Fluvial Erosion Flashcards
What does a rivers total energy depend on
The weight of water, the height of the river above its base level, the steepness of the channel (controls speed and kinetic energy)
How is energy in a river lost
Internally (turbulence within the flow) or externally (contact with the bed and banks) + friction
What are the 4 erosional processes
Abrasion (corrasion), hydraulic action, corrosion, attrition
What is abrasion (corrasion)
The scraping, scouring and rubbing action of materials carried along by a river (the load).
When is abrasion most effective
In short turbulent periods when the river is at bankfull or flood
What is hydraulic action
Caused by the sheer power of moving water. The movement of loose unconsolidated material due to the frictional drag of the moving water on sediment lying on the channel bed.
When is hydraulic action most effective
At meanders- which leads to undercutting and collapse
What is corrosion
The minerals in a rock are dissolved by weak acids in the river water and carried away in solution
When is corrosion most effective
On rocks that contain carbonates eg limestone and chalk
What is attrition
The reduction in size of fragments and particles within a river due to the processes described above
What kind of pebbles are found upstream
Larger and more angular (whereas smaller and round pebbles downstream)
Why do rivers erode
Because they possess energy
