• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.2
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• pp.125-135
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• 2005

Generation and transport of nonpoint source pollution, especially sediment-associated pollutants, are profoundly influenced by hydrologic features of runoff. In order to identify pollutant export rates, hence, clear knowledge of rainfall-runoff relationship is a pre-requisition. In this study, performance of AnnAGNPS model was assessed based on the ability of the model to predict rainfall-runoff relationship. Three catchments, each under different nearly single land use, were simulated. From the results, it was found that the model was likely to produce better predictions for larger catchments than smaller catchments. Because of using the daily time scale, the model could not account for short durations less than 24 hours, especially high intensity events with multiple peak flow that significantly contribute to the generation and transport of pollutants. Since CN information for regional areas has not been built up, a careful selection of CN is needed to achieve accurate prediction of runoff volume. Storm distribution also found to be considered as an important calibration parameter for the hydrologic simulation.

• Journal of the Korean Geosynthetics Society
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• v.7 no.4
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• pp.9-18
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• 2008

Shallow slope failures in residual soil during periods of prolonged infiltration are common in Korea. This study examines an infinite slope analysis to estimate the influence of infiltration on surficial stability of slopes by the limit equilibrium method. Approximate method which is based on the Green-Ampt model have been considered to evaluate the likelihood of shallow slope failure which is induced by a particular rainfall event that accounts for the rainfall intensity and duration for various return periods. Pradel & Raad method which is devised to predict the depth of wetting front to decomposed granite soil slopes having measured soil-water characteristic curves. To compare the results with those obtained from the Pradel & Raad method, a series of numerical analysis using SEEP/W were carried out. It was found that the stability analysis of unsaturated soils calculated by using the soil-water characteristic curve of decomposed granite soils was found to be a proper analysis for shallow slope failures due to rainfall.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.89-99
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• 2012

An upland monitoring was conducted for about 4 years with respect to the water and quality of rainfall-runoff. The objective was to characterize of runoff and nonpoint source (NPS) pollution from a sandy field with 4.5 % in slope under balloonflower (2008-2010) and potato (2011) cultivation. Balloonflower was cultivated without any surface cover but potato was grown under plastic mulching. Runoff rate, EMCs and NPS pollution loads were estimated. The first flush effect was evaluated, and the correlation coefficient among the selected water quality indices were analyzed. Average rainfall size was higher by 2.3 mm when balloonflower was cultivated but average runoff rate was higher by 0.02 when potato was cultivated due to the plastic mulching. EMCs monitored from balloonflower field were higher than potato field except SS and TN, but all NPS pollution loads of potato field were 2.1~22.9 times greater than balloonflower field because of larger runoff volume. As a result of first flush effects, balloonflower and potato field were more influenced by increasing of accumulated rainfall and rainfall intensity rather than first flush. In the result of correlation analysis, there were no evident correlations between runoff and water quality indices. However, there were obvious correlations between SS and the other indices except TN. As a result of this study, it was thought that perennial balloonflower crop could help reduce runoff and NPS pollution loads but annual crop with plastic mulching increase them.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4B
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• pp.347-359
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• 2010

A simple web-based flood forecasting system using data from stage and rainfall monitoring stations was developed to solve the difficulty that real-time forecasting model could not get the reliabilities because of assumption of future rainfall duration and intensity. The regression model in this research could forecast future water level of maximum 2 hours after using data from stage and rainfall monitoring stations in Daejeon area. Real time stage and rainfall data were transformed from web-sites of Geum River Flood Control Office & Han River Flood Control Office based MS-Excel 2007. It showed stable forecasts by its maximum standard deviation of 5 cm, means of 1~4 cm and most of improved coefficient of determinations were over 0.95. It showed also more researches about the stationarity of watershed and time-series approach are necessary.

• Journal of Korea Water Resources Association
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• v.39 no.1 s.162
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• pp.47-57
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• 2006

This study derives an event-based tank model with a conceptual rainfall-infiltration process, modifying conventional tank models. The model comprises two serial tanks, one parallel tank and an infiltration regulating element. The infiltration process within the element is not represented as a function of only time, but as a function of soil moisture content for three possible cases owing to the relationship between rainfall intensity and infiltration capacity. This study considers the previous soil moisture condition of a watershed by using antecedent precipitation index. Six parameters of the model are identified by using the real coded genetic algorithm. The applicability and validity of the proposed model are assessed for the observed stormwater data from the research basin of the International Hydrological Program, the Pyeongchanggang River basin, Republic of Korea. The results computed streamflows show relatively good agreement with observed ones.

• The Korean Journal of Applied Statistics
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• v.12 no.1
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• pp.125-141
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• 1999

서로 다른 위치에서 동시에 관찰된 자료들이 공간적인 변인에 의하여 영향을 받는다면 공간적인 변인의 함수식에 의한 예측모형을 설정하는 것이 타당하다. 본 연구에서는 공간적인 변인으로 거리가 주어졌을 때, 공간자료에 대한 세미베리오그램 모형의 추정과 관측되지 않은 지점에 대한 공간예측기법을 정리하였으며, 또한 공간이상치 탐지를 위한 두가지 방법론으로 분포론적 방법과 p-Deletion 방법을 제시하였다. 방법론의 예시를 위하여 강우강도 자료를 이용하였으며 서로 상관되어 있는 공간데이터에 대한 시뮬레이션을 통하여 두가지 방법을 비교하였다.

• Journal of Korea Water Resources Association
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• v.38 no.9 s.158
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• pp.699-711
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• 2005

In this study, the U.S. Geological Survey's DR3M-II(Distributed Routing Rainfall-Runoff Model) was applied for small urban drainage. DR3M-II is a watershed model for routing storm runoff through a branched system of pipes and natural channels using rainfall input. The model was calibrated and verified using short term rainfall-runoff data collected from Sanbon basin. Also, the parameters were optimized using Rosenbrock technic. An estimated simulation error for peak discharge was about 7.4 percent and the result was quite acceptable. Results of the sensitivity analysis indicate that the percent of effective impervious area and ${\alpha}$ defining surface slope and roughness were the most sensitive variables affecting runoff volumes and peak discharge for low and high intensity storm respectively. In most cases, soil moisture accounting and infiltration parameters are the variables that give more effects to runoff volumes than peak discharge. Parameter ${\alpha}$ showed the opposite result.

• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.49-55
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• 2016

Field measurement units and a system were constructed and installed in a waste-dump slope at the Imgi mine to investigate and analyze the variations in the unsaturated characteristics of the soil. The field instrumentation system was composed of a data acquisition system (DAS), a solar system, and measuring sensors. The rainfall, matric suction, and volumetric water contents were continuously measured from the units in the instrumented site. The variations in matric suction and volumetric water content were primarily affected by the rainfall intensity. At the surface of the slope, the largest increase and decrease in the changes in matric suction and volumetric water content were observed during the wetting and drying processes, respectively. Also, the matric suction and volumetric water content were 5-35 kPa and 0.12-0.24, respectively. However, the ground water level was not suddenly increased just after rainfall but gradually increased after 2 or 3 days later.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.4
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• pp.59-72
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• 1987

Although long-term runoff analysis is important as much as flood analysis in the design of water works, the technological level of the former is relatively lower than that of the latter. In this respect, the precise estimation model for the volume of successive runoff should he developed as soon as possible. Up to now, in Korea, Gajiyama's formula has been widely used in long-term runoff analysis, which has many problems in applying in real situation. On the other hand, in flood analysis, unit hydrograph method has been exclusively used. Therefore, this study aims at trying to apply unit hydrograph method in long-term runoff analysis for the betterment of its estimation. Four test catchment areas were selected ; Maesan area in Namlum river as a representative area of Han river system, Cheongju area in Musim river as one of Geum river system, Hwasun area in Hwasun river as one of Yongsan river system, and Supyung area in Geum river as one of Nakdong river system. In the analysis of unit hydrograph, seperation of effective rainfall was carried out firstly. Considering that effective rainfall and moisture condition of catchrnent area are inside and outside of a phenomenon respectively and the latter is not considered in the analysis, Initial base flow(qb)was selected as an index of moisture condition. At the same time, basic equation(Eq.7) was established, in which qb can take a role as a parameter in relating between cumulative rainfall(P) and cumulative loss of rainfall(Ld). Based on the above equation, computer program for estimation model of qbwas seperately developed according to the range of qb, Developed model was applied to measured hydrographs and hyetographs for total 10 years in 4 test areas and effective rainfall was estimated. Estimation precision of model was checked as shown in Tab- 6 and Fig.8. In the next stage, based on the estimated effective rainfall(R) and runoff(Qd), a runoff distribution ratio was calculated for each teat area using by computerised least square method and used in making unit hydrographs in each test area. Significance of induced hydrographs was tested by checking the relative errors between estimated and measured runoff volume(Tab-9, 10). According to the results, runoff estimation error by unit hydrograph itself was merely 2 or 3 %, but other 2 or 3 % of error proved to be transferred error in the seperation of effective rainfall. In this study, special attentioning point is that, in spite of different river systems and forest conditions of test areas, standardized unit hydrographs for them have very similar curve shape, which can be explained by having similar catchinent characteristics such as stream length, catchinent area, slope, and vegetation intensity. That fact should be treated as important factor ingeneralization of unit hydrograph method.

• Journal of the Korean Geographical Society
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• v.41 no.4 s.115
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• pp.418-434
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• 2006

The study was investigated to runoff characteristics of non-point pollutants according to rainfall in Kokseong river watershed. The result of which is as follows : First of all, major reason which affect the formation of water quality of Kokseong River is judged to be caused by non-point pollution source which flows out from farmland and residential area. Flow of rainfall effluent in the downstream in which direct flow components of urban district and combined sewer overflows of farmland was intervened faster than that in the upstream reacted more promptly. Generation of pollutants by non-point source shows increasing trend in general in accordance with the increase in the intensity of rainfall but it was affected by SS, BOD, COD and T-P in the upstream part whereas BOD, COD and T-N were significantly affected by beginning period of rainfall in the downstream. EMC in the downstream increased approximately 3-315 times as compared to upstream, particularly the discharge of SS5 and T-P were extremely increased. While surface flow out of rainfall effluent in the upstream was only 4.7%, the surface flow in the downstream took up as much as 29%, which was major reason for the increase of EMC. From the above contents, we can see that the change in water quality according to the increase and decrease of effluent at the time of rainfall showed very complex pattern depending on the type of land use, and it is judged that the most important thing for the administration of non-point pollution source is to come up with the solution for the reduction of effluent at the beginning.