The only gorge in the Pride Lands
This is not a new theory. I have seen it in a fanfiction, and – upon rewatching the worst moment in any Disney movie – I am inclined to agree with it.
The theory is such: the gorge by which Simba escapes Zira’s ambush (and, indeed, the gorge in which Zira is washed away by flood waters) is the same gorge in which Mufasa is killed.
First, we have to ask a simple question – how many gorges could there possibly be within the Pride Lands? While we aren’t told exactly how big the Pride Lands are (though “Everything the light touches” does seem to suggest that they cover a pretty wide area), the Outlands and the Elephant Graveyard aren’t that far from Pride Rock, and so we can say that the Pride Lands aren’t that big – at least, not big enough to have more than one gorge.
Second, both gorges seem to be about the same size, when you compare the stampede scene with the flooding scene.
Last, and this is the piece of evidence that finally convinced me, Simba’s escape routes in both the stampede scene and the ambush scene look similar. In the stampede scene, Simba jumps up a rocky path that stretches to the top of the gorge. In the ambush scene, he jumps up a series of logs which lead up to the top of the gorge. It could be the case that the rocks from the stampede were just covered over with logs at some point during the intervening years.
Thus, it would seem that they are indeed the same gorge.