• Title/Summary/Keyword: Suspended sediment

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Surface Sediment and Suspended Material in Deukryang Bay (득량만의 퇴적물 및 부유물 특성)

  • 공영세;이병걸
    • 한국해양학회지
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    • v.29 no.3
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    • pp.269-277
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    • 1994
  • Process of resuspension and accumulation well explaines the characteristics of surface sediment size distribution and suspended material in Deukryang Bay. Most of the surface sediments of the bay show asymmetric unimodal size distribution, which is found also in sediments from western part of the inner shelf mud area between Keomundo and Yokchido islands. Investigation of the size curves indicates that surface sediment in Deukryang Bay is a deposit of suspended coastal sediment transported east along southern coast of Korea. The distribution pattern of coarse sit fraction content in the surface sediment is very similar to that of computed current velocity (Lee, 1994), suggesting that fine sediment on the bed may reassumed and accumulate repeatedly due to shallow depth and strong tidal current in Deukryang Bay. The process of repeated resuspension and accumulate repeatedly due to shallow depth and strong tidal current in Deukryang Bay. The process of repeated resuspension and accumulation seems to be responsible not only to the asymmetric size distribution of the surface sediment, but also to the amount of suspended material in the bay. The difference of suspended material concentration between surface and near bottom water in summer is two times as large as that the in winter. This seems to derive from the fact that stratification of water mass prevails in summer, while total water mass is vertically mixed in winter. It was found that the most important factors to decide distribution of suspended material in Deukryang Bay are the physical properties of water mass such as current velocity and stratification, and water depth, in part with the supply of suspended sediment by rivers.

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Suspended Sediment Transport Characteristics in the Estuary with Significant Shallow Water Tides and Tidal Flat (천해조 및 조간대가 발달된 하구에서의 부유사이동 특성)

  • 강주환;문승록;안성모
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.14 no.3
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    • pp.201-208
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    • 2002
  • The characteristics of suspended sediment transport are analyzed at the estuaries which show significant shallow water tides, following the previous research for bottom sediment transport at the same estuaries. Several theories which are related with the formation and transition of turbidity maximum are reconfirmed by the numerical experiments. The experiments suggest the necessity of modeling the shallow water tide as a boundary condition, as was also suggested for the bed sediment transport at the previous research. Both the differences of transport characteristics between bed and suspended sediment and the differences between flood/ebb dominances and high/low water dominances are also examined at the Keum River and Youngsan River estuaries. In addition, the transport of bed and suspended sediments are found to have the opposite directions at the Youngsan River estuary which has extensive tidal flat, and thus shows pronounced ebb dominance, which is considered to be a main reason of keeping present bathymetry.

Characteristics of Turbulent Flows and Suspended Sediment Transport in Open-channel with Submerged Vegetation (침수식생 개수로에서 난류 및 부유사 이동 특성)

  • Yang, Won-Jun;Jang, Ji-Yeon;Choi, Sung-Uk
    • Journal of Korea Water Resources Association
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    • v.44 no.5
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    • pp.417-427
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    • 2011
  • The open-channel flow with submerged vegetation shows distinct features in two separate regions, namely upper and vegetation layers. In the upper layer, the flow is akin to the open-channel flow, while the flow in the vegetation layer is relatively uniform with suppressed turbulence due to vegetation stems. This paper presents laboratory experiments to investigate the characteristics of turbulent flows and suspended sediment transport in open-channel flows with submerged vegetation. An open-channel facility, 0.5 m wide and 12 m long, was used for laboratory experiments. Various discharges were employed with depth ratios of 2~3, and wooden cylinders were used for vegetation. To make equilibrium suspension, sediment particles of median diameter of 75 ${\mu}M$ were fed until capacity condition. Laser Doppler velocimeter was used to measure instantaneous velocity, and direct sampling with vinyl tube was used to measure the concentration of suspended sediment. Using the sampled data, the mean flow and turbulence structures were provided and characteristics of suspended sediment concentration with Rouse number were presented.

Study on the Long-term Change of nitrogen in the Tidal Area of River (하천 감조부에 있어서 질소의 장기변동에 관한 연구)

  • 김원규;강주복
    • Water for future
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    • v.25 no.2
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    • pp.67-78
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    • 1992
  • Several field surveys were conducted to investigate changes of water quality with time in a tidal river. Results indicated that nitrification process were dependent on the change of salinity and suspended solids concenttration. Therefore laboratory batch experiments were conducted, using suspended solids and sediment taken from a tidal river, to study the effect of salinity on nitrification and to estimate kinetic parameters of it in the tidal river. suspended solids and sediment were sampled at a point in the middle stream. Sediments were collect from the aerobic layer of mud. The change of nitrogen concentration with time was clearly explained with Monod groth model and kinetic parameters were obtained by curve fitting method. Changes in NH4-N, NO2-N, and NO3-N concentrations in the river ROKKAU with time were simulated well using Lagrangian reference frame and parameter values obtained in the laboratory tests. T도 mechanism of nitrification by suspended solids and sediment in a tidal river is shown to depend on tidal effects.

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Study on the Settling Process of Cohesive Sediment (점착성 퇴적물의 침강특성에 관한 연구)

  • Sin, Dong-Su;Bae, Gi-Seong
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.111-120
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    • 1998
  • Laboratory settling experiments (column, recirculating flume) were conducted for further understanding of the physical processes of cohesive sediment transport. \In still water experiments, the growth rate of flocculation is dependent upon the initial suspended concentration. Consequently, the settling velocity increases with concentration of flees. In flocculation settling regime, the exponent n in the settling velocity, $w_s=kC^n$, for Nakdong estuary mud was obtained empirically. The exponents were found to be 1.33, and 1.06 for the initial suspended concentrations of 1 g/i and 3 g/t, respectively. In flowing water, experiments for the median settling velocity with Nakdong mud in a recirculating flume were conducted. Settling velocity was found to depend much more strongly on the current velocity than initial concentrations. The temporal variation of suspended concentration increases as current velocity decreases.

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The Distribution and Behaviors of Suspended Matters in Seomjin River Estuary - Compared with Rainy and Wet Season - (섬진강하구에서 부유물질의 분포와 거동 - 풍수기와 평수기의 비교 -)

  • Kim, Seok-Yun;Lee, Byoung Kwan
    • Journal of Korean Society on Water Environment
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    • v.25 no.6
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    • pp.935-942
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    • 2009
  • During period of the rainy season of spring tide Aug. 2005, the suspended sediment transport rate from Seomjin River increased ten times as high as neap tide of low river discharge. During ebb tide of high terrestrial input, the grain size of suspended particles of both surface and bottom layer of the water column, showed a uni-modal distribution with a dominant peak at coarse fraction, which suggests a characteristic development of floc-sized particles of low mean effective density. On the contrary, the particles supplied toward upstream of Seomjin river from Gwangyang Bay during flood tide showed a bi-modal distribution with a secondary peak at finer fraction, possibly due to the resuspension and the deflocculation associated with the increased shear velocity at near bottom. Break-up of large flocs is also suggested by the increased mean effective density. However, settling velocity was lower during flood tide because of smaller grain size. Thus, net deposition of suspended sediment is expected at within Gwangyang Bay instead of upstream of Seomjin River, even though suspended sediment transport rate at near bottom water was three times higher than that at surface water during flood tide.

Estimating magnitude of suspended sediment transport in ungauged east coastal zone (미계측 동해안 유역의 토사유출 규모의 평가에 관한 연구)

  • Lee, Sangeun;Kang, Sanghyeok
    • Journal of Korea Water Resources Association
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    • v.51 no.2
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    • pp.175-182
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    • 2018
  • Coastal sediment archives are used as indicators of changes on shore sediment production and fluvial sediment transport, but rivers crossing coastal plains may not be efficient conveyors of sediment to the coast. In some case there is a net loss of sediment in lower coastal plain reaches, so that sediment input from an upstream exceeds the sediment yield (SY) at the river mouth. The main source of sediment in coastal area is the load from land. In Korea, data on suspended SY are limited owing to a lack of logistic support for systematic sediment sampling activities. This paper presents an integrated approach to estimate SY for ungauged coastal basins, using a soil erosion model and a sediment delivery ratio (SDR) model. For applying the SDR model, a basin specific parameter was validated on the basis of field data. The proposed relationships may be considered useful for predicting suspended SY in ungauged basins that have geologic, climatic and hydrologic conditions similar to the study area.

A SVR Based-Pseudo Modified Einstein Procedure Incorporating H-ADCP Model for Real-Time Total Sediment Discharge Monitoring (실시간 총유사량 모니터링을 위한 H-ADCP 연계 수정 아인슈타인 방법의 의사 SVR 모형)

  • Noh, Hyoseob;Son, Geunsoo;Kim, Dongsu;Park, Yong Sung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.43 no.3
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    • pp.321-335
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    • 2023
  • Monitoring sediment loads in natural rivers is the key process in river engineering, but it is costly and dangerous. In practice, suspended loads are directly measured, and total loads, which is a summation of suspended loads and bed loads, are estimated. This study proposes a real-time sediment discharge monitoring system using the horizontal acoustic Doppler current profiler (H-ADCP) and support vector regression (SVR). The proposed system is comprised of the SVR model for suspended sediment concentration (SVR-SSC) and for total loads (SVR-QTL), respectively. SVR-SSC estimates SSC and SVR-QTL mimics the modified Einstein procedure. The grid search with K-fold cross validation (Grid-CV) and the recursive feature elimination (RFE) were employed to determine SVR's hyperparameters and input variables. The two SVR models showed reasonable cross-validation scores (R2) with 0.885 (SVR-SSC) and 0.860 (SVR-QTL). During the time-series sediment load monitoring period, we successfully detected various sediment transport phenomena in natural streams, such as hysteresis loops and sensitive sediment fluctuations. The newly proposed sediment monitoring system depends only on the gauged features by H-ADCP without additional assumptions in hydraulic variables (e.g., friction slope and suspended sediment size distribution). This method can be applied to any ADCP-installed discharge monitoring station economically and is expected to enhance temporal resolution in sediment monitoring.

ChlorophyII and suspended sediment specific absorption coefficient in the sea.

  • Ahn, Yu-Hwan;Moon, Jeong-Eon
    • Proceedings of the KSRS Conference
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    • 1998.09a
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    • pp.399-403
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    • 1998
  • Absorption coefficient per mass unit of particles, specific absorption coefficient, is one of main parameters in developing algorithms for ocean color remote sensing. Specific absorption coefficient of chlorophyll (a$^*_{ph}$) and suspended sediment (SS) were analyzed by "wet filter technique" and "Kishino method" for data sets observed in the Yellow and Mediterranean Seas. A new data-recovering method for the filter technique was also developed using spectrum slopes. This method recovered the baseline of spectrum that was often missed in the Kishino method. High a$^*_{ph}$($\lambda$) values in the oligotrophic Mediterranean Sea and low values in the Yellow Sea were observed, spanning over the range of 0.02 to 0.12 $m^2$/mg, at the chlorophyll maximum absorption wavelength 440nm. The empirical relationship between a$^*_{ph}$ and chlorophyll concentration was found to fit a power function, which was slightly different from that proposed by Bricaud et ai. (1995). Absorption specific coefficients for suspended sediment (a$^*_{SS}$) didn't show any relationship with concentrations of suspended sediment. However, the average value of a$^*_{SS}$ at 440nm was close to the specific absorption coefficient of soil (loess) measured by Ahn (1990). The more-pronounced variability of a$^*_{SS}$ than a$^*_{ph}$ perhaps can explain more wide range of size-distribution for SS, which were determined by their specific gravity and agitation of water mass in the sea surface.

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Characteristics of Surface Sedment and Seasonal Variation of Suspended Sediment in the Masan Bay, South Coast of Korea (한국 남해 마산만의 표층퇴적물 특성과 부유퇴적물의 계절별 변화 양상)

  • Choi, Jae Ung;Woo, Han Jun;Choi, Dong Lim;Lee, Tae Hee
    • Journal of Wetlands Research
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    • v.8 no.3
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    • pp.67-77
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    • 2006
  • Sedimentological investigations on surface and suspended sediments were performed in Masan Bay of the South Sea in order to reveal recent changes in depositional environments concerning anthropogenic influence. Surface sediments had been classified as 3 sediment facies: mud, slightly gravelly mud, and gravelly mud. In general, mud facies with more than 60% of silt is predominant and slightly gravelly mud facies occurs at the watercourse of bay's central area. The silt-dominant mud faices appears to be predominant before and after dredging. Temperature and salinity changes during one tidal cycle for each season suggest that water columns were stratified without vertical mixing regardless of the season due to weak intensity of tide from the effect of geographical features. The effect of freshwater discharge from the land seems to be insignificant. The strongest current was observed during ebb tide in spring and autumn while observed during flood tide in summer and winter. Net sediment flux (fs) and net suspended sediment transport (Qs) for suspended sediment were determined by remaining drift developed here. Net suspended sediment transport loads were seaward with $62.02{\times}10^3kgm^{-1}$, $31.84{\times}10^3kgm^{-1}$ in spring and fall, respectively, and landward with $18.23{\times}10^3kgm^{-1}$, $3.22{\times}10^3kgm^{-1}$ in summer and winter, respectively.

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