• Journal of Korea Water Resources Association
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• v.32 no.6
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• pp.697-709
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• 1999

Two dimensional finite element model(RMA) is applied to examine sediment transport behavior near Buyeo water intake station of the Keum River. The simulation results of bed change with various discharge conditions agree with those of observation. As the alternatives of channel modification and resulting bed lowering near intake station, construction of jetties and removal of small island are considered. The station of jetties diverted the main stream toward the other side and the width of the main stream did not change so much. The bed elevation of the main channel is reduced about 5~20 cm, when flow condition of 12,030㎥/sec applied. The removal of small island provides the less significant effect on sediment movement. This study shows that the construction of jetties would be effective to reduce the entrainment of sediment.

• Journal of Environmental Impact Assessment
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• v.20 no.1
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• pp.61-69
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• 2011

Integrated stream naturalness based on abiotic and biotic factors were developed. Abiotic factors considered in this study were types of land use in the riparian area, river bank and high water bed streamside, revetment, bed substrate and artificial construction of streamside. Biotic factors included types of vegetation, assemblages of fish, macroinvertebrate, bird and mammal(Otter) in streams. The presence/absence of legal species and biological assessment index were also weighted as important parameters in this study. Scoring criteria selected for each matrix was five rating system; 1=poor, 2=moderate, 3=fair, 4=good, 5=excellent. Numerical ratings for the matrix were then summed. This resulted in a minimum score of 13 if all matrix at a site were poor, and a maximum score of 65 if all matrix were excellent. Five grade system from poor(I) to excellent condition(V) was employed. To verify its validity in natural environment, the evaluation system was applied to the Gapchun stream which is a test bed selected. Our result showed that stream naturalness of each reach was clearly distinguished by biotic and abiotic characteristics. Determination of correlation coefficient between abiotic and biotic factors was also high ($R^2=0.96$, p<0.05). In conclusion, assessment for stream naturalness reflecting abiotic and biotic factors was useful method representing stream integrated.

• Journal of Korea Spatial Information System Society
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• v.10 no.2
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• pp.81-93
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• 2008

Current re-arrangement of river and waterway has been made uniformly ignoring characteristics of individual rivers thereby aggravating artificial river restructuring. Subsequently this severely affects the rivers' physical, chemical, and biological phenomenon. 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 river changes to evaluate the major causes of the river disturbance and its impacts is essential. Therefore, this study mainly focused on 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. For the analysis, the study area on the downstream of the river was selected and airphotos of the area were converted into GIS format to generate 'shape' files to secure waterways, river banks, and auxiliary data required for analyzing river disturbance. 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 relatively accurate numbers representing sinuosity of the waterway and relevant changes. As the major results from the analysis, the relocation of waterways and the level of river sinuosity were quantified and used to verify the impacts on the stability of the waterways especially in the downstream of the dam. The results from this study enabled effective establishing proper measures against waterways' unstability, and emphasized subsequent researches for identifying better alternatives against river disturbances.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.2
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• pp.17-24
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• 2007

This study analyzes the flood inundation in low agricultural area caused by rainfall during typhoon periods and how flood inundation areas should be affected. GIS techniques, HEC-HMS and HEC-GeoHMS were used for flood runoff, HEC-RAS was applied in water surface elevation analysis at each cross-section. RMA2, SED2D were applied for runoff characteristics of inundation areas and river bed change and distribution of sediment. As a result, velocity distribution was analyzed 2.6 m/s-3.4 m/s in flood inundation by water level increase. In the case of bed elevation change, most sediments were deposited to the parts that adjoin bank.

• 한국해양학회지
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• v.10 no.2
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• pp.67-75
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• 1975

Tidal Flushing at the entrance channels of tidal bay or estuary in the central western coast of Korea; Gum River Estuary, Garorim Bay, Asan Bay, and Yeomha Estuary were studied with the recent data of current surveys measured by curret meter at three or five anchored stations along the section for one or two tidal periods at mean spring tide. Equilibrium relationship between tidal prism at mean spring tide and minimum flow area below the mean sea level of the channel in alluvial material was found as of O'Brien's (1931, 1969) study. Bed load transport in the tidal channel is balanced with the tidal flushing ability having a mean velocity of about 0.75m/sec or maximum velocity of about 1.25m/sec for a half tidal cycle over the section at mean spring tide which fairly agree with Brunn's study(1955, 1957). flushing actions for different hydraulic depth( mean depth) and bed material size in the channel were reviewed and found that it depend to a minor extent on the factors.

• Water for future
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• v.6 no.1
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• pp.19-28
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• 1973

Presented is the results of a model study about scouring around a bridge pier. 24 different types of piers were inestigated for the depth and width of scouring. The grain size of sand used in the experiment ranges from 0.149 to 2, 380mm, The time required to reach the stable bed formation was about 30min, with the range of Froud number from 0.58 to 0.69. It has been found that the scouring is most severe at the frontal side of the pier and decreases with decreasing a contact angle (between the center line of the pier and tangent to the frontal face). For design purposes, it is recomanded that the contact angle at the frontal face is 25 degrees for a triangular type and 40 deyrees for a circular type respectively.

• Water for future
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• v.25 no.2
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• pp.79-87
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• 1992

This study is a model on the Migration Characteristics which developed by using the equations for conservation of mass, momentum and for lateral stability of the streambed, an the model can be examined for magnitude and location of near-bank bed scour as well as rates and direction of meander migration in which sine-Wave type rivers(SWR) of the small sinuosity. It is evident from this study that the transverse bed slope factor B' and transverse mass flux factor $ play significient roles, and show reasonable that the values are B'=4.0 and $=0.4 respectively . It will be a useful guide in planning, design, construction, and development of SWR river-basin projects.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.2
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• pp.127-133
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• 1999

The MOSU model, a depth-averaged two-dimensional sediment transport model, is applied to simulate the bed level changes before and after dock construction in Daemyung site. The model is a semi¬coupled finite difference model that can be applied to a river, a reservoir, a lake, estuaries, or coastal regions, The model is able to simulate the transport of fine sand, silt, and clay. The model parameters are estimated by qualitative calibration. A prediction result of the numerical model shows that the bed level changes due to dock construction are little.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.5
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• pp.117-124
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• 2010

Most of the rivers which exist in nature are not a single river but the network that is composed of several branches and mainstreams. The river network are more complicated than other sigle rivers and streams. Therefore the hydraulic characteristics are sensitively changed by reduction and expansion of the width in the confluence or the variation of the flux. In this paper, the hydraulic characteristics were calculated by the change of the width and length in the confluence and the hydraulic model test. The deposit of confluence emerged at the left bank, right bank and the stagnation sector. As the total flow in the branch have increased, stagnation of the left bank and right bank have decreased. When the width of the downstream have been get smaller from 3 m to 2 m, the deposit of the left bank and right bank and stagnation sector have decreased. But as the eddy flow in the center of the confluence is occurred, the erosion has been increased. The result of this paper can be used as a basic data of water management around the junction and for maintenance on the ground of development of the river.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.365-376
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• 2021

In general, domestic streams and rivers are composed of alluvial rivers consisting of sand and gravel beds. These rivers can cause erosion and riverbed changes due to sudden changes in flow rates, such as floods, torrential rains, and heavy rains. In particular, there are various types of erosion, such as contraction erosion caused by changes in river shape, or local erosion occurring around obstacles such as piers, abutments or embankments. In addition, river changes can occur in various forms, such as static or dynamic periods, due to limitations such as flow rate, velocity, and shear stress. This study focused on the erosions of embankments directly related to human casualties among various river structures, and evaluated limit velocities and critical shear stress in order to identify changes in strength of natural materials by identifying the characteristics of natural hoan materials and resistance to erosions. In particular, the limitations of materials according to the type of materials in the river, characteristics of particles, and size of particles were studied using Soil loss, which is a change in the volume of the revetment material, and it is intended to be used as basic data for river design and restoration.