River Thames Ebb Tide Flag Warning
What the flags mean
Extreme Caution
Ebb Tide Very Strong Fluvial Flows -- Fluvial flows are very strong. Conditions are difficult and dangerous. All people-powered vessels are advised not to go afloat on the ebb tide.
Caution
Ebb Tide Strong Fluvial Flows -- The Port of London Authority advise people-powered vessels, in particular; beginners, novices, younger junior (J15's and younger), or any weaker crews, and those that do not usually navigate on the tidal section of the River Thames not to go afloat on the ebb tide.
All river users of people-powered vessels should navigate with extreme caution and consider whether it is safe for them to go afloat on the ebb tide.
Average
Fluvial Flows are average -- All river users to navigate with caution and maintain a proper look out.
Caution
Low Fluvial Flows -- Tidal flow is lower than usual. River users should expect lower than predicted tides especially around low water.
How the flag colour is determined
Every day at 6 am and 6 pm the lowest tide reading for the Richmond tide gauge is taken for the preceding 12 hours.
If the value is 2.6 metres or above then the flag is RED.
If the value is 1.7 metres or above but less than 2.6 metres then the flag is YELLOW.
If the value is 0 or above but less than 1.7 metres then the flag is GREEN.
If the value is less that 0 then the flag is BLACK.
