Bulkington Flood Alleviation

Due to space restrictions the original proposals, consisting of below ground large diameter pipes and manholes which would have been both costly and disruptive due to requiring road closures. Future development planned in the catchment would also increase the likelihood and frequency of flooding.

Our role was to confirm the extent of the flooding, carry out a feasibility study to investigate options and undertake hydraulic modelling to predict the level of protection for various rainfall events up to 1 in 30 years, with an allowance for climate change. We then undertook outline design of the preferred solution.

The traditional solution consisting of underground large diameter pipes was too expensive and disruptive, involving road closures and diversion of utility services. The urban location of the flooding limited options for solutions outside the public highway. Our client aspired to minimise carbon footprint of the works and maximise any potential environmental benefits.

Based on recent experience with other clients we proposed alternative, sustainable urban drainage solutions consisting of rectangular rain gardens set in the grass verge along with a detention basin. The rain gardens were positioned allowing for the constraints of access, below and above ground services, street furniture and existing trees. They utilised clean stone aggregate to create a void space beneath a planted topsoil layer. They capture run off from the adjacent highway and property roofs, attenuating flows prior to release into the surface water sewers. They also improve runoff quality by capture of pollutants.

The detention basin is sited immediately prior to discharge into the watercourse attenuating and controlling flows. The rain garden solution provides flood protection at an affordable cost with substantially reduced impact on the community.