Sediment dynamics information provide vital insights into the important role of oceanographic forcing factors on habitat distribution; yet remains an under-utilized physical surrogate in marine habitat mapping studies. An integrated oceanographic and geophysical analyses of dynamic processes combining sediment mobility indices, obtained from coupled-hydrodynamic- wave sediment transport models; with seabed classification has been made at Galway Bay, Ireland.
Maerl or rhodolith coralline red algae beds are abundant in Galway Bay and these beds represent more than 65% – 70% of the maerl habitats in Ireland (De Grave and Whitaker, 1999). Maerl beds are particularly affected by hydrodynamics and increased storminess resulting in recurrent disturbance of the benthic habitat patch during winter storms. Live maerl beds are biodiversity rich coastal habitats and form subtidal and intertidal banks and open marine beds. Dead maerl beds of the branched maerl morphotype are considered to be biogenic sediment with form dense biogenic gravel debris beaches.
Sediment mobility modelling is of importance to a range of disciplines including sediment dynamics, marine conservation, coastal engineering, and renewable energy (Harris and Coleman, 1998; Idier et al., 2010; Li et al., 2015, Joshi et al, 2017a, Coughlan et al. 2021). It is based on the fundamental quantity of bed shear stress and the impact of pure currents, wave-only, wave-induced currents or combined wave-current flow on surficial sediments.
Multibeam backscatter from the INFOMAR national seabed mapping program of Ireland have been utilized for seabed classification using the new machine learning and deep learning libraries in ArcGIS Pro and Python.
An integrated interpretation of the dynamic processes happening at the seafloor is made as a result of the combined wave-current induced disturbance regime during storm conditions. Implications for future conservation management of maerl beds impacted by increased storminess and anthropogenic activity are discussed.
Coughlan, M., Guerrini, M., Creane, S., O’Shea, M., Ward, S.L., Van Landeghem, K.J.J., Murphy, J., Doherty, P., 2021. A new seabed mobility index for the Irish Sea: Modelling seabed shear stress and classifying sediment mobilisation to help predict erosion, deposition, and sediment distribution. Continental Shelf Research 229, 104574.
De Grave, S., Whitaker, A., 1999. A census of maerl beds in Irish waters. Aquatic Conservation: Marine and Freshwater Ecosystems 9,303-311.
Harris, P.T., Coleman, R., 1998. Estimating global shelf sediment mobility due to swell waves. Marine Geology 150, 171177.
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, 365–377.
Joshi, S., Duffy, G.P., Brown, C., 2017a. Mobility of maerl-siliciclastic mixtures: Impact of waves, currents and storm events. Estuarine, Coastal and Shelf Science 189, 173–188.
Li, M.Z., Hannah, C.G., Perrie, W.A., Tang, C.C.L., Prescott, R.H., Greenberg, D.A., 2015. Modelling seabed shear stress, sediment mobility, and sediment transport in the Bay of Fundy. Canadian Journal of Earth Science. 52, 757–775.
Joshi, Siddhi. (2022). Integrating sediment dynamics into habitat mapping approaches using sediment mobility indices and seabed classification in Galway Bay, Ireland. GeoHab 2022, Venice. https://lnkd.in/e9vHBu8v