Highcliffe is a popular resort beach on the east Dorset coast, looking out across
Christchurch Bay with views of the Isle of Wight to the east. The shingle beach has
numerous groynes and a moderate slope, flattening to shallow sandy flats that are
exposed when the tide retreats. Behind the beach are cliffs and a shoreline promenade
which provides access to the town and to the coast road at the top of the cliff.
Prior to 1997 treated effluent from Barton on Sea Sewage Treatment Works was disinfected
with hypochlorite during summer periods and discharged via an outfall 4 km from the
bathing water sampling site. On rare occasions this might have affected bathing water
quality. This discharge ceased prior to the 1997 bathing season when flows were diverted
to Pennington Sewage Treatment Works to receive further treatment.
Very high results observed on 13 July 2009 were investigated. They were associated
with very heavy rainfall which caused a large freshwater input into the bathing water.
For the four year (2020-2023) assessment period where data is available, seaweed (macroalgae)
was not assessed as being sufficient to be objectionable, but was observed as being
present on 37% of visits. The shore can become covered with seaweed, depending on
tides and the weather. Groynes, rocks and other fixed objects may have a covering
of seaweed which can be slippery.
Modern sewerage systems have two separate systems, one takes foul sewage to sewage
treatment, the other takes rainwater runoff through surface water drains to rivers,
lakes and the sea. Misconnections occur when waste water pipes are plumbed into surface
water drains instead of the foul water sewerage system. This can give rise to pollution
when the waste water is discharged directly to the environment through the surface
water drain. For example, a washing machine or toilet may be incorrectly plumbed so
that it discharges to the surface drain rather than the foul sewage drain.
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 2% of visits. Microscopic algae (phytoplankton) increase
in number at certain times of the year. This process is known as a phytoplankton bloom.
Blooms of phytoplankton can result in the water appearing discoloured or a foam forming
on the water.
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.
The Chewton Bunny stream, which receives urban run-off, inputs into the bathing water.
Christchurch Harbour, which receives riverine and other inputs, inputs 5.5 km to the
west. These sources may contribute to reduced bathing water quality after heavy rainfall.
Pennington Sewage Treatment Works discharges further treated sewage 12 km from the
bathing water and is designed to protect bathing water compliance. This discharge
is scheduled to receive ultraviolet disinfection to protect nearby shellfish beds
in the near future, which will provide further protection to the bathing water. Christchurch
Harbour, which flows to sea 3.5 km west of the bathing water, receives further treated,
ultraviolet disinfected effluent from several sewage treatment works as well as inputs
from storm overflows. These discharges to Christchurch Harbour have been designed
to have minimal impact on bathing water compliance.
Environment Agency samplers make observations of litter present on the beach at every
visit, this includes assessments of sewage debris, litter and tar. At Highcliffe 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 2% of visits, with 58% of visits noting the presence of litter. Tarry residue
was not noted at this site.
The natural drainage (hydrological) catchment surrounding the bathing water is approximately
950 hectares and drains into the Chewton Bunny stream which discharges into the bathing
water via an outfall 450 metres east of the sampling site. The top of the catchment
is rural while the lower catchment is predominantly urban. The steep slopes in the
catchment cause water to run off the land into the stream and into the bathing water
very quickly.
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.
