• Journal of Korea Water Resources Association
• /
• v.49 no.5
• /
• pp.391-398
• /
• 2016

The confluence section of rivers forms complex flow pattern due to inflow discharge variation at the mainstream and tributary. Due to complex flow characteristics, bed change and bank erosion at the local section produce lateral geomorphology changes in rivers. In this study, bankline change by bank erosion and bed change were simulated using CCHE2D of 2-dimensional numerical model for quantitative analysis of lateral changes in the confluence section of South Han River and Geumdang Stream. As a result, bankline at the left-side channel of the mainstream was largely changed in the downstream section of the confluence compared to the upstream section. Also, bank erosion in the tributary was hardly occurred and bankline at the left-side tributary and right-side main stream moved to riverside land due to decreased velocity and deposition.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.12
• /
• pp.659-667
• /
• 2017

This study analyzes the changes in the flow characteristics due to the difference in inflow discharges from the main channel and tributary at the confluence of the Nakdong and Geumho Rivers. The analysis was done using a two-dimensional numerical method. The study site has complicated flow patterns because of the discharge variation from the main stream and tributary. The study section has a meandering main channel, and the hydraulic characteristics cannot be defined with simple conditions such as the confluence angle of the channels or the ratio of the channel widths. An actual flood event in 2012 was applied in the numerical simulation. The maximum velocity occurred in the meandering section after passing the confluence, where a rapid change was expected. A high velocity and large bed change in this section were observed in the simulation results. The variation of discharges from the main channel and tributary was a more dominant factor in the flow and bed changes for the normal flow conditions than the flood event. This indicates that countermeasures for channel stabilization should be considered in the meandering section downstream of the confluence section, and countermeasures for the study section should be investigated.

• Journal of Korea Water Resources Association
• /
• v.56 no.2
• /
• pp.103-113
• /
• 2023

The river confluence is a section in which two rivers with different topographical and hyrodynamic characteristics are combined into one, and it is a section in which rapid flow, inflow of sediments, and hydrological topographic changes occur. In the confluence section, the flow of fluid occurs due to the difference in density due to the type of material or temperature difference, which is called a density flow. It is necessary to accurately measure and observe the confluence section including a certain section of the main stream and tributaries in order to understand the mixing behavior of the water body caused by the density difference. A comprehensive analysis of this water mixture can be obtained by obtaining flow field and flow rate information, but there is a limit to understanding the mixing of water bodies with different physical properties and water quality characteristics of rivers flowing with stratigraphic flow. Therefore, this study attempts to grasp the density flow through the water temperature distribution in the confluence section. Among the extensive data of the river, vertical data and water surface data were acquired, and through this, the stratification phenomenon of the confluence was to be confirmed. It was intended to analyze the mixed pattern of the confluence by analyzing the water mixing pattern according to the water temperature difference using the vertical data obtained by measuring the repair volume by installing the ADCP on the side of the boat and measuring the real-time concentration using YSI. This study can supplement the analysis results of the existing water quality measurement in two dimensions. Based on the comparative analysis, it will be used to investigate the current status of stratified sections in the water layer and identify the mixing characteristics of the downstream section of the river.

• Journal of Korea Water Resources Association
• /
• v.31 no.5
• /
• pp.529-538
• /
• 1998

The flow configurations at open channel junctions are analyzed by 2-D depth averaged mathematical model. The governing factors of the flow at the junction are found to be discharge ratio between tributary flow and the post confluence combined flow, and confluence angle. Analyzed by these two factors are flow patterns and flow depth variation at the confluence, discharge ratio above which the flow upstresm from the junction is affected by the tributary flow and the geometries of a recirculation region. Further, the flow contraction in the downstream region and the deflection of the tributary flow in the main channel were investigated. The numerical results are compared with the existing experimental data fairly well.

• Journal of Wetlands Research
• /
• v.16 no.1
• /
• pp.139-151
• /
• 2014

In this study, virtual confluence of $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$ type flowing into main channel was designed to comprehend occlusion phenomenon of the mouth of river, then performed numerical analysis using the RMA-2 and SED2D model of SMS according to application of 40m, 60m, 80m, 100m Training levee corresponding to main channel width ratio. Results of simulations analysis are summarized as follows. Applying appropriate Training levee length determined by numerical analysis results, Training levee dimension for occlusion reduction was studied through the analysis of velocity, water level, bed variation at the Gamchen confluence and Wichen confluence.

• Journal of The Geomorphological Association of Korea
• /
• v.27 no.2
• /
• pp.29-46
• /
• 2020

In this study, changes in the fluvial landforms of the Yeoju section of the Han River, which was made up of the Han River Restoration Project, were examined through existing previous research data, government's environmental impact assessment data, satellite images, and field observations. For example, In the vicinity of Dori Island, the most upstream part of the study section, the location of the confluence of the Han River and Cheongmi Stream was changed, and it was found that a significant portion of the sand sedimentary layer disappeared. In the Bawuinupgubi area, the wetland, which is the first class in the ecological nature, was greatly modified, and the elevation of the ground rose as Gangcheon island and it was completely separated from the river by dredging The confluence of Geumdangcheon and the point bar of Yeonyang-ri in the south were also dredged, turned into an artificial waterfront park, and a chute channel remained in the form of a wetland was also developed as a recreational park. The deposional forms around Baekseok-ri islands also disappeared as dredging was carried out. Among the areas adjacent to the confluence of Bokcheon and Yangchon-ri Island, some sedimentay forms remains, but the abandonned channel between Yangchon-ri and the northern river bank has been changed into a riverside reservoir through dredging and embankment construction, and the waterway of the tributary river(Yazoo) has been greatly changed.

• Ecology and Resilient Infrastructure
• /
• v.6 no.4
• /
• pp.328-338
• /
• 2019

This paper presents the numerical simulations of future river bed changes using CCHE2D, a two-dimensional numerical model, for river confluences at the confluences of the Nakdong River and Gamcheon as well as Geum River and Mihocheon. The numerical simulations of future river bed changes were conducted for three years using hydrological data from August 30, 2012, to August 29, 2015 after the Four Major River Restoration Project. The simulation results demonstrated that river bed changes occurred actively near the confluence where sediment deposition was concentrated, resulting in the possibility of point bar formation. Through the numerical simulations, the characteristics of future river bed change was evaluated by investigating the characteristics of bed changes, average bed elevation changes, and the difference between deposition and erosion in the target section. The two-dimensional numerical model is expected to be used in the future to prepare effective stabilization plans for the tributary confluence.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.49 no.5
• /
• pp.11-20
• /
• 2007

In this study, we reviewed the optimal space for the fishway and fish storage establishment in the section between the downstream of the Hwacheon dam and the confluence of the Pungsan river. The hydraulic stability of these facilities was also examined. In the section between the downstream of Hwacheon dam and the confluence of Pungsan river, the release flow of Hwacheon dam was set at $5,495m^3/s,\;6,110m^3/s$ and $7,537m^3/s$, and numerical simulations were executed for each instance using the HEC-RAS model and RMA-2. In the analysis of the flow velocity distributions in the subject section by release flows of Hwacheon dam, it was shown that there was over 5.0m/s of high flow velocity at Sta. $#1{\sim}Sta.$ #3, Sta. $#4{\sim}Sta.$ #6, and Sta. $#12{\sim}Sta.$ #13 of the sections analyzed in this study. The Sta. $#0{\sim}Sta.$ #1 was considered appropriate for the fishway and fish storage establishment. As seen in the results of the numerical stability review by release flow conditions of Hwacheon dam subject to the selected available areas fur fishway and fish storage, the topographically available section for the establishment of fishway and fish storage exists at Sta. $#1{\sim}Sta.$ #3 when the release flow of Hwacheon dam is $5,495m^3/s$, whereas Sta. $#0{\sim}Sta.$ #1 should be reviewed for the subject section for the establishment of fishway at release flows of $6,110m^3/s$ and $7,537m^3/s$, in addition to the figures gathered at the $5,495m^3/s$ release flow. Finally, the available section for the establishment of fishway and fish storage was determined to be Sta. $#0{\sim}Sta.$ #3. Further, if fishway and fish storage are established in the outer bank within this section, the high flow velocity section should be avoided. An alternative would be to establish for the fishway in the inner band on the section of Sta. #1 or Sta. #3.

• Journal of Korean Society on Water Environment
• /
• v.33 no.6
• /
• pp.640-649
• /
• 2017

The purpose of this study is the analysis of the water quality spatial characteristics for the main stream of Nakdong River in consideration of the tributary inflow. The flow and water quality (BOD, TOC, TP) data for 32 monitoring stations located in the main stream and the tributaries of Nakdong River were collected from 2003 to 2016. From the results of the flow and water quality analyses for each site, a status map of the flow and the water quality for Nakdong River was produced. The water quality of each river section was classified according to seven river-environment standards. The water quality changes in the main stream before and after the confluence were analyzed spatially. As a result, the water quality of Kumho River, in particular the Kumho B to Kumho C section, is the worst among the tributaries. In addition, the water quality grades of the lower streams such as Nam River and Miryang are worse than that of the upper streams of the Nakdong River. In the case of the main stream, the water quality grades of the sections between the Wicheon and Nam River confluences and the section from Nakbon L to Nakbon N are relatively poor.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.2
• /
• pp.911-918
• /
• 2013

Two - dimensional numerical analysis model(RMA2), is mainly applied to analyze the flood water levels, velocities and change of river bed at the downstream of Dam. The analysis result be able to influence to Gwangchon bridge from Juam dam, freeboard be insufficient 0.7m to left bank 300m section of dam downstream. Bank overflow is appear to all section of Bosung river to PMF spill condition. Inundated district is appear to river confluence to 200year frequency and is expand to bank overflow to PMF spill condition. Velocity in the channel was simulated high velocity to the bridge and narrow reach and appear to riverbed degradation.