There's one more key player that needs to come to the table if Whanganui is to work out a managed retreat from its flood plain: the insurance industry.
I met our Whanganui representatives on the Horizons Regional Council this week. My conversation with Councillor David Cotton and Councillor Nicola Patrick was both candid and amicable.
I appreciated learning that Mr Cotton door-knocked a considerable stretch of Anzac Parade on recent weekends, talking to some 60 residents about their perspective on the flood risk, their experiences and their opinions.
He reports those who were insured had no complaints about how they were treated by their insurers -
"No, they weren't good," one resident told him. "They were fantastic."
Those who were flooded and returned to rebuilt houses have had insurance policies renewed. Those who bought flood-damaged houses have also been able to take out full insurance, without high premiums, excesses or exclusions. So far, so good.
Perhaps people buy or stay in these houses because they think a flood won't happen again. Or are they are lulled into a sense of security because ... well, insurance money will pay to rebuild?
Don't think for a second that the insurance industry won't be ruthlessly pragmatic. They are for-profit companies, acutely attuned to minimising their risk.
Will they start scaling back cover after the next flood? Or will it be the one after that? (Or it may be nothing to do with local events but a global disaster that affects New Zealand insurers' ability to get reinsurance.)
I worry that if Horizons cannot broker a timely and acceptable managed retreat from Whanganui's flood plain, the insurance industry will decide the issue for us.
Insurers are likely to stage their own managed retreat, and here's how it would likely play out, according to industry sources I've been speaking with.
The first step would probably be increased premiums and/or high excesses for specified risk, such as floods or slips. Next, they won't insure against those risks.
Then, the embargo: they won't write new policies. This is when it really starts to bite.
They'll renew your cover, but they won't write a new policy to cover the person to whom you want to sell your home.
No insurance? No mortgage.
At this point, potential buyers all but disappear.
At the same time, you would find you can't increase your level of insurance cover.
The final stage is when your insurer won't renew your policy. And if you have a mortgage on that now uninsured home?
I'm not sure what your bank's response will be, but the banking industry is well aware of the risk and already discussing options with insurers.
If you're smugly congratulating yourself on not owning property in a flood plain, consider that the above scenarios are already being experienced by New Zealanders living in earthquake-prone areas, cliff-tops at risk of erosion and coastal areas battered by storm surges.
Embargoes are already in place in parts of Christchurch, Kaikoura and the Wairarapa and in some of the most expensive neighbourhoods in Auckland.
Insurance policy schedules are horrible things to read, but there's never been a time when it's more important to know the details of your house insurance.
In the aftermath of a disaster, your outcome will depend a very great deal on the details of your insurance policy. Depending on your insurer, you may - or may not - have choices about how you are paid out.
All policies will pay to rebuild your house on the same site, but some will also pay out so you can build a house on a different piece of land (naturally, you pay for the land; that's not covered by any insurance policy). Other policies will also give you the choice of taking a payout in cash.
It falls to Horizons to broker a deal that can make managed retreat happen in time. Needed at the table are central government, our regional and district councils and the insurance industry - plus, of course, ratepayers and affected homeowners need to be consulted and involved.
As we've seen in Kaeo and now in Edgecumbe, central government can find money to support uninsured people in the wake of disastrous flooding. Does it have the sense, and the will, to find money to prevent harm before it happens?
That's it from me - for now - on this vexatious topic. I really want to hear from our would-be local MPs. What would they, and their parties, do to support a managed retreat from natural disasters in Whanganui?
Rachel Rose is a writer, gardener, fermenter and fomenter - more reading and sources are online at www.facebook.com/rachelrose.writer