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.
