Flooding Flashcards
What is flooding
Flooding occurs when a river has too much water in its channel and it spills onto the surrounding land
What are some physical causes of flooding
Heavy rainfall
Long periods of rain
Snowmelt
What are some human causes of flooding?
Deforestation
Urbanisation
What is deforestation
Removing trees reduces the amount of water intercepted by the tree and therefore increases run off towards the river
(Cutting down trees)
What is urbanisation
Towns and cities have more impermeable surfaces ( doesn’t let any water through) this means the water just sits on the top and builds up to become a flood.
Rain falling on concrete and tarmac is unable to soak into the ground.
Gutters and drains then carry the water quickly and directly to the river.
What are the 6 steps of flooding from heavy rainfall
- Heavy rainfall
- Rain soaks into ground
- Water quickly reaches river
- Water runs over the surface
- River level rises
- River floods
How are floods most commonly made
If the water is unable to soak into the ground it stays in the surface , then it flows quickly downhill into a river
What do roots on a tree help with
They take up water to reduce the amount reaching the river
They slow down the movement of the water
What do the leaves of a tree help with
They act as an umbrella to stop the rain from hitting the ground.
The water on the leaves evaporates and doesn’t reach the ground
Where is somewhere that had a flood?
Biescas in northern Spain
What is a famous river?
The Amazon river
What can happen if a house is flooded? (Effects of flooding)
Furniture can be destroyed and expensive to replace.
Insurance may be expensive to get in the future
What can happen if a farm is flooded? (Effects of flooding)
Farm animals may drown
Crops can be destroyed. In poor countries this means people starve.
What can happen if roads are flooded? (Effects of flooding)
Sewage systems may overflow. Causing drinking water to become contaminated.
Travel and transport can be disrupted as roads are under water or badly damaged.
Is this positive or negative?
Flood waters bring mud/minerals (known as silt) from the river onto the floodplain and that makes the soil fertile for farming.
Positive
Is this positive or negative?
Flooding can flush out pollution from the land around the rivers and make the land more useable.
Positive
Is this positive or negative?
The pools/lakes created by a flood provide breeding areas for fish/prawns which are a food source for people
Positive
What is a SOFT way to prevent floods?
Planting trees in the river basin. The trees act as a break on rainfall and reduce the amount of rain reaching the ground. Trees also use up water as they grow.
What is another name for planting trees?
Afforestation
What are some HARD ways to prevent floods?
Make the river channel larger and deeper to hold more water.
Walls called flood embankments are built to increase the height of the river channel.
Flood relief channels can be built around towns to divert excess water out of rivers and reduce the risk of flooding.
What is hard engineering?
A techniques used to prevent erosion and flooding. They are highly visible man made structures used to stop or disrupt natural processes.
They usually have a negative impact on the environment
What is soft engineering?
It works with nature to protect rather than trying to stop natural processes. It uses ecological principles ( like planting trees) .
It has a less negative impact on the environment
It’s less expensive
What is an example of hard engineering
Dredging
Using a digger to make the river channel deeper and larger
What is an example of soft engineering?
Planting trees
