High curvatures drive river meandering

Abstract

One of the long- and widely held ideas about the dynamics of meandering rivers is that migration slows down in bends with higher curvatures. High-resolution measurements of migration rates of more than 1600 bends in time-lapse Landsat satellite images, covering more than 4000 km of seven rapidly migrating meandering rivers in the Amazon Basin, suggest that the variation of migration rate closely follows that of the local channel curvature. However, locations of maximum migration rate are shifted downstream relative to peak curvature, with a phase lag that shows limited variability for the same river segment. A quasi-linear relationship exists between the two if this lag is taken into account. Overall, bends with the highest curvatures show the highest migration rates; exceptions with limited migration seem to be related to the low erodibility of the outer bank, not the hydrodynamics of the flow. The implication is that one of the most important ways river migration is rejuvenated and meandering patterns are reshuffled is the generation of high-curvature bends through cutoffs.