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Geography > River Landscapes (P1- SEC C) > Flashcards

River Landscapes (P1- SEC C) Flashcards

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1
Q

Upper course characteristics

A

Steep, V-shaped Valley
Narrow/shallow channel
High bed load

FEATURES :
V draped valleys
Interlocking spurs
Waterfalls
Gorges

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2
Q

Middle course characteristics and features ?

A
  • open , gentle sloping valley with floodplain
  • wider /deeper channel
  • more suspended sediment

FEATURES :
- meanders
- river cliffs
- slip off slopes

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3
Q

Lower course characteristics and features ?

A
  • open gentle sloping valley with floodplain.
  • flat and wide floodplain
  • wide open valley
  • very wide /deep channel

FEATURES :
Oxbow lakes
Flood plains
Levees

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4
Q

Watershed ?

A

The boundary dividing one drainage basin from another

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5
Q

Confluence ?

A

Where 2 river join

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6
Q

Hydraulic action ?

A

Thé force of water hunting river bed/banks

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7
Q

Abrasion ?

A

Load carried by river repeatedly hits the bed / banks dislodging particles into the flow of the river

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8
Q

Attrition?

A

When stones carried by the river know against each other making stones smaller and rounded

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9
Q

Solution ?

A

River flows over limestone /chalk , the rock slowly dissolved

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10
Q

transportation processes (4)

A

Traction - large particles rolled over sea bed
Saltation: ‘bouncing of particles too heavy to be suspende
suspension : small sediment held in the river
solution : dissolved load

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11
Q

EROSION LANDFROMS : INTERLOCKING SPURS
- how is it formed and what are they?

A

outcrops of land along the river course in a valley

  • forms near source of river /not powerful enough to cut through ‘spurs of land’ so flows around the
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12
Q

EROSION LANDFROMS : V-SHAPED VALLEY
- how is it formed and what are they?

A
  • as small stream flows downhill steeply, the bedlam erodes downwards
  • this vertical erosion deepens the valley, making the sides deeper/exposed
  • overtime, weathering/gravity wear away steep valley sides, forcing material into the stream, which it uses to cut valley deeper
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13
Q

EROSION LANDFROMS : WATERFALL S
- how is it formed and what are they?

A
  • SOFTER ROCK erodes quicker undercutting hard rock , creating PLUNGE POOL
  • overhang collapses / falls into plunge pool increasing abrasion/ making plunge pool deeper
  • waterfall retreats
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14
Q

EROSION LANDFROMS : GORGES
- how is it formed and what are they?

A
  • NARROW, steep-sided valley usually found immediately downstream of a waterfall
  • formed by gradual retreat of a waterfall
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15
Q

EROSION LANDFROMS : RAPIDS
what are they?

A
  • FAST FLOWING, turbulent sections of a river where the river bed has a relativley steep gradient
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16
Q

EROSION/DEPOSITION LANDFROMS : MEANDERS/OXBOW LAKES
- how is it formed and what are they?

A
  • as a slight bend in a river occurs, water flows faster on outside bend (erosion) the. inside bend (deposition)
    -more exaggerated meanders due to erosion/deposition, so NECK BEGINS TO NARROW
  • in flood, river cuts the neck taking shortest route - DEPOSITION SEALS OFF OLD MEANDER
  • old meander is completely cut off , rive has a new course and ox bow lake is formed
17
Q

DEPOSITION LANDFORMS : FLOODPLAINS
- how is it formed and what are they?

A
  • wide flat area of Marchy land on either Side of a river
  1. meanders migrate across floodplain due to LATERAL EROSION -
    - when they reach the edge of floodplain , they erode edge of VALLEY
  2. when river floods, loses velocity and it deposits finer sediments
18
Q

DEPOSITION LANDFORMS : ESTUARIES
- how is it formed and what are they?

A
  • transitional ones between river and coastal environment
  • during a rising tide, river water is unable to be discharged into the sea
  • river’s velocity falls and sediment is deposited
  • deposits form MUDFLATS
  • MUDFLATS form into natural habitats called SALTMARSHES
19
Q

CASE STUDY : river tees
where, what landforms?

A
  • NE OF ENGLAND ( SOURCE HIGH IN PENNINE HILLS)
    LANDFORMS :
  • waterfalls/gorges (erosion)
  • meanders (erosion/deposition)
    -levees/floodplains (deposition)
20
Q

factors increasing flood risk
physical/human ?

A

PHYSICAL
- precipitation - lead to rapid saturation of upper soil, so excess water goes to rivers as surface runoff
- geology - impermeable rocks make water flow overland into river channels
steep slopes - cause greater overland flow/ shorter lag time

HUMAN
- urbanisation - creates impermeable surfaces causing rapid water movement into river channels
- deforestation - when trees are removed, more water available/transferred rapidly to channel - less interception/infiltration
- agriculture- soil is left exposed , leads to more surface run-off

21
Q

hydrograph?

A

a graph that plots a river’s discharge after a storm

22
Q

discharge ?

A

quantity of water that passes a given point on a stream or river bank within a given period of time

23
Q

peak discharge ?

A

highest discharge

24
Q

lag time?

A

time in hours between the highest rainfall hughest peak discharge

25
Q

HARD ENGINEERING: dams and reservoirs
Cost/benefits

A

Controls the river flow by blocking the river and letting water in a controlled way.

BENEFITS: multipurpose
- effective water regulator

Costs: expensive
- flood large areas

26
Q

HARD ENGINEERING: embankment
Cost/benefits

A

Raised river bank - hold more water

BENEFITS: - cheaper
- sustainable
- look natural

COST: concrete walls are unnattraxtive

27
Q

HARD ENGINEERING: channel straightening
Cost/benefits

A

Cut through meanders to create straight Channel - speed up water flow

BENEFITS : protects vulnerable location
COST: increase flood risk downstream
- unattractive
- unnatural
- damage habitats

28
Q

HARD ENGINEERING:
Flood relief channels
AD/DIS

A

Man made river channel constructed to bypass urban area
Benefit : reduce threat of flood
- reduces losses for those living nearby

DIS : expensive
- regular maintainence

29
Q

SOFT ENGINEERING : FLOODPLAIN ZONING
Cost /benefit

A

restricts different land uses to certain locations on the floodplain

BENEFITS: reduce losses from flood
Areas can be used for pasture , parklands and fields

COST : difficult to implement on floodplains , causes land prices to fall

30
Q

SOFT ENGINEERING : wetlands
Cost /benefit

A

BENEFITS: - efficient store of water
- valuable habitats to wildlife

COST: takes long for wetlands to establish and grow

31
Q

SOFT ENGINEERING : RIVER RESTORATION

A
  • course of river changed So river restoration can return it to original course

BENEFIT: reduce likelihood of flood
- more habitats
- restores wetland areas

COST : expensive
- can cause some areas to flood

32
Q

SOFT ENGINEERING : PREPARING FOR FLOODS /flood warning
COST/BENEFITS

A
  • river basins monitored remotely using satellites /tech by measuring rainfall/river levels

COST : ppl become ‘blighted’ by being at risk of flooding
- property values drop

BENEFITS : helps ppl prepare
- cheaper

33
Q

CASE STUDY : BANBURY
Location , affected , management

A

Location : floodplain of river CHERWELL
AFFECTED :
- closure of towns of railway
- 12.5 mill damage
- more 150 Homes/ businesses damaged

MANAGEMENT: - Earth embankment ( holds 3mill m3 of water )
- opening controls rate of flow downstream to Banbury
- raised A361 road
- pumping station to transfer excess water
- Biodiversity Action plan habitat with ponds to store excess water

34
Q

SOCIAL, ECONOMIC , ENVIRONMENTAL benefits/issues of Banbury ?

A

SOCIAL: - raised A361 avoided disruption to lives
- quality of life improved
- reduce anxiety of fear of flood

ECONOMIC : - cost £18.5 mill
- donors include ENVIRONMENTAL agency
- benefits are estimated to be over £100 mill

ENVIRONMENTAL : - 100000 tonnes of earth required to build embankment
- new BPA habitat created
-

35
Q

Flashy storm hydrograph
DESCRIPTION, WEATHER, ROCK TYPE, RELIEF, BASIN SIZE, VEGETATION

A
  • short lag time , high peak , steep rising limb
  • intense storm /rapid snow melt
  • IMPERMEABLE rocks
  • HIGH STEEP SLOPE —> more run off
  • small drainage basin
  • few plants /deforestation
36
Q

DEPOSITION LANDFORMS: levees
- how are levees formed and what are they?

A
  • levees are raised embankments alongside a river
  • when river floods, friction with land , reduces velocity and increases deposition
  • larger material is deposited first at sides of river, and finer material is deosoited further away
  • after many floods, sediment builds up to increase height of levées
37
Q

how do factors that increase flood risk make the hydrograph look like?

A

Short lag time
Steep rising limb
High discharge
As a result the river may not have the capacity to contain the water and so flood risk is higher

38
Q

how do factors that decrease flood risk make hydrograph look like?

A

Longer lag time
Gentle rising limb
Lower discharge
As a result the river is more able to cope with the water entering the channel and the flood risk is lower

Geography (13 decks)

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