The Waikato District Council has released out-dated information about the likelihood of some Tamahere properties to flood at times of heavy rainfall over the objections of local representatives.
Aerial maps used in a study to show properties that may have a build-up of surface water in a one-in-100 year storm date from around four years ago (2007-2008).
Both the Tamahere district councillor Wally Hayes and the Tamahere Community Committee had urged the council to release up-to-date information, expected to be available later this year.
Houses built in the stormwater study area, the Tamahere Country Living Zone, in the last four and a half years won’t feature until new maps are produced in about six months, the council said in a media release.
“The council has published the current maps because they represent the best assessment of the potential for ponding in the area based on the available information,” said the council, which notified owners of around 920 properties by letter this week.
Tamahere district councillor Wally Hayes said he would have preferred the council to delay releasing the information until it was current. He expected the information to come as a complete surprise to many residents and to cause some frustration.
The Tamahere Community Committee said it was worried about the accuracy of the data and had serious concerns about its premature public release.
Hayes and the committee urged affected property owners to attend open days being held by the council on Tuesday, July 10 and Tuesday July 17, in the Tamahere Community Centre from 7pm to 8.30pm.
The committee said it encouraged residents “to strongly advocate to the council any inaccuracies affecting their properties.”
Hayes said many variables could be applied to the stormwater modelling “so that makes a whole lot of assumptions questionable” but he warned against over-reaction.
“In the vast majority of cases we are talking about low levels of water ponding arising from an extreme weather event every hundred years or so. Essentially this means water may lie about for a day or two.”
Tamahere Community Committee member Leo Koppens said it was disappointing the council had knowingly released inaccurate information that affected about 650 properties.
“The council should have waited until more accurate data reflecting the extensive stormwater measures undertaken by itself and developers was available,” he said.
“The released information could and, in some cases, will affect property values especially when selling and when purchasers get a LIM (Land Information Memorandum) report,” said Koppens, a local real estate agent.
In recent times the council had already addressed the one-in-100 year storm effect in resource consents granted to developers, he said.
“I urge all landowners to go to the council website and check their own properties on a specially created page. The council has offered to remove ponding data from its maps if landowners can prove their properties are not affected.”
The council said the stormwater study by engineering firm GHD combined climate and topographical data with local surveys and a computer model to predict which areas would be subject to surface water ponding in the event of a one-in-100 year level of rainfall or, put differently, a 1% chance that such rainfall would occur every year.
“This study is based on the best information currently available, however it is important to note that it is a forecast: there is no guarantee that it is exactly what will occur in a one-in-100 year storm,” said council general manager of water and facilities Richard Bax.
The council had commission new aerial maps “to obtain a more up-to-date picture of the potential for ponding in the Tamahere Country Living Zone,” he said.
The study was not expected to affect future development in the country living zone but in some cases steps might need to be taken to mitigate the potential effects of water ponding before a building or resource consent was granted.
Click for the Tamahere stormwater info on the council website.