A wastewater overflow has been detected at Mission Bay Beach in Auckland. Photo: RNZ / Marika Khabazi
Eleven Auckland beaches have been given black flag alerts as heavy rain causes overflows on the sewage system.
The beaches are mainly the inner city beaches of Coxs Bay, Herne Bay, St Marys Bay, Okahu Bay, Mission Bay, St Heliers and Point England, as well as Taipari Strand and Chapman Strand near Te Atatu.
The warning indicates a "very high risk" due to bad water quality and appear to be in place until Sunday morning.
"Wastewater overflows occur when wastewater (sewage) spills out from gully traps, manholes, engineered overflow points or pump stations. It then flows into back yards or waterways and the sea," Safeswim's website said.
Many other beaches in the region also have a red alert in place - where swimming was not advised also due to the water quality.
MetService has issued a heavy rain warning and strong wind watch for the region ahead of the Auckland Annverisary long weekend.
These are in place until Friday night.
"Heavy rain may cause streams and rivers to rise rapidly," it said on its website, adding that 50mm to 80mm of rain was expected on top of what had already fallen.