Recent developments in numerical algorithms have enabled the
construction of three-dimensional models for the prediction of flows in
open channels. These advances encompass improvements in both numerical
solutions and the process representation required for an accurate
system definition. However, to date, there is still little agreement on
how to assess systematically and report the credibility of these
simulations. This paper addresses this problem by adopting a Grid
Convergence Index approach. The results indicate, for two simple
hypothetical cases, a zero-degree confluence and a meander bend, that
the numerical code can be verified to an acceptable numerical standard.
However, it is shown that this does not mean that verification is
complete, as the literature implies, as whilst the discretization
resolution may be sufficient to verify one of the model variables it
does not imply that every variable has converged. Furthermore, the
scheme may still be insufficient to capture all the processes of
interest that are operating within the chosen environment.