Sediment Transport due to Trawling in La Fonera Submarine Canyon - A Numerical Modelling Approach

The process of resuspension by bottom trawling leads to recurrent transfer of sediment from shallower to deeper areas, and occurs practically worldwide. Recent studies have shown the importance of trawling as a driver of sediment transfer in canyons. Our aim is to assess trawling impact on sediment dynamics in La Fonera submarine canyon (NW Mediterranean). Our methodology combines inverse modelling and the implementation of a numerical process-based model, and allows us to simulate trawling-induced flows in the canyon on the basis of trawling fleet activity (derived from Vessel Monitoring System data). The model simulates turbidity current hydrodynamics and deposition for events whose magnitude and initial volume concentration is defined from the inverse analysis. Mooring data in the axis of a tributary valley is used to validate the model hypothesis. Based on the good agreement found between modelled transport and measurements at the mooring site, we have quantified fishing activity over the fishing grounds and obtained the propagation patterns of the resuspended sediment towards the canyon axis and beyond. Trawling-induced sediment flows lead to the development of new trawl-driven depocentres.