Braid-bars.

Braid-bars.

Dynamics and deposits of braid-bars in the World’s largest rivers: Processes, morphology and subsurface sedimentology

This NERC funded project runs from 2008 to 2011. It is led by Phil Ashworth (University of Brighton) and involves a team from Brighton, Birmingham, Durham, Exeter, Leeds, Illinois, Santa Fe and Corrientes. Full details on the project team and research can be found on the project website.

The work aims to develop an improved understanding of the interactions between flow, sediment transport, alluvial bedforms, channel morphology and sedimentology within the World’s largest multi-channel rivers, using a combination of field measurement and numerical modelling. These techniques are being applied within selected reaches of the Rio Paraná in NE Argentina (the 5th largest river in the World in terms of its mean discharge).

Work led from Exeter by Andrew Nicholas is applying both 2D physics-based and reduced-complexity (RC) models to investigate flow, sediment transport, channel morphodynamics and sedimentology. The hydrodynamic component of the RC model is being evaluated using field data and results from Computational Fluid Dynamics modelling of 3D flow conducted by the team at Durham (led by Stuart Lane and Richard Hardy).

The RC model is being applied to investigate processes within sections of the Rio Parana (see above) and to simulate braid bar evolution in idealised channel geometries, such as simple flow expansions where bar formation is common (see below).

Simulations are also being conducted using the commercial code Delft3D (in depth-averaged mode), to investigate flow, morphodynamics and sedimentology (see below). These simulations are being evaluated using bathymetric surveys that quantify channel change over the past 100 years along the Paraná.

An example of simulated bar migration within the upstream portion of the reach shown above can be seen in this movie.

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