A Flood Alert was issued for Upper River Colne and Radlett Brook in Hertfordshire on 12th March 2026. Affected watercourses included the River Colne.
During this event, FloodRadar monitoring gauges recorded notable rises. The River Colne at Farlows Bridge rose 0.24m, peaking at 0.81m, while the River Colne at Watford climbed 0.21m.
Environment Agency advice issued
Rising river levels throughout the evening may lead to flooding. Flooding is possible from overnight on 12 March 2026 to the following morning. Locations most affected will be low lying land and roads near rivers. We are closely monitoring the situation . Take care and avoid walking, cycling or driving through flood water and consider activating any flood protection products you may have This message will be updated by 10:00AM on 13 March 2026 or as the situation changes.
Monitoring gauges during this event
| Station | River | Rise | Peak |
|---|---|---|---|
| Farlows Bridge | River Colne | +0.24m | 0.81m |
| Watford | River Colne | +0.21m | -0.13m |
| London Colney | River Colne | +0.16m | 1.42m |
| Thorney Mill Road, West Drayton (Temporary) | River Colne | +0.15m | 0.30m |
| Willowbank | River Colne | +0.14m | 0.59m |
| Iver, Clisbys Bridge | River Colne | +0.09m | 0.62m |
| Denham Colne | River Colne | +0.06m | 0.30m |
| Moor Lane | River Colne | +0.06m | 7.57m |