• Journal of Korea Water Resources Association
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• v.48 no.6
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• pp.479-489
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• 2015

The objective of this study is to develop the equations for concentration time and storage coefficient considering regional trend in urban stream watershed for reliable hydrological analysis. The 13 basins located in Jungrang, Tan, Anyang, and Hongje stream are selected for the data collection and formula development in this study. The stepwise multiple-regression analysis is used for the development considering watershed, urban, and precipitation characteristic indices. The developed formulae are compared with the domestic and foreign empirical formulae and evaluated the accuracy in urban stream area. It shows the computed value from the equation developed in this study is more accurate than those from other empirical formulae. The error sum, average error and RMSE of computed values from the developed equations in this study are the lowest. The formulae considering the regional trend of urban stream watershed are worth in terms of showing better results than the domestic and foreign empirical formulae. It can be concluded the developed formulae can be useful in urban stream watershed.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.109-113
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• 2005

도시하천유역에서 집중호우에 따른 제방 범람과 이에 따른 침수 피해범위를 해석하기 위하여 우리나라의 대표적 도시하천인 중랑천 시험유역에서의 하천의 홍수 및 제방붕괴 특성 분석을 중심으로 연구하였다. 이를 위하여 100년, 200년, PMF의 빈도별 강우 조건에서 홍수량을 각각 산정하였고, 제방붕괴조건별 하천의 부정류 해석 및 제내지의 홍수범람해석을 실시하였다. 제방붕괴의 조건으로서 붕괴시간(10, 30, 60분), 붕괴폭(10, 20, 30m) 및 제방붕괴위치(중상류부, 중류부, 중하류부) 등에 따른 홍수위, 월류량 및 제내지 침수 수위 변화 등을 검토하였다. 홍수규모와 제방붕괴 양상 및 위치에 따른 월류량 및 제내지에서의 침수 범위를 각각 계산하고 비교 검토한 결과, 제방붕괴의 위치 및 붕괴폭이 홍수범람규모와 침수피해에 큰 영향을 주는 것으로 분석되었다.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.6
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• pp.412-420
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• 2014

Water quality variations were investigated at 4 locations of Jungrang river (upper, middle and lower basins) during a period of 3 rainfall events. During the rainfall, concentrations of $COD_{Mn}$, SS and $BOD_5$ significantly increased, while the concentration of T-N decreased and that of T-P remained relatively constant. This pattern became more apparent as the level of accumulative precipitation and rainfall intensity increased. Simple regression analysis showed that the accumulative precipitation was positively correlated with all water quality pollutants except for T-N. With increasing accumulative precipitation, the concentration of T-N decreased, while the others increased. $R^2$ of simple regressions of hourly average rainfall intensity and water quality pollutants, showed wider range of variation ranged from 0.483 to 0.992, which indicated a strong correlation. The stronger the hourly average rainfall intensity, the more T-N and T-P in the upper basin, more $COD_{Mn}$ in the middle and lower basins, more SS with gradual increase from upper to lower areas, and more $BOD_5$ with gradual decrease from upper to lower region. Simple regression showed that water quality pollution in the upper basin was more sensitive to an increase of rainfall discharge than that in the middle and lower areas.

• Korean Journal of Environment and Ecology
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• v.37 no.2
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• pp.140-150
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• 2023

The Eurasian otter (Lutra lutra) is an apex predator of the riparian ecosystem. It is a keystone and an indicator species; consequently, its presence suggests a sustainable water environment. Otter is a keystone species as a predator at the top of the food web in the aquatic environment and an indicator species representing the health of the aquatic environment. Although Eurasian otters disappeared from the Han River urban water system because of anthropogenic activities like habitat destruction, poaching, and environmental pollution in the 1980s, the species were sighted in the Cheonggye Stream, Jungrang Stream, and Seongnae Stream, which are urban sections of the Han River, in 2016 and 2021. Therefore, it is pertinent to assess the habitat potential in the area for conservation and management measures to ensure its permanent presence. However, existing studies on otter habitats focused on natural rivers and reservoirs, and there is a limit to applying them to habitats artificially confined habitats in narrow spaces such as tributaries in urban areas of the Han River. This study selected the Cheonggye Stream, an artificially restored urban stream, to evaluate its potential as a habitat for Eurasian otters in urban water environments using the habitat suitability index (HSI). The HSI was calculated with selected environment attributes, such as the cover, food, and threat, that best describe the L. lutra habitat. According to the results, the confluence area of Seongbuk Stream and Cheonggye Stream and the confluence area of Cheonggye Stream and Jungnang Stream were suitable otter habitats, requiring appropriate conservation efforts. The HSI model suggests a valuable method to assess the habitat quality of Eurasian otters in urban water environments. The study is crucial as it can help rehabilitate the species' populations by identifying and managing potential Eurasian otter habitats in highly urbanized areas of the Han River basin and its tributaries.

• Analytical Science and Technology
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• v.5 no.2
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• pp.159-167
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• 1992

An improved and accurate method for the determination of linear alkybenzene sulfonate(LAS) in river water is described by using gas chromatography and GC/MS. The gas chromatograph equipped with BP-5 capillary column was satisfactory for isolation of the homologues and isomers of LAS in river water. Four LAS homologues, $C_{10}$, $C_{11}$, $C_{12}$, $C_{13}$ alkyl chains were determined in Jungrang stream, Jinwi stream and down stream of Han river tributary. Especially $5-C_{11}$, $6-C_{11}$, $2-C_{12}$ and $6-C_{13}$, $7-C_{13}$ of LAS were identified by mass chromatogram. Different composition of LAS in standard and river water expressed the distribution and fate of LAS in river water. The remarkable reduced content of $C_{12}$ and $C_{13}$ in river water implied that the biodegradation of LAS more easily occured in longer alkylchain one. This method would be applicable for determination of LAS in water with high resolution and sensitivity.

• Korean Journal of Ecology and Environment
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• v.45 no.4
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• pp.378-391
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• 2012

The objective of this study was to determine temporal patterns and longitudinal gradients of water chemistry at eight artificial reservoirs and ten streams within the Han-River watershed along the main axis of the headwaters to the downstreams during 2009~2010. Also, we evaluated chemical relations and their variations among major trophic variables such as total nitrogen (TN), total phosphorus (TP), and chlorophyll-a (CHL-a) and determined intense summer monsoon and annual precipitation effects on algal growth using empirical regression model. Stream water quality of TN, TP, and other parameters degradated toward the downstreams, and especially was largely impacted by point-sources of wastewater disposal plants near Jungrang Stream. In contrast, summer river runoff and rainwater improved the stream water quality of TP, TN, and ionic contents, measured as conductivity (EC) in the downstream reach. Empirical linear regression models of log-transformed CHL-a against log-transformed TN, TP, and TN : TP mass ratios in five reservoirs indicated that the variation of TP accounted 33.8% ($R^2$=0.338, p<0.001, slope=0.710) in the variation of CHL and the variation of TN accounted only 21.4% ($R^2$=0.214, p<0.001) in the CHL-a. Overall, our study suggests that, primary productions, estimated as CHL-a, were more determined by ambient phosphorus loading rather than nitrogen in the lentic systems of artificial reservoirs, and the stream water quality as lotic ecosystems were more influenced by a point-source locations of tributary streams and intense seasonal rainfall rather than a presence of artificial dam reservoirs along the main axis of the watershed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1B
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• pp.9-20
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• 2012

Recently to overcome limitations of conceptual, hydrological and physics based models for flood stage forecasting, multiple linear regression model as one of data-driven models have been widely adopted for forecasting flood streamflow(stage). The objectives of this study are to compare performance of different multiple linear regression models according to regression coefficient estimation methods and determine most effective multiple linear regression flood stage forecasting models. To do this, the time scale was determined through the autocorrelation analysis of input data and different flood stage forecasting models developed using regression coefficient estimation methods such as LS(least square), WLS(weighted least square), SPW(stepwise) was applied to flood events in Jungrang stream. To evaluate performance of established models, fours statistical indices were used, namely; Root mean square error(RMSE), Nash Sutcliffe efficiency coefficient (NSEC), mean absolute error (MAE), adjusted coefficient of determination($R^{*2}$). The results show that the flood stage forecasting model using SPW(stepwise) parameter estimation can carry out the river flood stage prediction better in comparison with others, and the flood stage forecasting model using LS(least square) parameter estimation is also found to be slightly better than the flood stage forecasting model using WLS(weighted least square) parameter estimation.

• 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.41 no.2
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• pp.185-196
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• 2008

The flash flood has been studied in the climatological aspect which considers temporal and spatial characteristics of rainfall. However, we have not interested in runoff hydrograph for flash flood study. Therefore, our objectives of this study are to apply a work of Bhaskar et. al (2000) which studied runoff hydrograph to represent the flash flood to Korea and also to distinguish flash flood event from general flood event. That is, we quantified the severity of flash flood by estimation of flash flood index using runoff hydrograph. This study estimated the flash flood index for investigating the relative severity of flash flood in Han river basin with 101 flood events. Also we quantified the flash flood severity for flood event by heavy rainfall occurred in July of 2006. As a result, Kangwon-do province showed more severe flash flood than other areas in Han river basin and urban area such as Jungrang cheon stream also showed severe flash flood. We analyzed a flash flood of July of 2006 by dividing July into 1st to 3rd terms. From the analysis we knew that the 1st term of July showed the severe flash flood was occurred in Seoul area and the 2nd term showed it was occurred in Kangwon-do province.