Modelling width adjustment in straight alluvial channels

Many existing numerical alluvial channel models are limited because they are unable to account for adjustments of channel width through time. In this paper, the basis for modelling width adjustment in straight river channels is discussed. Features and capabilities of selected models are discussed in terms of advances made in representing the physical processes and mechanisms involved in width adjustment, and in terms of approaches used to characterize initial and boundary conditions accurately. Validation and verification studies of existing width adjustment models are also considered. Existing models have, for the most part, not yet been subjected to rigorous evaluation of their numerical robustness, accuracy in replicating analytical solutions, accuracy in replicating laboratory data or their ability to simulate field situations. In part, these limitations reflect the lack of available detailed laboratory and field data sets required to evaluate complex models. The potential of width adjustment models for use as tools for the investigation of river channel dynamics is briefly described using two examples.