Project started
1 March 2014
Project status

London's rivers are a vital habitat for wildlife and a great resource for people, yet they are degraded by poor habitat and pollution. 

Why we are improving London’s rivers

Urban rivers can provide important opportunities to restore nature to cities. The upside of years of neglect and modification, including the burial of many streams and rivers, is that the opportunities to restore from such a low baseline are considerable. In addition, they are often lined by semi-connected open spaces that, with strategic planning, can be linked as a network of interconnected wildlife sites. Another significant reason to focus on freshwater ecosystem recovery is that freshwater systems, compared to other systems, are disproportionately biologically rich. The 0.8% of our planet that is covered in freshwater is home to more than 10% of all known animal species.

In London, ZSL works with multiple partners to restore rivers. Since 2000 approximately 39 km of river, 6% of the total length of rivers in London, has been restored but we need to do more and faster. The evidence is clear, when rivers are restored wildlife returns. In addition to benefiting wildlife, restoring rivers helps improve water quality, makes the city more resilient to the effects of climate change and the threat of flooding, and supports the well-being of local people.

"I’m a local resident and I noticed there was some pollution in the river and I’m quite interested to find out about the water quality and also the ecology and how we can improve the water quality of the river" - Karolina Allu, Citizen Science Volunteer


Community science 

The Riverfly Monitoring Initiative

The Riverfly Monitoring Initiative (RMI) is a UK wide citizen science scheme that is used to detect pollution events and learn about long-term trends on river health. ZSL act as the London Riverfly Monitoring Hub, working with project partners to support the development of RMI schemes on rivers throughout the Greater London area.

The RMI is a scheme created by The Riverfly Partnership which is a dynamic network of organisations working together to protect river habitats for wildlife and to improve water quality. ZSL are an active board member of The Riverfly Partnership.


Sewage pollution and the outfall safari

Much of Greater London is serviced by two separate drainage systems. One collects rainwater and flows directly into our rivers, and the other takes foul wastewater from buildings to sewage treatment works to be cleaned before being released into a river.
Mis-connections between the two drainage systems, often caused by inexpert plumbing, results in pollution pouring directly into our rivers via drains known as outfalls.


Until recently, there has been no systematic surveying of outfalls in urban rivers to identify pollution and notify the relevant authorities. The Outfall Safari is a citizen Science method devised to address this evidence gathering and reporting gap. It was created by the Citizen Crane project team in partnership with staff from Thames Water and the Environment Agency and is. regarded by the Environment Agency as best practice.

The Outfall Safari methodology encompasses the following activities:

  • Record and map the dry weather condition behaviour of surface water outfalls in urban rivers
  • Geo-locate and photograph sources of pollution and report them to Thames Water and the Environment Agency
  • Recruit more volunteers to the work of River Catchment Partnerships to help deliver the objectives of catchment management plans 
  • ZSL has led on the most comprehensive survey of London’s rivers undertaken in recent years. Findings indicate the true scale of the problem of sewage and other pollutants being sent into rivers by homes and business across London due to misconnected plumbing.

Read our report on tackling pollution in London's rivers

Please make sure your own home is not polluting your local river. Find out more.

ZSL are active members of the Regional Misconnections Group and work in partnership with organisations across the region to help tackle this damaging problem for London’s rivers.

  • More than 10% of all known animal species can be found
    in the 0.8% of our planet that is covered in freshwater.
  • A guide to running an outfall safari

    Since 2016, Outfall Safaris have taken place on over 250km of river in Greater London and the approach has been adopted by other environmental NGOs across the UK. To support the spread of the Outfall Safari method and drive improvement in urban water quality across the country, ZSL and The Rivers Trust have created the Outfall Safari guide and package of resources to help environmental NGOs and water companies’ setup their own Outfall Safari projects.

    Read the guide first to understand how the methodology works and use these resources to help with the technical aspects of setting up and running the Outfall Safari:

    We would really value hearing from those that have used the guide and run their own Outfall Safaris. Please contact us at with your feedback, ideas and any general questions that you may have. 

    The Citizen Crane project

    The Citizen Crane project is a major citizen science initiative on the River Crane in West London. The project is led by ZSL, Friends of River Crane Environment, Frog Environmental with support and guidance from the Environment Agency, Thames Water and The Crane Valley Partnership
    All the project reports can be viewed here.

    River restoration and urban wetland creation 

    ZSL are members of the London River Restoration Group and are Biodiversity and Water Quality theme leads for the Smarter Water Catchment programme on the Crane.  Much of our work is concerned with evidencing the impact of constructed wetlands and other river restoration interventions.

    You can find our guidance on the design of Urban Wetlands, produced in partnership with London Borough of Enfield and The Greater London Authority in this handy guide.  


    Project information


    • Citizen Zoo
    • Crane Valley Partnership 
    • Environment Agency
    • Frog Environmental
    • Friends of Ickenham Marshes
    • Friends of River Crane Environment
    • Friends of Yeading Brook
    • Greater London Authority
    • Kingston University
    • London Wildlife Trust
    • London Borough of Enfield 
    • London Borough of Harrow 
    • London Borough of Hillingdon
    • London Borough of Richmond 
    • The Riverfly Partnership
    • South East Rivers Trust
    • Thames21
    • Thames Water
    • Friends of the River Roding
    • Vision RCL
    • Middlesex University

    Kindly funded by:

    • City Bridge Trust
    • Thames Water
    • Greater London Authority
    • Environment Agency

    If you would like any of the reports published by ZSL's London's Rivers Team, then please contact us at