Great Sheffield flood
Coordinates: 53°25′05″N 1°38′25″W / 53.41796°N 1.64036°W
The Great Sheffield Flood was a flood that devastated parts of Sheffield, England, on 11 March 1864, when the Dale Dyke Dam broke as its reservoir was being filled for the first time. At least 240 people died and more than 600 houses were damaged or destroyed by the flood. The immediate cause was a crack in the embankment, but the source of the crack was never determined. The dam's failure led to reforms in engineering practice, setting standards on specifics that needed to be met when constructing such large-scale structures. The dam was rebuilt in 1875.
Sheffield is a city and subdivision of South Yorkshire, England. As the town industrialised, its population grew from 45,478 in 1801 to 185,157 in 1861. This rapid population growth resulted in the construction of the Dale Dyke Dam for the purpose of providing a more efficient source of clean water. It was created by the Sheffield Waterworks Company (SWWC). During the late 1850s, the company purchased land in the Loxley Valley to the north-west of the town, on which to build a reservoir. By the 1860s the dam and its associated works had been passed as satisfactory and it was allowed to fill with water.
On the night of 11 March 1864, assisted by a strong south-western gale, the newly built dam, known as the Dale Dyke Dam in Bradfield Dale near Low Bradfield on the River Loxley, collapsed while it was being filled for the first time. An estimated 3 million cubic metres (700 million imperial gallons) of water swept down the Loxley Valley, through Loxley Village and on to Malin Bridge and Hillsborough, where the River Loxley joins the River Don. The flood continued south down the Don into Sheffield centre, around the eastward bend of the Don at Lady's Bridge, then to Attercliffe, past the sites of what later became Don Valley Stadium, Sheffield Arena and Meadowhall Centre, and on to Rotherham. A wall of water moved swiftly down the valley, destroying everything in its course. The centre of the town, situated on the hill to the south, escaped damage, but the densely populated district of the Wicker, around the new railway viaduct (constructed by the Manchester and Sheffield Railway), was completely destroyed. The company's consultant engineer, John Towlerton Leather, was one of a family of worthy Yorkshire engineers who were involved in such work. His uncle, George Leather, had been responsible for reservoirs around Leeds and Bradford, and one of these was the scene of a dramatic collapse, in 1852, when 81 people died. John Leather and resident engineer John Gunson were working closely together during the construction of the dam. Leather designed the dam and oversaw its construction whereas Gunson directed and supervised the construction of the dam. Gunson was on site the night of the collapse and stated that there was a concerning crack in the outer slope of the embankment. Gunson convinced himself that the crack was not harmful but still took the precaution of opening up the valves on the middle of the embankment to allow more water through. This failed to prevent the crack from worsening.
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