|You can look at stream valleys in two main ways. One
way is how the valleys of a stream and its tributaries look on a map.
The Bryant watershed's valleys make a tree-like pattern. Each stream
valley branches into smaller ones, and these then branch into still
smaller ones. This pattern comes from very large cracks hidden in
the bedrock lying underneath that direct the flow of water on the
Another way of looking at stream valleys is by their
shape. At their headwaters, the valleys of Bryant tributaries are
V-shaped. The streams cut right down into the soil and rock because
they are flowing steeply downward, and so they flow fast. Fast water
carries more sediment, which grinds the stream deeper and deeper
into the bottom of the V. A V-shaped valley is a younger valley,
because it is cutting back into the higher ground where it begins.
("Younger" means hundreds and thousands of years. "Older" means
hundreds of thousands, even millions of years!)
The Bryant's valley is older where it has already
cut pretty far down through the bedrock. There it flows less steeply
on its way to join the North Fork. Where it's older, it's broader,
and you find the rich, flat bottomlands good for farming. There
the stream "meanders," year by year slowly moving back and forth
across the valley, one side losing, one side gaining land. There
the land floods in high water times. That's why the bottoms are
also called "flood plains".
You may notice that it is the outside of a curve that
eats into the stream bank. The water flows fastest on the outside
of the curve. On the inside curve, the slower water drops its sediment,
and the land builds up on that bank. That's where you find gravel
bars. Then sycamores sprout. In a few years what was stream bottom
has become bottomland!