Flooding Flashcards
What is flooding
A flood occurs when a river has too much water in its channel and it spills onto the surrounding land
Cause of flooding
Rivers usually flood due to a range of physical (natural) factors and causes.
human activity and also cause flooding
Physical causes of flooding
heavy rain fall
# long periods of rain
#snow melt
The steps to flooding
- Heavy rainfalls
- Rains soaks into the ground
- Water quickly reaches the river
- Water runs over the surface
5.River level rises - River floods
Why dose it flood
Usually when it rains,most of the water simply soaks into the ground and there is little chance of flood If however, the water is unable to soak into the ground it will stay on the surface and flow quickly down hill and into the river this is when floods are most common
Human causes of flooding
Deforestation because removing trees reduces the amount of water intercepted by the tree therefore increases run off towards the river
#urbanisation because towns and cities have more impermeable surfaces (doesnât let the water seep through it
What are some human causes of flooding
- Deforestation because removing trees reduces the amount of water intercepted by the tree and therefore increases run-off towards the river
- Urbanisation because towns and cities have more impermeable surfaces (doesnât let the water seep through)
What dose deforestation mean?
Many of the worldâs forests are being cleared to make way for other developments. In some countries the number of Serious floods has more than doubled since large -scale trees clearing began
How to trees help stop flooding
- Leaves act as an umbrella and stop rain from hitting the ground
- Water on the leaves evaporates and doesnât reach the ground
- Roots take up the water and reduce the amount of water reaching the river
- Roots slow down the movement of water in the soil
Negative impacts of flooding.
- Sewage to overflow which can make drinking water contaminated.
- farm animals may drown
- crops can be destroyed (in poor countryâs this may make people starve to death )
-can become electrically charged water in homers which if touched can kill people
Positive impact of flooding
-bring mud/minerals (known as silt) from the river onto the floodplain beside that makes the soil fertile for farming
- can flush pollution out off the land around rivers making it more sustainable.
-The pools/lakes can create a breading area for fish/prawns which are a food source for people.
How can floods be prevented?
- planting trees in the river basin The trees act as a break on rainfall and reduce the amount of rain reaching the ground. Trees absorb water as they grow. This is afforestation.
- river channels are made larger by dredging so that they can hold more water.
- walls called embankments are built to increase the light of river channel
-flood relief (by-pass) channels can be built around townsthey divert excess water out of rivers und reduce the risk of flooding.