XII' Streams

1
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)

2
The Hydrologic Cycle
See Fig. 12.3
3
Drainage Basins

• Systems of streams and their tributaries that
  collect runoff
• Divide
• Ground Water

Great Lakes Drainage Basin
4
Steam Profiles(Streams Shaping the Land)
Flood Plain
V-Shaped Valley
5
What is this Drainage Pattern?(What does is tell
of the geology?)
6
Valley and Ridge Province of PA(Trellis Stream
Patters)
7
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
8
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

9
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

10
Stream Velocity Controls

• How much and what grainsize of sediment is
• Eroded and
• Transported
• Where and what grainsize size will be sediment

11
Stream Erosion

• First, Weathering
• Fracturing (mechanical)
• Loosening (mechanical and chemical)
• Solution (chemical)

• Then, Erosion
• Solution (chemical weathering)
• Hydraulic Action (lifting)
• Abrasion (crushing and grinding)
• Pg. 276 .

12
Stream Transport

• Dissolved Load
• Suspended Load
• Bed Load
• Saltation
• Rolling, sliding
• Pg. 276

(ions)
13
Stream Deposition

• Erosion Dominated
• High gradients
• Less resistance
• Fast velocities
• Deposition Dominated
• Lower gradients
• More resistance
• Lower velocities

• e.g., Alluvial Fans
• Fig. 12.14a
• Fig. 12.14b

Braided Streams
Alluvial Fan
14
Stream Deposition

• Midchannel bars Fig. 12.7b
• Point bars
• Fig 12.9
• Braided streams
• Fig. 12.7a

15
Deltas

• Reduction of velocity due to extreme widening
• Deposition of silt and clay

• Fig. 12.13

16
Erosion and Deposition ? Transport

• E.g., Meandering streams
• As meanders are migrating
• Cutbanks eroding
• Point bars building
• Sediment is moving downstream

17
Meander Cutoff

• How does the gradient change with meandering and
  meander cutoff?

18
Meandering Streams
D

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

A
C
B
E
19
Natural Levees

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

Fig. 12.11
20
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
21
Drainage Patterns

• 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)

A. Dendritic
B. Radial
C. Rectangular
D. Trellis