Øresund bridge now set to resist a 10,000-year storm surge

The more than seven million drivers and their passengers crossing the Sound via the Øresund bridge and tunnel each year can now rest assured a storm surge will not leave them stranded along the way. Øresundsbro Konsortiet is protecting the four-kilometre-long tunnel against a surge. When the current projects have been completed in 2025, the tunnel part of the Øresund link will be able to withstand a 10,000-year storm surge projected up to 2050. The Øresund link between Denmark and Sweden was designed to withstand a 10,000-year storm surge when it was first inaugurated in 2000. But climate projections have changed since then. According to new climate models, we can expect to see more frequent and more powerful storm surges. The current projects therefore involve building new dikes and a concrete wall to protect the tunnel stretch of the link.

The storm surge protection will be fully established in 2025

Work to construct the first of several dikes started in summer 2022.

The longest dike will be almost 900 meters long, and it will be built on the Kastrup peninsula of Amager northeast of Copenhagen Airport.

The almost 16-kilometer-long bridge and tunnel connected by Peberholm island are the only fixed link between Denmark and Sweden.

The decision by the board of Øresundsbro Konsortiet to storm-surge protect the four-kilometre-long tunnel as soon as possible was taken in 2021.

By summer 2022, the first row of dikes was under construction. All the sub-projects in the extensive protection project have been planned for completion by 2025.

Øresund Bridge is financing the DKK 60-million project itself.

The many structures being established will have the same service life as the Øresund Bridge itself, namely 200 years.

Increasing risk of storm surges with enormous costs

If the Øresund tunnel were to flood, it could have to close for at least one year. And repairs could amount to as much as DKK 4 billion.

If pay toll booths, electricity supply and railway tracks are flooded, the bridge will have to close. 

The costs of repairs in such a situation would exceed DKK 100 million.

From the beginning of the project, the tunnel was designed to the 'highest protection level', corresponding to a 10,000-year storm surge event.

The climate is changing, and new risks assessments have been made since then.

If Øresund Bridge is to withstand a present-day 10,000-year storm-surge event, the bridge will need considerably more protection than when it was inaugurated in 2000.

Large and small dikes and a long concrete wall

Storm-surge protection of the Øresund link consists almost exclusively of passive flood controls.

In addition to the dikes, several other controls will be introduced.

The four-kilometre-long underground tunnel starts at Kastrup on Amager and ends on the artificial island of Peberholm. 

From Peberholm and for the remainder of the stretch to Sweden, the link continues as a bridge.

All of the storm-surge projects pertain to the tunnel and are on Amager and Peberholm.

Two large dikes will be established. The longest 900-meter-long dike will be on the Kastrup peninsula and will protect the road leading down into the tunnel.

The dike will be established during autumn 2022 and will provide an additional three-metre-high protection against the sea.

The other large dike will be 800 meters long and will be established on Peberholm. Together with a 400-meter-long concrete wall, this dike will secure the road where it runs up onto the island from the tunnel.

Several smaller dikes will be established on the four-kilometre-long, and 160-hectare island of Peberholm . These will secure technical instillations as well as road and railway traffic.

The dikes consist of various material fractions with a core of clay.

The longest dike on the Kastrup peninsula alone will require 10,000 cubic metres of rocks and boulders laid on the outer surface of the dike to protect it against erosion. The rocks will be retrieved from quarries in Skåne, Sweden.

The dikes on Peberholm will largely be built using material dug up on the island itself.

Peberholm consists of dredged seabed material, and since it was established more than 20 years ago, the island has developed its own ecosystem, with around 400 plant species, 30 bird species and more than 500 species of insect.

Using material from the island itself for the dikes will spare the ecosystem from unnecessary disturbances.

Climate projections will continue to change over time. The future will bring new risk assessments identifying new needs.

Øresundsbro Konsortiet has therefore designed the current storm surge projects with built-in flexibility so that the projects can be reinforced in the years to come.

Furthermore, as part of the projects up to 2025, Øresund Konsortiet will carry out risk analyses and preliminary studies to assess how the groundwater affects ramps, railway embankments and toll booths.

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