Rivers Flashcards
What causes a river to flood?
Sometimes after heavy rain or rapid snow melt, there may be too much was for the river to hold so it will overflow it’s banks and spread out across the land on either side of it’s channel
Where does the water flowing down a river come from?
It comes from rain or melting snow
What factors increase the risk of flooding?
- Rock and soil type
- Steep Slopes
- Deforestation
- Urbanisation
What caused the Bangladesh flood? (please check your book - I can’t see them)
- The population
6.
7.
How does Bangladesh cope with floods? (please check your book, I can’t see them)
- Build dams
- Provide emergency help
- Give after-care
How can the risk of flooding be reduced? (again, check the book)
1.
What is the source of a river
This is where a river begins (usually on mountains where there is heavy rainfall and melting snow)
What is a tributary?
It is a small river or stream which joins the main river
How does a river erode?
- Abrasion
- Attrition
- Hydraulic action
- Solution
What are Oxbow lakes?
They are horse shoe shaped lakes found next to rivers. They are remains of old meanders which has been cut off from the main river during a flood.
What is a meander?
It is a curve in a river - made when rivers bend side to side in upland areas so when they reach lowlands, the curves can become large
Where is the rivers flow the fastest?
On the outside bend of a meander
What is alluvium? (sometimes called silt)
Flood planes are made up of alluvium - it is a muddy material left behind after floods
Why is a flood plane useful to people??
They are flat land and they have rich fertile soil which makes them good for building on and for farming.
Not a question, just know this ->
The outside of a river bend (where water travels fastest) get eroded quickly. Where as the inside of a river bend (where water travels slow) gets built up by deposition.
That’s why in those cross-section diagrams, the river is deeper on the outside of the bend and shallow on the inside of the bend.
Features of a river in it’s old stage
- Has a large volume of water
- Very wide
- Flows through a flood plain
- Floods often
- River banks are low
- The river forms a lot of meanders
What are the raised areas of a river bank called?
Bluffs
Features of landforms that a river forms in the lower stage are..
- Ox-bow lakes
- Flood Plains
- Levees
- Estuaries or Delta’s
What is a delta?
It is a low-lying area of land formed at the rivers mouth.
What is a river channel?
It is a valley in which a river flows.
The sides of a valley are called?
Banks
What is the mouth of a river?
This is where the river ends. Usually in the sea but may be a swamp or lake.
What happens in the middle stage of a river?
Main work is transport -> traction, saltation, suspension and solution
Features of a river in the middle stage?
- The slope is more gentle
- The river is much wider
- The volume of water is higher
- Main work is transport
What is the main work of a river in it’s lower course?
Deposition.
What is a river beach?
This occurs when deposition on the inside of a meander builds up into an area of shallow land.
What are distributaries?
This happens when the main river splits into many smaller rivers. These smaller rivers are called distributaries.
How are braided rivers formed?
The deposition of material on the valley floor sometimes causes the river to split into several channels.
How are levées formed?
When a river overflows it’s channel, deposition takes place on the banks of the channel and this produces an edge-like feature - this is called a levée
