. A 4-day sweeping interval showed similar removal efficiency (48%) with 96 times of sweeping per year. It is considered that the road sweeping on the day before a rainfall event could maximize the effect of reducing the non-point source pollution from the road with minimization of the number of road sweeping. So, the road sweeping on the day before a rainfall event can be considered as one of the useful and best management practices (BMPs) on road.

• Journal of the Korean earth science society
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• v.33 no.7
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• pp.596-607
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• 2012

The R-Z relationship is one of important error factors to determine the accuracy of radar rainfall estimation. In this study, we have explored the effect of the R-Z relationships derived from disdrometer data in estimating the radar rainfall. The heavy rain event that produced flooding in St-Remi, Quebec, Canada has been occurred. We have tried to investigate the severity of rain for this event using high temporal (2.5 min) and spatial resolution ($1^{\circ}$ by 250 m) radar data obtained from the McGill S-band radar. Radar data revealed that the heavy rain cells pass directly over St-Remi while the coarse raingauge network was not sufficient to detect this rain event. The maximum 30 min (1 h) accumulation reaches about 39 (42) mm in St-Remi. During the rain event, the two disdrometers (POSS; Precipitation Occurrence Sensor System) were available: One used for the reflectivity calibration by comparing disdrometer Z and radar Z and the other for deriving disdrometric R-Z relationships. The result shows the significant improvement with the disdrometric reflectivity-dependent R-Z relationships against the climatological R-Z relationship. The bias in radar rain estimation is reduced from +12% to -2% and the root-mean squared error from 16 to 10% for daily accumulation. Using the estimated radar rainfall rate with disdrometric R-Z relationships, the flood event was well captured with proper timing and amount.

• Journal of Korean Society on Water Environment
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• v.22 no.4
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• pp.666-671
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• 2006

Effects of a rainfall event (July 28, 2005) on the hydrochemical characteristics of the Jungrang river, the biggest tributary of the Han river, was investigated. Significant spatial variations in the hydrochemical characteristics were observed. At JR2 location, concentrations of T-N and T-P were relatively low indicating occurrence of active oxidation in the stepped drop structure. At JR3 location, concentrations of Na, K, Cl, $NH_4-N$ and EC were elevated suggesting increased discharge from the nearby waste-water treatment plant and tributaries. The rain event diluted major dissolved ion concentrations in the river by 12~52%. The $NO_3-N$ levels were preserved during the rain then increased about twofold after rainfall, suggesting increased discharge of nitrate-contaminated groundwater. Heavy metals including Cd, Co, Cr, Cu and Pb were not detected in all water samples and the leachates from surface sediment samples. Concentrations of Fe, Mn, Al and Zn were below the Korean Drinking Water Guideline. Results of this study suggested that establishment of water-quality monitoring protocols describing temporal and spatial variations in parameters sensitive to rainfall events, relatively steady factors, and contaminant sources is required.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.572-579
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• 2011

We have examined the runoff characteristics of nonpoint source (NPS) in fields. Two monitoring sites were equipped with an automatic velocity meter and water sampler. Monitoring was conducted at fields 1 and field 2 during the rainfall event. Ten rainfall-runoff events were monitored and analyzed during the study period. The results show that runoff occurred if daily rainfall and intensity were higher than 40 mm and 1.6 mm/hr except a few extreme rainfall events with very high intensity. Runoff of field 1 was approximately twice of that of field 2. Event mean concentrations (EMC) and pollution load of analyzed water quality indices were also higher in field 2 than in field 1. Especially, TN load from field 2 was $75.4 mg/m^2$ and was about 5 times higher than that from field 1. Analysis of Pearson correlation coefficient of water quality parameter indicates that besides of TN all items in fields 1 have tight relationship respectively (p < 0.01). But those of fields 2 have a significant (p < 0.05). Estimating units loading of NPS, we suggested that variable such as soil texture, rainfall amount and intensity and slope were needed to be considered from agricultural landuses. The results of this study can be used as a basic data in the development and implementation of total maximum daily loads (TMDL) in Korea.

• Journal of Environmental Science International
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• v.20 no.3
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• pp.417-426
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• 2011

This study was conducted to investigate runoff characteristics of non-point pollutants source at the urban and rural zones in sangju area. The monitoring was conducted with seven events for ten months and Event mean Concentration(EMC) and First Flush Effect(FFE) of SS and BOD were calculated on the result of the water quality parameters. During rainfall event, the peak concentrations of SS and BOD were observed after 3~4 hours of rainfall in rural areas. Whereas, the peak concentrations occurred within 1~2 hours after rainfall and then the highest concentration of NPS pollutants sharply decreased, showing strong first flush effect in urban areas. The cumulative load curves for NPS pollutants showed above the $45^{\circ}$ straight line, indicating that fist flush effect occurred in urban areas. The mean SS EMC values of rural areas ranged from 0.9~3.3mg/L, it was higher value when compare to urban areas. While the mean BOD values of urban areas were shown the highest values.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.2 no.1
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• pp.29-36
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• 1998

An instantaneous unit sediment graph (IUSG) model is investigated for prediction of sediment yield from an upland watershed in Northwestern Mississippi. Sediment yields are predicted by convolving source runoff with an IUSG. The IUSG is the distribution of sediment from an instantaneous burst of rainfall producing one unit of runoff. The IUSG, defined as a product of the sediment concentration distribution (SCD) and the instantaneous unit hydrograph (IUH), is known to depend on the characteristics of the effective rainfall. The IUH is derived by the Nash model for each event. The SCD is assumed to be an exponential function for each event and its parameters were correlated with the effective rainfall characteristics. A sediment routing function, based on travel time and sediment particle size, is used to predict the SCD.