A government study says the cost of flood damage could rise from about £1bn a year to £20bn by 2080 in the most extreme scenario.
The barrier is one part of the Thames' flood defences
So why are we still building homes and businesses on floodplains?
Claire Foy-Smith looks at the Thames Gateway, one of the largest development schemes and set in the Thames basin.
The Thames Gateway is one of four key areas earmarked to burst the boil of housing demand swelling in more traditionally-desirable areas.
It will see a massive build across London and the south east of England during the next 20 years.
But in choosing the gateway, planners are asking people to set up home in some places at risk from flooding.
It comes at a time when reports and projections point to an increasing risk of flooding for the UK and spiralling prevention and clean up costs and when images of inundated homes and streets turned to rivers are a regular in news reports.
Academics warn strategic thinking is vital, and environmentalists question whether anyone will actually move in.
But the planners say a "holistic" approach to flood prevention will ensure success.
Predictably perhaps, Alex Nixon, lead environmental officer at the Thames Gateway London Partnerships, is confident.
"If you plan sensibly you can lessen the risk," he said. "You can only give people reassurance if you have positive on-the-ground action."
He says this holistic approach to planning will replace the old, "expensive and unsustainable " high walls approach where "everything stays dry".
Instead, flood-prone areas will see precautions like a green bund placed between houses and the river and tiered flood defences that allow the river to rise along steps.
Defences can only go so far
"People have this nightmarish vision of a wall of water coming down the Thames," he said.
But, he said, that is not the issue. Flood defences will need capacity to deal with fluvial flow - the run off from the many rivers feeding into the area as well as tidal flow.
At the largest single development site - Barking Reach - houses will be built on land raised by covering contaminated land with soil.
Gateway development will take place on a "green grid", open spaces including fields and parks that can be flooded to manage water flow.
The project will see 120,000 new homes built before 2016, many on brownfield sites.
Further development will come in greater London, Kent and Essex.
The gateway is no virgin desert. Environment Agency figures say 1.25m people live in the four areas and there is £80bn of commercial business - infrastructure that already needs flood protection.
A partnership of organisations is working to reconcile the flood threat with the housing need.
The Office for the Deputy Prime Minister, is talking to groups including the Environment Agency, Thames Gateway London Partnership, the London Development Agency, and Association of British Insurers.
Homeowners fear increased flooding
Rachel Collins of the Environment Agency said the project meant an increasing number of people would be in the flood risk area.
But the work is an opportunity to put flood risk management in place at the earliest stage.
Frequent flooding in the face of global warming has meant increasing insurance claims by people affected and an inability to secure cover for some.
Jane Milne of the Association of British Insurers said sensible building depended on three factors - maintaining existing defences, ensuring future ones - like a new barrier and systems along the estuary - and building under regulations with the right materials.
While her organisation stands against building on flood areas nationwide, she added: "In the South East there is such a demand for housing - we would still say we need to avoid the worst risk areas and we need to put the investment in place before we go in.
"We wouldn't want to stand in the way of house-building going on because people need homes."
Despite the optimism and efforts, environmentalists remain to be convinced.
Friends of the Earth climate campaigner Roger Higman said he doubted people would be tempted to an area beyond the existing barrier with a widening river, when south east England is sinking and sea levels rise under global warming.
Building near the river posed a flood risk but building further away in the wider Thames "scenic" areas created further environmental problems, he said.
Referring to a Californian desert development that failed to attract many settlers, he said: "Whether there is the demand to live in that part of the South East, still the real pressure will be on the land within London.
"The government might have grand plans but actually it will get a pocket of housing here and a pocket of housing there."