Physical Modifications

Over thousands of years, people have made changes to the physical structure of rivers, such as altering their course and installing flood defences and weirs.

Human changes to rivers - such as building weirs, reservoirs, and straightening channels - have brought certain benefits, including improved navigation, flood protection, water supply and power generation. But these modifications have also caused significant ecological damage.

Weirs block fish migration and spawning, while straightened channels reduce habitat diversity, harming invertebrates, fish and predators. In our catchments 29% of rivers fail to reach good ecological status due to changes in shape and flow from physical modifications.

Reservoirs and Flow Disruption

Reservoirs like Gouthwaite on the River Nidd, alter natural flow, interrupt sediment transport and restrict wildlife movement.

Restoring River Health

Where structures are no longer needed, rivers can be restored. Removing weirs improves habitats and fish passage - as seen in the Reconnecting the River Laver project near Ripon featured below, and as is being currently addressed in our Mid Swale Tributaries project.

When removal isn’t possible due to water supply needs or costs, impacts can still be reduced. Solutions include installing fish passes, creating in-stream habitats and restoring channel diversity to support healthier ecosystems.