We maintain our sewer system to ensure it has sufficient capacity to cope with wet weather.
However there is a limit to how much additional capacity we can build to maintain its effectiveness.
As this means flooding can occur during extreme rainfall, we use a measure to identify the percentage of the population at risk of sewer flooding in a 1-in-50 year storm (equivalent to a 2% chance each year).
Unit of measurement
Current performance (17/18)
% of population at risk