Seaward expansion of salt marshes maintains morphological self-similarity of tidal channel networks

Yang, Zhicheng; Finotello, Alvise; Goodwin, Guillaume; Gao, Chao; Mudd, Simon M.; Lague, Dimitri; Schwarz, Christian; Tian, Bo; Ghinassi, Massimiliano; D’Alpaos, Andrea

doi:10.1016/j.jhydrol.2022.128733

“…Second, our simulated scenarios do not account for salt‐marsh landward migration, which can mitigate the net loss of salt marshes (e.g., Enwright et al., 2016; Fagherazzi et al., 2019; Feagin et al., 2010; Field et al., 2016; Kirwan & Gedan, 2019). Even though this process is typically hindered by the presence of levees and dikes at the interface between marshes and the upland (e.g., Yang et al., 2022), it cannot be disregarded a priori. The colonization of new intertidal areas by marsh upland migration would profoundly change the hydrodynamics and sediment budget of the whole back‐barrier system, as new areas would be periodically flooded by tides and additional sediment volumes would become available as marshes expand landward.…”

Section: Discussionmentioning

confidence: 99%

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

Finotello

¹

,

Tognin

²

,

Carniello

³

et al. 2023

Water Resources Research

Self Cite

View full text Add to dashboard 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.

show abstract

“…Second, our simulated scenarios do not account for salt-marsh landward migration, which can mitigate the net loss of salt marshes (e.g., Feagin et al 2010;Field et al 2016;Enwright et al 2016;Fagherazzi et al 2019;Kirwan and Gedan 2019). Even though this process is typically hindered by the presence of levees and dikes at the interface between marshes and the upland (e.g., Yang et al, 2022), it cannot be disregarded a priori. The colonization of new intertidal areas by marsh upland migration would profoundly change the hydrodynamics and sediment budget of the whole back-barrier system, as new areas would be periodically flooded by tides and additional sediment volumes would become available as marshes expand landward.…”

Section: Implications For the Hydrodynamics Of Back-barrier Tidal Lag...mentioning

confidence: 99%

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

Finotello

¹

,

Tognin

²

,

Carniello

³

et al. 2023

Preprint

0

View full text Add to dashboard Cite

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.

show abstract

“…Second, our simulated scenarios do not account for the fact that salt marshes can potentially migrate landward, in this way increasing the total salt-marsh area or at least reducing the rate at which salt marshes are lost (e.g., Feagin et al 2010;Field et al 2016;Enwright et al 2016;Fagherazzi et al 2019;Kirwan and Gedan 2019). While this process is hindered in the Venice Lagoon, as well as in most salt marsh ecosystems worldwide, by the presence of fixed seawalls, levees, and dikes at the interface between marshes and the upland (e.g., Yang et al, 2022), it cannot be disregarded a priori. Clearly, the colonization of new intertidal areas by marsh upland migration would profoundly change the hydrodynamics and sediment budget of the whole backbarrier system, since new areas would be periodically flooded by tides and additional sediment volumes would become available as marshes expand landward.…”

Section: Implications For the Hydrodynamics Of Back-barrier Tidal Lag...mentioning

confidence: 99%

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

Finotello

¹

,

Tognin

²

,

Carniello

³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Seaward expansion of salt marshes maintains morphological self-similarity of tidal channel networks

Cited by 5 publications

References 93 publications

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

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

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

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

Contact Info

Product

Resources

About