• 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.

• Water for future
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• v.27 no.4
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• pp.85-94
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• 1994

A Sensitivity analysis on the model parameters involved in the Clark watershed routing method is made to demonstrate the effect of each parameter on the magnitude of 50-year design flood for small urban streams. As for the rainfall parameter the time distribution pattern of design storm was selected. For short duration storms Huff, Yen & Chow and Japanese Central type distributions were selected and the Mononobe distribution of 24-hour design storm was also selected and tested for Clark method application. The effect of SCS runoff curve number for effective rainfall and the methods of subbasin division for time-area curve were also tested. The routing parameter, i.e. the storage constant(K), was found to be the dominating parameter once design storm is selected. A multiple regression formula for K correlated with the drainage area and main channel slope of the basin is proposed for the use in urban stream practice for the determination of design flood by Clark method.

• Journal of Korea Multimedia Society
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• v.12 no.7
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• pp.989-996
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• 2009

Recently, use of the GIS (Geographic Information System) for the disaster of the urban inundation is increasing. The digital disaster map is the system which analyzes the occurrence area of inundation in the past and forecasts the flood areas by the hydrology method. The development of the system which simulates the flood forecast area by the SWMM(Storm Water Management System) and hydrology method and displays the danger areas is required for the construction of the inundation forecast system. And the spatial database which contains information of the urban facilities such as the street and building and the sewer system such as the manhole and drainage and the result of the hydrology analysis is constructed. In this paper, we propose the method for transforming the Shape File in ESRI into the Oracle spatial database to construct the spatial data for the drainage systems and urban facilities using the Shape File format in the ESRI. We suggest the algorithm for the transformation of the data format, and develop the prototype system to display the inundation area using the spatial database.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.5
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• pp.53-58
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• 2008

This study presented a design model optimizing a distance of inlet with drainage pipe laid under the gutter in road. When the distance of inlet changed, a basin for the gutter divided by the distance of inlet and the inflow coming into the gutter would be changed. In this case, the change of inlet distance causes the change of a diameter of drainage pipe and slope because of the change of capacity. Therefore, the optimization is needed to design the combination of them for the distance of inlet. Genetic Algorithm is used to determine the optimal combination of them. The conditions of road and the precipitation were assumed like a real and the range of inlet distance adopted $10{\sim}30\;m$ which has been introduced in domestic. This model presented the optimal distance of inlet and the combination of pipe and slope through the minimum cost. The result of the study is that the optimal distance of inlet is different from each slope of road and it can reduce about 20% of total cost for the distance of inlet.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1173-1185
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• 2008

The design methods of the road surface drainage facilities were compared for the improvement of design method. We have developed four computational design models classified by the methods to determine the duration of design rainfall and to analyze the flow of a linear drainage channel. The critical duration was determined by assuming the critical duration to be 10 minutes or by finding the duration of design storm being similar to the travel time of flow by trial and error. The flow of a linear drainage channel was analyzed as the uniform flow or the varied flow. The design models were applied to the artificial road surface drainage facilities with various channel slopes and road shoulder slopes. If the rainfall intensity of the 10 minutes duration was applied, the outlet spacing obtained from the design based on the varied flow analysis was larger than the uniform flow analysis only when the channel slope and the road shoulder slope was small. On the other hands, if the duration of design rainfall was determined by calculating the travel time, the varied flow analysis brought about larger outlet spacing than the uniform analysis for all conditions. However, the model of the critical duration concept and the varied flow analysis resulted in smaller outlet spacing than the current design method employing the rainfall of 10 minutes duration and the uniform flow analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1802-1806
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• 2006

It is important to consider the effects of land-use changes on surface runoff, stream flow, and groundwater recharge. Expansion of urban areas significantly impacts the environment in terms of ground water recharge, water pollution, and storm water drainage. Increase of impervious area due to urbanization leads to an increase in surface runoff volume, contributes to downstream flooding and a net loss in groundwater recharge. Assessment of the hydrologic impacts or urban land-use change traditionally includes models that evaluate how land use change alters peak runoff rates, and these results are then used in the design of drainage systems. Such methods however do not address the long-term hydrologic impacts of urban land use change and often do not consider how pollutants that wash off from different land uses affect water quality. L-THIA (Long-Term Hydrologic Impact Assessment) is an analysis tool that provides site-specific estimates of changes in runoff, recharge and non point source pollution resulting from past or proposed land-use changes. It gives long-term average annual runoff for a land use configuration, based on climate data for that area. In this study, the environmental and hydrological impact from the urbanized basin had been examined with GIS L-THIA in Korea.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.222-225
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• 2001

In urban environments, the surface land impermeability fundamentally related to urban growth emphasizes the environmental problems such as the storm water peak flow (so-called the urban flooding) and the pollution. The conventional urban drainage system provides a number of temporary reservoirs intercepting and retaining surface-derived pollutants following their introduction to and deposition upon the impermeable surface. Gully-pots are common features in urban drainage systems in Korea, which were installed for draining rainwater to prevent regurgitation in rainy season and retaining larger particles, hence minimizing pipe blockage problems. When the road runoff conveying sediment enters a gully-pot, the sediment mixes with the gully liquor causing direct pollution of receiving waters. The characteristics of local sediment contamination are usually related to the types of land use activities that take place or have taken place within the area., This study was undertaken to evaluate the spatial and temporal variations of the contamination of gully-pot sediments in Seoul with respect to heavy metals such as As, Cd, Co, Cr, Ni, Pb, Cu and Zn. The heavy metal data were examined according to the land use type. In this paper, sampling sites in Seoul were divided into six groups (commercial area, industrial area, residental area, motor way, rural area, and local pollution).

• Water for future
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• v.23 no.3
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• pp.329-340
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• 1990

The Paper presents the development and applications of physically-based urban runoff analysis model, URAM, which is capable of simulating sewer runoff hydrograhps and inundation conditions within a samll urban catchment. The model coniders three typical flow conditions of urban drainage networks, which are over-land flow, gutter flow, and conduit flow during a storm. Infiltration, retention storage and flow routing procedures are physically depicted in model. It was tested satisfactorily with the field data from a tested catchment having drainage area of 0.049k$m^2$. It was also applied to other urban areas and found to adequately simulate inundation areas and duration as observed during storms. The test results as well as model components are described in the paper.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.141-141
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• 2021

This study proposed an equation for Rainfall Threshold for Flood Warning (RTFW) for urban areas based on computer simulations. First, a coupled 1D-2D dual-drainage model was developed for nine watersheds in Seoul, Korea. Next, the model simulation was repeated for a total of 540 combinations of the synthetic rainfall events and watershed imperviousness (9 watersheds × 4 NRCS Curve Number (CN) values × 15 rainfall events). Then, the results of the 101 simulations with the critical flooded depth (0.25m-0.35m) were used to develop the equation that relates the value of RTFW to the rainfall event temporal variability (represented as coefficient of variation) and the watershed Curve Number. The results suggest that 1) the rainfall with greater temporal variability causes critical floods with less amount of total rainfall; and that 2) the greater imperviousness requires less rainfall to have critical floods. For validation, the proposed equation was applied for the flood warning system with two storm events occurred in 2010 and 2011 over 239 watersheds in Seoul. The results of the application showed high performance of the warning system in issuing the flood warning, with the hit, false and missed alarm rates at 68%, 32% and 7.4% respectively for the 2010 event and 49%, 51% and 10.7% for the event in 2011.

• Water for future
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• v.14 no.4
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• pp.13-18
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• 1981

The rainfall pattern analysis on time distribution characteristics of rainfall rates in important in determination of design flow for hydraulic structures, particularly in urban area drainage network system design. The historical data from about 400 storm samples during 31 years in Seoul have been used to investigate the time distribution of 5-minute rainfall in the warm season. Time distribution relations have been deveolped for heavy stroms over 20mm in total rainfall and represented by relation percentage of total storm rainfall to percentage of total storm time and grouping the data according to the quartile in which rainfall was heaviest. And also time distribution presented in probability terms to provide quantitative information on inter-strom variability. The resulted time distribution relations are applicable to construction of rainfall hyetograph of design storm for determination of design flow hydrograph and identification of rainfall pattern at given watershed area. They can be used in conjuction with informations on spatstorm models for hydrologic applications. It was found that second-quartile storms occurred most frequently and fourth-quartile storms most infrequently. The time distribution characteristics resulted in this study have been presented in graphic forms such as time distribution curves with probability in cumulative percent of storm-time and precipitation, and selected histograms for first, second, third, and fourth quartile stroms.