J. Tobal-Cupul¹*; R. van de Vijsel¹; M. van Puijenbroek¹; S. Tas¹; M. Duran-Matute²; T. Hoitink¹

¹ Wageningen University and Research, The Netherlands; ² Eindhoven University of Technology, The Netherlands

^* Corresponding author: jessica.tobalcupul@wur.nl

Introduction

Salt marshes are wetlands flooded by high tide, formed by sediment exchange with tidal areas. They provide key ecosystem services, including coastal protection, biodiversity, carbon storage, and sediment retention. Keeping their elevation above sea level is vital for their long-term survival. While storms can cause erosion, they can also increase sediment supply to marsh platforms. However, it is not well understood which storm conditions, including storm direction and timing, mainly contribute to annual marsh accretion.

Several studies explore the role of storms in marsh sedimentation, focusing on short- and long-term deposition patterns and how storm magnitude and frequency influence them. Roman et al. (1997) observed that storms cause short-term accretion near inlets. Cortese et al. (2024) noted that long-term deposition depends on storm strength and frequency. FitzGerald et al. (2020) found that a single storm can deposit ice-driven sediment equivalent to about 15 years of accumulation, and Vincent et al. (2025) showed that category-four hurricanes promote vertical accretion. Despite these findings, how storm impacts accumulate throughout the year to contribute to annual marsh sedimentation remains unclear.

Objective and Methods

In this study, we investigate which storm conditions resuspend sediment on the mudflat and transport it to salt marshes during inundation. We hypothesize that higher suspended sediment levels occur when storm winds align with sediment-rich zones, such as tidal divides. When these winds coincide with salt marsh flooding, they facilitate efficient sediment deposition on the marsh platform. Focusing on the salt marshes of Ameland (Dutch Wadden Sea), where long-term annual sediment accretion data from 1985 to 2017 are available, and using available hydrodynamic time series, our goal is to identify the key factors influencing suspended sediment levels in the water flooding the marshes.

We integrate these field-based accretion measurements with hydrodynamic and suspended-sediment data available in the Wadden Sea. Additional suspended-sediment data from simulations in Sassi et al. (2015) will be used. They employed the process-based General Estuarine Transport Model (GETM) to simulate sediment transport within the Dutch Wadden Sea in 2009. The key hydrodynamic factors associated with high sediment concentrations during inundations will be identified for 2009 and then extended across the entire hydrodynamic time series, allowing a comparison with observed annual marsh accretion. This approach enables a direct assessment of storm-driven sediment delivery over multiple decades.

Results

Preliminary analysis of inundation events in the salt marshes shows that, in the high marsh, these are mainly caused by wind rather than astronomical tides. Most inundations, especially the more severe ones, originated from the NW and W directions, and were associated with high wind speeds. An open question is whether these intense inundation events occurred sequentially with High-SSC. Next, we will examine data from SSC collected through fieldwork, monitoring stations, and model outputs to identify key hydrodynamic factors, such as water level, waves, and wind, that are linked to High-SSC events.

References

Cortese, L., Zhang, X., Simard, M., & Fagherazzi, S. (2024). Storm Impacts on Mineral Mass Accumulation Rates of Coastal Marshes. Journal of Geophysical Research: Earth Surface, 129(3). https://doi.org/10.1029/2023JF007065

FitzGerald, D. M., Hughes, Z. J., Georgiou, I. Y., Black, S., & Novak, A. (2020). Enhanced, Climate-Driven Sedimentation on Salt Marshes. Geophysical Research Letters, 47(10). https://doi.org/10.1029/2019GL086737

Roman, C. T., Peck, J. A., Allen, J. R., King, J. W., & Appleby, P. G. (1997). AccretionofNewEngland_Roman1997. Estuarine, Coastal and Shelf Science, 45, 717–727. https://doi.org/10.1006/ecss.1997.0236

Sassi, M., Duran-Matute, M., van Kessel, T., & Gerkema, T. (2015). Variability of residual fluxes of suspended sediment in a multiple tidal-inlet system: the Dutch Wadden Sea. Ocean Dynamics, 65(9–10), 1321–1333. https://doi.org/10.1007/s10236-015-0866-2

Vincent, S., Wilson, C., Snedden, G. A., & Quirk, T. (2025). Time-Varying Rates of Organic and Inorganic Mass Accumulation in Southeast Louisiana Marshes: Relationships to Sea-Level Anomalies and Tropical Storms. Journal of Coastal Research, 41(3). https://doi.org/10.2112/jcoastres-d-24-00032.1.