Statistical characterization of erosion and sediment transport mechanics
in shallow tidal environments. Part 2: suspended sediment dynamics
Abstract
A proper understanding of sediment transport dynamics, critically
including resuspension and deposition processes of suspended sediments,
is key to the morphodynamics of shallow tidal environments.
Aiming to account for deposition mechanics in a synthetic theoretical
framework introduced to model erosion dynamics (D’Alpaos et al., 2022),
here we investigated suspended sediment dynamics.
A complete spatial and temporal coverage of suspended sediment
concentration (SSC) required to effectively characterize resuspension
events is hardly available through observation alone, even combining
point measurements and satellite images, but it can be retrieved by
properly calibrated and tested numerical models.
We analyzed one-year-long time series of SSC computed by a
bi-dimensional, finite-element model in six historical configurations of
the Venice Lagoon in the last four centuries.
Following the peak over threshold theory, we statistically characterized
suspended sediment dynamics by analyzing interarrival times, intensities
and durations of overthreshold SSC events.
Our results confirm that, as for erosion events, SSC can be modeled as a
marked Poisson process in the intertidal flats for all the considered
historical configurations of the Venice Lagoon because exponentially
distributed random variables well describe interarrival times, intensity
and duration of overthreshold events.
Moreover, interarrival times, intensity and duration describing local
erosion and overthreshold SSC events are highly related, although not
identical because of the non-local dynamics of suspended sediment
transport related to advection and dispersion processes.
Owing to this statistical characterization of SSC events, it is possible
to generate synthetic, yet realistic, time series of SSC for the
long-term modeling of shallow tidal environments.