3. Factors affecting erosion and deposition
Velocity
Gradient – rise over run
Channel shape
Channel roughness
Discharge – amount of water flow per unit time, as discharge increases, load increases.

4. Velocity

5. Velocity

6. Channel shape and roughness
Semicircular
Flow fast
Wide channel
Flow slow
Rough bottom
Flow slow

7. Channel shape and roughness
Narrow channel
Flow fast
Wide channel
Flow slow

8. Changes from Upstream to Downstream
Profile
Cross-sectional view of a stream
Viewed from the head (headwaters or source) to the mouth of a stream
Profile is a smooth curve
Gradient decreases downstream
Factors that increase downstream
Velocity
Discharge
Channel size
Factors that decrease downstream
Gradient
Channel roughness

9. Stream Erosion
Stream erosion (and deposition) controlled by flow velocity and discharge
Stream velocity controlled by stream gradient (slope), channel shape and channel roughness
Maximum velocity near center of channel
Floods involve increased velocity and discharge (volume of water passing a particular point in a stream over time)
Higher stream velocities promote erosion and transport of coarser sediments
Erosion of very small particles difficult due to molecular binding forces

10. Do Now Do ES1301-How Does Stream Flow Change over Time?
This activity can be found on my website under “Files From Class.”

14. Monday, April 29, 2013 Objective #2
You are going to learn the similarities and differences between deltas and alluvial fans

15. Deposition

16. Definition
Deposition- the process in which sediment is laid down in new locations
The end result of erosion

17. Water Deposition Alluvial fan- fan shaped deposit of sediment on land
Usually form when a stream slows down and enters a flat plain
Delta- sediment from a stream deposited where a river enters a large body of water
Triangular shape

18. Alluvial fan and Delta

19. Sediment Deposition
Delta - body of sediment deposited at the mouth of a river when flow velocity decreases
Surface marked by shifting distributary channels
Shape of a delta depends on whether its wave- dominated, tide-dominated, or stream-dominated

20. Sediment Deposition
Alluvial fan - large, fan- or cone-shaped pile of sediment that forms where stream velocity decreases as it emerges from a narrow mountain canyon onto a flat plain
Well-developed in desert regions, such as the southwestern U.S.
Larger fans show grading from large sediments nearest the mountains to finer sediments farther away

21. Do Now
Now you should access ES104 from the “Files From Class” section of my website. This investigation will focus more on deltas.