The state flower of Kansas, a sunflower.

Second vote for sunflower. It's an annual altho' I think there are perennial cultivars available. Not all sunflowers grow 12 ft. tall. Yours could have self seeded.

Hi there,
I think the foliage looks wrong for a garden variety sunflower, aka Helianthus annuus). Goin by the small lanceolate foliage I would guess it is some perennial Helianthus (no clue, are there native annual sunflowers over there?...). That it grows at the water's edge is somewhat unusual. Is it a creek or rather pond? Sometimes Jerusalem Artichokes get washed downstream, or rather bits of their rhizomes.

Well, curious, let's see what pops up,

Bye, Lin

Maybe it's a Swamp Sunflower (Angustifolius).
They are native to Georgia. The leaves look similar and yours is by a pond.
It's pretty and probably good forage.