2The streams found in mountains are likely to have formed relatively recently.
3These young streams typically have V-shaped valleys.
4The rivers tend to move fast in their upstream portions, although, some are slowed by the large rocks and boulders in the river channel.
5The young mountain streams tend to have a steep slope or gradient.
6Rivers move a great deal of material Rivers move a great deal of material. The faster the water moves, the larger material that can be carried down stream.
7Fast moving upstream portions can often move rocks and boulders. Downstream portions usually only transport small silts and clays.
8This process tends to sort materials by size. Have you ever wondered why we have so much silt and clay in our soil?
9Valleys with very steep, almost vertical sides are called canyons or gorges.
10How long do you think it took to form the Grand Canyon?
11Most scientists believe it took 1 to 3 million years!
12A stream or river can not cut its bed any lower than the body of water into which it flows. As the stream approaches this base level, the slope and speed of the stream decrease.
13The river channel becomes wider, deeper, and the volume is bigger as there are more tributaries contributing to the volume.
14The river valley also changes at this point. It becomes more open, more of a U shape with a wider river floor.
15It also has the largest volume and a very gentle gradient. The lower or downstream portion of the river is at its deepest, widest and slowest speed.It also has the largest volume and a very gentle gradient.
16The river valley tends to be broad, flat and bounded by bluffs. These bottom lands are often areas that flood.
17Lower portions of rivers often start to meander or form a s-shape river pattern.
18Erosion is greater on the outside of the bend, deposition more on the inside.
19The river can eventually cut through the meander, leaving a straighter section and an ox-bow lake.
20To view an animation of this process click on this web site.
21Rivers deposit the sediment they have carried as they slow down Rivers deposit the sediment they have carried as they slow down. This sediment load will often form deltas as the river flows into the quiet waters of a bay or gulf.
22As the deposits grow, they resemble the Greek letter ▲(delta). The river tends to be split into channels by its own deposits as it drops more sediment.As the deposits grow, they resemble the Greek letter ▲(delta).
23Alluvial Fans An alluvial fan differs from a delta in several ways. The deposit is formed on land, not in water.
24Alluvial FansAlso, the sediments of these deposits are coarse sands and gravels, rather than fine silts and clays of the deltas.
25WatershedA watershed, or drainage basin includes all of the land that drains into a river or bay either directly or through its tributaries.
26WatershedThe high land that separates one river valley or watershed from the next, is called the divide.
27Can you name the large watershed that covers over 64,000 square miles and drains the area where you live?