Fluvial Processes

Question 1

When does most erosion occur

Answer 1

Hugh flow when volume and velocity are greater and river energy is at its maximum

Question 2

Erosion operates in 2 ways:

Answer 2

Vertical- river load scrapes against and eventually lowers the level of the bed= steep valley sides + waterfalls

Lateral- fast flowing, enough energy to wash away part of bank. Can lead to undercutting

Question 3

Four different erosion processes:

Answer 3

Corrosion/Abrasion- fragments scrape along bed and banks wearing them away

Attrition- reduction in size and angularity of particles as they collide together.
Large and angular at source —> small and rounded near mouth

Hydraulic action- most effective on soft loose material picked up by frictional array of flowing water
Can weaken rock by forcing air into its cracks

Solution/corrosion- rainfall slightly acidic
When river flows over alkaline rocks, minerals are dissolved and then carried away in solution

Question 4

4 ways of transport

Answer 4

Traction- rolling and sliding of large rocks along river bed

Saltation- bouncing if medium sized load

Suspension- small load suspended in the water

Solution- soluble minerals are carried away via solution transport

Question 5

What is deposition and when is it likely

Answer 5

River loses energy, load can no longer be carried, deposited. Largest to smallest (large is more energy)

Likely when: river enters sea, river foods into floodplain, area of shallow water, load is increased suddenly eg landslide