Viaduct until 24 August 2008, when they were demolished, scuppering alternative plans to use them as a public art installation. Water quality The Environment Agency measure the water quality of the river systems in England. Each is given an overall ecological status, which may be one of five levels: high, good, moderate, poor and bad. There are several components that are used to determine this, including biological status, which looks at the quantity and varieties of invertebrates, angiosperms and fish. Chemical status, which compares the concentrations of various chemicals against known safe concentrations, is rated good or fail. The water quality of Blackburn Brook, which appears to only cover the stretch from below the junction with Charlton Brook to the River Don, but includes Hartley Brook Dike and Ockley Brook, was as follows in 2019. The river has not been classed as good quality because of physical modification of the channel, which affects invertebrates, and discharge misconnections, where household sewage wastes have been inappropriately connected to the wrong drainage network. Like many rivers in the UK, the chemical status changed from good to fail in 2019, due to the presence of polybrominated diphenyl ethers (PBDE), perfluorooctane sulphonate (PFOS), mercury compounds and other chemicals, none of which had previously been included in the assessment. Flooding Water levels are monitored by the Blackburn Brook at Sheffield Wincobank gauging station. The normal range for this location is between and . During the 2007 United Kingdom floods the level recorded by this station was . The brook burst its banks at the entrance to Chapeltown Park, and where the stream flows under the A629 Cowley Lane. Many properties on Cowley Lane and Falding Street were flooded and a local schoolboy had to be rescued from fast flowing waters after falling into the stream. Since the 2007 event, normal river levels at Wincobank have been updated, and are between -0.02 metres and . The highest level recorded has also increased, as it reached on 7 November 2019, during the 2019 flooding event. Flood warnings for the Blackburn Brook and Ecclesfield Brook were issued on 7 November 2019, and despite water levels exceeding any previously recorded, flooding was restricted to Mill Road and Whitley Lane in Ecclesfield, caused by blockages in the Whitley Brook culvert, to Butterthwaite Lane and Station Road in Ecclesfield, where the Blackburn Brook could not contain the volume of water, and to