Sangman Jeong

Salinity intrusion characteristics analysis using EFDC model in the downstream of Geum River.

As social interest in the environmental conservation and ecological restoration has recently increased, more research works have been done to resolve problems concerning environmental management of estuaries. In this study, a three-dimensional numerical model, Environmental Fluid Dynamics Code (EFDC) was used in the analysis of the salinity intrusion characteristics in the downstream of Geum River. The numerical simulation was performed to investigate the influence range for salinity intrusion when the gates were fully opened. The conditions used for simulation were the four flow regimes in Geum River Basin, Korea. Results indicated that the ranges of salinity intrusion from the barrage were 50.72 km (drought flow), 48.87 km (low flow), 46.56 km (normal flow) and 42.10 km (flood flow). These results indicated that the EFDC model used for numerical simulation has high accuracy. The result concluded in this study can be used as a basis in understanding the extent of salinity intrusion effects at different flow rates.

Seasonal nutrient uptake of plant biomass in a constructed wetland treating piggery wastewater effluent.

The surface-flow constructed wetland (CW) located in Nonsan City, South Korea, and constructed as the final stage of a piggery wastewater treatment plant that aims to treat high nutrient content effluent during dry days and stormwater runoff during wet days was monitored from October 2008 to November 2011. This research investigated the seasonal nutrient uptake of plant biomass in the CW and nutrient concentration changes in each treatment region under monsoon and temperate climate conditions. Results showed that the mean total nitrogen removal during summer (June to August) was higher by 13% than in spring (March to May), while total phosphorus removal was higher by 22% in fall (September to November) than in winter (December to February). All plants in the CW reached their maximum biomass coverage and weight in summer and minimum growth in winter. The highest N and P content in plants occurred in September with 583.2 g/m(2) and August with 62.0 g/m(2), respectively. Based on the results, it is recommended that the harvesting of plants should be conducted during the time of the peak nutrient uptake and before the plants release the nutrient content back to the CW. The dependence of nutrient removal efficiency on plants is not so significant. In order to increase the nutrient removal rate by plant uptake, it is suggested that the treatment regions in the CW be covered by plants.

Treatment performance of a constructed wetland during storm and non-storm events in Korea.

The efficiency of a free water surface flow constructed wetland (CW) in treating agricultural discharges from stream was investigated during storm and non-storm events between April and December, 2009. Physico-chemical and water quality constituents were monitored at five sampling locations along the flow path of the CW. The greatest reduction in pollutant concentration was observed after passing the sedimentation zone at approximately 4% fractional distance from the inflow. The inflow hydraulic loading, flow rates and pollutant concentrations were significantly higher and variable during storm events than non-storm (baseflow) condition (p <0.001) that resulted to an increase in the average pollutant removal efficiencies by 10 to 35%. The highest removal percentages were attained for phosphate (51 ± 22%), ammonium (44 ± 21%) and phosphorus (38 ± 19%) while nitrate was least effectively retained by the system with only 25 ± 17% removal during non-storm events. The efficiency of the system was most favorable when the temperature was above 15 °C (i.e., almost year-round except the winter months) and during storm events. Overall, the outflow water quality was better than the inflow water quality signifying the potential of the constructed wetland as a treatment system and capability of improving the stream water quality.

Sensitivity Assessment on Daecheong Dam Basin Streamflows According to the Change of Climate Components - Based on the 4th IPCC Report -

Climate change and global warming are prevalent all over the world in this century and many researchers including hydrologists have studied on the climate change. This study also studied the impact of climate change on streamflows of a basin in Korea. The SWAT model was used to assess the impacts of potential future climate change on the streamflows of the Daecheong Dam Basin. Calibration and validation of SWAT were performed on a monthly basis for the year of 1982-1995 and 1996-2005, respectively. The impact of seven 15-year(1988-2002) scenarios were then analyzed for comparing it to the baseline scenario. Among them, scenario 1 was set to show the result of doubling , scenario 2-6 were set to show the results of temperature and precipitation change, and scenario 7 was set to show the result of the combination of climatologic components. A doubling of atmospheric concentration is predicted to result in an maximum monthly flow increase of 11 percent. Non-linear impacts were predicted among precipitation change scenarios of -42, -17, 17, and 42 percent, which resulted in average annual flow changes in Daecheong Dam Basin of -55, -24, 25, and 64 percent. The changes in streamflow indicate that the Daecheong Dam Basin is very sensitive to potential future climate changes and that these changes could stimulate the increased period or severity of flood or drought events.

Natural Disaster Vulnerability Assessment at Boroughs and Census Output Areas in Seoul Focusing on Socio-economic Perspective

우리나라에서는 매년 호우, 태풍, 대설 등 자연재해로 인하 여 많은 피해가 발생되고 있으며, 2013년도에서는 총 1,721억 원의 재산피해가 발생하였는데 이중 90% 이상이 호우에 기 인하였다. 또한 재해로 인한 피해액과 그에 따른 복구액 역시 점점 증가하고 있는 추세를 보이고 있다(NEMA, 2013). 특히 나 2011년 서울시 우면산 산사태, 2014년 부산·경남 지방에 서 폭우 등으로 인하여 많은 재산 피해와 인명피해가 발생하 였으며, 이러한 사건은 사회적인 관심을 불러일으켰다. 우리나라의 경우 도시지역 인구밀도가 높으며, 이로 인해 도시지역에 재해가 발생되면 치명적인 피해를 입게 된다. 따 라서 도시지역의 자연재해에 대한 대응책 마련이 반드시 필 요하다. 이를 위해서는 어떤 지역에서 자연재해가 발생하였을 경우 얼마나 많은 피해를 입는지에 대한 정량적인 평가가 우 선적으로 진행되어야 한다. Smith and Ward(1998)은 홍수에 Abstract

Development of GIS-based disaster assessment system to reduce flood risks in urbanized creeks

AbstractThis study developed a disaster assessment system, which integrated flood inundation, risk analysis system, and a decision support system. The parameter representation of the model was selected through sensitivity analysis, used for automated parameter optimization of the model. The Bocheong watershed in South Korea was selected for this study. The results of the simulation were used for disaster assessments; estimated results were calculated basing from flood damages from historical flood disasters, GIS, population, and inundation results. Lastly, this study developed a user-support system to provide real-time meteorological and hydrological data to local government and disaster situation room in South Korea. From the results of the evaluation, the developed model in this study was proven to be more excellent than ModClark model. The application of this model was found superior for ungaged basin such as mountainous area and small creek basins.

Seasonal treatment efficiency of surface flow constructed wetland receiving high nitrogen content wastewater

Abstract This research investigated the performance of a constructed wetland (CW) that functions as a post-treatment unit for the secondary effluent of a piggery wastewater treatment facility. The pollutant mass removal efficiency was evaluated from 37 sampling events on non-rainy days during 2008–2010. Based on the findings, the pollutant concentrations decreased somewhat along the cells from the influent to the effluent while DO and pH increased along the cells and appeared to peak at the deep marsh region during the spring season. The overall cumulative treatment efficiencies for the entire monitoring period were 53% for total suspended solids; 35–37% for biological oxygen demand and chemical oxygen demand; 33% for total phosphorous; and 17–21% for total nitrogen and other nitrogen forms. The main reason for the low treatment performance was attributed to the low carbon to nutrient ratio (i.e., the COD/BOD:TN:TP ratio) in the CW influent. Moreover, algal bloom was frequently observed in the deep marsh ...

Characteristics of contaminant and phosphorus existence types in sediment of a constructed wetland

ABSTRACT This research investigated the physical and chemical characteristics of sediment deposited at the bottom soil layer of free water surface flow constructed wetland (CW) treating runoff impacted stream water from an agricultural area which is important when determining the long-term maintenance requirements over the lifetime of the CW. Based on the findings, the influent to the CW still was polluted with high concentration of nutrients with TN and TP exceeding five and two times the water quality standard in rivers and lakes. The accumulation of sediment at the first treatment unit (sedimentation zone) of the CW augmented after the summer season signifying that the dredging of sediment must be conducted after the rainy season or until before the winter season. It was found out that the main phosphorus (P) types existing at the sediment in the CW were residual-P (R-P) and non-apatite-P (NAI-P) constituting to almost 90% of total P. While NAI-P can be released in the natural environment by increasing...

Drought assessment based on real-time drought index

AbstractThe continuous increase in water demand is primarily caused by the explosive population growth rate due to urbanization and industrialization, and thus, is accelerated in both agricultural and residential parts. Drought adversely affects the quality of life and the whole economic situation of the country, and therefore, an accurate assessment of the incidence of water shortage is required. The existing researches for calculating drought indices do not consider the water demand and the water supply from irrigation facilities, streams, and water storages; thus, existing hydrological drought indices have many limitations in determining actual drought situations in the country. Only water supply without water demand is considered on the existing hydrological drought index therefore, water shortage cannot be calculated. On the other hand, real-time drought index (RDI) evaluates drought on a daily basis in real-time and calculate water shortage according to residential, agricultural, and industrial wate...

Assessment of aquatic habitat effect by artificial change of streambed topography

As interest in ecosystems and the environment has recently increased, efforts for the preservation and restoration of river ecosystems have increased. The purpose of this study is to estimate the fish physical habitat by artificial change of streambed topography applying two-dimensional simulation model, River2D. A total reach length of 130 m along the Je stream located within the Geum River basin in Korea was used in this study. The target fish is the dominant fish species, Zacco platypus, which was evaluated for two growth steps (adult and spawning). Five scenarios were considered which included the installation of small dams at three different heights (0.25 m, 0.50 m, and 1.00 m) and installation of small pool with 0.25 m and 0.50 m depth. Results indicated that for natural streambed conditions the adult optimum flow was 1 m(3)/s, and the spawning optimum flow was 3 m(3)/s. The mean annual outflow for the natural condition was 0.64 m(3)/s, lower than the evaluated optimum flows. Applying the three discharges observed in 2008 to the five scenarios, the installation of the small dam increased the weighted usable area (WUA) while the installation of pools decreased the WUA, both as compared to the WUA for the natural condition.