1. Stream and River Deposits
Chapter 11 Section 2

2. The Ability to Erode
Gradient: Measure of change in elevation over a certain distance
Discharge: The amount of water a stream or river carries
Load: The material carried by a stream

3. Gradient
The steeper a stream is the more erosive energy it has

4. Discharge
The more water a river will discharge the more erosive power it will have.

5. Load Load is affected by speed. Fast = large particles
Slow = Smaller particles

6. Stages of a River Rivers go through a “life cycle.” Youthful Mature
Old

7. Youthful
Youthful rivers have a steep gradient, a steep and narrow channel, and many waterfalls. The channel will erode deeper, rather than wider.

8. Mature
Mature Rivers have a gradient that is not as steep as a youthful river. They have few falls and rapids. They will erode wider rather than deeper.

9. Old
Old rivers have a low gradient and little erosive energy. They deposit rather than erode.

10. Rejuvenated Rivers
Rejuvenated rivers are mature rivers that have a steeper gradient due to land rising because of tectonic activity.

11. Deposition

12. Delta Rivers slow down when they empty into a large body of water.
This often causes a fan-shaped pattern of deposits called a delta.

13. Deltas (cont.) These deltas cause the coast line to grow.
Deltas are made of mostly mud. Some of the mud particles come from very far away.

15. Alluvial Fans
When a fast-moving mountain stream flows onto a flat plain, the stream slows very quickly.
The deposition forms an alluvial fan.
Alluvial fans form on dry land.

18. How do rivers deposit sediment?
Rivers pick up weathered sediment during erosion.
Then the sediment is dropped off or laid down.
This happens when the speed of water decreases.

19. Meandering Rivers Constantly erode material - Cut bank
Constantly deposit material - Point bar
Change their channel course gradually
Create floodplains wider than the channel
Very Fertile soil
Subjected to seasonal flooding

20. Formation of Meanders

21. Point bar deposits

22. Cut bank erosion
Point bar deposits }
Meander loop

23. Formation of an Oxbow

24. Meandering stream
flowing from
top of screen
to bottom

25. Maximum
deposition
Maximum
erosion

35. Meander scars
Oxbow Lake
Oxbow
cuttoff

41. Flood Plains
When there is a sudden increase in the volume of water flowing into a stream, it will overflow.
This is caused by a SUDDEN increase in precipitation or rapid snow melt.
The area around a river that forms from sediments deposited during a flood is called a floodplain.
Each flood adds another layer of sediment.

43. Good Farming
Floodplains are good for farming because the periodic floods bring in new, rich soil.

44. Review What is the difference between a delta and an alluvial fan?
Why are floodplains bad?
Why are flood plains good?
What causes sediment to be deposited.
What is the relationship between weathering, erosion, and deposition?