Kyoung-Hak Hyun

The purpose of this study was to develop a low impact development-based district unit planning (LID-DP) model and to verify the model by applying it to a test site. To develop the model, we identified various barriers to the urban planning process and examined the advantages of various LID-related techniques to determine where in the urban development process LID would provide the greatest benefit. The resulting model provides (1) a set of district unit planning processes that consider LID standards and (2) a set of evaluation methods that measure the benefits of the LID-DP model over standard urban development practices. The developed LID-DP process is composed of status analysis, comprehensive analysis, basic plan, and sectoral plans. To determine whether the LID-DP model met the proposed LID targets, we applied the model to a test site in Cheongju City, Chungcheongbuk-do Province, Republic of Korea. The test simulation showed that the LID-DP plan reduced nonpoint source pollutants (total nitrogen, 113%; total phosphorous, 193%; and biological oxygen demand, 199%); reduced rainfall runoff (infiltration volume, 102%; surface runoff, 101%); and improved the conservation rate of the natural environment area (132%). The successful application of this model also lent support for the greater importance of non-structural techniques over structural techniques in urban planning when taking ecological factors into account.

This study aims to examine the treatment of graywater (GW), especially bathroom wastewater, using subsurface-flow constructed wetlands (CWs) in an apartment complex. It analyzed the removal of organic matters and nitrogen, the status of a wetland by depth, and microbial communities under the conditions of aeration and non-aeration at the inlet section, and planting and non-planting. The results of this study show that aeration at the inlet section and planting affect ORP, , and nitrogen by water flowing distance and water depth in a wetland. The result of COD_cr removal seems to satisfy the Korean standard (below 20 mg/L (COD_mn)) of reuse water quality in all three operational conditions. The aeration at the inlet section has the advantages of effectively removing organic matters at the inlet section, thus preventing its clogging, and removing nitrogen through the nitrification. Aeration at the inlet section and planting are expected to have a positive effect on the wetland status and GW treatment. Therefore, aeration at the inlet and planting will be helpful to construct and operate an artificial wetland in residential areas such as a multi-family housing complex. Ammonia-oxidizing bacteria including Nitrosomonas, Nitrosospira, Nitrosococcus and denitrifying or nitrate-reducing bacteria such as Thiobacillus, Achromobacter, Pseudomonas, Micrococcus belong to the classes of β-proteobacteria, γ-proteobacteria, and Actinobacteria. These microbial communities found in this study seem to contribute to nitrogen removal. But, the roles of microbial community in CWs need to be further investigated, both qualitatively and quantitatively.

An analysis of the impact of a low impact development (LID) on runoff was performed using a Storm Water Management Model 5 (SWMM5)–LID model. The SWMM5 package has been developed to facilitate the analysis of the hydrologic impacts of LID facilities. Continuous simulation of urban stormwater runoff from the district which included the LID design was conducted. In order to examine the impact of runoff in the LID district the first, second and third highest ranked flood events over the past 38 years were analyzed. The assessment estimated that a LID system under historical storm conditions would reduce peak runoff by approximately 55–66% and runoff volume by approximately 25–121% in comparison with that before the LID design. The impact on runoff was also simulated under 50, 80 and 100 year return period conditions. Under these conditions, the runoff reductions within the district were estimated to be about 6–16% (peak runoff) and 33–37% (runoff volume) in comparison with conditions prior to the LID. It is concluded from these results that LID is worthy of consideration for urban flood control in future development and as part of sewer and stormwater management planning.

An increase in impermeable surfaces due to burgeoning urbanization is creating problems of non-point source, deterioration of urban amenities and the urban water cycle. Therefore, stormwater management with natural drainage has been attempted in Korea as a countermeasure. Objectives of this study are analysis of impact on heavy metals and distribution characteristics of the heavy metals in soil in infiltration splash blocks and rain gardens for management of roof runoff from apartment buildings. In this study, infiltration splash blocks and rain gardens were constructed to hold and infiltrate runoff from an apartment building roof. The distribution of heavy metals in soil in infiltration splash blocks and rain gardens was analyzed. There is a common feature that heavy metals were detected more in soil from the infiltration devices than in the surrounding soil in the order of Cu>Cd>Zn>As>Pb. The levels of these heavy metals are significantly lower than the Korea soil pollution standards. However, the distribution characteristics of Cu, Cd, Zn, As, and Pb in the splash blocks and rain gardens soil show that these heavy metals are influenced by roof runoff. This means that roof runoff could also be a non-point source.

Urban development is the primary cause of the expansion of impervious areas. Urbanization reduces infiltration of rainwater, increases runoff volume, and finally has an effect on the hydrological cycle and urban environment. To solve these problems, Low Impact Development (LID) methods have been used to restore the natural hydrology of predevelopment sites using site design techniques such as infiltration, evaporation, and retention. SWMM5 has been developed as a model to analyze the hydrologic impacts of LID facilities. This study performed hydrologic analysis and evaluated the flood reduction effect of the Jangjae Stream watershed by the design of LID facilities of the rainwater management demonstration district of AsanTangjung New Town (Korea). LID facilities in this study were comprised of infiltration trench, rain barrel, vegetation swale, etc. SWMM5 was calibrated using rainfall data of the 7th and the 14th of July, 2011 and was verified using rainfall data of the 10th and the 11th of August, 2011. This study analyzed flood reduction effect on 50 to 100 y return period. Based on the results of this study, the reduction of flood peak discharge by each return period of storms was estimated to be about 7 to 15%.