The Metro has been designed for climate change

In 1992, it was decided to establish a tram, light rail or a metro system to connect the airport and the future Ørestad district with downtown Copenhagen and Frederiksberg. Arguments for choosing the metro included that it would attract more passengers because of its high speed, frequency of departures, reliability and safety, as well as the argument that it would be the best solution from an environmental perspective. In 2012, a total of 54 million passengers used the Metro. This corresponds to more than 1 million passengers per week.

If the metro system is flooded, worst-case implications include breakdown and material damage. For example, if saltwater reaches any of the technical installations, this could lead to prolonged downtime and significant financial losses. Therefore, Metroselskabet has been working with climate change adaptation since planning and dimensioning the first metro in 1993-1995.

These climate change considerations, which were included from the very onset of planning, combined with subsequent experience, have now been summarised into an full climate change adaptation strategy. Metroselskabet's climate change adaptation strategy supports the practice of including climate change adaptation early on in the planning and dimensioning phase, so that afterwards only minor ongoing adjustments are required.

"The IPCC's forecasts have changed over time. The basis of calculation, e.g. with regard to storm-surge events, therefore changed in the period between the design of the first metro and the design of the new metro, Cityringen, which is currently under construction. For example, the mean water level forecasts have gone from 48cm at the time of designing the first metro, to 1m at the time of designing the Nordhavn branch. The changed basis of calculation and the expected more powerful storms mean that the height at which to place platforms and shafts has increased over the years," explained Lillah Lucie Emmik Sørensen, who is environment and authorities coordinator at Metroselskabet.

Although recent years have seen a greater number of dramatic events, only on a couple of occasions has Metroselskabet have had to deal with water on stairs and in entrance halls, and at no time has there been water in the actual tunnels. Consequently, at two of the metro stations, drainage grates have now been improved for better drainage of the main stairs. The goal is for the Metro to be completely dry.

"The City of Copenhagen allows for 10cm of water at ground level in the event of cloudburst, so if we make sure we are 10cm above the surrounding ground level, we should be able to keep the Metro dry. However, it's not as simple as that, because when the sewer systems are unable to take in all of the water, things tend to go wrong,"

Lillah Emmik Sørensen continued.

"Another impact that we hadn't counted on is that when busses continue to run during a cloudburst, they actually cause a wave effect that we need to add to our calculations. For example, during the recent cloudburst in 2011, the bus traffic at Nørreport metro station caused a wave effect and more water accumulated around metro entrances than had been anticipated. We have therefore improved the pumping capacity at Nørreport to take account of the fact that the water tends to accumulate in certain areas because of the traffic,".

Every metro station design has been specifically calculated on the basis of its unique location in the city. As a basis for the calculation of cloudburst events, Metroselskabet has chosen a 2000-year event; i.e. an event which has a 5% likelihood of occurring within the lifespan of the metro (100 years). On the basis of these calculations, the levels at which to place the individual platforms and shafts were calculated.

"In the event that a Sydhavn branch becomes reality, we have already looked at each station in relation to future cloudburst and storm-surge forecasts. We have assessed that the stations should to be placed at different levels, between three and five metres, in order to safeguard the fixed installations against a 10,000-year storm-surge event.
Metroselskabet is in ongoing dialogue with the City of Copenhagen, co-owner of the metro company, about plans for overall protection of Copenhagen with sluices and dams.

"If these plans become a reality, they will give us an entirely different basis for planning and designing the metro systems, and we would, for example, not have to raise the ground level to above three meters in the new districts in Nordhavn. However, the establishment of harbour protection lies 30-40 years ahead, which is too long for us to wait. We must protect our metro now as best as we can. When harbour protection has eventually been established, then the metro will be doubly protected," said Lillah Lucie Emmik Sørensen.

"What is unique about the metro construction, is that the individual building site will be there for many years. We have therefore also taken climate change into account in the construction period, because we have to protect the people that work on these sites as well as the often quite expensive machinery. During the construction period, we have to safeguard the sites against cloudbursts, storms and storm surges. With regard to storm surges, this applies primarily to the work sites in areas close to the harbour. We will assess how high these sites should be and whether we need to establish barriers around the site. The construction sites are usually protected against a 500-year event.

Metroselskabet was founded by the Government, the City of Copenhagen and the City of Frederiksberg in 2007. The parties brought a total of DKK 9.6 billion into the company in the form of the existing Metro and cash contributions from the owners. The Government contributed DKK 4 billion, the City of Copenhagen contributed DKK 4.8 billion and the City of Frederiksberg contributed DKK 0.8 billion.  Funding of the climate change adaptation solutions is included both in the construction and in the operating budgets.