Trá an Doilin, Maerl Beach in Carraroe

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We recently did a modelling study on the sediment mobility of maerl in Galway bay, utilising coupled hydrodynamic-wave-sediment transport models. This is the final part of my PhD in maerl sediment dynamics. Sediment mobility in its simplest form is the percentage of time grains of a particular size are mobile during  a tidal cycle (Idier et.al., 2010). This study focuses on the sediment mobility of maerl in particular, utilising coupled hydrodynamic-wave-sediment transport models to model the oceanography during calm and storm conditions and the resulting sediment transport. Sediment mobility models are another way of quantifying the disturbance of the seafloor as a result of currents, waves and combined wave-currents. This study calculates two sediment mobility indices, the Mobilization Frequency Index (MFI) and the Sediment Mobility Index (SMI), related to the magnitude and frequency of disturbance events (Li et.al, 2015). The residual currents, which are the part of the current remaining after removing the oscillatory tidal component, show that maerl prefers intermediate mobility environments and is often found at the periphery of the residual current gyres. Sediment mobility maps can be used to inform marine spatial planning for the management of both live and dead (fossil) maerl beds, as a result of climate change or anthropogenic activity. The full research paper, Joshi et.al. 2017, can be found here.

References

Idier, D., Romieu, E., Pedreros, R., & Oliveros, C. (2010). A simple method to analyse non-cohesive sediment mobility in coastal environment Continental Shelf Research, 30(3-4), 365-377 DOI: 10.1016/j.csr.2009.12.006

Joshi, S., Duffy, G., & Brown, C. (2017). Mobility of maerl-siliciclastic mixtures: Impact of waves, currents and storm events Estuarine, Coastal and Shelf Science DOI: 10.1016/j.ecss.2017.03.018

Li, M., Hannah, C., Perrie, W., Tang, C., Prescott, R., Greenberg, D., & Rygel, M. (2015). Modelling seabed shear stress, sediment mobility, and sediment transport in the Bay of Fundy Canadian Journal of Earth Sciences, 52 (9), 757-775 DOI:10.1139/cjes-2014-0211

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