VESSEL-MOUNTED HYDROPHONE MEASUREMENTS TO ESTIMATE BEDLOAD TRANSPORT OF COARSE SHELLY SEDIMENTS

摘要

Assessing bedload transport is of particular interest to understand the morphodynamics of active sedimentary systems in coastal areas and remains a scientific challenge. Here we present results illustrating an original approach aimed at obtaining bedload transport values with an extended temporal and spatial coverage, and consisting in recording passive acoustics data from a vessel drifting over the site of interest. It was tested during contrasting hydrodynamic forcing conditions on a shallow submarine dune bank composed of coarse shell sand. Root mean square pressure (P_(rms)) was computed on the [60–80] kHz frequency band, corresponding to bedload transport. P_(rms) values were then inverted using an empirical formulation (Thorne, 1986) to estimate the number of moving grains on the seafloor N. Results are promising, with N showing a clear dependency on the magnitude of the current at the bottom of the water column extracted from numerical simulations with a high-resolution hydrodynamic model.