Bedload Transport of Sediment Mixtures in Shelf Seas
Connor McCarron – Bangor University
- Katrien Van Landeghem
- Jaco Baas
- Laurent Amoudry
- Ian Taylor
- Alan Roberts
The morphology of the seabed is controlled primarily by bedload sediment transport processes while the UK’s shelf seas are comprised of mixed sediments (i.e. sand and gravel) due to deposition of reworked sedimentary material by paleo-glacial processes. The presence of these sediment mixtures causes a “hiding-exposure” effect where smaller grains are sheltered or “hidden” by larger, more “exposed” grains. This changes the efficiency of the flow in mobilising different grain sizes affecting bedload transport and seabed morphodynamics and remains to be quantified in shelf-seas. This project will attempt to quantify this effect with the aim to improve the predictive ability of current bedload transport formulae, with implications for the safety of offshore developments, coastal erosion and for stakeholders or consumers of shelf sea resources.
Initial work will include acoustic techniques (multi-beam echosounders, sidescan sonars and sub-bottom profilers) and sediment sampling. This will inspire flume tank experiments to quantify “hiding-exposure” using sediment traps and an array of ultra-sonic transducers and velocity profilers to monitor current velocities and bed evolution. Using the best results, existing bedload transport formulae will be adapted and tested in the NOC-L’s 180m POLCOM model; outputs will be cross validated with a geophysical investigation of bedforms on mixed sediment beds of Liverpool Bay.
Why This Subject Matters to Them
“My interest in shelf-seabed morphodynamics was first sparked during my undergraduate studies at University of Ulster where I participated on various research and student training cruises investigating shelf seabed morphodynamics on the north coast of Ireland, glacial and non-glacial sediment transport in the Rockall Trough, and sea level minima in the Irish Sea. This experience exposed me to various aspects of marine geoscience and further developed my interest in the field. Subsequently, I applied to study MSc Applied Marine Geoscience at Bangor University. During my master’s degree I gained extensive theoretical knowledge and practical experience of various geophysical surveying techniques, for marine and terrestrial applications, at a much higher level than I had previously experienced. The PhD project that I am now completing provides a multidisciplinary approach to improve the predictive ability of bedload transport formulae and bedform development models integrating my interest in shelf-seabed morphodynamics, the associated sediment transport processes and the use of geophysical techniques for discriminating seabed processes.”