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Predicting dominance of sand transport by waves, tides and their interactions on sandy continental shelves
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  • Erin Victoria King,
  • Daniel C Conley,
  • Gerhard Masselink,
  • Nicoletta Leonardi
Erin Victoria King
University of Plymouth

Corresponding Author:erin.king@plymouth.ac.uk

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Daniel C Conley
University of Plymouth
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Gerhard Masselink
Plymouth University
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Nicoletta Leonardi
University of Liverpool
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Waves and tidal currents resuspend and transport shelf sediments, influencing sediment distributions and bedform morphology with implications for various topics including benthic habitats, marine operations, and marine spatial planning. Shelf-scale assessments of wave-tide-dominance of sand transport tend not to fully include wave-tide interactions (WTI), which non-linearly enhance bed shear stress and apparent roughness, change the current profile, modulate wave forcing, and can dominate net sand transport. Assessment of the relative contribution of WTI to net sand transport requires computationally/ labour intensive coupled numerical modelling, making comparison between regions or climate conditions challenging. Using the Northwest European Shelf, we show the dominant forcing mode and potential magnitude of net sand transport is predictable from readily available, uncoupled wave, tide and morphological data in a computationally efficient manner using a k-Nearest Neighbour algorithm. Shelf areas exhibit different dominant forcing modes for similar wave exceedance conditions, relating to differences in depth, grain size, tide range, and wave exposure. WTI dominate across most areas in energetic combined conditions. Over a statistically representative year, meso-macrotidal areas exhibit tide-dominance, while shallow, finer grained, amphidromic regions show wave-dominance, with WTI dominating extensively >30m depth. Seabed morphology is strongly affected by sediment transport mode, and sand wave geometry varies significantly between predicted dominance classes with increased length and asymmetry, and decreased height, for increasing wave-dominance. This approach efficiently indicates where simple non-interactive wave and tide processes may be sufficient for modelling sediment transport, and enables efficient inter-regional comparisons and sensitivity testing to changing climate conditions with applications globally.