Bridges No.27 - Richmond Lock

Next up is a rather curious structure that looks like a bridge, and doubles as a bridge but has another identity - a tidal barrier.

The river, even at Richmond is still tidal in nature although we are now very close to Teddington where all marine influence ends. Until 1832 the Old London Bridge (the one with all the houses built on it) had almost acted as a full barrier across the Thames and had reduced the tidal effects further upstream. When it was demolished there were unexpected consequences further upstream. Some bridges suffered from increased erosion at the base of their piers and ultimately had to be replaced with the faster moving tides. At the same time dredging activity increased in the lower reaches of the river. At Richmond the size of the river shrunk significantly to the extent that on some occassion it was little more than a stream running through mudbanks. The river can still get quite narrow - just look at my picture of Barnes Bridge at low tide to see.

In 1890 premission was given for the construction of a half-lock and weir just downstream of Richmond. A barge lock was built against the Surrey bank joined by a weir and three sluice gates. To operate the sluices a superstructure was required and it was decided that this should take the form of a footbridge. For two hours during high tide the sluices are raised into the footbridge structure and boats can pass through as if this were a normal bridge. For the rest of the tidal cycle the sluices are moved down and closed. Boats must then use the lock system. This results in maintaining water levels between Richmond and Teddington locks.