Thought of the Day – 11th March

The 11th of March 1864

Sometime between 11pm and midnight on March 11 1864 what had been a slight crack in the new Dale Dyke Dam six or seven miles north west of Sheffield suddenly expanded until the force of the water behind it swept aside much of the construction. A section 330 feet wide by 75 feet deep gave way, and in seconds a wall of water burst through.

In spite of a farm labourer crossing the dam spotting the beginnings of a crack at 5.30pm, by the time engineers had been fetched, inspections made, and action deliberated, it was tragically too late. The chief engineer did try to ease the pressure on the dam first by opening some safety valves, and then in desperation by trying to blow up part of a weir, but the bad weather prevented the detonation of gunpowder intended to do the job.

The Sheffield Water Company's new dam, in the Bradfield hills above Sheffield, was about 90 per cent full, construction and commissioning of the structure which had begun in 1859 was nearly complete. Criticism after the event centred on calculations that showed the pressure of the water behind the dam necessitated a well anchored wall 55 feet thick. The actual wall was 40 feet thick.

An artificial lake covering 78 acres was held behind the wall; that is a strip a mile and a quarter long and a quarter of a mile wide. Two million tons of water, half a billion gallons and more, gushed through the broken barrier and flooded down the Loxley Valley, meeting the Rivelin river and combining to flow into the River Don . In its path Bradfield, Damfield, Little Matlock, Malin Bridge, and areas of Hillsborough and Owlerton were devastated.

When the flood had passed more than 250 people had died in the disaster, perhaps as many as 270; 100 factories had been demolished by the waters, and more than 400 houses and cottages. Twenty bridges had been thrown aside as if they were feathers caught in a gale. Bodies were recovered from the other side of the city, many of them mangled by the power of the water and their collisions along the flood's route.

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