The Impact of Wind on Flow and Sediment Transport over Intertidal Flats

Irene Colosimo,Ad J. H. M. Reniers,Johan C. Winterwerp,Dirk S. van Maren,Bram C. van Prooijen,Paul L. M. de Vet

doi:10.3390/jmse8110910

Irene Colosimo, Ad J. H. M. Reniers + Show 4 more

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https://doi.org/10.3390/jmse8110910

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Abstract

Sediment transport over intertidal flats is driven by a combination of waves, tides, and wind-driven flow. In this study we aimed at identifying and quantifying the interactions between these processes. A five week long dataset consisting of flow velocities, waves, water depths, suspended sediment concentrations, and bed level changes was collected at two locations across a tidal flat in the Wadden Sea (The Netherlands). A momentum balance was evaluated, based on field data, for windy and non-windy conditions. The results show that wind speed and direction have large impacts on the net flow, and that even moderate wind can reverse the tidal flow. A simple analytical tide–wind interaction model shows that the wind-induced reversal can be predicted as a function of tidal flow amplitude and wind forcing. Asymmetries in sediment transport are not only related to the tide–wind interaction, but also to the intratidal asymmetries in sediment concentration. These asymmetries are influenced by wind-induced circulation interacting with the large scale topography. An analysis of the shear stresses induced by waves and currents revealed the relative contributions of local processes (resuspension) and large-scale processes (advection) at different tidal flat elevations.

Highlights

Intertidal flats are habitats of vital importance for numerous flora and fauna species
Full-Period Time Series The time series of wind speed and direction, water depth, long-shore and cross-shore flow velocity, significant wave height, and suspended sediment concentration (SSC) are shown in Figure 3 for the lower mudflat (FLM) and in Figure 4 for the higher mudflat (FHM)
The flow velocity resulting from the non-linear interaction between tide and wind-driven flow was estimated by applying the momentum balance equation and using field data to quantify its terms

Summary

Introduction

Intertidal flats are habitats of vital importance for numerous flora and fauna species. Migrating birds especially depend on these areas for their survival [1,2]. Depending on its future rate, sea level rise may cause the drowning of intertidal areas [5,6,7]. Management strategies have to be developed to maintain and/or restore intertidal flats, e.g., [8]. E.g., [9,10,11], show that dredged material can be re-used to feed tidal flats and promote salt marshes restoration. The disposal in estuarine channels can have long-term effects (order of years or decades) on the tidal flats and salt marshes morphodynamics [12]. A detailed understanding of the hydrodynamic and sediment transport mechanisms in intertidal areas is key to predicting their morphological evolution

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