• Title/Summary/Keyword: River Bed Change

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Analysis of Hydraulic Characteristics using SMS RMA2 and SED2D Model in the Downstream of Gyeongan-Cheon (SMS를 이용한 경안천 하류구간의 하천흐름 분석)

  • Hong, Seong-Min;Jung, In-Kyun;Kim, Seong-Joon
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2003.10a
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    • pp.519-522
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    • 2003
  • The purpose of this study is to analyze various hydraulic characteristics using SMS (Surface Water Modelling System) RMA2 model. It is based on 2-D finite element method. River reaches (13.8km) from Gyeongan gauge station to the inlet of Paldang lake was selected. Finite element was made by RIMGIS Data, and the analysis of river-changes was operated by unsteady flow. The sediment concentration and bed change was simulated using SED2D model.

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The estimation of water level fluctuation in the down stream water mark by water level fluctuation in the upper region water mark (상류지점 수위표 수위변동에 따른 하류지점 수위표 수위변동예측)

  • Choi, Han-Kuy;Lim, Yoon-Soo;Baek, Hyo-Seon
    • Journal of Industrial Technology
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    • v.30 no.B
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    • pp.83-89
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    • 2010
  • Generally, the accuracy of the prediction of flood elevation is difficult to identify due to the sedimentation on a river bed, earth and sand being moved by flow, and localized torrential downpours caused by climate change. It is also because of natural and artificial influences on rivers. To predict river floodings successfully, more precise and reliable flood elevation prediction system is needed, in which the concentration time of downstream is numerically interpreted through analyzing and utilizing the watermark of the upper region. Therefore, this research analyzed the prediction methods of the changes in water levels, which use the watermarks of the upper region. The watermarks which impacts the spot being predicted of flood was selected through floodgate analysis and correlation analysis. With the selected watermarks, a statistically reliable regression equation was yielded.

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Characteristics of Fish Community Structure before the Dam Operation in the Naeseong Stream, Korea (내성천에서 영주댐 운영전 어류 군집구조의 특성)

  • Won, Jong-Seo;Kim, Seog Hyun;Cho, Kang-Hyun
    • Ecology and Resilient Infrastructure
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    • v.4 no.1
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    • pp.34-43
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    • 2017
  • The Naeseong Stream as a tributary of Nakdong River has conserved the unique structure and function of a typical sand-bed stream ecosystem. However, it is expected to change the stream bed environments and then the fish fauna in the downstream of the dam after the operation of the Yeongju Dam from 2016. We collected fishes and investigated their habitat environments from 2014 to 2016 in the downstream of the Yeongju Dam under construction in order to monitor changes in habitat environment, fauna and community structure of fishes in the Naeseong Stream. The size of the bed materials increased immediately downstream of the Yeongju Dam under construction. Before the operation of the Yeongju Dam, Zacco platypus was dominated and Opsarichthys uncirostris amurensis, Coreoleuciscus splendidus, Hemibarbus longirostris and Pseudogobio esocinus were sub-dominated according to the different sampling sites. Hemibarbus labeo, H. longirostris, Pseudogobio esocinus, Gobiobotia nakdongensis, Cobitis hankugensis and Leiocassis ussuriensis were found as a psammophilous fish specific to sand stream in the Naeseong Stream. At the downstream of the dam, the fish community was classified into a group of gravel-bed fishes such as Microphysogobio yaluensis, Coreoleuciscus splendidus and Coreoperca herzi and a group of sand-bed fishes such as Hemibarbus labeo, Cobitis hankugensis and Gobiobotia nakdongensis. These fish communities gradually tended to change from sand-bed fish community to gravel-bed fish community during the construction of the Yeongju Dam. Therefore, it is necessary to collect the baseline data for the stream ecosystem conservation in the sandy stream by continuously monitoring changes in the environment and fish in the downstream of the Youngju Dam.

Numerical analysis of geomorphic changes in rivers due to dam pulse discharge of Yeongju Dam (댐 펄스방류로 인한 하천의 지형변화 수치모의 분석(영주댐 중심으로))

  • Baek, Tae Hyoa;Jang, Chang-Laeb;Lee, Kyung Su
    • Journal of Korea Water Resources Association
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    • v.56 no.12
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    • pp.871-881
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    • 2023
  • This study investigates the geomorphic changes and Bed Relief Index of the river downstream of the Yeongju Dam by Nays2DH, a two-dimensional numerical model, in order to grasp the dynamics of the downstream river while applying various flow patterns such as pulse discharge. It shows that the geomorphic and the bed elevations changes are the largest under the condition of the normalized pulse discharge. The total change in the riverbed is 29.88 m for uniform flow, 27.46 m for normalized hydrograph, 29.63 m for pulse flow and 31.87 m for pulse flow with normalized hydrograph which result in the largest variation in scour and deposition. The Bed Relief Index (BRI) increases with time under conditions of uniform flow, pulse flow and pulse flow with normalized hydrograph. However, BRI increased rapidly until 30 hrs after the peak flow (14 hrs), but decreased from 56 hrs under the condition of normalized hydrograph. Therefore, the condition of normalized hydrograph gives greater dynamics than the condition of a single flood or constant flow, and the dynamics increase downstream than upstream, resulting in an effect on improving the environment of the river downstream of the dam.

A Study on the Effect of Dredging and Operation of Weirs on Hydraulic Characteristics in Nakdong River (낙동강 수계 준설 및 수리시설물 운영에 따른 흐름특성 연구)

  • Ahn, Jung Min;Lyu, Siwan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.5
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    • pp.1829-1840
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    • 2013
  • It is essential to understand the hydraulic characteristics in accordance with the changes in the river environment and operating hydraulic structures for increasing flood-control capacity. The objective of this study is to analysis the effect of dredging and operation of weirs on hydraulic characteristics in Nakdong River(Seongju~Imhaejin). HEC-RAS model has been used to examine the hydraulic characteristics with considering the flow transition through the unsteady flow analysis and the information about the specifications of multi-functional weirs. The relationship between Manning n and roughness height k, the effect of weir installation and operation on the flow and stage, and the bed change resulted from the river treatment project have been examined by steady and unsteady flow analysis. It is expected that the result from this study can be the basic data for the river treatment and management.

Hydraulic Characteristic Analysis for Prevention of River Disaster at Estuary in the Eastern Coast of Korea (동해안 하천 하구부의 하천재해 방지를 위한 수리특성 분석)

  • Choi, Jong-Ho;Jun, Kye-Won;Yoon, Yong-Ho
    • Journal of Korean Society of Disaster and Security
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    • v.11 no.2
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    • pp.83-89
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    • 2018
  • The significant sedimentation at the estuary in the eastern coast of Korea frequently causes river mouth occlusion where disconnection between the river and sea is observed. River mouth occlusion causing watershed retention raises the environmental risk of the area as it impairs water quality and threatens the area's safety in the event of floods. This study proposes a plan to maintain stability of river channel and flow of flood discharge at the estuary with loss of its function for disaster prevention. To this end, the study tries to change the location and width of stream path, focusing on the center line of stream near the sand bar of river mouth. This allows to identify a shape of stream path that leads the most stable flow. To review the result, this study uses the SRH-2D, a model for two-dimensional hydraulic analysis, and conduct numeric simulation. The simulation result showed that the most effective plan for maintaining the stable flow of running water without having the area sensitive to changes in hydraulic characteristics is to lower the overall river bed height of the sand bar near the center line of stream to a equal level.

Evaluation of the effects of the river restoration in Hwangji Stream, the upstream reach of the Nakdong River

  • Bong Soon Lim;Jaewon Seol;Chang Seok Lee
    • Journal of Ecology and Environment
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    • v.48 no.1
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    • pp.85-95
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    • 2024
  • Background: In Korea, riparian zones and some floodplains have been converted into agricultural fields and urban areas. However, there are essential for maintaining biodiversity, as they are important ecological spaces. There are also very important spaces for humanity, as they perform various ecosystem services in a changing environment including climate change. Due to the importance of rivers, river restoration projects have been promoted for a long time, but their achievement has been insignificant. Development should be pursued by thoroughly evaluating the success of the restoration project. Ecological restoration is to accelerate succession, a process that a disturbed ecosystem recovers itself, with human assistance. Ecological restoration can be a test bed for testing ecological theories in the field. In this respect, ecological restoration should go beyond a 'simple landscaping exercise' and apply ecological models and theories in restoration practice. Results: The cross-section of the restored stream is far from natural rivers due to its steep slope and artificial material. The vegetation profiles of the restored streams did not reflect the flooding regime of the river. The species composition of the vegetation in the restored stream showed a significant difference from that of the reference stream, and was also different from that of an unrestored urban stream. Although species richness was high and the proportion of exotic species was low in the restored stream, the effect was offset by the high proportion of gardening and landscaping plants or obligate terrestrial plants. Conclusions: Based on both the morphological and ecological characteristics of the river, the restoration effect in the restored stream was evaluated to be very low. In order to solve the problems, a systematic adaptive management plan is urgently required. Furthermore, it is necessary to institutionalize the evaluation of restoration effects for the development of river restoration projects in the future.

Study on physical habitat suitability of Gobiobotia naktongensis in Naeseong Stream according to change of bed grain size (내성천 하상 입경 변화에 따른 흰수마자의 물리 서식 적합도 분석)

  • Lee, Dong Yeol;Park, Jae Hyun;Baek, Kyong Oh
    • Journal of Korea Water Resources Association
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    • v.56 no.9
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    • pp.553-562
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    • 2023
  • The Gobiobotia naktongensis is a species endemic to Korea, and it has recently been designated as a class I endangered species of freshwater fish. Naeseong Stream, one of the tributaries of the Nakdong River, where the Gobiobotia naktongensis was first discovered, provided an optimal habitat for the Gobiobotia naktongensis in the past with fine sand beds and riffle. Currently, due to the construction of Yeongju Dam and the excessive dredging of river channels by the local government, the riverbed armoring in the downstream area of the dam is undergoing rapid changes, and as a result, the habitat environment of the Gobiobotia naktongensis is deteriorating. In this study, the variations of the habitat suitability of the Gobiobotia naktongensis due to the change in the riverbed grain size of the Naeseong Stream were analyzed based on the WUA (weight usable area) using the physical habitat model, River2D. The study domain is the reach from Seoktap Bridge to Hoeryong Bridge downstream of Yeongju Dam. The change in riverbed grain size was analyzed using D50 acquired in 2010 and 2020, respectively. The substrate grain size of Naeseong Stream in 2020 was thicker than that in 2010, and the riverbed coarsening phenomenon was evident overall. As a result of the River2D analysis, the area in which the Gobiobotia naktongensis could inhabit was only about 0.75% in 2010 compared to the entire area of the flow, and even this decreased to 0.55% in 2020 due to riverbed armoring.

Two - Dimensional analysis in Dam Downstream due Spill Condition (방류조건에 따른 댐 하류부의 2차원 수치해석)

  • Lee, Jong-Hyeong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.2
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    • pp.911-918
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    • 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.

Evaluation on Disturbance and Adjustment of Close-to-Nature River Improvement for Creek (소하천의 자연형하천 정비사업에 따른 교란 및 적응 평가)

  • Kim, Kiheung;Lee, Hyeongrae
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.10 no.3
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    • pp.71-87
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    • 2007
  • In order to improve and manage rationally for Youngdam creek in Haman-gun, the channel change, water quality and ecological adaptation etc. were evaluated by monitoring during three years. The distinct differences of channel characteristics appeared in the extents of bed excavation and the revetment methods because overall reconstruction was occurred intense disturbance of width expansion and levee construction etc. The scour and deposition were caused according to channel characteristics of ripple and pool, and the adaptation of vegetation was distinguished from each revetment methods clearly. Water quality was maintained first class on the basis of BOD as 0.5~1.5mg/${\ell}$. The vegetation appeared in 380 species close-to-nature river improvement before, but 64 species it after one year, 159 species it after two year and 158 species it after three year. The animal life appeared in 123 species of close-to-nature river improvement before, but 103 species it after one year, 116 species it after two year and 119 species it after three year.