Christchurch Mudeford Sandbank is in Christchurch Bay on the Dorset coast. The bay
is approximately 13 kilometres wide from Hengitsbury Head to Hurst Castle. Mudeford
Sandbank is a sandbank beach resort, approximately one and a half kilometres wide,
with views across the harbour.
Within the catchment there are storm, emergency and surface water outfalls that discharge
to the Stour and Avon rivers. The operation of the overflows can lead to a drop in
bathing water quality.
Wessex Water made improvements in 1994 to reduce the frequency of emergency overflows
from two combined sewer overflows (CSO) which discharge to the River Stour. Improvements
to the treatment capacity and storm storage at Holdenhurst Sewage Treatment Works
(STW) were also completed at that time. Ultraviolet (UV) disinfection was provided
at Christchurch STW by May1998 and by April 2001, UV treatment and additional storm
storage was installed at Holdenhurst STW.
Improvements to an emergency overflow from a pumping stations at Iford were completed
in 2002. The storm discharge from Christchurch STW was improved by April 2003, and
the STWs at Wimborne, Kinson, and Palmersford received UV disinfection by the end
of 2003. The CSO at Tuckton High Street was rebuilt and made larger by April 2004
and the storm discharge from Kinson STW was improved by April 2005.
For the four year (2020-2023) assessment period where data is available, seaweed (macroalgae)
was assessed as being sufficient to be objectionable for 13% of visits, with 79% of
visits noting the presence of seaweed (macroalgae). This bathing water does not have
a history of large amounts of seaweed (macro algae).
For the four year (2020-2023) assessment period where data is available, phytoplankton
(microscopic algae) was not assessed as being sufficient to be objectionable, but
was observed as being present on 8% of visits. Phytoplankton (microscopic algae) naturally
increase in number at certain times of the year. This process is known as a phytoplankton
bloom. This bathing water does not have a history of phytoplankton blooms.
The risks to human health from contact, ingestion or inhalation with marine algae
that currently occur in UK coastal waters are considered to be low. However, some
individuals may be more sensitive and display some reactions.
A common marine algae found in UK coastal waters is Phaeocystis, which is often mistaken
for sewage as it forms foam and a brown scum, but it is non-toxic.
There are no active pollution risk forecasts made at this bathing water. However any
bathing water has the potential to be affected by a pollution incident and if this
occurs a pollution risk warning with associated advice against bathing will be issued
on this website.
Streams and rivers are typically affected by human sewage, animal slurry and runoff
from roads. This bathing water is close to the mouth of the Rivers Stour and Avon
which flow into Christchurch Harbour. The natural effects of wind and tide outside
the harbour can mean that water quality at the beach is impacted by the quality of
the rivers Stour and Avon. Long-term monitoring by the Environment Agency has shown
that the rivers may affect water quality after periods of heavy rainfall.
All the significant sewage treatment works in the lower catchment receive UV disinfection,
and further up the catchment there are smaller, treated, continuous discharges. These
discharges are designed to protect bathing water quality.
Environment Agency samplers make observations of litter present on the beach at every
visit, this includes assessments of sewage debris, litter and tar. At Christchurch
Mudeford Sandbank East for the four year (2020-2023) assessment period where data
is available, sewage debris was not noted at this site. Litter was assessed as being
sufficient to be objectionable for 8% of visits, with 71% of visits noting the presence
of litter. Tarry residue was not noted at this site.
The largely agricultural catchments of the rivers Stour and Hampshire Avon have significant
areas of land used for livestock. During and after periods of heavy rainfall, runoff
from agricultural land is greatly increased, and the quality of the bathing water
can be reduced.
The Environment Agency are working with Natural England and farmers on Catchment Sensitive
Farming programmes to encourage better farming practices and improve water quality
in the surrounding areas.
The catchment surrounding Christchurch Mudeford Sandbank East is approximately 300,000
hectares and includes the Hampshire Avon and the River Stour. The Avon is approximately
95km long and rises in Wiltshire in the Vale of Pewsey. It then flows south across
Salisbury Plain through Durrington, Amesbury and Salisbury where all the significant
tributaries of the Avon come together, including the Nadder, Wylye, Bourne and Ebble.
The upper Avon catchment includes the undulating, chalk downlands of Salisbury Plain,
which are cut by steep combes and river valleys. The steep catchment means rain runs
off rapidly into the river. To the south of Salisbury the Avon enters the rolling
farmland of the Hampshire Basin, flowing along the western edge of the New Forest
through Fordingbridge and Ringwood. The Avon meets the River Stour at Christchurch
and flows into Christchurch Harbour and the English Channel at Mudeford.
The River Stour is approximately 96km long and flows east from Stourhead in Wiltshire
through the Blackmore Vale and the towns of Gillingham and Sturminster Newton, where
it is joined by the River Lydden. The river breaks through the chalk ridge of the
Dorset Downs at Blandford Forum, and flows southeast into the heathlands of south
east Dorset. At Wimborne Minster it is joined by the River Allen, and meets the River
Avon at Christchurch.
Outside the urban areas of Bournemouth, Poole and Christchurch, the catchment is mainly
agricultural with more than 50 farms.
Seaweed (macroalgae) and phytoplankton (microscopic algae) are a natural part of the
marine and freshwater environment. Below we note whether these have been recorded
in quantities sufficient to be a nuisance.
The majority of sewers in England are “combined sewers” and carry both sewage and
surface water from roofs and drains. A storm overflow operates during heavy rainfall
when the sewerage system becomes overwhelmed by the amount of surface water. The overflow
prevents sewage from backing up pipes and flooding properties and gardens. An emergency
overflow will only operate infrequently, for example due to pump failure or blockage
in the sewerage system.
Heavy rain falling on pavements and roads often flows into surface water drains or
highway drains, ending up in local rivers and ultimately the sea. The quality of bathing
water may be adversely affected as a result of such events.
It is the Environment Agency role to drive improvement of water quality at bathing
waters that are at risk of failing higher standards. It is natural for water to run
off the land to the sea. Water quality at a bathing water is dependent upon the type
and area of land (the catchment) draining to the water and the activities undertaken
in that catchment.