River Landscapes and Processes- Flooding Flashcards

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1
Q

Flash floods

A

Floods that happen without warning

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2
Q

5 physical causes of flooding

A

Prolonged rainfall, heavy rainfall, snow melting, rocks, relief

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3
Q

Prolonged rainfall causing flooding?

A

Long period of rain, soil saturated, more runoff, increases discharge quickly

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4
Q

Relief causing flooding?

A

Steep valleys, water reaches the channel quickly, increases discharge quickly

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5
Q

Heavy rainfall causing flooding?

A

Increase in surface runoff, increase discharge

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6
Q

Snowmelt causing flooding?

A

Lots of snow melt, lots of water in river quickly, increases discharge quickly

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7
Q

Rocks causing river floods?

A

Impermeable rocks, no percolation, more runoff, increases discharge

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8
Q

5 Human causes of flooding

A

Urbanisation, agriculture, industry, deforestation, drainage systems

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9
Q

Urbanisation causing flooding?

A

Change in land use, impermeable materials, no infiltration, more runoff, increase discharge quickly

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10
Q

Agriculture causing flooding?

A

More farming, less vegetation, less interception, more runoff, increases discharge quickly

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11
Q

Industry causing flooding?

A

Factories at river mouth
Impermeable surfaces, more run off, risk of flooding
Deepen river for boats, increase capacity, less floods

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12
Q

Deforestation causing flooding?

A

Trees removed for industry, urbanisation etc, less interception, increases discharge quickly

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13
Q

Drainage systems causing flooding?

A

Water flowing straight to river, increased discharge, more risk of floods

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14
Q

2 Social effects of flooding

A

Loss of life due to drowning
Damage to houses and belongings

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15
Q

2 Environmental effects of flooding

A

Shortage of food from flooded farmland
Contamination of fresh water supplies

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16
Q

2 Economical effects of flooding

A

Communication links can be destroyed
Disruption to gas and electricity supplies

17
Q

4 Types of hard engineering for rivers

A

Dams, levees, channelisation, flood relief channels

18
Q

Dams/reservoirs
Def, ad, dis

A

Barriers to hold back water in artificial lakes
Ad- long lasting, produce hydro-electric power
Dis- expensive, can ruin the environment

19
Q

Embankments/levees
Def, ad, dis

A

High banks built on or near riverbanks
Ad- stops water spreading, can be natural, blend in
Dis- water could go over and be trapped, can burst

20
Q

Channelisation
Def, ad, dis

A

Deepening or straightening a river
Ad- water flows away quicker from places at risk
Dis- can put other places at risk, looks unnatural

21
Q

Flood relief channels
Def, ad, dis

A

Extra channels built leading from rivers
Ad- accommodates high flows, prevents overflow of banks
Dis- can be unsightly, expensive

22
Q

3 Types of soft engineering for rivers

A

Floodplain zoning, wash lands, river restoration

23
Q

Floodplain zoning
Def, ad, dis

A

Governments use areas differently based on flood risk
Ad- prevents new housing floods, leisure spaces in high risk areas
Dis- floodplains good for building,no demand for leisure spaces

24
Q

Wash lands
Def, ad, dis

A

Areas on the flood plain being allowed to flood
Ad- safe place for water to go, improves natural river processes
Dis- limit use of land, change in land use

25
Q

River restoration
Def, ad, dis

A

Restoring a river to it’s original course
Ad- can slow down river through meanders, create natural habitats
Dis- flood banks can still be needed, require change in land

26
Q

Hydrograph?
Flood hydrograph?

A

A record of river discharge over a period of time
Shows the change in discharge caused by a period of rainfall

27
Q

River discharge calculation

A

Cross sectional area x river’s mean velocity

28
Q

Rising limb?
Peak flow?
Recession limb?
Lag time?

A

Increase of flood water in a river
Highest amount of discharge in a river
Decrease of flood water in a river
Difference between peak rainfall and peak discharge

29
Q

5 factors affecting storm hydrographs

A

Area, soil, rain intensity, urbanisation, afforestation

30
Q

How does area affect storm hydrographs?

A

Large basins receive more precipitation, more runoff, increases lag time

31
Q

How does soil affect storm hydrographs?

A

Thick soil, more infiltration (sand), increases lag time

32
Q

How does rain intensity affect storm hydrographs?

A

Intense rainfall, more runoff, steep rising limb, decreases lag time

33
Q

How does urbanisation affect storm hydrographs?

A

More impermeable surfaces, steep rising limb, decreases lag time

34
Q

How does afforestation affect storm hydrographs?

A

More interception, shallow rising limb, increases lag time