Winds of Opportunity: Intertidal Flat Hydrodyanmics & Morphodynamics

Intertidal flats and salt marshes are critical ecosystems offering significant services but face degradation due to anthropogenic pressures. To mitigate this, restoration efforts like the "Mud Motor" have been introduced, where fine sediments dredged from ports are strategically relocated to nourish intertidal areas and salt marshes. This approach enhances ecological development while reducing maintenance dredging. This dissertation, conducted within the Mud Motor Pilot Project (2016–2017) in the Dutch Western Wadden Sea, investigates the role of wind in the hydro-morphodynamics of intertidal flats, focusing on sediment dynamics and morphological evolution.

Field campaigns across three years (2016–2018) in the Dutch Wadden Sea provided comprehensive datasets on water levels, sediment concentrations, currents, waves, and bed-level changes. Analysis revealed wind's significant influence on hydrodynamics. Opposing winds to tidal currents could reverse tidal flows, especially in higher intertidal zones. A newly developed analytical model validated with field data quantified the nonlinear interactions between wind- and tide-driven flows.

The findings emphasize the pivotal role of wind direction in sediment transport. Low to moderate winds in alignment with tidal residual transport facilitate sediment accumulation in low-energy zones, while short periods of opposing winds resuspend and redistribute this sediment. These wind-driven sediment fluxes critically shape short- and long-term sediment dynamics in systems like the Wadden Sea.

Moreover, the research identifies a "window of opportunity" for tidal flat accretion, driven by temporal sequences of sediment deposition and over-consolidation under favorable wind conditions. Sediment gains sufficient strength to resist erosion only through prolonged drying processes influenced by wind-driven water level set-down.

This study underscores the complexity of wind's impact on intertidal ecosystems, offering insights for restoration projects to better integrate natural processes. By accounting for wind effects, these projects can improve predictions and identify new restoration opportunities.