Rivers Flashcards
(75 cards)
What is the transportation process known as solution?
Takes soluable minerals such as calcium carbonate, it has any flow conditions, minerals are dissolved from soil or rocks and carried along in the flow.
What is the process of suspension?
Takes small particles such as clay and silt, occurs in all but the slowest flowing rivers, tiny particles are carried long distances in the flowing water.
What is the process of saltation?
Takes sand and small gravels, it occurs in more energetic rivers with higher velocities, the sediment bounces and skips along.
What is the process of traction?
Takes larger gravels, cobbles and boulders, only common in high energy river channels/flood events, the bed load rolls along in contact with the river bed.
When does erosion occur in a river?
Where it has plenty of energy eg. Flowing quickly or when the river is full of water after heavy rain.
Where do rivers that flow across gentle slopes flow with greatest force?
Other bend of each curve or meander.
How is a river bank eroded?
Water is thrown sideways into the river bank and is eroded by hydraulic action and abrasion. The bank becomes undercut.
What happens after a river bank becomes undercut?
Overhanging soil slumps into the river channel where the new load is transported downstream by the flowing water.
What is the erosional process of hydraulic action?
Water crashes into gaps in the soil and rock, compressing the air and forcing particles apart.
What is the erosional process of abrasion?
The flowing water picks up rocks from the bed that smash against the river banks.
What is the erosional process of attrition?
Rocks carried by the river smash against one another, so they wear down into smaller and more rounded particles.
What is the erosional process of corrosion?
Minerals such as calcium carbonate (the main part of chalk and limestone rocks) are dissolved in the river water.
Where does deposition occur?
Where the river loses its energy.
Where might a river lose its energy?
Enters a lake, flow is slowed by the body of still water.
Very shallow sections of a river channel, where the friction between the river bed and the water causes the river to lose its energy and deposit its load.
What does the process of deposition create?
Layers of sand and gravel that are sorted by sediment side because the coarsest sediment is often deposited first.
In what direction do rivers flowing over steep gradients tend to erode?
Vertically because as the river flows downwards it cuts into its channel and produces a narrow valley with steep V shaped sides.
What might the rocks of the river bed in a river flowing over a steep gradient show?
Evidence of abrasion in form of smoothly cut potholes (scour holes)
What do rivers flowing over steep gradients have enough of?
Enough energy to erode and transport large quantity of material.
What happens to a rivers load as it flows downstream?
It decreases due to attrition (rocks carried by river smashing into one another wearing down into smaller and more rounded particles).
What do rivers flowing over gentler gradients tend to do?
Swing from side to side.
What is lateral erosion?
Water flows fastest on outside bend of each meander, causes erosion of banks rather than bed.
What is afforestation and why is it a good flood management method?
It is planting trees and it is good as it intercepts rainwater before it reaches the soil.
What are the disadvantages of afforestation?
Can’t be used everywhere as it involves a lot of space.
What are sluice gates and why are they a good flood management tool?
They form a temporary dam, blocking water if there was a surge.
