‘Huge problem’ of 70,000 barriers in UK rivers mapped out

More than 70,000 weirs, dams and other river barriers have been mapped across the UK, as conservationists warn they are a “huge problem” for wildlife and pollution.

Weirs, concrete dams, underwater gates and other barriers – many of which are “old, redundant” installations that serve no practical purpose – make it difficult for fish and other wildlife to migrate, create areas of concentrated pollution and affect the overall health of the habitat, WildFish said.

A new database compiled by the environmental charity reveals there is an average of one manmade barrier for every 2.5km (1.5 miles) of waterway across 150,000km (93,000 miles) of rivers across Britain.

These manmade river obstacles are eight times more prevalent than natural barriers such as waterfalls, which only occur around once every 20km (12 miles) on average, WildFish said.

Meanwhile, data on barriers in Northern Ireland is scarce, with less than 100 obstacles recorded on the country’s thousands of kilometres of rivers.

Barriers can damage the entire river ecosystem, with 674 rivers in England failing to achieve good ecological status in 2023 due to blocks to fish migration, the charity said.

River blockages are a driving factor in declines for four of the seven British freshwater species that are at risk of extinction – Atlantic salmon, European eel, allis shad and twaite shad.

But when barriers are removed, rivers can quickly restore their flow and fish return, WildFish said.

The charity is calling for Government action on removing barriers where possible to help restore rivers and wildlife.

WildFish data analyst Daniel Nixon said: “River barriers have long been a huge problem for wildlife, pollution, and river health, yet the issue has received little attention – perhaps due to a lack of comprehensive data.

“WildFish’s database now reveals the true scale of the problem, with more than 70,000 barriers mapped across the UK.

“While the number of barriers is overwhelming, there is also real hope: when unnecessary barriers are removed, rivers typically respond quickly, with river flow restoring and fish returning to previously inaccessible reaches.”

The charity said the biggest hurdle to removing weirs, culverts or other barriers is planning and legal permissions which can take months or years to secure, with go-ahead required from organisations such as the Environment Agency, councils or internal drainage boards.

But where removals do go ahead, the barrier can be gone in a matter of hours, often just for the cost of hiring a digger or jackhammer.

Janina Gray, head of science and policy at WildFish, said: “While dams and flood defences are often essential infrastructure, there are many cases in which old, redundant barriers are serving no practical purpose yet still have a huge negative impact on the entire river ecosystem.

“Identifying removable barriers like unused culverts and weirs will allow our rivers to flow more freely than they have in decades.”

WildFish hopes the database – which it says is the most complete inventory yet of the barriers across UK rivers – will raise awareness of the issue and help identify redundant barriers to improve river health.

A typical example on the map is a weir – a small dam to regulate river flow – at the end of Ennerdale, in the Lake District, which maintained water levels when the lake was used as a reservoir.

It is now a redundant structure that blocks fish such as the migration of Atlantic salmon, sea trout, brook lamprey and European eels, Dr Gray said.

She added that fish such as Atlantic salmon make migrations of more than 1,000 miles, but “each and every barrier makes this already difficult journey even harder”.

“Removing redundant barriers is an easy conservation win to unlock our rivers and help restore their natural ecosystems,” she said.

“Where barriers cannot be removed fish passage must be ensured – as all species of fish need to move freely within rivers to complete their lifecycles.”

An Environment Agency spokesperson said: “Physical barriers can interrupt the natural flow of rivers and make it harder for fish such as salmon, eel and shad to reach the places they need to complete their lifecycles.

“The Environment Agency recognises the scale of the task to tackle barriers to fish and eel migration and working as part of the Great Yorkshire Rivers Partnership we have removed over 100 barriers so far.

“We know there is more to do to improve river connectivity across our waterways and as part of our partnership work we aim to remove thousands of barriers across the country within the next two decades.”

Published: 23/05/2026 by Radio NewsHub