• Journal of Korea Water Resources Association
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• v.48 no.5
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• pp.393-407
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• 2015

This study analyzed the characteristics of orographic effect using radar data for the Chungju dam basin. First, independent rainfall events were selected by applying the IETD (Interevent Time Definition) and rainfall threshold. Among those independent rainfall events, rather strong events were selected to decide the occurrence condition of orographic effect. Also, the average reflectivity was calculated for the entire period and for the period of storm center, and the change in reflectivity was analyzed by comparing the average reflectivity to that in the mountain area. Important rainfall factors were selected and applied to the logistic regression model to decide the occurrence condition of orographic effect. Summarizing the results is as follows. First, evaluation of the radar data along the passing line of a storm showed the increase of radar reflectivity in the mountain area. Second, the result of logistic regression analysis showed that the orographic effect in the Chungju Dam Basin mostly occurred when the rainfall intensity was higher than 4 mm/hr, the storm velocity was lower than 4 km/hr, and the approach angle was $90^{\circ}{\pm}5^{\circ}$.

• Journal of Korea Water Resources Association
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• v.47 no.9
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• pp.777-787
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• 2014

Stormwater pipe systems are most commonly used to discharge rainwater from the urban catchment covered by the impervious area. To design stormwater pipe and rainwater pumping station, frequency analysis is implemented using historical rainfall and the design rainfall is timely distributed using theoretical shape such as Huff distribution. This method cannot consider the rainfall intensity variation caused by climate change which is type of uncertainty. Therefore, in this study, runoff from Gasan1 stormwater pumping stations catchment is calculated using design rainfall distributed by the 2nd quartile distribution method and the historical rainfall events. From the analysis, the nodal flooding in the urban catchment is likely caused by the high peak rainfall event rather than the large amount of rainfall. The linear regression analysis is implemented. As a result, when several storms have the same amount of rainfall, the nodal flooding in the stormwater pipe systems could be caused by the high peak of storm events. Since as the storm duration become short, the peak rainfall become high, the nodal flooding likely become severe with the short storm duration. The uncertainty in the peak data of design rainfall is analyzed and this uncertainty has to be consider in the stormwater pipe design process.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.351-364
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• 2000

The effect of water quality improvement of combined sewage by detention pond has been studied. It is convinced that the pollutant load and peak flow through the combined sewer by first rainfall and runoff can be decreased by detention pond sited at the outlet of small basin. Hydraulic modeling of detention panel was performed for two cases of sedimentation pond and gravel contact pond. It has been recognized that it is more efficient to reduce the pollutant of combined sewage when the combined sewage is released alter a fixed detention time in the detention pond than it is released continuously without detention time. The gravel contact detention pond shows higher pollutant removal rate than the sedimentation detention pond in all pollutants. When it comes to gravel contact detention pond, the gravel pond filled with crushed gravel has a higher pollutant removal rate than that filled with river gravel.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.6
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• pp.43-50
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• 2020

The Doam Lake watershed is one of the non-point source management areas announced by the Ministry of Environment, and is a constant problem for the stream ecosystem dut to Storm water. In this study, a total of 48(rainfall) and 47(non-rainfall) sites were investigated for the entire watershed (Samyangcheon, Chahangcheon, Hoenggyecheon, Yongpyeongcheon, Songcheon, Lake Doam) on August 15, 2019 and on October 18, 2019 to estimate the source of turbid water in the Doam Lake watershed. Subsequently, water quality analysis was performed on Suspended Soild (SS), Turbidity, Total Phosphorus (TP), Total Nitrogen (TN), and Biochemical Oxygen Demands (BOD) and correlation among water quality parameters was analyzed based on the analyzed samples. As a result, most of the turbid water generated during rainfall was in highland fields. During rainfall, Hoengyecheon had the highest average SS concentration among all streams, and during non-rainfall, the average SS concentration was highest in Yongpyeongcheon, so the two stream were selected as vulnerable areas. However, since Yongpyeongcheon may be a temporary phenomenon due to river construction, additional continuous monitoring is required. Therefore, in the Doam Lake watershed, intensive management is required for vulnerable areas.

• Journal of Korean Society on Water Environment
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• v.21 no.3
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• pp.248-255
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• 2005

Since the water quality of drinking water sources has been recognized as a big issue, the ministry of Environment in Korea is designing the total maximum daily load (TMDL) program for 4 major large rivers. The TMDL program can be successfully performed as controling the nonpoint pollutants from watershed area near the river. Of the various landuses in nonpoint pollution, parking lots and bridges are stormwater intensive landuses because of high imperviousness and high pollutant mass emissions from vehicular activities. Vehicle emissions from those areas include different pollutants such as heavy metals, oil and grease and particulates from sources such as fuels, brake pad and tire wear, etc. Especially the pollutant washed-off from the landuses are directly affecting to the river water quality. Therefore this research was conducted to understand the magnitude and nature of the stormwater emissions with the goal of quantifying stormwater pollutant concentrations and mass emission rates of pollutants from parking lot and bridges in Korea. In Kongju city areas, two monitoring sites were equipped with an automatic rainfall gages and an automatic flow meter for accumulating the useful data such as rainfall, water quality and runoff flow. This manuscripts will show the concentration changes during storm duration and EMCs to characterize the concentration profiles in different land uses. Also the first flush criteria will be suggested using dynamic EMCs. The definition of dynamic EMC is a new approach explaining the relationship of EMC and first flush effect.

• Journal of the Korean Institute of Landscape Architecture
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• v.38 no.5
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• pp.80-92
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• 2010

The purpose of this study was to analyze drainage facilities in mountainous urban neigbborhood parks--Baebongsan Park and Ogeum Park--in Seoul. Based on an analysis of existing drainage facilities, the volume of storm water runoff (VSW), the runoff rate of open channels(ROC), and the detention capacity of open charmels(DCOC) by each drainage watershed, the coefficient of runoff rate(CROC) as evaluated to be relevant between VSW and ROC and the coefficient of the detention capacity of open channe1s(CDCOC) as evaluated with DCOC compared to VSW were estimated and analyzed by parks and by watersheds. The results are as follows: 1. The total drainage area of Baebongsan Park was 34.13ha including surface runoff area(15.05ha; 44.09%), open channel area(l4.60ha; 42.78%), and natural waterway area(4.48ha; 13.13%). The total drainage area of Ogeum Park was 20.39ha including open channel area (10.14ha; 49.73%), ridge-side gutter area(7.17ha; 35.16%), surface runoff area (2.52ha; 12.36%), and natural waterway area (0.56ha; 2.75%). In Baebongsan Park, the portion of surface runoff was comparatively higher while the portion of artificial drainage area was higber in Ogeum Park. 2. In Baebongsan Park drainage districts were largely divided: VSW was $7.28m^3/s$ in total(average $0.23m^3/s$). Comparatively, tbe VSW in Ogeum Park, including smaller drainage districts, was $4.37m^3/s$ in total(average $0.12m^3/s$). 3. The ROC of Baebmgsan Park was $11.58m^3/s$ in total(average $0.77m^3/s$) and the CROC was 5.26, while in Ogeum Park, the ROC was $15.40m^3/s$(average $0.34m^3/s$) and tbe CROC was 8.87 higher than that of Baebongsan Because the size and slope of the open channel in Baebongsan Park was higher, the average ROC was larger, while tbe CROC of Ogeum Park was higher than that of Baebongsan Park, for the VSW in Ogeum Park was comparatively lower. 4. The DCOC in Baebongsan Park was $554.54m^3$ and the average of CDCOC was 179.83. That of Ogeum Park was $717.74m^3$ and the average of the CDCOC was 339.69, meaning that the DCOC of Ogeum Park was so much higber that drainage facilities in Ogeum Park were built intensively. This study was focused m the capacity of the drainage facilities in mountainous urban neighborhood parks by using the CROC to evaluate relevance between VSW and ROC and the CDCOC to evaluate the DCOC as compared with VSW. The devised methodology and coefficient for evaluating drainage facilities in mountainous urban neighborhood parks may he universally applicable through additional study. Further study m sustainable urban drainage systems for retaining rainwater in a reservoir and for enhancing ecological value is required in the near future.

• Journal of Korean Society of Forest Science
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• v.81 no.4
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• pp.337-345
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• 1992

In this research, a kinematic wave model was applied for the runoff analysis, Regulation of streamflow was estimated by the calibration of roughness coefficient as a parameter. The data analyzed were obtained from Ananomiya and Shirasaka experimental basins at Tokyo University Forest in Aichi. Estimation methods and characteristics of roughness coefficient as a evaluation method of hydrological function of forest are summarized as follows ; 1. Roughness coefficient($N_s$) indicates the resistance of hillslope to the flowing water of surface runoff. There exists an hypothesis that resistance of hillslope to flowing water increase with the growth forest and development of the $A_o$ layer. 2. Roughness coefficient($N_s$) was estimated by the parameter when the stream direct runoff was calculated by using the kinematic wave. 3. Secular change of '$N_s$' in ananomiya has a curve which has an upper limit and increases exponentially near the limit. The curve quickly increased from 1935 to 1945 when results of afforestation for erosion control were thought to be effective. On the other hand, slight increase of '$N_s$' in Shirasaka indicates that there was not such a big change in the surface of soil layer. 4. The increase of '$N_s$' was related with decrease of direct runoff and increase of base flow. It was recognized that the rate of direct runoff decreased with the improvement of forest physiognomy and the rate of base flow was increased. But absolute value of water runoff per one storm decreased in chronological order.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.587-596
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• 2003

Application of a catchment modelling system requires recorded information to ascertain the reliability and robustness of the predicted flow conditions. Where this recorded information is not available, the necessary information for reliable and robust predictions must be obtained from other available information sources. The alternative approach presented in this paper used inference models for getting this necessary information that is required to calibrate and validate the catchment modelling system for both an ungauged and a gauged catchments. In this study, inference models were developed for determination of control parameters of the Storm Water Management Model (SWMM), mainly based on landuse component of the catchment, which is a major factor to impact on quantity and quality of catchment runoff. Results from the study show that the new approach for determination of the spatially variable control parameters produced more accurate estimates than a traditional approach. Also, the number of control parameters estimated can be reduced significantly as the proposed method only requires determination of control parameters associated with each land use of the catchment while a traditional approach needs to assign a number of control parameters for a number of subcatchment.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.2
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• pp.69-79
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• 2017

In this study, we developed real-time urban stream discharge forecasting model using short-term rainfall forecasts data simulated by a regional climate model (RCM). The National Centers for Environmental Prediction (NCEP) Climate Forecasting System (CFS) data was used as a boundary condition for the RCM, namely the Global/Regional Integrated Model System(GRIMs)-Regional Model Program (RMP). In addition, we make ensemble (ESB) forecast with different lead time from 1-day to 3-day and its accuracy was validated through temporal correlation coefficient (TCC). The simulated rainfall is compared to observed data, which are automatic weather stations (AWS) data and Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA 3B43; 3 hourly rainfall with $0.25^{\circ}{\times}0.25^{\circ}$ resolution) data over midland of Korea in July 26-29, 2011. Moreover, we evaluated urban rainfall-runoff relationship using Storm Water Management Model (SWMM). Several statistical measures (e.g., percent error of peak, precent error of volume, and time of peak) are used to validate the rainfall-runoff model's performance. The correlation coefficient (CC) and the Nash-Sutcliffe efficiency (NSE) are evaluated. The result shows that the high correlation was lead time (LT) 33-hour, LT 27-hour, and ESB forecasts, and the NSE shows positive values in LT 33-hour, and ESB forecasts. Through this study, it can be expected to utilizing the real-time urban flood alert using short-term weather forecast.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.3
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• pp.68-80
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• 2013

The purpose of this study is to evaluate the applicability of UK design flood estimation model, FEH-ReFH through rainfall-runoff simulation of Korean watershed. For the Nam stream watershed($165.12km^2$), the model was calibrated using 6 storm events. The watershed and hydrological characteristics for the model requirements was prepared by developing input data pre-processors based on open GIS. The parameters of rainfall loss rate and unit hydrograph were calibrated from the observed data. The results can be used for improving and standardizing the Korean design flood estimation method.