Bringing the River Thames flood defence walls to life: restorative ecology in an urban estuary
A Thames21 project in collaboration with Kings College London.
In 1957 the River Thames was declared biologically dead, this meant that the water quality was so poor that it could not sustain life. Since then, the river has undergone a massive transformation; though we continue to have issues with sewage pollution, water quality has improved, and wildlife has returned. However, long stretches of concrete flood defense walls on the Thames prevent plant growth and the invertebrates that thrive in healthy riverbank habitats.
This project seeks to boost the biodiversity of the hard walls of the Thames through central London with structures to support plant and invertebrate life,adding to and benefiting the existing wildlife along the river. Six sites between Richmond and North Woolich have been selected to host the living walls. These sites along the River Thames have concrete or sheet piling walls and vary from freshwater, brackish and saline with little or no vegetation.
How a Green Wall works
The ‘wall’ is a grid like structure mounted to embankment just above and below the mean high tide line, containing native plant species such as Gypsywort or Yellow Marsh Cress which are known to thrive on river banks. In between the seedlings, fertile soil cups will allow natural colonisation from seeds carried in the water, by the wind and by animals, ensuring a range of plant species.The walls will be regularly monitored for successful germination and plant growth, which will allow robust comparisons with the previously bare banks.
It is hoped that our use of green walls will help support species that currently have no or little habitat on the Thames, boosting the ecological value of the river in central London, while preserving the flood defense function of the hard surfacing.
The River Thames Green Walls project originated from a research collaboration between Thames21 and King’s College London to look at the biodiversity and potential for ecological improvement along the river through central London. For more information, see: Background to the Green Walls project