Dynamics of Sorted Bedforms on a Shallow Infralittoral Prograding Wedge Influenced by Dredging (El Masnou, NW Mediterranean)

Abstract

The dynamics of sorted bedforms on the inner shelf off El Masnou coast (NW Mediterranean) was investigated based on time-series of swath bathymetry and backscatter and grain-size analysis of grab samples spanning 4 years (2006–2009). The sorted bedforms are superimposed on the edge of a shallow infralittoral wedge with an orientation nearly perpendicular to the slope and oblique to the shoreline. They commonly display lateral asymmetry in backscatter, with the high backscatter domain on the depression and on the eastern side of the bedforms. The short-term evolution of these bedforms evidenced changes in the location of the bedform boundaries, widening and narrowing, predominant migration towards the southwest in the direction of the net alongshore sediment transport, and formation of new sorted bedforms. The analysis of repeated bathymetries also revealed the impact of dredging activities on the sorted bedforms, resulting in the destruction of part of the bedform pattern, which started to recover over the subsequent months. This behaviour suggests that the sorted bedforms off El Masnou are persistent and dynamic over a 4 year time span.