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Geo Questions - 2 > Own Knowledge - Rivers > Flashcards

Own Knowledge - Rivers Flashcards

1
Q

types of weathering

A

physical - freeze thaw
chemical - acid rain
biological - roots of plants

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2
Q

types of mass movement

A

sliding
rock fall
slumping

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3
Q

types of erosion

A

hydraulic action - sheer force of the water
abrasion - material carried by the river being rubbing against banks and bed of the channel, wearing it away
solution - minerals dissolve into water - slightly acidic - dissolve rocks
attrition - sediment particles collide with each other - rounder and smaller

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4
Q

types of transportation

A

traction - rolling along river bed
saltation - bounce over eachother on the river bed
suspension - the water flow carries silt and clay-sized particles
solution - river water dissolves some minerals

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5
Q

how do interlocking spurs form

A
  • upper course
  • erode downwards
  • flow around the hardest parts of the rocks
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6
Q

how do waterfalls form

A
  • band of hard more resistant rock lies over a band of soft rock
  • river erodes less resistant rock at a faster rate - undercutting it
  • eroded by hydraulic action and abrasion
  • hard rock overhangs
  • hard rock falls under force of gravity
  • falling rocks cause erosion of the river bed and the formation of PLUNGE POOL
  • gorge forms as waterfall retreats = soft rocks eroded and hard collapses - gorges form in hard rock where vertical erosion is dominant
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7
Q

how do meanders form

A
  • found in flood plain
  • highest velocity on outside of the bend - lateral erosion
  • forms a RIVER CLIFF
  • inside of bend - velocity less - deposition
  • forming a POINT BAR
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8
Q

how do oxbow lakes form

A
  • rivers erode outside of bend fastest
  • narrows the neck
  • eventually erodes through neck
  • new river by passes the meander
  • dries up leaving an oxbow lake
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9
Q

how is a flood plain formed

A
  • formed by both erosion and deposition
  • lateral erosion on outside of bends of meanders means they MIGRATE across valley floor + erode Vally sides = valley floor becoming wide and flat
  • during floods - flood water spreads across valley floor + deposit fine sediments called ALLUVIUM as it loses energy - flat land
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10
Q

how do levees form

A
  • natural embankments of sediment on either side of a river
  • during a flood water come out of channel and lose velocity
  • deposits the larger + heavier material first on its bank
  • repeated flooding causes these banks to get higher - forming levees
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11
Q

how do deltas form

A
  • when rivers meet another body of watet eg. ocean - loses velocity + deposits sediment
  • if river deposits faster than it erodes = sediment builds up in a fan-shaped DELTA
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12
Q

how does width change from source to mouth

A
  • increases
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13
Q

how does depth change from source to mouth

A

increases

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14
Q

how does velocity change from source to mouth

A

increases

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15
Q

how does discharge change from source to mouth

A

increases

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16
Q

how does gradient change from source to mouth

A

decreases

17
Q

how does channel roughness change from source to mouth

A

becomes smoother = less friction

18
Q

how does sediment size change from source to mouth

A

becomes smaller + rounder

19
Q

define lag time

A

the difference between peak rainfall and peak discharge

20
Q

flashy hydrograph

A
  • steeper rising limb
  • short lag time
  • higher peak discharge
21
Q

subdued hydrograph

A
  • gentler rising limb
  • longer lag time
  • lower peak discharge
22
Q

how does drainage size and shape affect hydrograph

A
  • small, elongated = higher discharge

- circular = lower discharge

23
Q

bridging points on river severn

A

Shrewsbury

24
Q

antecedent conditions - river severn 2007

A

140mm - highest in 100 years

25
Q

why is the risk of flooding increasing

A
  • increasing population = building on floodplains
  • changes to land use = urban development creates more impermeable surfaces
  • changes to weather patterns = climate change
26
Q

Tewksbury damage

A
  • 4800 homes affected
  • each home had estimated repair cost of 20,000 - 30,000 pounds
  • local council - 140,000 pounds
27
Q

who is responsible for managing the risk of flooding

A

environment agency

28
Q

how does the environment agency reduce chance of flooding

A

catchment management = rating the risk of properties

hard + soft engineering

29
Q

hard engineering strategies

A
  • flood walls
  • embankments
  • flood barriers

building infrastructure to overcome challenges

30
Q

advantages and disadvantages of embankments

A
  • high banks built on or near a river / man made levees

advantages

  • stop water from spreading into areas where it could cause problems - eg. settlements
  • they can be earth and grass - which blend into environment

disadvantage

  • flood may go over the embankments
  • can burst under pressure, causing even greater damage
31
Q

advantages and disadvantages of flood walls

A

artificial barriers designed to raise the height of river banks

advantages
- increases capacity + prevent water from spreading

disadvantages

  • expensive to build
  • may cause flooding downstream
  • ugly
32
Q

advantages and disadvantages of demountable flood barriers

A

a temporary structure that is only installed when needed

advantages

  • put up and taken down when needed
  • prevent so much ugliness

disadvantages
- may not be installed in time

33
Q

advantages and disadvantages of permanent flood barriers

A

flood gates built near the river mouth to prevent a storm surge form flooding

advantages

  • gates can be closed when a high surge is forecasted
  • able to protect large areas

disadvantage

  • high cost
  • ugly
34
Q

examples of soft engineering

A
  • flood plain retention
  • river restoration

working with nature to encourage natural processes

35
Q

advantages and disadvantages of flood plain retention

A

strategies to maintain rivers original flood plain = allowing rivers to flood and intentionally allowing areas of floodplain to build up - this slows down the river flow reaching areas of economic importance + planting trees

advantages

  • slow waters down
  • recover a rivers natural sedimentation process - helps the soil more efficient at storing water

disadvantage
- may require a change in land use - eg. a change in farmland

36
Q

advantages and disadvantages of river restoration

A

restoring a river to its natural course of meanders to slow rivers down + remove impermeable surfaces and replace with natural materials to promote infiltration

advantages

  • more attractive for recreation
  • create natural habitats which benefit wildlife

disadvantages
- changes in land use

Geo Questions - 2 (10 decks)

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