• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.65-71
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• 2007

In this research, we made a one and two-dimensional analysis of numerical data collected from the bend curvature of a bended river section. According to the result from the numerical analysis, the inflow & output angle caused a water level deviation which increased with an increase of the flood discharge. From the water level deviation of our two-dimensional numerical model, we obtained the maximum slope of 6,67% when the inflow and output angle was 105 degrees and the flood discharge was 500 CMS. As for the right side, the differences with the one-dimensional numerical model were reduced when the angle was more than $90^{\circ}$. As for the left side the differences were reduced when the angle was more than $105^{\circ}$. For a river with more than 90 degrees bend curvature, a hydraulic experiment would be more appropriate than a numerical analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1441-1449
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• 2015

At the bends of a river, the deflected flow of high energy erodes the embankment and transports sediment, ultimately changing the river's course. Such phenomena lead to instability of the embankment and may cause serious problems for nearby roads, land, or riverside structures. This study intends to analyze the characteristics of hydraulic flow at S-shaped bends after the installation of Riprap Weirs designed to prevent changes in a river's course and embankment erosion. An experimental channel was constructed by a two-dimensional CCHE2D model, and analyzed the characteristics of hydraulic flow with and without the Riprap Weirs. Also, the characteristics of hydraulic flow at the inner and outer sides of river bends and at points near reservoirs were analyzed, depending on the intervals between the Riprap Weirs.

• Journal of Korea Water Resources Association
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• v.30 no.5
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• pp.477-485
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• 1997

Recent internal and external bridge failures due to pier and abutment scour have emphasized the need for better methods of scour depth estimation. This paper compares the hydraulic analysis of the Namhan River Bridge over the Namhan River using one-dimensional models. WSPRO & HEC-2, and the two-dimensional model. TABS-MD based on the procedures presented in HEC-18 published by the U.S. FEdral Highway Administration. A comparison of estimated scour depth for this research based on the results from both one-dimensional and two-dimensional model is presented. At the same time, field measurement has been performed before and after flood using sounding instrument. Fathometer (DE-719C). A comparison between estimated and measured scour depth at bridge is also presented. Result shows that there is all the difference between estimated and measured scour depth due to dissimilarity between laboratory and field conditions. Also, it is difficult to measure the maximum scour depth accurately due to refilling. Therefore development of scour measuring equipment which can be used during peak flood, and derivation of empirical model appropriate for internal river system seems urgent.

• Journal of Korea Water Resources Association
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• v.32 no.1
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• pp.61-70
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• 1999

The two-dimensional Random-Walk model in which fluid and pollutant particles are tracked using statistical concept was developed to simulate dispersion processes in natural streams. The calibration of the model shows that the error decreases as the number of grid increases, and/or the number of particles in each grid increases. The proposed model is tested against the dispersion data collected in the Grand River, Canada. The simulation results show that the 2-D Random-Walk model describes two-dimensional mixing phenomena occurred in the irregular meandering stream very accurately.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.31-43
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• 1989

Tidal asymmetry and the associated sediment dynamics in the Keum River Estuary has been investigated from a numerical tidal model. Modeling efforts were focussed on the simulation of large drying sandflat exposed at the mouth of the Estuary and dynamic combination of two-dimensional estuary model and one-dimensional river model. Despite strong frictional attenuation within the estuary, the M4 tides reach significant amplitude, resulting in strong tidal distortion. Model results show that the asymmetry over the area exhibit more intense flood flows transport than do less intense ebb flows of longer duration. This causes filling of the estuary as evidenced by large sandflats spread over the inner area. The spatial distribution of peak bottom stress computed from the tidal model suggest that present tidal sedimentation regime may be altered significantly, especially in the approach channel to outer Kunsan port and downstream part of the dike, due to the construction of cross-channel barrier.

• Korean Journal of Hydrosciences
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• v.10
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• pp.59-72
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• 1999

FIAS(Flood Inundation Analysis System) using Arc/Info is developed and applied to the Namhan River basin. The DWOPER model is revised and expanded to handle simultaneous multiple overtopping and/or breaking, and to estimate the inundated depth and extents. The model is applied to an actual levee overtopping case, which occurred on August 23∼27, 1995 in the Namhan River. Stage hydrographs inside and outside of the levee are compared, then inundated discharges from overbank spilling are computed. The Graphic User interface is developed with AML. Two- and three-dimensional inundation map by Arc/Info are presented. The computed inundation extends agree with observations in terms of inundated depth and flooded area. The FIAS is useful for the analysis of flood hazards and preparation of inundation map for river basins.

• Journal of Korea Water Resources Association
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• v.30 no.4
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• pp.401-409
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• 1997

This study aims to predict the bed elevation change of river and reservoir by compound water model, two-dimensional jet model and one-dimensional density current model, assuming that the river has a single channel and the reservoir has multiple channels. In numerical model, discharge and water level changes is obtained by flow continuity equation and flow momentum equation through double-sweep method, and then applied to sediment continuity equation to predict the scour and deposit of channel bed. The span ranged from the Bosung Dam to Mundueok Bridge at the upstream of Juam Dam, which is approximately 31km long (13km of river and 18km of reservoir), is taken as survey area.

• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.693-701
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• 2002

In this study, one dimensional sediment movement numerical model(HEC-6) and semi-two dimensional sediment movement numerical model(GSTARS 2.1) were applied to solve the change of channel geometry in Bocheong stream. GSTARS 2.1 model was applied for the three selected sediment transport formulas(Ackers and White's, Engelund and Hanson, Yang formula) from 1993 to 2000 measured data on each section. The simulation results of Ackers and White formula for long -term bed changes are good when compared to the measured data. The HEC-6 model was applied for the simulation of one dimensional sediment movement for the same period. Comparison of the long-term simulations by GSTARS 2.1 and HEC-6 models with measured data shows that simulations by both models are in fair agreement with measured data in overall trend of the river bed changes. Comparisons of simulated cross sectional bed-elevations with measured data shows that GSTARS 2.1 model gives better agreement with than simulated results bed changes on the HEC-6 model.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1273-1284
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• 2018

The flow and bed change were analyzed using the CCHE2D model, which is a two-dimensional numerical model, at a confluence of the Namhan River and Seom River where deposition occurs predominantly after the "Four Major Rivers Restoration Project." The characteristic of the junction is that the tributary of Seom River joined into the curved channel of the main reach of the Namhan River. The CCHE2D model analyzes the non-equilibrium sediment transport, and the adaptation lengths for the bed load and suspended load are important variables in the model. At the target area, the adaptation length for the bed load showed the greatest influence on the river bed change. Numerical simulation results demonstrated that the discharge ratio ($Q_r$) change affected the flow and bed change in the Namhan River and Seom river junction. When $Q_r{\leq}2.5$, the flow velocity of the main reach increased before confluence, thereby reducing the flow separation zone and decreasing the deposition inside the junction. When $Q_r$>2.5, there was a high possibility that deposition would be increased, thereby forming sand bar. Numerical simulation showed that a fixed sand bar has been formed at the junction due to the change of discharge ratio, which occurred in 2013.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.2
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• pp.127-133
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• 1999

The MOSU model, a depth-averaged two-dimensional sediment transport model, is applied to simulate the bed level changes before and after dock construction in Daemyung site. The model is a semi¬coupled finite difference model that can be applied to a river, a reservoir, a lake, estuaries, or coastal regions, The model is able to simulate the transport of fine sand, silt, and clay. The model parameters are estimated by qualitative calibration. A prediction result of the numerical model shows that the bed level changes due to dock construction are little.