Rivers Flashcards
How does a river form?
Start in upland areas because you get relief rainfalls which is caused by the shape of the land.
what is long profile?
Shows how river gradient changes as the river moves from its upper coarse to its lower coarse.
What do we get in the upper course?
Steep gradient
v shaped valley due to vertical erosion
River is narrow, shallows and turbulent (frothy and shaky bouncing off rocks)
Large bedload (rocks and boulders) - mainly transportation
What do we get in the middle course?
Gentle gradient
Wider valley+ flat floor ( lateral eriosion and deposition)
deeper
has smaller material in the load (pebbly) - transportation
What do we get in the lower course?
Very gentle gradient
very wide valley and flat (mostly deposition)
deep river
has mainly suspended load (suspension)
mostly deposition on river mouth ( estuary
name the erosion types
Abrasion
Hydraulic action/impact
Attrition
Solution
What are the transportation types?
Solution
Saltation
Traction
Suspension
What is a meander?
Meanders are bends in a river usually found in a rivers middle course. They are natural features formed by erosion and deposition.
What is the formation of meanders?
- The water in the river flows fastest on the outside bend and wears the river away (thalweg) this causes increased speed and increased erosion /hydraulic action and abrasion)
- The slowest flowing part of the river is on the inside bend. This is where it deposits it’s load of alluvium. Meanwhile on the outside bend the riber continues to cut into the bank.
- the result is that the river bends more and more
- Oxbow lake is formed when the neck of the meander gets narrower. The river then cuts through the neck and shortens in leaving behind old river which is cut off by deposition. ( crescent shaped lake)
What does the erosion and deposition in river create?
River cliff - outside bend causes undercutting of the bank
Slip of slopes - gentle slope of built-up sand and shingle
What is a bluff?
Furthest point at where the river once had been which created a rise in land eitherside.
Will urban areas be at risk of flooding?
Urban areas are likely to lead to flooding because the water will not infiltrate in the ground.
More overland flow so river discharge will increase.
Rural areas and flooding.
Covered in farmland and rainwater can soak into the land. - water gets to the river slowly and decreases chance of flooding.
Deforestation
Trees intercept - if trees are cut down the rain wont go to the trees but will go straight to river. Increases the river discharge -flooding
Farming
Tractors dig the field up when crops are picked. - mini channels and directs water quickly to river.
