SMRM

The SMRM is a reduced complexity, two-dimensional rule-based model of marsh response to SLR that only requires the input of four parameters: (1) a high-resolution DTM, representing both the target marsh area and adjacent surfaces (e.g., tidal flats, backbarrier flats, dunes, alluvial plains), with an acceptable spatial range, resolution and quality to allow simulating marsh expansion; (2) critical tidal levels, representing transition between main intertidal environments and vegetation sensitive to submersion time; in the test-cases addressed herein, the model considers mean high-water neap elevation (MHWN) as the critical boundary between tidal flat and low marsh, mean high-water (MHW) as the transition between low and high marsh, and mean high-water spring (MHWS) as the upper growth limit of the high marsh; (3) at least one SLR projection, including an initial rate and an optional SLR acceleration value; (4) representative accretion/sedimentation rates for high marsh, low marsh and tidal flat domains, which can remain invariant over time or change throughout the century (in this last case, acceleration values of accretion rates must be introduced). The SMRM works with several data sources, putting together the results obtained from fieldwork and laboratory (accretion rates), monitoring equipment (tidal levels and SLR), physical models (SLR) and remote sensing (DTM).

The model has been built considering the premises that present-day tidal amplitudes will not change significantly in future decades and that the signal and rate of evolution of the salt marsh surface results from the balance between SLR rates and accretion rates.

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