Astronomic link to anomalously high mean sea level in the northern Adriatic Sea

Earth Surf Processes Landf

Capperucci

Bartholomä

et al. 2022

Self Cite

Tidal channels form the pathways for tidal currents to propagate and distribute clastic sediments and nutrients, thus providing a primary control on tidal-landscape ecomorphodynamics. Most tidal channels in both estuarine and lagoonal environments have a tendency to meander, yet very few studies exist that investigate the full spectrum of processes controlling tidal meander morpho-sedimentary evolution.The Venice Lagoon (Italy) offers a unique opportunity to shed light on this topic, because a long record of morphological and sedimentary data is available, which allows one to relate tidal channel evolution to the hydrodynamic and morphological changes undergone by the lagoon. In particular, during the last 130 years, feedback between rising relative sea levels and anthropogenic interventions has caused severe modifications of the Lagoon hydro-and morphodynamics. Here we investigate how these modifications fed back into the morpho-sedimentary evolution of a meandering tidal channel located in the northern lagoon. Combining extensive datasets of aerial photographs, topographic and bathymetric surveys, geophysical investigations, sedimentary core analysis, and numerical modelling, we show that enhanced local tidal ranges and water discharges determined adjustments of channel cross-sectional geometries proportional to increasing tidal prisms, while changes in local tidal asymmetries caused modifications of the local sediment transport regime, resulting in the development of bar-pool patterns according to the dominant tidal phase. Such bar-pool patterns eventually determined channel migration through a bar-push mechanism controlled by a fluvial-like, quasi-linear relationship between local channel curvature and lateral migration rates. Critical differences in sediment transport regime are, however, highlighted between fluvial and tidal meanders the latter being potentially characterized by high concentrations of suspended sediment during periods of slack waters when wind-driven sediment transport processes are not negligible. This could hamper the formation of high-relief bedforms, with profound implications for the sedimentology of tidal point-bar deposits.

Section: The Venice Lagoonmentioning

confidence: 99%

Morpho‐sedimentary evolution of a microtidal meandering channel driven by 130 years of natural and anthropogenic modifications of the Venice Lagoon (Italy)

Earth Surf Processes Landf

Capperucci

Bartholomä

et al. 2022

Self Cite

“…On the other hand, they caused critical changes in the lagoon hydro‐ and morpho‐dynamic regimes. Since the construction of the jetties, changes in the tidal regime within the lagoon have been much more sustained than the typical periodic, multi‐annual variations induced by the nodal modulation of tides in the Adriatic Sea, which are in the order of 4% of the characteristic tidal range (Amos et al., 2010; Valle‐Levinson et al., 2021). Between 1909 and 1973, the tidal range within the lagoon increased as much as 25% on average (L. D’Alpaos, 2010; Ferrarin et al., 2015; Tomasin, 1974), with local changes that can be even more pronounced (Finotello, Capperucci, et al., 2022; Finotello et al., 2019; Silvestri et al., 2018).…”

Section: Geomorphological Settingmentioning

confidence: 99%

Hydrodynamic Feedbacks of Salt‐Marsh Loss in the Shallow Microtidal Back‐Barrier Lagoon of Venice (Italy)

Water Resources Research

Tognin

Carniello

et al. 2023

Self Cite

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.

“…The Lagoon's present-day morphology is characterized by the presence of three inlets, namely, from North to South: Lido, Malamocco, and Chioggia (Figure 1a-d). Tides follow a semidiurnal microtidal regime, with a mean spring tidal range of 1 m and maximum tidal oscillations of about 0.75 m around Mean Sea Level (MSL) (e.g., D 'Alpaos et al 2013;Valle-Levinson et al 2021).…”

Section: Geomorphological Settingmentioning

confidence: 99%

“…On the other hand, they caused critical changes in the lagoon hydro-and morpho-dynamic regimes. Since the construction of the jetties, changes in the tidal regime within the lagoon have been much more sustained than the typical periodic, multi-annual variations induced by the nodal modulation of tides in the Adriatic Sea, which are in the order of 4% of the characteristic tidal range (Amos et al, 2010;Valle-Levinson et al, 2021). Between 1909 and1973, the tidal range within the lagoon increased as much as 25% on average (L. D 'Alpaos, 2010;Ferrarin et al, 2015;Tomasin, 1974), with local changes that can be even more pronounced (Finotello et al, 2019;Finotello, Capperucci, et al, 2022;Silvestri et al, 2018).…”

Section: Geomorphological Settingmentioning

confidence: 99%

Hydrodynamic feedbacks of salt-marsh loss in the shallow microtidal back-barrier lagoon of Venice (Italy)

Tognin

Carniello

et al. 2023

Preprint

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.