River Erosion and Deposition
Rivers Shape the Land
• Even the smallest stream has the ability to
pick up objects
• Erosion is the process by which fragments of
soil and rock are broken off from the ground
surface and carried away.
• These fragments are carried away until they
are eventually dropped off or deposited in a
new location
Rivers Shape the Land
• Deposition is the process by which soil and
rock are left behind
• Rivers wear away land forms through erosion
and build new landforms through deposition
• Particles that are picked up and dropped off
by moving water are called sediment.
• Sediment that has not been dropped off is
called a suspended load.
Rate of Erosion/Deposition
• A river’s speed affects its ability to wear away
or erode the land
• Faster speed = more energy
• Slower speed = less energy
• The more energy a river has the heavier the
sediments it can move.
• As a river slows it drops the heavier sediments
first.
What affects the speed of a river?
• Steepness of its slope
• Volume of water in the river
– Increase in water = increase in speed
• Shape of the river channel
– As the water rubs against the sides and bottom it
creates friction
– In a narrow and shallow channel there is more
friction so the water flows slowly
What affects the speed of a river?
• Friction between the water molecules and
sides and bottom of river cause the water to
move slower
• The velocity of a stream is the greatest away
from the bottom and sides
• On the outside of curves
Parts of a River
• Headwaters- small streams that come
together at the source of a river
• Flood Plain
– River created valley by erosion
– Small obstacle cause a bend in the river
– River flows faster on the outer edge of the curve
causing erosion
– River deposits sediment on the inner curve
Parts of a River
• The process of erosion and deposition creates
a looping curve known as a meander.
• Eventually the river may break through the
meander and create a new channel.
• The crescent shaped, cutoff body of water is
called an oxbow lake.
• Mouth – the point where a river flows into
another body of water
Parts of a River
• As the river’s water reaches the larger body of
water the speed of the rivers slows.
• This causes sediments to deposit at the mouth
of the river
• The deposits build up forming what’s called a
delta.
River Erosion ABC Write
• Is a river more likely to erode the land around
its headwaters or at its mouth? Why?