Silt - a story of dock mud

Further Info

This story was made at a weekly digital storytelling workshop with a Brunel theme for staff and volunteers at Bristol Industrial Museum, inspired by the life and work of Brunel. The stories were created both in formal sessions and in staff members’ spare time with support from Ruth Jacobs, Sarwat Siddiqui, Andy King, Chris Redford and Phil Walker, between Nov 2005 and Feb 2006. The project was supported by Bristol’s Museums, Galleries & Archives.

Transcript

[singing] “Mud, mud, glorious mud. Nothing quite like it for cooling the blood. So follow…”

[singing] “Silt, silt, glorious silt. Nothing quite like it to gunge up your dock. So bless you, bless you, Brunel to the rescue. Now we can flush you, glorious silt.”

Yes silt, ladies and gentlemen, silt. A great problem which has bedevilled the Floating Harbour since it was constructed some two hundred years ago.

[orchestral music plays]

Bristol was once a great port, second only to London, and renowned throughout the world. Hundreds of ships could be seen here, tied up two or three abreast. The docks were thick with masts. But the great port had always suffered two major problems: it was situated some six miles from the river Severn at the twisting, difficult-to-navigate river Avon, and when the tide was out… there was no water. Just what you need for a dock.

By the mid 18th century, Bristol was losing trade to Liverpool, who now boasted extensive new docks, complete with water. Something had to be done.

The dock company adopted a scheme put forward by one of the great civil engineers of the day, William Jessop. His plan was to form a float, by damming the river Avon at Hotwells and Totterdown and diverting its course along a new cut. Once in port, ships would stay afloat at all states of the tide, hence its name, the floating harbour.

Between 1804 and 1809, and at great expense, the harbour was duly constructed. Seemed like a good idea at the time, but by damming the river Avon in this way, and the river Frome that flowed into it, the tidal scour, which had previously carried off all the sewage and other objectionable refuse from the city had effectively been sealed off. William Jessop failed to recognise this as a problem, and had made inadequate provision in his harbour improvement scheme, for keeping the water wholesome. He had built an overfall dam at Hotwells to control the level within the harbour, but in so doing had caused the water to stagnate.

The dock company introduced various measures to deal with the problem, but the build-up of the silt, the sewage and the stench grew steadily worse, and by 1832 had reached really serious proportions.

Enter our local hero, Isambard Kingdom Brunel. Aged only 26 and somewhat financially hard-pressed at the time, he was anxious for large commissions, and seized the opportunity by submitting a report to deal with the nuisance. In a few brief paragraphs he cut through to the problem of silting in the harbour, namely the near-stagnant condition of the water causing it to deposit mud brought down by the Avon and the Frome. In his solution he stated that “A constant stream, though nearly imperceptible in its motion will carry with it the lighter particles of mud which form the principle part of such deposits. If the whole of the river Avon were at all times running through the float, and which I have no doubt Mr Jessop originally intended should be the case, such a stream might generally be obtained.”

He went on to make specific suggestions, which included a steam-propelled device for scraping mud away from the walls of the harbour. Under his direction, a trunk and a set of culverts were prepared to scour mud under the overfall dam, converting it to an underfall. Together, these measures brought remarkable improvement in the silting and conditions, particularly around the Cumberland Basin entrance. The directors thus had good reason to be satisfied with their young engineer.

But had he solved the problem? Well um… well, you see, um… er

[Music of “The Hippo Song” by Flanders and Swan played on viola and piano]

Credits

All media not otherwise credited created by the story author, or permission obtained, used under copyright licence.