Wave-induced sand re-suspension at dredged gravel pits based upon hydrodynamic measurements (Tromper Wiek, Baltic Sea)

Garel, Erwan and Lefebvre, Alice (2010) Wave-induced sand re-suspension at dredged gravel pits based upon hydrodynamic measurements (Tromper Wiek, Baltic Sea). Journal of Coastal Research, (51), 195-204. (doi:10.2112/SI51-018.1).

Abstract

ABSTRACT
Gravel pits created by anchor hopper dredging may affect regional sediment transport patterns by trapping sediments. In turn, this may cause -or enhance- erosion at the adjacent coastline. Reliable assessment of such impacts requires a good understanding of the hydro-sediment dynamic processes acting at dredged pits. This paper examines the processes for sand re-suspension from pressure, current and turbidity data collected inside and outside a single dredged pit, in a non-tidal environment (Tromper Wiek, Baltic Sea). The data confirm the generally weak sediment dynamics in the area, with waves being the main hydrodynamic agent for sediment re-mobilization. Comparisons with historical data indicate a small number of sediment re-suspension events (<15%), over a 37 months-long period, without significant difference inside and outside the pit. Suspended sediment concentration profiles are predicted inside the studied pit by a simplistic model, tuned to over-estimate sediment re-suspension. The results suggest that the depth of the excavation should be very shallow (<1 m) for the bed material to be frequently extracted out by waves, and redistributed over the area. With pits up to 7 m-deep within the extraction zone, we conclude that a significant fraction of sediment is trapped over the long-term period (years).

This record has no associated files available for download.

Contributors

Download statistics