Evaluation of Morphodynamic Controls on the Preservation of Fluvial Meander‐Belt Deposits

Abstract

Abstract 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.

Keywords

• river morphodynamics
• point bar
• accretion rate
• sediment preservation
• stratigraphic completeness
• numerical model