Rivers, 10 Flashcards
Source of the river is…
Where a river begins.
Drainage of the river is…
The area from which water drains into the river.
Watershed of the river is…
An imaginary line that separates two drainage basins.
Confluence of the river is…
The point where two rivers join together.
Tributaries of the river is…
Smaller rivers which joins the main river.
Flood plain of the river is…
Land that floods when a river overflows.
Mouth of the river is…
Where a river flows into the sea or lake.
River Bad of the river is…
The bottom of a river channel.
River Bank of the river is…
The side of a river channel.
Channel of the river is…
River flow in this
The middle Course of the river is….
In the middle course, the river starts to flow slowly because it starts to transport lots of sediment, as rivers look muddy. As a river mover down its valley, a number of changes occur. The river gets wider, as more tributaries join together.
- the valley sides become less steep, giving the shape of a open V.
- the river begins to erode sideways, into its banks. This opens out the valley floor and a flood plain that starts to develop.
- erosion and deposition occur.
- the edges of the floodplain are market bluffs.
The upper Course of the river is…
The steepest part of land in the river. It is usually small, but flows quickly. The energy levels are high and the river cuts away at its bed. As it does it quickly deepens its valley. Downward erosion is the dominant process. ( velocity of river is slowest in the upper course)
Erosion is…
The gradual removal of rocks from a river’s banks and bed.
Abrasion/Corrasion
Rocks carried along by the river wear down the river bed and banks. The river is using the load it is carrying like sand paper to wear down its bed and banks.
Hydraulic action
The force of the river against the banks can cause air to be trapped in cracks and crevices. The pressure builds, weakening the bed and banks and gradually wearing them away.
Solution / Corrosion
Soluble particles and minerals are dissolved into the river. ( Similar or sugar granules dissolving in tea or coffee)
Attrition
Rocks being transported by the river smash together and break into smaller, rounder and smoother pieces. ( these same rocks are responsible for abrasion )
River landforms, upper course: V-shaped valleys
The river erodes downwards as boulders, stones and rock particles are bounced and scraped along the channel bed.
As the river cuts down, the steep sides are attacked by weathering. This breaks up and loosens the soil and rock.
The loosened material slowly creeps down the slope because of gravity or is washed into the river by the rainwater. The river carries it away.
The end result is a speed sided valley that has the shape of a letter “V”
Four main factors affect the rate of river erosion.
- Gradient - a steep gradient results in the river water being pulled by gravity, cutting down and eroding the channel.
- Rock resistance - erosion rate increases more erodible the rock - for example limestone is easily eroded - harder rocks such has igneous rock are difficult to erode.
- Velocity - erosion rate increases as velocity increases - more load can be carried and therefore more erosion occurs.
- Discharge- erosion increases is discharge Increases. The water in a river the more power it has.
Meander is…
It is formed by…
Band in the flow of the river.
It is formed by abrasion.
Ox-bow lake…
A horseshoe or semi-circular area that represents the former cause of a meander.
! River meander are formed by lateral erosion!
Formation of ox-bow lake + meander
- A meander starts as a slight bend. Water flows faster on the outside of the bend that on inside.
- So the outside of the bend is eroded away. Material is deposited on the inside of the bend.
- This erosion and deposition turns in the bend into a meander.
- The meander bends more and over the years until it becomes a really tight loop.
- When the water level is really high, the river has enough energy to go straight across the loop, rather than round it.
- This is called a meander cut-off.
- The river keeps to its new channel, so the loop is left as an ox-bow lake.
- After a long time, the ox-bow lake slits up and dries out, and plants grow in it.
Floodplain is…
The area of flat land adjacent to the river channel in the lower course. Created to allow water to overflow once bank full conditions are reached.
