Relative sea level rise and Venice Lagoon wetlands  <B>Relative sea level rise and Venice Lagoon wetlands</B><P>J.W. Day Jr.1, D. Are2, A. Rismondo2, F. Scarton2 and G. Cecconi3</B><I><P> 1 Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana, USA <BR> 2 Biotecnica, Viale Garibaldi, VeneziaMestre, Italy <BR> 3 Consorzio Venezia Nuova, Venice, Italy</I><P> Abstract<P> Over the past century, Venice Lagoon has experienced a high rate of wetland loss and a strong net export of sediments; nowadays the local Authority (Magistrato alle Acque di Venezia MAV) is running several projects for beneficial use of dredging materials. From March 1993 until March 1995, the accretionary response of wetlands in the lagoon to changing water levels was studied. Vertical accretion, short term sedimentation, and surface elevation change were measured at six sites with varying sediment availability and wave energy. Short term sedimentation averaged 6.85 g/m2/d with a minimum of 0.06 g and a maximum of 72 g during periods of high tides and storms. Over two years accretion ranged from 0.3 to 2.3 cm yr1 and surface elevation change ranged from +0.7 to 3.7 cm yr1. The sites with highest accretion were near a river mouth and a site with strong wave energy and rapid erosion of the marsh edge with a high resuspended sediment availability. A marsh created with dredged spoil had a high rate of elevation loss due mainly to compaction. The rate of accretion at three sites was clearly sufficient to offset relative sea level rise, but a saline site with low sediment availability had the lowest accretion. A sediment fence significantly increased accretion at one site. The results suggest that reduction of turbulent motion or increasing sediment availability are needed to offset wetland loss indifferent areas of the lagoon.<P>