Flooding

Causes of flooding: physical

Prolonged rainfall:

After long period of rain, soil becomes saturated so more rain can't infiltrate. This increases runoff which icreases dicharge quickly, which can cause a flood.

Snowmelt:

When lots of snow/ice melts, lots of water enters a river in a short period of time. This increases discharge quickly, which could cause flood.

Heavy rainfall:

Means there is lots of runoff. Discharge increases quickly, which can cause flood.

Relief:

Steep-sided valley = water reaches river more quickly. Increases discharge quickly. And vice versa

Causes of flooding: human

Deforestation:

Trees intercept rain water on leaves, which then evaporates. Trees also absorb water through roots and store it. Cutting down trees increases vol. of water that reaches river, which increases discharge and makes flooding more likely.

Building/construction:

Building often made from impermeable materials & surrounded by roads. Icreases runoff & discharge quickly.

River flooding in UK is happening more, especially over last 20 years.

Flooding case studies: Carlisle & Bangladesh

Causes:

• Heavy rainfall: 200mm fell in 36 hours. Soil became saturated, increased…