The race to build more riverside property on London’s floodplain has received another boost after a big development on the Greenwich Peninsula was given the green light.

The Financial Times reported on Friday that Boris Johnson has given final approval to an £8.4bn, 12,700-home development that would transform this area of south-east London into a “high-rise urban village complete with film studio”.

Knight Dragon have already begun construction on the project, a 150-acre scheme approved 10 years ago in a more modest form but revived and expanded after the financial crisis.

The report mentions that local residents are concerned the scheme will place unbearable strain on the area’s transport links and that the size and density is out of keeping with Greenwich’s World Heritage Site of 17th to 19th-century buildings close by.

What is not mentioned is flood risk – a factor that, considering climate models, is deemed too minuscule to worry about. The proposed development satisfies this risk criteria – a report on the ‘Strategic Flood Risk Assessment’, drawn up in October 2011, mentions:

“Tidal flood risk is extensive, but at present Greenwich is fully defended against the 0.1% annual probability extreme tide level with climate change to 2107. A breach in the defences, although a low probability of occurrence, would have a high consequence, causing significant flooding of the Thamesmead, New Charlton and Greenwich Peninsula areas of the Borough.”

But is it wise to build on historic floodplain? Surely we should be looking elsewhere in London for safer sites for projects that will help ease the housing crisis.

The website floodlondon.com shares concern that developments such as these are at severe risk from a tidal surge when the Thames Flood Barrier nears the end of its working life in the middle of this century.

“Perched on the very tip of the Greenwich Peninsula, the O2 Arena finds itself ideally located on a nice sharp bend in the river where it is likely to take the full brunt of the surge as it careers into the bank, much like a racing car taking a corner too fast. The North Greenwich tube station just across the road will prove to be a great asset at this point as it funnels the water into the Jubilee Line.”

Before the Thames Barrier was built this part of the river has seen some catastrophic flooding.

Since the flood of 1953 measures, including the Thames Barrier, were put in place to stop this flooding. The Environment Agency has outlined a range of options for the future of the Thames Estuary flood defences. None are particularly cheap. As a minimum, the EA estimates that the cost of maintaining the defences until 2035 will be around £1.5 billion, with an additional £1.8 billion needed to repair and upgrade the defences until 2050. Particular bits of marshland could also be set aside to store tide waters.

The EA estimates a new barrier could cost as much as £7 billion, though that figure could go up if conditions change significantly as the climate changes.

Greenwich Peninsula and another project, City in the East, which was announced last month will need proper flood protection and planning. I wonder if planners are as willing to invest in these defences as they are at making a tidy buck developing these riverside schemes. And do our politicians have the appetite to drive the legislation through?

The problem is that if the climate change does bring greater rainfall and an unprecedented sea-level rise it is the people living in these properties that will be faced with the problem of ever-increasing costs to fight off the risk of inundation.