Topic: Erosion & Running Water
* Earth’s main agent of natural erosion
What is erosion?
• Erosion is -
Agents of Erosion
• Agents of erosion include -• Running water is the big Kahuna of all
erosional agents.
How does water carry the sediments?
• Water carries sediments in the following ways:
–Solution – –Suspension – –Rolling or bouncing along the streambed.
–Floating – -
Streams act as conveyor belts
Cobbles & Pebbles
Move by sliding, rolling
along the river floor
Slower than the water flow
Colloids (Silt & Clay) & Dissolved Ions
Carried in suspension
Same speed as water
Sand
Bounces along river floor
Slower than the water flow
Stream Side View
Greatest Potential Energy
= Stored Energy
Greatest Kinetic Energy =
Energy of Motion
Lake
Most Erosion
Low Kinetic &
Potential Energy
Most
Deposition
Ocean
Dynamic Equilibrium
Rate of Erosion = -
Changing Stream Velocity:
• A. -• B. --
Stream velocity determines size of
sediment carried.
ESRT pg 6 
Take out your ESRT!
Streambed
--
Stream bank
Stream bank
--
Region of maximum stream velocity
changes when streams bend or turn.
Region of
maximum velocity
shifts to --
Region of minimum
velocity shifts to --
Since the region of maximum stream velocity is at
the outside of the curves, streambeds are more
eroded at the outside of curves.
A’
A
B’
B
C
C’
bed
A
C
C’
B
A’
B’
What does erosion by rivers create?
• Abraded sediments
– --
FQ
The stream’s velocity is 100 cm/sec, what size
sediment(s) can the stream transport?
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Topic: Life Cycle of a Stream
Youthful Stream
Lake
(Source of
Water)
Waterfall
Steep
Slope
Rapids
Rapid
Flow
This forms V-shaped valleys.
** ---**
Middle Age
Velocity decreases
due to decrease in slope
Begins to meander
Downcutting slows
due to velocity
decrease
Valley walls become
wider
Old Age Stream
Slow speed
Very broad, flat valley (flood plain) filled with fine
sediments - alluvium
Almost flat slope
Very little erosion
Oxbow lake
Wide meanders
Wide flood plain
Meander – --
Oxbow lake – --
Rejuvenation – a
stream may be
brought back to a
youthful stage of
development at any
time by uplifting
the land.
(ex. Grand Canyon)
Name the part of the
stream’s life cycle in the
picture
FQ:
What shape do stream valleys make?
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