During the course of a Road Safety Audit in Hertfordshire, TMS safety auditors Harminder Aulak and Mark Steventon came across a novel swale drainage system for a new large residential development. The system is designed to capture rainwater using a sustainable drainage system along the primary infrastructure “green corridor” roads, rather than a traditional closed gulley system which discharges into storm sewers.  The principle of the open grass swales is to retain as much surface water on the site as possible to achieve the Environment Agency’s requirement of keeping runoff from the site at its current level.

The open grass swales are positioned between the carriageway and footway, with surface water channelled into the system by providing lowered kerbs. A photograph of the system is shown below:

We carry out Road Safety Audits all across the UK and this was the first time the audit team have come across a drainage system like this. This novel and sustainable solution to drainage is likely to become more common across the UK as the need to look for more sustainable drainage solutions increases.