Download WATERSHED or DRAINAGE BASIN Organized runoff This is the

Erosion – the carrying away of weathered
rock by gravity, water, wind, and ice
Running Water
Wind
Ice
Gravity Erosion:
mass movements of materials
down hill
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Soil creep (slow, 1 cm/year)
Debris flow (slow to fast, mm/day – km/hr)
Mud flow (fast, 1-5 km/hr)
Rock fall (very fast, >4 km/hr)
SOIL CREEP
Rock Fall
Rock fall
Most erosion is caused
by water moving across the
Earth’s surface (runoff)
Random runoff – this is rain water that runs down any exposed
slope and often produces gullying
1. slope
3. low permeability
RECALL:
What factors favor
runoff?
2. lack of
vegetation
4. saturated ground
Notice the many
gullies
Badlands National Pa
(South Dakota)
Similar gullying in
Bryce Canyon in Utah
Random runoff –produces gullying
Organized runoff – this is water that moves through
a series of developed channels until it eventually
reaches the ocean. Also referred to as a
drainage pattern.
The area drained by a river and its tributaries is called a
WATERSHED or DRAINAGE BASIN
Organized runoff
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Continental
Divide
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This is the Mississippi
River drainage basin or
WATERSHED
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The small rivers are tributaries
of the Mississippi River
Every location in
green, drains into
the Mississippi
River
Which way is the river flowing?
Which are the tributaries?
Grand Canyon from space
Young
Mature
Old
Rivers and streams
can be grouped into 3 stages
of development
Summary of Young Stream
1. Mostly erode down
2. High velocity, steep gradient
3. Characterized by rapids and waterfalls
4. Narrow and carve a “V” shaped valley
5. Straight unless forced to curve by topography
6. canyons may form
Streams start out high in the
mountains as young streams
These young mountain
steams have a high
velocity and can move
even large boulders
Their velocity and
eroding power grows
as smaller streams join
the main stream
Young rivers often carve
“V” shaped valleys
The young stage usually produces
a “V” shaped valley
Waterfalls and
rapids are common
In this stage
Grand Canyon
When a young river
cuts through a
plateau, a canyon
is created
Velocity of any stream is determined by:
1. Gradient or slope of land
2. Volume of water in stream
Streams usually flow fastest
In spring, why?
Glacier Nat. Park
solution
Rivers and streams transport
rock and sediment in 3 ways
suspension
Rolling and
tumbling
Abrasion causes rocks
in a stream to become rounded