Modeling the planform evolution of confined meandering rivers

The presence of lateral planimetric constraints preventing free migration and avulsion has a significant influence on the planform dynamics of river meanders. This particular confined kind of meandering rivers is definitely understudied, especially in comparison to freely migrating ones. Through a semi-analytical meander model, here we attempt to investigate the effect of the confined floodplain width through a morphodynamic modeling approach. The confined floodplain width is defined as the width between symmetric lateral confinement where the river is free to migrate, on the planform pattern and dynamics. Model results illustrate that weak confinement (i.e. loose floodplain boundaries) increases planform irregularity, with the river centerline preferentially lying close to floodplain boundaries, while strong confinement (tight floodplain boundaries) leads to a remarkable planform regularity, constituted by periodic sequences of sawtooth-shaped meanders. Bend orientation is reminiscent of the sub/super-resonant regime regardless of the confinement width. Model results are supported by good agreement with available field and remote sensing observation on selected case studies of confined meandering rivers in Canada previously studied by Nicoll and Hickin (2014).