Porthcothan Bay is on the north coast of Cornwall. It is a rural, sheltered sandy
bay, approximately 400 metres wide, backed by sand dunes. There is a stream that flows
across the beach. Porthcothan is popular with tourists and surfers and is patrolled
by lifeguards during the day in the summer.
The Environment Agency carried out additional monitoring in the Porthcothan Stream
in 2010, and will make recommendations for further improvements to protect and improve
the bathing water quality.
For the four year (2015-2018) assessment period where data is available, seaweed (macroalgae)
was assessed as being sufficient to be objectionable for 4% of visits, with 82% of
visits noting the presence of seaweed (macroalgae). The bathing water can become covered
with large amounts of seaweed, depending on tides and the weather. This bathing water
does not have a history of large amounts of seaweed, but that it can be noticeable
from time to time.
For the four year (2015-2018) assessment period where data is available, phytoplankton
(microscopic algae) was not noted at this site. 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.
Streams and rivers are typically affected by human sewage, animal slurry and runoff
from roads. The Porthcothan Stream flows onto this beach. The Environment Agency have
monitored the stream between 1993 and 2014, and found that water quality is temporarily
worse after heavy rainfall.
Environment Agency samplers make observations of litter present on the beach at every
visit, this includes assessments of sewage debris, litter and tar. At Porthcothan
for the four year (2015-2018) assessment period where data is available, sewage debris
was not noted at this site. Litter was assessed as being sufficient to be objectionable
for 1% of visits, with 54% of visits noting the presence of litter. Tarry residue
was not noted at this site.
There are approximately 20 farms in the catchment, most of which are used for livestock.
During and after periods of heavy rainfall, runoff to the Porthcothan Stream from
agricultural land is greatly increased, and the quality of the bathing water can be
reduced.
The catchment surrounding Porthcothan is approximately 1,500 hectares. The Porthcothan
Stream is approximately seven kilometres (km) (13.5km long including tributaries)
and rises close to Bear’s Downs. The steep catchment means rain runs off rapidly into
the stream.
The catchment is agricultural, with around 20 farms. The rural areas are a patchwork
of improved grassland and arable. The catchment includes the settlements of St Eval
and Porthcothan as well as several smaller villages and at least four caravan sites.
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.
