• Journal of Korea Water Resources Association
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• v.51 no.3
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• pp.183-193
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• 2018

Channel-forming discharge for downstream section of Yeongju dam in Naesung stream was calculated to analyze stable channel geometry. Determined channel-forming discharge was applied to design stable channel slope, depth, and base width at Yonghyeol station. Used data for channel-forming discharge and stable channel analysis were collected in downstream section of Yeongju dam in Naesung stream before the dam construction. Specified recurrence interval discharge, effective discharge, and bankfull discharge were analyzed and compared to decide final channel-forming discharge which was $260m^3/s$ of bankfull discharge. Stable channel analysis and design program was applied to predict stable channel section of width, depth, and slope with various sediment transport equations of Ackers and White, Brownlie, Engelund and Hansen, and Yang's equations. As a result, all equations of sediment transport produced milder slopes compared to current bed slope of 0.00177 and Ackers and White equation presented the most similar flow depth of current section with the design constraint of current channel width.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.167-167
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• 2020

Annual sediment deposition in reservoirs behind weirs poses flood risk, while its accurate prediction remains a challenge. Sediment management by hydraulic flushing is an effective method to maintain reservoir storage. In this study, an integrated approach to predict sediment inflow and sediment flushing simulation in reservoirs is presented. The annual sediment inflow prediction was carried out with Artificial Neural Networks (ANN) modelling. RESCON model was applied for quantification of sediment flushing feasibility criteria. The integrated approach was applied on Sangju Weir and also on estuary of Nakdong River (NREB). The mean annual sediment inflow predicted at Sangju Weir and NREB was 400,000 ㎥ and 170,000 ㎥, respectively. The sediment characteristics gathered were used to setup RESCON model and sediment balance ratio (SBR) and long term capacity ratio (LTCR) were used as flushing efficiency indicators. For Sangju Weir, the flushing discharge, Q_f = 140 ㎥/s with a drawdown of 5 m, and flushing duration, T_f = 10 days was necessary for efficient flushing. At NREB site, the parameters for efficient flushing were Q_f = 80 ㎥/s, T_f = 5 days, N = 1, El_f = 2.24 m. The hydraulic flushing was concluded feasible for sediment management at both Sangju Weir and NREB.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.86-86
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• 2022

While estuarine dams can develop freshwater resources and block the salt intrusion, they can result in increased sediment deposition in the estuary. The mechanism of increased sediment deposition in an estuary with an estuary dam is not well understood. To fill this knowledge gap, 7 ADCP measurements of flow and suspended sediment concentration (SSC) were collected along-channel in an estuary with an estuarine dam over a neap-spring cycle. Flow and SSC were used to calculate the sediment flux and sediment flux gradients. The results indicated that the cumulative sediment fluxes at all stations were directed landward. The along-channel sediment flux gradient was negative, which indicated deposition along the channel. The landward mean-flow fluxes were dominant in the deep portion of the channel near the estuary mouth, whereas landward correlation fluxes were dominant in the shallow portion of the channel near the estuarine dam. The tides were the dominant forcing driving the sediment fluxes throughout the estuary.

• Ocean Systems Engineering
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• v.12 no.4
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• pp.403-411
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• 2022

Annually, about 48-60% of sediment discharge of the Mekong River is delivered near the mouths of the Mekong River branches which is mostly coinciding with the southwest (SW) monsoon. This sediment budget in turn will be southwestwardly transported along the coast of the Mekong Delta (MD) during the northeast (NE) monsoon. Analysis of monsoonal changes in grain-size distribution (GSD) of surface sediment contributes to a better understanding of erosion and deposition processes along the MD. This study aims to figure out changes in GSD and sediment textures along the MD between SW and NE monsoons based on 183 surficial sediment samples collected along the MD during two field surveys carried-out in October 2016 and February-March 2017. Compared to the GSD during the SW and NE monsoon, the GSD along the MD changed significantly, especially in the estuary areas and along the coast of Bac Lieu and Ganh Hao. Whereas, in the west coast of the MD, GSD seem no changes between the two seasons. These changes in seabed sediment suggest that sediment with grain-sizes ranging from silt to fine sand can be transported during only a NE season.

• The Journal of the Korea Contents Association
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• v.15 no.8
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• pp.544-555
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• 2015

This study aims to derivate of the relationship and rating curve for the flow discharge-total sediment using the measured field data from the main points of small-medium stream reaches in agrarian basin. The total sediment of measured data are obtained by bed load added to suspended load which analyzed using the particle size distribution curve of sieve test and the dry or the filtration method from the collected samples by samplers (DH-48, D-74 and BLH-84, BL-84) at the stream bed and the depth-averaged concentration, respectively. These field data had been collected from August 2012 to September 2014 at the seven measuring stations of the national-local channel reaches of the four study streams in the Nonsan river systems of agrarian basin. As a result, the relationships and the rating curve for the flow discharge-total sediment are derived as a function pattern of power law by analyzing on a distribution characteristic of the database set and it will be used as a useful tool to analyze erosion, deposition, and transportation in theoretical research as well as in practical application of the hydraulic sedimentation engineering.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.2
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• pp.95-102
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• 2012

The objective of this research was to experimentally test the effect of rice straw mats on the reduction of runoff, sediment discharge and turbidity under a laboratory scale. We used the small runoff plots of 1 m ${\times}$ 1 m ${\times}$ 0.65 m ($L{\times}W{\times}H$) in size filled with loamy sand. Experimental treatments were bare (control), rice straw mat cover of straw mats + PAM + Gypsum (SPG), rice straw mats + Chaff + PAM + Gypsum (SCPG) and rice straw mats + Sawdust + PAM + Gypsum (SSPG); slope of 10 % or 20 %; and rainfall intensity of 30 mm/hr. Runoff volume and rate of covered plots were significantly lower than those of control plot. Average runoff rate of covered plots, slope of 10 % and 20 %, decreased 85.6 % and 72 % in respectively. Sediment reduction ratio was more than 99 % regardless of slope. The differences runoff and sediment discharge among different cover materials were not significant. It was also shown that even if runoff reduction by surface cover were low, sediment discharge reduction could be very significant and contribute to improve the water quality of streams in sloping agricultural regions. It was concluded that the use of straw mat and soil amendments (PAM and Gypsum) on sloping agricultural fields could reduce soil erosion and muddy runoff significantly and help improve the water quality and aquatic ecosystem in receiving waters. But mixing effect of PAM and Gypsum was minimal.

• Water for future
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• v.24 no.2
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• pp.71-79
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• 1991

Some selected hydraulic characteristics including the average velocitv, geometry of the channel cross-section, and water temperature, and sediment-characteristics including suspended sediment concentration , and the size distributions of suspended and bed-sediments were collected at two measuring stations in the Cheongmi-Stream during a flood period. The river bed investigated for this study is composed completely of sands, and it can be considered a typical alluvial channel. The major results obtained from the analysis of the date collected are as follows: 1) Only during floods, a substantial sediment transport occurs in the river; 2) The stage-discharge relations are changed frequently, especially for low flows; 3) The friction in the flow increases with an increase in the flow discharge; 4) Slits and clays are dominant in suspended sediments during normal flows, while sands are dominant during floods; 5) The vertical distributions of the flow velocity and suspended sediment concentration can be described, respectively, by Prandt1-von Karman's log-law and Rouse's exponential law. It is judged that the above results are commonly adapted for other alluvial rivers, although they were obtained from a limited number of data collected from a specific river reach.

• Journal of Korea Water Resources Association
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• v.30 no.5
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• pp.561-570
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• 1997

The feature of this paper is (1) to analyze the characteristics of rainfall-runoff relationship with kinematic wave theory, (2) to study the computational model to estimate the sediment yield, (3) to analyze the effects of bed change by transport formulas and the number of watershed division, and (4) to verify the model application with observation of channel data and measurement of rainfall, runoff, sediment discharge in Pyung-Chang River Basin. The calculated time of concentration of peak discharge occured little earlier than the actual, but the tendency of hydrograph coincided with observation. The shape of sediment hydrographs was similar to the water hydrograph. Based on above results, the applicability of the model was verified in detail. As the number of watershed division increased, the difference between the measured runoff and sediment values and the estimated ones decreased. The result of calculation with Yalin's formula for surface and Acker-White's one for channel gave the best agreement with the measured data among the six selected sediment transport foumulas.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.11a
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• pp.205-208
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• 2006

• Proceedings of the Korea Water Resources Association Conference
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• 1995.05a
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• pp.27-33
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• 1995