Amelanchier?

No, the buds for next year's leaves are not right for Amelanchier.

Could be a cherry/plum (Prunus)?

Not a cherry either.

What about swamp tupleo?

Try gently scratching the twig and smelling it. Does it have a scent?

IME tupelo has bright fall color, and the twigs don't zigzag

I'll try the scratch and sniff test. This tree does have very bright red color (starting off beautifully multi-colored, then turning crimson), although that's not apparent in the photos.

The problem is the pictures aren't adequate. Show the habit of the whole bush, show closer views of the buds and leaves, if there are any old berries underneath it, or even the lingering stalks that would help...

If it's something nurseries around there sell you might find it at one of those. Or in a publicly accesible collection, like an arboretum or botanic garden.

It is a swamp tupelo.

It could as well be "black Tupelo". The leaves, at least in the second image appear a little broader than swamp tupelo.

In fact it could also be a Perssimmin. Except I'm not sure that would grow in a flood plain and it often has bigger leaves, but not always. Black Tupelo is also said to prefer higher ground.

Is the flood plain actually wet a lot? Can you tell more about the habitat and the area? Also images of the trunk might be usefull.

I just posted a very similar looking tree for identification.. At least the leaves are quite similar. I hope someone can ID it, but I'm guessing "sweetbay" has got it right... maybe you (sweetbay) can identify the tree I've posted just minutes ago at the link below. (Click the thumbnails for a larger rendering)

Here is a link that might be useful: RED LEAF TREE

hput3, yours is Vaccinium arboreum, Sparkleberry.