An online tool that highlights opportunities to to tackle road run-off pollution, before it ends up in London’s rivers, has gone live.

Road run-off pollution in rivers and streams comes from spills of oil, diesel and petrol, and from the wearing of roads, tyres and braking systems. All this vehicle activity leaves residues and sediment that are then washed off the roads by rain, and flushed into waterways.

It is possible to capture some of this run-off and filter the pollution out by creating natural barriers and filters including roadside green spaces, wetlands and swales.

Government agencies and departments that oversee road runoff pollution have faced severe cuts in recent years. Thames 21 says the Government must step-up to provide the highways authorities and the Environment Agency with the appropriate funding in order for them to boost their investment in capturing pollutants at source and nature-based solutions to properly protect the capital’s rivers.

Deputy mayor for energy & environment, Shirley Rodrigues, said: “London's rivers are in desperate need of a clean up, which is why the mayor called for the Government to provide the appropriate funding for measures to properly protect the capital’s rivers. Thames21's pollution tool, funded by the mayor, builds on the first phase of work in 2019, and will provide Highways Authorities with a toolkit to address the significant risk from road run-off to the health of London's rivers.”

Alex Williams, chief customer & strategy officer at Transport for London said, “This report highlights the importance of road run-off as a contributor to pollution entering watercourses in London. TfL is working hard on encouraging a shift to more sustainable and cleaner forms of travel, which will reduce the amount of road runoff pollutants being created in the first place.

"For example, we have expanded the Ultra Low Emission Zone to discourage polluting vehicles, are investing in Healthy Streets schemes, and run a world-class public transport network. But there is more we need to do to avoid any remaining road run-off pollution entering watercourses.

Our Adaptation Plan includes a SuDS target that we’re on track to meet this year, and we have made SuDS the default drainage solution for our schemes. We look forward to using this tool to help us identify where SuDS schemes would be most likely to be effective.”

The development of the online tool builds on years of research by environmental charity Thames21 and its partners Middlesex University and the South East Rivers Trust. The charity started its initial road runoff project identifying key polluting London roads in 2019, with help of funding from the Mayor of London, Transport for London, and the Environment Agency.

The British Geological Survey built the online decision-support tool - Road Pollution Solutions - and provided some additional support through the UKRI NERC-funded CAMELLIA project.

The tool will help decision-makers prioritise suitable water quality improvement interventions:

• In greenspaces that lie between the road and the river
• At road locations in Outer London where surface water drains to the rivers
• On London’s main strategic road network

The partners say there should also be a focus on addressing the sources of the sediment and oil.

Modelling has shown that 2,415 road sections, covering over 450km of London’s roads, pose a high risk of causing road run-off, and are therefore a priority for treatment to help prevent pollution entering rivers. Roads where heavy goods vehicles regularly apply their brakes are often the worst affected.

The boroughs with roads carrying the highest concentration of predicted pollutants are:

• Barking and Dagenham
• Barnet
• Havering
• Haringey
• Waltham Forest

Working in partnership, the authorities responsible for these roads could intervene, providing nature-based solutions around these areas to help make runoff cleaner and improve water quality in local rivers and watercourses. It is hoped that the online tool will be replicated in other parts of the country prone to road runoff pollution to protect rivers and improve water quality.

“Pollutants from road run-off are having a devastating impact on aquatic wildlife, including killing off fish," says John Bryden, head of improving rivers at Thames21 said. "As more people look to London’s rivers for recreation, we all need to up our game.

“Strategically-placed sustainable drainage systems such as wetlands or swales can be an excellent way to reduce road run-off pollution, reduce flood risk and improve the urban environment for wildlife and for people. So, it’s extremely important that we have worked in collaboration with our partners on this pioneering research and on developing this new tool.

“We hope this tool will be helpful to authorities responsible for the roads in London, and others, to help them to reduce runoff pollution, in order to improve our water quality and the health of our rivers. There is also potential for this tool to be replicated across other locations in the UK in order to help others improve our waterways.”