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 Lagoons &
Wetland, Alderney
The
lagoons project at Alderney represents the first example of a SUDS
(Sustainable Drainage Systems) in the Bourne stream
catchment.
Installed by Borough of Poole Leisure Services, and funded by English Nature, they are now the
subject of detailed study and monitoring to assess their effect on both water quality and wildlife habitat.
Phase One - Lagoons
March
2000 - a series of five on-line lagoons (ponds) were created in the upper reaches of the identifiable watercourse
immediately downstream of Ringwood Road and planted with reeds. Total area approximately
one hectare.
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Site
prepared for lagoons (above left) - and after 6 months (above right) |
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Phase
One provided some initial treatment to the flows from Ringwood Road
(primarily highway run-off).
During tree clearance here an old and
leaking foul sewer was discovered and is understood to have generated
overspill into the watercourse; this has now been rectified.
The
lagoons were originally planted with 450m2 Phragmites australis
(Common Reed) but was soon eaten by the two ponies that graze
the area.
They
have now been colonised by Typha latifolia (commonly known
as Reed Mace) (right), which can also be found at the ponds
upstream of Scott Road and at Bourne
Valley Park.
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Compare the plan with an
aerial photo of the lagoons taken soon after their
creation (click to enlarge)
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Phase Two -
Wetland
March
2001 - a shallow off-line wetland was constructed a short distance upstream of Phase I (see plan). Total area
approximately 2500m2.
Phase
II now provides the initial treatment for the highway run-off from
Ringwood Road, and is intended to deal with first-flush waters
containing a high level of pollutants. On leaving the wetland area stream water is
diverted into Phase I for further treatment.
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Wetland site after tree clearance 2001 |
Wetland well vegetated in April 2003 |
Since
completion of Phase I, students from Bournemouth University have been
monitoring and evaluating the success of the lagoons and wetland.
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Kerry
Fleet, BSc (Hons) Environment Protection, Bournemouth University (2002) The Use of Constructed Wetlands to Improve the Water
Quality of the Bourne Stream, Dorset.
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Robert
Aquilina, MSc Environmental Quality, Bournemouth University (2003) Habitat
Quality in Constructed Wetlands as part of a Sustainable Urban Drainage
System (SUDS).
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Gary
Broocks, BSc (Hons) Environmental Protection, Bournemouth
University (2004) Constructed
Wetlands on the Bourne Stream, Dorset: An Assessment of Water Quality
and Highway Run-Off
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