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River environments
Weat hering

- Three types: physical (breaking down of rock - Slumping: river flows at base of valley-side
smaller pieces), biological (roots of plants slope. Slope = unstable. Heavy rain material
growing in cracks and splitting rocks apart), saturated heavier + lubricated slumping
chemical (decaying, disintegration, mostly by…

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- Deposition: laying down of load due to decreased energy, speed and discharge (usually when
river enters sea, gradient decreases or during drought). Heaviest load deposited first
- Erosion: wearing away of rock/stones/soil by river/wind/rain/ice

The higher the velocity, the more particles are eroded and the less particles are deposited.…

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- Formed in fast-moving streams littered with large, hard rock formations water goes from a
hard rock resisting erosion (more resistant) to a soft rock that's easier to erode (less
resistant) softer rocks erode harder rocks left as incomplete barriers (too small to form
waterfall though) water rushes around rocks,…

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Water
Definitions
- Supply: taking water from lakes/rivers/groundwater to meet demand. Most of the world's
water supply is from ice sheets (77%). Only 3% of the world's supply is freshwater
- Demand/consumption: the need for water
- Water balance: comparison between supply and demand of water in an area

Supplies…

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How supply issues are being addressed
- Maximum use of aquifers in South East
- Reservoir construction in North and West (e.g. Lake Vyrnwy- Wales, Lake Kielder- England)
- Water from reservoirs is transferred to main areas of water deficit

How water demand is controlled during times of extreme shortage…

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Factors affecting water quality
Agriculture Global pattern of access to safe water
- Liquid from silage and animal slurry LICs tend to have low percentage of people
- Fertilisers/pesticides in groundwater with access to safe water (e.g. Madagascar;
- Deforestation more run off more soil/ countries in Africa, Asia and…

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The Three Gorges Dam- Yangtze River
- REDUCE PROBLEMS caused by FLOODS (protects
When? 10 million people- but no one upstream)- 1931
- Approved in APRIL 1992 FLOOD KILLED >3 MILLION
- Reservoir began to be filled around 10 years - Improved TRANSPORT (boats from Chongqing
later Shanghai through reservoir.…

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Physical Impact Effect on hydrograph
factors

Weather Rainfall exceeding ground's infiltration Heavier rain/ frozen soil shorter lag
capacity, prolonged rainfall saturated time, higher peak discharge
ground, slow snow melt, frozen ground Snow longer lag time, lower peak
run off reaches river faster discharge as snow takes long time to melt…

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Consequences

Short term Long term

Disruption of transport/communications Polluted/stagnant floodwater disease from
dirty water

Insurance claims Need for aid


Flood cont rol
Hard engineering
= structures which hold back/safely dispose of floodwaters (e.g. Dams, flood embankments,
sluice gates, relief channels)

Soft engineering
= flood control schemes- working with nature to…

Page 10

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Flood De fence Scheme- T he T hames Barrier
Why?
- London is prone to TIDAL (e.g. Storm surges, tidal surges from North Sea) and FLUVIAL floods
- In 1953, major FLOOD caused 307 DEATHS and £50 MILLION of DAMAGE
- PREVIOUS SOLUTION had been to keep building HIGHER and…

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