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XII. Streams. The Hydrologic Cycle (components and pathways) Stream Velocity (controls and results) Drainage Patterns and Landscape Features (results of erosion and deposition) Stream Valley Development (tectonic uplift and downcutting) . The Hydrologic Cycle. See Fig. 12.3.

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xii streams

XII. Streams

The Hydrologic Cycle(components and pathways)

Stream Velocity (controls and results)

Drainage Patterns and Landscape Features (results of erosion and deposition)

Stream Valley Development(tectonic uplift and downcutting)

drainage basins
Drainage Basins
  • Systems of streams and their tributaries that collect runoff
    • Divide
    • Ground Water

Great Lakes

Drainage Basin

stream gradient
Stream Gradient
  • Slope of the land
  • Sinuosity of stream

10 m/km 10 m per 1¼ km =

8 m/km

10 m

10 m

1 km

1 km

meander velocity
Higher velocities on outside of meanders causes erosion (cut bank)

Lower velocities on inside of meanders causes deposition (point bar)

Fig. 10.6

Meander Velocity
channel shape and roughness
A. Narrow and Deep

Less resistance

Faster flow

B. Wide and Shallow

More resistance

Slower flow

C. Rough Streambed

More resistance

Slower flow

Channel Shape and Roughness
stream velocity controls
Stream Velocity Controls:
  • How much and what grainsize of sediment is
    • Eroded and
    • Transported
  • Where and what grainsize size will be sediment
stream erosion
Then, Erosion

Solution(chemical weathering)

Hydraulic Action (lifting)

Abrasion(crushing and grinding)

Pg. 276 .

First, Weathering

Fracturing (mechanical)

Loosening (mechanical and chemical)

Solution (chemical)

Stream Erosion
stream transport
Stream Transport
  • Dissolved Load
  • Suspended Load
  • Bed Load
    • Saltation
    • Rolling, sliding

Pg. 276

(ions)

stream deposition
e.g., Alluvial Fans

Fig. 12.14a

Fig. 12.14b

Erosion Dominated

High gradients

Less resistance

Fast velocities

Deposition Dominated

Lower gradients

More resistance

Lower velocities

Stream Deposition

Braided

Streams

Alluvial Fan

stream deposition14
Midchannel bars Fig. 12.7b

Point bars

Fig 12.9

Braided streams

Fig. 12.7a

Stream Deposition
deltas
Fig. 12.13

Reduction of velocity due to extreme widening

Deposition of silt and clay

Deltas
erosion and deposition transport
Erosion and Deposition Transport

E.g., Meandering streams

  • As meanders are migrating
    • Cutbanks eroding
    • Point bars building
  • Sediment is moving downstream
meander cutoff
Meander Cutoff

How does the gradient change with meandering and meander cutoff?

meandering streams
Meandering Streams

D

Identify

  • Cutbanks
  • Point bars
  • Meander neck
  • Oxbow lakes
  • Areas of Erosion
  • Areas of Deposition

A

C

B

E

natural levees
Natural Levees
  • Flooding
  • Overbank deposits
  • Widening of stream into flood plain
  • Deposition of sediment
    • Coarse near stream
    • Fine farther away

Fig. 12.11

graded streams
Graded Streams

Increased velocity and accelerated erosion.

Base level:

Lake or Sea

Erosion acts to grade the Longitudinal stream profile to concave-upward curve

Same Base level

drainage patterns
Drainage Patterns

A. Dendritic

Geology controls stream patterns

  • Uniformly Erodible

(e.g., flat-lying sedimentary rocks of the Midwest)

  • Conical Mountains

(e.g., Volcanoes)

  • Fractured bedrock

(shallow bedrock)

  • Resistant ridges of tilted sedimentary rocks

(e.g., Valley and Ridge Province of Pennsylvania)

B. Radial

C. Rectangular

D. Trellis