Horizons Regional Council's unexpected announcement that it would pursue a strategy of managed retreat from the eastern flood plain guarantees years of uncertainty and stress for Anzac Parade homeowners.

It's a bold move, given there's no precedent in New Zealand for spending government money before a natural disaster happens.

There is talk of houses being shifted away from flooding in Wellington. Some 75 houses on Pharazyn and Marsden Sts in Lower Hutt will be bought - and demolished - by the Hutt City Council in order to build bigger stopbanks to protect its CBD, but work hasn't begun yet.

Stopbank proponent Steve Baron has repeatedly compared Whanganui's defences to those in Palmerston North, which are built to withstand much bigger floods than our 1-in-50 year stopbanks.

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It plays into popular local discontent with Horizons - you know the mutterings about how all "our" money gets spent in Palmerston North, the "what-do-they-do-for-us?" complaints.

It's easier to understand why Palmerston North residents have stronger flood defences (and why they supported allocating rates to pay for it) when you dig into the numbers.

Over there, between $25 million and $35m spent on constructing flood defences protects a commercial and residential area with a capital value of at least one billion dollars and as many as 5300 residences.

Improving stopbanks along Anzac Parade would protect 98 homes, together worth $21m, and would cost an estimated $7m to $10m. Work out the average cost per house for yourself - it's startling.

Horizons is not taking the easy way out by pursuing managed retreat. The easy way out is do nothing.

That's not an option given the regional council's obligation to increase community resilience to natural hazards.

I respect Horizons' position, and particularly its senior technical staff, who show evidence of having listened well and thought hard.

Did you slip your token into the red bin, voting to "keep flood protection at its current level", thinking that would keep rates down?

Our community needs to understand that managed retreat will cost significant amounts of money - including for the councils.

Horizons isn't going to invest in detailed research into stopbank design, so we won't know how the cost of managed retreat will compare to raising stopbanks.

It's unlikely to be much cheaper, but it will be more effective and long-lasting. Some people, like former mayor Annette Main, have suggested some improvement in flood protection is made as a short- to medium-term measure, while the longer goal of managed retreat is figured out.

That's going to take decades to resolve, she thinks.

Regional councillor Nicola Patrick's view is Horizons can't justify spending money on both strategies and Whanganui must start now to solve the challenges of a managed retreat.

Those challenges are considerable. Who will share the financial pain? We've only seen the very beginning of discussion but some comments made online are bitter and divisive, along the lines of, 'I've got my own problems and bills to pay, why should I bail out people who bought homes on Anzac Parade?' It's an attitude being expressed even in the council chambers.

There are also difficult issues about keeping the state highway open and all the underground utilities that run below the Parade - electricity, gas, water, stormwater and sewage and now UFB cables.

(Consider for a moment the devastating economic implications of State Highway 4 being rerouted away from Whanganui. Given the New Zealand Transport Agency's incapacity to repair the relatively minor flood damage suffered two years ago, we may be faced with this scenario sooner rather than later.)

And still ... still people buy these homes. The issue of personal responsibility can't be ignored.

Are the buyers out-of-towners, blissfully ignorant of our trials? No - I spoke with a leading agent who is still selling Anzac Parade homes. The regulatory requirements are stringent, and agents clearly disclose the flood risk.

"We point out to them where on the wall the floodwaters came to," he told me.
Yes, some of the buyers are from out of town - but they ask more questions about flooding than the locals. It all seems to be to be a dangerous gamble.

For now, Anzac Parade homeowners can still get out, even if prices have showed signs of softening since Horizons' announcement. But there is going to come a tipping point where the buyers will disappear. And that may well happen years before any agreement about how to share the cost of lifting or moving houses out of danger.

There's no question that managed retreat is going to cost individual homeowners. It's just a question of how much they stand to lose.

Rachel Rose writes in a home office overlooking Anzac Parade