Hi Brett,
I would suggest that you post this in the Native Plants Forum. I'm sure people there will be able to help you.
There are non-natives that will grow in these conditions, but you would have to make sure that they are not in the 'weed' category like willows and poplars or it could cost you a small fortune in the future to get rid of them.Good luck,
Dee.

I'm up near the Carrara floodplain. The old dairy land contains a fair number of Erythrina which looks like crista-galli but I'm no expert and maybe its E fusca which common name of "swamp immortelle" sounds more likely. it's not an unattractive tree and quite beautiful in flower but of course thorny, and semi deciduous.
Niffsan bought the old Surfers Paradise raceway and is creating some sort of residential thing there with man-made shallow lakes and landscaping. It is of course, all flood-plain, though the soil is probably a bit sandy after their earthworks.
I would suggest you have a look up there along the Nielsens road extension and their production nursery is on Birmingham road just near Emmanuel college you might call in and have a talk to the gardeners there to see what species they are using for the areas which potentially face frequent innumdation.
IMHO some of the Melaleucas are quite lovely though.

Hi Brett,

She-oak trees for sure. Also, off the top of my head, try Liquidambars (great autumn colour too...naturally found on river flats in sth-east USA).

Definitely Australian Lilly-Pilly tree/shrub varieties and River Red Gums would go well. Beach Almond trees, Black Almond trees would also go very well.

Other ideas might include some Australian rainforest or open forest trees such as figs, tallow-wood, Flame trees, Crows Ash trees. I'm sure they could withstand occasional short-term flooding. Hope this helps. (ps. staking them or building up an earth bank around your trees might help them to withstand being washed away??)

Try some oaks or do you have them down there?