2024 Bathing Water Profile for Downderry
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Downderry is on the south coast of Cornwall. It is a remote sand, shingle and pebble beach, approximately 1.1 kilometres wide, backed by cliffs. There are two streams that flow across the beach to the sea.
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Cornwall
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Cornwall
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The Environment Agency periodically carries out additional catchment monitoring, and this is used to make recommendations for further improvements to protect and improve bathing water quality.
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There is an emergency/storm overflow from the Downderry pumping station that discharges into the sea approximately 560m south east of the bathing water. The operation of the overflow can lead to a temporary drop in bathing water quality.
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The sewage treatment scheme for Seaton and Downderry, which provides secondary treatment and ultraviolet (UV) disinfection, was completed by South West Water in early 1998. The scheme included the removal of untreated discharges which were retained as combined sewer overflows (CSO), and the construction of a sewage treatment works at Seaton. Storm overflow event duration monitoring (EDM) was installed at Downderry pumping station by December 2011.
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The urban area of Downderry immediately behind the beach is served by a combined (surface and sewer) system.
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For the four year (2020-2023) assessment period where data is available, seaweed (macroalgae) was assessed as being sufficient to be objectionable for 25% of visits, with 75% 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 has a history of large amounts of seaweed.
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Wrongly connected domestic waste water pipes can also affect the bathing water quality. We have checked the local sewerage system for misconnections. 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.
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For the four year (2020-2023) 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.
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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.
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2024 Bathing Water Profile for Downderry
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2024-09-30
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2024-05-01
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Streams and rivers are typically affected by human sewage, animal slurry and runoff from roads. The Downderry Stream enters the sea at this beach. Another stream known as Treliddon Lake also enters the sea at the rocks to the east of the Environment Agency monitoring point. The Environment Agency have monitored the Downderry Stream between 1990 and 2012, and found that water quality is temporarily worse during and after heavy rainfall.
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Environment Agency samplers make observations of litter present on the beach at every visit, this includes assessments of sewage debris, litter and tar. At Downderry for the four year (2020-2023) assessment period where data is available, sewage debris was not noted at this site. Litter was not assessed as being sufficient to be objectionable, but was observed as being present on 32% of visits. Tarry residue was not assessed as being sufficient to be objectionable, but was observed as being present on 2% of visits.
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During and after periods of heavy rainfall, runoff to the Downderry Stream from agricultural land is greatly increased, and the quality of the bathing water can be reduced.
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The catchment surrounding Downderry is approximately 60 hectares. The stream at Downderry beach starts inland at Lower Deviock and flows for approximately 1.2km through the village of Downderry before entering an underground channel at the beach next to the Environment Agency monitoring point, Downderry beach stretches along the coast in both directions, with two further streams entering the sea at the beach 500 metres (m) and 795m east of the Environment Agency monitoring point. The steep catchment means rain runs off rapidly into the stream. Land use is part arable and improved grassland, with two farms, and Downderry village at the coast.
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Downderry
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Downderry
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Sampling point at Downderry
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231470
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50.360983061814046
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-4.370798313705646
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53920
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Sampling point at Downderry
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p152 dT23 h59 m59 s
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2024 05 01 t00:00:00
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2024-05-01T00:00:00
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2024 09 30 t23:59:59
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2024-09-30T23:59:59
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2024 26700:1
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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.
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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.
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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.
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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.
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Discharges from sewage treatment works have improved substantially in England since the 1980s.
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