Three-dimensional simulation of river flood flows

The velocity field in meandering river channels during overbank flows is fully three-dimensional. To date, there have been few attempts to simulate this behaviour using three-dimensional computer models; most investigations have been experimental or used two-dimensional computer models that assume a hydrostatic pressure distribution. Fully three-dimensional simulations are important, as they will improve our understanding of the velocity field and the role of turbulence in determining this, particularly along the shear layer where the flood plain and main channel flows interact. This in turn will have practical implications for our knowledge of the mechanics of channel morphology, pollutant transport and conveyance capacity. In the present paper, the application of a CFD computer code to simulate flood flows on the River Severn (UK) is presented, and a comparison is made with field data collected for the purpose of computer model verification. The quantitative comparisons are encouraging and illustrate the potential of CFD codes for use in river engineering problems.