Meandering and braiding of rivers

1978 ◽  
Vol 84 (4) ◽  
pp. 609-624 ◽  
Author(s):  
Jørgen Fredsøe
Keyword(s):  
Laboratory Experiments ◽  
Bed Load ◽  
Two Dimensional ◽  
Transport Mechanisms ◽  
Dimensional Model ◽  
Alluvial Rivers ◽  
Load Transport ◽  
Bed Load Transport ◽  
The Stability ◽  
Natural Rivers

The origin of meandering and braiding of alluvial rivers is re-analysed in terms of stability theory. The flow is described by a two-dimensional model, and the transportation of sediment is separated into bed-load transport and transport of suspended sediment, by use of the improved knowledge of sediment transport mechanisms achieved in recent years. The paper explains why it is important to distinguish between the sediment transported as bed load and that in suspension.The analysis is able to predict whether a river remains stable or tends to meander or braid.The results of the stability analysis are compared with laboratory experiments and data from natural rivers, and the agreement is satisfactory.

On the development of dunes in erodible channels

1974 ◽  
Vol 64 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Jørgen Fredsøe
Keyword(s):  
Stability Analysis ◽  
Order Approximation ◽  
Experimental Fact ◽  
Bed Load ◽  
Two Dimensional ◽  
Alluvial Channel ◽  
Load Transport ◽  
Bed Load Transport ◽  
The Stability ◽  
Vorticity Transport

A two-dimensional stability analysis of the flow in a straight alluvial channel has been carried out, using the vorticity transport equation. In the analysis an attempt has been made to account for the influence of gravity on bed-load transport, and this turned out to change the stability quite significantly.In the case of instability, the further growth of the dunes has been investigated using a second-order approximation, This nonlinear theory explains the experimental fact that the dunes very soon become asymmetric.

scholarly journals Bed-load transport: From the beginning into the future

2018 ◽  
Vol 40 ◽  
pp. 05003
Author(s):  
Willi H. Hager
Keyword(s):  
Current Knowledge ◽  
Laboratory Data ◽  
Bed Load ◽  
Transport Parameters ◽  
Water And Sediment ◽  
Experimental Campaign ◽  
Load Transport ◽  
Bed Load Transport ◽  
Natural Rivers

This research addresses bed-load transport in the fluvial environment. Based on the current knowledge, it is first noted that this problem is by far not solved. The eminent questions ask for a large experimental campaign by which the basic issues are solved first, and then expanded to more challenging topics relating to questions not included in the first stage involving uniform water and sediment flows. A number of currently available experimental techniques is mentioned by which a high-quality laboratory experimentation should be feasible. Next, the effects of various fundamental transport parameters should be cleared using both systematic experimentation and data analyses. An improved bed-load transport equation should be established first, by which the current tools are replaced to produce better agreement with prototype data. The role of computational hydraulics is also highlighted, to apply results to natural rivers. Froude similitude should be carefully applied so that the laboratory data can safely be transferred to prototype conditions, if the limitations are respected.

scholarly journals The Application of Radioactive Tracers for Determination of Bed-Load Transport in Alluvial Rivers

1980 ◽  
Vol 11 (3-4) ◽  
pp. 133-144 ◽  
Author(s):  
Thorkild Thomsen
Keyword(s):  
Radioactive Isotopes ◽  
Bed Load ◽  
Alluvial Rivers ◽  
Tracer Particles ◽  
Bed Forms ◽  
Load Transport ◽  
Bed Load Transport ◽  
Tracer Methods ◽  
The Difference

Radioactive isotopes have been applied for determining the transport rate of bed load in an alluvial river on the basis of: centroid velocity of the tracer particles, size and material-transporting width of mobile layer. These parameters were found by detailed measurements in the field. Computed values were produced on the basis of Engelund and Fredsøe's model on sediment transport (1976) and on the propagation of bed forms. When comparing measured and computed values, the difference was about 25%. Finally, the applicability of tracer methods for solving practical problems is discussed.

scholarly journals Two-Dimensional Numerical Simulation Study on Bed-load Transport in Fluctuating Backwater Area: A Case-Study Reservoir in China

2018 ◽  
Author(s):  
Ming Luo ◽  
Heli Yu ◽  
Er Huang ◽  
Rui Ding ◽  
Xin Lu
Keyword(s):  
Sediment Transport ◽  
Transport Model ◽  
Longitudinal Section ◽  
Bed Load ◽  
Two Dimensional ◽  
River Bed ◽  
Reservoir Drawdown ◽  
Load Transport ◽  
Bed Load Transport ◽  
Volume Method

Numerical modeling of sedimentation and erosion in reservoirs is an active field of reservoir research. However, simulation of bed-load transport phenomena has rarely been applied to other water bodies, in particular, the fluctuating backwater area. This is because the complex morphological processes between hydrodynamics and sediment transport are generally challenging to accurately predict. In this study, the refinement and application of a two-dimensional shallow-water and bed-load transport model to the fluctuating backwater area is described. The model employs the finite volume method of the Godunov scheme and saturated sediment transport equations. The model was verified against experimental data of a scaled physical model. It was then applied to actual reservoir operation, including reservoir storage, reservoir drawdown and continuous flood process, to predict the morphology of reservoir sedimentation and sediment transport rates and bed level changes in the fluctuating backwater area. It was found that the location and morphology of sedimentation effected by the downstream water level results in random evolution of the river bed, and bed-load sedimentation is transported from upstream to downstream with the slope of the longitudinal section of the river bed generally reduced. Moreover, the sediment is mainly deposited in the main channel and the elevation difference between the riverbank and channel decreases gradually.

scholarly journals Whit ham method of the expansion near the wave front propagating on the river with bed load transport

1990 ◽  
Vol 12 (3) ◽  
pp. 8-14
Author(s):  
Pham Hung
Keyword(s):  
Differential Equation ◽  
Wave Front ◽  
Water Surface ◽  
Bed Load ◽  
Flood Wave ◽  
Load Transport ◽  
Bed Load Transport ◽  
Linear Differential ◽  
The Stability ◽  
Special Case

In this paper the non linear differential equation describing the behavior of water surface behind the wave front is obtained by Whit ham method. It is shown that the bed load transport could influence significantly on the stability of the flood wave. In the supercritical flow, the bed load wave will propagate upstream and will linearly stabilize. The different situations when the wave could topple over are analyzed. In the flow without the bed load transport, the results of Whit ham have been reobtained as a special case.  

scholarly journals Structural Properties of the Static Armor during Formation and Reestablishment in Gravel-Bed Rivers

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1845
Author(s):  
Qiang Wang ◽  
Yunwen Pan ◽  
Kejun Yang ◽  
Ruihua Nie
Keyword(s):  
Random Field ◽  
Structural Properties ◽  
Transport Rate ◽  
Surface Elevation ◽  
Bed Load ◽  
Two Dimensional ◽  
Statistical Parameters ◽  
Laboratory Flume ◽  
Load Transport ◽  
Bed Load Transport

The formation and reestablishment of bed structural properties in the static armor layer is an important research subject. To address this issue, we conducted a series of static armor layer experiments in a laboratory flume that focused on formation and reestablishment. Through an automatic measurement system, we obtained a real-time bed load transport rate. The bed surface elevation at different flow intensities was obtained using a PTS (Photo Terrain Scanning) system. The results show that the formation and reestablishment of the bed load transport rate in the static armor layer increased from zero to its peak before decaying. The bed structure response was found to be highly dependent on the unevenness of the bed surface elevation. The bed surface elevation of a static armor layer in a laboratory flume is considered as a two-dimensional random field. In a two-dimensional random field, the changes in bed elevation are characterized using statistical parameters. Statistical parameters are evaluated from precise digital elevation models (DEMs) of bed surfaces. Experimental results provide the change of probability distribution functions (PDFs) and second-order structure functions of bed elevations between formation and reestablishment after breaking the static armor layer. By quantitatively analyzing the changes in these statistical parameters, we quantified the difference between the bed structure in the static armor layer formation and the new static armor layer formed after being broken. Thus, this finding reveals that the bed structure of the static armor layer formed by different flow intensities is different, and this difference can be quantified using statistical methods.

Sign in / Sign up

Export Citation Format

Share Document