Your SlideShare is downloading. ×
GEOG 100--Lecture 16--Streams
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

GEOG 100--Lecture 16--Streams

405

Published on

Published in: Education
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
405
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
0
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • \n
  • Transcript

    • 1. Chapter 11Fluvial Geomorphology
    • 2. StreamsThe work that streams do:• Erosion/Denudation – Movement away of rock, rock fragments and/or soil from its original position• Transportation – Continuous movement of material from one place to another• Deposition – Setting down (depositing) of eroded and transported material
    • 3. Drainage Systems• Drainage system—A branched, hierarchical network of streams and tributaries• Valley—Where a drainage system is clearly established• Interfluve—(“inter”=between, “fluvia”= rivers) High ground that separates valleys• Drainage divide—The invisible line separating two drainage basins
    • 4. Drainage basinor Watershed• A single network system; includes both the channeled valley and any other land surface contributing overland flow or groundwater to the stream• Scale varies
    • 5. Erosion• Overland flow— unchannelized flow of water• Splash erosion—Raindrops hitting exposed ground surface, shifting individual particles, which can then be transported away
    • 6. Overland Flow• Sheet erosion—if there is very little ground cover (vegetation), not much water may infiltrate and sheet flow can occur, moving particles downslope
    • 7. Erosion• Hydraulic action—The physical force of water pounding on rocks and land materials, breaking them apart• Abrasion—Rock materials hitting the bed (bottom) of the river and its banks (sides)• Corrosion—The chemical action of water dissolving minerals and rock material
    • 8. How Quickly Erosion OccursDepends On…• Flow Speed• Turbulence• Resistance of the bedrock
    • 9. 1. Flow Speed
    • 10. 1. Flow Speed• Flow Speed –The faster the water, the more force it has –Faster water = more erosion
    • 11. What makes the water go faster?
    • 12. What makes the water go faster?1. Steeper gradient
    • 13. What makes the water go faster?1. Steeper gradient – Gradient—The rate of fall in elevation of the stream surface in the downstream direction (as in 20 ft./mi.)
    • 14. What makes the water go faster?1. Steeper gradient – Gradient—The rate of fall in elevation of the stream surface in the downstream direction (as in 20 ft./mi.) • Steeper gradient = faster flow = more erosion
    • 15. What makes the water go faster?1. Steeper gradient – Gradient—The rate of fall in elevation of the stream surface in the downstream direction (as in 20 ft./mi.) • Steeper gradient = faster flow = more erosion2. Volume of flow (discharge)
    • 16. What makes the water go faster?1. Steeper gradient – Gradient—The rate of fall in elevation of the stream surface in the downstream direction (as in 20 ft./mi.) • Steeper gradient = faster flow = more erosion2. Volume of flow (discharge) – More water = higher speed = more erosion
    • 17. What makes the water go faster?1. Steeper gradient – Gradient—The rate of fall in elevation of the stream surface in the downstream direction (as in 20 ft./mi.) • Steeper gradient = faster flow = more erosion2. Volume of flow (discharge) – More water = higher speed = more erosion • Flood events move bigger material—and more of it!
    • 18. What makes the water go faster?1. Steeper gradient – Gradient—The rate of fall in elevation of the stream surface in the downstream direction (as in 20 ft./mi.) • Steeper gradient = faster flow = more erosion2. Volume of flow (discharge) – More water = higher speed = more erosion • Flood events move bigger material—and more of it!3. Channel width—the narrower the channel, the swifter the flow, for the same volume of water (Remember the Venturi effect?)
    • 19. How much erosive force?
    • 20. How much erosive force?
    • 21. How much erosive force?
    • 22. How much erosive force?
    • 23. 2. Turbulence
    • 24. 2. Turbulence• Water swirling and tossing, not smooth flow
    • 25. 2. Turbulence• Water swirling and tossing, not smooth flow• Turbulence is determined by: –Flow speed
    • 26. 2. Turbulence• Water swirling and tossing, not smooth flow• Turbulence is determined by: –Flow speed •Faster flow = increased turbulence
    • 27. 2. Turbulence• Water swirling and tossing, not smooth flow• Turbulence is determined by: –Flow speed •Faster flow = increased turbulence –Roughness of the stream channel
    • 28. 2. Turbulence• Water swirling and tossing, not smooth flow• Turbulence is determined by: –Flow speed •Faster flow = increased turbulence –Roughness of the stream channel •A rough, irregular channel = more turbulence
    • 29. 2. Turbulence• Water swirling and tossing, not smooth flow• Turbulence is determined by: –Flow speed •Faster flow = increased turbulence –Roughness of the stream channel •A rough, irregular channel = more turbulence
    • 30. 3. Resistance of bedrock• More resistance (harder rocks) = less erosion
    • 31. Transportation: Stream Load• Stream load (rock material transported by streams) is carried in three forms:
    • 32. Transportation: Stream Load• Stream load (rock material transported by streams) is carried in three forms:
    • 33. Transportation: Stream Load• Stream load (rock material transported by streams) is carried in three forms: 1. Dissolved load—dissolved minerals carried in solution
    • 34. Transportation: Stream Load• Stream load (rock material transported by streams) is carried in three forms: 1. Dissolved load—dissolved minerals carried in solution 2. Suspended load—small particles that never touch the stream bed
    • 35. Transportation: Stream Load• Stream load (rock material transported by streams) is carried in three forms: 1. Dissolved load—dissolved minerals carried in solution 2. Suspended load—small particles that never touch the stream bed 3. Bedload—larger rock fragments that drag, roll, skip or bounce along the stream bed
    • 36. Transportation: Stream Load• Stream load (rock material transported by streams) is carried in three forms: 1. Dissolved load—dissolved minerals carried in solution 2. Suspended load—small particles that never touch the stream bed 3. Bedload—larger rock fragments that drag, roll, skip or bounce along the stream bed • Material is picked up, dropped and picked up again
    • 37. Transportation: Stream Load• Stream load (rock material transported by streams) is carried in three forms: 1. Dissolved load—dissolved minerals carried in solution 2. Suspended load—small particles that never touch the stream bed 3. Bedload—larger rock fragments that drag, roll, skip or bounce along the stream bed • Material is picked up, dropped and picked up again
    • 38. Transportation: Stream Load• Stream load (rock material transported by streams) is carried in three forms: 1. Dissolved load—dissolved minerals carried in solution 2. Suspended load—small particles that never touch the stream bed 3. Bedload—larger rock fragments that drag, roll, skip or bounce along the stream bed • Material is picked up, dropped and picked up again
    • 39. Transportation: Competence
    • 40. Transportation: Competence• The faster the stream is flowing, the larger the particles it can transport
    • 41. Transportation: Competence• The faster the stream is flowing, the larger the particles it can transport• This measurement is called competence
    • 42. Transportation: Competence• The faster the stream is flowing, the larger the particles it can transport• This measurement is called competence – Competence varies to the sixth power of the water’s speed
    • 43. Transportation: Competence• The faster the stream is flowing, the larger the particles it can transport• This measurement is called competence – Competence varies to the sixth power of the water’s speed If flow speed doubles:
    • 44. Transportation: Competence• The faster the stream is flowing, the larger the particles it can transport• This measurement is called competence – Competence varies to the sixth power of the water’s speed If flow speed doubles: 26 = 64 times the size!
    • 45. Transportation: Competence• The faster the stream is flowing, the larger the particles it can transport• This measurement is called competence – Competence varies to the sixth power of the water’s speed If flow speed doubles: 26 = 64 times the size! – This is why flood events are so significant in stream transportation
    • 46. Transportation: Capacity
    • 47. Transportation: Capacity• Capacity—A measure of the amount of solid material potentially transported (volume/time past a given point: gal/sec)• The capacity of a given stream depends on:
    • 48. Transportation: Capacity• Capacity—A measure of the amount of solid material potentially transported (volume/time past a given point: gal/sec)• The capacity of a given stream depends on: 1. Water volume (volume↑, capacity↑)
    • 49. Transportation: Capacity• Capacity—A measure of the amount of solid material potentially transported (volume/time past a given point: gal/sec)• The capacity of a given stream depends on: 1. Water volume (volume↑, capacity↑) 2. Flow speed (flow speed↑, capacity↑)
    • 50. Transportation: Capacity• Capacity—A measure of the amount of solid material potentially transported (volume/time past a given point: gal/sec)• The capacity of a given stream depends on: 1. Water volume (volume↑, capacity↑) 2. Flow speed (flow speed↑, capacity↑) 3. The type of load material
    • 51. Transportation: Capacity• Capacity—A measure of the amount of solid material potentially transported (volume/time past a given point: gal/sec)• The capacity of a given stream depends on: 1. Water volume (volume↑, capacity↑) 2. Flow speed (flow speed↑, capacity↑) 3. The type of load material (lighter material, capacity↑)
    • 52. Deposition• Deposition occurs when either flow speed or volume decrease• Conditions that cause deposition: –Change in gradient –Channel widening –Change of direction –Flowing into less active water
    • 53. Deposition: Alluvium• Alluvium—Any stream-deposited debris –Sorting—Based on size (smaller particles carried farther than large ones; as stream flow decreases, larger particles will drop out of suspension first)
    • 54. Sorting after a flood event erosion
    • 55. Sorting after a flood event
    • 56. Sorting after a flood event deposition
    • 57. Sorting after a flood event deposition (particles settle biggest first, smallest last)
    • 58. Deposition: Alluvium• Alluvium –Particle shape—Alluvial material is generally smooth and round due to rocks hitting each other and the stream bed; the longer it’s transported in the stream, the more rounded and smooth a rock will become
    • 59. (some well-rounded alluvial deposits)
    • 60. Stream Flow• How does friction from the channel sides and bottom affect stream flow?
    • 61. Stream Flow• Patterns – Straight – Sinuous – Meandering – Braided
    • 62. Stream Flow• Patterns – Straight – Sinuous – Meandering – Braided
    • 63. Stream Flow• Patterns – Straight – Sinuous – Meandering – Braided
    • 64. Stream Flow• Patterns – Straight – Sinuous – Meandering – Braided
    • 65. Just like a lake, water balance mustbe maintained, or the stream willbecome an ephemeral stream
    • 66. Equilibrium: A Graded Stream• All factors are balanced (gravity, stream load, deposition, down-cutting)• A graded condition is more theoretical than actual, because equilibrium is so difficult to achieve—and maintain
    • 67. Which processes happen as a streamtries to attain a graded condition?• Valley deepening• Valley widening and flattening• Valley lengthening
    • 68. Valley Deepening:Knickpoint Migration• Downcutting progresses upstream, until the valley is all at one level
    • 69. Valley Deepening:Knickpoint Migration• The Case of Niagara Falls
    • 70. Valley Widening and Flattening
    • 71. Valley Widening and Flattening The Role of Meanders
    • 72. Meanders and Oxbow Lakes
    • 73. Meanders and Oxbow Lakes
    • 74. Can you find the oxbow lake?Where is a cutoff about to form?
    • 75. 34
    • 76. Structures of a Floodplain
    • 77. Structures of a Floodplain
    • 78. Valley Lengthening:Headward Erosion
    • 79. Valley Lengthening:Delta Formation and Distributaries
    • 80. Valley Lengthening:Delta Formation and Distributaries
    • 81. Valley Lengthening:Delta Formation and Distributaries
    • 82. Valley Lengthening:Delta Formation and Distributaries
    • 83. Stream Rejuvinationand Entrenched Meanders
    • 84. Stream Rejuvinationand Entrenched Meanders
    • 85. Stream Rejuvinationand Entrenched Meanders
    • 86. Next: Oceans

    ×