Understanding and predicting wave erosion of marsh edges

Abstract

[1] Margin lateral erosion is arguably the main mechanism leading to marsh loss in estuaries and lagoons worldwide. Our understanding of the mechanisms controlling marsh edge erosion is currently quite limited and current predictive models rely on empirical laws with limited general applicability. We propose here a simple theoretical treatment of the problem based on dimensional analysis. The identification of the variables controlling the problem and the application of Buckingham's theorem show, purely on dimensional grounds, that the rate of edge erosion and the incident wave power density are linearly related. The predictive ability of the derived relationship is then evaluated, positively, using new long-term observations from the Venice lagoon (Italy) and by re-interpreting data available in previous literature.

The secret gardener: vegetation and the emergence of biogeomorphic patterns in tidal environments

“…Equation (2.1) inherently refers to a 'vertical' accounting of deposition and erosion contributions, and hence does not include edge erosion processes. We note, however, that neglecting such processes does not affect the validity of the results presented here, as 'vertical' dynamics and horizontal erosion of tidal landforms are largely independent [33,34]. Because temporal variations in the bottom profile occur over time scales typical of morphological changes, i.e.…”

Critical width of tidal flats triggers marsh collapse in the absence of sea-level rise

“…We therefore develop a simple dynamic model that includes the following processes: (i) wave power and related marsh boundary erosion increases with tidal flat fetch and depth; (ii) marsh boundary erosion increases the fetch of the adjacent tidal flats, thus increasing wave power (1,14); (iii) marsh boundary erosion releases sediments that become available to settle on the tidal flats, reducing water depths and thus decreasing wave power (1,14,15); (iv) fetch and depth control sediment resuspension by waves on the tidal flat. This resuspension mechanism, combined with tidal fluxes, determines the sediment exchange with the open sea and whether the tidal flat erodes or aggrades in time (16).…”

Coastal wetland loss, consequences, and challenges for restoration

“…On the other hand, marshes can be drowned where available suspended sediment concentrations are very low (1-10 mgL −1 ) and tidal range is very small (<1 m) (Kirwan et al 2016). Wind waves also play an important role in the erosion and loss of salt marshes worldwide, especially at boundary zones (Marani et al 2011;Leonardi and Fagherazzi 2015). Lowwave-energy conditions can even result in large portions of marsh loss (Leonardi and Fagherazzi 2015).…”

“…Yet the knowledge for the mechanism of bio-morphological interaction is rather limited, and is often site-specific in terms of tidal ranges, wave energy, salinity gradients, suspended sediment contents, morphological conditions, and species structure. General interpretations of marsh mechanisms obtained at large scale also need site-dependent data input to support successful rehabilitation (Marani et al 2011).…”