The Long Profile-processes Flashcards
Cavitation
In this process, bubbles form in flowing water. These bubbles can implode next to or within cracks in the bank. They then evict tiny jets of water that can move up to 130m/second
Abrasion
The wearing away of the bank and bed by the load of the river. It is the mechanical impact of debris as it is picked up and bashed against the river.
Hydraulic action
The sheer force of the water and air against the bed and banks. Includes evorsion and cavitation.
Solution
The removal of chemical ions, especially calcium.
Attrition
The wearing away of the load as it is transported by the river and bashes against one another.
Transportation- Suspension
Particles carried within the flow, usually very fine material
Transportation-Saltation
Particles move by bouncing along the river bed, e.g pebbles.
Traction
Load is dragged along the bed of the river, e.g rocks or boulders.
Upper course
Erosion- Abrasion and hydraulic action
Vertical erosion
Load moved in times of high discharge
Middle course
Erosion- Hydraulic action
Less vertical erosion and more lateral
Much smaller load, easier to transport - traction and saltation.
Lower course
Some hydraulic action
Suspension, larger load still moved through saltation and traction
Deposition
Graded profile
The idealised pattern is concave and has a smooth decrease in gradient
Wetted perimeter
The length of the banks and bed in a cross section in contact with the moving water.
Hydraulic radius
A measure of channel flow efficiency
Hydraulic radius = cross sectional area of river, divided by wetted perimeter
Evorsion
The direct force of flowing water. This is most effective in turbulent flow.
