Draft coastal hazard maps released

1 Jun 2016

A three-year review designed to ensure better long-term local authority planning for up to 13,000 potentially affected properties in erosion and/or flood-prone Northland coastal areas is nearing completion.

The review began in 2013 and aims to update existing Northland Regional Council coastal hazard zones, most of which were developed at least a decade ago.

Councillor Joe Carr, who chairs the council's Environmental Management Committee, says the council has today released draft coastal hazard maps identifying land potentially at risk of flooding and/or erosion by the sea.

"There are coastal erosion hazard maps for 31 sites and coastal flood hazard maps for 61 sites; all up these cover roughly 13,000 properties up and down the length of our east and west coasts."

Councillor Carr says that the New Zealand Coastal Policy Statement requires councils to identify areas of the coastal environment potentially affected by coastal hazards over the next century. The council has chosen to do this through mapping, the bulk of which has been done on its behalf by environmental and engineering consultants Tonkin & Taylor Ltd.

"The methods they used for their assessments have in turn been peer reviewed by the University of Auckland to ensure they're in line with national and international best practice."

"Areas which may already be at risk, and those that may eventually be exposed to risk due to coastal processes like erosion and potential sea level rise, are included in the maps, but it's really important to keep this issue in perspective."

Councillor Carr says many risks have long been recognised by property owners and in many parts of Northland, formal local authority coastal erosion hazard zone (CEHZ) setback lines have already been in place for more than two decades.

"For example, in 2006 more than 630 dwellings and 1090 properties, collectively worth several hundred million dollars, were already in (or partially in) identified CEHZ.

Councillor Carr says since that time, another roughly 12,000 properties had been newly-identified as being in previously unmapped coastal flood hazard zones, due to the use of modern topographic tools like LIDAR.

He says public feedback on the combined 13,000 properties will help produce final coastal hazard maps, which he expects will be completed early next year and released shortly after.

“It’s important to remember the production of these maps does not have any effect on the actual risk of coastal hazards to a property and because the implications will vary from site to site, it’s impossible to determine whether there will be any effect on property values.”

While the new maps will increase awareness of the current and future likelihood of coastal erosion or flooding, he says councils regularly release this kind of information all over New Zealand, so it’s not a situation unique to Northland – or its insurers.

Councillor Carr says if a property is mapped as within a coastal hazard area, district councils will develop the relevant district plan rules to manage any risk in relation to buildings.  (That process will include providing a formal opportunity for the public to comment.)

The draft maps will also be available to district councils when generating land and property information reports (LIMs and PIMs).   “Where property is already within a mapped coastal hazard zone, there are already district plan rules relating to development there.”

Councillor Carr says the high-tech and complex review takes into account a wide range of data and should enable the likely impacts of erosion and resulting shoreline positions to be modelled with a fairly high level of confidence right out until the year 2115.

“The 100 year coastal erosion hazard zone has only a five percent chance of being exceeded, so we can be fairly certain that any coastal erosion will be limited to the mapped area.”

The council is writing to affected property owners and draft coastal hazard maps are now also available through the regional council website via www.nrc.govt.nz/coastalhazardmaps  “Those without access to the internet can call us on 0800 002 004 to request a copy of the maps for their area.”