The agency said it is prepared in case sea-levels rise faster than expected
The Thames Barrier will protect London from flooding until 2070, the Environment Agency has said.
A new study into London's flood defences found the barrier should work for 40 years longer than expected.
The nine concrete barriers in Woolwich Reach, south-east London, will need upgrading by 2035. By 2075, a new barrier should be built at Long Reach.
The study was based on a worst case climate change scenario with sea-levels rising to 2.7m (8.9ft).
The Thames Barrier, built in 1982, protects 45 sq miles of the capital which is at risk of flooding.
The future of the Thames Barrage and other flood defences for the capital were also outlined in plans which looks into managing flooding until 2100.
If rising sea levels destroy wildlife habitat new and alternative intertidal habitats will be created for them, the plan said.
Dr Paul Leinster, chief executive of the Environment Agency, said the launch of the study would reassure more than 1.25 million people who live in the Thames flood plain.
"Rigorous study and scientific research into the estuary, the defences, climate change and our options for the future, have culminated in a plan that will safeguard the Thames estuary, and the people, buildings and natural habitats that make this area so unique."
"If over time sea levels are found to be rising faster then expected then we are already prepared and have identified the necessary solutions."
A consultation will be held on the draft plans before they are submitted to the government in 2010.
The barrier will protect the capital for at least another sixty years.
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