The coastal area on the western Firth of Thames has been identified as one of the country’s high risk rural districts under a rising sea level scenario.
Other areas include Kaipara, parts of eastern Bay of Plenty and Blenheim.
A NIWA report last year highlighted the risk to the nation.
In Waikato under rising sea levels the tiny Hauraki Plains service town of Ngatea alone amounted to $175 million of assets sitting below mean spring tide high water lines.
In total almost $20 billion in assets nationwide are at risk.
There might be many lessons to learn from the flood and from observing what overseas engineers had done when it came to dealing with seawater inundation, Waikato Regional Council soil scientist Matthew Taylor said.
“In the Netherlands in some places they have abandoned some control systems because they were not economically viable.
“We may instead have to look at what we can grow, another way of farming there, such as using salt water tolerant grasses.”
Dealing with salt water damage to pasture might be a skill coastal farmers have to learn should more similar storms become commonplace under global warming and rising sea levels.
Taylor compiled for Rural Support Trust some of his findings from a previous Hauraki Plains sea water flood in 1995 to help affected Kaiaua farmers cope.
Typically, pasture covered by salt water for less than 48 hours with good rain after should bounce back.
“It is likely the saltwater was diluted by rain during the storm which measured up to 70mm.”
In 1995 there was also good rain and pasture recovered within three months.
Overseas experience shows between 48 and 96 hours most pasture dies but stems survive as does clover but after 96 hours all vegetation dies.
Taylor’s work indicates farms with clay soils will experience less sea water infiltration, down to about 2cm, and fortunately many soils in the district are marine clays.
He encouraged farmers to pump water off where possible and to engage with their farm advisers if concerned about the need to re-grass. They should test sodium levels on flooded pastures.
And farmers at Kaiaua and in other places will have to pay if they want improved flood protection.
Waikato Regional Council’s Waihou councillor Stu Husband said getting government funding to protect coastal strips like Kaiaua was a challenge given the bulk of infrastructure like state highways and rail lines lay further afield.
However, he was prepared to use proposal for a tourist cycle way and Miranda’s world renowned status as a bird sanctuary as leverage when discussing the funding issue with Regional Economic Development Minister Shane Jones soon.
Previous attempts to provide flood protection at Kaiaua had been thwarted by local opposition to the cost being added to rates.
Husband said opposition to a payment had typically come from home or small business owners, with farmers appreciating the value of being part of such a scheme.
Federated Farmers Hauraki-Coromandel president Kevin Robinson said it was concerning the flood had a high water mark of 2.8m, 40cm higher than the last record flood in 1996.
“It may be that it requires targeted rates to sort it out but if that is what it takes, so be it.”
Husband said the issue of rising sea levels and inundation would now also be an issue that would have to be addressed alongside conventional flood protection.
“You could consider a series of stop banks but you are trying to stop the sea and that is very hard and will be very expensive.”
