A model-based characterization of confined meandering rivers

In this paper we analyze the dynamics of meandering rivers that flow in geologically confined floodplains. We use a state of art meander morphodynamic model in which the floodplain erodibility can be spatially variable, and can thus be highly reduced where nearly unerodible lateral walls are simulated. We propose a hybrid empirical and model-based indicator to estimate the degree of confinement relative to the potential, unconfined meander belt. Together with commonly used meander morphometric indicators, we propose two novel planform metrics to represent the observed tendency of confined meanders (i) to develop long reaches attached to the geological boundaries, and (ii) to develop more frequent crossing of the floodplain central axis. Results reproduce realistic planforms of confined meanders, quantitatively support previously suggested qualitative classifications of confined meandering rivers, and provide a rational framework to compare meandering rivers having different degree of confinement (strong, moderate, unconfined), as well as different hydro-morphological conditions. Good agreement between model predictions and the few existing field observations support the proposed approach.