It was too early to talk about cost, or who would pay. Houses had been shifted away from flooding in Wellington, but it had a bigger base of ratepayers to pay for the moves. He'd like to get central government help, but said it was unlikely.
"We need to understand the issue first, then how and who will pay for it."
The cost is similar to the cost of more stopbanks, a council agenda says.
Cost was a big concern of people commenting on the Chronicle's Facebook page. Some thought councils should pay, others insurance and others the owners.
One person said the area should be red zoned, and another that it could be turned into football grounds. Some thought the decision should have been made years ago.
The March consultation on flood protection allowed a new team to look at the issue with fresh eyes. The new members are Whanganui councillor Nicola Patrick and Horizons' river manager Ramon Strong.
Councillors made the decision on information presented by Mr Strong and the council's communications team, who were present at public meetings and the River Traders' market to listen to residents.
Mr Cotton laid out the reasons for not raising the Anzac Pde stopbanks. He said it would mean removing 100 trees, which would lose vista and atmosphere.
Higher stopbanks would increase the water pressure on them, and increase the risk of "piping" - water seeping under them. It can be prevented by putting concrete or metal plates into the soil underneath, but that inreases cost by 40 to 50 per cent.
Ponding from Matarawa Stream, which comes in behind the stopbanks, would continue being a problem. And there would still be a problem with floodwater backing up on incoming tides.
Higher stopbanks would obscure the view of the river, and they would be expensive.
As for moving Kowhai Park, Mr Cotton said that would be Whanganui District Council decision. Personally he would favour leaving it, but making it resilient.
Protecting SH4 would be up to the New Zeland Transport Agency.
Horizons will issue some funding to get a full understanding of the Anzac Pde problem - how many properties were affected, how badly, and which houses could be lifted or moved.
When the full extent is known people will be able to make informed submissions to Horizons' 2018-28 plan.
Making the area resilient will involve having a good warning system, lifting wiring in houses so that people can get back into them faster and putting in concrete floors that can be washed down.
He's also heard of a rubber-ised type of paint that will keep water out for several days, provided other gaps are plugged.
The idea is to lessen the impact of floods, and owners will be able to choose what to do.
"We will work with people to achieve what they want. We won't be forcing people to do anything."
Taupo Quay also floods. Mr Cotton said 200-year stopbanks there would obliterate the area used by the Saturday market, and residents didn't want that.
Businesses there could get more resilient by putting stands on rollers and being ready to vacate premises. Whanganui District Council is to have input into how it can be redeveloped.
Putiki's marae and kohanga reo flood too. Mr Cotton said Putiki people haven't made submissions, but could make them to the long term plan.
The only submisions asking for more protection have been from Whanganui District Council, while Annette Main was mayor.
"Annette Main had a very strong view. I haven't seen evidence of that in the wider community," Mr Cotton said.
WHY NO MORE STOPBANKS FOR ANZAC PDE?
+ more than 100 trees would have to go
+ increased risk of water seeping under them as they get higher
+ ponding from Matarawa Stream still a problem
+ water backing up on incoming tides still a problem
+ loss of river views
+ cost
INSTEAD, FOR ANZAC PDE
+ houses raised
+ worst affected houses moved off
+ others made resilient, eg raising wiring, concrete floors
FOR TAUPO QUAY
+ commercial and reserve area popular
+ resilience measures possible
+ redevelopment plan from Whanganui District Council
FOR PUTIKI
+ more consultation needed to find out what people want
