Review of wave-driven sediment resuspension and transport in estuaries

Abstract

Waves are fundamentally important to the physical and biological functioning of estuaries.Understanding and predicting contaminant transport, development of sedimentary structures, geomorphological response to changes in external forcings such as rising sea level, and response of estuarine ecosystems to contaminant stressors require understanding of the relative roles of wave-and current-driven sediment transport. We review wave-driven sediment resuspension and transport in estuaries, including generation of bed shear stress by waves, initiation of sediment motion by waves, and the ways waves modulate, add to, and interact with sediment transport driven by currents. A key characteristic of the waveinduced force on the seabed is extreme spatial and temporal variations; simple analytical models are revealing of the way such patterns develop. Statistical methods have been widely applied to predict wave resuspension of intertidal-flat bed sediments, and physically based predictors of resuspension developed from open-coast studies appear to also apply to short-period estuarine waves. There is ample experimental evidence to conclude that over the long term, waves erode and tidal currents accrete intertidal flats. Waves indirectly add to the formation of fluid mud by adding to the estuarine pool of fine sediment, and waves may fluidize subtidal seabeds, changing bed erodibility. Models have been used to explore the dynamic balance between sediment transport by waves and by currents and have revealed the key control of waves on estuarine morphology. Estuarine intertidal flats are excellent natural laboratories that offer opportunities for working on a number of fundamental problems in sediment transport.

Macrofaunal Functional Diversity Provides Resilience to Nutrient Enrichment in Coastal Sediments

“…DistLM showed that 39-54% of response to enrichment could be explained, most of it by macrofaunal diversity. It is difficult to speculate on the source(s) of the unexplained variation in DEA CN , but on a dynamic intertidal sandflat spatial and temporal variations in sediment biogeochemistry caused by hydrodynamic forcing (Green and Coco 2014;Huettel and others 2014), foraging and excretion by large predators (for example, Thrush and others 1994;Hines and others 1997;Jauffrais and others 2015), detrital inputs (for example, Eyre and Ferguson 2002;Eyre and others 2013) and microbial diversity (for example, Yazdani Foshtomi and others 2015) could all contribute, as could any initial small-scale variation between plots within a site. Nevertheless, the fact that a substantial proportion of the DEA response could be explained by macrofauna diversity despite the complexity of the field setting emphasises its importance in regulating the effects of enrichment.…”

Analysis of Suspended Particulate Matter and Its Drivers in Sahelian Ponds and Lakes by Remote Sensing (Landsat and MODIS): Gourma Region, Mali

“…Considering that resuspension does not occur in dry years and that it stops in April-May, it is legitimate to include water depth as a possible limiting factor of SPM resuspension. Indeed, the resuspension of lake bottom sediment occurs when the water is not too deep (otherwise, the wave-driven turbulence would not reach the lake bottom), which is never the case for ponds in this region, nor too shallow (otherwise, large waves cannot develop) [46].…”

Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

“…Tidal asymmetries and lag effects are classically regarded as drivers of sediment import from the channels to the tidal flats, but it is unclear whether that still holds if the influence of wave forcing is considered. As an example, Green and Coco (2014) reported about studies in which waves are argued to enhance settling lag by lengthening the settling trajectories, or conversely to impair settling lag by agitating the water column and preventing settling. By means of defining a unifying framework (next Section 2.4), we will be able to assess how wave resuspension affects magnitude and direction of the tidal barotropic mechanisms.…”

“…Wind and wave forcing influence the sediment transport patterns in the basin Lettmann et al 2009;Sassi et al 2015). In this paper, we direct our attention to the erosion of sediment by small-amplitiude waves, which has been recognized as a process of major importance for morphodynamics of tidal flats (Green and Coco 2007;Green 2011;Green and Coco (2014;Talke and Stacey 2008;Friedrichs 2012). The wave-orbital velocities influence the distribution of the bed-shear stresses and hence the sediment fluxes caused by the tidal flow.…”