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0800 002 004 | www.nrc.govt.nz Putting Northland first

Date: 22 January, 2010

Major Progress But Floods Still Risk To Kaitaia

More than $2 million of work including more than 200,000 cubic metres of earthworks and the removal of 2000-plus trees has resulted in marked improvements to the Awanui Flood Management Scheme, local authority experts say.
However, the Northland Regional Council (NRC) says even with the extensive ratepayer-funded work carried out since mid-2005, flooding remains a serious risk to Kaitaia.

The Council concedes it may seem strange to be considering flooding when a drought has just been officially declared, but says recent computer analysis has indicated that more than 700 Kaitaia properties collectively worth over $220 million are in areas susceptible to flooding.

“Like drought, floods are by no means a new issue,” the Council’s Land/Rivers Senior Programme Manager Bruce Howse says. “Flooding, both from the Awanui River system and from Rangaunu Harbour, has been a problem since the area was first settled well over 100 years ago.”
Mr Howse says the urban areas of both Kaitaia and Awanui sit on the Awanui River floodplain, with Kaitaia’s entire Central Business District – more than half the town – located on a “very active” section of the floodplain.
He says over the past 12 months in particular, the NRC and the Awanui Flood Management Liaison Committee had made significant progress understanding the potential risks to Kaitaia from flooding caused by both the Awanui River and the Bell's Hill Slip.

Detailed computer modelling work could now predict the likely extent, depth and speed of floodwater in and around Kaitaia in various rainfall/storm scenarios. Similarly, significant risk reduction work and investigation had also been done at Bell's Hill slip, which could potentially force the Awanui River into urban Kaitaia if it failed.

“These have been the most detailed investigations and significant steps forward in recent decades for enabling an understanding of how to manage flood risk within the Awanui catchment.”

Mr Howse says in the four years to the start of the current financial year, $2.19M had been spent on flood scheme maintenance/restoration and associated scheme running costs.

As well as detailed surveying and modelling, substantial physical works had been carried out along 18 kilometres of the river, including 210,000 cubic metres of earthworks and the removal of over 2000 trees which had hindered its ability to carry floodwaters. More than 60 of the scheme’s 140 floodgated culverts had been repaired or replaced.

Mr Howse says new work has been scheduled for early this year, including further culvert maintenance and tree removal. It also hoped to improve the efficiency of the the Whangatane Spillway.

“Stopbanks will be surveyed to check their size and condition and an ecological survey of inanga (whitebait) spawning areas carried out to determine places that may be sensitive to any works. “

He says the NRC and Liaison Committee will meet next month (subs: February) to discuss options to further reduce flood risks and to set a direction for the next phase of investigative work.

“This process will require extensive investigation into the effectiveness of a suite of potential flood risk reduction options and looking at a range of criteria including technical, social, cultural, environmental and economic costs and benefits of flood risk reduction.”

However, Mr Howse says “significant” sums running to many millions will still need to be invested if the local community is serious about significantly reducing Kaitaia's future flood risks.

The Awanui is one of 27 catchments around Northland identified as priorities for flood risk planning by the NRC and local communities because of the potential threats the rivers and streams in them pose to lives, buildings, road access, infrastructure and agriculture.

Further information is available from the Council’s website via: www.nrc.govt.nz/priorityrivers

ENDS

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