• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.4
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• pp.85-93
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• 1998

In the 2nd year study of a 5 year project to evaluate the soil quality and develop the best management practices for mountaineous soils, 11 runoff plots were treated and monitored with respect to physical property of the soil, runoff and sediment discharge, and the following results were obtained. 1. Bulk density and porosity did not show any siginificant difference between experimental treatments. 2. Runoff was basically dependent on the soil's physical property and tillage. Up-and-down plots showed the highest runoff while contour plots the lowest runoff. 3. Sediment yield in the mountaineous soils was directly related to tillage and residue cover. Residue covered plots showed the lowest sediment yield and up-and-down plots the highest sediment yield. And it is recommended that the best management practices using till_age and residue cover for the mountaineous soils must be developed to protect soil quality and maintain agricultural productivity.

• Water for future
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• v.29 no.3
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• pp.129-142
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• 1996

This study investigates the magnitude of errors that can be expected in integrating sediment concentration in a vertical, basede on a single-point measurement, because of errors in input data. Potential error sources, including sampler location, water surface elevation, bed elevation, fall velocity, $\beta$ value, and $\kappa$ value were comparatively examined using data from a special study on the Rio Grande Conveyance channel in New Mexico. It is concluded that simple forms of equations for the vertical distribution of velocity and sediment concentration based on a single-point field sample of suspended sediment. The most uncertain point in the computation is related to the Rouse number z in the equation for the vertical concentration distribution of suspended sediment.

• International Journal of Ocean System Engineering
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• v.2 no.2
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• pp.71-81
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• 2012

Several methods have been proposed to control the sedimentation process. These include catchment management, flushing, sluicing, density current venting, and dredging. Flushing is used to erode previously deposited sediments. In pressurized flushing, the sediment in the vicinity of the outlet openings is scoured and a funnel shaped crater is created. In this study, the effect of localized vibrations in the sediment layers on the dimensions of the flushing cone was investigated experimentally. For this purpose, experiments were carried out with two bottom outlet diameters, five discharge releases for each desired water depth, and one water depth above the center of the bottom outlets. The results indicate that the volume and dimensions of the flushing cone are strongly affected by localized vibrations.

• 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 Korean Society of Coastal and Ocean Engineers
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• v.14 no.2
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• pp.108-115
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• 2002

Pollutants discharge modeling was carried out in the watershed of Mankyung and Dongjin rivers. The watershed and pollutants source information extracted and analysed by the GIS tool was used as the model input parameters. This model was calibrated by comparison of the measured and computed monthly freshwater discharge and water quality(WQ) concentration. The compared WQ data are the ten-year-mean WQ concentration and monthly WQ concentration in 1999. The results show that the watershed runoff is underestimated in summer season, although the seasonal trends are relatively well estimated. The WQ concentrations were also relatively well estimated except Iksancheon. The computed concentration was much lower than the observed concentration in Iksancheon because of the effect of polluted sediment. Thus, the effects of polluted sediment on water column need further study through measuring and analysing the degree of the sediment contamination.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.3
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• pp.127-136
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• 1996

The purpose of this study is to provide with information for the water resources development and management in stream management planning, such as information on the sediment trensport, design of dam and water facilities, river improvement and flood plains management. The major results obtained from the field measurement and analysis of the watershed characteristics, hydraulic and sediment characteristics are as follows ; 1. The rating curve formulas obtained from the analysis of the hydraulic characteristics data collected are ; Q-=110.563 $(H-0.474)^2$ for 0.7m$(H-0.146)^2$ for 0.4m$Sr=aX{^2} {_1} X^{c}{_2}$, in the experimental watershed.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.728-733
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• 2002

The measurement of river discharge is among the most fundamental observations and is necessary for understanding many water-related issues, such as flooding hazards, sediment transportation, and nutrient movement. Traditionally river discharge is estimated by measuring the water stage and converting the measurement to discharge using a stage-discharge rating curve. The possibility of monitoring river discharge from satellites has been largely ignored, because it is difficult to measure water surface information from space with sufficient precision. In this paper, an efficient approach to discharge estimation using mainly satellite data is developed and described. The proposed method, which focuses on the measurement of water-surface width coupled with river width-stage and stage-discharge relationships, is applied to the Yangtze River with good results.

• Korean Journal of Environmental Agriculture
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• v.19 no.3
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• pp.201-205
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• 2000

Eleven runoff $plots(3{\times}15\;m)$ were built on a sloping field of a high plateau in Kangwon Province, Korea. The plots were treated with different tillage, residue covers and fertilizers, corn and potato were cultivated, and sediment discharge was measured from the plots for 3 years. Agricultural management practices were monitored around the plots to develop adequate best management practices. The least sediment occurred from the plots with no-till and 100% residue cover $(corn,\;0.1{\sim}2.2\;t/ha/year)$ and with contour tillage and vinyl sheet cover plots $(potato,\;0.1{\sim}0.2\;t/ha/year)$. The largest sediment was measured from the plots with up-and-down till and no cover ($11{\sim}33$ and $16{\sim}31\;t/ha/year$ from corn and potato plots, respectively). The type of organic and commercial fertilizers seemed not to affect sediment discharge. Sediment discharge from contour plots were largely dependent on the collapse of ridges due to the flush of water stored in furrows. The sediment discharge from contour corn and potato plots with no residue cover was $10{\sim}27$ and $16{\sim}24\;t/ha/year$, respectively. No-till with residue cover, vinyl cover for tuber crops, construction of furrow dam, frost heave research, furrow and ridge tillage with furrow dam after tuber crop harvest, limited stalk harvest of row crops, use of winter cover crops, and other common best management practices were recommended to minimize the sediment discharge from a high plateau sloping land culture.

• Journal of Korean Society of Forest Science
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• v.88 no.4
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• pp.477-484
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• 1999

This study was conducted to investigate the effect of forest road on the suspended sediment yield into a stream in the small forest watershed. The samples of suspended sediment yield were collected at surveying points A and B in mountains watersheds unaffected by forest road, and at surveying point C affected by forest road. When hourly change of suspended sediment concentration was investigated, it showed the highest increase along the forest road, and the peak of suspended sediment concentration due to the watershed characteristics of each surveying point occurred before or at the same time with, the peak of discharge. This may be due to the time lag in which stagnated unstable suspended sediment moved strongly upon rainfall. Although suspended sediment load varied depending upon rainfall factors and surveying period, suspended sediment load per unit watershed flowed out 4.1 times more at the point C than at the point A and B. The suspended sediment load on 18~19 September, 1998, strongly affected by rainfall factors, was 4.179g/sec/㏊ at the point C, and 0.343g/sec/㏊ and 0.147g/sec/㏊ at the point A and B, respectively. This load was 12 times higher at the point C than at the point A and 28 times higher than at the point B.

• 한국해양학회지
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• v.30 no.3
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• pp.147-162
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• 1995

The circulation due to tidal current and river discharge, and the associated suspended suspended sediment transport in macrotidal Keum Estuary, were studied through a series of field measurements of tidal currents and suspended sediment concentration at three anchored stations from 1990 through 1992. From the measurements, the following results were obtained. At the seaward entrance of the estuary, the veritical profiles of the ebb and flood currents were almost symmetric. At the southern channel the flood current was dominant in the whole water column, but in the northern channel the ebb current was dominant in the surface and bottom layers and the flood current was dominant in the intermediate layer. The maximum velocity of the tidal current in the southern channel was 174 cm/s during flood tide in the intermediate layer. The maximum velocity, 148 cm/s in the northern channel also appeared during flood tide in the intermediate layer. However, in the surface and bottom layers, the maximum velocities were 110.6 cm/s during ebb tide and 92.1 cm/s during flood tide, respectively. The type of the Keum Estuary can be categorized to 'Type 3' of Hansen and Rattray's scheme. The water column of the estuary during the flood tide becomes stratified, and after high water the ebb current reduces the density difference and the water column becomes turbulent. The lower layer of the water column is generally turbulent. The largest sediment flux 20.61 ton/s was found in the southern channel during flood current in the lowest river discharge (May, 1991), while the smallest flux, 0.65 ton/s in the northern channel in the lowest tidal range (July, 1992). The stronger bottom shear velocity for the present study area seems to erode the bottom sediments during the flood tide, and the relatively long duration of the ebb tide to transport the suspended sediments. Under normal river discharge conditions, the suspended sediments are transported mainly through the southern channel. However, under high river discharge condition the suspended sediment transport is dominant through the northern channel.