Swimmers have been warned to stay away after sewage was discharged on beaches across England and Wales, predominantly in the south.
Pollution alerts have been issued to beachgoers by the Environment Agency, and on some beaches signs have been put up to warn people.
The environmental campaign group Surfers Against Sewage (SAS) has collected data that suggests storm sewage discharges have taken place in the waters of beaches in Cornwall, Cumbria, Devon, Essex, Lancashire, Lincolnshire, Northumberland and Sussex.
Storm overflows are designed to allow sewers to overflow into rivers and the sea when they reach their capacity from torrential rain. If the sewage is not released, it can flow into streets.
With much of the UK in drought, the land has become less able to absorb heavy rainfall, meaning larger than usual quantities reaching drainage channels, which can cause flash floods.
The Environment Agency has published pollution alerts, saying the rainfall and flooding of the past two days has affected water quality.
A spokesperson said: “Throughout the bathing season, daily pollution risk forecasts are made for a number of bathing waters where water quality may be temporarily reduced due to factors, such as heavy rainfall – as is the case today – wind or the tide.
“When the potential for a temporary reduction in water quality is forecast, we issue a pollution risk warning and advice against bathing. This enables bathers to make informed decisions regarding avoiding times or locations where the risk of pollution is higher than normal, and health risks from bathing may be higher than the annual classification suggests.”
Hugo Tagholm, head of Surfers Against Sewage, said: “Every year we track thousands of sewage spills at some of England and Wales’s best loved beaches. Water companies are routinely using our rivers and beaches as a sewage dumping ground, compromising the health of the environment and people alike.”
He said: “Official bathing waters, including Blue Flag beaches, are affected every year, with almost 3,500 sewage pollution events recorded in the 2021 bathing season alone.
“Southern Water are at the top of the dirty beach league table, with an average of 38 sewage alerts for their beaches between May and September 2021. Almost a third of our ill-health reports are also linked with beaches in their area.”
Real-time pollution alerts can be viewed on Safer Seas & Rivers Service, which gives live information for hundreds of beaches and rivers nationwide.