Sediment transport in the lower Saginaw River

1995 ◽  
Vol 46 (1) ◽  
pp. 337 ◽  
Author(s):  
M Cardenas ◽  
J Gailani ◽  
CK Zeigler ◽  
W Lick
Keyword(s):  
Sediment Transport ◽  
Transport Model ◽  
Three Dimensional ◽  
Computer Time ◽  
Numerical Calculations ◽  
Time Dependent ◽  
Curvilinear Coordinates ◽  
Bed Load ◽  
Sediment Bed ◽  
Dependent Model

A study of the resuspension, deposition and transport of sediments and the resulting changes in bathymetry in the lower part of the Saginaw River in Michigan has been made. The numerical model used in this study consists of a two-dimensional, vertically integrated, time-dependent hydrodynamic and transport model coupled with a three-dimensional, time-dependent model of the dynamics of the sediment bed and its properties. Transport of sediment as suspended load and bed load was included in the analysis. In the numerical calculations, curvilinear coordinates were used. For verification of the model, results of numerical calculations of changes in the thickness of the sediment bed due to time-varying flow events were compared with bathyrnetric measurements taken at nine transects on the river on 28 August 1991 and 13 May 1992. From the transect measurements, from measurements of flow rates and sediment concentrations, and from the numerical modelling, a reasonably accurate description of the sediment transport and the resulting bathymetric changes has been made. The calculations and observations show that resuspension/deposition, bed load, and slumping are significant factors in changing the bathymetry. It is also shown that the largest flows are responsible for most of the sediment erosion and deposition and must therefore be understood and considered in detail. An approximate procedure for making long-term (1 to 25 year) calculations is presented and discussed. This procedure greatly reduces the required computer time but still maintains the required accuracy for the prediction of sediment and contaminant transport and fate.

scholarly journals A Methodology for Estimating the Parameters in Three-Dimensional Cohesive Sediment Transport Models by Assimilating In Situ Observations with the Adjoint Method

2017 ◽  
Vol 34 (7) ◽  
pp. 1469-1482 ◽  
Author(s):  
Daosheng Wang ◽  
Jicai Zhang ◽  
Ya Ping Wang ◽  
Xianqing Lv ◽  
Yang Yang ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Adjoint Method ◽  
Settling Velocity ◽  
Transport Model ◽  
Three Dimensional ◽  
Temporal Variations ◽  
Cohesive Sediment ◽  
Cohesive Sediment Transport ◽  
Resuspension Rate

AbstractThe model parameters in the suspended cohesive sediment transport model are quite important for the accurate simulation of suspended sediment concentrations (SSCs). Based on a three-dimensional cohesive sediment transport model and its adjoint model, the in situ observed SSCs at four stations are assimilated to simulate the SSCs and to estimate the parameters in Hangzhou Bay in China. Numerical experimental results show that the adjoint method can efficiently improve the simulation results, which can benefit the prediction of SSCs. The time series of the modeled SSCs present a clear semidiurnal variation, in which the maximal SSCs occur during the flood tide and near the high water level due to the large current speeds. Sensitivity experiments prove that the estimated results of the settling velocity and resuspension rate, especially the temporal variations, are robust to the model settings. The temporal variations of the estimated settling velocity are negatively correlated with the tidal elevation. The main reason is that the mean size of the suspended sediments can be reduced during the flood tide, which consequently decreases the settling velocity according to Stokes’s law, and it is opposite in the ebb tide. The temporal variations of the estimated resuspension rate and the current speeds have a significantly positive correlation, which accords with the dynamics of the resuspension rate. The temporal variations of the settling velocity and resuspension rate are reasonable from the viewpoint of physics, indicating the adjoint method can be an effective tool for estimating the parameters in the sediment transport models.

scholarly journals 3 Dimensional Modeling of Advection-Diffusion Equation

2019 ◽  
Author(s):  
Amin Ilia
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Transport Model ◽  
Three Dimensional ◽  
Water Levels ◽  
Dynamics Simulation ◽  
Advection Diffusion ◽  
Sediment Transport Model ◽  
Time Splitting ◽  
2D Model

Estimation of flows and sediment transport is challenging as many complexes and interacting physical phenomena need to be accounted for. In this research, a coupled two-dimensional finite volume flow model and a three-dimensional sediment transport model were developed in Fortran. In this model, the depth-integrated current vectors and water level were computed by 2D shallow water equations as the 2D model is computationally much faster than the 3D model. The depth-integrated current vectors were distributed in depths using a logarithmic current distribution equation, log of the wall. These distributed velocities and simulated water levels were used for three-dimensional sediment transport model which is generated using the same scheme. A 3D sediment transport model was preferred over a 2D model as 3D sediment model can estimate vertically diffusion of sediment mass from bedload to suspended sediment load which significantly improves the prediction of morphology evolutions.In order to discretize each subset of equations with the best-suited method, I utilized a time-splitting technique. As a result, I applied the second-order Fromm scheme which was found the best method for solving advection terms and semi-implicit forward time central space method which was found the best method for solving diffusion terms. The time-splitting scheme also reduced the complicity, therefore, the solution became simple and attractive to apply. For developing the sediment transport model, I applied this advection-diffusion concept to estimate the distribution of suspended sediment concentration and the Van Rijn (1981) scheme for the estimation of bedload sediment transport. As it’s very important to estimate and predict this phenomenon accurately, I compared the model with a lab trench experiment and the model results were in agreement with lab experiments. It was shown that the model could accurately simulate sedimentation on the downsloping (deceleration) section and erosion on the upsloping (acceleration) section of a marine trench. This would cause lateral movement of the channel toward the current direction. Being capable of accurate sediment transport and morphological dynamics simulation in this complex setting, this model is validated to be applied to other marine problems.

scholarly journals THE IMPACT OF BARRIER ISLAND DEGRADATION ON HURRICANE-INDUCED SEDIMENT TRANSPORT

2018 ◽  
pp. 49
Author(s):  
Ke Liu ◽  
Qin Chen ◽  
Kelin Hu
Keyword(s):  
Sediment Transport ◽  
Storm Surge ◽  
Coastal Wetland ◽  
Transport Model ◽  
Three Dimensional ◽  
Barrier Islands ◽  
Coastal Morphology ◽  
Major Barrier ◽  
Barataria Bay ◽  
The Impact

Hurricanes are recognized as a strong forcing in changing coastal morphology by redistributing sediments. Barrier islands protect estuaries from storm surge and severe waves and confine water and sediment discharge into estuaries during a hurricane event. In this study, we developed a three-dimensional, fully coupled storm surge, waves, and sediment transport model. The impacts of barrier islands degradation on hurricane hydrodynamics and sediment dynamics were evaluated by comparing a hypothetical model configuration for four major barrier islands in Terrebonne Bay and Barataria Bay against a baseline configuration. With the hypothetical deterioration of barrier islands, model results showed that the sediment transport from the shelf to the estuary increased in Terrebonne Bay but decreased in Barataria Bay. In the simulations, most of the deposition on coastal wetland still originated from the bay even when the barrier islands were degraded.

scholarly journals A Three-Dimensional Flow and Sediment Transport Model for Free-Surface Open Channel Flows on Unstructured Flexible Meshes

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 18 ◽  
Author(s):  
Yong Lai ◽  
Kuowei Wu
Keyword(s):  
Free Surface ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Open Channel ◽  
Transport Model ◽  
Three Dimensional ◽  
Suspended Sediment Transport ◽  
Open Channel Flows ◽  
Sediment Transport Model ◽  
Flow And Sediment Transport

Three-dimensional (3D) hydrostatic-pressure-assumption numerical models are widely used for environmental flows with free surfaces and phase interfaces. In this study, a new flow and sediment transport model is developed, aiming to be general and more flexible than existing models. A general set of governing equations are used for the flow and suspended sediment transport, an improved solution algorithm is proposed, and a new mesh type is developed based on the unstructured polygonal mesh in the horizontal plane and a terrain-following sigma mesh in the vertical direction. The new flow model is verified first with the experimental cases, to ensure the validity of flow and free surface predictions. The model is then validated with cases having the suspended sediment transport. In particular, turbidity current flows are simulated to examine how the model predicts the interface between the fluid and sediments. The predicted results agree well with the available experimental data for all test cases. The model is generally applicable to all open-channel flows, such as rivers and reservoirs, with both flow and suspended sediment transport issues.

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