Swathes of low-lying Norfolk could regularly flood within decades, claims a new report.

US think tank Climate Central says improved mapping of the Earth's contours provides a clearer view of flood risk than previous satellite data, which made some areas of land look higher than they really are.

It says when combined with predicted sea level rises, its new digital elevation model (DEM) shows many more areas are at risk of flooding than was previously feared.

MORE: Would-be MPs promise billions to shore up flood defences

In East Anglia, the area of the Fens which would lie below the high tide mark is shown stretching south from King's Lynn to Cambridge, and north through to Lincolnshire Fens.

Low-lying Lynn, Wisbech, March and Chatteris are included, along with parts of Downham Market.

Parts of the north Norfolk coast, northern broads and the Yare and Waveney valleys are also at risk, along with areas of the Suffolk coast.

Climate Central says worldwide, some 150m people will be living in areas below the high tide line by 2050. Around 3.5m of them are in the UK.

"The levees, seawalls and other defences and accommodations currently protecting tens or hundreds of millions of coastal-area residents globally point to the potential for protecting ever-larger areas as seas rise," says Climate Central's report, published in the journal Nature Communications.

"At the same time, current coastal defences should not be assumed adequate to protect against future sea levels and storms without continued maintenance and, likely, enhancement.

"If our findings stand, coastal communities worldwide must prepare themselves for much more difficult futures than may be currently anticipated."

A report by academics at the University of East Anglia, published last week, said joined up thinking was needed to plan for the impacts of climate change on coastal regions.

MORE: Norfolk village ranks worst hit by coastal erosion in UK

"Climate change poses a particular challenge due to the significant

uncertainties that exist over its timing, magnitude and impacts," its foreword said. "These impacts, such as the potential increase in flood risk, are likely to have widespread and disastrous effects without the adaptation of human and natural systems."