Transcript Slide 1

HYDROSPHERE
Rivers
processes, profiles and landforms
HYDROSPHERE
What do you
remember/know about
rivers???
In your groups, spend 5
minutes noting down
anything you can think of.
HYDROSPHERE
In this section we will cover...
• River Processes
– Erosion, Transport, Deposition
• Profiles
– How a river changes as it progresses
towards its mouth.
• Landforms/features
– Key features and how they are formed.
HYDROSPHERE
Rivers processes
• Rivers like glaciers and the sea, are important forces in
shaping the landscape.
• All three not only erode the land but also transport and
deposit eroded material.
Erosion Processes
These erosion processes obviously take a long time to shape the
land and they are difficult to observe. But the land will wear down
more quickly if the rocks around the river channel are softer and
have more cracks.
Hydraulic action - When the sheer force of
the water in the river dislodges particles
for the rivers bed and banks
Corrasion - When smaller material carried in
suspension rubs (like sandpaper) against the
banks of the river. Can produce potholes.
Corrosion - When acid in the water dissolves
the rocks (such as limestone).
Attrition - Boulders and other material are
transported along the bed of the river,
these collide and break in to smaller pieces.
Transportation
When a river carries material this is called the load. The river
transports its load by a possible 4 processes
Traction: The largest rocks in the river are
rolled along the bottom of the river by the
force of the water. This primarily occurs in
the upper reaches of the river.
Saltation: Smaller rocks are bounced along the
riverbed in a leap frog motion. This occurs
most in the upper and middle sections of the
river.
Suspension: The water carries smaller particles
of material. This process occurs throughout
the course of the river, but increases the
closer you are to the mouth of the river.
Solution: Material is dissolved within the water
and carried along by it. Primarily this occurs
in the middle and lower reaches of the river.
Deposition
Deposition by rivers takes place when they can no longer transport
their loads. Any velocity decrease may occur:
• As rivers reach a base level by entering the sea or
loch.
• When rivers overflow their banks.
• On the inside bend of a meander.
• With a sudden decrease in gradient.
Processes and Energy
• The critical erosion velocity curve.
• The settling velocity curve.
Hjulstrom curce
HYDROSPHERE
Velocity in
relationship to
particle size