A report says that nearly 200,000 properties in England will have to be abandoned by the year 2050.
It looks at where water will cause the most damage.
Scientists agree that decades of sea level rise are inevitable, but not all properties can be saved.
Sea level rise will put a third of England's coast under pressure.
The author of the report says that it will not be possible to hold the line all along the coast.
"These are the places we are going to hold, and these are the places we aren't going to hold, so we need that honest debate about how we're going to do that and support communities where they are affected."
There is a study in the journal.
The South West is listed as having the highest number of properties at risk of flooding. Increased sea levels increase the risk of flooding on the coast and in estuaries, as well as speeding coastal erosion through larger waves.
For the first time, the study looks at places where the cost of improving defences may be too high. Up to 160,000 properties are at risk of needing relocation because of a conservative sea level rise caused by temperature increases of 2C by century's end, according to a new study. There are between 30,000 and 35,000 properties that are at risk.
The walls and embankments of London are raised in response to sea level rise because there is no limit to how well we can protect ourselves. Sayers told the story to the news on the beach.
Under current funding rules, there won't be money.
The red-and-white-striped lighthouse is not likely to get any more funding for sea defences. Its coast is in a bad shape.
There is a safety barrier across the street after the ground under the bungalow fell into the sea.
The sign says the road is closed. For the past six months, the 77-year-old has been documenting the retreating tarmac.
She sighs and says that it's 3.4 metres now.
There is good reason to watch the erosion. She moved just 50m up the road to a house that was going to fall into the sea. She says it's likely to last until 2030.
The district council decided that Happisburgh shouldn't be protected by sea defences. She points out that large amounts of sand have been dumped on the shore in order to protect a gas terminal.
She says it's a weak and unpatriotic attitude. We need to divert funding to our country because it is so important.
An organisation has been set up to try and get people interested in some new sea defences.
She told me that it was the Save Happisburgh Action Group. A shag is a sea bird who has to fight for survival against impossible odds. That is appropriate for the area.
It is not universally held in the area. She's not the only one.
The sea is strong. Malcolm Kirby is one of the founding members of the Coastal Action Group.
For more than two decades, Malcolm has been involved in finding a solution to the erosion problem in Happisburgh. The owners of homes that were about to fall into the sea were offered market price by the government in order to resettle further inland. He says it's called roll-back.
He says either you commit to spending billions or you don't. In the light of what's happening with climate change and sea level rise, we'll do a properly managed withdrawal and look after the people as we go.
The rest of the UK is being looked at as an example of how to adapt to new things. Along with East Yorkshire, north Norfolk has been chosen to be part of a programme which will look at ideas such as establishing "green buffer zones" between communities and facilitating the "managed transition of communities from high risk land".
The landlord of the pub says that the village will fall into the sea.
All normal commercial transactions stop as soon as the decision is made that there is no defence.
The problem does not end when the properties go over the cliff.
Clive wants to see a mix of relocation and defence to slow the sea's advance.
He saysevitable is a long way off.
The human race created climate change over the last 50 years. Some people on the coast should not have to pay for that.