Due to its location beside the confluence of the River Derwent and the Markeaton brook, Derby has a long history of being flooded from either the brook or the river.
St Werburgh's Church, which is located next to the brook, suffered greatly from flood damage, such as in 1673, when "A great flood upon the Markeaton brook, carried away the hay, filled cellars as high as the Angel, Rotten Row, and broke down three of the ten bridges”, again in 1677 and in November 1698 “A great flood which washed down part of St. Werburgh’s church and the steeple fell." The church faced further floods in the 18th and 19th centuries.
In the early 1930s there were two major floods caused by the brook, which provided the impetus to find a solution, and prevent further flooding in Derby. The planned solution was the construction of two flood relief culverts, with associated improvements to the sewerage system. Opened in 1938, the largest of the diversion tunnels was called the Northern Flood Relief Culvert, and drains excess flows from the Markeaton and Mackworth brooks.
It has been estimated that during a large storm the catchment can generate a flow of 50 cubic metres per second (1,800 cu ft/s), within thirteen hours of intense rainfall. Summer flows are much smaller, with the brook producing a flow of only 0.35 cubic metres per second (12 cu ft/s)
The northern relief culvert commences at MarkeatonPark, near to the confluence of the Markeaton and Mackworth brooks. Each brook has its own inlet spillway, with a weir that overflows during periods of high flows. Flows from these inlets converge, and are then taken by the relief culvert eastwards for 2.2 km through the suburbs of Derby, to an outfall with the Derwent in DarleyPark
Met up with @UrbanCaving, @KM_Punk, @Sids, @Deconstrukt, AccessDenied, Aisha and Kensee on the hottest day of the year and it was great to get into the cool depths of this awesome drain with some great international peeps.