Rethinking the resilience of salt marshes to land subsidence and sea-level rise: The RESTORE project approach

Coastal transitional environments (CTE) are among the most productive ecosystems in the world, supporting various natural functions and providing important ecosystem services to human societies. Because of their low elevation, CTE are expected to be severely threatened by the accelerated sea-level rise (SLR) and their resilience will depend on the capability to keep pace with SLR. Recent field studies and modelling analyses suggests that Holocene events in terms of sedimentation rates and distribution of lithology could significantly influence the evolution and resilience of CTE with expected climate changes. Using the Venice Lagoon (Italy) as a case study, the RESTORE (i.e. REconstruct subsurface heterogeneities and quantify sediment needs TO improve the REsilience of Venice saltmarshes) project proposes a new multidisciplinary approach that combines geological conceptualizations, numerical modelling and vulnerability assessment to quantify the amount of sediment that CTE need to keep pace with the relative SLR. Specific attention is paid to the type of deposits and shallow subsurface architecture that play a key role in the process of land subsidence and autocompaction, i.e., the natural compaction caused by sediment self-weight. Specifically, the RESTORE workflow includes developing a detailed 3D reconstruction of the Holocene stratigraphic architecture and associated geomechanical properties, developing a numerical model that can simulate the evolution of elevations and natural subsidence over the Holocene, and developing a vulnerability assessment able to highlight the areas of the lagoon most threatened by SLR. Expected results include the evaluation of quantitative data on the sediments needed to keep pace with IPCC projected sea-level rise and the production of  vulnerability maps of tidal morphologies to different sea-level rise scenarios to assist policymakers in developing restoration, conservation, and mitigation plans.