We have only been collating detailed flood messages since May 2017.
Each Flood Alert may have multiple updates. The messages listed below may therefore be greater than the number of alerts detailed in the Flood Alert table above.
Flood Alert issued on 4 Oct 2021 20:11
This flood alert is being issued based on the forecast heavy rainfall we are expecting overnight on Monday 4 October into Tuesday. This is likely to cause the river to rise.
The main area of concern is currently Warrengate including South Mimms, Potters Bar, Brookmans Park and Welham Green.
There is likely to be flooding to low lying land and roads close to the river on Monday night. Flooding from surface water, where water gathers and flows off road surfaces, could also occur.
We expect the river to rise and then remain high overnight. Further showers are then forecast on Tuesday.
We have staff attending site who will be closing the Warrengate Road flood gates. We are also constantly monitoring river levels and have staff on standby to attend to any blockages in the river.
This message will be updated on Tuesday morning or earlier if the situation changes.