A lot of off trail exploration on both sides of Eagle Creek has been done & reported on this site before but I don't believe this creek has ever come previously. That doesn't mean it hasn't been done though!
It looks like Zach went up it
to the Upper Falls in 2010. (Tim and Melinda went down to that falls in 2014.) I'd imagine that going up would be quite a chore though, unless climbing wet, water-worn basalt is your idea of fun.
That said, Zach went up some serious canyons in the Gorge (like Gray's Creek), and this is what he had to say about Wauna Creek canyon:
...suffice it to say, this is a serious canyon. Nobody but experienced bushwhackers with a tolerance for risk and pain should attempt it. ...It is literally some of the toughest canyon terrain around. Slick, congested with spiked foliage, rotting wood, slick, loose rocks, you name it.
That ridge south of the falls does look interesting though. What say you, Guy? Are there some Eagle Creek ridges left for us? It's been a while!