Millions living near the coast are likely to be hit by rising sea levels, erosion and storm surges, warns a new study by the Joseph Rowntree Foundation

On Benbecula, they know all too well that rising tides threaten the UK's coastline. For the 1,200 inhabitants of the small, low-lying island in the Outer Hebrides, the sea's encroachment is becoming a serious problem, especially on its western shores.

Impacts of Climate Change on Disadvantaged UK Coastal Communities, a report to be published tomorrow by the Joseph Rowntree Foundation, an influential thinktank, records how local people have seen the coastline retreat before their eyes in just a few years.

The threat posed by erosion has been exacerbated by the fact that the sea has taken material from the island's beaches that is normally used for constructing roads and buildings. But Benbecula is not alone: the report claims that rising sea levels are likely to have a "severe impact" on much of the UK's coastline by 2080.

The authors note that "the total rise in sea levels off the UK coast may exceed one metre, and could potentially reach two metres". They warn that "the frequency of intense storm events is expected to increase and, along with the rise in sea level, to lead to more coastal flooding".

As a result, many of the 30 million people living near the UK's coastline – which has 291 inhabited islands – will need to anticipate how climate change will affect them. "We haven't devoted enough time to debating these issues," said Jeremy Richardson, director of the engineering consultancy URS-Scott Wilson, who co-authored the report.

"Because we're talking about what happens in 2050 to 2080, people tend not to talk about this, but the coast is going to be at the forefront of these climate change impacts. We're not just talking about flooding or drought, but also rising sea levels and an increase in storminess; it will affect a lot of towns, many of which are especially vulnerable because they are isolated geographically."

Climate change threatens to be an additional burden on coastal regions already experiencing major socioeconomic problems. Many have increasingly elderly populations, with younger people forced to move inland to find work. Among Britain's local authorities with the largest proportions of pensioners, all but one are coastal, according to the report.

Each coastal region will be affected differently, it suggests. Winter precipitation is likely to increase markedly on the northern and western coastlines of the UK, prompting concerns that these areas will experience a rise in flooding. The east of England, with its low-lying and soft-sediment coasts, will be most vulnerable to erosion, with towns near estuaries particularly at risk.

Some 17% of the UK's coastline is already thought to be suffering from erosion. Five areas are identified as particularly at risk: south Wales, north-west Scotland, Yorkshire and Lincolnshire, East Anglia and the Thames estuary.

One of the towns that will be particularly affected is Llanelli, on the Loughor estuary in Wales. The inhabitants told the report's authors that they believe many parts of their town could be under water within 50 years. Recent storms have destroyed the Millennium Coastal Path around Llanelli, while sand dunes at nearby Pembrey have disappeared.

Skegness in Lincolnshire is identified in the report as being at particular risk from sea-level rises and increased storm surges. The report warns that the town's problems are compounded by its "predominant architectural style, which consists of largely single-storey dwellings, meaning that residents cannot simply go upstairs to avoid floodwaters. In addition, there is a suspected 'hidden population' living in caravans all year round."

Another town identified as a key concern is Great Yarmouth on the Norfolk coast, which was flooded in 1953. A "near miss" in November 2007, when a tidal surge and high tides resulted in partial flooding, has raised concerns among the town's business leaders that its tourist industry is vulnerable to climate change.

The government has wrestled with the dilemma of how best to defend the UK's coastline for decades. For the last half a century, successive administrations have employed a "hold-the-line" policy – defending the coast through the use of "hard" defences such as sea walls and groynes.

Advocates of such a policy point out that around 60% of the best agricultural land is five metres or less above sea level, while 90% of UK trade comes and goes through sea ports. In addition to being a major tourist destination, the UK's coastline is also home to internationally significant wetlands and habitats for major bird populations. Around 10% of Britain's nature reserves are located near the coast.

Recently ministers have questioned whether maintaining this approach is cost-effective in the long term as sea levels rise. But Richardson said it was vital that the government provided coastal communities with adequate resources to combat the new threats posed by climate change.

"We are an island nation; we live and die by the sea," he said. "Even if protecting the coastline does not make sense in cost-benefit terms, it is vital to our national character and identity."

• The following correction was printed in the Observer's For the record column, Sunday 13 March 2011. In early editions we wrote that the positions of Great Yarmouth and Skegness were transposed on a flood map showing regions under threat and a photograph labelled as Great Yarmouth actually showed the village of Walcott, 21 miles away.