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Geography > Rivers > Flashcards

Rivers Flashcards

0
Q

River regime

A

The variablility of a rivers discharge over the course of a year

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1
Q

Discharge

A

The amount of water passing a certain point over a period of time

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2
Q

Storm hydrograph

A

Shows the change in a rivers discharge caused by a period of rain

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3
Q

How do floods occur

A

Floods occur when discharge exceeds channel capacity

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4
Q

Boscastle 17th August 2004

Brief summary

A

Rivers Valency, Jordan & Paradise feed into Boscastle
Boscastle built on flood plain
1 months rain in 24 hours
3 million tonnes of water fell onto 40 square kilometre drainage basin
Few trees on side of the valley
Tourist season

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5
Q

Flood management

A

Reduce lag time and peak discharge
Increase channel capacity
Improve channel efficiency

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6
Q

Hard engineering solutions

A 
Dredging
Channel widening/straightening
Levees/embankments
Dams
Outflow storage
Flood walls
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7
Q

Soft engineering solutions

A 
Afforestation
Floodplain zoning
Flood warnings
Protection
River restoration
Wetland & river bank conservation
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8
Q

Natural causes of flooding in Bangsladesh

A

Onshore winds
In the path of tropical cyclones
Vast drainage basin
Low lying relief

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9
Q

Human causes of flooding in Bangladesh

A

Population pressure
Urbanisation
Global warming

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10
Q

Impacts of flooding in Bangladesh (1998)

A

670,000 ha of farmland was destroyed
1000+ human deaths
30,000,000 people made homeless

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11
Q

Dhaka

A

Capital of Bangladesh
Population of 17,000,000 and growing by 1,500,000 each year
10,000,000 people live in the slums

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12
Q

Cherrapunji

A

Total annual rainfall is 10980 mm

Total rainfall for May to August is 7560 mm

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13
Q

The LA river, Calfornia

A

Source in the Simi Hills and Santa Susana Mountains
48 miles long
Managed almost the entire length
Only 2% of water reaches the sea

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14
Q

Management strategies on the LA river

A

Sediment/debris dam
Flood control basin (dam)
Spreading grounds over permeable rocks
Much of the channel has been straightened and lined with concrete

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15
Q

3 main types of weathering

A

Physical
Chemical
Biological

16
Q

Types of physical weathering

A

Freeze thaw
Pressure release
Insolation/exfoliation

17
Q

Types of chemical weathering

A

Salt crystal growth
Hydration
Oxidation
Carbonisation

18
Q

Types of biological weathering

A

Plants

Animals

21
Q

Mass movement

A

The downward slope movement of earth material
Moves under the influence of gravity
Larger particles need steeper slopes for the effect of gravity to effect the weight of the material

22
Q

Erosion processes

A 
Hydraulic action
Abrasion
Attrition
Corrosion
Cavitation
23
Q

Landforms of river erosion

A

Interlocking spurs
Rapids & waterfalls
Evorsion hollows/potholes
V-shaped valleys

24
Q

Bernoulli effect

A

Traction (rolling)
Saltation (bouncing)
Suspension (floating)
Solution (dissolved)

25
Q

Fluvial processes

A

Erosion
Transportation
Deposition

26
Q

Deposition

A

Larger particles are deposited first as more energy is needed to carry them
Hjulström curve

27
Q

Causes/theories for the formation of meanders

A

Obstruction

Pools & riffles

28
Q

Deltas

A

Large areas of sediment found at the mouth of many large rivers

29
Q

Positive feedback effect

A 
Sediment supply
Bar formation
Flow diverted to channel bank
Rapid bank erosion
Repeat
30
Q

Eustatic change (eustacy)

A

Global change in sea level

31
Q

Isostatic change (isostsacy)

A

Change in height of land (isostatic recovery)

32
Q

Paired terracing causes

A

Climate change
Tectonic uplift
Isostatic recovery/eustatic change

33
Q

Unpaired terracing causes

A

Meander migration

34
Q

Entrenched meanders

A

Rapid erosion taking place

No time to migrate across, cut straight down

35
Q

Ingrown meanders

A

Slow erosion takes place

37
Q

Endogenetic (internal) factors influencing the weathering of the rock

A

Presence of certain minerals
Rock texture
Presence of joints and bedding plains

38
Q

Exogenetic (external) factors influencing the weathering of the rock

A

Climate and vegetation
Organic acid contained within plants
Presence of water
Atmospheric and soil temperature (2-3 X after per 10 degree temp rise)

39
Q

Mekong river

A

One of the world’s richest freshwater fishing grounds

2.6million tonnes of fish a year

Geography (4 decks)

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