• Journal of Korea Water Resources Association
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• v.34 no.2
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• pp.119-130
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• 2001

At-site and regional frequency analyses of annual maximum 1-, 2-, and 3-days rainfall in Han River basin was performed and compared based on the regional L-moments algorithm. To perform regional frequency analysis, Han River basin was subdivided into 3 sub-basins such as South Han River, North Han River, and downstream regions. For each sub-basin, the discordancy and homogeneity tests were performed. As the results of goodness of fit tests, lognormal model was selected as an appropriate probability distribution for both South Han River and downstream regions and gamma-3 model for North han River region. From Monte carlo simulation, RBIAS and RRMSE of the estimated quantiles from regional frequency analysis and at-site frequency analysis were calculated and compared each other. Regional frequency analysis shows less RRMSE of the estimated quantiles than at-sites frequency analysis in overall return periods. The differences of BRMSE between two approaches increase as the return period increases. As a result, it is shown that regional frequency analysis performs better than at-site analysis for annual maximum rainfall data in Han River basin.

• Journal of Korean Society on Water Environment
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• v.35 no.1
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• pp.55-63
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• 2019

The Four Major Rivers Restoration Project started in 2009 and completed in early 2013 is a large-scale inter-ministry SOC project investing ₩22.2 $10^{12}$ and one of the Project's objectives was to enhance the water-quality grade through recovering the river eco-system and environment. The average concentration and probability distribution of water-quality constituents at given and selected sampling sites are very significant elements for analyzing and controlling the water-quality of rivers or reservoirs effectively. Average concentration can be estimated by point estimator, distribution function of water-quality constituents or Bootstrap method, in which the distribution function estimated with more data in case of insufficient dataset, is applied. Ipo and Gangcheon water-quality monitoring stations in South Han River were selected to compare and analyze the variation of concentration before and after Ipo and Gangcheon Weirs construction, using the whole 4-year's data, from 2005 to 2008 and from 2014 to 2017. Water-quality constituents such as BOD and COD relating to oxygen demanding wastes and TP and Chlorophyll-a relating to the process of nutrient enrichment called eutrophication were also selected. The guidelines for water-quality control and management after weir construction including evaluation of water-quality constituents' variations can be presented by this paper.

• Journal of Wetlands Research
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• v.19 no.3
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• pp.353-358
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• 2017

As a drinking water source of 26 millions people of Seoul metropolitan region, Han river is one of the most important basin. Managing the Non-point source pollution which is regarded as the main cause of water pollution including refractory organic matter is important thing. This research investigates the runoff characteristics of organic matters from main 3 rivers (South Han, North Han, Kyungan). Water quality measurement items include not only carbon-based TOC (Total Organic Carbon), DOC (Dissolved Organic Carbon), POC (Particulate Organic Carbon) but also R-TOC (Refractory Total Organic Carbon), R-DOC (Refractory Dissolved Organic Carbon), R-POC (Refractory Particulate Organic Carbon) is researched. The research shows that R-TOC takes approximately 61~83% of TOC. Most of the R-TOC is consist of R-DOC (72~77%). Refractory organic matter have a stable runoff characteristics compared to other organic matter. The organic matter concentrations of South Han river and Kyungan river are the highest in spring time and show a gradual decline. The concentrations of Kyunan river is the highest. Kyungan river's small area and the high city land use ratio seem to be the reason. Loading of organic matter in summer time takes the most loading (62~84%). TOC loadings per unit area of each river is Kyungan river ($1.22ton/km^2$), South Han river ($1.01ton/km^2$), North Han river ($0.91ton/km^2$).

• Journal of the korean society of oceanography
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• v.38 no.2
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• pp.80-86
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• 2003

The horizontal distributions of $^{224}Ra$ (half life=3.4 days) and $^{223}Ra$ (half life=11.3 days) were measured in surface seawaters of the Nakdong River estuary and the South Sea of Korea in April and October 2002. In order to determine these short-lived Ra isotopes, we used a delayed coincidence counter which is much more rapid and accurate than traditional methods. In an estuarine mixing zone (salinity, ~l6 ppt), the activities of $^{224}Ra\;and\;^{223}Ra$ were much greater than what would be expected from a mixture of freshwater and seawater in the Nakdong River estuary. This excess Ra may be a result of Ra desorption from fresh sediments originating from the river upstream. However, in the more open areas of the Nakdong River estuary (salinity>30 ppt) and the South Sea of Korea, $^{224}Ra\;and\;^{^{223}Ra$ activities decreased exponentially as a function of distance offshore. Using the decrease of $^{223}Ra$ with distance offshore in the South Sea of Korea, we estimated the apparent horizontal eddy diffusivities. The apparent eddy diffusion coefficients in South Sea of Korea are calculated to be approximately $3500-8000\;\textrm{m}^2/sec$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.173-181
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• 1993

Under natural conditions, rivers do not in general take straight courses but instead take winding courses. This is known as meandering of rivers. Meandering of rivers are so complicated because of the mutual interactions between flow and movable boundaries. In quantitative information, it is important to predict the future location of a river channel(channel migration) because in selecting a bridge site or a location of a road. It may be valuable to know the future impact of a nearby river on those structures. When the prediction model of the migration of channel is used in domestic rivers with high coefficient of river regime, it is rational to use the periodical dominant discharge (PDD), which is named firstly by the author, instead of the average discharge. According to the analysis of the erosion coefficient, the mean deviation on the channel migration, and the bed scour factor, it can bring shedding light on the fact that the discharge is one of the dominant components in channel migration. In project area, the discharge that can shift the channel is slightly greater than 6,000CMS. The prediction model of the migration of channel estimated the erosion coefficient, $E_0$ by the data from the South Han River. This estimated value from the South Han River was also used to predict the migration of the South Han River in year 2000.

• Journal of Korean Society on Water Environment
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• v.30 no.4
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• pp.429-440
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• 2014

This study was conducted to investigate the main cause of water quality deterioration during the spring season in the transition zone between the South Han River and the river-reservoir Paldang. A water quality model modified from QUAL2E (U.S.EPA) was used, and the model showed that eutrophication and algal production in the low flow season affected about 60% of the organic pollution at the downstream of the South Han River. This result means that phosphorus control is prior to external organic material management to ameliorate the deterioration of water quality in the water body.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.97-110
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• 2012

In case of the axial line bikeway, the residents in the riverside use it frequently but those in the city center hardly do as the axis is formed along the riverside of the Han river. This situation happens due to the inefficient connectivity between the bikeway that leads to the riverside and that in the city center, which means the administrative policies have been focused on the facilities rather than on raising connectivity of the bikeway networks in the south of the Han River. Also, this is the point of time when a reasonable improvement plan is needed to raise the accessibilities of the bikeways in Seoul, not just a utilization of those in the south of the Han River. This study intends to analyse the connectivity between Gangseo (west of the Han River) and Gangdong (East of the Han River) districts by comparing the current spatial structure in the southern areas of the Han River and that after the installation of the axial line, and that after installation of the ordinary bikeway respectively with use of the Space Syntax Model, and to predict resultant changes there of. The Space Syntax Model was used as the major method of analysis in this study to find out characteristics of the bikeways in the south of the Han River. Consequently, as the analysis shows that when the bikeways in the Gangseo and Gangdong-gu districts are connected, the accessibility of the bikeways in the south of the Han River will improve while the spatial structure intelligibility will be lowered, it can be said the prediction rate in the all areas is low compared with the current status. It is analyzed that the intelligibility of the current bikeways in the south of the Han River appeared highest when compared with those of plans for installation of the axial line and ordinary bikeway because they don't interconnect with other areas.

• Journal of Korean Society on Water Environment
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• v.27 no.3
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• pp.306-313
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• 2011

In this paper, runoff characteristics of South-Han river watershed in terms of refractory organic matters were investigated. The concentrations of DOC, POC, R-DOC, R-POC in runoff and flow rates were determined by monitoring 27 times in dry season and 4 times in rainy season. The concentrations of the dissolved refractory organic matter, R-DOC was the lowest in fall and similar in the other dry seasons. The particulate refractory organic matter, R-POC showed less fluctuation than R-DOC. In summer, mass loading was the highest than other dry seasons. The concentrations of R-DOC, R-POC were showed to be affected by runoff volume. The mass loading grows higher as runoff volume gets higher.

• Economic and Environmental Geology
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• v.35 no.2
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• pp.113-120
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• 2002

Oxygen and hydrogen isotopic compositions of stream water in the Han river basin are expressed by the equation of $\delta$D=6.6$\delta$$^{18}$ O-7.4, which is not satisfy the meteoric water line ($\delta$D=8$\delta$$^{18}$ O+10). It might be depended on the local climatic condition and the evaporation effect in the Han river basin. The $\delta$$^{18}$ O and $\delta$D values of stream water in the Han river basin range from -8.2 to -10$\textperthousand$ (avg. -9.1$\textperthousand$) and -60 to -96$\textperthousand$ (avg. -69$\textperthousand$), respectively. The stream water from the South Han river (8$\delta$$^{18}$ O= -8.9~ -10$\textperthousand$, avg.-9.3$\textperthousand$ $\delta$D: -66~ -96$\textperthousand$, avg.-69$\textperthousand$) is slightly more depleted in $^{18}$ O and D than those of North Han river ($\textperthousand$$^{18}$ O= -8.4~ -9.7$\textperthousand$, avg. -9.2$\textperthousand$, $\delta$D= -64~ -95$\textperthousand$, avg. -69$\textperthousand$). It reflects more altitude effect than the effect of latitude and Inflow of the $^{18}$ O eniched S $O_4$$^{2-}$ and HC $O_3$- from the carbonate rock and sulfide minerals in the Taebagsan and Hwanggangri mineralized zone. The Main stream water of the Han river having $\delta$D: -60~ -76$\textperthousand$ (avg.-68$\textperthousand$) and $\textperthousand$$^{18}$ O= -8.2~-10$\textperthousand$ (avg.9.0$\textperthousand$) is enriched in $^{18}$ O compared to the South and North Han river waters, which is caused by the evaporation effect. Binary simple mixing ratio of the Main Han river water between South and North Han river waters was obtained to be 6 : 4 by the isotopic data, suggesting a strong influence of South Han river water to the Main Han river water.

• Environmental Engineering Research
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• v.19 no.3
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• pp.229-240
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• 2014

Rain events are extremely important for phosphorus (P) dynamics in rivers since large portions of annual river P loads can be transported in particulate forms during only a few major events. Despite their importance, a precise estimation of P contribution in river sediments after rainy seasons has rarely been reported. This study estimated the longitudinal variation in the concentrations of different inorganic P fractions in bed sediments of the South Han River over a rainy season, through using the sequential extraction method. Non-apatite P was the dominant form, representing more than 60% of total inorganic P (TIP) content in sediments. Although no significant variation of TIP contents was observed, the proportion of bioavailable P in TIP pools decreased after the rainy season. The concentrations of individual inorganic P fractions ($NH_4Cl-P$, $NH_4F-P$, NaOH-P, and $H_2SO_4-P$) were significantly different across sites and after the rainy season (p < 0.05, two-way ANOVA). $NH_4F-P$ and NaOH-P concentrations in sediments increased in a downstream direction. After the rainy season, $NH_4Cl-P$ concentrations in sediments decreased whereas $NH_4F-P$ and $H_2SO_4-P$ concentrations increased. The redistribution of individual P fractions in sediments observed after rainy seasons were possibly due to the changing contribution of various sources of runoff and the variation in flow related particle size. Current estimation of P in bed sediments of the South Han River suggests a lower potential of internal P loading from sediments after the rainy season.