• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1184-1188
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• 2005

The impacts of turbidity flow induced by summer rainfall events on water supply, aquatic ecosystems, and socioeconomics are significant and major concerns in most of reservoirs operations. As a decision support tool, the real-time turbidity flow monitoring and modeling system RTMMS is under development using a laterally integrated two-dimensional (2D) hydrodynamic and water quality model. The objectives of this paper is to present the preliminary field observation results on the characteristics of rainfall-induced turbidity flows and their density flow regimes, and the model performance in replicating the fate and transport of turbidity plume in a reservoir. The rainfall-induced turbidity flows caused significant drop of river water temperature by 5 to $10^{\circ}C$ and resulted in density differences of 1.2 to $2.6kg/m^3$ between inflow water and ambient reservoir water, which consequently led development of density flows such as plunge flow and interflow in the reservoir. The 2D model was set up for the reservoir. and applied to simulate the temperature stratification, density flow regimes, and temporal and spatial turbidity distributions during flood season of 2004 After intensive refinements on grid resolutions , the model showed efficient and satisfactory performance in simulating the observed reservoir thermal stratification and turbidity profiles that all are essentially required to enhance the performance of RTMMS.

• Journal of Environmental Impact Assessment
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• v.15 no.6
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• pp.435-441
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• 2006

For the calibration of rainfall-runoff model, automatic calibration methods are used instead of manual calibration to obtain the reliable modeling results. When mathematical programming techniques such as linear programming and nonlinear programming are applied, there is a possibility to arrive at the local optimum. To solve this problem, genetic algorithm is introduced in this study. It is very simple and easy to understand but also applicable to any complicated mathematical problem, and it can find out the global optimum solution effectively. The objective of this study is to develope a parameter optimization program that integrate a genetic algorithm and a rainfall-runoff model. The program can calibrate the various parameters related to the runoff process automatically. As a rainfall-runoff model, SWMM is applied. The automatic calibration program developed in this study is applied to the Jangcheon watershed flowing into the Youngrang Lake that is in the eutrophic state. Runoff surveys were carried out for two storm events on the Jangcheon watershed. The peak flow and runoff volume estimated by the calibrated model with the survey data shows good agreement with the observed values.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.877-882
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• 2010

This paper is a result of investigating causes and main characteristics of landslides, occurred at Hongcheon area in Gangwondo during July in 2006, by collecting relevant data and visiting site. The main cause of landslides in this area has been found to be saturation of the ground wetted by a series of precipitations during 10~13 July and the heavy rainfall during 15 July. The pattern of the landslides could be classified as translational failure, occurred at the boundary between the relatively thin weathered residual soil and the mother rock. By analyzing a number of failed slopes based on site visit and reviewing collected data, typical widths of failed slopes are in the range of 10~20m (minimum: 5m, maximum: 70m). Lengths of landslide area are in the wide range of 10~450m. Most of area are less than 20m in width and 100m in length so that their shapes are long and narrow, frequently observed in Korea, and their areas are relatively small size of around $1000m^2$. The inclinations of the failed slopes are in the range of $10{\sim}60^{\circ}$ while the most probable slope angle is about $20{\sim}25^{\circ}$.

• Spatial Information Research
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• v.10 no.2
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• pp.275-287
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• 2002

Rainfall-Runoff Analysis in Whangryong River Basin was made using HEC-HMS and HEC-GeoHMS. The Basin was divided into three sub-basins using HEC-CeoHMS and GIS. Then, GIS input data were derived from each sub-basins. SCS CN runoff-volume model, Snyder's UH direct-runoff model, exponential recession baseflow model and Muskingum routing model in HEC-HMS were used to simulate the runoff volume using selected rainfall event and the parameters were optimized. Peak flowrate calculated using optimized parameters was compared to the observed flowrate in the basin. The result proved to be good agreement with each other. Optimized parameters in this local basin can be used to calculate the peak flowrate in the future.

• Journal of Environmental Science International
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• v.20 no.3
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• pp.417-426
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• 2011

This study was conducted to investigate runoff characteristics of non-point pollutants source at the urban and rural zones in sangju area. The monitoring was conducted with seven events for ten months and Event mean Concentration(EMC) and First Flush Effect(FFE) of SS and BOD were calculated on the result of the water quality parameters. During rainfall event, the peak concentrations of SS and BOD were observed after 3~4 hours of rainfall in rural areas. Whereas, the peak concentrations occurred within 1~2 hours after rainfall and then the highest concentration of NPS pollutants sharply decreased, showing strong first flush effect in urban areas. The cumulative load curves for NPS pollutants showed above the $45^{\circ}$ straight line, indicating that fist flush effect occurred in urban areas. The mean SS EMC values of rural areas ranged from 0.9~3.3mg/L, it was higher value when compare to urban areas. While the mean BOD values of urban areas were shown the highest values.

• Water for future
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• v.25 no.4
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• pp.109-119
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• 1992

The purpose of this study is to develop real-time streamflow forecasting models in order to manage effectively the flood warning system and water resources during the storm. The stochastic system models of the rainfall-runoff process using in this study are constituted and applied the Recursive Least Square and the Instrumental Variable-Approximate Maximum Likelihood algorithm which can estimate recursively the optimal parameters of the model. Also, in order to improve the performance of streamflow forecasting, initial values of the model parameter and covariance matrix of parameter estimate errors were evaluated by using the observed historical data of the hourly rainfall-runoff, and the accuracy and applicability of the models developed in this study were examined by the analysis of the I-step ahead streamflow forecasts.

• Water Engineering Research
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• v.1 no.3
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• pp.223-231
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• 2000

The purpose of this study is the development of a system for estimating non-point sources pollutant loads from a watershed, which enables users to get insights of pollutant load distribution in the watershed during rain as well. Based on the Geographic Information System, this non-point source pollutant loading estimation system(NSPLES) consists of three distinct models such as a distributed rainfall-runoff model, a soil loss and delivery model, and a non-point source pollutant model. It also includes GIS modules for preprocessing the input data for the models and graphical postprocessing of the model outputs. The system output aren't only the hydrograph, sedimentograph, and pollutograph at the watershed outlet, but also various maps that show the distribution of soil loss over the watershed. The developed system was applied to the two upper stream areas of Sumjin river basin, Ssangchi and Gwanchon basins, and three rainfall events for respective subbasins during 1992 and 1998 were selected for the system application. The results of this showed relatively higher corelation between observed data and simulated data, and proved the applicability of the system.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.120-125
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• 2000

This study analyzes agricultural water demand nationwide which calculated by the estimation system for agricultural water demand(ESAD) with the data are observed in the other Studies. The results are as follows. Maximum, minimum and average values of annual evapotranspiration in paddy in 1,767 boundaries covering all the country are estimated as 819.2mm, 595.2mm and 702.9mm respectively. In the case of transplant seeding, the annual effective rainfall is estimated as 834.7mm to 464.3mm, while the average is 635.3mm. The amount of effective rainfall is largest in case of transplant seedlings and then come watered direct seeding and dry direct seeding regardless of region. Maximum, minimum and average values of annual evapotranspiration in upland in 1,767 boundaries are estimated as 659.97mm, 129.3mm and 411.8mm respectively. The annual effective rainfall is estimated as 607.2mm to 68.3mm while the average is 257.4mm. infiltration ratio in paddy in 1,767 boundaries applied in ESAD is 5.06mm/day in average, varying from 12.0mm/day to 2.0mm/day. Applied conveyance loss is 12.8% in average, varying from 18.0% to 8.0%.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.2
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• pp.67-74
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• 2002

The purpose of this study was to investigate the effects of ponding depth treatment on water balance in paddy fields. Three ponding depth treatments, very shallow, shallow, and deep were used. The experimental plots were three 80m $\times$ 8m rectangular plots. Daily values of rainfall amount, ponding depth, irrigation water, drainage water, evapotranspiration, and infiltration were measured in the field. The ponding depth was continuously observed by water level logger during the growing season. The ET was measured by 1-m diameter PVC lysimeters. Irrigation water volume was measured by 75 mm pipe flowmeters and the drainage water volume by 75 mm pipe flowmeters and a recording Parshall flume. The results showed that irrigation water depths were 688.9 mm, 513.6 mm, and 624.4 mm in very shallow, shallow, and deep ponding, respectively. The effective rainfall amounts (effective ratio) were 243.7 mm(48.8%), 344.6 mm(68.9%), and 272.9 mm(54.6%) in very shallow, shallow, and deep ponding, respectively. The three treatments did not show any statistical difference in growth and yields. But the shallow depth treatment showed the largest yield.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.214-214
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• 2015

Rainfall induced landslides is one of the most devastating natural disasters acting on mountainous areas. In Korea, landslide damage areas increase significantly from 1990s to 2000s due to the increase of both rainfall intensity and rainy days in addition with haphazard land development. This study was carried out based on the application of TRIGRS unsaturated (Transient Rainfall Infiltration and Grid-based Regional Slope stability analysis), a Fortran coded, physically based, and numerical model that can predict landslides for areas where are prone to shallow precipitation. Using TRIGRS combining with the geographic information system (GIS) framework, the landslide incident happened on 27th, July 2011 in Mt. Umyeon in Seoul was modeled. The predicted results which were raster maps showed values of the factors of safety on every pixel at different time steps show a strong agreement with to the observed actual landslide scars in both time and locations. Although some limitations of the program are still needed to be further improved, some soil data as well as landslide information are lack; TRIGRS is proved to be a powerful tool for shallow landslide susceptibility zonation especially in great areas where the input geotechnical and hydraulic data for simulation is not fully available.