Road runoff update
In my previous articles, January 2023 and July 2024, I discussed the issue of harmful pollutants in road runoff ending up in our rivers and I stated that contaminated water from transport residues made up 13% of all pollutants in our rivers.
Whilst 13% might seem a small percentage of the total pollution, road runoff does contain some of the most toxic of pollutants such as trace metals, hydrocarbons, chemicals and other organic pollutants, see study carried out in 2019 which claims that there are some 300 different pollutants that can cause environmental damage when carried into the river from roads when it rains. This can be particularly harmful when severe rain storms follow extended dry periods.
You may ask why I am revisiting this subject? The answer is that members of ERA’s steering group attended a webinar hosted by Western Sussex Rivers Trust (WSRT) on road runoff, presented by Jo Bradley of Storm Water Shepherds.
Following the webinar I revisited the Stormwater Shepherds’ website and on the page The Times They Are A-Changing, I found that Jo Bradley quotes an article in the Guardian newspaper on 19 July 2025 that brought some hope to the team at Stormwater Shepherds. The article explained that “The commitment by Steve Reed, the environment secretary, aims to highlight that, while sewage spills into waterways are a significant source of public concern, runoff from farms and roads also makes up a critical part of the pollutants going into rivers and other bodies of water.”
The article also acknowledges that “nearly 20% of water bodies saw pollutants from roads and transport, including oil, chemicals and the residues from tyre and brake wear, a problem made worse by heavy rain.”
Jo’s comment on this article is “This government recognition of pollution from highway runoff is new, and we hope that it is, in some small part, a result of our continued pressure and our persistent sharing of evidence to show the extent of this pollution.
“At the same time, the Planning and Infrastructure Bill is passing through Parliament at the moment, and Part 1 of the Bill will lessen the consultation stages for Nationally Significant Infrastructure Projects, and that risks the construction of new road schemes without the proper interrogation of their pollution prevention schemes.
“So, we have taken one giant leap forward with the recognition of pollution from highway runoff, but we risk taking 2 steps backward with the weakening of the planning process.
“It will be very interesting to see how things unfold over the next few months, but you can rest assured that the team here at Stormwater Shepherds will be watching closely to make sure that pollution from highway runoff is effectively controlled in years to come so that our rivers can recover from decades of harm.”
In 2023 I quoted research that Road Run off was 13% of the pollution in our rivers and waterways, now Stormwater Shepherds claim it is up to 20%, the trend is in the wrong direction.
Key Points from Jo Bradley’s Storm Shepherds webinar
Polyaromatic Hydrocarbons (fossil fuel based) up to 50 times higher than the standard safe level have been found in rivers that are in close proximity to roads that carry up 30,000 vehicle per day.
Other toxic pollutants include Copper, Zinc, Microplastic Tyre Wear Particles etc. These pollutants cause harm to aquatic organisms that live in rivers and streams. They cause mutations and deformations, disrupt cardiac function, prevent reproduction, they are carcinogenic and lead to failure to mature. These organisms are the bottom of the food chain for fish and aquatic mammals and birds. The result is that they can be a significant cause of biodiversity collapse and ultimately could cause harm to human health.
It is a criminal offence to discharge poisonous/ toxic matter into rivers. Industry and Highway Authorities are required to meet standards in order acquire a Permit to Discharge from the Environment Agency. These permits state the levels of permissible discharges, they are not enforced effectively to ensure our rivers are compliant with Environmental Standards.
Where road run-off seeps into the ground the pollutants can get into the water table and the aquifers that, along with river water extraction, supply us with drinking water.
Drinking water is treated before it gets to our taps, but far better if strategies are deployed to ensure the pollutants do not get into our rivers and ground water in the first place. Ongoing research is needed to identify yet to be discovered pollutants, plus regular testing to monitor pollutant levels.
Examples of pollution mitigations include Sustainable Urban Drainage Systems and Vortex Separators, but their use requires legislation and the enforcement of that legislation. Of course human behaviour change could be a significant mitigating factor in reducing the pollutants on the road in the first place, which I have also covered in previous articles.
Safer Driving is a sustainable choice
Road Run Off -what Happens to it
Road transport pollutes our rivers as well as the air we breathe