• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.721-729
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• 1997

Total scour depth at a bridge is comprised of three components: long-term changes, contraction scour and local scour. Therefore, the analysis of long-term bed elevation changes is very important in the estimation of total scour depth at bridge sites. In this research, long-term bed elevation changes at the Namhan River Bridge are analysed using CHARIMA and HEC-6 models. The results show that, for 5-year steady normal stream flow, the bed elevation is aggreded by 45cm for CHARIMA model but degraded by 5cm for HEC-6 model. For 5-year unsteady flow, the bed elevation is changed greatly and it has a great influence on the estimation of total scour depth. Therefore, to make a proper estimation of total scour depth, not only contraction scour and local scour, but also long-term bed elevation changes should be estimated precisely.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.394-398
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• 2016

Numerical analysis was conducted using Delft3D developed by Deltares in Netherlands to predict long-term river bed changes in Saemangeum Area. Tidal flow, discharge through the drainage gates and river bed changes in numerical model was verified by comparing to the results of field observation and hydraulic experiments. We calculated long-term river bed changes in Saemangeum area for 10 years from 2031 to 2040 after completion of development in Saemangeum. It is shown that 70 cm and 139 cm of accumulation occur in estuaries of Dongjin River and Mankyong River, respectively. Variation of flood level was also investigated considering long-term river bed changes. There was no change in estuary of Dongjin River but maximum flood level in estuary of Mankyong River increased 81 cm.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.297-300
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• 2002

Semi-two dimension numerical models were applied to study on the hydraulic and sedimentologic characteristics of upstream and downstream channel section in Dal stream. The feature of this paper is (1) to analyse the effects of bed changes by sediment transport formulas, (2) to analyse the effects of bed changes by stream tube. The simulation results of Meyer-peter and Muller formula for long-term bed changes are good when compared to the measured data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.7089-7097
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• 2015

Bed changes in the Nakdong River were analyzed with long-term monitoring data for analyzing riverbed change patterns after Four Major Rivers Restoration Project (FMRRP). Also, possible long-term bed changes were predicted using one-dimensional numerical model for the section where the largest change was observed after FMRRP. The sensitive analysis was performed with different incoming sediment discharge conditions and sediment transport equations. The numerical model was calibrated by comparing short-term monitoring data and simulated results, and was applied for predicting bed change after 10 years. As a result of monitoring data analysis, the largest change in bed elevation occurred at the section between the Changnyeong-Haman and Hapcheon-Changnyeong weirs. The result of one-dimensional numerical modeling for 10 years indicated that maximum depositions of 2.07 m and 3.26 m were produced in this section.

• Proceedings of the Korea Water Resources Association Conference
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• 2002.05b
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• pp.817-822
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• 2002

• Spatial Information Research
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• v.21 no.5
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• pp.1-6
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• 2013

Trying to estimate variations of the riverbed is basic and important for river management. When new dam constructed in upstream and a structure were planned, impact of the riverbed changes in downstream should be considered for stably maintained and sustained rivers in the future. In this study, long-term riverbed changes analyzed using aerial photographs in Naeseongcheon. Also applying one-dimensional numerical model, GSTARS analyzed the effects of bed deformation in critical points. Based on Changing Patterns of long-term riverbed, it is possible that after the dam was built, to explore how to manage Naeseongcheon.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.103-108
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• 2008

Riverbed change is greatly influenced by artificial factors such as dam construction, gravel collection, and river improvement. This study simulated a long-term bed change based on the GSTARS3 model using actual data from the area downstream of the Geum River Daecheong Dam and compared the estimation with a section of the actual measurement. As a result, it was found that the section of the actual measurement was far lower than the result of the simulation in terms of long-term bed change. While the area downstream of Daecheong Dam displayed approximately an average of 2.29 m of streambed degradation on average while the upper stream area showed approximately 0.63 m of bed degradation over 24 years. In the simulation of the area downstream of Daecheong Dam based on the GSTARS3 model, similar bed degradation was observed. However, a great difference was detected between the result and the actual measurement. According to the cause analysis, the riverbed in the area downstream of Daecheong Dam has continuously degraded due to the dam construction and mass collection of gravel. The mass collection of gravel was the main cause of riverbed change. It was found that about 76% of all riverbed degradation was caused by the mass collection of gravel.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1B
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• pp.1-7
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• 2012

Quasi-two dimensional numerical model (GSTARS) was applied to determine the optimal sediment discharge formula for simulating the sedimentologic characteristics of Hyeongsan river. The field measurements have been conducted to obtain the data, such as sediment discharge, bed material, and channel geometry, for model calibration and verification. The sediment discharge formulas, which have been generally used, have been assessed according to the average error, relative error, RMSE, RRMSE, discrepancy ratio and Nash-Sutcliffe efficiency coefficient for bed changes along the thalweg. From the results, Laursen formula(1958) shows the best performance to simulate the long-term bed change of Hyeongsan river.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.139-147
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• 2008

More precise estimation of the bed change, primary cause of flood damage, has been recognized significant for designs of levees and other river facilities. In this study, the long-term bed change was examined as the application of the relatively new Surface-water Modeling System (SMS) Model because there has not been broad verification of the model empirically on river of South Korea. This 2-dimensional model was used to examine the bed change of Pochon Stream Basin, a tributary of Imjin River, where heavy rain damages annually occur. First, in order to verify the model, the simulating period was set from 1986 to 1998 because of the existence of the field measurements. Cross sectional field measurements of 1986 were used for the initial condition and output were compared and analyzed with the observed cross sectional data in 1998. As the results of the verification, the comparison in lateral and streamwise bed level between results from the model and the field measurements showed a reasonable agreement except for the some cases of local scours. However, in terms of the quantitative comparison, the change of the bed elevations for each cross section for 1998 was rather underestimated than that of the field measurements.