• Journal of Wetlands Research
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• v.17 no.3
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• pp.221-227
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• 2015

Urbanization increases the impervious cover, which affects the discharge of stormwater runoff and non-point source pollutants to the waterbodies. In order to improve the water quality and restore the aqua-ecosystem, the Ministry of Environment (MOE), Korea MOE introduced the Low Impact Development(LID) techniques on development projects. Therefore, research was performed to develop the bioretention technology for managing the stormwater runoff from urban areas. The test-bed was established on 2013 up to evaluate the performance of pollutant and runoff reduction. A total of 11 storm events have been monitored from November 2013 to present. Even though the SA/CA (surface area of bioretention/catchment area) is approximately 2.2%, the facility shows high pollutant and runoff reduction during storm events by increasing retention and infiltration capacities. The bioretention shows a 100% total runoff reduction at 0mm < R < 10mm rainfall range and more than 90% of runoff reduction at a rainfall range of 10mm < R < 20mm. Due to runoff volume reduction, more than 90% of nonpoint source pollutant were also removed by the bioretention.

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.929-941
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• 2008

The objectives of this study are to propose a system for combined use of a hydrologic and a hydraulic model for urban flood forecast model and to evaluate the system on the $300km^2$ Jungrang urban watershed area, which is relatively large area as an urban watershed and consequently composed of very complex drainage pipes and streams with different land uses. In this study, SWMM for hydrologic model and HEC-RAS for hydraulic model are used and the study area is divided into 25 subbasins. The SWMM model is used for sewer drainage analysis within each subbasin, while HEC-RAS for unstready flow analysis in the channel streams. Also, this study develops a GUI system composed of mean areal precipitation input component, hydrologic runoff analysis component, stream channel routing component, and graphical representation of model output. The proposed system was calibrated for the model parameters and verified for the model applicability by using the observation data. The correlation coefficients between simulated and observed flows at the 2 important locations were ranged on 0.83-0.98, while the coefficients of model efficiency on 0.60-0.92 for the verification periods. This study also provided the possibilities of manhole overflows and channel bank inundation through the calculated water profile of longitudinal and channel sections, respectively. It can be concluded that the proposed system can be used as a surface runoff and channel routing models for urban flood forecast over the large watershed area.

• Journal of Korea Water Resources Association
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• v.39 no.11 s.172
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• pp.935-946
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• 2006

This study proposed a new procedure of sustainable water resources planning to prevent the urban streamflow depletion, based on the Heathcote's study in 1998: (1) to understand the watershed component and processes, (2) to identify and quantify problems within the watershed, (3) to set clear and specific goals, (4) to develop a list of management options, (5) to eliminate infeasible options, (6) to test the effectiveness of remaining feasible options, and (7) to develop the final options. PSR(Presure-State-Response) concept was used for the determination of indicators of PSD(Potential Streamflow Depletion; step 2) and effect equation (step 7) and composite programming for the calculation of PSD. The instreamflow requirement was proposed as clear and specific goal (step 3) and was determined by the larger of the PHABSIM's environmental flow and the drought flow. A continuous rainfall-runoff model is necessary to test the effectiveness of alternatives. It should estimate not only the exact runoff but also the effect of landuse change, reservoir, infiltration facility and so on like SWAT(Soil and Water Assessment Tool). The proposed procedure will be applied on the corresponding paper.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.67-76
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• 2018

There are 34 mega-cities with a population of more than 10 million in the world. One of the highly populated cities in the world is Seoul in South Korea. Seoul receives $1,140million\;m^3/year$ for domestic water, $2million\;m^3/year$ for agricultural water and $6million\;m^3/year$ for industrial water from multi-purpose dams. The maintenance water used for water conservation, ecosystem protection and landscape preservation is $158million\;m^3/year$, which is supplied from natural precipitation. Recently, the use of the other water for preservation of water quality and ecosystem protection in urban areas is increasing. The objectives of this study is to develop the seasonal forecast method of environmental water in urban areas (Seoul, Daejeon, Gwangju, Busan) and to evaluate its predictability. In order to estimate the seasonal outlook information of environmental water from Land Surface Model (LSM), we used the observation weather data of Automated Synoptic Observing System (ASOS) sites, forecast and hind cast data of GloSea5. In the past 30 years (1985 ~ 2014), precipitation, natural runoff and Urban Environmental Water Index (UEI) were analyzed in the 4 urban areas. We calculated the seasonal outlook values of the UEI based on GloSea5 for 2015 year and compared it to UEI based on observed data. The seasonal outlook of UEI in urban areas presented high predictability in the spring, autumn and winter. Studies have depicted that the proposed UEI will be useful for evaluating urban environmental water and the predictability of UEI using GloSea5 forecast data is likely to be high in the order of autumn, winter, spring and summer.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.22 no.5
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• pp.45-56
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• 2019

Urban green areas are generally composed of relatively small and fragmented patches, but it is a critical factor for the quality of an urban environment. They have positive effects such as increasing green connectivity, reducing runoff, and mitigating urban heat. But, there is a lack of urban greening plans that consider the comprehensive effects of green space in real urban areas. To fill this gap in this literature, this study identifies a planning model that determines the optimal locations for maximizing green areas' multiple effects(e.g., heat mitigation and enhancement of connectivity) by using unused lots. This model also considers minimizing costs using meta-heuristic optimization algorithms. As a results, we finds 50 optimal plans that considers two effects within the limited cost in Nowon-gu. The optimal plans show the trade-off effect between connectivity, heat mitigation and cost. They also show the critical unused land lots for urban greening that are commonly selected in various plans. These optimal plans can effectively inform quantitative effectiveness of green space and their trade-off. We expect that our model will contribute to the improvement of green planning processes in reality.

• The Journal of Engineering Geology
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• v.33 no.3
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• pp.489-502
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• 2023

Urban floods pose significant challenges to cities worldwide, driven by the interplay between urbanization and climate change. This review examines recent studies of urban floods to understand their causes, impacts, and potential mitigation strategies. Urbanization, with its increase in impermeable surfaces and altered drainage patterns, disrupts natural water flow, exacerbating surface runoff during intense rainfall events. The impacts of urban floods are far-reaching, affecting lives, infrastructure, the economy, and the environment. Loss of life, property damage, disruptions to critical services, and environmental consequences underscore the urgency of effective urban flood management. To mitigate urban floods, integrated flood management strategies are crucial. Sustainable urban planning, green infrastructure, and improved drainage systems play pivotal roles in reducing flood vulnerabilities. Early warning systems, emergency response planning, and community engagement are essential components of flood preparedness and resilience. Looking to the future, climate change projections indicate increased flood risks, necessitating resilience and adaptation measures. Advances in research, data collection, and modeling techniques will enable more accurate flood predictions, thus guiding decision-making. In conclusion, urban flooding demands urgent attention and comprehensive strategies to protect lives, infrastructure, and the economy.

• Spatial Information Research
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• v.18 no.1
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• pp.49-56
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• 2010

Considering the flood problem in urban areas, it is important to estimate disaster risk using accurate numerical analysis for inundation. In this study, it is carried out to calculate inundation depth in Samcheok city which suffered from serious flood damage in 2002. The urban flood model was developed by cording Manning n, elevation, and building's rare on ArcGIS for reducing error on data exchange, and applied for estimating flood damage by grid. This paper describes the extraction of sewer lines and buildings area, estimates its influence on flood inundation extent, and integrated 1D/2D flow to simulate inundation depth in high-density building area. This paper shows an integrated urban flood modeling including rainfall-runoff, inundation simulation, and mathematical flood damage estimation, and will serve drainage design for reducing its damage.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.573-584
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• 2006

This study was carried out to investigate the causes of fish kills in the Yudeung Stream in Daejeon, Korea using literature reviews, governmental and our water quality monitoring data of the study site, rainfall data, intensive water quality monitoring during rainfall events, sediment pollutant contents and laboratory bioassay tests. Fish kill in urban streams can be caused by combined effect of reduction in dissolved oxygen concentration, increase in toxic material or increase in turbidity in waterbody due to introduction of surface runoff or effluent of combined sewer overflows after rainfall from the watershed areas. Despite of extensive and intensive field surveys and laboratory tests, it was found that those conventional methods have limitations to identify causes of fish kills in urban streams. It would be necessary to use dynamic water quality modeling to predetermine the range and level of water pollution in the stream and automatic water quality monitoring system that can collect water samples and detect water quality continuously.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.585-594
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• 2006

This study focused on the causes of fish kills and its prevention methods in Yudeung Stream, Daejeon, Korea. Intense field data, continuous water quality monitoring system and water quality modeling were applied to analyze the causes. Pollutant can be delivered to urban streams by surface runoff and combined sewer overflows in rainfall events. However, water quality analysis and water quality modeling results indicate that the abrupt fish kills in the Yudeung stream seems to be caused by combined effect of DO depletion, increase in turbidity and other toxic material. Excessive fish population in the study area may harm the aesthetic value of the stream and also has greater potential for massive fish kills. It is suggested to implement methods to reduce delivery of pollutants to the stream not only to prevent fish kills but also to keep balance of ecosystem including human uses. Frequent clean up of the urban surface and CSO, installation of detention basin will be helpful. In the long run, it seems combined sewer system has be replaced with separate sewer system for more effective pollutant removal in the urban area.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.3
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• pp.140-148
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• 2017

The effectiveness of the first flush treatment system using settling process was evaluated to reduce urban nonpoint source pollutant loads to surface water during storm events. A pilot scale system was constructed and tested in the field and surface runoff samples were collected automatically according to pre-defined conditions. Nine rainfall events were tested and average removal efficiencies of TSS (Total Suspended Solid), TP (Total Phosphorus) and TN (Total Nitrogen) were evaluated as 87.4%, 75.3%, and 43.6%, respectively. Concentration and removal efficiency of pollutants were found to be affected by an amount of rainfall and rainfall intensities of the respective events. This seemed to be caused by the greater particulate fractions of first flushed samples than the samples collected in later time periods during the same rainfall events. The study showed that it is possible to remove a significant portion of the nonpoint source pollutant loads in initial rainfall runoff by using a simple settling process for TSS and TP without requiring additional power or chemicals.