“When the big ice melted it did so rapidly. It created vast floods everywhere, sometimes for centuries.”
How do you know that? Evidence please.
That river was simply the melt water from the face of the vast ice sheet that extended from there to the North Pole.
The river channel moved across the land from East to West, and then back, many times.
That's just at the end of the last big blaciation. There's evidence that something similar happened in the previous glaciation, and the one before that, and the ones before that. Evidence of NUMEROUS glaciations may be found all over Southern Indian.
Ain't no thang!