• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.745-753
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• 2017

In this study, a design strategy is proposed to restore the distorted urban water cycle to the natural water cycle through the LID facility. This is accomplished by determining the optimal LID facility design capacity through which flow duration curves remain the same before and after urban development. A part of the Noksan National Industrial Complex in Busan was selected as the study area and EPA SWMM was constructed to simulate long-term stormwater for various land use scenarios and LID facility design capacity. In the case that the study area was assumed to be a forest area or an agricultural area before urban development, it was found that it was necessary to allocate 7.3% or 5.5% of the impervious area to the area of the bio-retention in order for the flow duration curve to remain the same as before urban development. As a result of the sensitivity analysis of the bio-retention design capacity according to regional rainfall characteristics, the design capacity of 3.8~5.5% of impervious area is needed for the development of agriculture area. Therefore, it can be seen that the optimum capacity can be significantly different according to regional rainfall characteristics. On the other hand, as a result of analyzing the sensitivity of the design capacity according to the variation of the depth of each layer constituting the bio-retention and the size of contributing catchment area, the sensitivity of the optimal design capacity with respect to the design specifications of the bio-retention and the size of contributing catchment area was not significant.

• Journal of the Society of Disaster Information
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• v.11 no.3
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• pp.318-328
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• 2015

Effective urban flood reduction and restoration of natural water cycle at present include the application of permeable pavements. The application of permeable pavement addresses urban water cycle and disaster related events which gained attention internationally. However, few researches have been conducted to investigate unsaturated behavior and evaluate the water characteristics curves of these type of pavement materials most especially in the unsaturated state. In this study, first the saturated permeability and the soil-water characteristics curve of a pervious concrete are evaluated based on laboratory tests, and, based on experimental results, the infiltration of permeable pavement system is numerically modelled. In the soil-water characteristics curve of a pervious concrete, the volumetric water content drops very steeply after the air entry value with increasing matric suction. From the finite element analyses, the performance of the permeable pavement when compared to impermeable pavement, confirmed that the whole system effectively delayed and reduced runoff.

• Journal of Environmental Policy
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• v.13 no.3
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• pp.43-73
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• 2014

Cities in Korea have rapidly urbanized and they are not well prepared for natural disasters which have been increased by climate change. In particular, they often struggle with urban flooding. Recently, green infrastructure has been emphasized as a critical strategy for flood mitigation in developed countries due to its capability to infiltrate water into the ground, provide the ability to absorb and store rainfall, and contribute to mitigating floods. However, in Korea, green infrastructure planning only focuses on esthetic functions or accessibility, and does not think how other functions such as flood mitigation, can be effectively realized. Based on this, we address this critical gap by suggesting the new green infrastructure planning framework for improving urban water cycle and maximizing flood mitigation capacity. This framework includes flood vulnerability assessment for identifying flood risk area and deciding suitable locations for green infrastructure. We propose the use of the combination of frequency ratio model and GIS for flood vulnerability assessment. The framework also includes the selection process of green infrastructure practices under local conditions such as geography, flood experience and finance. Finally, we applied this planning framework to the case study area, namely YeonJe-gu an Nam-gu in Busan. We expect this framework will be incorporated into green infrastructure spatial planning to provide effective decision making process regarding location and design of green infrastructure.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.2
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• pp.251-259
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• 2013

Among various Green Infrastructure measures for urban stormwater management, effects of porous pavement were quantitatively examined in terms of hydrological cycle. Different scenarios for porous pavement were introduced on a SWMM model and the effects were compared and analysed using discharge hydrographs. Two types of pavements having different runoff coefficients (0.05 & 0.5) were introduced to cover different ratio of entire road areas (100 %, 77.5 % and 40.4 %) and these made up in total 6 different scenarios. Total runoff volume was reduced and peak flow was significantly decreased by applying the porous pavement. The highest reduction for total runoff was shown from S-6(covering area: 100 %, runoff coefficient: 0.05) as 19 % followed by S-5(covering area: 77.5 %, runoff coefficient: 0.05, 16 %), while that of S-2(covering area: 40.4 %, runoff coefficient: 0.05) and S-1(covering area: 40.4 %, runoff coefficient: 0.5) were the lowest with 8 % and 5 %. This proved that the application of porous pavement would improve urban hydrological cycle.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.26-36
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• 2009

Combined sewer system (CSS) has been built in the most urban areas across the nation. During dry weather conditions, CSS works fine. But during heavy rain storms, combined sewage frequently overflows into the stream. This study simulated the hydrologic cycle and pollutant loads (BOD, SS, TN and TP) in the Mokgamcheon watershed considering combined sewer overflows (CSOs). PC storm water management model (PCSWMM) was used for continuous simulation and CSOs are considered using the flow divider. Sensitivity analysis, calibration and verification for water quantity and quality are carried out. To verify CSOs, field measurements of CSOs are compared with simulated results. As a result, 41.3% of precipitation flows into the stream directly and 1.1% of water supply flows into stream as CSOs. 6.5% of BOD total loads, 12.0% of SS, 13.6% of TP, and 29.2% of TN are from CSOs. This result will be effective to the integrated watershed management for sustainability.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.145-145
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• 2021

Water distribution networks (WDNs) are designed to satisfy water requirement of an urban community. One of the central issues in human history is providing sufficient quality and quantity of water through WDNs. A WDN consists of a great number of pipelines with different ages, lengths, materials, and sizes in varying degrees of deterioration. The available annual budget for rehabilitation of these infrastructures only covers part of the network; thus it is important to manage the limited budget in the most cost-effective manner. In this study, a novel pipe replacement scheduling approach is proposed in order to smooth the annual investment time series based on a life cycle cost assessment. The proposed approach is applied to a real WDN currently operating in South Korea. The proposed scheduling plan considers both the annual budget limitation and the optimum investment on pipes' useful life. A non-dominated sorting genetic algorithm is used to solve a multi-objective optimization problem. Three decision-making objectives, including the minimum imposed LCC of the network, the minimum standard deviation of annual cost, and the minimum average age of the network, are considered to find optimal pipe replacement planning over long-term time period. The results indicate that the proposed scheduling structure provides efficient and cost-effective rehabilitation management of water network with consistent annual budget.

• Journal of Wetlands Research
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• v.23 no.1
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• pp.74-84
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• 2021

Active stormwater management is essential to minimize the impact of urban development and improve the hydrological cycle system. In recent years, the Low Impact Development (LID) technique for urban stormwater management is attracting attention as a reasonable alternative. The Storm Water Management Model (SWMM) is actively used in urban hydrological cycle improvement projects as it provides simulation functions for various GI (Green Infra) facilities through its LID module. However, in order to simulate GI facilities using SWMM, there are many difficulties in setting up complex watersheds and deploying GI facilities. In this study, a model that can evaluate the performance of GI facilities is proposed while implementing the core hydrological process of GI facilities. Since the proposed model operates based on hydrological routing, it can not only reflect the infiltration, storage, and evapotranspiration of GI facilities, but also quantitatively evaluate the effect of improving urban hydrological cycle by GI facilities. The applicability of the proposed model was verified by comparing the results of the proposed model with the results of SWMM. In addition, a discussion of errors occurring in the SWMM's permeable pavement system simulation is included.

• Journal of Korea Water Resources Association
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• v.39 no.8 s.169
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• pp.703-716
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• 2006

The flow duration curves in the present and the ideal hydrologic cycle were derived using SWAT model. The present situation is the landuse and the groundwater withdrawal in the year of 2000 and the ideal situation is the landuse of 1975 and no groundwater withdrawal. These results were compared with the previous instream flow requirements which are the larger flow between the average drought flow and environmental control flow. As a result, the present and ideal drought flows of Ojeoncheon, Hakuicheon, Samseongcheon, and Sammakcheon, were the same and the drought flows of Samseongcheon and Sammakcheon were even zero since the baseflow is very little due to the small and mountainous watersheds. The previous instream flow requirement for the riverine function is also larger than the low flow of the ideal hydrologic cycle. The present method to set the instream flow requirement is not proper for the small mountainous watershed since it can be usually overestimated and drive the artificial measures to secure the streamflow Therefore, another method should be developed such as the low flow and the average flow between the drought flow and the low flow of the ideal hydrologic cycle using the proper hydrologic simulation model such as SWAT which can consider the landuse.

• KIEAE Journal
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• v.14 no.3
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• pp.15-21
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• 2014

In this study, we developed a modular rainwater infiltration system that can be applied for general purposes in urban areas to prepare for localized heavy rain caused by climatic change. This study also analyzed the system's effects on reducing runoff. An analysis of the system's effects on reducing runoff based on rainfall data and monitoring data obtained between September 2012 and December 2013 after the system was installed showed that approximately 20~22% of the runoff overflowed from the infiltration facility. Also, an analysis of the runoff that occurred during the monsoon season showed that 25% of the runoff overflowed through the storm sewer system of the urban area. These results show that the rainwater overflows after infiltrating the detention facility installed in the area during high-intensity rainfall of 100mm or higher or when precipitation is 100mm for 3~4 days without the prior rainfall. According to precipitation forecasts, torrential rainfall is becoming increasingly prevalent in Korea which is increasing the risk of floods. Therefore, the standards for storm sewer systems should be raised when planning and redeveloping urban areas, and not only should centralized facilities including sewer systems and rainwater pump facilities be increased, but a comprehensive plan should also be established for the water cycle of urban areas. This study indicates that decentralized rainwater management can be effective in an urban area and also indicates that the extended application of rainwater infiltration systems can offer eco-friendly urban development.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.6
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• pp.919-926
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• 2006

In this study, environmental impact assessments of wastewater treatment plant (WWTP), sewerage system, and tailrace were performed using LCA methodology. The life cycle stages were divided into 3 categories; construction stage, maintenance stage and demolition & disposal stage. As a tool of impact assessment, Ecoindicator99 containing fate analysis, exposure & effect analysis and damage analysis, was used. As tile results of WWTP LCA, more than 80% of environmental impact was produced from maintenance stage. On the other hand, most of environmental impact was produced from construction stage in the case of tailrace and sewerage system construction.