• Title/Summary/Keyword: river-bed change

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A Study on the Applicability of GSTAR-1D to the Riverbed-Level Variation in the Geum River (GSTAR-1D 모형의 금강 하상변동예측 적용성에 관한 연구)

  • Chung, Sung-Young;Park, Bong-Jin;Jung, Kwan-Sue
    • Proceedings of the Korea Water Resources Association Conference
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    • 2006.05a
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    • pp.1611-1615
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    • 2006
  • The purpose of this study is to simulate the riverbed profile changes downstream of Daecheong re-regulation dam from 1988 to 2001, to evaluate the model's applicability and to predict a long-term riverbed-level variation between 2002 and 2017. As a result of simulation 14 sediment transport equations provided by GSTAR-1D, it was found that Acker's & White formula was the most stable relatively. The interval used to calculate its stability was 7 days for bankful discharge$(1,000m^2/s)$, 3 days for daily maximum flow$(4,273m^2/s)$, 1 day for hourly maximum flow$(7,605m^2/s)$ and minimum flow$(8.5m^2/s)$. The simulation results of river bed changes were evaluated and compared to its measure data from 1988 to 2001. It was showed that there was the degradation for a section between Daecheong re-regulation dam and Maepo water stage gage station due to bed-material, and the degradation for a reach between Maepo and Gongju water stage gage station due to massive aggregate collection. Also, as a result of simulating the river profile change for 2002 to 2017, it was predicted that the section between Daecheong re-regulation dam and Geumnam Bridge would remain as the present profile and the reach between Maepo and Gongju water stage gage station would have some degradations in several parts, which would be stable as a whole unless it was due to artificial river profile change.

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Influences of Vegetation Invasion on Channel Changes in the Deposition Area of Torrential Stream (계상퇴적지내의 식생침입이 유로변동에 미치는 영향)

  • Ma, Ho-Seop;Lee, Heon-Ho
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.3 no.3
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    • pp.12-19
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    • 2000
  • The purpose of this study is to evaluate the channel changes according to the temporal and spatial distribution of the deposition area by the vegetation invasion in Kyesung-river. The deposition area mainly occurred by landslide and debris flow from the headwater channel. And also the movement of subsequent downstream depends upon the site of deposits by a varity erosional processes. As the age of deposition area is older, it had a tendency to stable by plant invasion relatively. The vegetations grown in deposition area were very effective to estimate a historical deformation process of river-bed occurred by landslide. The vegetations around deposition area consisted of the same as tree species grown in forest area of circumference like Pinus densiflora, Styrax japonica, Quercus acutissima and Salix gracilistyla. If the torrential stream is flooding, the deposition area of 1 to 5 years can be change to the channel easily. Deposition area of 11 to 23 years had a high river-bed because it passed long time since deposited, and amount of sedimention is much more in wide than in narrow channel. It is consider that the change of channel had many influenced by the span of survial time, scale and movement frequency of deposition area after the vegetation invasion.

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Strategy Prospects of Environmental Restoration of Stream Side in Japan(IV) (일본(日本)에서 계류변(溪流邊)의 환경복원(環境復元) 발전전략(發展戰略)(IV))

  • Park, Jae-Hyeon;Woo, Bo-Myeong;Lee, Heon-Ho
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.3 no.4
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    • pp.84-90
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    • 2000
  • The objective of this study was to introduce the current status and development strategy for an environmental restoration of stream side in Japan, and to consider a methodology which could be effectively applied for the environmental restoration of stream side in Korea. 1. In order to change the recent direction of the forest conservation and erosion control projects which are focused on the restoration of stream side ecology, we have to quit the past erosion control policy such as water control purpose, and establish new plans regarding on the forest conservation and erosion control which is considered the regional environmental restoration of watershed. 2. When we restore stream side and river side ecosystem, we should establish restoration plans which can keep the original nature of stream and river. 3. The forest conservation and erosion control construction projects for the restoration of stream and river ecosystem should be planned for the perfect restoration of their ecosystem by way of sustainable maintenance and management. 4. The restoration direction of stream and river ecosystem needs to be planned to restore the diversity of small geographies such as waterway, shoal and puddles rather than flattening of stream bed. 5. The main principle in the restoration of stream and river ecosystem is to accomplish forest conservation and erosion control construction projects which can conserve the existing stream and river ecosystem.

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An Experimental Study on Scour of Succession Row Piers, Multiple Row Piers and Pile Group (일련연속교각, 다중연속교각, 말뚝군의 세굴특성에 관한 실험적 연구)

  • Choi, Han-Kyu;Kim, In-Ho;Choi, Yong-Mook
    • Journal of Industrial Technology
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    • v.20 no.A
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    • pp.123-129
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    • 2000
  • As materials on the river bed have been changing through erosion, transportation and accumulation, so does the waterway's section. So many bridges have nowadays been constructed to the same direction as water flows. However further researches are still needed on the scours of succession row piers and multiple row piers. Analyzing them through hydraulic stimulation experiments, this study deals with the scour character with the change of diameters in row piers which have been built in the identical direction of water flow and also the part-scour character change in multiple row piers.

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Formation processes of low river terraces in Korea (우리나라 저위하안단구(低位河岸段丘)의 형성요인)

  • Son, Myoung-Won
    • Journal of the Korean association of regional geographers
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    • v.7 no.2
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    • pp.71-81
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    • 2001
  • According to the change of stream power/resisting power relationship due to the crustal movement or the climatic change, most channel landforms which reflect the equilibrium state of fluvial system are eroded and a part of them is remained as a river terrace. In many rivers in Korea are extensively distributed the relatively younger low river terraces. But their accurate formation mechanism is not known. In this paper, the formation processes and the dating of low river terraces distributed in Nakdong River basin will be investigated. Stream power of the downward erosion was revived because the sea level fell down. So stream power was superior to the resisting power under the cool-wet climatic condition during the last glacial period. Thus the river bed was excavated deeply, so that low river terraces were built up. And many incised meander loops were cut during this period. But, when fluvial system did not have equilibrium over all reaches, the last glacial period ended and the sea level initiated to rise rapidly. The headward erosion from the fall of sea level during the last glacial period had kept up to Hagye Fall because of the cutting of incised meander loops. Deeply excavated valleys and abandoned channel of cut-meander in lower reaches of a stream were filled with sediments. Thus the longitudinal profile of the uppermost reaches reflect the last interglacial, the upper reaches the last glacial, and the middle/1ower reaches recent fluvial system. Therefore low river terraces have been formed since the last glacial period.

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A Preliminary Verification of the Influences of Hydrologic Regime Change and Nutrients Influx on Vegetation Recruitment on Riparian Bars (하천식생 이입 현상에 대한 수문현상 변화와 영양염류 영향의 예비 검증)

  • Woo, Hyoseop;Kang, Joon-goo;Cho, Hyung-Jin;Choi, Yi-song;Park, Moon-hyeong
    • Ecology and Resilient Infrastructure
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    • v.2 no.4
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    • pp.284-290
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    • 2015
  • In this study, two hypotheses were examined to preliminarily verify for the vegetation recruitment and establishment on riparian bars in unregulated rivers; hydrologic regime change and nutrients influx into streams. In order to preliminarily verify the first hypothesis, precipitation patterns were analyzed during a period from March through to May when reeds, the most common riparian vegetation in Korea, germinate and start to grow in riparian areas. The results show that during the last 35 years, the total precipitation during the three-month period decreased by about 15 %, while the total annual one increased by about 15% in Korea. In order to verify the second hypothesis, a preliminary experiment was conducted with a set of two-vegetative flumes for one year. In this experiment, a stream flow with reeds on the riparian sand bars was simulated with a flume with reeds planted on the sand bed and water with a concentration of 3.5 mg of N flowing in the flume for four hours. For comparison, clean water was circulated in the same way in another flume for simulating a stream flow without N. The experimental results show that the growth rate of reeds in N-mixed flow exceeds that in clean water flow by about 30%. The above two results could explain the phenomenon of change in unregulated rivers from white river to green river in Korea, although they were obtained through limited extents of analysis and experiment.

Numerical Analysis on Flow and Bed Change Characteristics by Discharge Variations at the Confluence of Nakdong and Geumho Rivers (낙동강과 금호강 합류부 구간에서 유입유량에 따른 흐름 및 하상변동 특성 변화에 관한 수치모의 연구)

  • Jang, Eun-Kyung;Ji, Un
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.12
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    • pp.659-667
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    • 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.

Analysis of River Disturbance using a GIS(II) (GIS기법을 이용한 하천 교란 실태의 분석(II))

  • Park, Eun-Ji;Kim, Kye-Hyun;Jang, Chang-Lae
    • Journal of Korea Spatial Information System Society
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    • v.10 no.4
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    • pp.27-35
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    • 2008
  • Current re-arrangement of rivers and waterways have been made uniformly ignoring characteristics of individual rivers thereby aggravating artificial river restructuring. On the contrary, quantitative techniques to evaluate the aftermath of artificial river disturbance such as uprising of river bed, intrusion of foreign fisheries, and changes of ecological habitats are not available. To establish such quantitative techniques, analysis of the river changes to evaluate the major causes of the river disturbance and its impacts is essential. Therefore, research for proposing a method which can be applied for the development of techniques to investigate river disturbance according to the major factors for the domestic rivers using airphotos and GIS techniques was preceded. In this study, the study area on the downstream of the river was selected and analysis of river disturbance using preceding method was done to confirm the benefit of analyzing river disturbance using GIS techniques. Trend analysis of the waterway sinuosity and changes of the flow path leaded to detailed verification of the river disturbance for specific location or time period, and this enabled to generate relatively accurate numbers representing sinuosity of the waterway and relevant changes. Also, it is possible to predict the effect on the current re-arrangement of the river and waterway to river flow using the analysis of past river change. It is necessary to establish GIS based proper measures for environmental river restoration using the results from this study and future works.

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한강하류지형면의 분류와 지형발달에 대한 연구 (양수리에서 능곡까지)

  • Park, No-Sik
    • Journal of the Speleological Society of Korea
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    • no.68
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    • pp.23-73
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    • 2005
  • Purpose of study; The purpose of this study is specifically classified as two parts. The one is to attempt the chronological annals of Quaternary topographic surface through the study over the formation process of alluvial surfaces in our country, setting forth the alluvial surfaces lower-parts of Han River area, as the basic deposit, and comparing it to the marginal landform surfaces. The other is to attempt the classification of micro morphology based on the and condition premising the land use as a link for the regional development in the lower-parts of Han river area. Reasons why selected the Lower-parts of Han river area as study objects: 1. The change of river course in this area is very serve both in vertical and horizontal sides. With a situation it is very easy to know about the old geography related to the formation process of topography. 2. The component materials of gravel, sand, silt and clay are deposited in this area. Making it the available data, it is possible to consider about not oかy the formation process of topography but alsoon the development history to some extent. 3. The earthen vessel, a fossil shell fish, bone, cnarcoal and sea-weed are included in the alluvial deposition in this area. These can be also valuable data related to the chronological annals. 4. The bottom set conglometate beds is also included in the alluvial deposits. This can be also valuable data related to the research of geomorphological development. 5. Around of this area the medium landform surface, lower landform surface, pediment and basin, are existed, and these enable the comparison between the erosion surfaces and the alluvial surfaces. Approach : 1. Referring to the change of river beds, I have calculated the vertical and horizontal differences comparing the topographic map published in 1916 with that published in 1966 and through the field work 2. In classifying the landform, I have applied the method of micro morphological classification in accordance with the synthetic index based upon the land conditions, and furthermore used the classification method comparing the topographic map published in 1916 and in that of 1966. 3. I have accorded this classification with the classification by mapping through appliying the method of classification in the development history for the field work making the component materials as the available data. 4. I have used the component materials, which were picked up form the outcrop of 10 places and bored at 5 places, as the available data. 5. I have referred to Hydrological survey data of the ministry of Construction (since 1916) on the overflow of Han-river, and used geologic map of Seoul metropolitan area. Survey Data, and general map published in 1916 by the Japanese Army Survbey Dept., and map published in 1966 by the Construction Research Laboratory and ROK Army Survey Dept., respectively. Conclusion: 1. Classification of Morphology: I have added the historical consideration for development, making the component materials and fossil as the data, to the typical consideration in accordance with the map of summit level, reliefe and slope distribution. In connection with the erosion surface, I have divided into three classification such as high, medium and low-,level landform surfaces which were classified as high and low level landform surfaces in past. furthermore I have divided the low level landform surface two parts, namely upper-parts(200-300m) and bellow-parts(${\pm}100m$). Accordingly, we can recognize the three-parts of erosion surface including the medium level landform surface (500-600m) in this area. (see table 22). In condition with the alluvial surfaces I have classified as two landform surfaces (old and new) which was regarded as one face in past. Meamwhile, under the premise of land use, the synthetic, micro morphological classification based upon the land condition is as per the draw No. 19-1. This is the quite new method of classification which was at first attempted in this country. 2. I have learned that the change of river was most severe at seeing the river meandering rate from Dangjung-ni to Nanjido. As you seee the table and the vertical and horizontal change of river beds is justly proportionable to the river meandering rate. 3. It can be learned at seeing the analysis of component materials of alluvial deposits that the component from each other by areas, however, in the deposits relationship upper stream, and between upper parts and below parts I couldn't always find out the regular ones. 4. Having earthern vessel, shell bone, fossil charcoal and and seaweeds includen in the component materials such as gravel, clay, sand and silt in Dukso and Songpa deposits area. I have become to attempt the compilation of chronicle as yon see in the table 22. 5. In according to hearing of basemen excavation, the bottom set conglomerate beds of Dukso beds of Dukso-beds is 7m and Songpa-beds is 10m. In according to information of dredger it is approx. 20m in the down stream. 6. Making these two beds as the standard beds, I have compared it to other beds. 7 The coarse sand beds which is covering the clay-beds of Dukso-beds and Nanjidobeds is shown the existence of so-called erosion period which formed the gap among the alluvial deposits of stratum. The former has been proved by the sorting, bedding and roundness which was supplied by the main stream and later by the branch stream, respectively. 8. If the clay-beds of Dukeo-bed and Songpa-bed is called as being transgressive overlap, by the Eustatic movement after glacial age, the bottom set conglomerate beds shall be called as being regressive overlap at the holocene. This has the closest relationship with the basin formation movement of Seoul besides the Eustatic movement. 9. The silt-beds which is the main component of deposits of flood plain, is regarded as being deposited at the Holocene in the comb ceramic and plain pottery ages. This has the closest relationship with the change of river course and river beds.

Topographical change of sandbar and vegetation settlement in Jang-Hang wetlands for Han River Estuary Wetlands Restoration (한강 하구 습지복원을 위한 장항습지의 사주 지형변화 및 식생정착)

  • Ahn, Hong-Kyu;Kim, Si-Nae;Chung, Sang-Joon;Lee, Dong-Jun;Lee, Sam-Hee
    • Journal of Wetlands Research
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    • v.14 no.2
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    • pp.277-288
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    • 2012
  • Estuary is unique habitat ground under substantial changes of water quality, river side, bed material, and micro topography. Construction of SinGok underwater weir with excessive dredging for downstream of weir has changed hydraulic conditions of Han River. This study investigates spatial changes of estuary and expansion process of vegetation on sandbar for JangHang estuary in Han River through analysis of physical and ecological characteristics. As a result of investigation, we found that area of sandbar in JangHang estuary is expanded six times compared between 1985 and 2006, and area of Phragmites australis is gradually decreased while area of Salix subfragilis Anderson. is increased. Also the analysis result of soil layer shows that the Jang-Hang wetlands are created by effect from river, and woody plants are settled from middle part of wetlands, then spread to upper and lower part of wetlands.