I'm not really sure what type of flower this is, but my guess is an iris. And because I found it next to a river, I will be calling it a River Iris for now.
Update: Zania send me the following on Facebook: "Correct - it is from Iris family. looks more like the Scarlet river lily [river banks] (Hesperantha coccinea). Could also be Small forest freesia [forest margins] (Freesia laxa) - can't see clearly from the pic - depends on leaves, rhizome, size etc ..."