Rivers

Question 1

Upper course features

Answer 1

Steep sides - V shaped valley, interlocking spurs
Vertical erosion

WATERFALL, RAPID, POTHOLE, V SHAPED VALLEY

Question 2

Middle course features

Answer 2

Wider channel
Sloping sides
Tributaries join - more water
Vertical + lateral erosion

MEANDER, OX BOW LAKE

Question 3

Lower course

Answer 3

Deep
Wide/flat valley floor
Fast flowing - little friction
Smaller, rounded bedload (attrition)

FLOODPLAIN, LEVEE

Question 4

River erosion (4)

Answer 4

Hydraulic action: power of water against bed/bank; pressuring air into cracks

Corrasion: river uses load to erode bed/bank, sand papering (repeatedly)

Corrosion: chemicals in water dissolve rocks

Attrition: particles crash against each other + break into smaller pieces

Question 5

River transportation (4)

Answer 5

Solution: dissolved load (not visible)

Suspension: v fine material floats on surface

Saltation: load bounces along bed

Traction: large load rolls along bed

Question 6

Deposition

Answer 6

More friction, velocity decreases, less energy, drops off load on inside of meander (flood) or delta

Question 7

Rapid

Answer 7

Part of river with fast current

1. Less resistant downstream eroded faster
2. Steeper gradient, more energy/velocity, rapid flow
3. Or load deposited on upstream meander

Question 8

Pothole

Answer 8

Cylindrical hole in top of river

1. Water circulates repeatedly
2. Large stones rotate, current erodes down
3. Circular holes get deeper into river bed

Question 9

Waterfalls

Answer 9

1. Less resistant more rapidly eroded than more resistant #
2. Hydraulic action/abrasion enlarge plunge pool
3. Harder rock undercut
4. Harder collapses (unsupported)
5. Retreats upstream to form gorge

NIAGRA: falls over escarpment, more energy, faster erosion of underlying less resistant rock to form plunge pool

Question 10

Q: FORMATION

CS Niagra Falls (x2)

Answer 10

12 300 years ago, North America ice sheets melted (water)
Flowed over more resistant rock + plunged over Niagra escarpment

Benefits:
Tourism - 12million, local economy, jobs (hotels)
Hydroelectric power plants - cheap, renewable

Problems:
Transport across Lake Ontario + Eric
Tourism - noise/air/visual pollution
Flooding

Question 11

Meander

Answer 11

1. Less friction, high velocity, more erosion on outside
2. Faster flowing so bank becomes deeper + laterally eroded (river cliff)
3. More friction, low velocity, more deposition on inside
4. Slower water so more deposition (slip-off slope)

River cliff: erosion on outside, loosening of bank, gentle overhang
Slip-off slope: lower velocity, deposition on inside

Question 12

Oxbow lake

Answer 12

1. Water pushed to outer bend in meander
2. Higher velocity, more energy, hydraulic action/abrasion laterally erode outer to form river cliff
3. Continues, so neck of meander narrows
4. In high flow/flood, neck broken
5. Follows shorter straighter path - fastest current now in centre
6. Deposition along banks, old meander sealed off
7. Oxbow lake dries up

Question 13

Flooplains

Answer 13

1. Lateral erosion widens river
2. High discharge, lots of energy, transports large amount
3. Overflows/floods, spread across flat land
4. More friction, less velocity, deposits (large first: levee)
5. Less energy, recedes, repeats leaving load

Question 14

Levees

Answer 14

Natural ridge on banks of river channel

1. Floods, more friction, less velocity/energy
2. Deposits on floodplain
3. Largest load first building levee
4. Finer material spread out in layers
5. Repeats

Question 15

Why live on floodplain (Adv + Dis)

Answer 15

ADV: Fertile soil - high yield 
Washing/drinking/rice water 
Communications 
Fish 
Flat land (build) 

DIS: Flood
Need to bridge river
Densely populated - competition

Question 16

Along profile …

Answer 16

Flatter, smoother bed, volume of water increases

Steep height reduction (source) then gradual (downstream)