wyldvigilante
After watching this I had to research caves in that area talked about in the movie northwest of the Alamo and came up with a cave network in Travis county. I read a cave survey that was done in the area that was old and hard to read being done in the old style copy that used purple ink. One in particular caught my eye.

It was faded and difficult to read parts of it illegible called Etts Cave or West Cave and talked about how it was once commercially used but did not state how. It had a waterfall within it and damns were built to block passage into rooms but allowed just enough room for only water to pass. This cave network also had numerous sink holes like seen in the movie.