Seaside houses falsely tagged as flood risks

Thousands of coastal homes north of Auckland may have been wrongly tagged with a hazard warning because of an exaggerated threat from global warming and extreme weather.

The mistake was discovered after a group of Omaha Beach homeowners challenged the warnings slapped on their Land Information Memorandum (LIM) by Rodney District Council.

Like other councils around the country, including Tauranga and Auckland's North Shore, Rodney is trying to protect itself from potential multimillion-dollar legal action by residents hit by severe flooding.

Orewa, Manly, Whangateau Harbour, Pt Wells and Omaha have all been affected by the LIM reports warning potential buyers the property is at risk of "coastal inundation".

A LIM is usually the first thing a potential buyer asks for because it lists any defects a home may have.

Engineer Ian Hutchinson was hired by Omaha Beach residents to check the council's calculations.

"Omaha has some wealthy and influential people and they got organised," he said. "It's like a cancer on a property when you say something like that on an LIM, but once councils have this sort of information on their files, they are legally obliged to publish it so they put something on the LIM to cover their butt."

The problems began when Rodney District Council commissioned a Tonkin and Taylor report on "coastal inundation" along its eastern coast, which has experienced a population explosion and skyrocketing land values in recent years.

The council used the report to calculate how far above mean sea level - the mid-point between low and high tide - the floor of a dwelling must be to avoid the combined risk of sea-level rise from climate change, one-in-50-year storm surges, weather patterns such as El Nino and La Nina and higher-than-normal tides.

At Omaha the figure was 5m, affecting 242 homes.

But Mr Hutchinson said sea-level data the council used were flawed and the idea rising sea levels would combine with an extreme weather event, a nasty weather pattern with a super-spring tide, was ridiculous.

"All this global warming sea-level rise is a load of garbage, sea levels have been fluctuating for ever."

The limit at Omaha should have been 3.8m, meaning only a handful, if any, properties would be affected.

Omaha real estate agent Michael Dow said the affected homes immediately lost up to a third of their value.

"The council drew a blue line showing homes all tarred with the same 'inundation' brush, it's just rubbish."

Omaha residents' association president Greg Stenbeck said lawyers helped with the case and he hoped the offending LIM notices would be removed by next month.

"There was nothing wrong with the report, it was that the council applied it willy-nilly," he said.

The council has also agreed to reword all LIM notices when one is asked for by the owner or a potential buyer.

Instead of saying the property was identified "as being within or near to land which may be subject to sea inundation", it will say the Tonkin and Taylor report did not mean the property was directly affected by the risk of inundation but was "within a range of site levels that could be affected".

The council was in the middle of revising risk levels to below 4m at Omaha and Manly but Pt Wells, Omaha Flats and Whangateau Harbour residents would have to wait for a major aerial topographical survey before LIM hazard warnings could be removed, said Rodney District spokesman Mike Isle.

That was because the data for those areas were even more limited than for Omaha Beach.

Local Government New Zealand environment manager Susan Edwards said it was standard practice at a number of councils to include information about coastal hazards on LIM reports or in district plans.

Thames-Coromandel District Council spokesman Peter Hazael said his council and Environment Waikato had taken that obligation seriously for buildings in fore-dune areas such as Cooks Beach, around Whitianga and at newly developed parts of Matarangi.

Areas within 100m from the beach were marked on LIMs as coastal hazard areas.