Simulating long-term river morphodynamics at watershed scale.

It has been a traditional practice of fluvial engineers to apply the uniform water-flow hypothesis to real rivers by averaging the geometric and hydraulic quantities over appropriate portions of the river reach. No quantitative criterion, however, was applied to assess the validity and limitations of this procedure. The present paper collects a number of theoretical considerations and relevant observations (developed in the framework of two recent doctoral theses) that are quite useful for selecting the approximated model most suitable for studying morphodynamic problems at watershed scale. Particularly efficient for this analysis has been consideration of the river in quasi-equilibrium conditions. [ABSTRACT FROM AUTHOR]