Offshore Sand and Gravel Mining

This is a general overview of marine sand and gravel extraction. The origin of the relict or modern resource and the nature of the deposits are described, together with the related hydrodynamic and sedimentological regimes. Some important variations between countries are stressed in the marine aggregates production and usage. Details are provided on the prospecting methods for the identification of new resources, with emphasis on the ‘state-of-the-art’ sea bottom survey instrumentation. The article also focuses upon the principal techniques of extraction, that is, anchor and trailer suction dredging, and the associated features which are generated on the seabed (i.e., pits and furrows, respectively). The creation of such features, together with turbid plumes resulting from the extraction process, may induce significant environmental (physical and biological) impacts. These impacts are described in detail, while the recovery time of the changes is addressed. The article concludes with an overview of the supply and future of marine aggregate dredging.