By CLAIRE TREVETT
Homeowners on a Waiheke Island clifftop fear their property values will plunge after a report claiming many of their homes and properties face erosion over the next 50 years.
The Auckland City Council is planning to put warnings of erosion on Land Information Memorandum (Lim) reports covering about 90 properties in Huruhi Bay after an assessment of the cliff.
Residents were sent a report commissioned by the Auckland City and Auckland Regional Councils with a map showing many exclusive clifftop properties face erosion problems.
A line on the map showed the worst-case scenario of the effects of erosion over 50 years and included a 10m buffer strip to allow for major landslides and rising sea levels.
The bay is home to former broadcaster Brian Edwards and writer Judy Callingham, and former head of Time Warner Asia Pacific, Tony Wells.
At a public meeting this week, homeowners said the Lim reports could "knock six figures off the values of our homes" and questioned whether the $25,000 study by Tonkin and Taylor was comprehensive enough to warrant putting a notice on all Lim reports in the area.
Brian Edwards said their house at the end of a small point was built three years ago and the council had then said it was all right to build.
"Now there is a red line going through which shows in 50 years only our driveway will be left.
"There are uncertainties about how quickly this will happen.
"The council response is there are still investigations to be done, and there is uncertainty about how it can be fixed.
Connon Andrews, coastal scientist at Tonkin and Taylor, told the residents the cliff was weak in many parts, making it susceptible to slips.
Erosion rates averaged 5cm to 10cm each year along the whole coastline and were expected to remain similar or worsen.
The main cause of erosion was waves cutting into the base of the cliff. Stormwater and groundwater were also a problem.
He said it was a very basic report based on the limited amount of information already available, such as aerial photos, and there were some uncertainties.
The assessment had since been extended to about 30 more properties on the Putiki Bay side of the peninsula but that report was still to be finalised.
Group manager of city planning at the Auckland City Council John Duthie said the council had planned to put it on Lim reports from Tuesday, but would now hold off while the line on the map of the erosion risk zone was reviewed and its meaning clarified.
He said when the council was aware of potential problems it was legally bound to notify them. Homeowners had misunderstood the meaning of the erosion line.
"Everyone thought we were saying that land would be completely eroded away. This is not saying you can't build on these properties or in those areas.
"What it is saying is these areas have to be investigated and there are stability issues.
"In the worst case scenario of erosion, we are talking about the length of a pen every year. It's very small but now that we are aware of it, council has to act on it."
He said he did not expect there to be a sudden rush on properties being put on the market before the Lims were changed.
Any potential purchasers of any properties in the meantime would be told of the erosion study. "But when we put stuff in the Lim report we want to make sure it's accurate information.
Auckland Regional Council coastal projects leader Andrew Benson doubted the line would change.
"Yes there are some uncertainties as with any piece of work with limited information and so you have to make assumptions and extrapolations with that.
"But if the line is going to be moved there should be a very good reason for it. Just because some people have concerns about that isn't a reason to move it."
He said the Huruhi Bay study was one in a series the ARC had done with other local councils on the coastline, including Muriwai, Omaha South, Onetangi, Maraetai, Hudsons Beach and Browns Bay.
An Auckland-wide report on coastal hazards was expected by the end of the year, and more landowners could then face restrictions on their properties or Lim notes of hazards.
Mr Duthie said homeowners could contract their own engineers for individual reports, which the council would consider and decide if the Lim hazard notification should be removed again.
The report recommended improving storm water and sewage systems, restricting the amount of impermeable surfaces, restricting development near the cliff, and protecting the cliff, possibly with seawalls, and keeping the cliff well vegetated.
By CLAIRE TREVETT