2023 paper

Question 1

Explain two reasons for the variation of deposition along a river channel

Answer 1

• decrease in sediment size due to erosional processes
• meanders

Question 2

Explain why minimum velocity needed for sediment erosion varies

Answer 2

• larger sediment, heavier and so more energy needed
• clay has weak chemical bonding so stronger cohesion so more energy needed

Question 3

Explain why there can be a difference between the state of water during the daytime and night-time

Answer 3

At daytime large amounts of incoming solar radiation causes water to evaporate and so is likely to be in gaseous stae.

At night, radiation cooling and lack of solar output means ground/air cool down and so result in the condensation of water when it reaches dew point resulting in a liquid stat

Question 4

Explain how mass movement can affect the slope of an area

Answer 4

• scree/debris at bottom
• reduction in vegetation
• increased water at bottom of slope
• exposed cliff face
• terracettes (soil creep)
• decrease in angle at base as slope material is built up

Question 5

Briefly explain why precipitation may not always reach a river channel

Answer 5

may be intercepted and stored on vegetation and then uptake by plant roots

• may evaporate from the surface in times of strong solar output

Question 6

Outline two factors which influence the formation of a braided channel.

Answer 6

• increase in sediment load results in deposition
• multiple channels created in times of low flow/flat gradient

Question 7

Describe and explain how soft engineering and hard engineering can be used to prevent river
floods

Answer 7

Hard engineering:
Dams and reservoirs
Channel straightening ( flow faster so less likely to overflow)
Embankment (Bangladesh): increases channel capacity
Diversion spillways
Flood relief channels

Soft engineering:
Wetland conservation/floodplain zoning: means area allowed to flood so wont flood elsewhere
Afforestation

Question 8

Urbanisation always results in an increase in channel flow.’
With the aid of examples, how far do you agree?

Answer 8

Reasons for:
- impermeable surfaces (rapid urbanisation)
- drainage systems straight to river channels
- deforestation (Bangladesh 50% less in 20 years)
- increase in precipitation as a result of urban heat island effect
- canals in dhaka vital for drainage but blocked with sewage due to urbanisation
- wetland area in dhaka now used for industrial

Reasons for decrease:

• Dams kaptain dam which is an earth-fill embankment dam with a reservoir and reservoirs
• Diversion of water into canals
• afforestation may result in decrease in urban areas