4b.3 - Valley Profiles

Question 1

Why does high discharge increase erosion?

Answer 1

Higher velocity / energy

Hydraulic action / abrasion are more effective

Question 2

Why does high discharge increase abrasion (erosion)?

Answer 2

Higher discharge increases river load (the amount of sediment)
This increases abrasion

Question 3

How do you calculate river discharge (the amount of water in a river)?

Answer 3

Width, depth (CSA) * velocity

= XXX cumecs (cubic metres per second)

Question 4

Why does river velocity increase downstream?

NB - 2 extended reasons max is enough

Answer 4

Wider and deep channel = less friction
Channel becomes a more efficient shape = less friction
The hydaulic radius increases = less friiction
Smoother channel = less friction
More tributaries join the main channel = more water in the river

(NB - you don’t need to know all of these - 2 max)

Question 5

Identify 3 landforms found in the middle/lower course of a river?

Answer 5

Meander
Ox-bow Lake
River Channel

Question 6

How does river shape change from source to mouth?

Answer 6

Increased size (width/depth), increase channel size

Question 7

How does river speed change from source to mouth?

Answer 7

Flow velocity increases
Why? Friction with the bed/banks/bedload decreases
Why? More water in the channel, less contact with the channel sides

Question 8

How does river bedload change from source to mouth?

Answer 8

Large angular rocks in the highlands
Middle course: erosion has made this material smoother and smaller
Lowland: most material is granular (sand and silt)