|
Marine Aggregates (Sand and Gravel)
Sublittoral sand and gravel habitats occur in
a wide variety of environments, from sheltered (sea lochs, enclosed
bays and estuaries) to highly exposed conditions (open coast).
The particle structure of these habitats ranges from mainly sand,
through various combinations of sand and gravel, to mainly gravel.
While very large areas of seabed are covered by sand and gravel
in various mixes, much of this area is covered by only very thin
deposits over bedrock, glacial drift or mud. The strength of tidal
currents and exposure to wave action are important determinants
of the topography and stability of sand and gravel habitats.
UK
Habitat Action Plan: Sublittoral sands and gravels
Exploitation
Each year in Ireland, many hundreds of thousands of tonnes of
sand and gravel "aggregates" are extracted from sedimentary deposits
on-land, primarily for use in construction and road building.
In coastal waters, marine aggregates are extracted from the seabed
for use in beach replenishment and harbour development infill.
As economically viable on-land sources of aggregates in Britain
and Ireland become increasingly depleted, the pressure grows for
marine aggregates deposits to be opened-up for exploitation.
There are substantial marine sand and gravel resources in Irish
coastal waters, particularly in the southern Irish Sea in offshore
bars that extend from Dublin Bay southwards, parallel to the coast,
to an area off Carnsore Point, County Wicklow. Near-shore sandbanks
off counties Wicklow, Wexford and Cork have been exploited for
some years by local authorities for beach replenishment and as
infill for harbour development (Marine Institute 1999). OSPAR
(2000) states that "no information is currently available
on the environmental effects of extraction at these specific sites".
At present, no commercial marine sand and gravel extraction takes
place in Ireland (ICES 2005). Apart from dredging works at ports,
harbours and marinas, the most recent marine aggregate extraction
activities licensed under the Foreshore Acts are:
- In 1997, an estimated one million cubic metres of sand and
gravel were extracted from Cork Harbour for use as back-fill
in a combined tunnelling and harbour development project (Marine
Institute 1999).
- In 1999/2000 there was no licensed commercial marine aggregate
extraction from State-owned foreshore, i.e. the land and seabed
between the high water mark and the 12 nautical mile limit of
the territorial sea (OSPAR 2000).
- During 2000/2001, a licensed extraction took place of 234,767m³
of gravel from the Codling Bank in the Irish Sea to provide
aggregates for coastal protection (beach replenishment) works
at Bray, County Wicklow.
IMAGIN project
According to the ICES Working Group on the Effects
of Extraction of Marine Sediments on the Marine Ecosystem (WGEXT)
Report 2005:
The Irish Department of Communications Marine and Natural Resources
(DCMNR) have indicated that they look forward to collaboration
with all of the Irish and Welsh partners in the course of this
initiative and to reviewing the output of the IMAGIN project,
as a key input in the development of Irish policy for this resource
area. In this context the DCMNR anticipate that the process of
actual policy development is likely to be completed within a period
of 2 years after the closure date of the IMAGIN project in February
2007.
The aim of the Ireland/Wales collaborative research project IMAGIN
(Irish Sea Marine Aggregates Initiative 2005-2007) is "to
facilitate the evolution of a strategic framework within which
development and exploitation of marine aggregate resources from
the Irish Sea may be sustainably managed with minimum risk of
impact on marine and coastal environments, ecosystems and other
marine users." Key outputs from the project will be:
- A digital marine aggregate management decision support system
and a database of geophysical, ecological and associated datasets.
This will be linked to a sediment dispersion hydrodynamic model.
- A cost-benefit analysis of marine aggregate extraction in
the context of other extraction methods currently used by the
aggregate supply industry.
- A regional bio-sedimentary environmental assessment and a
set of digital and hardcopy maps.
- Documents detailing the strategic framework and scientific
rationale geared to-wards underpinning future policy development
on marine aggregates for the southern Irish Sea area (ICES 2005).
For further information see: IMAGIN
Wales workshop proceedings (9 February 2006)
|
 |
What does it mean?
Try the pop-up Glossary |
|
