Ecohydraulics of Surrogate Salt Marshes for Coastal Protection: Wave–Vegetation Interaction and Related Hydrodynamics on Vegetated Foreshores at Sea Dikes

Abstract

Vegetation on foreshores in close vicinity to sea dikes may prove beneficial as regulating ecosystem service in the context of coastal defense, dike safety, and flood protection by reducing loads on these defense structures. Predominantly, a decrease in wave heights and bottom shear stresses is hypothesized, which calls for an inclusion in design procedures of coastal defense structures. In contrast to heterogeneous and variable salt marsh vegetation, this study uses surrogate vegetation models for systematic hydraulic experiments in a wave flume, without modeling specific plant species a priori. Froude-scale experiments are performed in order to investigate the effect of salt marsh vegetation on the wave transformation processes on the foreshore and wave run-up at sea dikes. The effect of plant and wave properties on wave transmission, energy dissipation, and wave run-up at a 1:6 sloped smooth dike are presented and discussed, focusing on the wave-vegetation-structure interaction. Vegetated foreshores can contribute to wave attenuation, where an increasing relative vegetation height h v /h results in decreased wave run-up on the dike by up to 16.5% at h v /h = 1.0.

The influence of infragravity waves on the safety of coastal defences: a case study of the Dutch Wadden Sea

“…12 and 18), a minimum foreshore slope of 1/1000 (or 0.1 %) is considered here. This is in line with the common approach where slopes milder than or equal to 0.1 % are treated equally as (nearly) flat (Keimer et al, 2021;Steendam et al, 2004). Note that the calculated foreshore slopes ranged from −0.04 % to 4 % with an average of 0.14 %, where a negative slope indicates a slight downward slope towards the dike toe.…”

Proposing a novel classification of growth periods based on biomechanical properties and seasonal changes of Spartina anglica

“…Furthermore, the results can be implemented into modeling approaches, including the coastal protection potential of above-ground biomass of salt marsh vegetation. Physical surrogates (see, for example, Augustin et al, 2009;van Veelen et al, 2020;Keimer et al, 2021;Keimer et al, 2022) can be adjusted to incorporate the aspect of seasonality for different storm scenarios. Furthermore, numerical simulations can be extended to include the variance in vegetation properties (see, for example, van Loon-Steensma et al, 2016).…”

“…Ecosystem-based coastal defenses (Schoonees et al, 2019) provide multiple ecosystem services (European Commission and Directorate-General for Environment, 2014;Haines-Young and Potschin, 2018), enhancing their environmental value while bolstering natural resilience (Bouma et al, 2014;Doswald et al, 2014). Salt marshes, taking reference to various globally distributed sites (Mcowen et al, 2017), have been studied in laboratories and in the field to evaluate multiple ecosystem services, like the absorption of hydrodynamic energy (Ghisalberti and Nepf, 2006;Augustin et al, 2009;Ysebaert et al, 2011;Koftis et al, 2013;Anderson and Smith, 2014;Möller et al, 2014;Carus et al, 2016;Vuik et al, 2016;Rupprecht et al, 2017;Lou et al, 2018;Garzon et al, 2019;van Veelen et al, 2020;Willemsen et al, 2020;Keimer et al, 2021;Zhang et al, 2022), sediment accretion (Christiansen et al, 2000;Cahoon et al, 2006;Andersen et al, 2011;Baaij et al, 2021;Cahoon et al, 2021;Proenca et al, 2021), soil stabilization (Ford et al, 2016;Kosmalla et al, 2022;Schoutens et al, 2022) and geomorphological changes Chen et al, 2020;Cao et al, 2021;Ladd et al, 2021).The above-mentioned effects depend on vegetation species, traits of the above-and below-ground biomass and hydrodynamic conditions (Schoutens et al, 2020). Integrating and upscaling the presence of salt marshes into coastal protection plans, thus, adds multiple protection funct...…”

Design and Insights Gained in a Real-World Laboratory for the Implementation of New Coastal Protection Strategies

“…simply compensate for the anticipated loss of biodiversity [7]. A promising approach to promote coastal resilience are nature-based solutions (NbS) that offer or even exploit services provided by ecosystems [8,9], e.g., wave attenuation [10,11], accretion of sediments or reduction of erosion naturally provisioned or supported by coral reefs, salt marshes, seagrass meadows or coastal dunes [12][13][14][15][16]. Further studies and experiences of NbS are provided and discussed, e.g., by Scheres et al [17] on alternative plant coverage and its root systems stabilizing sea dikes or by Staudt et al [18] on the ecological dimensions of beach and foreshore nourishments with marine aggregates, such as sand and gravel.…”