Variations in storm-induced bed level dynamics across intertidal flats

Abstract

Hydrodynamic forces on intertidal flats vary over a range of temporal and spatial scales. These spatiotemporal inhomogeneities have implications for intertidal flat morphodynamics and ecology. We determine whether storm events are capable of altering the long-term morphological evolution of intertidal flats, and unravel the contributions of tidal flow, wind-driven flow, waves, and water depth on inhomogeneities in bed level dynamics (bed level changes over ~days) across these areas. We complement decades of bed level measurements on eight intertidal flats in two estuaries in the Netherlands with an extensive 1-month field campaign on one of those flats. Across this intertidal flat, the hydrodynamics and morphodynamics of a storm event were captured, including the poststorm recovery. We show that individual events can persistently alter the morphological evolution of intertidal flats; magnitudes of some bed level changes are even comparable to years of continuous evolution. The morphological impacts of events are largely controlled by the relative timing of the forcing processes, and not solely by their magnitudes. Spatiotemporal variations in bed level dynamics of intertidal flats are driven by a combination of: (1) the inhomogeneous distributions of the hydrodynamic forcing processes (including the under-explored role of the wind); and (2) the linear proportionality between bed level dynamics and the local bed slope.

Contrasting strategies to cope with storm‐induced erosion events: a flume study comparing a native vs. introduced bivalve

“…Mimicking storm-induced rapid erosion events: the concept and flume design Manipulating sediment erosion rates is important to better understand bivalve vulnerability to storm-induced erosion, because storms do not all have the same intensity. As storms of higher intensity can induce larger volumes of sediment erosion than storms of a lower intensity (Hu et al 2017;de Vet et al 2020), the proportion of surfaced bivalves in a population is likely to increase with the intensity of a storm. We may also observe threshold effects, where once a certain sediment erosion rate is reached, all the individuals of a population are surfaced.…”

“…However, extreme storms can erode 10-15 cm of sediment on intertidal flats in a single event (see de Vet et al 2020;Hu et al 2015Hu et al , 2017Zhu et al 2019), thereby not only threatening shallow-buried juvenile bivalves, but also adults. Severe storm-induced erosion can decrease macrofaunal abundances (de Vet et al 2020), cause long-term community structural change (Ong and Krishnan 1995), and large bivalve mortality events (Rees et al 1977;Yeo and Risk 1979;Cadée 2016;Shi et al 2021). Indeed, exposure of bivalves to the sediment surface can increase the risk of mortality by predation , desiccation (Kurihara 2003), and transport to unfavorable habitat (Cadée 2016).…”

“…Under daily hydrodynamic forcing, slow-moving adult bivalves are safe from erosion due to their size and burrowing depth (Yeo and Risk 1979;Hunt 2004). However, extreme storms can erode 10-15 cm of sediment on intertidal flats in a single event (see de Vet et al 2020;Hu et al 2015Hu et al , 2017Zhu et al 2019), thereby not only threatening shallow-buried juvenile bivalves, but also adults. Severe storm-induced erosion can decrease macrofaunal abundances (de Vet et al 2020), cause long-term community structural change (Ong and Krishnan 1995), and large bivalve mortality events (Rees et al 1977;Yeo and Risk 1979;Cadée 2016;Shi et al 2021).…”

Key Bioturbator Species Within Benthic Communities Determine Sediment Resuspension Thresholds

“…We specifically chose to measure τ cr , as it is applicable in quantitative modeling approaches used to upscale the biogeomorphological interactions investigated here. τ cr of the sediment was measured rather than that of the fluff layer, as the thickness of the latter is generally in the order of mm, while erosion on tidal flats during storms can be in the order of centimeters (de Vet et al, 2020). This is distinctly different from annular flume measurements (cf.…”

Vulnerability assessment of nearshore clam habitat subject to storm waves and surge

“…Therefore, the disaster risk and infrastructural vulnerability to storms attract substantial research efforts. Besides the physical damage to human communities, hurricane waves and surge may bring great changes to the littoral morphology accompanied by widespread impacts to coastal infaunal assemblages 3 – 5 . In contrast, studies on better understanding these ecological implications are insufficient and lag behind 6 – 9 , although critical for the proactively managed disaster resilience.…”