1. Stream/River Erosion & Deposition

2. A river is simply a LARGE stream!!
What is a Stream/River?
A stream is a moving body of water that eventually connects to an ocean
A river is simply a LARGE stream!!

3. Which river has a greater velocity?
Stream / River Characteristics
Velocity – how fast or slow the river is moving.
This determines the rivers ability to erode sediments
Which river has a greater velocity?

4. Stream / River Characteristics
2. Gradient – the slope or steepness of the river
The steeper the gradient, the more energy

5. Stream / River Characteristics
3. Discharge – the amount of water moving by a certain point of the river in a set time
The Amazon River in South America has greatest discharge 212,400 m3/s
Mississippi River in USA has 7th greatest discharge at 17,300 m3/s

6. Stream / River Characteristics
4. Stream Channel – the course that the water flows in a river

7. Following a River from Source to Mouth
A river begins at the source/headwaters
This is usually where you find the steepest gradient
You may also find V-shaped valleys here

8. Following a River from Source to Mouth
Alluvial Fan: A fan-shaped deposit of sediment that forms when a stream drops downward from a higher elevation and encounters the valley floor. The stream slows down, depositing fine silt, sand, or other sediments it is carrying.

9. Waterfall Formation The stream bed has soft and hard rock.
The softer rock erodes MORE QUICKLY as the river flows over it.
Eventually there is a big enough difference in the rock layers to form a waterfall.

11. Following a River from Source to Mouth
As the river continues, you will also find many tributaries – this is where one stream empties into another
As more tributaries add water to the main river, the amount of discharge increases

12. Tributaries

13. Following a River from Source to Mouth
As the river moves downhill, it will erode its channel until it hits base level
Base level is the lowest point to which a river can erode its channel.

14. Following a River from Source to Mouth
As a river approaches base level, it can develop meanders – bends in the stream channel

15. Following a River from Source to Mouth
Delta - a fan-shaped sediment deposit where a river empties into an ocean at the mouth

16. Lena River Delta in Siberia

17. New Orleans: Built on Mississippi River Delta

18. Meanders can turn into Oxbow lakes…here’s how

19. Ox Bow Lakes Neck of meander is gradually eroded
Once cut off, the water takes the quickest/shortest route
What’s left behind is the Ox Bow lake

20. Sediment Transport in Rivers
Rivers & Streams carry sediment in 3 ways:
In solution (dissolved load)
In suspension (suspended load)
Scooting or rolling along bottom (bed load)

21. 1. Dissolved Load
Sediments that are dissolved in river water

22. 2. Suspended Load
Fine-grained sediment (like sand, silt, clay) that remains in the water during transportation
Usually what you see that makes a river look dirty
Most sediment carried by a stream is suspended
This amount increases dramatically during floods

23. 3. Bed Load
Heavier, coarse grained sediments that travel along the bottom of a stream.
Causes the most stream erosion!
Sediment may not move frequently

24. Over 55% of U.S. rivers and streams are so polluted that they are no longer safe for fish and other aquatic life!!

25. Quiz Vocabulary Stream Velocity Gradient Discharge Stream Channel
Source/Headwaters
Alluvial Fan
Tributaries
Base Level
Meander
Delta
Ox Bow Lake
Dissolved Load
Suspended Load
Bed Load