Wave Generation of Gravity-Driven Sediment Flows on a Predominantly Sandy Seabed
Raúl P. Flores (Universidad Técnica Federico Santa María, University of Washington)
Sabine Rijnsburger (TU Delft - Environmental Fluid Mechanics)
Saulo Meirelles (TU Delft - Coastal Engineering)
Alexander R. Horner-Devine (University of Washington)
Alejandro J. Souza (CINVESTAV Unidad Merida)
Julie Pietrzak (TU Delft - Environmental Fluid Mechanics)
Martijn Henriquez (TU Delft - Coastal Engineering)
AJHM Reniers (TU Delft - Environmental Fluid Mechanics)
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Abstract
Wave-supported gravity flows (WSGFs) generate rates of sediment flux far exceeding other cross-shelf transport processes, contributing disproportionately to shelf morphology and net cross-shelf fluxes of sediment in many regions worldwide. However, the conditions deemed necessary for the formation of WSGF limit them to a narrow set of shelf conditions; they have been observed exclusively in regions where the seabed consists of very fine-grained sediment and typically co-occur with nearby river flood events. Here we document the occurrence of a WSGF event on a predominantly sandy seabed and in the absence of a preceding river flood. Our measurements confirm that the dynamics are governed by the friction-buoyancy balance observed in other WSGF and that WSGF can form in mixed grain-size environments and transport high concentrations of sand. The occurrence of WSGF on a predominantly sandy seabed suggests that they may occur under a much wider range of conditions and, given the global prevalence of sandy shelves, they may be a more frequent and more ubiquitous feature of shelf dynamics than previously thought.