Winnie the Pooh sails the Thames The River Thames
From Source to Sea

Tidal Rivers can cause Problems

A Problem

mapThe River Thames is tidal from Teddington to the sea. When the sea goes out so does the water in the river, even though the North Sea is still 65 miles (104 kilometres) downstream. At its most extreme this tidal change can be as much as 7 metres. In fact, the river would be just a small stream when the tide was out. This means that at low tide ships would find it hard to sail up the river.

The Solution

A half-lock was designed and built at Richmond to control the tidal flow.

The lock comprises of three vertical steel sluice gates suspended from the footbridge.

Richmond half-lock
Richmond lock
Looking downstream. The lock is on the right.
Part of the Lock

For around two hours each side of high tide, the sluice gates are raised into the footbridge structure above, allowing ships and boats to pass through (see photo below).

Richmond half-lock

For the rest of the day, the sluice gates are closed, and passing river traffic must use the adjacent lock on the Surrey bank. The gates are closed so that there is always at least 1.72 metres of water in the River between Richmond and Teddington.

Richmond half-lock
Sluice Gates are down holding back the river

Richmond half-lock
Looking up stream. The lock is on the left.

Start of Voyage down the Thames Contents Page Introduction
Facts about the Thames Flooding Thames Basin
Pollution Erosion Tributaries



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I teach computers at The Granville School and St. John's Primary School in Sevenoaks Kent.