• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3B
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• pp.315-321
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• 2008

Recently, in the light of environments and utilization, countermeasures to preserve beaches in coastal area are required without depending on such as jetties and breakwaters. The necessity of integrated sand management including not only coastal sediment but also sediment discharge from hinterland rivers is increased so as to establish long-term counterplan for sediment transport. In this regard, the following subjects are examined in this study; efficient ways for discharged sand to be transported from a river to the neighboring coast, the river terrace occurrence and its growth at the river delta, measures to improve storage efficiency of the discharged sand and measures to prevent the sand resources from being discharged into the deep sea during flooding. In recent, A jetty of 260 m length was constructed at Namdae River mouth in the year of 2005 as a countermeasure against the occurrence of sand-bar at river mouth and its close. In this study, a series of numerical experiments were carried out to investigate the characteristics of sediment transport and morphological change due to the construction of jetty at the entrance of Namdae River mouth. Firstly, The sand discharge from Namdae River is quantified by one-dimensional numerical analysis assuming the mixed sand of three different particle diameters. Then, in order to understand the transport behavior of the sand discharge from river and river mouth phenomena the numerical experiments were then conducted to examine the flow behaviors of river efflux and wind generated circulations in coastal area. And, after establishing the numerical model system, which predicts the sea bed changes obtained from the flux model combining with the wave propagation, wave-induced currents and sediment transport models, the sediment transport in the vicinity of Namdae River mouth is analyzed.

• Journal of Korea Water Resources Association
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• v.42 no.4
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• pp.271-279
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• 2009

The objective of this study is to develop the scheme to apply one-dimensional finite volume method (FVM) to natural river with complex geometry. In the previous study, FVM using the Riemann approximate solver was performed successfully in the various cases of dam-break, flood propagation, etc. with simple and rectangular cross-sections. We introduced the transform the natural into equivalent rectangular cross-sections. As a result of this way, the momentum equation was modified. The accuracy and applicability of newly developed scheme are demonstrated by means of a test example with exact solution, which uses triangular cross-sections. Secondly, this model is applied to natural river with irregular cross-sections and non-uniform lengths between cross-sections. The results shows that the aspect of flood propagation, location and height of hydraulic jump, and numerical solutions of maximum water level are in good agreement with the measured data. Using the developed scheme in this study, existing numerical schemes conducted in simple cross-sections can be directly applied to natural river without complicated numerical treatment.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.2
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• pp.76-88
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• 1982

The stream morphological characteristics of a basin have important influence upon the analysis of runoff. In this study, the laws of stream morphology-the law of average stream fall and the law of least rate of potential energy expenditure-which were derived based on the analogy of entropy in thermodynamics are introduced and their validity is analysised with the data taken from the topographic maps covering the whole Geum River system. The first law is the Law of Average Stream Fall which states that under the dynamic equilibrium condition the ratio of average fall between any two different order stream in the same river basin in unity. The second law is the law of least rate of energy expenditure which states that all natural streams are intended to choose their own course of flow such that the rate of potential energy loss per unit mass of water this course is a minimum. The parameters representing the morphological characteristics of 13 tributaries in the Geum River system such as stream bifurcation ratio and stream concavity were Computed from the Horton-Strahler's laws and are used to check the law of average stream fall. The result showed that the law of average stream fall agrees reasonably well with law of Horton-Strahler. Concavity of a river basin is shown to be the determinative factor to the formation of a stream system. Concavity of a river basin is shown to be the determinative factor to the formation of a stream system. Based on Horton's Law and the law of average stream fall, longitudinal stream profiles can be calculated.

• Journal of Korea Water Resources Association
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• v.37 no.1
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• pp.55-66
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• 2004

The Hapchon Dam, located upstream of the Hwang River, Korea, was constructed in December, 1988. Due to the lack of storage of water, the dam gate has not been operated during last ten years. Thus, a new ecosystem has been established at the downstream part of the dam. This is not a common phenomenon which can be found elsewhere in the country. The present study investigates the effect of flow regime change on the river morphology and vegetation cover in the downstream river reach after the dam construction. The analysis of flow regime is carried out, and the changes in bed elevation and in channel cross sections are examined. Site investigations including tree ring tests are also performed. The increase in the vegetation cover is estimated by comparing aerial photographs taken before and after dam construction.

• 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.

• Journal of the Speleological Society of Korea
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• no.72
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• pp.19-30
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• 2006

The purpose of this study is to clarified the geology and geomorphic characteristics of the Hantan River Basin. In this area, some kind of landforms are developed such as pre-land forms, lava plateau, and present landforms etc. Some river terraces are peculiar features in the area. Some conclusions are as follows : The vicinity of the Hantan River is lava plateau formed from the volcanic activity. Some steptoes are located in the lava plateau. Baekeuiri formation means the river bed boulder beneath the lava formation. The development of drainage patterns are unstable and the bifurcation ratio, the ratio of mean length of the river are lower than the other rivers. The relative height of the terraces is about $5{\sim}25m$ and the terraces are alluvial terraces. In the Jiktang Fall area, bedrock is granite and basalt plateau covered the bedrock. In that point, the old erosion surface is relatively steeper than the horizontal-basalt plateau. Vertical columnar joints are developed and weathering materials creep on the valley wall. The cross section of the landform of the Kosukjung vicinities are somewhat different from the landforms of Jiktang Fall. The bedrock near the Kosukjung is granite that is the same with the Jiktang Fall. But the cross section shows a asymmetrical curve from each side.

• Journal of Korea Water Resources Association
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• v.42 no.10
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• pp.845-855
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• 2009

In this study, changing characteristics of bed materials downstream of Daecheong Dam by flushing flow was investigated. Flushing flow affected the downstream environment in such a way that the mean diameter of bed material was increased and the standard deviation was decreased. The vertical sorting of bed materials composed of mixed sediment in the sediment box was observed. The surface layer was composed of gravels, and uniform sand material was buried below it. Relative fractions (Di/D50) of the bed material trapped in the box was nearly 1.0 for the bed material coarser than D$_{50}$ at Hyundo gauging station, and was between two values on the bed surface before and after the flushing flow at Bugang gauging station. Ratio of driving force to resisting force for each fraction ($\tau_i^*$) with the faction size maintained constant for the bed material coarser than D$_{50}$ at Hyundo station. At Bugang station, however, it was rapidly decreased. It means that pavement of the surface layer of bed material at Bugang station was developed, with the sediment particles moving downstream uniformly by flushing flow.

• The Korean Journal of Ecology
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• v.14 no.4
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• pp.399-413
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• 1991

Benthic macroinvertebrate communities and environments at the upper and lower sites of levees in the middle reaches of paenae stream, a tributary of the naktong river,were investigated in four seasons from August 1989 to may 1990. Current velocities were significantly fast at the loer sites than the upper sites of levees. Substratum compositions were also different between these two sites. Abundances of major species of benthic macroinvertebrates occurring in four seasons were primarily dtermined by temperature. in each location of levees, however, current velocities and substratum particle sizrs were important in determining species were generally higher than upper sites of levees. Biological indices were also high at the lower sites of levees. diversity, evenness and dominance indices were positively correlated with the quantity of the middle-sized large pebbles(3∼5cm in diameter) in stream bed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.E
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• pp.55-62
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• 1995

The topographic influences for the hydraulic characteristics in the estuary were studied by the hydraulic model test. The upstream boundary is set up at the Kumkang estuary dike and the downstream boundary at the Kunsan outer port. The geometrical model scales in horizontal and vertical are 1/300 and 1/100 respectively so that the distorted ratio is 3. If there is no or little river flow through the gate, the highest water levels are varied with $\pm$ 5cm compared with those before the project. If there is a flood flow through the gate, the highest water levels in front of the estuary dike are reduced 5~2Ocm depending on the frequency of flood compared with those before the project. This means that there is no important risk of excessive water level rise after the dredging.

• 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.