DS1: possible to have hidden cave behind waterfall (like DS2)?

I'm going full necro here and looking at a very old post by Ghastley back in 2009 ("I can't believe they did that") where the topic is a hidden cave, presumably the hidden cave behind a waterfall in Greilyn Forest (forget which side).

Is something like that possible in DS1/LoA? I've searched high and low, both eyeballing the SE Terrain tree and also searching SNO files for keywords. Came up with plenty of separate waterfalls, caves, small alcove behind waterfall, etc. Tried many, all are quite cool (especially the so-called Waterfall Alcove in KoE by the broken bridge to Stonebridge). But nothing for what I'm trying to accomplish. I want to be able to enter the waterfall and explore the hidden/concealed cave.

Also, totally different question: are there terrain nodes that join two downstream waterways? I mean, two streams forming into one. I've found nodes that split a waterfall into two streams (as are found in the Great Northern Forest), but not the other way around (not *up* a waterfall, obviously). In nature, it's much more common for waterways to join, rather than to split (major exception: deltas).