London Bridge Starlings

Look at London Bridge, so firm and fixed.

Imagine the force required to lift the central section of the road bridge to allow the passage of tall ships.

It is not the first London Bridge, but its design follows a pattern from earlier London Bridges.

Those buttresses you can see at water level are known as starlings.

The origin of the architectural term “starling” for a bulwark supporting a pier in a river is thought to be derived from the Old English word “stedeling”, which meant “place” or “standing place”. Or derived from the Old Norse word “staurr”, which meant “pile” or “post”.

Regardless of its origin, the term “starling” has been used in English since the 14th century to refer to these bulwarks.

Remember this is a river bridge, and with the tide up the estuary there could be a two metre (six feet) difference in height between the river’s tidal ebb and flow.

The starling’s triangular or trapezoidal shape and sloping sides prevents the accumulation of sediment and deflects the force of waves away from the pier, reducing drag and preventing vortices that would otherwise erode the foundations.

Starlings on the river bed also create a complex flow pattern, which helps to reduce the overall velocity of the water. This dissipates energy and reduces scouring by stones and silt in the water.

It tickles me that engineers many hundreds of years ago had already accumulated the technical knowledge and expertise about protecting structures standing in flowing water.

The Old London Bridge that fell down also had starlings to support its piers.

What it also had were also more than a hundred shops and dwellings sitting on it, some seven stories tall.

And it burned down, and fell down.

London Bridge is falling down,
Falling down, falling down,
London Bridge is falling down,
My fair lady.

Before the old bridge fell down it was the site for showing what happened to traitors. The heads of traitors were dipped in tar and boiled to preserve them against the elements and then impaled on spikes and displayed on the bridge.

I shall think on that next time I see the bridge.

For a picture of English rebellions, there’s Watt Tyler and the Peasant’s Revolt in 1381, and Jack Cade’s Rebellion in 1450.