Marine aggregate extraction has been operating at the current commercial scale since the early 1970s. In 2011 19.11million tonnes of marine aggregate (sand and gravel) were extracted from The Crown Estate-owned marine aggregate licences. The landings to England and Wales contribute over 20% of the total national demand for sand and gravel.
The area of seabed under licence is equivalent to 0.15% of the UK continental shelf area, but is reduced further by zones that are actively dredged. In 2010 the area of seabed dredged was 105.4 km2, although 90% of dredging effort was confined to just 37.63 km2537. Extrapolating the statistics calculated for the ten year review (1998-2007) of aggregate dredging538, shows that over the 20 year period 1998-2018 marine aggregate extraction will result in a total cumulative dredged footprint of 620 km2.
The distribution of regions containing marine aggregate licence areas in English and Welsh waters (Source: The Crown Estate)
There are currently 25 purpose-built marine aggregate dredgers operating in UK waters. They can carry 1500-8800 tonnes of aggregate cargo (dependent upon vessel type) per trip, delivering to over 70 wharfs throughout England and Wales, close to their point of use. A typical 5000 tonne cargo equals 250 lorry loads M0060. Thus marine sources significantly reduce road congestion and exhaust emissions.
There are six main regions of marine aggregates supply around the coast of England and Wales; Humber, East coast, Thames Estuary, South coast, Bristol Channel and north-east Irish Sea.
The location of dredging areas within these regions is the result of geological processes involved in the formation and deposition of the target resource (sands and gravels). The relict or fossil deposits were formed by the actions of prehistoric glaciers and rivers that occurred when sea levels were lower than they are at present. Sea-levels rose following the end of the last ice age, flooded the prehistoric landscapes, submerging the palaeo-river channels and deposits, resulting in their current marine setting.
In general East and South coast licence areas are targeted for production of gravel and sand cargoes and The Bristol Channel and West coast areas are targeted for sand only. This is a direct result of the markets in these regions, where shortfalls in land based supplies are filled by supply from marine sources.
A glossary of terms associated with marine aggregate operations has been produced by the British Marine Aggregate Producers Association and The Crown Estate M0062