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.

• An important transport corridor for society

  Many passengers using Copenhagen Airport in Kastrup come from Sweden via the Øresund Bridge.

   

  With the establishment of the Fehmarnbelt link. the Øresund Bridge will become part of a direct link between Scandinavia and Europe. Furthermore, the Øresund Bridge is crucial in ensuring  rapid  deployment of emergency services between Sweden and Denmark. 
  

  Øresund Konsortiet categorises the Øresund Bridge as a critical infrastructure corridor. It is therefore important to eliminate even the tiniest risk of a storm surge closing down the tunnel.

   

  

   

  "There are many societal aspects at play here," said the project manager, Christian Tolstrup.

   

  "Many airport customers come from Sweden via the Øresund Bridge. And when the Fehmarnbelt link has been established, the Øresund Bridge will become part of a direct link between Scandinavia and mainland Europe," he said.

   

  Storm surge protection of the Øresund tunnel on the Kastrup peninsula will also provide protection for Kastrup railway station, which would otherwise be exposed to water surging up from the coast during a storm surge.

   

  Finally, Denmark relies on rapid emergency response from Sweden in the event of major accidents.

• Storm surge protection for DKK 60 million

  The budget for the storm surge protection of Øresund Bridge was drawn up before increasing inflation rates and rising freight and materials prices set in.

   

  However, Øresund Konsortiet still expects the budget to hold.

  Øresund Konsortiet will pay the full costs of protecting the Øresund tunnel against storm surges.

   

  The DKK 60 million expenditure will be recovered concurrently with the other costs of establishing and operating the bridge.

   

  Øresund Konsortiet expects the costs of establishing the Øresund Bridge to be recovered through user tolls by 2050.

   

  Specific models have been set up as part of the project to allow for minor changes in the material fractions used, so that materials can be procured that do not need to be transported over long distances. This is one way to ensure the project stays within budget.

   

  Øresund Konsortiet does not expect the costs of operating the bridge to increase because of the storm surge protection project.

• Directives and other legislation

  The part of the project already underway is on property belonging to Øresund Bridge.

   

  Some of the future sub-projects will be carried out in cooperation with owners of the neighbouring property.

  The decision to establish storm surge protection for Øresund Bridge was agreed by the board in 2021.

   

  The longest of the dikes will be established from summer to autumn 2022, and a building permit has been obtained from Tårnby Municipality to build in the rural zone.

   

  The dike is located in a resting and breeding area for a number of birds and animals covered by the EU Nature Directives. It is also a Natura 2000 site. This means that a building permit is required from the municipality.

   

  The project also obtained authorisations from the Danish Coastal Authority in accordance with the Danish Coastal Protection Act, the Danish Coastal Habitat Order and the Danish Environmental Assessment Act.

   

  Because the building site is also an airport approach zone for Copenhagen Airport, the preliminary work before actual construction has been intense.

   

  In addition to the above, Øresund Bridge is collaborating with several other neighbours.

• Early dialogue with all parties is crucial

  Øresund Konsortiet does not like to talk about barriers but would rather talk about what they have learned and are still learning.

   

  In this respect, dialogue with neighbours, consultation parties and their consultant is key.

  Øresund Konsortiet therefore entered into dialogue with its neighbours already before commencement of the formal authorisation process with the authorities.

   

  This has been instrumental in parrying off resistance and unforeseen complications.

  The consortium also prioritised early dialogue with their consultant and main contractor.

   

  Increasing fuel and freight prices could have become a challenge for the project.

   

  However, because of the dialogue with the contractor, it was possible to make minor changes to the material fractions used.

   

  This meant that materials could be sourced closer to the construction site, thus reducing transport distances.

   

  Furthermore, some materials will now be recycled.