• Journal of Korean Society of Water and Wastewater
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• v.24 no.4
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• pp.377-386
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• 2010

To identify operating parameters of the up-flow filtering system, which is available to discharge filtering residue after the rain, developed for treatment of urban storm runoff, lab scale test was carried out. Removal efficiency of SS was 68.7%, 62.2%, and 58.6% at the area roading rate of 2.46m/h, 4.68m/h, and 10m/h, respectively, filtering device is desirable to operate at the lower than 4.68m/h of area roading rate to get higher level of 60% SS removal efficiency. The removal efficiency of SS was 57.1% ~ 68.7% at the raw water SS of 100mg/L ~ 600mg/L, and the SS in treated water was maintained at the constant level through the elapsed time. It is indicate that filtering device can guarantee a certain level of effluent water quality at various raw water quality. The removal efficiency of SS to the depth of filter media was 68.3%, 78.6% at the filter depth of 10 cm, 20cm respectively. The final treated water quality was showed 30.2mg/L of CODMn, 1.60mg/L of TN and 0.25mg/L of TP. The average removal efficiencies by filtering device developed in this research were recorded slightly lower levels than other research. The main reason of these results were the first, the filter depth of the media used in this test was shallow, the second, the kind of filter media in discharge port of residue. More research to kind of filter media, filter packing rate, select of media for residue discharge port should be go on to produce optimum operating condition. The result of this study would be valuable for the application of filtration device to control of urban storm water.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.391-398
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• 2011

This study is to develop highly efficient coagulation system(HECS) that runs treatment with a short retention time to cover the overflow in the rain, which coagulation, mixing and settling are contacted in a single reactor and to estimate the applicability. Setting up 100ton/day-size pilot scale plant, the results of continuous operation in case of runoff, maintaining 20 minute-retention time at optimum chemical injection condition(Alum 100mg/L, Polymer 1.0mg/L) shows the highest removal efficiency(Turbidity 93.1%, TCODcr 80.6%, BOD 81.8%, SS 92.5%, TN 72.3% and T-P 87.3%). It was estimated that the large amount of cost for separate sewage system and the size of area for system instruction can be reduced if the HECS is applied for CSOs treatment because the HECS is so compact and quickly. When we see the results, HECS from this study could be able to treat the pollutant quickly within a short retention time only with coagulant and polymer, which could show high applicability.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.949-957
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• 2011

This aim of study was to investigate the characteristics of discharge of pollutants as well as the correlation between flow rate and water quality constituents in a combined sewer system according to the characteristics of rainfall. For the loading rates for each pollutant, the median concentrations of all pollutants except T-N was increased when a CSO took place. The loading rates of BOD, COD, SS, T-N, T-P, Cu and Zn at the CSOs were 328-1255, 25-129, 83-2009, 4-12, 14-51, 5-11 and 5-13 times higher than the DWF (Dry Whether Flow), respectively. Especially, SS loading rate was found to be highest in all pollutants. On the other hand, the range of the first flush coefficient, b for water quality constituents such as BOD, COD, SS, T-N, T-P, Cu and Zn were 0.537-0.878, 0.589-0.888, 0.516-1.062, 0.852-1.031, 0.649-0.954, 0.975-1.015 and 0.900-1.114, respectively. In term of correlation between flow rate and pollutant concentrations, SS concentration was highly correlated to flow rate. However, there was an inverse correlation between EC (Electrical Conductivity) and flow rate because of the high dilution of flow rate. In case of correlation between pollutants, there was a high correlation between SS and T-P.

• Journal of Forest and Environmental Science
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• v.29 no.4
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• pp.314-323
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• 2013

To examine surface erosion and sediment export patterns on a hillslope, which was devastated by a shallow landslide and which was slowly revegetating by natural plant species, we surveyed variations in surface erosion depth on the upper-, middle- and lower-section of the hillslope, and subsequent sediment yield from the whole hillslope. The result showed that, with the passing of year, surface erosion on the devastated hillslope was regulated by higher rainfall intensity due to the supply-limitation of exportable sediment, and its variation range decreased. In addition, surface erosion on the upper-section with steep slope was regulated by higher rainfall intensity, which might result in raindrop erosion, compared to it on the lower-section with relatively gentle slope. Besides, the sediment yield from the devastated hillslope had nonlinear relationship with surface erosion depth on the hillslope because sediments on the hillslope are exported downwards while repeating their cycle of transport and redistribution. Our findings suggest the establishment of management strategy to prevent sediment-related disasters occurred during torrential rainfall events, which was based on the continuous field investigation on the hillslope devastated by landslides.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.439-449
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• 2016

The methodology of synthetic unit hydrograph using geomorphic characteristics was suggested. Six geomorphic components over 19 watersheds were used to estimate synthetic unit hydrograph and the test watersheds were classified into two groups on the basis of the area of $200km^2$. The regression formulas between standardized geomorphic characteristics for each group and peak quantities of specific streamflow and time of representative unit hydrograph were suggested and the Nash and the Clark unit hydrographs were derived. For verifying the derived unit hydrographs, the resulting hydrographs were compared with the ones using the existing Clark unit hydrographs based on the empirical parameter estimation for the 145 storm events during 2010 to 2011 for the additional six watersheds. The results showed the relatively higher performance over the existing synthetic unit hydrograph methods, which could be a contribution to the hydrologic estimation in ungauged watersheds.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.975-985
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• 2013

In this research, the integrated modeling system by coupling of a watershed model, a reservoir model, and a river model has been constructed in Doam reservoir watershed. Because of domestic climate characteristics, it is inevitable to construct the dam for control of flood, water use, and power production due to the heavy rain in the summer. Especially, when the dam is constructed on the stream for these kinds of purpose, it is necessary to consider this region as one watershed and also to make the integrated system for simulation and management. In this study, SWAT model was constructed for watershed modeling and EFDC-WASP model was constructed for simulating the hydrodynamic and water quality of the reservoir and the downstream in Doam dam watershed. Also, the water quality improvement equipment for demonstration was applied in the upstream part of Doam reservoir, which shows the applicability of the developed integrated modeling system.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.252-252
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• 2011

Rainfall-runoff models are calibrated and validated by using a same data set such as observations. The past climate change effects the present rainfall pattern and also will effect on the future. To predict rainfall-runoff more preciously we have to consider the climate change pattern in the past, present and the future time. Thus, in this study, the climate change represents changes in mean precipitation and standard deviation in different patterns. In some river basins, there is no enough length of data for the analysis. Therefore, we have to generate the synthetic data using proper distribution for calculation of precipitation based on the observed data. In this study, Kajiyama model is used to analyze the runoff in the dry and the wet period, separately. Mean and standard deviation are used for generating precipitation from the gamma distribution. Twenty hypothetical scenarios are considered to show the climate change conditions. The mean precipitation are changed by -20%, -10%, 0%, +10% and +20% for the data generation with keeping the standard deviation constant in the wet and the dry period respectively. Similarly, the standard deviations of precipitation are changed by -20%, -10%, 0%, +10% and +20% keeping the mean value of precipitation constant for the wet and the dry period sequentially. In the wet period, when the standard deviation value varies then the mean NSE ratio is more fluctuate rather than the dry period. On the other hand, the mean NSE ratio in some extent is more fluctuate in the wet period and sometimes in the dry period, if the mean value of precipitation varies while keeping the standard deviation constant.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.385-385
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• 2011

유역 스케일의 실제 증발산량을 산정하는 대표적인 방법으로 관측 강우량과 유출량의 관계로부터 증발산량을 간접적으로 추정하는 물수지(water balance)법, 증발력과 토양수분량의 변화량 (soil moisture accounting)을 고려한 유역 수문모델링을 이용하는 방법, 잠재 증발산량과 실제 증발산량간 보완관계식(complementary relationship)을 이용하는 방법 등이 있다. 물수지법은 관측치를 기반으로 한다는 점에서 신뢰도가 높다고 할 수 있으나, 기본적으로 유역 저류량의 변화를 무시하기 때문에 연 단위와 같이 긴 시간 스케일에 적용 가능하고 작은 시간 스케일에는 적용성이 떨어진다. 유역 수문모델링을 이용하는 방법은 기상, 토양 및 식물 조건을 모두 고려하는 방법으로 유역의 불균질성을 반영할 수 있고 일 단위 등의 비교적 작은 시간 스케일에 대해서도 증발산량을 산정할 수 있는 장점이 있으나, 수많은 입력자료가 필요하며 간접적인 추정 방식이기 때문에 모형의 정확한 검증과 상당한 숙련도가 뒷받침되어야 한다. 잠재 증발산량과 실제 증발산량간 보완관계식을 이용하는 방법은 토양이나 식물 등의 지표면 조건에 대한 정보를 필요로 하지 않으며 단지 기상자료만을 이용하는 방법으로 적용하기 쉽다는 장점이 있으나 잠재 및 실제 증발산량간의 보완피드벡 매카니즘이 존재한다는 가정이 수반되어 있어 적용시 이를 입증해야 하는 어려움이 있다. 이 처럼 각기 장단점을 가진 여러 방법으로 증발산량을 산정하고 있지만, 각 방법 간의 연결고리를 맺는 연구는 심도 있게 수행되지 못하고 있다. 따라서 본 연구에서는 상기 언급한 증발산량 산정 방법 중 보완관계식을 이용하는 방법과 유역수문모형에 의한 방법 간의 연관성을 평가하고자 하였으며, 이를 위해 충주댐 상류유역에 대해서 SWAT-K에 의한 증발산량 모의치가 보완관계식을 따르는 지에 대해 고찰하였다. 모의기간동안 계산된 잠재 및 실제 증발산량을 습윤지수(humidity index)에 따라 함께 도시해본 결과, 연 단위의 경우에는 건조할수록 잠재 증발산량은 점차 커지고 실제 증발산량은 작아지는 것으로 나타나 보완관계가 성립하였고, 월 단위 경우에는 강우에 비해서 비교적 증발산량이 큰 5, 6월에 가장 명확한 관계가 보여 늦은 봄과 초여름에 보완적 관계가 뚜렷하게 발생하는 반면에 동절기에는 보완관계가 성립하지 않는 것으로 나타나는 등 분석 단위기간별로 보완관계의 성립여부를 판별할 수 있었다.

• Journal of Korea Water Resources Association
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• v.44 no.12
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• pp.967-974
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• 2011

Based on daily time series from RDAPS numerical weather forecast, Streamflow prediction was simulated and the result of ESP analysis was implemented considering quantitative mid- and long-term forecast to compare the results and review applicability. The result of ESP, ESP considering quantitative weather forecast, and flow forecast from RDAPS numerical weather forecast were compared and analyzed with average observed streamflow in Guem River Basin. Through this process, the improvement effect per method was estimated. The result of ESP considering weather information was satisfactory relatively based on long-term flow forecast simulation result. Discrepancy ratio analysis for estimating accuracy of probability forecast had similar result. It is expected to simulate more accurate flow forecast for RDAPS numerical weather forecast with improved daily scenario including time resolution, which is able to accumulate 3 hours rainfall or continuous simulation estimation.

• Water for future
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• v.27 no.2
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• pp.147-154
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• 1994

The occurrence condition of debris fiow due to rainfall is given by solving the equations for fiow on a slope. The solution shows that a debris fiow will occur on a slope when the accumulated rainfall within the time of concentration exceeds a certain value determined by the properties of the slope. To estimate this critical value, the system analysis technique would be commendable. In this study, a procedure to fine the critical rainfall from the rainfall data whith and without debris flows is proposed. Reliability of this method is verified by applying to the debris flows in Unzen Volcano which recently began to erupt. Discharge of debris flow in a stream is obtained by solving the equation of continuity using the kinematic wave theory and assuming the cross sectional area to be a function of discharge. The computed hydrographs agree weel with the ones observed at the rivers in Sakurajima and Unzen Volcanos. It is found from the derived equation that the runoff intensity of debris flow is in proportion to the rainfall intensity and accumulated rainfall, jointly. This gives a theoretical basis to the conventional method which has been widely used.