What is a storm overflow?
A storm overflow is an outlet from the sewer system. Its monitor records when the overflow operates. That record is one part of the evidence about the water nearby.
What to do
Use the map to find the outlet record, then check its year, monitor coverage and latest report time. The monitor shows operation. It does not measure sewage volume or water quality.
What the map can show
Use a location page to check the operator, receiving water, permit reference and annual return. The current panel shows the latest monitor report we hold. Its date is separate from the year of the annual figures.
What the monitor does not measure
Event duration monitoring records operation and time. These records do not provide a sewage volume or a bacteria test. A long event and a short event can have different flows, so hours cannot be converted into litres from this data.
Keep the reporting year in view
Compare records for the same year and check monitor coverage. A missing value means the source did not provide a usable value. It is not a zero. Read the source notes where a return has been corrected.