Prolonged Rainfall and Heavy Rainfall are the Main Cause of Flooding
Flooding occurs when the discharge of a river is so high that the river spills over its banks onto the flood plain.
A major cause of flooding is prolonged rainfall. After a long period of rainfall the ground becomes saturated which increases surface runoff > increasing the discharge from the river.
Heavy rainfall can lead to rapid surface runoff. If the rainfall is to intense for the surface to handle and absorb then this can increase the river discharge = flash floods.
Melting snow & ice leads to an increase in a rivers discharge.
Physical Factors that Increase the Risk of Flooding:
- Sparce Vegetation - little rainfall can be intercepted = more rain reaches the ground. Increases the amount of water that reaches the river = increase in the river discharge.
- Impermeable ground - if the ground has been baked hard…