The risk of sewage mixing with floodwater because of blocked toilet facilities has caused this year's Waimarama Beach Day to be postponed.
Thousands of people were expected to descend on the beach for the calendar highlight event on Sunday.
Beach Day co-ordinator Debbie Morgan said surface flooding by the surf life saving club had caused a blockage in its sewage tank.
"It's all backed up into the surf club's toilets and into the public toilets to the side of the club, so you can't use them."
Morgan said while the other toilet block in the area seemed to be okay, organisers believed increased use would "flood it".
Although they had tried to organise portaloos at the last minute, none were available for the event.
Instead, the event will now be held on Sunday, February 3. Morgan said vendors had been receptive to the change.
"We just don't want to overload the sewage in the state it's in at the moment. We've just got to naturally let it go away."
She said it could become a health and safety issue "only if the sewage goes back into the surface flooding and mixes it up".
A Hastings District Council spokeswoman said it was investigating this particular event to see if further work was required in the future.
She said they were not aware of a health and safety issue at the beach at this stage, but added that "any standing water should be treated with caution".
"The ponding has been caused by the heavy rain – the domain is a naturally low-lying area where rain water gathers in a number of places."
MetService Meteorologist Melissa Oosterwijk said an average of 30mm fell from midnight Wednesday to midnight Thursday in Hastings and Napier.
However, Morgan said about 120mm had been recorded on Harper Rd, Waimarama during that time.
A Hawke's Bay Regional Council spokeswoman said its Pollution Response Team had not been informed. However, it would assess the situation tomorrow morning.
A Hawke's Bay District Health Board spokeswoman said its Health Protection Team had not been advised, but was going to look into it.
Lat year, disaster was averted days before the event, when mounds of seaweed, which had washed up in front of the watch tower, were removed by several tractors operated by local farmers.
Morgan says they plan to "get some trenching done in the winter" as well as to move the sewage tank to higher ground to avoid a repeat of the situation.
For more information visit: https://www.waimaramasurf.org.nz/