Field observations of bedforms in high sediment transport conditions

2000 ◽  
Vol 108 (5) ◽  
pp. 2616-2616
Author(s):  
Anna M. Crawford ◽  
Alex E. Hay
Keyword(s):  
Sediment Transport ◽  
Field Observations ◽  
High Sediment

scholarly journals Morphodynamic Evolution of a Nourished Beach with Artificial Sandbars: Field Observations and Numerical Modeling

2021 ◽  
Vol 9 (3) ◽  
pp. 245
Author(s):  
Cuiping Kuang ◽  
Xuejian Han ◽  
Jiabo Zhang ◽  
Qingping Zou ◽  
Boling Dong
Keyword(s):  
Sediment Transport ◽  
Tidal Current ◽  
Model Simulation ◽  
Morphological Changes ◽  
Current Model ◽  
Beach Nourishment ◽  
Tidal Range ◽  
Coastal Protection ◽  
Field Observations ◽  
One Year

Beach nourishment, a common practice to replenish an eroded beach face with filling sand, has become increasingly popular as an environmentally friendly soft engineering measure to tackle coastal erosion. In this study, three 200 m long offshore submerged sandbars were placed about 200 m from the shore in August 2017 for both coastal protection and beach nourishment at Shanhai Pass, Bohai Sea, northeastern China. A series of 21 beach profiles were collected from August 2017 to July 2018 to monitor the morphological changes of the nourished beach. Field observations of wave and tide levels were conducted for one year and tidal current for 25 h, respectively. To investigate the spatial-temporal responses of hydrodynamics, sediment transport, and morphology to the presence of three artificial submerged sandbars, a two-dimensional depth-averaged (2DH) multi-fraction sediment transport and morphological model were coupled with wave and current model and implemented over a spatially varying nested grid. The model results compare well with the field observations of hydrodynamics and morphological changes. The tidal range was around 1.0 m and the waves predominately came from the south-south-east (SSE) direction in the study area. The observed and predicted beach profiles indicate that the sandbars moved onshore and the morphology experienced drastic changes immediately after the introduction of sandbars and reached an equilibrium state in about one year. The morphological change was mainly driven by waves. Under the influences of the prevailing waves and the longshore drift toward the northeast, the coastline on the leeside of the sandbars advanced seaward by 35 m maximally while the rest adjacent coastline retreated severely by 44 m maximally within August 2017–July 2018. The model results demonstrate that the three sandbars have little effect on the tidal current but attenuate the incoming wave significantly. As a result, the medium-coarse sand of sandbars is transported onshore and the background silt is mainly transported offshore and partly in the longshore direction toward the northeast. The 2- and 5-year model simulation results further indicate that shoreline salient may form behind the sandbars and protrude offshore enough to reach the sandbars, similar to the tombolo behind the breakwater.

High Efficient Sediment-Transport Water Volume in High Sediment-Laden River

2011 ◽  
Vol 214 ◽  
pp. 265-270
Author(s):  
Jun Yan ◽  
Biao Liang ◽  
Hui Cao ◽  
Yu Hua Zhang
Keyword(s):  
Sediment Transport ◽  
Transport Process ◽  
Field Data ◽  
Yellow River ◽  
Water Volume ◽  
The Lower Yellow River ◽  
Calculating Method ◽  
High Efficient ◽  
Xiaolangdi Reservoir ◽  
High Sediment

Analyzed the sediment-transport process in high sediment-laden river, the new concept and calculating method for sediment-transport water volume are proposed. Based on field data of sediment and water volume in the Lower Yellow River from 1950 to 2000, the sediment-transport water volume and unit sediment-transport water volume in LYR are calculated. Meanwhile, relations between them and influencing factors are confirmed to calculate efficient sediment-transport water volume after construction of the Xiaolangdi reservoir.

scholarly journals Numerical Simulations of the 2004 Indian Ocean Tsunami Deposits Thicknesses and Emplacements

2018 ◽  
Author(s):  
◽  
Musa Al'ala ◽  
Hermann M. Fritz ◽  
Mirza Fahmi ◽  
Teuku Mudi Hafli
Keyword(s):  
Sediment Transport ◽  
Indian Ocean ◽  
Numerical Simulations ◽  
Field Data ◽  
Numerical Models ◽  
Indian Ocean Tsunami ◽  
Tsunami Deposit ◽  
Field Observations ◽  
Tsunami Deposits ◽  
2004 Indian Ocean Tsunami

Abstract. After more than a decade of recurring tsunamis, identification of tsunami deposits, a part of hazard characterization, still remains a challenging task not fully understood. The lack of sufficient monitoring equipment and rare tsunami frequency are among the primary obstacles that limit our fundamental understanding of sediment transport mechanisms during a tsunami. The use of numerical simulations to study tsunami-induced sediment transport was rare in Indonesia until the 2004 Indian Ocean tsunami. This study aims to couple two hydrodynamic numerical models in order to reproduce tsunami-induced sediment deposits, i.e., their locations and thicknesses. Numerical simulations were performed using the Cornell Multi-Grid Coupled Tsunami Model (COMCOT) and Delft3D. This study reconstructed tsunami wave propagation from its source using COMCOT, which was later combined with Delft3D to map the location of the tsunami deposits and calculate their thicknesses. Two Dimensional-Horizontal (2DH) models were used as part of both simulation packages. Lhoong, in the Aceh Besar District, located approximately 60 km southwest of Banda Aceh, was selected as the study area. Field data collected in 2015 and 2016 validated the forward modeling techniques adopted in this study. However, agreements between numerical simulations and field observations were more robust using data collected in 2005, i.e., just months after the tsunami (Jaffe et al., 2006). We conducted pit (trench) tests at select locations to obtain tsunami deposit thickness and grain size distributions. The resulting numerical simulations are useful when estimating the locations and the thicknesses of the tsunami deposits. The agreement between the field data and the numerical simulations is reasonable despite a trend that overestimates the field observations.

scholarly journals Flow modelling to estimate suspended sediment travel times for two Canadian Deltas

2000 ◽  
Vol 4 (3) ◽  
pp. 425-438 ◽  
Author(s):  
S. R. Fassnacht
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Surface Profile ◽  
Suspended Sediment Transport ◽  
Mackenzie Delta ◽  
Travel Times ◽  
Channel Networks ◽  
Section Data ◽  
Flow Modelling ◽  
High Sediment

Abstract. The approximate travel times for suspended sediment transport through two multi-channel networks are estimated using flow modelling. The focus is on the movement of high sediment concentrations that travel rapidly downstream. Since suspended sediment transport through river confluences and bifurcation movement is poorly understood, it is assumed that the sediment moves at approximately the average channel velocity during periods of high sediment load movement. Calibration of the flow model is discussed, with an emphasis on the incorporation of cross-section data, that are not referenced to a datum, using a continuous water surface profile. Various flow regimes are examined for the Mackenzie and the Slave River Deltas in the Northwest Territories, Canada, and a significant variation in travel times is illustrated. One set of continuous daily sediment measurements throughout the Mackenzie Delta is used to demonstrate that the travel time estimates are reasonable. Keywords: suspended sediment; multi-channel river systems; flow modelling; sediment transport

Reliability of flood discharge estimates

1991 ◽  
Vol 18 (4) ◽  
pp. 624-630 ◽  
Author(s):  
Michael C. Quick
Keyword(s):  
Sediment Transport ◽  
River Flow ◽  
Theoretical Work ◽  
High Water ◽  
Channel Cross Section ◽  
Approximate Methods ◽  
Channel Slope ◽  
Channel Curvature ◽  
Large Floods ◽  
High Sediment

The high accuracy of normal river discharge measurements is contrasted with the approximate methods used to estimate large floods. The most commonly used method, the slope–area method, is examined and it is argued that there is likely to be a strong upward bias in these flood estimates. Sources of error are subdivided into four main types: (i) error in the Manning friction coefficient, (ii) error in after-flood measurements of channel cross section, (iii) estimation of surface slope and energy grade line from high-water marks, and (iv) the effects of erosion and sediment transport. These various factors are seen to be influenced by channel curvature and meandering, floodplain flow and interaction with the main channel, and changes to channel geometry during a flood. From theoretical work on high sediment transport, it is argued that up to one third of the channel slope is required for moving the sediment, so that only two thirds of the slope is available for transporting the water. Key words: floods, river flow, channel friction, sediment transport, floodplains, meandering.

The High Efficient Sediment-Transport Water Volume in the Lower Yellow River

2011 ◽  
Vol 403-408 ◽  
pp. 228-234
Author(s):  
Jun Yan ◽  
Biao Liang ◽  
Yu Hua Zhang ◽  
Hui Cao
Keyword(s):  
Sediment Transport ◽  
Transport Process ◽  
Yellow River ◽  
Water Volume ◽  
Lower Yellow River ◽  
The Lower Yellow River ◽  
Calculating Method ◽  
High Efficient ◽  
Xiaolangdi Reservoir ◽  
High Sediment

Analyzed the sediment-transport process in high sediment-laden river, the new concept and calculating method for sediment-transport water volume are proposed. Based on field data of sediment and water volume in the Lower Yellow River from 1950 to 2000, the sediment-transport water volume and unit sediment-transport water volume in LYR are calculated. Meanwhile, relations between them and influencing factors are confirmed to calculate efficient sediment-transport water volume after construction of the Xiaolangdi reservoir. Results gained from these functions are consistent well with the facts of real water-sediment regulation in LYR.

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