A coupled biomorpho-geomechanical model of tidal marsh evolution
C. Zoccarato, P. Teatini
Dept. of Civile, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
C. Da Lio
Institute of Marine Sciences, CNR, Venice, Italy
L. Tosi
Institute of Geosciences and Earth Resources, CNR, Padova, Italy
ABSTRACT
Ecogeomorphic characteristics of tidal marshes are strongly related
to their elevation with respect to the mean sea level. Predicting the
long-term evolution and resilience of such ecosystems in times of rapid
natural and anthropogenic climate changes is of critical importance.
The notion that the tidal marsh elevation is the result of feedbacks between
vegetation dynamics, sediment fluxes, natural consolidation, and sea level changes
is widely recognized. However, the interaction of these processes has been
poorly investigated until now. This contribution aims at presenting a novel
numerical model to simulate the above-surface and subsurface coupled dynamics
of a tidal landscape in a 2D-framework, with the relative sea level rise (RSLR)
acting as an external stressor. A biomorphological model is used to compute
deposition fluxes, which depends on topography and availability of organic/inorganic
sediments. The outcome is used as forcing term in a physically-based geomechanical
model to simulate the consolidation of the marsh body that, in turn, influences sediment
fluxes by acting on the platform elevation. The results demonstrate how compaction
of the marsh body can crucially affect the resilience of tidal landforms to RSLR
accelerations. With normal sediment concentration in coastal waters (10<Co<100
mg/l), if minerogenic (stiff) deposits prevail, a tidal marsh is capable of
maintaining its elevation relative to msl independently of RSLR (at least up to
10 mm/yr). When the marsh is composed of a large percentage of more compressible
organic matter, the landform resilience is much more dependent on RSLR, implying
higher vulnerability with respect to future climate changes.
