• Journal of Environmental Impact Assessment
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• v.10 no.3
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• pp.223-234
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• 2001

In this study, we conducted a survey to examine the runoff characteristics of nonpoint sources, which wash off pollutants from the surface of basin during rainfall and affect water pollution of streams. An Anyangchun basin in the region Ewiwang City was selected as a study site. The basin divided into several subbasins such as Wanggokchun, Ojeonchun, and Anyangchun based on the tributaries, which confluence to the main stream of Anyangchun. Four times of field examination had been carried out between July and August of 2000, and water quality data collected from the surveys had been analysed. The survey includes in-situ flow, DO and PH measurements in the outlet of catchment. Laboratory analysis includes BOD, TN, TP. From the result, pollutant by runoff of nonpoint sources were washed out along with stormwater in the beginning of rainfall, and flowed into streams resulted in stream pollution. In case of BOD, the load from Ojeonchun catchment, most of which included urban areas, took up 50% of the total load from the entire watershed. Thus, by the results, it is clear that runoff load by urban nonpoint sources plays an important role in the control and management of nonpoint sources for the watershed.

• Korean Journal of Hydrosciences
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• v.7
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• pp.21-35
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• 1996

This Study is to develop the suitable hydrologic models for determination of the size and location of detention storage facilities to restrain stormwater runoff in urban areas. Hypothetical areas of two levels are considered to seize the hydrologic response characteristics. A one-square-kilometer ares is selected for the catchment level, and a 10-square-kilometer area consisting of 10 catchments is adapted at the watershed level as representative of urban drainage area. In this analysis, different rainfall freqyencies, land uses, drainage patte군, basin shates and detention storage policies are considered. Folw reduction effect of detention storage facilities is deduced from storage ratio and detention basin factor. A substantial saving in detention storage volumes is achieved 노두 the detention storage is planned at the watershed level rather than the catchment level. For the application of real watersheds, two watersheds in Seoul metropolitan area-Jamshil 2 and Seongnae 1-are selected on the basis of hydrologic response charactaristics. Through the regression analysis between dimensionless deterntion storage volume, dimensionless upstream area ratio and reduction rate of storage ratio, the regression equations to determine the size and location of detention storage faclities are presented.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.9-18
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• 2011

In this study the optimal volume for non-point source control retention is estimated considering spatio-temporal variation of land surface. The 3-parameter mixed exponential probability density function is used to represent the statistical properties of rainfall events, and NRCS-CN method is applied as rainfall-runoff transformation. The catchment drainage area is divided into individual $30m{\times}30m$ cells, and runoff curve number is estimated at each cell. Using the derived probability density function theory, the stormwater probability density function at each cell is derived from the rainfall probability density function and NRCS-CN rainfall-runoff transformation. Considering the antecedent soil moisture condition at each cell and the spatial variation of CN value at the whole catchment drainage area, the ensemble stormwater capture curve is established to estimate the optimal volume for an non-point source control retention. The comparison between spatio-temporally varied land surface and constant land surface is presented as a case study for a urban drainage area.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.2
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• pp.126-135
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• 2015

Increase of delivery effect of pollutant loads and surface runoff due to urbanization of catchment area results in serious environmental problems in receiving urban streams. This study aims to develop integrated stormwater management system to assist efficient urban stream flow and water quality control using information from the Storm Water Management Model (SWMM), real time water level and quality monitoring system and remote or automatic treatment facility control system. Based on field observations in the study site, most of the pollutant loads are flushed within 4 hours of the rainfall event. SWMM simulation results indicates that the treatment system can store up to 6 mm of cumulative rainfall in the study catchment area, and this means any type of normal rainfall situation can be treated using the system. Relationship between rainfall amount and fill time were developed for various rainfall duration for operation of stormwater treatment system in this study. This study can further provide inputs of river water quality model and thus can effectively assist integrated water resources management in urban catchment and streams.

• International Journal of High-Rise Buildings
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• v.7 no.2
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• pp.95-109
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• 2018

Since the concept was first introduced in the 1970s, transit-oriented-development (TOD) has greatly expanded in East Asian cities such as Hong Kong. Rail stations are built together with clusters of residential-commercial towers and government services to form a new style of living - a "rail village." This paper examines the composition, scale, spatial form, organization and operation of several typical rail villages in Hong Kong. The cases range across those planned from the mid-1990s to 2015. Based on the analysis of the rail village composition, the paper derives a development ratio to indicate the density, effectiveness and efficiency of a rail village catchment area. The ratio provides a useful and direct figure for the comparison of different stations, cities and development modes.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.349-357
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• 2006

Nowadays, the discharges of urban streams during dry season are depleted because the hydrologic cycle in the watershed has been destroyed due to the expansion of the impermeable area, the excessive groundwater pumping, climate change, and so forth. The streamflow depletion may bring out severe water quality problems. This research are to investigate the hydrologic characteristics and to develop a technology to restore sound hydrologic cycle of Anyangcheon watershed. For the hydrological cycle analysis of the Anyangcheon watershed, continuous simulations of urban runoff were performed for the upstream basin of Gocheok bridge whose basin area covered 4/5 of the whole catchment area. The increase of impervious area by urbanization was analysed and its effect on urban runoff was evaluated. The SWMM 5 (Storm Water Management Model 5) was used for the continuous simulation of urban runoff. The analysis results of urbanization effect on runoff are as follows: the surface runoff in 2000 increases to 65% of the whole precipitation whereas the surface runoff in 1975 amounts to 50% of the precipitation; the groundwater runoff in 2000 amounts to 7% and shows 6% decrease during the period from 1975 to 2000.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1209-1212
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• 2007

Urban flooding with surcharges in sewer system was investigated because of unexpected torrential storm events these days, causing significant amounts of human and economic damages. Although there are limitations in forecasting and preventing natural disasters, integrated urban flooding management system using the SWMM(Storm Water Management Model) engine and Web technology will be an effective tool in securing safety in operating rubber-tired transportation system. In this study, the study area, located in Chuncheon, Kangwon province, was selected to evaluate the applicability of the SWMM model in forecasting urban flooding due to surcharges in sewer system The catchment are 21.10 ha in size and the average slope is 2% in lower flat areas. Information of subcatchment, conjunctions, and conduits was used as the SWMM interface to model surface runoff generation, water distribution through the sewer system and amount of water overflow. Through this study, the applicability of the SWMM for urban flooding forecasting was investigated and probability distribution of storm events module was developed to facilitate urban flooding prediction with forecasted rainfall amounts. In addition, this result can be used to the establishment of disaster management system for rainfall safety of rubber-tired tram in the future.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.123-123
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• 2020

The present study is aimed to correcting radar-based mean areal precipitation forecasts to improve urban flood predictions and uncertainty analysis of water levels contributed at each stage in the process. For this reason, a long short-term memory (LSTM) network is used to reproduce three-hour mean areal precipitation (MAP) forecasts from the quantitative precipitation forecasts (QPFs) of the McGill Algorithm for Precipitation nowcasting by Lagrangian Extrapolation (MAPLE). The Gangnam urban catchment located in Seoul, South Korea, was selected as a case study for the purpose. A database was established based on 24 heavy rainfall events, 22 grid points from the MAPLE system and the observed MAP values estimated from five ground rain gauges of KMA Automatic Weather System. The corrected MAP forecasts were input into the developed coupled 1D/2D model to predict water levels and relevant inundation areas. The results indicate the viability of the proposed framework for generating three-hour MAP forecasts and urban flooding predictions. For the analysis uncertainty contributions of the source related to the process, the Bayesian Markov Chain Monte Carlo (MCMC) using delayed rejection and adaptive metropolis algorithm is applied. For this purpose, the uncertainty contributions of the stages such as QPE input, QPF MAP source LSTM-corrected source, and MAP input and the coupled model is discussed.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.122-122
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• 2020

Urban flood simulation plays a vital role in national flood early warning, prevention and mitigation. In recent studies on 2-dimensional flood modeling, the integrated run-off inundation model is gaining grounds due to its ability to perform in greater computational efficiency. The adaptive quadtree shallow water numerical technique used in this model implements the adaptive mesh refinement (AMR) in this simulation, a procedure in which the grid resolution is refined automatically following the flood flow. The method discounts the necessity to create a whole domain mesh over a complex catchment area, which is one of the most time-consuming steps in flood simulation. This research applies the dynamic grid refinement method in simulating the recent extreme flood events in Metro Manila, Philippines. The rainfall events utilized were during Typhoon Ketsana 2009, and Southwest monsoon surges in 2012 and 2013. In order to much more visualize the urban flooding that incorporates the flow within buildings and high-elevation areas, Digital Surface Model (DSM) resolution of 5m was used in representing the ground elevation. Results were calibrated through the flood point validation data and compared to the present flood hazard maps used for policy making by the national government agency. The accuracy and efficiency of the method provides a strong front in making it commendable to use for early warning and flood inundation analysis for future similar flood events.

• Health Policy and Management
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• v.18 no.4
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• pp.66-84
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• 2008

Objectives: This study aimed to. offer some fundamental evidences for the stroke management policy by investigating the trends of medical care utilization and regionalization in stroke inpatients. Methods: We used the National Health Insurance claims and registry data for stroke inpatients from 1998 to 2005. Among all stroke inpatient claims data, self-employed insured and their dependents were only included in this study. The classification of stroke was based on ICD-10(I60-I69) and its subtype was divided by hemorrhage(I60-I62) and infarction(I63-I64) type. To evaluate regionalization of medical care utilization, relevance index was calculated by regions. The regions were classified 8 large catchment areas and 163 self authorized areas. Results: The overall medical care utilization rate of stroke inpatient has been increased, especially infarction subtype. Among medical care institutions, the utilization of hospital has been the most rapidly increased. Although considered annual rate of interest, total medical cost of stroke inpatients has been increased, Totally, more than 84% of stroke inpatient were admitted to medical care institutions in their own large catchment area during 1998-2005. The relevance indices in their own large catchment area (self sufficiency rates) were more than 70% in most areas regardless of stroke subtype except Chungbuk catchment area. Self sufficiency rates of stroke inpatients among 163 self authorized areas in 1998 and 2005 were 84.2% and 83.1% in metropolitan, 46.7% and 45.5% in urban, and 19.5% and 22.6% in rural areas, respectively. Conclusion: Stroke management policy for improvement of distribution at the district level, especially in rural areas, may be helpful for reducing regional inequality in stroke.