As the watercourse adjacent to the site is culverted, the risk of fluvial flooding could not be properly quantified as no detailed flood levels were available. EAS then built a simple 1D hydraulic model to establish the likely flood levels on the existing site for a number of fluvial return period flows. A ‘proposed’ scenario was also modelled, whereby the proposed landscaping and buildings were included in the model. The Environment Agency then approved this model which was used to inform the Flood Risk Assessment.
A 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.
As construction got underway, EAS were again approached by the contractor to apply for an Environment Agency Flood Risk Activity Permit for activities taking place within 8m of the culverted Wealdstone Brook, including the construction of the basement car park. EAS completed all permit application forms as well as producing Methods Statement and Environmental Risk Assessment. EAS also worked with the chosen contractor to collate all required information to ensure a smooth and successful permit application.
The Environment Agency Permit was granted in January 2021.