Creek in Austin

In the first two pics it looks like people cut out the rock from the hillside. Who would have done that? I think this place was actually mined for its rock. I gotta go back and re-read the signs. The last two pics show incredible grooves in the rock but I think that's from nature. But how much of the natural erosion increased due to how much run off occurs now with roads and homes and businesses being built up in the surrounding areas? This mystery of what people were doing in this creek is fascinating. That type of curiosity drives my interest in history. I juxtapose this with the new condo tower in Austin a mile away from this nature preserve. What people do now with the land and resources only makes sense to me if I know how people used to use those resources. And how nature acts with or without us informs our decisions about what to do now.