Evaluation of Morphodynamic Controls on the Preservation of Fluvial
Meander-belt Deposits
Abstract
The way river morphodynamics influence the preservation of point-bar
deposits at different spatio-temporal scales is hitherto unquantified.
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: (i) pairs and (ii) sets of accretion packages, and (iii)
meander-belts. Results show 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.