• Title/Summary/Keyword: River-bed change

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Analysis of Correlation on Physical Characteristics and Bed Materials in Natural Rivers (자연하천에서 하도의 물리적 특성과 하상재료의 상관관계분석)

  • Kim, Ki-Heung
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.13 no.2
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    • pp.95-104
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    • 2010
  • The purpose of this study is to analyze the correlation between physical stream characteristics and bed materials in natural rivers. Accordingly, four natural rivers were selected reference streams, they were Nam river, Sumjin River, Naesung River and Han River. Grain size distributions of bed materials were gravels, cobbles and boulders in Han river and Nam river, were sand, gravels, cobbles and boulders in Sumjin river and were sand in Naesung river. Four reference streams were divided into each two reference reaches (straight and bend) by plan and profile characteristics of naturally meandering stream. Therefore various reference reaches were chosen in the aspect of physical stream characteristics and grain size distributions. The results investigated and analyzed are as follows. The streams that grain sizes distributions of river bed materials were coarse were stable because they had variety of bed slope without sediment deposition, and then the riffles frequency and the physical characteristics were various. Also, velocitydepth regime were various in four kinds, and the response parts for water level change were small, so that channel flow status were stable and excellent condition. On the other hand, sand river that grain sizes distributions of river bed materials were fine had not the variety of parameters as velocity-depth regimes, sediment deposition, channel flow status and riffles frequency, so that the physical stream characteristics were not various.

An analysis of bridge perimeter of river channel change and sediment concentration distribution characeristic (교량 주변 하도구간에서 하상변동 및 유사농도 분포 특성분석)

  • Lee, Hyo-Jung;Jung, Do-June;Ahn, Seung-Seop
    • 한국방재학회:학술대회논문집
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    • 2008.02a
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    • pp.207-210
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    • 2008
  • Recently many studys have been continued Nak-Dong river. This study recognized the importance about a rivers floor change. The Nak-Dong main river of railroad bridge(2.423Km) waegwan-eup, Cilgok-gun, Gyeongsangbuk-do analyzed to the SED2D-WES model. This study recognized the difference of the model according to the existence and nonexistence of the bridge piers. At a result of mean velocity current is higher in bridge option appeared in this case. As well sediment transportation model show that river bed change appear the part of velocity is low.

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An Analysis of Bed Change Characteristics by Bed Protection Work (바닥보호공 설치에 따른 하상변동 특성 분석)

  • Son, Ah Long;Kim, Byung Hyun;Moon, Bo Ram;Han, Kun Yeun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.4
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    • pp.821-834
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    • 2015
  • This study presents the analysis of flow and bed change characteristics considering bed protection work built on the immediate downstream of weir to protect river bed from scouring. The study area is 37km reach from Hyunpoong station to Masuwon station including Hapcheon- Changryoung multi-function weir in the Nakdong river. CCHE2D model is calibrated and validated for evaluating the flow and bed change characteristics during Typhoon Kompasu in 2010. Three simulation conditions are set up: Case 1 is a natural channel without installation of weir. Case 2 involves an installation of weir in the natural channel. Case 3 involves an installation of weir with bed protection in the natural channel. Flood frequency (50, 100 and 200yr) is applied to each scenario to analyze the effects of bed protection work. While the sediment rate is increased in the downstream of fixed gate and sluice-type gate, river bed scouring rate is increased in the downstream of lift-type gate in Case 2 comparing with the results of Case 1. The river bed scouring is not occurred in the immediate downstream of weir (~30m) due to the effect of bed protection, but larger amount of sediment is occurred in the downstream of weir (60m~) which the bed protection is not installed comparing with the results Case 1. Through the results of simulation considering bed protection work, this study would be helpful to expect bed change and operate the weir as well as manage.

Long-term Bed Change Analysis and Equilibrium Bed Elevation Prediction after Weir Construction in Nakdong River (낙동강의 보 구조물 설치 후 장기 하상변동 분석 및 평형하상고 예측에 관한 연구)

  • Ji, Un;Jang, Eun-Kyung;Kim, Won
    • 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.

Mechanism of Wetland Formation according to Interaction of River Bed Fluctuation and Plant Success in the Hangang River Estuary (한강하구에서 하도변화와 식물천이의 상호작용에 따른 습지형성 기작)

  • Lee, Samhee;Youn, Sukzun
    • Journal of Wetlands Research
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    • v.24 no.4
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    • pp.320-330
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    • 2022
  • The Hangang river estuary, which is a natural estuary without structures such as estuary barrage, is an ecological pathway connecting the sea and rivers. Accordingly, Hangang river estuary has various species, and there is very valuable. Sediment classification in Hangang river estuary is three-dimensionally and diversely is distributed. Sediment classification in Hangang river estuary is also sensitively changed according to various factors such as climate change and river development. It is typically cause to landform and to develop a compound cross section. In Janghang wetland, the plant success is remarkable according to the morphological change at river bed. The purpose of this study is to identify the mechanism of wetland formation based on the observation on-site. As a result of the observation, Janghang wetland where was artificially created, has been grown according to the river bed change based on the flow rate and the plant success. The viscous surface layer material(fine grains of wash rod properties), which is not the main material(sand) of the river bed, but sub-materials of river bed, jas been settled on the pioneer plants(bolboschoenus planiculmis, etc.). It is an important role in the growth of a compound cross section and a wetland. After the wetland developed to the compound cross section, it is observed that the pioneer plants are transferred to other plant species.

The relationships of erosion and river channel change in the Geum river basin (금강유역의 침식과 하상변동과의 관계)

  • 양동윤;짐주용;이진영;이창범;정혜정
    • The Journal of Engineering Geology
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    • v.10 no.2
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    • pp.52-74
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    • 2000
  • The basement rock of upper stream of Keum River Valley consists of Precambrian gneiss which is resistant to weathering. That of mid and lower stream valley, however, is mainly composed of Mesozoic granites which are vulnerable to weathering. The upstream part of Geum River Basin is typified by the deeply-incised and steep meandering streams, whereas mid and lower part is characterized by wide floodplain and gently dipping river bottom toward the Yellow Sea. In particular flooding deposits, in which are imprinted a number of repetitions of erosion and sedimentation during the Holocene, are widely distributed in the lower stream of Geum River Basin. For understanding of erosions in the mid and lower stream of Geum River Basin, the rate of erosion of each small basins were estimated by using the data of field survey, erosional experiments and GIS ananlysis. It was revealed that erosion rate appeared highest in granite areas, and overall areas, in this field survey were represented by relatively high erosion rates. By implemeatation of remote sensing and imagery data, the temporal changes of river bed sediments for about last 11 years were successfully monitored. Observed as an important phenomenon is that the river bed has been risen since 1994 when an embankment (Dyke) was constructed in the estuarine river mouth. From the results derived from the detailed river bed topographical map made in this investigation, the sedimentation of the lower river basin is considered to be deposited with about 5 cm/year for the last 11 years. Based on this river bed profile analysis by HEC-6 module, it is predicted that Geum River bed of Ganggyeong area is continuously rising up in general until 2004. Although extraction of a large amount of aggregates from Gongju to Ganggyung areas, the Ganggyung lower stream shows the distinct sedimentation. Therefore, it is interpreted that the active erosions of tributary basins Geum drainage basins can affect general river bed rising changes of Geum River.

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Natural and Artificial Bed Change Analysis through Sediment Budget Analysis of Nakdong River Channel (before the Four Rivers Restoration Project) (낙동강 하도의 유사수지 분석을 통한 자연적 그리고 인위적 하상변동 분석(4대강살리기 사업 이전))

  • Son, Kwang Ik;Ji, Un
    • Journal of Korea Water Resources Association
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    • v.48 no.1
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    • pp.1-8
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    • 2015
  • General features of sediment budget for the Nakdong River before the Four Rivers Restoration Project were analyzed using surveying, dredging, and mining data for the past 20 years, as well as sediment data measured from the tributaries, and numerical modeling, etc. As a result of the sediment budget analysis of the Nakdong River before the Four Rivers Restoration Project, sediment inflow supplied from the watershed is $2,100,000m^3/yr$ and sediment outflow including mining and dredging volumes is $10,180,000m^3/yr$. Therefore, the bed change volume estimated by the sediment budget analysis is $-8,080,000m^3/yr$ of the bed erosion volume which is similar to the analysis result ($-8,300,000m^3/yr$) of natural and artificial bed changes using the surveyed data.

Determination of the Optimal Sediment Discharge Formula for Hyeongsan River Using GSTARS (GSTARS모형을 이용한 형산강의 최적 유사량공식 결정)

  • Ahn, Jung Min;Lyu, Siwan;Lee, Nam Joo
    • 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.

Prediction of Long-Term River Bed Changes in Saemangeum Area (새만금지구 장기 하상변동 예측)

  • Jung, Jae-Sang;Song, Hyun Ku;Lee, Jong Sup;Kim, Gweon Su
    • 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.

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Ratio of Bedload to Total Sediment Load in Gravel-bed Rivers (자갈하천 총유사량에 대한 소류사의 비율)

  • Park, Sang Doeg
    • Journal of The Geomorphological Association of Korea
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    • v.25 no.2
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    • pp.15-29
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    • 2018
  • The sediment transport process in a river reflects the process of geomorphological change in the watershed, influencesthe river bed variation and the river channel migration, and is a parametric phenomenon that exhibits a dynamic self-adjusting process. Sediment load is divided into bedload and suspended load depending on the dominant mechanism. Quantitative sediment load is important information for solving river problems. Because it is difficult and time consuming to measure bedload, compared to that ofsuspended load, data on the sediment transport load and the research required for the gravel-bed rivers are insufficient. This study is to analyze the ratio of the bedload to the total sediment load in gravel-bed rivers. The sediment load ratio in gravel-bed rivers increases with the flow rate per unit width, and the rate of the bedload varies more rapidly than the suspended load. The sediment transport efficiency coefficient has been affected by the ratio of the flow depth to the mean diameter of particles and has been dependent on the shear velocity Reynolds number. So $A^{\ast}$ and $B^{\ast}$ are introduced to compensate for the uncertainties such as bed materials, sediment transport, and flow velocity distribution, and the coefficient of bedload ratio has been presented. For the sediment load data in experimental channels and rivers, A* was 3.1. The dominant variables of $B^{\ast}$ were $u_*d_m/{\nu}$ in the gravel-bed and h/dm in the sand-bed. When $B^{\ast}$ the is the same, in the experimental channels the coefficient of bedload ratio was affected by the bed forms, but in the rivers it was of little difference between the gravel-bed and sand-bed.