• Journal of Korean Society on Water Environment
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• v.24 no.4
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• pp.442-451
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• 2008

We analyzed characteristics of rainfall-runoff for the channel of Yongwon area made by a new port construction. And we conducted inundation analysis on the region of lower elevation near the coast. SWMM5 was calibrated with the storm produced by the typhoon Megi from August 19 to August 20 in 2004, and was verified with the storm from August 22 to August 22 in 2004. We performed hydraulic channel routing of Yongwon channel about typhoon Megi from August 19 to August 20 in 2004 by UNET model which is a hydraulic channel routing. The simulated runoff hydrographs were added to the new stream as lateral inflow hydrographs and a watershed runoff hydrograph was the upstream boundary condition. The downstream boundary condition data were estimated by the measured stage hydrographs. The maximum stage that was calculated by hydraulic channel routing was higher than the levee of inundated region in typhoon Megi. Thus we can suppose an inundation to have been occurred. We performed inundation analysis about typhoon Megi from August 19 to August 20 in 2004 and flood discharge of return period 10~150 years. And we estimated each inundation area. The inundation areas by return periods of storms were estimated by 3.4~5.7 ha. The causes of inundation are low heights of levee crests (D.L. 2.033~2.583 m), storm surges induced by typhoons and reverse flow through the coastal sewers (D.L. -0.217~0.783 m). A result of this study can apply to establish countermeasure of a flood disaster in Yongwon.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3270-3278
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• 2014

Many researches has been conducted as extreme rainfall in hydrology and extreme rainfall analysis is not proper for determination of CSOs treatment capacity. In this study, runoff is calculated by tranformation from rainfall to runoff according to Interevent Time Definition. The capacity of sewage treatment plant is designed by 3 times of DWF(Dry Weather Flow) and the efficiency of present sewage treatment plant is very low becauseat at present. Also, The sewage treatment plant can not control CSOs. In this research, the pollution load is calculated by EMC(Event Mean Concentration) and pollution concetration of total runoff is a standard deciding suitablility of present sewage treatment plant. Finally, CSOs treatment capacity is determinated considering pollution load.

• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.409-417
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• 2012

SWAT model was applied for the Nakdong River Basin to characterize water quality variability and assess the feasibility of using the load duration curve to water quality management. The basin was divided into 67 sub-basins considering various watershed environment, and rainfall runoff and pollutant loading were simulated based on 6 year measurements of meteo-hydrological data, discharge data of treatment plants, and water quality data (SS, T-N and T-P). The results demonstrate that non-point source loads during wet season increase by 80 ~ 95% of total loads. Although the rate of water flow governs the amount of SS that is transported to the main streams, nutrient concentrations are highly elevated during dry season by being concentrated. This phenomenon is more pronounced in the lower basin, receiving large amounts of urban point source discharges such as treated sewages. Also, the load duration curves (LDC) demonstrate dominant source problems based on the load exceedances, showing that SS concentrations are associated with the rainy season and nutrients, such as T-P, may be more concentrated at low flow and more diluted at higher flow. Overall, the LDC method could be used conveniently to assess watershed characteristics and pollutant loads in watershed scale.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.18-18
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• 2012

In Japan, about 67% of the land is covered by forests and about 41% of them consist of plantations. About 35% of the plantations consist of old-aged plantations of older than 50 yearsand the percentage is projected to 67% in ten years' time. Although the trees of these plantations are supposed to be cut for timber production, most of them remain unmanaged and thus overcrowded mainly due to declining domestic forest industry. Since the forests are mostly located in headwater watershed, there are growing concerns about the degradation of water resources by these unmanaged plantations. To understand the ecohydrological processes in these plantations and examine the effect of intensive 50-60 % thinning to increase infiltration rate and reduce overland flow and soil erosion by recovering understory vegetation, the JST-CREST project "Development of Innovative Technologies for Increasing in Watershed Runoff and Improving River Environment by the Management Practice of Devastated Forest Plantation (Representative: Yuichi Onda)" has been launched since 2009. The ultimate objective of this project is to provide potential scenario to enhance low flow discharge in drought period and reduce turbid material in high flow period. We have been conductingintensive field observation campaign in five research sites across Japan. In Fukuoka site, integrated ecohydrological observations have been conductedin two contrastive watersheds since 2010. Intensive 50% thinning was conducted from January to April 2012 and comparative studies of ecohydrological processes before and after thinning have been started. The interim results from all the sites of this project will be presented in the 3rd International Congress for Forest and Water in a Changing Environment held in Fukuoka during 18-20 September, 2012 (http://www.forest.kyushu-u.ac.jp/~ecohydrol/3ForestWater/index.html).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.404-411
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• 2019

In this study, the HEC-HMS was applied to determine rainfall-runoff processes for the Gokgyuchun basin. Several sub-basins have large-scale reservoirs for agricultural needs and they store large amounts of initial runoff. Three infiltration methods were implemented to reflect the effect of initial loss by reservoirs: 'SCS-CN'(Scheme I), 'SCS-CN' with simple surface method(Scheme II), and 'Initial and Constant rate'(Scheme III). Modeling processes include incorporating three different methods for loss due to infiltration, Clark's UH model for transformation, exponential recession model for baseflow, and Muskingum model for channel routing. The parameters were calibrated using an optimization technique with trial and error method. Performance measures, such as NSE, RAR, and PBIAS, were adopted to aid in the calibration processes. The model performance for those methods was evaluated at Gangcheong station, which is the outlet of study site. Good accuracy in predicting runoff volume and peak flow, and peak time was obtained using the Scheme II and III, considering the initial loss, whereas Scheme I showed low reliability for storms. Scheme III did not show good matches between observed and simulated values for storms with multi peaks. Conclusively, Scheme II provided better results for both single and multi-peak storms. The results of this study can provide a useful tool for decision makers to determine master plans for regional flood control management.

• Journal of Korea Water Resources Association
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• v.57 no.4
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• pp.289-300
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• 2024

The purpose of this study is to evaluate the applicability of the GRM (Grid based rainfall-Runoff Model) to the continuous simulation by simulating the dam inflow. The GRM was previously developed for the simulation of rainfall-runoff events but has recently been improved to enable continuous simulation. The target watersheds are Chungju dam, Andong dam, Yongdam dam, and Sumjingang dam basins, and runoff models were constructed with the spatial resolution of 500 m × 500 m. The simulation period is 21 years (2001 to 2021). The simulation results were evaluated over the 17 year period (2005 to 2021), and were divided into three data periods: total duration, wet season (June to September), and dry season (October to May), and compared with the observed daily inflow of each dam. Nash-Sutcliffe efficiency (NSE), Kling-Gupta efficiency (KGE), correlation coefficient (CC), and total volume error (VE) were used to evaluate the fitness of the simulation results. As a result of evaluating the simulated dam inflow, the observed data could be well reproduced in the total duration and wet season, and the dry season also showed good simulation results considering the uncertainty of low-flow data. As a result of the study, it was found that the continuous simulation technique of the GRM model was properly implemented and the model was sufficiently applicable to the simulation of dam inflow in this study.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.79-87
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• 2017

In this paper, for 43 sites neighboring to western area of Gangwondo where disaster of debris flow occurred from 2006 to 2013, magnitude of debris flow was estimated from results of site investigation and correlation analysis between influencing factors to its magnitude was performed. Magnitude of channelized debris flow was found greater by 6.5 times of that of hill slope debris flow and approximately 5% of total volume was occurred at initiation part of channelized debris flow. As results of analyzing yield rate of debris flow, for channelized debris flow, yield rate values of $19m^3/m$ and $8m^3/m$ were obtained for total volume being over $10,000m^3/m$ as the large scale of debris flow and less than $10,000m^3/m$ respectively, and value of $5m^3/m$ was estimated for hill slope debris flow. As results of correlation analysis of influencing factors to magnitude of debris flow, runoff distance and erosion width were very highly correlated to its magnitude whereas average slope of basin and erosion depth showed relatively low correlation. In particular, value of erosion depth was in the range of 0.5-2.6 m, being similar range to the value proposed by Ikeya (1981). Triggering rainfall to debris flow such as continuous rainfall and maximum intensity of hour rainfall were analyzed to have low correlation with magnitude of debris flow.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.283-286
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• 2007

현재까지 이수관리를 목적으로 저수지 또는 저수지군의 최적(연계)운영모형 개발에 관한 연구들을 다수 수행한 바 있는데 그 예를 들면, 한강, 금강, 낙동강 수계에서 Hydro-scheduling 모형과 CoMOM(Coordinated Multi- reservoir Operating Model for Han River Basin)을 적용하였고 특히 낙동강 수계에 대해서는 저수관리시스템을 개발하여 적용하였다. 그러나 이러한 적용 사례에도 불구하고 이수 물관리의 근간이 되는 수계 저수유출을 모의할 수 있는 모형은 정립되어 있지 못한 실정이다. 본 연구에서는 수계별 한정된 수자원의 효율적 관리를 위한 기존댐의 연계운영과 병행하여 댐 상 ${\cdot}$ 하류 유출을 고려한 종합적인 수자원관리방안 수립의 필요성이 대두됨에 따라, 저수기 램 상 ${\cdot}$ 하류의 수계 주요지점에 대한 하천유출상황을 모의할 수 있는 모형을 개발하였다.

• Journal of Korean Society of Disaster and Security
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• v.15 no.1
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• pp.1-12
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• 2022

An automatic optimization technique is used to estimate the optimal parameters of the hydrologic model, and different hydrologic response results can be provided depending on objective functions. In this study, the parameters of the event-based rainfall-runoff model were estimated using various objective functions, the reproducibility of the hydrograph according to the objective functions was evaluated, and appropriate objective functions were proposed. As the rainfall-runoff model, the storage function model(SFM), which is a lumped hydrologic model used for runoff simulation in the current Korean flood forecasting system, was selected. In order to evaluate the reproducibility of the hydrograph for each objective function, 9 rainfall events were selected for the Cheoncheon basin, which is the upstream basin of Yongdam Dam, and widely-used 7 objective functions were selected for parameter estimation of the SFM for each rainfall event. Then, the reproducibility of the simulated hydrograph using the optimal parameter sets based on the different objective functions was analyzed. As a result, RMSE, NSE, and RSR, which include the error square term in the objective function, showed the highest accuracy for all rainfall events except for Event 7. In addition, in the case of PBIAS and VE, which include an error term compared to the observed flow, it also showed relatively stable reproducibility of the hydrograph. However, in the case of MIA, which adjusts parameters sensitive to high flow and low flow simultaneously, the hydrograph reproducibility performance was found to be very low.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.63-71
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• 2018

The particle filtration mechanisms in an infiltration trench should be varying due to the different hydraulic conditions during stormwater runoff. The understanding of these variations associated with different filtration mechanisms and their effect on the particle removal efficiency is of vital importance. Therefore, a LID (Low Impact Development) system comprising of an infiltration trench packed with gravel and woodchip was investigated during the monitoring of several independent rainfall events. A typical rainfall event was divided into separate regimes and their corresponding flow conditions as well as filtration mechanisms in the trench were analyzed. According to hydraulic conditions, it was found out that filtration changes between vertical and horizontal flows as well as between unsaturated, saturated, and partially-saturated flows. Particle separation efficiency was high (55-76%) and was mainly governed by physical straining during the unsaturated period. It was then enhanced by diffusion during the saturated period (75-95%). When the trench became partially saturated at the end of the rainfall event, the efficiency decreased which was believed to be due to the existence of a negatively charged air-water interface which limited the removal to positively charged particles.