river discharge and flooding P1

• In the context of rivers, what is discharge?

  The volume of river water flowing per second
• What unit is river discharge typically measured in?

  Cumecs
• What does a hydrograph illustrate?

  River discharge over a period of time
• What is the peak discharge on a hydrograph?

  The highest discharge in the period
• What does lag time represent on a hydrograph?

  Delay between peak rainfall and peak discharge
• What does the rising limb of a hydrograph indicate?

  Increase in discharge as rainwater flows in
• What does the falling limb of a hydrograph represent?

  Decrease in river discharge to normal
• How does heavy rainfall contribute to increased flood risk?

  Water arrives too quickly to infiltrate
• Why do clay soils increase flood risk?

  They are impermeable, increasing runoff
• What type of rock is Granite?

  Impermeable
• What type of rock is shale?

  Impermeable
• How does prolonged rainfall contribute to flood risk?

  It saturates the soil, increasing runoff
• How does steep relief affect water flow to a river channel?

  Water reaches the channel much quicker
• How do buildings made from impermeable materials affect flood risk?

  They increase surface runoff of water
• How do trees reduce flood risk?

  They intercept rainwater and evaporate it
• How does deforestation impact flood risk?

  It leads to more flooding
• What are physical factors affecting flood risk?

  • Heavy rainfall
  • Geology (impermeable)
  • Prolonged rainfall
  • Relief (steep-sided valley)
• What are human factors affecting flood risk?

  • Land use (impermeable buildings)
  • Deforestation