1. STREAMS AND THE EARTH Water Erosion

2. 2. Running Water Running water is the dominate agent of erosion
Obtain sediments by
Direct lifting of particles
Collisions between carried sediments and stream bed (Abrasion)
Receiving dissolved minerals from groundwater flow or by directly dissolving the stream bed

3. Streams Carry Sediment Three Ways
Dissolved minerals carried in solution
Solid sediments small size carried in suspension
Larger sediments carried by rolling, and bouncing along the bed

4. AFFECTS ON EARTH’S SURFACE RUNNING WATER
Streams and Erosion
Average velocity is controlled by:
1. Slope (gradient)
2. Discharge (volume)
Earth Science Reference Tables

5. Sediment Transport!

6. STRAIGHT CHANNELS

7. MEANDERING CHANNELS

8. LIFE HISTORY OF STREAMS
3 Stages of Development
Youthful
Mature
Old age

9. Youthful Stage of Stream
High Energy
High Potential
High Kinetic
Erosion Dominates
All sediment sizes moved
V-Shaped valley
Downcutting
Rapids, Waterfalls

10. Characteristics of Youthful Stream

12. Mature Stage of Stream
Decrease in kinetic energy (and lower potential)
Less erosion down-cutting and an increase in side-cutting (widening of stream channel)
Smaller particles eroded Ex.
Meandering
Development of
Floodplain
Deposition of larger
sediments

13. Reduced Gradient

14. Meandering Sacramento Valley

15. Old Age of Stream Over meandering (Oxbow lakes)
Very little Kinetic Energy
Over meandering (Oxbow lakes)
Well-developed Floodplain
Deposition Dominates

16. Mature/Old Age Stage

17. Natural/Artificial Levees

19. STAGES REVIEW

20. DAMS

21. DEPOSITION “Sedimentation”
Process by which sediments are released, settled from, or dropped from an erosional system.
Erosion and Deposition are opposite processes. When kinetic energy is high, erosion dominates. Where slope is gradual or kinetic energy minimal, deposition dominates.

22. Sediment Characteristics
Sediments become rounded and smaller with increased time spent in running water
Abrasion (Mechanical Weathering)
Dissolving (Chemical Weathering)

23. Sediment Distribution and Deposition
Larger particles deposited close to the mouth (high energy environment) and finer sediments are carried out further away from shore (lower energy environment).

24. Graded Bedding Unsorted sediment dumped into quiet body of water.
Heavy/Dense settle first
Round settle faster than disc shaped

25. Watershed The land area from which a stream gets its water
‘Divides’ separate drainage basins
Bathtub analogy

26. Continental Divide