Before any vessel ventures onto the 95 mile tidal section of the River Thames, whether up or down stream, it is essential to consult the River Thames Tide Times. The PLA (Port of London Authority) publishes these times up to 2 years in advance, which are given in Greenwich Mean Time , so users must remember to add one hour when British Summer Time is in force.
Without consideration of the times of high and low tide, vessels could find themselves unable to move due to a lack of water at low tide. Conversely, at high tide, a tall vessel may be unable to progress under certain bridges on the river. For this purpose, there are marker posts on the approach to bridges, giving the air draught to enable vessels to safety proceed.
The PLA has managed a range of duties on the tidal Thames for more than 100 years. Their principal responsibility is the safety of navigation on the tidal 95 miles of river from Teddington Lock out to the North Sea.
During incoming and outgoing tides, the flow of the water can rise to five or six knots (7 mph or 11 kph). With the addition of heavy rainfall plus choppy and confused water, swells of 1.2metres are typical. Aided by sheer river walls and the movement created by large or fast moving boats, the power of the tides should not be taken lightly.
The high/low tide times change between half an hour and one hour each day and the tide flows in and out very quickly. At Teddington when there is a high tide, the water can be seen to rise above the height of the weir. This affects the water level through Kingston and upstream to Hampton Court Palace. The river frontage at Richmond is often under water. We have approached Teddington Lock on the high tide whilst transiting from Limehouse and have seen the bottom and the top gates open together. This happens on occasions when the tide is above the height of the weir and the lock keepers allow boats to travel through the lock without stopping.
At London Bridge, where the tides are measured, the depth of the Thames at low water is about 20 metres at its deepest. At high water you can add 5 to 7 metres to that depth. At the opposite end of the scale, upriver at Kew, we have seen boats negotiate a course with great difficulty, as the depth there is closer to 1 metre.
Of the 95 “tidal” miles, Kailani is the only Hotel Boat licensed to cruise the 20 miles between Limehouse Marina and Teddington. PLUS, of course, the remaining 116 miles of the non-tidal Majestic River Thames from Teddington to Lechlade (and back!)