• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.753-762
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• 2002

In-stream vegetation is an essential element of a stream channel. Vegetation plays an important role in flood control and the natural environment in stream channels. This research investigates the relationship between in-stream vegetation and stream changes. This study investigates the distribution characteristic of vegetation in some rivers of Korea. Although there are many physical factors that cause changes to streams, this research verified that in-stream vegetation caused sediment deposition. A hydraulic model experiment was conducted. Tests were conducted in a simulated gravel bed stream (bed slope 1/200) with Phragmites japonica. The average diameter of the bed load used was 0.3 mm and 27 kg were uniformly supplied for 1 hour under same hydraulic conditions. The deposition and scouring as well as the change of flow differed according to the density and arrangement of the Phragmites japonica. In-stream vegetation and stream channel change are closely related because deposition and scouring affects the distribution of vegetation.

• Journal of Wetlands Research
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• v.5 no.1
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• pp.53-66
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• 2003

The subject of sediment transport has been studied for centuries by engineers and river morpohologists. Many of the complex aspects of sediment transport are yet to be understood, and remain among the challenging subject for future studies. In this study, the finite element model is applied to various hypothetical channels. On the basis of the flow analysis results, sediment transport analysis is conducted using 3-different optional equations, and the results are compared with experimental results. For the purpose of predicting the sediment movements in natural river, RMA model is applied to Geum-River. It turned out to be very effective tool to predict various aspects of river evolution and the effects of hydraulic structures. The simulation results are also linked to the Geographic Information Systems (GIS).

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.154-159
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• 2001

Nakdong estuary is located at south-eastern coast of the Korea. A lot of sediment from upper river was deposited at this area. It has caused many problems such as changes in topography and tidal current. In this paper, field observation data on tidal currents and sediments were investigated as well as historical topographic changes by dredging and reclamation of the foreshore. Then, the numerical model considered the settling velocity of the suspended solids according to the particle size was applied to examine the characteristic of deposition. The results are as follows : 1. Changes of characteristics of deposition were caused by topographic changes of Nakdong estuary 2. Characteristics of deposition were influenced by river plume and tidal currents. 3. Numerical model which considers settling velocity reappeared distribution of deposition by particle-size. 4. Used model is only resonable for discussion in the quality, so, it is strongly suggested that the new model development is needed including the quatitative deposition processes.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.132-143
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• 2017

It is essential to obtain periodic sediment discharge data in a river in order to minimize problems that may arise from the erosion, transport, and deposition of sediment. However, it is difficult to estimate sediment discharge by the sediment discharge measurement plan in Korea at present, and empirical fomulas or numerical models are used to replace them. This paper has applied the K-DRUM model, a grid-based rainfall-runoff-sediment model, to estimate sediment discharge and ensure the continuity of the data in the watershed. Discharge and sediment load in 17 watersheds were estimated and the applicability of the model was analyzed through comparisons with measured data. For quantitative evaluation, NSE, PBIAS and RSR items were used, and discharge results reflected the tendency of rainfall and showed high statistical value. In case of sediment discharge, the soil erosion process of the watershed is physically well reflected. When the calibration was performed using the measure data, the applicability seems to be excellent in estimating the continuous sediment discharge data in the real watershed.

• Journal of the Korean Professional Engineers Association
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• v.3 no.10
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• pp.7-17
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• 1970

Fourteen reservoirs maintained by the local land improvement associations in the province of Chullabuk-Do and 20 reservoirs maintained by those in the province of Chullanam-Do, were surveyed in connection with a correction between storage capacity and sediment deposit. In addition to this survey, 3347 of small scale reservoirs, that lie scattered around in the above mentioned two provinces were investigated by using existing records pertaining to storage capacity in the office of City and Country, respectively. According to this inrestigation. the following conclusions are derived. 1. A sediment deposition rate is high, being about 10.63m$^3$/ha of drainage area, and resulting in the average decrease of storage capacity by 27.5%. This high rate of deposition could be mainly attributed to the severe denudation of forests due to disorderly cuttings of trees. Especially, in small scale reservoirs, an original average design storage depth of 197mm in irrigation water depth is decreased to about 140mm. 2. An average unit storage depth of 325.6mm as the time of initial construction is decreased to 226mm at present. This phenomena causes a greater shortage of gation water, since it was assumed that original storage quantity itself was already in short.

• Journal of Radiation Protection and Research
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• v.28 no.4
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• pp.353-360
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• 2003

The concentration of $^{137}Cs$, the particle size, and the contents of TOC, H, N and S were measured for sediments collected in the adjacent sea to Yangnam, Korea. The concentrations of $^{137}Cs$ in sediments are in the range of $^{137}Cs$ for sediments strongly depend on particle size and TOC content of sediments. The results of multiple regression analysis suggest that humic substances may have great influence on the deposition of $^{137}Cs$ in sediment.

• Water Engineering Research
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• v.2 no.3
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• pp.179-185
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• 2001

The time consuming and expensive nature of experimental research on scouring processes caused by flowing water makes it attractive to develop numerical tools for the predication of the interaction of the fluid flow and the movable bed. In this paper the numerical simulation of scour by a wall jet is presented. The flow is assumed to be two-dimensional, and the alluvium is cohesionless. The solution process, repeated at each time step, involves simulation of a turbulent wall jet flow, solution of the convection-diffusion of sand concentration, and prediction of the bed deformation. For simulation of the jet flow, the governing equations for momentum, mass balance and turbulent parameters are solved by the finite volume method. The SIMPLE scheme with momentum interpolation is used for pressure correction. The convection-diffusion equation is solved for sediment concentration. A boundary condition for concentration at the bed, which takes into account the effect of bed-load, is implemented. The time rate of deposition and scour at the bed is obtained by solving the continuity equation for sediment. The shape and position of the scour hole and deposition of the bed material downstream of the hole appear realistic.

• Fisheries and Aquatic Sciences
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• v.13 no.2
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• pp.167-181
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• 2010

To predict changes in the marine environment of the Beolgyo Stream Estuary in Jeonnam Province, South Korea, where cohesive tidal flats cover a broad area and a large bridge is under construction, this study conducted numerical simulations involving tidal flow and cohesive sediment transport. A wetting and drying (WAD) technique for tidal flats from the Princeton Ocean Model (POM) was applied to a large-scale-grid hydrodynamic module capable of evaluating the flow resistance of structures. Derivation of the eddy viscosity coefficient for wakes created by structures was accomplished through the explicit use of shear velocity and Chezy's average velocity. Furthermore, various field observations, including of tide, tidal flow, suspended sediment concentrations, bottom sediments, and water depth, were performed to verify the model and obtain input data for it. In particular, geologic parameters related to the evaluation of settling velocity and critical shear stresses for erosion and deposition were observed, and numerical tests for the representation of suspended sediment concentrations were performed to determine proper values for the empirical coefficients in the sediment transport module. According to the simulation results, the velocity variation was particularly prominent around the piers in the tidal channel. Erosion occurred mainly along the tidal channels near the piers, where bridge structures reduced the flow cross section, creating strong flow. In contrast, in the rear area of the structure, where the flow was relatively weak due to the formation of eddies, deposition and moderated erosion were predicted. In estuaries and coastal waters, changes in the flow environment caused by artificial structures can produce changes in the sedimentary environment, which in turn can affect the local marine ecosystem. The numerical model proposed in this study will enable systematic prediction of changes to flow and sedimentary environments caused by the construction of artificial structures.

• 한국해양학회지
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• v.18 no.1
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• pp.21-28
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• 1983

A series of experiments was performed to increase and make our puantitive understanding of the entrainuent and settling processes of fine-grained sediments, which are of critical importance to construct a predictive model of sediment experiments were performed in an annular flume. A rotating top produced a turbulent flow which in turn exerted and are shown to be dependent on the sediment concentration and the presence of clay minerals. The parameters on which entrainment strongly depends were identified to be the shear stress, water content (time ofter deposition), and the type of sediment (grain size and mineralogy).

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.196-196
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• 2016

Landslide dam failure presents as a severe natural disaster due to its adverse impact to people and property. If the landslide dams failed, the discharge of a huge volume of both water and sediment could result in a catastrophic flood in the downstream area. In most of previous studies, breaching process used to be considered as a constructed dam, rather than as a landslide dam. Their erosion rate was assumed to relate to discharge by a sediment transport equation. However, during surface erosion of landslide dam, the sediment transportation regime is greatly dependent on the slope surface and the sediment concentration in the flow. This study aims to accurately simulate the outflow hydrograph caused by landslide dam by overtopping through a 2D surface flow erosion/deposition model. The lateral erosion velocity in this model was presented as a function of the shear stress on the side wall. The simulated results were then compared and it was coherent with the results obtained from the experiments.