by David Clarke, Chiswick Lifeboat Crew 2002-2004
The Lifeboat’s vhf radio squarks “Chiswick immediate – persons cut off on Lot’s Eyot!”
We are on exercise in Corney Reach within sight of the station; helmsman Glen rams the throttles forward and the E-class lifeboat leaps ahead, reaching its top speed of 40 knots in a few moments. We get an update from the coastguard – “four children stranded on the foreshore!”.
We arrive on the scene in Brentford, three miles and five minutes later, to see four children standing against tall steel pilings on a visibly diminishing strip of shingle. The tide is rising fast, their narrow piece of dry land would only last another few minutes. We quickly gather the children into the lifeboat and check that they don’t have any injuries. They are soon landed back on the ‘mainland’ safe and sound. It turns out that they had been given pocket money to go to the swimming pool but bought sweets instead and went for a walk along the river. They crossed at low tide onto Lot’s Eyot to explore the derelict boatyard (now operating again, and with new footbridge access) and found themselves cut off.
In Chiswick Lifeboat’s patch the tidal range is over five and a half metres. Because of the shape of the tidal river the flood tide takes only four hours while the ebb tide lasts just over eight hours. This means the current is much faster on the incoming tide causing a rise of 1.5 metres in an hour at peak flow. This rapid rise catches people out on a regular basis. Walkers on Chiswick Mall are often tempted to walk out to Chiswick Eyot at low tide. By the time they have crossed to the other side of the island their return route has disappeared. On peak spring tides the island is completely inundated; we once rescued two lads who had clambered into a tree to escape the rising water.
The height of the river at high tide varies significantly between springs (highest) and neaps (lowest). Springs occur at full and new moons when the gravitational pull of the sun and the moon combine.
The speed of the tide also means that people (or animals) who find themselves in the water can be nearly half a mile away from their initial immersion in the minutes it takes for the Lifeboat to arrive. Crews monitor the state of the tide all the time when on shift so take the tidal movement into account on a search.
There are times when we wonder whether people are just not aware that the river is tidal. Many times a year we are asked to check cars that are half submerged and sometimes they can they float and need to be secured to prevent a hazard to navigation.
A bizarre phenomenon that can also catch people out happens after prolonged periods of heavy rain when huge amounts of rainwater flows through the weirs at Teddington resulting in the surface current continuously running downstream even when the tide is rising. Car drivers who are familiar with the tidal river may have seen the signs warning of risk of flooding but confidently park as they see the current running downstream only to be dismayed when they return to see their precious motor having a paddle.
Another strange effect occurs when the Thames Barrier is used to prevent fluvial flooding. After periods of heavy rain there is a risk of significant flooding when increased flow of rainwater from upstream combines with a tidal surge created by easterly winds. To prevent this, the barrier is raised at low tide to create a basin to fill up with the rainwater run off. When this happens the there are no normal tides in our patch.
Chiswick RNLI lifeboat usually operates between Battersea and Richmond lock. Two hours either side of high tide the barriers alongside the lock are raised so vessels can proceed without locking through. In this period the lifeboat can reach incidents further upstream within in its 15 minute target response time. The notice board in the crew room has the tide times at Richmond posted each day so that the duty crew know when they have this option.
As well as rescuing people in difficulty in the river, Chiswick’s crews often respond to casualties on the foreshore where access from the towpath is impossible. After falls from the river wall there is always a risk of spinal injuries when casualties should not be moved hastily. Often these incidents coincide with a rapidly rising tide so the casualty has to be taken to safety immediately. All lifeboat crews are trained to deal with this dilemma and the boat carries a spine board as well as neck braces and a basket stretcher so the casualty can be immobilised before being moved.
Although tide tables generally predict accurately, weather conditions can significantly change water levels so it is important to be vigilant when going on or near tidal rivers. If you see someone cut off by the tide or in difficulty in the water the RNLI encourages people to call 999 and ask for the Coastguard. Chiswick RNLI Lifeboat is manned 24/7 and has a launch target of 90 seconds so can reach incidents very quickly.
Chiswick RNLI lifeboat station is the second busiest in the UK and Ireland. Since the RNLI search and rescue service on the Thames started in 2002, Chiswick Lifeboat has attended over 3,700 incidents and rescued over 1,750 people. The RNLI is entirely funded by public donations.
Check Tide Times On The Chiswick Calendar Website
Don’t get caught out by the tide! We’re delighted to announce you can now check the tides at both Chiswick Mall and Strand on the Green in a brand new section on our website here: chiswickcalendar.co.uk/chiswick-tide-times
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