Pastures Way flood alleviation scheme, Luton - light case study
Where
Pastures Way in Luton has suffered repeated flooding over the years to both the highways and nearby properties.
Flooding has been recorded in 2005, 2009, 2010 and 2016 and records from Thames Water suggest that in 2012 there was sewer flooding reported.
Based on the modelling carried out by Project Centre, it was understood that flows from the wider catchment (0.87km2) ended up on Pastures Way as it forms the lowest part of the catchment in terms of topographic levels.
The hydraulic modelling demonstrated the incapacity of the public sewer which is affecting the ability of the public sewers to convey the runoff towards Lewsey Brook at a speed that could prevent upstream flooding. This meant that the site could benefit from a bypass system which can alleviate the flooding on Pastures Way.
The initial idea was to use a swale running parallel to Pastures Way which could provide overflow storage and attenuation during higher order events and eventually release it back to the sewer system. However, this meant that in an extreme event the swale would flood the park including the footpath which runs parallel to the proposed swale. This footpath is currently used by school children and must be functional at all times.
In response to this issue, Project Centre redesigned the flood routing system to consist of an interconnected rain garden swale and detention basin system which will attenuate water before releasing it slowly into Lewsey Brook.
The proposed scheme is intended to protect 18 houses along Pastures Way from surface water flooding from overland flows up to a one in 75-year event. It is envisaged that the swale will offer an overflow storage relief of 2200m3 .