Evaluation of Morphodynamic Controls on the Preservation of Fluvial Meander-belt Deposits

The way river morphodynamics influence the preservation of point-bar deposits at multiple scales is not fully understood. Employing time-lapse trajectories of natural rivers, a numerical model is used here to simulate planform evolutions of meander-belt reaches that embody different transformation behaviors and cutoff processes. Proxies for temporal durations are obtained considering the surface area over which a river migrated and channel migration rates that relate to average channel radius of curvature through constant, monotonic, and non-monotonic relationships. The preservation of meander-belt deposits over different timescales is assessed at three architectural hierarchies: (a) pairs and (b) sets of accretion packages, and (c) meander-belts. Results confirm that sediment preservation decreases in a predictable way with the accumulation time; however, accretion rates decay with time in a way that does not follow the expected power-law. This is interpreted to reflect the effect of the onset of geomorphic thresholds of channel transformation and cutoff.