Sewer flooding happens when sewers are overwhelmed by heavy rainfall or when they become blocked. The chance of flooding depends on the capacity of the local sewerage system and the amount of rain that falls. Land and property can be flooded with water contaminated with raw sewage as a result. Rivers can also be polluted by sewers that overflow.
The water and sewerage companies are responsible for managing the risks of flooding from their surface water and foul or combined sewer systems. They do this by investing in their sewer systems to minimise the risk to communities. Highways authorities provide and manage highway drainage and roadside ditches.