Enquiry Question 5 Flashcards
How does warmer air temperature affect the flood risk?
Warm air holds more water vapour
Atmospheric moisture storage capacity has risen by 7%
How does the jet stream affect flood risk?
The change in atmospheric pressure has caused more areas of low depression so more storms form.
Example of flood risk getting higher
What in the 1960-70 may have been a 1 in 125 day event is now a 1 in 85 day event.
Storms like storm Desmond are now 40% more likely
Flood defences
Defences are costly and are only used to protect valuable areas
Even then not many flood defences can prevent flood against major storm events
The budget for flood defences has been reduced
Destroying upper course wetlands/bogs
Wetlands and bogs hold water
When destroyed water released and floods are more likely
Building on flood plains
4 million properties on flood plain with 1 in 1000 risk of flooding each year
Building in these areas has grown at a rate of 1.2% a year since 2011
More impermeable surfaces
Removing meanders
Water moves quicker down river
Water cannot be stored for long
Lag time reduced
Flood walls
Building a high wall alongside river to increase capacity
Can increase flood risk downstream
Fairly cheap
Levees or embankments
Like flood walls but normally built at distance from river
Up to £1 million
Can increase flood risk downstream
Flood barrier
Building gates and walls across the river, controlling movement of water
Thames barrier cost £1.6 billion and £6 million per year
Rising sea levels mean Thames barrier won’t work after 2030
Flood plain retention
Level of flood plains lowered and surfaces restored to grass or shrubbery
Vegetation retains water
£1.2 million for 2km
River channel restoration
Meander rebuilt slowing water
Banks lowered to make river flood areas such as parks instead of town
£1.2 million for 2km
