Great Sheffield Flood: Dale Dyke reservoir bursts

Background. The dam was built by the Sheffield Waterworks Company to supply water for mills and drinking. Rapid population growth increased demand, leading to construction in Bradfield Dale. The embankment was completed in April 1863, and filling took place soon after; by 10 March 1864 the water level was 2 feet 4 inches (0.7 m) below the crest of the dam. The 1859–1864 construction window applies to the group of four Bradfield reservoirs, not solely this dam.

Failure. At 23:30 on 11 March 1864, the day after the reservoir was full, the dam failed. A crack in the embankment was the immediate cause, though its origin was never determined. A strong south-western gale assisted the collapse, releasing a wall of water that swept down the valley.

Impact. The flood caused massive damage along the Loxley and Don valleys, destroying over 5,000 properties. Sources disagree on the death toll: one gives at least 240, another 244, and a third 270. On 18 March 1864 the mayor called a meeting asking those who could afford it to give up one day's wage for those in need.