Changes in the wind‐wave field and related salt‐marsh lateral erosion: inferences from the evolution of the Venice Lagoon in the last four centuries

Abstract

Salt marshes are crucially important ecosystems at the boundary between the land and the sea, that are experiencing significant losses worldwide mainly dictated by the erosion of their margins. Improving our understanding of the mechanisms controlling marsh edge erosion is a key step to address conservation issues and salt‐marsh response to changes in the environmental forcing. Here we have employed a complete, coupled Wind‐Wave Tidal Model (WWTM) to analyse the temporal evolution of the wave field, and in particular of the mean wave‐power density, in the Venice Lagoon over the past four centuries (from 1611 to 2012). We have then related wave‐field changes to the observed erosion patterns determined by comparing recent aerial photographs (1978–2010) and historical bathymetric data. The results of our analyses from the Venice Lagoon show that, while wave‐fields did not significantly change from 1611 to 1901, a rapid increase in wave‐power densities occurred in the last century. This is suggested to depend on the positive feedback between relevant morphological evolutions and changes in the wave field, both influenced by natural forcing and anthropogenic pressures. We also emphasize the existence of a strong positive linear relationship between the volumetric marsh erosion rate and mean wave‐power density. We thus suggest that relating salt‐marsh lateral erosion rates to properly computed mean wave‐power densities provides a valuable tool to address long‐term tidal morphodynamics. © 2019 John Wiley & Sons, Ltd.

Remote Sensing for Optimal Estimation of Water Temperature Dynamics in Shallow Tidal Environments

“…The main environmental issues are the progressive reduction of the main morphological structures of the lagoonal environment, i.e., salt marshes and tidal flats, and the lagoon water quality. In the last 100 years, a reduction of about 40% of the salt marshes area and a 30% increase of the mean water depth has been observed, reinforcing the erosional trends by increasing the mean fetch and depth of the flows [23][24][25]. The modified hydrodynamics and the increased erosion and resuspension of sediments significantly affect also the water quality, spreading the pollutants accumulated in the Lagoon's sediments.…”

River, Coastal and Estuarine Morphodynamics Selected papers from the 10th anniversary of the RCEM Symposium

“…By combining observational evidence from the Venice Lagoon in the last four centuries and the results of numerical simulations, Tommasini et al . () address the mechanisms controlling marsh edge erosion in shallow tidal systems. By analysing the effects of the impinging wind waves on the retreat of salt‐marsh boundaries, and how the temporal evolution of wind‐wave fields over the last centuries affects erosional dynamics, they highlight that relating salt‐marsh lateral erosion rates to mean wave‐power densities provides a valuable tool to address long‐term tidal morphodynamics.…”

“…The 17 collected contributions include four state-of-science papers concerning the most recent advances in computational morphodynamic modelling of coupled flow-bed-sediment systems (Shimizu et al, 2019), a critical analysis of existing data on vegetation-flow-sediment interactions obtained through both laboratory experiments and field campaigns (Tinoco et al, 2020), a review of existing moving-boundary theories of shorelines with two extensions to allow inclusion of firstorder effects of waves and tides (Voller et al, 2020), and an overall assessment of the role played by wave forcing on the hydro-morphodynamics in shallow nearshore areas and at river mouths (Brocchini, 2019). The other 13 papers cover different topics about morphodynamics, spanning multiple environments, tackling concepts and processes with the aid of refined theoretical and numerical tools (Redolfi et al, 2019;Tambroni et al, 2019), grounding the results on laboratory data (Finotello et al, 2019;Geng et al, 2019;Matoušek et al, 2019, Porcile et al, 2020 and field observations (Fogarin et al, 2019;Tommasini et al, 2019), and making use of interdisciplinary approaches (Calvani et al, 2019;Chen et al, 2019;Pivato et al, 2019;van de Vijsel et al, 2020) also to develop new conceptualizations (Schlömer et al, 2020).…”

“…This high-resolution map can then be used to classify different benthic habitats, reflecting the spatial variability in hydrodynamics and sediment transport pathways, on the basis of a multidisciplinary approach that involves geomorphology, fluid dynamics and ecology. By combining observational evidence from the Venice Lagoon in the last four centuries and the results of numerical simulations, Tommasini et al (2019) address the mechanisms controlling marsh edge erosion in shallow tidal systems. By analysing the effects of the impinging wind waves on the retreat of salt-marsh boundaries, and how the temporal evolution of wind-wave fields over the last centuries affects erosional dynamics, they highlight that relating salt-marsh lateral erosion rates to mean wave-power densities provides a valuable tool to address long-term tidal morphodynamics.…”

Tidal regime shift in Lingdingyang Bay, the Pearl River Delta: An identification and assessment of driving factors

“…Temporal–spatial tidal forcing affects not only the transport of sediments, nutrients, and contaminants (Falcão, Santos, Drago, Serpa, & Monteiro, 2009; Bonaldo et al, 2014) in estuaries but also salt intrusion and storm surge propagation (Zhang, Savenije, Wu, Kong, & Zhu, 2011; Zhang, Savenije, Chen, & Mao, 2012; Li, Zhu, Wu, & Guo, 2014). In recent decades, intensive human activities (e.g., dredging for navigation, sand excavation, and land reclamation) have dramatically changed the morphology of many estuaries and, have caused the erosion of estuarine saltmarshes (Bendoni et al, 2016; Francalanci, Bendoni, Rinaldi, & Solari, 2013; Tommasini, Carniello, Ghinassi, Roner, & D'Alpaos, 2019) and altered the tidal regimes and hydrodynamics (Zhang et al, 2017; Mei et al, 2018; Wu et al, 2018; Zhang et al, 2018; Finotello Canestrelli, Carniello, Ghinassi, & D'Alpaos, 2019). For these reasons, the response of tidal forcing to human activities has attracted worldwide research attention.…”