River Enviounmnets Flashcards
What is erosion
River erosion is the wearing away of the landscape by the action of water.
What is vertical erosion?
When a river has a large load made up of coarse materials these scrape or rub against the channel bed, eventually lowering the level of the bed, to create steep valley sides. This is known as vertical erosion.
What is lateral erosion?
When a river is flowing fast the water has enough energy to wash away parts of the bank of the river. This leads to undercutting and collapse.
What is corrosion
Scraping and rubbing action of the load carried by the river. Rock fragments scrape along the bed and banks wearing them away.
What is attrition?
When particles become smaller and rounder in the river as they collide with one another, the bed and the banks.
What is solution
When a river flows over the alkaline underlying geology minerals in the rock are dissolved by the weak acids in the water. As they are dissolved they are carried in solution.
What is hydraulic action?
Caused by the sheer power of moving water. Air is pushed into the cracks and the rock is broken apart.
What is transportation?
The movement of material across earths surface
What is traction
The rolling and sliding of large rocks along the river bed. This process requires a lot of energy, and the largest bed load is only moved in times of flood.
What is saltation?
The bouncing of medium sized / pebbles load along the river bed.
Suspension
Very small load, which is continually held up or suspended in the water. Makes the water opaque
Solution (transportation)
Soluble minerals are carried via solution transport.
What is deposition
Deposition is the dropping of material on Earths surface.
Why does deposition occur?
Energy of water reduces. This could happen because
The river channel reaches a smaller gradient
River enters lake or sea
Discharge is reduced following a period of low rainfall
Areas of shallow water where friction reduces velocity.
What is discharge
The amount of water in a river which is passing a certain point in a certain time. Measured in cumecs (cubic meters per second)