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Flashcards in Physical Landscape Deck (55):

Definition of solution

Materials dissolved in water


Definition of suspension

Sand suspended in water


Definition of Traction

Rolling boulders


Definition of saltation

Bouncing pebbles


Definition of freeze-thaw weathering

Water enters a crack, freezes and expands by 10%, when it thaws, more water can enter the crack and so the process continues.


Definition of abrasion

Process where Sand/pebbles in waves rub against the coastline and smooth the surface


Definition of hydraulic action

Waves trap air in cracks in rocks, compressing the air and causing cavitation which expands the crack


Definition of corrasion

Large boulders thrown against the cliff face by the waves


Definition of carbonation

Acids in water dissolved minerals in the rock


How do waves form

Friction from wind blowing over the sea causing ripples that develop into waves


Definition of fetch

It is the distance that wave-generating winds blow across the open water


Why do waves break

As the gradient of the seafloor increases, friction slows the bottom of the wave which causes the crest of the wave to move faster and rise up

(Friction with seabed distorts circular motion, increasingly elliptical orbit as water becomes shallower)


Definition of mass movement

Downward movement or sliding of minerals under the influence of gravity


Key characteristics of constructive waves

Wave crests are far apart
Gently sloping front
Strong swash


Key characteristics of destructive waves

Waves are close together
Steep front
Strong backwash


What is a seawall

- they are at the foot of cliffs/top of beach
- high maintenance
- £10 million per km
- 3-5 metres high


What are groynes

- prevents sediment from being moved down the beach by long-shore drift
- £5000 per metre
- causes higher erosion elsewhere downdrift


What are Rock armour

- rocks against the cliff which forces waves to break therefore absorbing the waves energy
- rocks are expensive to transport
- £1000-£4000 per metre
- obtrusive


What are gabions

- Metal cages filled with rocks
- unattractive
- easy to maintain and last long
- £2000 per metre


What is beach nourishment

- where they build up a beach with sediment from nearby so it blends in
- £3000 per metre
- needs constant maintenance


Dune regeneration

- it is where marram Grass is planted because Dunes are effective buffers for waves and then fenced off so they can grow
- £20 per metre


What is Marsh creation

- allowing low-lying coastal areas to be flooded
- creates habitats
- compensation is given for land so can be expensive


Definition of a drainage basin

An area of land drained by a river and its tributaries


Definition of the source

The start of a river


Definition of the mouth

The end of the river, usually where a river joins the sea


Definition of a tributary

A small stream that joins a larger river


Definition of a confluence

Where a tributary joins a larger river


Definition of a watershed

It is a drainage basin and all the water in the area drains into one body of water


What is a floodplain

They are wide, flat areas on either side of the river in its middle and lower course. They are created by migrating meanders and floods depositing layers of silt to form alluvium


Definition of discharge

Quantity of water that passes a given point in a stream or river bank within a given period of time, measured in cumecs


Characteristics of the upper course

- steep, narrow valleys called V shaped Valleys
- narrow, shallow river, looks fast flowing as areas of rapids
- interlocking spurs


Characteristics of the middle course

- wider valleys
- decreased gradient of landscape
- meanders, oxbow lake, pools and riffles


Characteristics of the lower course

- Side of the valley is called the bluff
- flooding occurs across this valley leaving 'alluvium' on valley floor
- levees, estuary, delta


Formation of a waterfall and gorge

- occur when the river flows over resistant rock and then less resistant rock
- see diagram


What is LAG

The time between water landing on the Earth surface and entering a River channel


Causes of flooding both physical and human

- precipitation
- rapid thawing
- silting of river channel (shallower)

- urbanisation (impermeable surfaces)
- deforestation (reduces interception)


Hard engineering for managing floods

Channel straightening
Flood relief channels


Soft engineering for managing floods

Wetlands (flood storage)
Floodplain zoning
River restoration


Preparing for floods

Monitoring (satellites), environment agency warnings, individual planning (sandbags).


Outline datchet objections to the Jubilee flood management scheme

- public expense (moving railway and M4)
- cheaper solutions
- it will allow more floodplain development and could become stagnant and mosquito infested
- increased flood risk to Datchet and Staines
- noise and distruption (construction)


Facts about Jubilee food management scheme

- cost environmental agency £110 m.
- first used in January 2003 but some banks failed at only 60% full, costing £3.5 m to repair.
- environment agency said that it protected 400 properties from flooding and disruption was prevented to a further 1000.
- villages east of the confluence e.g. Datchet, were flooded - some residents believe they were worse off.


What facts are there for building the Jubilee flood management scheme

- Thames flooding has return periods
Normal cumecs = 60
Every 4-6 years = 350
Every 60 years = >500
Every 100 years = >600
- A flood is scheduled soon

-more people now live on the flood plain
-climate change may make floods more frequent/worse
-River could be a nature reserve and recreation facility


Evidence for worse conditions in Datchet

- 2 river channels means it flows faster through the area than if it flooded before Datchet
- between Thames and Jubilee river there is agricultural land which is being protected instead of residential land


How did the Jubilee scheme work in 2003

- 144 cumecs flowed in Jubilee river only 60% of designed capacity (full = 215 cumecs)
- allowed Thames to be 260 cumecs instead of 404 cumecs


Does the Jubilee river have enough capacity

- many are unconvinced

• 2014, with Jubilee river, Thames still flooded
• claims to hold 285 cumecs but was damaged at 144


Concluding comments on the Jubilee river

2014 showed the area will still flood but Jubilee clearly limited impacts on Maidenhead, Eton and Windsor. However Datchet suffered on a greater scale so will need flood protection.


Banbury flood management reasons why

• 1998 - cost £12.5m , 150 homes and businesses affected
• 2007 - even more properties affected


Management strategies 2017 Banbury

• embankment - 2.9 km long, height of 4.5m
• Raising A361 - improves drainage
• embankments and flood walls - built around Prodrive
• Pumping station - pumps excess water into channel
• biodiversity- New habitats (ponds, hedgerows, trees) to absorb and store excess water. Reservoir (100,000 tons of earth was extracted)


Economic evidence for evaluation of success Banbury

- costs £18.5m
- protects 441 homes and 73 businesses worth £100m


Social evidence for evaluation of success in Banbury

- Raising A361 ensures access routes during flooding
- Quality of life improved e.g. Footpaths


Environmental evidence for evaluation of success in Banbury

- new reservoir and habitats
- biodiversity action plan has created new ponds, trees and hedgerows


Explanation of how river processes changed for Banbury

Encouraging flooding north of Banbury and recovering flow of river through the sluice gates of the embankments reduces river energy and encourages deposition which leads to silting of the channel, reducing the channel capacity and causing more flooding.
Regular dredging is needed to address this.


Factors affecting rate of erosion

- energy of waves
- size and shape
- resistance of the coastline
- gradient of sea floor


Example of Mass movement

Rotational slip:

- impermeable under permeable rock
- water saturates permeable
- slips in a rotational manner


How are levees formed

When deposition raises the riverbed so the channel cannot carry as much water, so during flooding, the water flows over the side of the channel and deposits on the banks raising the height of the levees