1. A stream is a body of water that carries rock particles and dissolved ions and flows down slope along a clearly defined path, called a channel. Thus, streams may vary in width from a few centimeters to several kilometers.
Streams

2. Streams carry most of the water that goes from the land to the sea, and thus are an important part of the water cycle.
Streams carry billions of tons of sediment to lower elevations, and thus are one of the main transporting mediums in the production of sedimentary rocks.
Streams carry dissolved ions (minerals), the products of chemical weathering, into the oceans and thus make the sea salty.
Streams are a major part of the erosional process, working in conjunction with weathering and mass wasting.
Streams are the most influential factor in sculpting the physical earth.

3. The Water Cycle

5. The Basics
Stream Flow
Water makes its way to the sea under the influence of gravity.
The time it takes depends on the stream’s velocity.
Velocity is determined by three things
Gradient
Shape
Discharge

6. Gradient The slope of a stream channel
Gradient is the vertical drop of a stream over a specified distance in miles.
Some portions of the Mississippi have a gradient of 10 cm per km.

7. Shape of a Stream’s Channel
The shape and roughness of a channel affects the amount of friction the water will encounter.
Smooth channels offer little friction and fast water.
Rough channels offer high friction and slower water.

8. Discharge
A stream’s discharge is the volume of water flowing past a point in a specified time.
Measured in cubic meters per second.
The Amazon discharges 207,600 m3 of water per second, 12 times more than the Mississippi.

9. Changes from Upstream to Downstream
Gradient is steep upstream (start in hills or mountains)
Velocity and discharge is great downstream (smooth stream bed and high pressure from upstream water)

10. Straight Channels Rare Low Velocity
Bars = piles of sediment. Water works its way around the bars. Velocity and erosion are greatest at banks (sides of channel)

11. Meandering Channels Latin word for WANDERING
Velocity is highest at outer parts of meander (cutbank)
Erosion happens at cutbank
Velocity is lowest at inner parts of meander (point bar)
Depositioin happens at point bar
This continual erosion and deposition causes the channel to move and bend across a river valley.
Creates a flood plane, or area that a river floods.
Meandering Channels

13. Braided Channels
Streams with highly variable discharge and easily eroded banks.
Bars get exposed during low discharge and produce a braided channel
Usually happens at deltas.

14. Deltas Stream enters standing body of water.
Velocity drops and sediment is deposited.
They build outward from coastline.
Can only survive in low current and velocity.

15. Work of Streams Erosion – the general removal of rock and soil.
Streams transport their load of sediment in 3 ways
In solution (dissolved load)
In suspension (suspended load)
Rolling along the bottom (bed load)

16. Dissolved Load
Most of a stream’s dissolved load is brought by ground water.
Expressed as parts of dissolved mineral per million.
The average for the world’s rivers is between 115 – 120 ppm.

17. Suspended Load
Visible suspended sediment carried by a stream (sand, silt, and clay).
Usually constitutes a streams largest load.

18. Bed Load Sediment too large to be carried in suspension.
These large particles move along the bottom of the stream.
Some roll
Some hop (saltation)
Grinding action of the bed load, abrasion, aids in erosion.

19. Competence vs. Capacity
A stream’s competence is a measurement of the maximum sized particle a stream can carry.
The faster a stream’s velocity, the larger its competence.
A stream’s capacity is the maximum load it can carry.
The capacity is related to its discharge.
The greater volume in a stream, the greater capacity it will have.

20. Deposition
As a stream slows down, its capacity and competence decrease.
Particles begin to settle depending on their size.
Particles of similar size are deposited together (sorting).

21. The Stream Cycle
Over time rivers shape and reshape the land. Just like karst topography, there are stages of river development. They are:
Youth
Maturity
Old Age
Rejuvenation

22. Youth V-Shaped Valley Rapids
Waterfalls
No Flood Plain
Somewhat straight channel
Steep gradient
Valley Being Deepened
Drainage is poor therefore swamps and lakes MAY form but not always

23. Yellowstone River

25. Maturity V-Shaped Valley Beginnings of Flood Plain Increased Meanders
Gradient begins to reduce
Valleys stop deepening
Divides become rounded

26. Old Age Land worn to nearly flat surface
No downward cutting taking place
Very low gradient
Rivers meander across extremely wide, flat flood plains
Natural levees may form
Oxbow lakes form

27. Oxbow Lakes

31. Rejuvenation
Uplift of Land (Lowering of Sea Level, sometimes greater stream flow) causes stream to speed up and cut deeper.
Stream valley takes on youthful characteristics but retains features of older stages as well.
Can happen at any point in the cycle.

32.                                                                                     
Rejuvenation of an old-age landscape.

33.                                                                                     
Rejuvenation of an early mature landscape.