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Geography > River Landscapes > Flashcards

River Landscapes Flashcards

1
Q

What is a drainage basin

A

an area of land drained by a river and its tributaries

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2
Q

Speed of a river high in the mountains near the source

A

where water is shallow there is friction with the bed and banks, slowing the rate of flow
(unless there are rapids where channel narrows and river becomes deeper, increasing flow)

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3
Q

Characteristics of a river further downstream

A

rivers channel is deeper due to the tributaries bringing additional water

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4
Q

In which course of the river would there be mostly erosional landforms

A

upper course

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5
Q

In which course would you find mostly** desposition** landforms

A

lower

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6
Q

What is hydraulic action

A

the force of water hitting the rivere banks and bed

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7
Q

What is abrasion

A

when the load carried by the river repeatedly hits the bed or banks dislodging particles into the flow of the river

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8
Q

What is attrition

A

stones carried by the river knock against each other, gradually making the stones smaller and more rounded

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9
Q

What is solution

A

when river flows over limestone or chald, the rock is slowly dissolved due to the midly acidic river water

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10
Q

Where are larger rocks found in the river course and why

A

upper course because they are too heavy for the river to carry long distances

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11
Q

What are interlocking spurs

A

land made of hard rock jutting out, causing the river to meander

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12
Q

How is a waterfall formed

A
  • when a river flows over a resistant rock then less resistant rock
  • the less resistant rock is easily eroded vertically, creating a step and more erosion causes the hard rock to be undercut
  • a plunge pool is created when hyraulic action and abrasion take place
  • erosional processes continue and create a larger overhang of resistant rock
  • eventually the overhanging rock collapses under its own weight, adding rocks and boulders to the plunge pool
  • and the waterfall restreates upsteram
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13
Q

what is a gorge

+ example

A

narrow steep-sided valley that is usually found immediatly downstream of a waterfall, formed by the gradual retreat of a waterfall
e.g chedder gorge

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14
Q

how is a meander formed

A
  • starts with a slight bend in the river.
  • erosion takes place on the outside of the bend where the flow of water is fastest (thawleg)
  • deposition takes place on the inside where flow of water is slow
  • river cliff formed on outside.
  • slip off slope formed on inside
  • process repeats
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15
Q

how is an oxbow lake formed

A
  • over time the neck of the meander experiences lateral erosion until it is broken through forming a new straighter channel
  • the old meander loop is cut of by deposition to form an oxbow lake as water takes the shortest route
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16
Q

What is a floodplain and where are they found (which course)

A

wide flate area of marshy land on either side of a river
found in the middle and lower courses

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17
Q

what are flood plains made of

A

alluvium (a sediment -silt)

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18
Q

why are flood plains used for farming

A

soils are very fertile

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19
Q

how are flood plains formed

A

during a flood, sediment/ silt is deposited as the water loses its energy. layers of sediment builf up over time to form a thick deposit of fertile aluvium

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20
Q

how and where are levees formed

A
  • occur in the lower course when there is an increase in the volume of water flowing downstream causing a flood
  • during a flood, water flows over the side of the channel, carrying sediment
  • the largest material is deposited first on the river banks and smaller material futher away
  • after many floods, the sediment builds up to increase the height of the river banks
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21
Q

why do levees reduce flood risk

A

because they increase the height of the river banks, meaning the channel can carry more water (a greater discharge)

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22
Q

How is an estury formed and where are they found

A
  • initially formed from rising sea levels
  • estuaries are transitional zones where river meets the sea
  • main process operating in estuaries is deposition meaning sediment is depositedmudflats
  • at low tide deposists form extensive mudflats which develop into natural habitats called saltmarshes
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23
Q

what is brackish water

A

a mixture of salt water and freshwater

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24
Q

where is the river tees

A

River in the North East of England.
It’s source is high in the Pennine Hills and flows east to meet the North Sea

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25
Q

what is the water fall in the river Tees called

A

High force waterfall

26
Q

what other river landscapes does the river tees have

A
  • meanders (near Yarm and Barnard castle)
  • levees
  • floodplains
  • large estuary, with mudflats and sandbanks which support wildlife in the area (sites such as Seal Sands are protected areas
27
Q

what is flooding

A

where land that is not normally underwater becomes inundated. Occues when a river channel no longer hold the amount of water flowing in it.

28
Q

physical factors increasing flood risk

A
  • precipitation (torrential rainstorms can lead to sudden falsh floods)
  • geology (rock type) impermaeble rocks speed up water flow
  • steep slopes - encourage a rapid transfer of water towards river channels
29
Q

Human factors of increasing flood risk

(land use)

A
  • urbanisaiton, building on a floodplain creates impermeable surfaces, water is quikly transferred to drains and ewers and then into urban river channels
  • deforestation, trees use water to grow and also store it, when they’re cut down, more water is suddenly available
  • agriculture - soil is left unused and exposed leading to more surface runoff.
30
Q

what does a hydrograph show

A

a graph that plots the river discharge after a storm over time

31
Q

what is the discharge

A

the volume of water flowing along a river

32
Q

what is the lag time on a hydrograph

A

time between the highest rainfall and the highest discharge
it shows how quickly water is transferred into a river channel

33
Q

what is hard engineering

what are its generic costs and benefits

A

involves using man-made structures to prevent or control natural processes from taking place

costs- financial cost and negative impact on environment and peoples lives
benefits- financial savings made by preventing flooding, along with any environmental improvement

34
Q

Dams + reservoirs pros

A
  • can be used to produce electricity by passing water through a turbine within the dam
  • reservoirs can attract tourists
  • effective in regulating water flow
  • used in irrigation
35
Q

how do dams and reservoirs help to prevent floods

A

during periods of high rainfall, water can be stored in the reservoir and then released when rainfall is low

36
Q

Dams and reservoirs cons

A

very expensive
people may have to be displaced to allow construction
habitats are flooded leading to rotting vegetation which releases methane ( a greenhouse gas)

37
Q

channel straightening pros

A
  • used to reduce flood risk in built up/ vulnerable areas
38
Q

what is channel straightening

A

cutting through meanders to create a straight channel, speeding up the flow of water so that high volumes can pass through an area quickly

39
Q

channel straightening cons

A
  • increases flood risk further downstream
  • lining channels with concrete is unattractive and can damage wildlife habitats
40
Q

What are embankments how do they reduce flood risk

A

an artificially raised river bank allows the channel to hold more water before flooding occurs

41
Q

embankment pros and cons

A

pros - when mud is dredged from the river, it is more sustainable and cheaper + looks natural
cons - when concrete or blocks of stone is looks unnatural
- water speeds up which may increase flooding downstream

42
Q

what is a flood relief channel

A

a man-made river channel constructed to by pass an urban area

43
Q

how doe flood relief channel reduce flood risk

A
  • during times of high flow, gates can open to allow excess water to flow away into the relief channel and reduce flood risk
44
Q

cons of flood relief channel

A

expensive to build
if levels continue to rise, the relief channel may also floo

45
Q

what is soft engineering

A

involves working with natural rivver processes to manageflood risk

46
Q

how does afforestation reduce flood risk

A
  • trees obstruct the flow of water and slow down the transfer to river channels
  • water is soaked up by the tree’s or evaporated from leaves and braches
  • tree planting is cheap and has environmental benefits
47
Q

What is flood plain zoning

A
  • restricts different land uses to certain locations on the floodplain
  • areas close to the river and at risk from flooding can be kept clear of high-value land uses such as housing and industry
  • instead these areas can be used for pasture, parkland or playing fields
48
Q

Pros and cons of floodplain zoning

A

pros - reduces overall losses caused by flood damage
cons - can be difficult to implement on floodplains that have already been developed and can cause land prices to fall

49
Q

What is river restoration and how does it reduce flood risk

A

Uses the natural processes and features of a river, such as meanders and wetlands to slow down river flow and rduce the likelihood of a major flood downstream

50
Q

Three levels of flood warning

A

Flood watch - flooding of low-lying areas and roads is expected, people should be prepared and watch water level
Flood warning - there is a threat to homes and businesses. People should move valuable items upstairs and turn off electricity and water
Severe Flood Warning - extreme danger to life and property is expected.

51
Q

How can people prepare for a flood

A
  • Planning (e.g. moving valuable items upstairs)
  • Using flood gates to prevent floodwater from damaging property
  • Use sandbags to keep floodwater away from buildings
52
Q

Where is Banbury

A
  • located in the Cotswold Hills about 50km north of Oxford
53
Q

Why does Banbury need flood management

A
  • Banbury has a history of devastating floods
  • leading to closure of towns railway station
  • shut local roads and caused £12.5 million of damage
54
Q

In which years did Banbury experience extreme floods (2)

A

1998
2007

55
Q

Aspects of Banbury Flood Defence Scheme (embankment)

A
  • 2.9km earth embankment with a maximum height of 4.5m to create a flood storage area
  • Located mainly on the natural flood plan and collects rainwater that otherwise would have swelled the river and caused it to burst its banks
56
Q

Flow control structures in the Banbury embankment

A
  • specially designed opening controls the rate of flow downstream towards Banbury
  • Any excess water backs up behind the structure, filling up the reservoir rather thancontinuing towards Banbury
  • design avoids the need to open and close flood gates
57
Q

Other aspects of Banbury flood defence scheme

A
  • raising A361 road in flood storage area plus improvements to drainage beneath the road to prevent flooding
  • new earth embankments and flood walls to protest property and businesses such as motorsport business Prodrive
  • new pumping station to transfer excess rainwater into river below the town
  • creation of new Biodiversity Action Plan; a habitat with ponds, trees and hedgerows to absorb and store excess water
58
Q

Social benefits of Banbury

A
  • raised road open during floods to avoid disrupting peoples lives
  • quality of life improved with new footpaths and green areas
  • reduced levels of anxiety through fear of flooding
59
Q

Economic benefits of Banbury

A
  • cost was about £18.5 million
  • But by protecting houses and commercial properties, the benefits are estimated to be over £100 million
60
Q

Environmental costs/benefits of Banbury

A
  • Around 100,000 tonnes of earth required to build embankment
  • Biodiversity Action Plan
  • part of floodplain deliberately allowed to flood if river levels are too high, this causes distruction of habitats

Geography (14 decks)

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