Chalk Streams

What is a chalk stream?

Chalk streams are one of the rarest freshwater habitats on Earth, and England is home to approximately 85% of them. Found mainly in the south and east of the country, chalk streams are fed by groundwater making the good management of the chalk aquifers (stores of water in porous rock) essential to achieving good ecological health of chalk streams.

Watch a video explainer on X (Twitter) for a quick introduction to chalk streams.

What are the issues facing chalk streams?A tranquil stream flows gently through lush green foliage, reflecting sunlight on its surface under a clear blue sky.

Chalk streams have been badly damaged over many years through over abstraction of water, pollution, and poor management of their channels, floodplains, and catchments. The 2019 water framework directive classification results showed that only 17% of chalk streams meet ‘good ecological status’.

What action are we taking?An illustrated landscape with a river, trees, and buildings, highlighting collaboration among various organisations for water management.

The future of chalk streams is dependent on action by everybody: government, regulators, water companies, farmers, and landowners. We’re making progress, but there’s a lot more to do. Together with our partners, we have a plan to restore chalk streams and improve their resilience to climate change.

A tranquil, clear stream reflects lush green trees and grass, surrounded by foliage.The strategy sets out actions and recommendations for government, regulators, and the water industry on water resources, water quality and habitat restoration and management. This is the ‘trinity of ecological health’. The case studies below show some examples of our work.

The existing chalk stream strategy can be found on the Catchment Based Approach website. To open the strategy document from here, follow this link.

Case studiesA person taking a water sample in a clear stream, surrounded by lush greenery and yellow wildflowers under a partly cloudy sky.

Blog: Plant surveying on the River Mimram

Every June to September, Environment Agency monitoring officers conduct surveys of aquatic plant life (known as macrophytes) to determine the health of our riverine ecosystems.

Read Elodie's blog.

A muddy stream flows through a wooded area, bordered by green grass and fallen logs.Working to Improve chalk streams

The Lincolnshire chalk streams have helped shape the Lincolnshire Wolds landscape over the past 10,000 years. Over the last 10 years, we have worked with partners on projects that create and improve these habitats.

Managing in-channel Vegetation and Fallen Trees in Chalk Streams

Vegetation, be it on the riverbanks, at the water’s edge, or in the river channel, is a natural and important part of how chalk streams function. In-channel vegetation helps the river by:

  • Protecting the channel bed and banks from excessive erosion.
  • Creating flow diversity to encourage varying habitats for aquatic species.
  • Helping to keep the river resilient against low summer flows to protect fish.
  • Stabilising depositional areas (helping trap sediment), creating in-channel features such as vegetated berms (small raised areas).

There is legislation in place that protects river environments and their wildlife, so if it is judged that there is no immediate flood risk, it is best to leave vegetation in the channel for it to naturally vary in abundance with the seasons. Removing vegetation in the wrong way can:

  • Harm habitats for birds, fish, and water voles.
  • Reduce the water’s dissolved oxygen levels, potentially harming aquatic life.
  • Mobilise silt which can smother the gravel bed, limiting the opportunity for fish spawning and habitat for invertebrates.

Trees that have fallen into the channel are also important features in chalk streams, they create flow diversity and encourage variation in steam shape. They also create areas of scour to clean the gravel bed, and refuge areas for fish and habitat for many species.

If the fallen tree in the channel isn’t causing a flood risk, isn’t a safety hazard, and doesn’t block navigation, it’s best to leave it in place. If it must be moved, tying it to the riverbank instead of removing it completely helps keep its benefits for wildlife.


What is a chalk stream?

Chalk streams are one of the rarest freshwater habitats on Earth, and England is home to approximately 85% of them. Found mainly in the south and east of the country, chalk streams are fed by groundwater making the good management of the chalk aquifers (stores of water in porous rock) essential to achieving good ecological health of chalk streams.

Watch a video explainer on X (Twitter) for a quick introduction to chalk streams.

What are the issues facing chalk streams?A tranquil stream flows gently through lush green foliage, reflecting sunlight on its surface under a clear blue sky.

Chalk streams have been badly damaged over many years through over abstraction of water, pollution, and poor management of their channels, floodplains, and catchments. The 2019 water framework directive classification results showed that only 17% of chalk streams meet ‘good ecological status’.

What action are we taking?An illustrated landscape with a river, trees, and buildings, highlighting collaboration among various organisations for water management.

The future of chalk streams is dependent on action by everybody: government, regulators, water companies, farmers, and landowners. We’re making progress, but there’s a lot more to do. Together with our partners, we have a plan to restore chalk streams and improve their resilience to climate change.

A tranquil, clear stream reflects lush green trees and grass, surrounded by foliage.The strategy sets out actions and recommendations for government, regulators, and the water industry on water resources, water quality and habitat restoration and management. This is the ‘trinity of ecological health’. The case studies below show some examples of our work.

The existing chalk stream strategy can be found on the Catchment Based Approach website. To open the strategy document from here, follow this link.

Case studiesA person taking a water sample in a clear stream, surrounded by lush greenery and yellow wildflowers under a partly cloudy sky.

Blog: Plant surveying on the River Mimram

Every June to September, Environment Agency monitoring officers conduct surveys of aquatic plant life (known as macrophytes) to determine the health of our riverine ecosystems.

Read Elodie's blog.

A muddy stream flows through a wooded area, bordered by green grass and fallen logs.Working to Improve chalk streams

The Lincolnshire chalk streams have helped shape the Lincolnshire Wolds landscape over the past 10,000 years. Over the last 10 years, we have worked with partners on projects that create and improve these habitats.

Managing in-channel Vegetation and Fallen Trees in Chalk Streams

Vegetation, be it on the riverbanks, at the water’s edge, or in the river channel, is a natural and important part of how chalk streams function. In-channel vegetation helps the river by:

  • Protecting the channel bed and banks from excessive erosion.
  • Creating flow diversity to encourage varying habitats for aquatic species.
  • Helping to keep the river resilient against low summer flows to protect fish.
  • Stabilising depositional areas (helping trap sediment), creating in-channel features such as vegetated berms (small raised areas).

There is legislation in place that protects river environments and their wildlife, so if it is judged that there is no immediate flood risk, it is best to leave vegetation in the channel for it to naturally vary in abundance with the seasons. Removing vegetation in the wrong way can:

  • Harm habitats for birds, fish, and water voles.
  • Reduce the water’s dissolved oxygen levels, potentially harming aquatic life.
  • Mobilise silt which can smother the gravel bed, limiting the opportunity for fish spawning and habitat for invertebrates.

Trees that have fallen into the channel are also important features in chalk streams, they create flow diversity and encourage variation in steam shape. They also create areas of scour to clean the gravel bed, and refuge areas for fish and habitat for many species.

If the fallen tree in the channel isn’t causing a flood risk, isn’t a safety hazard, and doesn’t block navigation, it’s best to leave it in place. If it must be moved, tying it to the riverbank instead of removing it completely helps keep its benefits for wildlife.


Page last updated: 11 Nov 2025, 02:47 PM