Explore the vast range of titles available.

Sinuous channels wandering through coastal wetlands have been thought to lack lateral‐migration features like meander cutoffs and oxbows, spurring the broad interpretation that tidal and fluvial meanders differ morphodynamically. Motivated by recent work showing similarities in planform dynamics between tidal and fluvial meandering channels, we analyzed meander neck cutoffs from diverse tidal and fluvial environments worldwide, and show that tidal cutoffs are widespread. Their perceived paucity stems from pronounced channel density and hydrological connectivity in coastal wetlands, comparatively small size of most tidal channels, and typically dense vegetation cover. Although these factors do not efface tidal meander cutoffs, they collectively inhibit oxbow formation and make tidal cutoffs ephemeral features that can escape detection. We argue that similar morphodynamic processes drive cutoff formation in tidal and fluvial landscapes, with differences arising only during post‐cutoff evolution. Such process similarity has important implications for understanding coastal wetland ecomorphodynamics and predicting their long‐term evolution. Plain Language Summary The sinuous channels that wander through tidal coastal wetlands look like meandering rivers. However, features of alluvial floodplains that indicate active river meandering over time, such as oxbow lakes and meander cutoffs, are difficult to find in tidal settings. Their apparent absence has led researchers to infer that tidal and fluvial meanders evolve differently. We re‐examined this inference by identifying, measuring, and compiling examples of meander cutoffs from a variety of tidal coastal wetlands and fluvial floodplains worldwide. Our analysis suggests that the shapes and geometric properties of tidal and fluvial cutoffs are indeed remarkably similar. This indicates that while tidal and fluvial environments differ in many ways, they nevertheless share the same physical mechanism affecting meander morphodynamical evolution. Differences between tidal and fluvial meanders do arise after a meander is cut off. We observe that tidal meanders remain preferentially connected to the parent channel, preventing the formation of crescent‐shaped oxbow lakes and thus making tidal cutoffs more difficult to detect. Our results indicate a close similarity in meandering channel behavior across tidal and fluvial systems, which opens new opportunities for how researchers model tidal wetlands, with important implications for the effective conservation and restoration of these critical ecosystems. Key Points Tidal meander cutoffs are far more common than typically thought and share remarkable morphometric similarities with fluvial counterparts Similar mechanisms trigger cutoffs in both tidal and fluvial landscapes, with differences arising only during post‐cutoff evolution Tidal cutoffs seldom disconnect from parent channels and rarely form oxbows due to the high hydrological connectivity of tidal wetlands

Channel meandering is ubiquitous in tidal marshes, yet it is either omitted or weakly implemented in morphodynamic models. Here we propose a novel numerical method to simulate channel meandering in tidal marshes on a Cartesian grid. The method calculates a first‐order flow by considering the balance between pressure gradient and bed friction. To account for flow momentum shift toward meander outer banks, the flow is empirically modified. Unlike previous simplified methods that relied on the curvature of the bank, this modification is based on the curvature of the flow, making the model suitable for use in dendritic channel networks. The modified flow intrinsically accounts for the topographic steering effect, which tends to deflect the momentum toward the outer bank. As a result, the outer bank becomes steeper and erodes due to soil creep. Additionally, the outer bank experiences erosion proportional to the flow curvature. This mechanism parameterizes the direct erosion caused by flow impacting the bank through a proportionality coefficient, which modulates the rate of channel lateral migration. Deposition on the inner bank is automatically simulated by the model, triggered by reduced bed shear stress in that area. The model accurately reproduces channel lateral migration and sinuosity development, and associated processes such as meander cutoffs, channel piracies, and network reorganizations. The model provides an efficient tool for predicting marsh landscape evolution from decades to millennia, and will enable exploring how lateral migration and meandering of tidal channels affect marsh ecomorphodynamics, carbon and nutrient cycling, drainage efficiency, and pond dynamics. Key Points Novel, depth‐averaged, Cartesian‐grid‐based numerical model to simulate channel meandering in tidal marshes Realistic tidal channel morphologies and dynamics are reproduced, including cuspate bends, meander cutoffs, and channel piracies Model simulates the ecomorphodynamic evolution of tidal marshes with branching and meandering channel networks over decades to millennia

Conditions for vegetation spreading and pattern formation are mathematically framed through an analysis encompassing three fundamental processes: flow stochasticity, vegetation dynamics, and sediment transport. Flow unsteadiness is included through Poisson stochastic processes whereby vegetation dynamics appears as a secondary instability, which is addre6ssed by Floquet theory. Results show that the model captures the physical conditions heralding the transition between bare and vegetated fluvial states where the nonlinear formation and growth of finite alternate bars are accounted for by Center Manifold Projection. This paves the way to understand changes in biogeomorphological styles induced by man in the Anthropocene and of natural origin since the Paleozoic (Devonian plant hypothesis).

Coastal dunes, in particular foredunes, support a resilient ecosystem and reduce coastal vulnerability to storms. In contrast to dry desert dunes, coastal dunes arise from interactions between biological and physical processes. Ecologists have traditionally addressed coastal ecosystems by assuming that they adapt to preexisting dune topography, whereas geomorphologists have studied the properties of foredunes primarily in connection to physical, not biological, factors. Here, we study foredune development using an ecomorphodynamic model that resolves the coevolution of topography and vegetation in response to both physical and ecological factors. We find that foredune growth is eventually limited by a negative feedback between wind flow and topography. As a consequence, steady-state foredunes are scale invariant, which allows us to derive scaling relations for maximum foredune height and formation time. These relations suggest that plant zonation (in particular for strand “dune-building” species) is the primary factor controlling the maximum size of foredunes and therefore the amount of sand stored in a coastal dune system. We also find that aeolian sand supply to the dunes determines the timescale of foredune formation. These results offer a potential explanation for the empirical relation between beach type and foredune size, in which large (small) foredunes are found on dissipative (reflective) beaches. Higher waves associated with dissipative beaches increase the disturbance of strand species, which shifts foredune formation landward and thus leads to larger foredunes. In this scenario, plants play a much more active role in modifying their habitat and altering coastal vulnerability than previously thought.

We present a new bidimensional, spatially-explicit ecological model describing the dynamics of halophytic vegetation in tidal saline wetlands. Existing vegetation models employ relatively simple deterministic or stochastic mechanisms, and are driven by local environmental conditions. In the proposed model, in contrast, vegetation dynamics depend not only on the marsh local habitat, but also on spatially-explicit mechanisms of dispersal and competition among multiple interacting species. The role of habitat quality, here determined by the local elevation relative to the mean sea level as a proxy for environmental conditions, is mathematically modeled by a logistic function that represents the fundamental (theoretical) niche of each halophytic species. Hence, the model does not artificially impose any constraints to the ability of a species to colonize elevated areas where it is usually not observed: such limitations naturally arise through competition with fitter species across marsh topographic gradients. We qualitatively test our model against field data based on a suitable assemblage of focus species, and perform a sensitivity analysis aimed at determining how dynamic equilibria in vegetation distributions are affected by changes in model input parameters. Results indicate that the model is robust and can predict realistic vegetation distributions and species-richness patterns. More importantly, the model is also able to effectively reproduce the outcomes of classical ecological experiments, wherein a species is transplanted to an area outside its realized niche. A direct comparison shows that previous models not accounting for dispersal and interspecific competitions are unable to reproduce such dynamics. Our model can be easily integrated into virtually any existing morphodynamic model, thereby strengthening our ability to simulate the coupled biotic and abiotic evolution of salt marshes under changing climate forcings.