There are advantages in installing weirs in the river channels. These include easy water intake, controlling the water level and the back flow of the tide. However, weirs hinder the natural flow coming from the upper stream. Flow rate drops the sediment transport capacity by reducing the velocity. The analogy is drawn from the upstream results in the destabilization of the river bed being deposited in the upper section. Thus;, it adversely affects the functional side of the beam and can be the cause of various problems such as environmental pollution. Sejong weir was installed in Geum River through the Multi-functional Administrative City due to the four-river restoration project. The upstream section of Sejong weir which operates near the right bank of the small hydropower plants due to sediment accumulation were hindering the sluice operations. The quantitative prediction and problem analysis of the river bed changes and review of the stabilization plan of the river bed is therefore required.
In this study, the river bed changes in the upstream of the Sejong weir, the middle and the downstream of the Geum River in the flood zone about 600m away were analyzed. An evaluation of the applicability of the numerical model in the study area through the comparison of the actual and calculated results. Also, the evaluated numerical model was used in predicting the riverbed variations of the study area. The appropriate hydrological management plan for the proposed changes and the problems caused by the bed hydrological operations based on scenarios were also evaluated.
As a result, the quantitative aspects of the simulated results and the riverbed fluctuation Changes in SED-2D model shows a similar trend with the measured results by the bed, and the bed cross-section measurement variability. Therefore the use of SED-2D model was found to be highly-applicable. Sejong-weir was built one year after, the sediment deposited is 169,263㎥ and for the Sejong-weir built five years later is 164,652.0㎥, Sejong-weir built 10 years after the sediment has been deposited is 63,713.5㎥. Riverbed variation due to operating hydrological operations is 154,740.0㎥ when right-side gate is opened, 149,023.0㎥ during central gate opened, 163,841.0㎥ during left-side gate is opened, and 63,713.5㎥ when all gates were opened. Therefore, all gates opened was analyzed for minimization of sediment deposits.