cbec was subcontracted by Arup to complete a topographic survey of the New River, a 36 km man-made channel that diverts flow from the River Lea (Hertfordshire) to the Stoke Newington Reservoirs in London

The channel was created more than 150 years ago to provide water to the Hornsey Water Treatment Works, now operated by Thames Water; however, over time the channel had become silted and flow capacity had been reduced. As a result, Thames Water engaged with Arup, cbec and Edenvale Young to undertake an investigation into the hydraulic capacity of the New River in 2021, which involved assessing the level of silt in the channel and advising on the most cost-effective measures that could be implemented to improve flow conveyance to the water treatment works.

A topographic survey was undertaken by a number of cbec field staff using a combination of Trimble R12 real-time kinematic GPS and Trimble S6 total station, along with a high-specification HyDrone remote-controlled craft equipped with SonarMite BTX single-beam echo sounder, in order to determine the channel geometry and silt levels in the channel. cbec’s hydrology team also undertook flow data measurements to supplement water level data from known gauges, used for calibration purposes. These data were then utilised for input into a one-dimensional hydraulic model, which was used to assess the effect of different potential solutions on flow conveyance to the Hornsey Water Treatment Works.