Causes of Flooding

• How does heavy rainfall cause flooding?

  • When there is intense or prolonged rainfall, the ground becomes saturated.
  • This reduces infiltration, so more water flows as surface runoff into rivers, increasing flood risk
• How does geology cause flooding?

  • If the ground is made of impermeable rock (like granite), water can't soak in.
  • This increases surface runoff and causes rivers to fill up quickly and flood.
• How does steep relief cause flooding?

  • Water flows faster down steep slopes, so it doesn’t have time to soak into the ground.
  • This leads to more runoff and quicker river flooding
• Name the physical causes of flooding:

  • Geology (rock type)
  • Rainfall/precipitation
  • Relief of land
• Name the human causes of flooding:

  • Deforestation
  • Urbanisation
  • Agriculture
• How does urbanisation cause flooding?

  • Roads and buildings are impermeable, so rainwater can’t soak into the ground.
  • Instead, it flows quickly into drains and rivers, increasing flood risk.
• How does deforestation cause flooding?

  • Trees normally absorb water and slow runoff.
  • Without them, more rainwater flows straight into rivers, making flooding more likely.
• How does agriculture cause flooding?

  • Ploughing and overgrazing compact the soil, reducing infiltration.
  • This increases surface runoff into rivers, which can then flood.