The impact of a convectional summer rainfall event on river flow and fine sediment transport in a highly urbanised catchment: Bradford, West Yorkshire

Urban watercourses are important assets to cities, but they often have extremely ‘flashy’ hydraulic regimes and poor water quality, making them potential hazards. Current knowledge of the impact of intense rainfall events on urban river water discharge and, in particular, fine sediment transport is limited. Continuous monitoring of flow and turbidity (subsequently calibrated to suspended sediment concentration) was undertaken at a network of four sites throughout the highly urbanised Bradford catchment in West Yorkshire, NE England. An intense convectional rainfall event, which occurred over central Bradford in June 2001, generated extreme flow and fine sediment transport responses at the most downstream site, Shipley Weir. In just 15 min, discharge increased from 0.45 to 34.6 m3 s−1 (median annual peak instantaneous discharge of 27.5 m3 s−1, 1983–2001) and suspended sediment concentration increased from 14 to 1360 mg l−1. A peak sediment flux of 47.2 kg s−1 was recorded. It is demonstrated that this extremely large and urban flux of fine sediment is likely to have a major downstream impact on water quality in the River Aire.