I remember a few years back there was a gator spotted in a marsh/creek behind the football field at S.Oak Cliff(?).
They moved practice to another campus until TPW removed the animal.
There is a gator preserve near Parson’s Slough in SE Dallas County. Just South of 175 and 635.
I have also seen them in the Sabine near Lindale.
My guess is that it came up the Trinity from the south. I am just curious as to how it would cross the riprap on the dams.