Rivers and flooding
Learn about rivers and flooding including the physical and human causes of flooding as well as common prevention measures.
This lesson includes:
one video explaining river flooding and its causes
an introduction to hydrographs and how they are used to show how and when a rainfall event affects the discharge of a river
one flooding case study video
Watch this short film to find out about river flooding and its causes.
A river floods when the water normally flowing in the channel overflows its banks and spreads out onto the surrounding land.
This causes major problems for people living close to the river.
Why do rivers flood?
A variety of factors can increase the likelihood of flooding.
Physical causes of flooding:
- heavy rainfall
- long periods of rain
- steep slopes
- impermeable rock (doesn't allow water through)
- very wet, saturated soils
- compacted (when something is closely packed together) or dry soil
Human factors increasing flood risk:
- urbanisation (growth in the urban population), because towns and cities have more impermeable surfaces
- deforestation (the cutting down of trees), because removing trees reduces the amount of water intercepted (to interrupt the movement) and increases run-off (when rainwater flows over the surface of the land)
A storm hydrograph is a graph to show how and when a rainfall event affects the discharge of a river.
The amount and intensity of the rainfall is not the only factor influencing the shape of the hydrograph.
There are other influences:
Watch this short film with Liz Bonnin to find out about the 2014 floods in Somerset.
Here are a few activities to try to help you remember what you've learnt about rivers and flooding.
Exploring case studies
Read the following two flooding case studies:
- the main causes of the floods
- the main short term and long term responses
What are the similarities and differences between the causes and responses? Why do you think they differ?
There's more to learn
Have a look at these other resources around the BBC and the web.