I was familiar with the general landscape in this area before I went out exploring this morning, but I didn't know that a large stream parallels one of the trails. I became aware of the stream when I paused for a minute to attend to what sounded like a stampede of horses heading my way. It turned out that what I was hearing was torrents of rushing water. The stream was separated from the trail by up to 50 feet of brush and hidden from view by a 4 foot tall pile of rocks that paralleled the entire length of the stream. If the stream was dried up when I explored these trails a few years ago I could see how I wouldn't have noticed it. I only became aware of the stream today by sound.
 
The wall of rocks paralleling the stream was certainly the work of man. Like so many other trail networks I visit this one passes through land that was once cleared for agricultural use. This wall of rocks would have marked the edge of a field.