Zoltan Sylvester, Paul Durkin, Steve Hubbard, David Mohrig

Although it has long been recognized that deposition along meandering rivers is not restricted to convex banks, the consensus is that external forcing, that is, confinement by an erosion-resistant barrier, is necessary for significant concave-bank deposition to occur. Using a kinematic model of channel meandering and time-lapse satellite imagery from the Mamoré River in Bolivia, we show that downstream translation and the associated concave-bank deposition are essential, autogenic parts of the meandering process, and they are expected to be present whenever perturbations such as bend cutoffs and channel reoccupations create shorter bends with high curvatures. The implication is that zones of concave-bank deposition with lower elevations, relatively fine-grained deposits, stagnant water bodies, and riparian vegetation different from what is characteristic of point bars are more common than previously considered.