Palmerston Road, Wealdstone, Harrow

The Palmerston Road development is a gateway mixed-use residential and retail development in Wealdstone, Harrow. EAS built a 1D HECRAS hydraulic model as part of a Flood Risk Assessment to estimate the flood depth as a result of the culverted Wealdstone Brook surcharging during extreme events.

The Environment Agency (EA) did not hold any modelled flood data for the site, as the flood source was a culverted watercourse. EAS prepared a hydraulic model to determine the maximum flood depth within the site boundary during an extreme event. This flood depth and level was then used to evaluate the floodplain compensation required as a result of building on the ‘floodplain’. EAS met with the EA and the London Borough of Harrow to agree the best way to estimate the flood depth and address the EA’s requirements on floodplain compensation modelling. A solution was agreed whereby the floodplain compensation was

A detailed drainage strategy was also prepared by EAS to restrict runoff to the culverted brook in line with Sustainable Drainage principles involving a series of underground storage crates. Planning permission was granted in March 2017.