It is known affectionately as Belgium’s answer to St Tropez – a town once frequented by Frank Sinatra and Marlene Dietrich and which has inspired the pop art of Keith Haring and surrealism of René Magritte, who painted the walls of the town’s casino.

But now the chic, if slightly faded, seaside resort of Knokke-Heist is, in the words of its mayor, Count Leopold Lippens, in a “fight for its life”. The Flemish government, in an attempt to limit the damage to the Belgian coast from rising sea levels, has announced plans for an artificial island of 40 hectares (99 acres) 1.2 kilometres from the sandy beach, to act as a bulwark against the waves. Belgium has, until now, been slow to respond to climate change and its coast has suffered severe damage during recent storms.

Rather than saving Knokke-Heist, however, Lippens and others claim, the plan will create a calm channel of water in front of its beach, perfect for the barges, spewing oil and waste, that travel in and out of the port of Zeebrugge. “We would be an industrial harbour with a kind of open sewer in front of us,” Lippens said. “The island is to be 1.2km from the coast, so the boats would be 330 metres [away]. No one could swim or windsurf. It would be the end of tourism in Knokke-Heist, which would be very sad. That is why we are fighting for our lives.”

Lippens, mayor since 1979, said the municipality’s tourism revenues of €700m a year would be halved should the plans be approved. “We have to beat this,” he said. The 77-year-old has hired specialist lawyers to fight his corner.

The threat of rising waters is not unappreciated by the authorities in Knokke-Heist, a favourite hideout of the Belgian king, Philippe, and popular with artists since the Belgian painters James Ensor and Alfred Verwee captured its vistas on canvas in the early 19th century. The sea is expected to rise by 30cm by 2050 and 80cm by the end of the century. In 2016, Storm Dieter brought waves around two metres high crashing onto the front. About €17m was invested in a rebuilding programme, which included the replacement of 1.2m cubic metres of sand.

Facebook Twitter Pinterest Marlene Dietrich, opening bowling alleys in the town in 1960. Photograph: Alamy

Lippens says studies by the authorities in the Netherlands suggest better solutions. “It is the dredging companies who are pushing for the work to make the island because the Chinese have taken a lot of jobs away,” he said. “In Holland, where the land is much lower than in Belgium, they have studied all the systems, studied the islands, and it would be worse than just using more and more sand on the beaches. That is what they are doing and that is what we want.”

Not everyone agrees. Cathy Coudyser, who sits for the Flemish nationalist party, the N-VA, in the Flemish parliament and on the city council, said Lippens, a member of the Christen-Democratisch en Vlaams party, was playing politics before an October election.

She told the Belgian daily Het Nieuwsblad: “We have explained to Mayor Lippens the plan several times. Still, he continues to send wrong information to the world without blinking, including on the website of the municipality.

“Doing nothing is not an option for Knokke,” she added. “The coast in Knokke is a weak zone, which is severely affected by a violent storm, probably with a lot of damage and heavy flooding.

“Several other options have been studied, such as raising the sea dyke. But then the apartments would disappear behind a concrete wall. That seems to us a much worse solution.”

The Flemish government has already released €8m for the island, which is part of its 2020-26 coastal management plans.