Title Page Photo

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Title Page Photo
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The Impact of Fluvial Processes on the Landscape

• Fluvial processes involve running water
• Running water is Earths most important external
  agent
• Ubiquitous (everywhere except in Antarctica)

• Fig. 16-1. Gorge carved by the Green River,
  northeastern Utah.

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Streams and Stream Systems

• Streamflow and Overland Flow
• Streamflow channeled movement of water along a
  valley bottom
• Overland flow unchanneled downslope movement of
  surface water
• Valleys and Interfluves
• Valley drainage system of channeled (stream)
  flow
• Valley bottom and valley walls
• Interfluve No clearly established channeled
  flow
• High area between valleys
• Overland flow

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• Fig. 16-2. Valleys and interfluves. Valleys
  normally have clear-cut drainage systems
  interfluves do not.

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• Drainage Basins
• Valley bottoms
• Valley sides
• Interfluves that drain toward the valley
• Drainage divides
• Main stream basin
• Tributary sub-basins

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• Hierarchy of Drainage Basins
• Larger basins include a hierarchy of smaller
  tributary basins.

• Fig. 16-3

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• Stream Orders
• First-order stream
• Smallest stream, has no tributaries
• Second-order
• Begins at confluence of 1st order streams
• Third-order
• Begins at confluence of 2nd order streams
• Etc.

• Fig. 16-4

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• Fluvial Erosion and Deposition
• Animation (Stream Sediment Movement)
• Erosion by Overland Flow
• Splash erosion and sheet wash
• Rill and gully erosion

• Fig. 16-5

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• Erosion by Streamflow
• Volume of flow
• Abrasion of streambed
• Chemical weathering of channel
• Turbulence of flow
• Flow speed

• Fig. 16-6

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• Transportation
• Stream load - solids
• Types of load dissolved, suspended, bed
• Competence and capacity amount and size

• Fig. 16-7. Three types of stream load.

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• Deposition
• Alluvium
• Sorted/stratified deposits
• Smooth, rounded particles
• Cause Decrease in flow speed
• Streamflow Variability
• Floods periods of peak stream flow
• Erode upper portions of valleys
• Form vast floodplains in lower parts of valleys
• Perennial stream vs. Intermittent stream

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Stream Channels

• Channel Flow
• Friction
• Channel bottom/sides
• Turbulence
• Changing direction and speed of flow
• Causes currents

• Fig. 16-9

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• Stream Channel Patterns (4 types)
• Straight channels (uncommon)
• Short sections of a channel
• Eventually take on sinuous characteristics due to
  scouring and filling

• - Fig. 16-10

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• Sinuous Channels (common)
• Winding
• Steep gradients
• Gentle gradients

• Fig. 16-11

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• Meandering Channels
• Tightly curved loops
• Abandoned channels
• Where land is flat, such as large floodplains

• Fig. 16-12

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• Braided Channels
• Heavily loaded stream
• Gentle gradient slows flow speed
• Slow moving stream chokes channel with alluvium
• Sand and gravel bar deposits divide (braid) the
  stream

• Fig. 16-13

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• Stream Drainage Patterns
• (Reflect underlying geologic structure or
  topography)
• Dendritic Drainage Pattern
• Most common drainage pattern
• Tree-like
• Underlying structure does not control the pattern
• Nearly horizontal strata

• - Fig. 16-15

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• Trellis Drainage Pattern
• Alternating bands of tilted hard and soft rocks
• Long parallel streams cut into soft rocks
• Parallel streams are jointed by short,
  right-angled segments.

• - Fig. 16-16

Dendritic
Trellis

• West Virginia has both trellis and dendritic
  patterns.

- Fig. 16-17
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• Radial Drainage Pattern
• Streams drain from a mountain peak or volcano

• - Fig. 16-18

New Zealand
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• Centripetal Drainage Pattern
• Streams converge into a basin

Australia

• Fig. 16-19

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• Annular Drainage Pattern
• Streams converge into a basin

• - Fig. 16-20. Maverick Spring Dome WY

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The Shaping and Reshaping of Valleys

• Valley Deepening
• Downcutting and V-shaped Valleys
• Head (upper end) of a valley

• Fig. 16-21. Yellowstone River.

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• Base level
• Sea level, base level, and local base level

• - Fig. 16-22

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• Knickpoint Migration

• Fig. 16-23a-d

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• Fig. 16-B. Niagara Falls (Knickpoint) Retreat

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• Valley Widening
• Lateral erosion by a meandering stream

• Fig. 16-24

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• Fig. 16-25a-c

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• Valley Lengthening
• Headward erosion

• Fig. 16-27. Headward (gully) erosion into a
  Wisconsin field.

• Fig. 16-26

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• Stream Capture

• - Fig. 16-28

• Fig. 16-29. Stream capture by the Niger River,
  western Africa.

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• Delta Formation
• River mouth deposits

• - Fig. 16-32

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• Largest Deltas and Largest Deltaless Rivers

• - Fig. 16-30 Table 16-2 and 16-1

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• - Fig. 16-31. Locations of the worlds largest
  deltas and of the mouths of worlds largest
  deltaless rivers.

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Floodplains

• Meandering Streams
• Floods and Natural Levee Development

• Animations
• Floodplain Landforms
• Floodplain low-lying, flat alluvial valley floor

• - Fig. 16-34

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• Landforms

• - Fig. 16-37

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• Landform formation
• Cut-off meander
• Oxbow lake
• Meander scar

• Fig. 16-35

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• Natural levee

• Fig. 16-36

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Stream Rejuvenation

• Animation (Stream Rejuvenation)
• Tectonic Uplift
• Increased gradient
• Dramatic downcutting
• Landforms
• Stream Terraces

• - Fig. 16-40

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• Entrenched Meanders

• - Fig. 16-41a. Green River, Utah.

• Fig. 16-41c.
• Meander Entrenchment.

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Theories of Landform Development

• Davis Geomorphic Cycle
• (early 20th c. geographer)
• Structures, Processes, Stages
• Youth
• Maturity
• Old Age
• Rejuvenation

• Fig. 16-42

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• Criticisms of Davis Geomorphic Cycle
• No evidence of large peneplains
• Ignored erosion during initial uplift
• No clear evidence of sequential stages
• Pencks Theory of Crustal Change and Slope
  Development
• Slopes dependent on rate of tectonic uplift
• Slopes maintain their angles during uplift

• Figure 16-43

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• Equilibrium Theory
• Slope form depends on balance between uplift and
  erosion.

• The landscape (general pattern of slopes) is an
  expression of this dynamic equilibrium.

• Fig. 16-44. Swiss Alps. Erosion reduces the land
  at the same rate tectonic uplift raises the land.
  Thus, the elevation of the land remains the same.
  The general topography remains approximately the
  same also.

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Homework

• Read Ch. 16
• Mississippi River Delta
• What did you learn from the lecture/textbook
  about this delta?
• What else do you know about the Mississippi River
  delta and the city of New Orleans?
• Relate your prior knowledge to what you just
  learned.
• Due next week (or) before the final