Coastal flooding prevention measures, such as storm-surge barriers, are being widely adopted globally because of the accelerating rise in sea levels. However, their impacts on the morphodynamics of shallow tidal embayments remain poorly understood. Here, we combine field data and modeling results from the microtidal Venice Lagoon (Italy) to identify short- and long-term consequences of flood regulation on lagoonal landforms. Artificial reduction of water levels enhances wave-induced sediment resuspension from tidal flats, promoting in-channel deposition, at the expense of salt marsh vertical accretion. In Venice, we estimate that the first 15 closures of the recently installed mobile floodgates operated between October 2020 and January 2021 contributed to a 12% reduction in marsh deposition, simultaneously promoting a generalized channel infilling. Therefore, suitable countermeasures need to be taken to offset these processes and prevent significant losses of geomorphic diversity due to repeated floodgate closures, whose frequency will increase as sea levels rise further.
We describe three athletes who had syncope after (case 1) or during (cases 2, 3) hyperventilation. During the episode, ECG showed prolonged sinus arrest. Clinical data and noninvasive investigations were normal and the phenomenon was not reproducible. Electrophysiological study after autonomic blockade allowed a prolonged intrinsic heart rate in case 1, and abnormal corrected sinus node recovery time in cases 1 and 2. During follow-up, symptomatic sinus arrest provoked by deep inspiration occurred in case 3. These cases document prolonged asystole of unknown etiology, secondary to hyperventilation, and probably caused by different vagally-mediated mechanisms.
<p>Coastal systems are among the most economically valuable and highly threatened systems on Earth. They provide a wide range of valuable ecosystem services but are severely threatened by climate changes and increasing human pressure. We consider and analyze the Venice Lagoon as a paradigmatic case representative of the coevolution of man and landscape, of natural processes and human agency. The history and fate of Venice Lagoon, the largest brackish waterbody in the Mediterranean, are tightly intertwined with those of the City of Venice. We show, through an interdisciplinary approach combining field observations, remote sensing, laboratory analyses, and mathematical modeling, that increasing anthropogenic pressure, coupled with the effects of natural processes exacerbated by climate changes, has led to an accelerated morphological deterioration of the lagoon and of the related ecosystem services. We also provide new insights on the short- and long-term consequences of coastal flooding prevention measures, such as storm-surge barriers, which are being widely adopted globally because of the accelerating rise in sea levels. From this point of view, the Venice and Venice Lagoon issues are becoming the new paradigm of the conflicts arising from the interactions among economy, society, and the environment, the three main pillars of sustainable development, furthermore providing an indication of what fate has in store for coastal cities and ecosystems of the future.</p>
Extensive loss of salt marshes in back‐barrier tidal embayments is ongoing worldwide as a consequence of land‐use changes, wave‐driven lateral marsh erosion, and relative sea‐level rise compounded by mineral sediment starvation. However, how salt‐marsh loss affects the hydrodynamics of back‐barrier systems and feeds back into their morphodynamic evolution is still poorly understood. Here we use a depth‐averaged numerical hydrodynamic model to investigate the feedback between salt‐marsh erosion and hydrodynamic changes in the Venice Lagoon, a large microtidal back‐barrier system in northeastern Italy. Numerical simulations are carried out for past morphological configurations of the lagoon dating back up to 1887, as well as for hypothetical scenarios involving additional marsh erosion relative to the present‐day conditions. The progressive loss of salt marshes significantly impacted the lagoon hydrodynamics, both directly and indirectly, by amplifying high‐tide water levels, reducing wind‐wave energy dissipation, and critically affecting tidal asymmetries across the lagoon. Restoration projects and manmade protection of marsh margins, which have been implemented over the past few decades, limited the detrimental effects of marsh loss on the lagoon hydrodynamics, while not substantially changing the risk of flooding in urban lagoon settlements. Compared to previous studies, our analyses suggest that the hydrodynamic response of back‐barrier systems to salt‐marsh erosion is extremely site‐specific, depending closely on the morphological characteristics of the embayment as well as on the external tidal and wind forcings.
Extensive loss of salt marshes in back-barrier tidal embayments is undergoing worldwide as a consequence of land-use changes, wave-driven lateral marsh erosion, and relative sea-level rise compounded by mineral sediment starvation. However, how salt-marsh loss affects the hydrodynamics of back-barrier systems and feeds back into their morphodynamic evolution is still poorly understood. Here we use a depth-averaged numerical hydrodynamic model to investigate the feedback between salt-marsh erosion and hydrodynamic changes in the Venice Lagoon, a large microtidal back-barrier system in northeastern Italy. Numerical simulations are carried out for past morphological configurations of the lagoon dating back up to 1887, as well as for hypothetical scenarios involving additional marsh erosion relative to the present-day conditions. We demonstrate that the progressive loss of salt marshes significantly impacted the Lagoon hydrodynamics, both directly and indirectly, by amplifying high-tide water levels, promoting the formation of higher and more powerful wind waves, and critically affecting tidal asymmetries across the lagoon. We also argue that further losses of salt marshes, partially prevented by restoration projects and manmade protection of salt-marsh margins against wave erosion, which have been put in place over the past few decades, limited the detrimental effects of marsh loss on the lagoon hydrodynamics, while not substantially changing the risk of flooding in urban lagoon settlements. Compared to previous studies, our analyses suggest that the hydrodynamic response of back-barrier systems to salt-marsh erosion is extremely site-specific, depending closely on the morphological characteristics of the embayment as well as on the external climatic forcings.
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