Salt Marsh Hydrodynamics

Earth Surf Processes Landf

Wang

2022

Self Cite

Section: Discussionmentioning

confidence: 99%

“…meander wavelength) rather than basin scale. Tidal flows locally dominated by peakebb velocities could arise even in overall flood-dominated environments, due to the strong control that the geomorphic structure of intertidal areas exerts on tidal hydrodynamics(D'Alpaos et al, 2021;…”

mentioning

confidence: 99%

Predominant landward skewing of tidal meanders

Gao

Earth Surf Processes Landf

Wang

2022

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“…Indeed, the evolution of tidal meanders is typically recorded in the stratigraphic record through laterally accreted deposits, as well as through channel infilling as the tidal prism (i.e. the volume of water flowing through a given cross‐section during half of a tidal cycle; D'Alpaos et al, 2010, 2021) decreases when the channel is partially abandoned via either avulsion or meander cut‐off (Brivio et al, 2016; Cosma et al, 2019, 2020; D'Alpaos et al, 2017; Fenies & Faugères, 1998; Ghinassi, D'Alpaos, et al, 2018; Wilson et al, 2017).…”

Section: Introductionmentioning

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

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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.

“…This is a critical knowledge gap because significant differences might exist in terms of flow fields between tidal channels wandering through vegetated and unvegetated intertidal plains, especially concerning overbank stages (i.e., water levels that exceed the channel‐bankfull capacity). Overbank velocities in vegetated settings dominated by turbulence and friction are typically a magnitude lower than those observed on unvegetated mudflats (Bouma et al., 2005; Christiansen et al., 2000; D’Alpaos et al., 2021; Friedrichs, 2011; Hughes, 2012; Rinaldo et al., 1999a; Sullivan et al., 2015). Besides, overbank stages are more frequent in mudflats than in salt marshes, owing to the relatively lower position occupied by mudflat‐channel banks within the intertidal frame.…”

Section: Introductionmentioning

confidence: 96%

Hydrodynamics of Meander Bends in Intertidal Mudflats: A Field Study From the Macrotidal Yangkou Coast, China

Gao

Water Resources Research

D’Alpaos

et al. 2022

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Meandering channels are ubiquitous features in intertidal mudflats and play a key role in the eco‐morphosedimentary evolution of such landscapes. However, the hydrodynamics and morphodynamic evolution of these channels are poorly known, and direct flow measurements are virtually nonexistent to date. Here, we present new hydroacoustic data collected synchronously at different sites along a mudflat meander located in the macrotidal Yangkou tidal flat (Jiangsu, China) over an 8‐day period. The studied bend exhibits an overall dominance of flood flows, with velocity surges of about 0.8 m/s occurring immediately below the bankfull stage during both ebb and flood tides. Unlike salt‐marsh channels, velocities attain nearly constant, sustained values as long as tidal flows remain confined within the channel and reduce significantly during overbank stages. In contrast, curvature‐induced cross‐sectional flows are more pronounced during overbank stages. Thus, a phase lag exists between streamwise and cross‐stream velocity maxima, which limits the transfer of secondary flows and likely hinders the formation of curvature‐induced helical flows along the entire meander length. Our results support earlier suggestions that the morphodynamics of intertidal mudflat meanders does not strongly depend on curvature‐induced helical flows and is most likely driven by high velocities and sustains seepage flows at late‐ebb stages, as well as by other tidally‐mediated processes such as waves and intense rainfall events. By unraveling complex flow structures and intertwined morphodynamic processes, our results provide the first step toward a better understanding of intertidal mudflat meanders, with relevant implications for their planform characteristics and dynamic evolution.