The Active River

1. The Active River Pg. 4 - 10

2. Grand Canyon • The grand canyon was formed from the Colorado river. • Over millions of years the river washed billions of tons of soil and rock from its riverbed. • This is erosion. • This is just one example of the capabilities of water.

3. Water Cycle • How do rivers keep flowing and where do rivers get their water? • The water cycle is the answer. • The water cycle is the continuous movement of water from water sources like lakes, oceans, and more.

4. River Systems • River systems are rivers and streams that all connect with the land around them. • Some rivers are bigger than others and some smaller streams will flow into larger rivers. • These are called tributaries.

5. Drainage Basins • River systems are divided into regions known as drainage basins, which is the land drained by a river system (including the main river and its tributaries) • The Mississippi River Basin includes 1/3 of the continental U.S. • Drainage basins are separated by divides, or areas of higher ground (like mountains or high hills).

6. Stream Erosion • A channel is the path that a stream follows. • As the stream flows it erodes rock and soil. • Over time streams become wider and deeper due to erosion.

7. Gradient • The measure of the change in elevation over a certain distance. • A high gradient gives a stream more energy and can erode more rock and soil. • A low gradient has less energy for erosion

8. Discharge • The amount of water a stream or river carries in a given amount of time. • Discharge increases with storms and melting of snow and ice. • Discharge will decrease with long dry periods.

9. Load • The materials carried in a stream’s water are collectively called its load. • The more energy a stream has the more load it can carry. • A high gradient and high discharge will allow for a larger load.

10. River Stages • In the early 1900’s, William Morris Davis created a model for identifying the stages of river development. • His stages were modified by scientists because not all rivers would age the same way. • They were made of different material and other factors contributed to a river’s maturing. • Climate, gradient, and load.

11. Youthful Rivers • Its channel is deeper rather than wider. • It has a steep gradient and flows quickly. • Its sides/banks are steep and straight. • It has few tributaries. • Water will flow over rocks and waterfalls.

12. Mature Rivers • Its channel is wider than it is deeper. • Its gradient is less steep and has few rapids or water falls. • It has many tributaries. • It has more discharge than a youthful river.

13. Old Rivers • It has an extremely low gradient and erosive power. • It doesn’t widen or deepen. It deposits sediment along its banks. • They have wide flat flood plains. • They have fewer tributaries because they have merged together.

14. Rejuvenated Rivers • Occur where land is raised by the Earth’s tectonic forces. • When land is raised, it makes the gradient steeper and allow for more erosion. • Step like terraces often form on both sides of a rejuvenated stream • Terraces are flat portions of the landscape at the end of a steep cliff