During the summer of 2001 I used my GPS to mark to location of the north bank of the stream. The following winter, when it was easier to walk through the woods I marked the stream bank for an even larger distance. Then finally when I started Tree and Stream Weblog. I again used the GPS to mark the bank of the stream in the vicinity of my "tree."
The graph of the right shows the bank of the stream as marked by the GPS. North is up. And for those who are comfortable reading a graph the measurements are in meters. And for those who know GPS coordinate systems the numbers are the last three digits of the UTC coordinates. The red squares are the GPS positions marked. The red lines just connect those points. The blue square is the GPS location of the tree. The tree is leaning to the North West, meaning that if it falls as it leans it will lay in the stream bed for the first 100 feet. As yet I have not gotten a precise measurement of the height of the tree. So I don't know where the top of the tree will land. The plot marks the stream bank as of August 2, 2003.
The plot below shows the GPS coordinates of a larger area. It gives a better idea of the path of the meandering stream and where on the bend in the stream the tree sits. The units on the graph are the same as those in the first graph. This graph follows the stream for a distance of about two to three tenths of a mile. The tree is near the end of the large clockwise curve near the top center of the graph. The stream flows from left to right.
The stream itself is about six to eight miles long before it reaches the area where the tree is located. It then runs a couple miles further before it empties into a major river.
My general rule is that two inches of rain within an hour is sufficient to fill the stream bed to bank full. There is a rather large flood plain along the course of the stream. Even with six inches of rain in one day the water has never gotten more than about six inches deep in the larger flood plain. In general about once every six to nine months we get a rain event that fills the stream to bank full. The risky times for this include frozen ground, a heavy rain flowing a large snowstorm, or a very heavy thunderstorm. It is these situations which cause most of the erosion of the stream bank. The frequency of these events in the future will have a major effect on how long it is before the tree falls into the stream.
As the streambank moves I will periodically update the graphs above. I am also attempting to develop a better means of measuring the actual position of the stream bank with greater accuracy to its movements can be tracked more easily.
Enought of the graphs. The photo on the right shows the tree in early August 2003. It is sitting on the "cutbank." That is the term the pros use to describe the area of the bank on the curve of the stream. Notice the roots of the tree along the bank. These are partially protecting the bank from further erosion. To the right and across the stream is the "point bar." That is the term for the area being built up on the opposite side of the stream. I am standing on the bank of the steam. The steam flows past me, around the curve and past the tree. It the goes of the right for a couple of hundred feet before making another sharp turn to the left. The tree is to the South of me. If the tree falls in the direction it is leaning it will fall in front of me, crossing the stream, then crossing the point bar before again crossing the stream a second time. The crown of the tree will land on the bank to my right.