These are not unprecedented floods, there have been worse, but if they prove to be unprecedented, when they are finally over, that only means that the former unprecedented flood has lost the title.
As our experience of Australian floods only goes back a couple of hundred years then any known unprecedented flood must be in that time frame.
Tamworth NSW has had a very successful levee system for some years and it has paid for itself when the Peel River has risen to flood levels.
There is a lot on Google regarding Tamworth and local floods.
Substantial permanent levees are the answer and once built are cheap to maintain.

A ban on new buildings would affect more than half of both NSW and Victoria and would be impractical.
Is Mise,
All that's needed to stop is the practice of building low level homes on low ground/floodplains.
Build in such places then at least have the sense to build high set or just don't build hoimes there.
As I stated in posts all along, create more & wider channels & also canal developments on flood plains, they'll take up the volume from floods or at least reduce the damage & will help keep insurance premiums down for those who never claim.
Councils approving the selling of such land must be made accountable also !

Indyvidual,
You don’t seem to appreciate how flat a lot of western NSW and Victoria are, Moree , currently flooded is almost level and many towns are on vast flats.
As an example of how flat; years ago, in my youth, I was working at Mungindi and became homesick for the sight of a hill.
I heard mention of So and So’s.Hill on the road to Pockataroo, so the next Sunday I drove out there in my not very powerful 1828 Chev 4 tourer, I drove over the hill in top gear and never noticed it.

Is Mise,
So, now that people know that the area floods, will they continue to build low level or will they start moving to higher ground or what's the general go ?
How high has the water risen there ? If everything is now flooded will people remain or will they move ? I mean, will there be employment after the flooding ?
Would most people choose to leave if they can afford it & if they can't will they rebuild until they cop it again ? Are there plans for moving people out of these areas ?
If the flooding is not deep perhaps high set buildings might be the go or building up the block etc.
Do people there actually say they want to stay despite knowing what can happen ?
Of course affordability is the greatest issue & Govt should assist people to move. The Dutch have a system where houses are literally houseboats & are ready for flooding. Perhaps similar plans could be made here ?

Indyvidual,
They’ve known that the areas flood for yonks and there is no high ground.

Levees would stop flooding and cost far less and use less material than raising a town, where there have been levees built they have been effective and there are other benefits; Tamworth has a shared concrete walking/cycling path on top of their’s.

They’ve known that the areas flood for yonks and there is no high ground.
Is Mise,
Well, isn't that a good enough reason not to build any more ? To build levees takes as much materials as it would raising a house foundation to above flood level !
Levees are just another band-aid & a target for terrorists ! A couple of sticks of gelignite & the levees become useless. It'd take too long & too much Gelignite to blow up every house on built-up foundation. You should have sufficient imagination to see the difference. leave low, flood-prone ground to water & build homes on higher ground ! If the flood levels aren't too high then build up foundations. You'll find the physical side will work better than than the theorising of the "experts" !