Fluidr / MMR Dad's favorites

I composed this image recently while walking beside a stretch of the Bow River in Alberta, Canada. Hardly a creative masterpiece; I just found the view to be beautiful. Later, I began to think about the meandering of rivers, and why they do. This is what I learned.

When a river flows through the mountains, it primarily chooses the path of least resistance and weaves and is directed by the shape of the terrain. This makes sense as most rock takes a long time to erode so the water is a bit more at the mercy of the topography.

So, why do rivers meander so much on flat terrain? You would think they would flow in a relatively straight path cutting through the landscape. And yet, you could argue they weave and meander more across a level landscape!

Water may begin flowing in a relatively straight line downhill, but even small obstructions along the bank will alter the path. It could be a stone, a fallen tree, or even just a weak point in the bank but all of these things will change the flow of the water.
For example, if the water encounters a boulder that is jutting into the river on one side it will be forced toward the opposite bank.

Once this occurs, the river will now begin to more rapidly erode that bank and begin to form a curve. Once this happens, momentum will start to build through the curve and it will slingshot back toward the opposite bank. Not surprisingly, this side of the bank will become eroded and the process will begin again.

You may be wondering…is there a pattern? The answer is yes because on average the length of an S curve tends to be about six times the width of the channel. Like many things in nature, there is a fractal pattern built into the way rivers meander.

A fractal is a never ending pattern that repeats itself at different scales. This property is called “Self-Similarity.” Fractals are very complex, but they are made by repeating a simple process. Natural fractals include branching patterns like trees, river networks, lightning bolts, blood vessels and spiral patterns like seashells, hurricanes and galaxies. And then there are mathematical fractals - but I’m not going there.

Interesting. But I've decided that the beauty of a flower or a bird or a tree or a river is not enhanced by knowing its name, or whether it is a fractal or not. Better to just take a deep breath and enjoy it.

Tags: Alberta Canada Rivers Nature Beauty Fractals Water