Why places are more at risk from flooding

• Low-lying areas

  Low-lying areas are more prone to river and groundwater flooding, due to the ground becoming saturated after heavy rainfall.
• Urbanised areas

  Urbanised areas have increased areas of impermeable surfaces and so become more at risk of surface water flooding. Water is unable to infiltrate soil so it flows overland.
• Small drainage basins

  Small basins, especially in semi-arid or arid areas, are subject to flash flooding due to short lag times. Infiltration of semi-permeable sloped surfaces is limited allowing surface overland flow to develop rapidly.