RIVERS Flashcards
How does the river valley shape change from upper to lower course?
Upper course = V shaped valley
Middle course = Deeper and wider
Lower Course = Wide and Deep
Explain why the process of erosion is more dominant in the upper valley course compared to lower course?
Upper course erosion is more dominant due to the larger sediment which causes erosion to be harder compared to lower course which has small sediment
What does the long profile of a river show?
how the gradient changes as the river flows from source to mouth
Explain why a river is wider in the lower course compared to the upper course?
Lower is wider due to lateral erosion while there is vertical erosion in upper course valley
What are the four different types of erosions?
Hydraulic action = water hitting the river bed
Abrasion = Rock hitting river bed
Attrition = Rocks eroding one another
Solution = Chemicals in water eroding river bed
What are the four different types of transportations?
Traction = Large rocks roll along river bed
Saltation = Rocks bounce along river bed
Suspension = Fine material carried by river
Solution = Dissolved materials carried by sea
Why does a river deposit its load?
When velocity or river decreases, energy is reduced therefore deposits
What is the formation of a waterfall?
- The soft rock is eroded by hydraulic action, which creates a plunge pool
- That then creates an overhang, which collapses by weathering
-The waterfall retreats which creates a gorge (steep sided deep river valley).
Formation of interlocking spurs?
Ares of hard rock (which are harder to erode) where the river bends around it
How is meander formed?
- The current is faster on outside of bend since the channel is deeper.
- Therefore more erosion takes place on river bend and causes a river cliff
- Current is slower inside river bend since channel is shallow
- Therefore eroded material is deposited on the inside, causing a slip-off slope
Describe and explain the flood plain?
- River floods onto flood plain, water slows down so eroded material is deposited. That builds it up.
- Meanders migrate across flood plain making it wider
3.Deposition that happens on the slip-off slopes on meanders also help to build up the flood plain
Describe and explain formation of a levees
- During flood, thickets sediment is deposited at channel edges
- Thin sediment is deposited over the outer parts of floodplain
What is an estuary?
A freshwater of river or stream that meets the ocean
Three physical causes of flooding?
Relief = if the valley is steep, rain does not get the chance to infiltrate and runs off quickly
Prolonged rainfall = after rain, the soil becomes too saturated and can’t allow any more filtration
Snow melt = when a lot of snow or ice melts, a lot of water goes into river
Two human ways of flooding?
Urbanisation = Urban areas have a lot of impermeable surfaces like tarmac. This means the water runs off the surface into the river
Deforestation = The trees intercept the rainwater. Cutting down increases surface-runoff.
