Aptitude of modern salt marshes to counteract relative sea-level rise, Venice Lagoon (Italy)

In the past 100 yr, variations in relative sea-level rise (RSLR), the increase of frequency of very high tides, and a decrease of sediment availability caused progressive morphological changes of the Venice Lagoon tidal flats. In contrast with the general erosional trend, some salt marshes in the northern lagoon preserved their main original characteristics and showed accretion and development of the tidal creek network. The evolution of one of them was sketched by the interpretation of ultrahigh-resolution aerial photographs taken from A.D. 1938 to 2006, and results were compared with RSLR rates and storm tide frequency. The long-term investigation pointed out the most significant morphological changes that occurred over the entire period (i.e., erosion of the margin, modifications of the drainage network), whereas the short-term analysis showed in detail the subsequent phases of salt marsh evolution and their relations with sea-level variations. Margin shift was mainly in agreement with RSLR trend, whereas changes of the tidal creek network also reflected frequency of very high tides. Moreover, in the past 70 yr the salt marsh demonstrated a self-renewal aptitude to counteract RSLR: even if it underwent low accretion rates, it did not disappear, probably because the remobilization of sediments eroded from the marsh front and the lagoon bottom by tides and other local hydrodynamic processes, and their accumulation on the marsh surface favored by vegetation were sufficient to offset RSLR.

[1]  John Robert Lawrence Allen,et al.  Morphodynamics of Holocene salt marshes: a review sketch from the Atlantic and Southern North Sea coasts of Europe , 2000 .

[2]  Mark M. Brinson,et al.  RESPONSE OF WETLANDS TO RISING SEA LEVEL IN THE LOWER COASTAL PLAIN OF NORTH CAROLINA , 1995 .

[3]  J. Day,et al.  Soil Accretionary Dynamics, Sea-Level Rise and the Survival of Wetlands in Venice Lagoon: A Field and Modelling Approach , 1999 .

[4]  S. Rahmstorf.  A new view on sea level rise , 2010 .

[5]  S. Rahmstorf,et al.  Global sea level linked to global temperature , 2009, Proceedings of the National Academy of Sciences.

[6]  P. V. Sundareshwar,et al.  RESPONSES OF COASTAL WETLANDS TO RISING SEA LEVEL , 2002 .

[7]  A. Rubino,et al.  Teleconnections force interannual-to-decadal tidal variability in the Lagoon of Venice (northern Adriatic) , 2009 .

[8]  Lukas H. Meyer,et al.  Summary for Policymakers , 2022, The Ocean and Cryosphere in a Changing Climate.

[9]  R. Turner.  Landscape Development and Coastal Wetland Losses in the Northern Gulf of Mexico , 1990 .

[10]  C. Rosenzweig,et al.  Sea level rise projections for current generation CGCMs based on the semi‐empirical method , 2008 .

[11]  Michael S. Kearney,et al.  Landsat imagery shows decline of coastal marshes in Chesapeake and Delaware Bays , 2002 .

[12]  J. Day,et al.  Consequences of sea level rise: Implications from the mississippi delta , 1989 .

[13]  E. Rankey,et al.  Quantified rates of geomorphic change on a modern carbonate tidal flat, Bahamas , 2002 .

[14]  J. Day,et al.  Impacts of sea-level rise on deltas in the Gulf of Mexico and the Mediterranean: The importance of pulsing events to sustainability , 1995 .

[15]  Donald R. Cahoon,et al.  Pattern and process of land loss in the Mississippi Delta: A Spatial and temporal analysis of wetland habitat change , 2000 .

[16]  W. J. Cleary,et al.  Saltmarsh loss in southeastern North Carolina lagoons: importance of sea level rise and inlet dredging , 1987 .

[17]  Nicola Surian,et al.  Channel changes due to river regulation: the case of the Piave River, Italy , 1999 .

[18]  M. Frignani,et al.  210Pb and 137Cs as chronometers for salt marsh accretion in the Venice Lagoon - links to flooding frequency and climate change. , 2007, Journal of environmental radioactivity.

[19]  J. Day,et al.  Relative sea level rise and Venice lagoon wetlands , 1998 .

[20]  M. Frignani,et al.  Lead-210 as a tracer of atmospheric input of heavy metals in the northern Venice Lagoon , 1998 .

[21]  J. Day,et al.  Estimating shallow subsidence in microtidal salt marshes of the southeastern United States: Kaye and Barghoorn revisited , 1995 .

[22]  M. Kirwan,et al.  A coupled geomorphic and ecological model of tidal marsh evolution , 2007, Proceedings of the National Academy of Sciences.

[23]  J. French,et al.  Numerical simulation of vertical marsh growth and adjustment to accelerated sea‐level rise, North Norfolk, U.K. , 1993 .

[24]  P. Ciavola,et al.  Sedimentation Processes on Intertidal Areas of the Lagoon of Venice: Identification of Exceptional Flood Events (Acqua Alta) Using Radionuclides , 2002, Journal of Coastal Research.

[25]  J. Allen.  Simulation models of salt-marsh morphodynamics: some implications for high-intertidal sediment couplets related to sea-level change , 1997 .