Winds of opportunity

Winds of opportunity: The effects of wind on intertidal flat accretion

Colosimo, I. (TU Delft Environmental Fluid Mechanics)
van Maren, D.S. (TU Delft Environmental Fluid Mechanics; Shanghai Estuarine and Coastal Science Research Center; Deltares)
de Vet, P.L.M. (TU Delft Coastal Engineering; Deltares)
Winterwerp, J.C. (TU Delft Environmental Fluid Mechanics)
van Prooijen, Bram (TU Delft Coastal Engineering)

2023

Intertidal ecosystems are threatened by sea level rise and anthropogenic pressures. Understanding the processes controlling the morphodynamic developments of tidal flats is crucial for sustainable management of these systems. Analysis of three extensive fieldwork campaigns carried out on two adjacent mudflats fringing the Dutch Western Wadden Sea (from 2016 to 2018) provides important new insights into the conditions controlling a permanent increase of tidal flat elevation (‘accretion’), in which the wind and consolidation processes play a pivotal role. Sediment temporarily settles (‘deposition’) on the flats during a period of high suspended sediment availability and water level setup (often following a storm). A tidal flat accretes when a new layer of sediment over-consolidates: a state in which the bed strength is much larger than it would attain during inundated conditions, due to high stresses experienced during prolonged drying. This happens when a phase of sediment deposition is followed by a sufficiently long period with a low ambient water table (phreatic level) and aerial exposure. The chronological order of sediment deposition and over-consolidation provides a window of opportunity for tidal flat accretion. Such a window of opportunity depends on the hydrodynamic forcing (tides, waves, wind), on the consolidation state of the bed, and on sediment availability. Wind plays a crucial role in creating the conditions for tidal flat accretion because the wind direction influences the duration of a low water table and aerial exposure and therefore (over-)consolidation rates, which we refer to as the ‘winds of opportunity’. An abundance of sediment may even limit tidal flat accretion, because large deposition rates substantially increase consolidation timescales.

Accretion
Coastal morphology
Deposition
Intertidal flats
Over-consolidation
Suspended sediment concentration
Wind-driven transport

http://resolver.tudelft.nl/uuid:feeafd2b-a4b4-4920-a3d7-c00b9c2a064a

https://doi.org/10.1016/j.geomorph.2023.108840

0169-555X

Geomorphology, 439

Institutional Repository

journal article

© 2023 I. Colosimo, D.S. van Maren, P.L.M. de Vet, J.C. Winterwerp, Bram van Prooijen