Topic Summaries

Factors affecting flood risk

IGCSE > Geography > CIE > IGCSE Geography Topic Summaries > Management strategies for floods > Factors affecting flood risk
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Weather hazards and atmospheric circulation

Tropical storm hazards

Responding to tropical storms

Hot desert ecosystems

Cold environment ecosystems

Glacial landscapes

Glacial landform processes

Water supply

Energy supply

  • Physical factors: 
    • Heavy precipitation: exceeds infiltration capacity, causing surface runoff. 
    • Prolonged precipitation: saturates the soil, reducing infiltration and increasing runoff. 
    • Sudden snowmelt or storms: can cause flash flooding 
    • Geology: impermeable rocks (e.g. granite or clay) prevent infiltration and increase runoff, while permeable rocks (e.g. sandstone or chalk) allow water to soak in, reducing flood risk. 
    • Steep slopes: cause water to flow rapidly downhill reducing infiltration time and increasing flood risk. 
    • Vegetation: dense flora increases interception and transpiration, reducing runoff, whereas sparse or absent vegetation leads to erosion and faster surface flow.
  • Human factors: 
    • Land use: bare soil from agriculture or deforestation transfers water quickly, and ploughing slopes create tunnels (streams downhill).
    • Urbanisation: lack of vegetation and impermeable surfaces (e.g. concrete, tarmac) results in overland flow and little absorption.
    • River management: channel straightening, levees, embankments, dams, and reservoirs can all help manage or divert flood risks.
    • Climate change: leads to more frequent and intense storms, increasing rainfall and wetter seasons, increasing the likelihood of floods.

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