Road Run-off

Road Run-off

Tracy&James | Sunday, 4 February 2024

This week there have been a number of news articles about pollution from roads entering our rivers and water courses. I hadn't previously realised that this pollution was ranked the third most damaging source after agriculture and sewage. The articles predominantly covered England and in particular mentioned the a river near to where we used to live, the River Lambourn, a chalk stream, in Berkshire. The Lambourn's crystal clear water winds through Welford Park, before passing underneath the M4 motorway and at that point it can be clearly seen that the river bed is coated with a brown and murky 'gunk'. Local campaigners have taken samples of this and found high levels of pollutants.

The article reported that National Highways has a statutory responsibility to make sure that discharges from its network do not cause pollution. It said this outfall had been assessed as "low risk" and was not in line for any mitigation measures. The Lambourne is a tributary to the River Kennet so this is a serious concern for anglers and other users of the rivers. This article clearly showed the evidence of significant pollution and yet nothing was being done to mitigate the run-off. Considering the M4 is one of the UK's busiest motorways, then this 'gunk' will only increase and will probably spread throughout the river.

Heavy rain washes over roads picking up a toxic mix of oils, chemicals and particles of tyre rubber and runs-off to the nearby water courses. In England the road network has more than 18,000 outflows or drains. Apparently only some of these outflows are not monitored so the pollution is largely unchecked by the English Environment Agency. Instead local people have been doing their own testing and found micro-plastics from tyres, heavy metals from brake pads, toxic chemicals like arsenic and other carcinogenic compounds and hydrocarbons from emissions that wash off the tarmac. There's also general rubbish and waste discarded on the roads that are washed away. All resulting in damage to the flora and fauna in and around the water course.

UK roads are managed by National Highways who monitor these outflows, or at least some of them. They have identified 1,236 locations that are "potentially high risk" and expects that after verification only about 250 will actually be "high risk". Under its current plans only about 30 of those high-risk sites will have mitigation in place by the end of 2025. One of these is just off the A38 in Devon where in 2019 a reed bed was built, costing £2.5m, to filter run-off from the busy roadbefore entering the nearby lake in Stover Country Park. There are signs that the flora and fauna around the lake is starting to recover however there is still heavily polluted silt that sits on the bottom of the lake that will need dredging.

There are more articles from the last few years about this problem, particularly around London. Environmental charity 'Thames21' has launched an online map to show where contaminated rainwater from roads is polluting rivers in London. The map, sponsored by the Mayor of London, Transport for London and the Environment Agency, highlights more than 280 miles (450km) of London's roads that pose a “high risk of causing road run-off”. Roads where heavy goods vehicles regularly apply their brakes were some of the worst affected. Suggested mitigation was to introduce roadside filter drains, grit separators and storm-water filters.

This article made me wonder about the extent of the problem in Wales and whether it was something being monitored by the Natural Resources Wales. So I started researching...

In Wales there are 22,000 miles (35,405km) of road, including almost 2,800 miles (4,506km) of motorway and A-road. I wasn't able to find the number of outflows or drains but did find a report that most people live within 2.6 miles of a road system in Wales. We live near two rivers and both have the busy dual-carriageway intersecting them. I can only assume that the run-off from this road goes straight into these rivers.

The Highway Authorities responsible for road drainage are the Welsh Government for motorways and major trunk roads and Local Authorities for other roads. Sadly as I write this, I have not been able to find anything about the extent of this pollution problem in Wales.Interestingly even though I found little about Welsh rivers, I did find many articles about this problem across the World. Though what is clear is that addressing road run-off is crucial for safeguarding our waterways and maintaining ecological balance and I will endeavour to research more.

Whatever you are doing this weekend, tight lines,



PS - the photo is the river near to where we live as it flows past Rhuddlan Castle.