The Tides at Richmond Upon Thames

AW, 240522

Introduction

At HCC, we’re used to the water moving monotonously, heading downstream all the time.  Sometimes it flows more quickly than usual, and yellow or even red boards are displayed at the locks and on the EA website.  But still it just goes downstream; it falls over the weir at Sunbury, drifts past the clubhouse and falls over the weir at Molesey.

 

At sea, it’s usually quite different because of the tides.  The level of the water rises and falls, pulled by the gravitational tug of the Moon circling around the Earth.  The water advances and recedes across the beach in a predictable way:  the times of high tide and low tide can accurately be predicted years in advance; the heights of the water can be predicted too, but with less accuracy (they get affected by other meteorological events.)

 

Plenty of websites show the times and heights of tides; one is the BBC, showing here the tides for Dover: 

https://www.bbc.co.uk/weather/coast-and-sea/tide-tables/9/89#2020-09-05

 

To enable the water to fill or empty a beach, the tidal curents move the sea back and forth, generating tidal currents which can flow as fast as, or faster, than any kayaker can paddle.  Knowing which way the currents are moving is vital when planning a trip on our coasts or estuaries.  A lot of sea trips quite reasonably plan to go with the current until lunchtime, then wait for the current to change direction.  The return journey uses the reversed current to assist the paddle back to the launch point.

 

The same principles apply in estuaries – and, navigationally speaking, the Thames is an estuary as far inland as Richmond/Teddington.  Stand on London Bridge (or any bridge across the Thames between the sea and Richmond) and observe the current:  sometimes it’s flowing out to sea, at others it is flowing inland as the tide rises.  Both when flowing inland or seawards, the currents in Thames estuary can reach 4 knots (ie about as fast as you can paddle). 

 

At Richmond it’s different

The tides between Richmond and Teddington are fundamentally different from practically anywhere else on Earth.   Usually a river is a river, and it becomes tidal as its estuary meets the sea.  But between Richmond weir and Teddington weir, it is wholly a river some of the day, and wholly tidal the rest of the day.  How does that happen?:  the weir at Richmond is moveable!  It’s a part-time weir.  It can be completely lifted and lowered at the whim of the lockkeeper on site.

*** to follow:  photo of Richmond weir half open

 

When the weir is lifted up out of the way, motor boats can pass underneath.  When the weir is lowered, motor boats use the lock, just as they would at any other lock.  Paddlers equally paddle under the (lifted) weir when it’s up, and use the portage on the Twickenham (west) side when the weir’s down.  BEWARE:  the portage is always slippery and muddy.

 

When it’s high tide at Richmond, the weir is up out of the way.  Incidentally, when it’s high tide at Richmond, it’s also high tide at Teddington, and high tide at London Bridge was 60 minutes before.  The tide falls, with the water flowing seawards.  After maybe an hour and a half, or two hours, the water reaches the defined level and the weir is lowered into position (actually, each of its three sections is lowered into position, one at a time.)  Then the Thames between Richmond and Teddington behaves like it does all the way up to Lechlade:  it has a steady level.  Below Richmond, the Thames is full-time tidal and falls until low tide; then it rises again. 

 

When it’s low water at Richmond (actually, the water spends quite a while near the low water level) it’s quite muddy in that vicinity.  Gradually the water level rises as the current comes in through central London from the North Sea.  After a few hours, the water reaches the level of the weir, and the weir is lifted.  Motor boats and paddlecraft can then pass through.  The Thames is now flowing inland toward Teddington as it would in a tidal estuary, and it carries on until it’s high tide.

 

This cycle repeats every 13 hours, approximately, with two exceptions:

Sometimes the Thames Barrier at Woolwich is closed to keep out the incoming tide, either because the tide is dangerously high, or for routine maintenance. Then the low water state lasts for about 13 hours until the next incoming tide arrives.  Routine closures can be found at

https://www.gov.uk/guidance/the-thames-barrier#forthcoming-scheduled-closures 

and other closures by calling 0208 305 4161.

Usually there’s a period of 3 or more weeks in the late autumn when the weir’s left open for a few weeks to facilitate repairs between Teddington and Richmond. Then the Thames is fully tidal up to Teddington, falling at low water to unusually low (and muddy) levels.  The dates for the ’Draw-Off’ are publicised by the Port of London Authority a couple of months in advance at https://www.pla.co.uk/Safety/Regulations-and-Guidance/Notices-to-Mariners/Notices-to-Mariners

 

BTW sometimes the tide is so high that it overtops the weir at Teddington and forces the river to a standstill up as far as Kingston. When this happens, after the tide turns there’s a period of catch-up when the water’s moving faster than normal.

 

Here’s a timetable of what all this means for paddlers:

PADDLERS’ TIMETABLE FOR RICHMOND

Time Just below Teddington Weir Twickenham/Eel Pie Island Richmond above the weir Richmond below the weir
High water Most (or all) of the portage is undewater.  The water is barely moving. All the beaches and getouts are full of water.  The water is barely moving. The water’s barely moving. The water’s barely moving.
An hour later; Richmond weir’s still up. The portage has mostly emerged from the water.  The water’s flowing a bit faster than it is above the weir (it’s a bit narrower here). Most of the beaches and getouts have emerged from the water.  The water’s flowing faster than it is above Teddington. The water’s flowing much faster than it is above Teddington as it heads out to the North Sea. The water’s flowing much faster than it is above Teddington as it heads out to the North Sea.
The weir closes around 90 – 120 minutes after high water.  After that: The portage has emerged from the water.  The water’s flowing a bit faster than above the weir. The water level is as usual for low water around here.  The water’s flowing as fast as it is above Teddington. The water level is as usual for low water around here.  The water’s flowing as fast as it is above Teddington. The water level continues to fall.  The water near Richmond is flowing as fast as it is above Teddington; further on down around Kew and beyond, it is going much faster.
Low water The water’s flowing a bit faster than above the weir. The water’s flowing as fast as it is above Teddington. The water’s flowing as fast as it is above Teddington. The speed of the water slows down, and eventually reverses to head inland.
An hour later; also several hours later The water’s flowing a bit faster than it is above the weir. The water’s flowing as fast as it is above Teddington. The water’s flowing as fast as it is above Teddington. Below Barnes, the water’s heading inland at up to 4 knots.  Near Richmond, this slows to nearly nothing.
After the weir’s been lifted The water slows down once it meets the incoming tide. The water has reversed direction and is heading gently inland. The water has reversed direction and is heading inland quickly. Near Richmond, the water’s speeded up and is heading inland at up to 4 knots.
15 minutes before high water The water’s slowed, it’s nearly static.  The water’s slowed, it’s nearly static. The water’s slowed, it’s nearly static. The water’s slowed, it’s nearly static.