Road transport pollutes our rivers as well as the air we breathe

In previous Travel and Transport articles for ERA’s newsletters I have referred to the harmful effects of fossil fuel burning vehicles on human health and the environment. In this article I focus on an environmental impact of vehicles that does not come from exhaust pipes and might easily be overlooked.

Previous articles about ERA’s river monitoring project and the health of the River Rother can be read here. They got me thinking about the range of factors that can contribute to pollution in the river, and in particular about road runoff which I have taken as my topic for this article.

What are the sources of the pollutants that flows into our rivers from roads? How do those pollutants negatively impact aquatic life in the river, and plant life along the river banks? What are the potential health hazards for people who swim in our rivers? And what systems are in place to control and mitigate road runoff? Finally, I shall discuss what we as individuals and road users can do to reduce toxic and harmful materials ending up in our rivers and how such behaviour changes can positively impact on reducing harm to the environment.

Some of you may have read articles in the press from the anti-electric car lobby, or should I say pro fossil fuel lobby, arguing that because electric cars are heavier they generate more particulate matter and microplastic from tyre wear, brake wear and road surface wear. To what extent is that true and how come we did not hear the same argument being voiced when HGV max weight was increased to 44 tons in 2010?

According to the Environment Agency the three main reasons for poor water quality in our waterways across England are agriculture and rural land management (31%), the water industry (28%) and urban and transport (13%).

There will be regional variations in these percentages depending on the types of human activities and whether the area is urban or rural. Urban areas are likely to have more road traffic pollution, whereas rural areas will have a higher percentage of agricultural runoff.

What is road runoff?

Road runoff is commonly defined as pollutants from fuel, oil and coolant spills, particulates from tyre and brake wear, and accident debris from vehicles, which all build up on road surfaces, especially in dry periods, plus minute asphalt particles from road surface wear. Contamination resulting from these and other sources such as chemical spills is then washed into nearby rivers when it rains, particularly so when we have periods of heavy rain such as we have recently experienced in November and December 2022 and now as I am writing this in January 2023.

The main way road runoff gets into rivers in rural areas is from roadside ditches and drains. In urban areas surface water from road drainage systems share the same systems as sewage.

The contaminated road runoff can also contain a range of toxic pollutants, such as trace metals, hydrocarbons, chemicals and other organic pollutants which are carried into the river when it rains. These pose a significant threat to river health in severe rain storms. Road runoff can carry over 300 different pollutants which can cause damage both in the short and longer term. In extreme cases, it can cause large numbers of fish to die in so-called ‘fish kills’ (as this study shows).

ScienceDirect’s Chemosphere journal published a paper in 2010 called ‘Runoff pollutants of a highly trafficked urban road – Correlation analysis and seasonal influences’. This outlines a study of the quality of road runoff at a highly trafficked road over a 2-year period, sampling 63 storm events. The study identified concentrations of zinc, copper, lead, nickel and cadmium in both dissolved and particulate form, de-icing salt and dissolved organic carbon. Their sampling was done on a highly trafficked site near Munich with a daily average vehicle load of 57,000 vehicles. The major land use surrounding at the sampling site comprised residential housing, office buildings and a park.

A similar study in Queensland Australia came to the same conclusion regarding the toxic substances contained in road runoff.

For impact on aquatic life, a study by Middlesex University in 2019 on the effects of toxic pollutants from road runoff stated that ‘Oxygen levels can drop to levels that endanger fish as bacteria break down the organic material entering the river, resulting in aquatic mortalities. The consequences of fish dying and riverside vegetation damage extends to other river life such as otters, beavers, king fishers, ducks, coots, moorhens, egrets to name but a few, all of which rely on fish or plants as part of their diet. The demise of aquatic and river bank plants will negatively impact on those species that rely on a healthy river to survive.

Such pollutants also pose a danger to humans (and their dogs) who swim in rivers as well as creating complications for the water companies who extract river water for our drinking water, and farmers who use it for irrigating their crops and for their livestock, all of which can facilitate these pollutants being present in the food chain including the food that we consume every day.

Mitigations

At the planning stage systems can be put in place to reduce road runoff:

·       Sustainable drainage systems have been developed which can be used to improve the water quality before it enters a river.

·       Swales are shallow, broad and vegetated channels designed to store and/or convey runoff and initially remove some pollutants.

·       Filter strips are strips of ground where water running off a site can pass, allowing some or all of it to soak away, some of it may also end up in a Swale.

In a conversation with the Environment Agency, I was advised that if road drainage systems share the same system as sewage it is unlikely that the sewage works filtration can remove all toxic pollutants. I also asked what happens when roads have to be cleaned after road accidents and chemical spills. The response was that emergency services attending do their best to prevent the cleaning residue ending up in road water drainage systems, but it is inevitable some could end up in our rivers.

I also discussed road runoff mitigations with two civil engineers with significant experience in transport infrastructure. They advised that when new roads are built the drainage systems are designed to have sumps in the drains and/or settling ponds. Both of these allow some sediments to settle out of the water before it gets into rivers. However, to be effective these systems need to be cleaned regularly, raising the question of how the toxic sediment is then safely processed.

In our river surveys we record visible debris in the river and along the riverbanks. Litter, casually thrown out of car windows or dropped when out walking, can all too easily be washed into ditches and on into our waterways. After periods of heavy rain the visible litter in and around the River Rother noticeably increases.

Veronica and I do regular litter picks in the Trotton area. On a recent three hour litter pick we collected six bags of litter, much of it consisting of drinks cans and plastic packaging which we also often see in the River Rother or on the riverbank. On this particular litter pick we also collected sixty-plus glass bottles, spirits and wine, in a 30m stretch of ditch. 

 What can we as individuals and road users do to reduce toxic materials ending up in our rivers?

We can reduce the speed we travel, especially when cornering, and avoid harsh acceleration and hard braking - all of which will reduce the amount of tyre and brake particulates generated and left on the road surface. Also it will save us money by using less fuel and reducing brake, tyre and general vehicle wear and tear.

Make sure your vehicle does not leak liquids such as oil, fuel, coolant, and hydraulic fluids, which besides adding to river pollution can also make the road surface slippery. Leaking fluids from your car could cause damage to your vehicle which will lead to costly repair bills.

Try to use your car less, public transport more, and active travel where practicable.

Buy a smaller car, which will have the bonus of a lower carbon footprint as well as reducing particulates caused by tyre and brake wear, and be cheaper to run.

Take your litter home. Don’t let it end up being washed into our rivers - much of the litter we collect could have been recycled.

Report overflowing drains to your local authority: they are responsible for cleaning them. If a drain is overflowing then the sump in the drain will also be overflowing, causing the toxic material within to end up in our rivers.

Prevention is better than cure. When planning applications in your local area are submitted for any type of infrastructure development, for example, look at the plans to see what mitigations such as swales and filter strip are in place to minimise road runoff into your local rivers, ponds, and wetlands.

If we all bought less and consumed less, there would be fewer heavy goods vehicles on our roads.

Hopefully this article has shown why road runoff is a problem and given you some food for thought. Doing all of the above from a standing start probably seems a big ask regarding actions you may be able to take to reduce your personal contribution to the problem, so one thing you could easily ask is what is the one journey a week using a car that we as individuals could most easily give up?

Could you car share with a friend, a neighbour or a work colleague ?