Flocding Flashcards
What is flooding
When a water extends past its normal limits.e.g. When a river breaks its banks
What two types of factors cause floods
Physical factors(natural)
Human Factors(man-made)
What are flash floods
Floods that are so sudden we get no warning and people can get trapped and even drown.Bursts of heavy rainfall tend to cause then
What can floods be caused by
Often heavy rainfall =causing water to run over the surface quickly and back to the river
Or melting snow and ice
What does the river do once the channel is full
It bursts its banks
Less infiltration =
More surface runoff
More surface runoff=
Water reaches river more quickly
What are some physical factors of a flood(refer to case study)
Heavy rain(200ml in 4hrs)
Impermeable rock(leads to more surface runoff)
Soggy soil(previous saturated soil)
Steep slopes(Drainage basin sloppy)
Tributaries
Flat flood plains(these flood naturally)
Strong coastal winds
What human factors cause floods(refer to case study)
Built up areas more impermeable surfaces(in a town on a floodplain)
Deforestation,trees intercept rainfall and slow its movement down reducing flooding risks.Cutting down trees leads to more likely to flood(trees had been cut in the valley/bridges in town,100m Calvert)
What were the effects of flooding
Tourism=tourists went home and season was cut short
Rivers=contamination by sewage
Property=over 50 cars washed out to sea
Businesses=many lost stock and were closed for 6-9months
Costs=repairs were estimated at over £500 million
Buildings=3 properties destroyed,80 damaged
Roads and car parks were damaged
Harbour area severely damaged
Effects of flooding are
Long term and short term
What do flood management schemes do
Aim to prevent flooding or reduce it to a poiny
What is a flaw with flood schemes
They can have negative effects
What are hard ways to reduce flooding
Build a dam
Widen river
Deepen river
Add embankments or levees
Straighten the river
Concrete banks
What are soft ways to stop flooding
Plant trees
Controlled flooding
What does a dam do
Advantages:
A dam traps the water and stores it in a reservoir.That water can then be released slowly in a controlled way.
Dams also generate electricity when water turns as it passes through the dam.This is called hydro-electric power
Disadvantages:
Dams are very expensive and land around it I’d flooded by the reservoir
What does widening the river do
By digging out larger channel.however this means wildlife loses habitats as work is carried out
How does deepening the river work
By digging out the channel.However this means wildlife loses habitats as work is carried out
What does adding embankments or levees do
If you build the river banks it can hold more water,however they have to be maintained and if they break flooding can be worse
How does straightening the river work
This speeds the flow of water to the sea up
Concrete banks
Smoother than natural banks therefore water moves more quickly to the ses
How does plating trees help
If you plant trees in a drainage basin they will intercept rain and absorb water reaching the river and slows down the movement of water to the river
However planting trees need land that is normally used for farming.Trees also take many years to reach maturity especially deciduous trees which intercept the most of water
What does controlled flooding do
Allows designated areas to flood.This means excess water has somewhere to go as planners identify Whig areas of land to flood.This protects other areas downstream such as town and cities
