• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.535-546
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• 2008

Urbanization results in increased runoff volume and flowrate and shortening in time of concentration, which may cause frequent flooding downstream. The retardation structures are used to eliminate adverse downstream effects of urban stormwater runoff. There are various types of flow retardation measures include detention basin, retention basin, and infiltration basin. In this study, to present a rough standard about location of detention pond for attenuating peak flow of urban area, the runoff reduction effect is analyzed at outlet point when detention pond is located to upstream drainage than outlet. The runoff reduction effects are analyzed under the three assumed basins. These basins have longitudinal shape (SF = 0. 204), concentration shape (SF = 0. 782), and middle shape (SF = 0.567). Numerous variables in connection with the storage effect of detention pond and the runoff reduction effects are analyzed by changing the location of detention pond. To analyze runoff reduction effect by location of single detention pond, Dimensionless Upstream Area Ratio (DUAR) is changed to 20%, 40%, 60%, and 80% according to the basin shape. In case of multiple detention pond, DUAR is changed to 60%, 80%, 100%, 120%, and 140% only under the middle shape basin (SF = 0.567). Related figures and regression equations to determine the location of detention pond are obtained from above analysis of two cases in this study. These results can be used to determine the location of appropriate detention pond corresponding to the any runoff reduction such as storage ratio and peak flow ratio in urban watershed.

• Journal of the Korean Institute of Landscape Architecture
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• v.32 no.2
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• pp.78-85
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• 2004

To manage rainwater environmentally friendly, it is necessary to let the rainwater be infiltrated naturally and make reservoirs to detain it in the chosen spot. Not only should it be prepared to handle the city flood, but also it be a necessary alternative for establishing the ecological water circular system in cities. Therefore, considering the present rainwater. management system, this study analysed the status of products which can be interchanged from existent systems to rainwater infiltrating systems. In this study, the infiltrating equipment that is applicable to the Korean drainage system was developed. The case was studied out to investigate the effects of infiltrating and the detaining ability of the developed product. The case site, block 6 of Sang-am residence, was selected and analyzed. The amount of infiltration and detention per unit of the introduced facilities, i.e., infiltrating pipes and tanks were calculated. In this research, the amount of each infiltrating tank was revealed to be 1.353 m/hr and the amount of detention as 0.299 m/hr. And the amount of each infiltrating pipe was found to be 0.541 m/hr and the amount of detention was 0.118 m/hr. To examine the effects of the system, the total amount of the outlet before and after installing was compared and calculated. In doing this, a basis for deciding the arrangement and number of tanks and pipes of the infiltrating system was made.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.1
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• pp.1-8
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• 2011

This article proposes a hybrid approach involved in determining the size of stormwater control facilities as part of a very large scale urban retrofit project. The objective of the proposed hybrid approach is to restore the pre-development hydrologic cycle. Firstly, an appropriate IETD is determined to isolate single storm events from the continuous rainfall record. Then, using the NRCS-CN method, direct runoff and infiltration volume are computed for every storm events. Long-term statistics of direct runoff and infiltration volume are analyzed in each case of pre-development, post development, post development with detention only, and post-development with the proposed hybrid approach. In order to preserve long-term statistics of direct runoff and infiltration volume in the case of pre-development, the size of detention and infiltration-based retention are estimated using the genetic algorithm. The result shows that the proposed hybrid approach is very useful for restoring statistics of natural direct runoff and infiltration volume.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.415-426
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• 2001

After Disaster Impact Assessment(DIA) Program was particed, the wide variety of hydrological data are estimated by introducing the concept of critical storm duration to calculate the stormwater impoundments as the alternative of increasing runoff due to many developments. Critical storm duration is varied by a lot of hydraulic structures, drainage characteristics, temporal distribution of design rainfall, return period, and runoff models. In this study the methods of estimating the proper volume to design the stormwater impoundments are proposed to determine the required volume by comparing and analyzing the maximum stormwater impoundments in accordance with the impoundment volume and rainfall duration by using the concept of storage ratio presented in the existing studies. The methods of determining the critical storm duration of design rainfall which cause the maximum load from the runoff hydrograph will be studied as analyzing rainfall-runoff using the various runoff models and observed data.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1199-1203
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• 2005

Combined sewer overflows(CSOs) are themselves a significant source of water pollution. Therefore, the control of urban drainage for CSOs reduction and receiving water quality protection is needed. Examples in combined sewer systems include downstream storage facilities that detain runoff during periods of high flow and allow the detained water to be conveyed by an interceptor sewer to a centralized treatment plant during periods of low flow. The design of such facilities as stormwater detention storage is highly dependant on the temporal variability of storage capacity available(which is influenced by the duration of interevent dry periods) as well as the infiltration capacity of soil and recovery of depression storage. As a result, a contiunous approach is required to adequately size such facilities. This study for the continuous long-term analysis of urban dranage system used analytical Probabilistic model based on derived probability distribution theory. As an alternative to the modeling of urban drainage system for planning or screening level analysis of runoff control alternatives, this model have evolved that offer much ease and flexibility in terms of computation while considering long-term meteorology. This study presented rainfall and runoff characteristics or the subject area using analytical Probabilistic model. Runoff characteristics manifasted the unique characteristics of the subject area with the infiltration capacity of soil and recovery of depression storage and was examined appropriately by sensitivity analysis. This study presented the average annual COSs and number of COSs when the interceptor capacity is in the range 3xDWF(dry weather flow). Also, calculated the average annual mass of pollutant lost in CSOs using Event Mean Concentration. Finally, this study presented a dicision of storage volume for CSOs reduction and water quality protection.

• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.490-497
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• 2007

A Combined sewer overflows (CSOs) are themselves a significant source of water pollution. Therefore, the control of urban drainage for CSOs reduction and receiving water quality protection is needed. Examples in combined sewer systems include downstream storage facilities that detain runoff during periods of high flow and allow the detained water to be conveyed by an interceptor sewer to a centralized treatment plant during periods of low flow. The design of such facilities as stormwater detention storage is highly dependant on the temporal variability of storage capacity available (which is influenced by the duration of interevent dry periods) as well as the infiltration capacity of soil and recovery of depression storage. As a result, a continuous approach is required to adequately size such facilities. This study for the continuous long-term analysis of urban drainage system used analytical probabilistic model based on derived probability distribution theory. As an alternative to the modeling of urban drainage system for planning or screening level analysis of runoff control alternatives, this model have evolved that offer much ease and flexibility in terms of computation while considering long-term meteorology. This study presented rainfall and runoff characteristics of the subject area using analytical probabilistic model. This study presented the average annual COSs and number of COSs when the interceptor capacity is in the range $3{\times}DWF$ (dry weather flow). Also, calculated the average annual mass of pollutant lost in CSOs using Event Mean Concentration. Finally, this study presented a decision of storage volume for CSOs reduction and water quality protection.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3518-3524
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• 2015

Spatial and time variation of the precipitation in Korea is high, therefore, more than 2/3 of the annual precipitation is concentrated during the rainy season. Climate change also causes the intensive rainfall in the area of dense population, thus the occurrence frequency of the heavy flood in the impervious area has been increased. Therefore, the structural food mitigation measures such as the construction of the higher design frequency stormwater pipes, pumping stations, and/or detention ponds. The flood bypass tunnel or retention storage is also one of the efficient structures to mitigate flood damage in the urban area. However, the economic feasibility has been controversial because the flood bypass tunnel might be used once or twice a year. To solve the problem, the multi-functional tunnel for the urban traffic and flooding bypass has been considered. In this study, the design criteria of the road and water tunnel has been analysed and the composite design criteria is proposed for the multi-functional tunnel which is expected to be constructed.