Cases

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.

Seven cast-iron manhole covers on the ground are the only sign of extensive and very complex flood protection for the Citadel in Østerbro, Copenhagen. The Citadel is around 350 years old and is one of the best-preserved fortification works in Northern Europe. The fortification is a listed ancient monument. It also functions as military barracks and as a workplace for hundreds of staff in the Danish Defence. Furthermore, the Citadel is much visited by tourists, and Copenhageners use the ramparts around the Citadel as a green escape from the busy capital. In recent years, the Citadel has been exposed to several torrential flood events following cloudbursts. Following major underground work, the Danish Defence Estates and Infrastructure Organisation has now secured the Citadel against a 1,000-year rainfall event.

In the Municipality of Assens on Funen, three new retention ponds are keeping the town of Tommerup Stationsby dry-shod, even after persistent and heavy rainfalls. The three lakes - together known as Tallerupsøerne - are the largest climate adaptation project to date on Western Funen. The lakes are interconnected via meandering channels, and during heavy rainfall the three lakes become one large lake able to retain as much as 22,000 cubic metres of water. When the lakes fill up with water, the water is led on via a controlled pipe system into the Brende Å watercourse. The lakes were established on a 7-hectare land area acquired for the project by the local public utility company, Assens Forsyning A/S. The land was already gently undulating. The project entailed digging the hollows deeper and adding the soil dug up to the hilly parts, thus accentuating the undulating terrain. The local inhabitants of the area have been actively involved in creating the new landscape and recreational area surrounding the lakes. The lakes were designed to withstand a five-year rainfall event but have proven capable of withstanding more.

The local district heating company, Høje Taastrup Fjernvarme, pumps up groundwater, sends it, and the energy it contains, onwards through a heat pump and into the district heating pipelines; thus killing two birds with one stone. An excellent business case is what originally prompted Høje Taastrup Fjernvarme to start using groundwater for heat production. However, the process also lowers the high groundwater levels in the area. Previously, residents in the area experienced frequent flooding of their basements because the water table has risen by several meters over the past years. The cooled water is pumped into the Mølleåen river, which will significantly improve the living conditions for flora and fauna. Dispensation from the Danish Energy Agency was required, because the area is otherwise designated for heat supply from CHP.

New synergies have emerged in climate change adaptation efforts in Aarhus. The surroundings of the Danish centre of rehabilitation, research and development, MarselisborgCentret, integrate health, urban nature, rehabilitation and climate change adaptation in a single project. The project is called SPARK - in Danish, an acronym for health, park, activities, rehabilitation and climate change adaptation. The project is part of local water company Aarhus Vand's strategy to couple health and climate change adaptation efforts. SPARK is the first concrete result of the strategy. In this project, MarselisborgCentret, the Central Denmark Region and the City of Aarhus have collaborated to establish a 7.3-hectare area in the city, able to contain and retain almost all the rainwater that falls on the centre site. As a side-effect of the project, the many users of the centre and the thousands of local residents in the area now have fantastic new recreational opportunities. The SPARK park has been financed with funds from various foundations. The park is designed to withstand a 35-40-year rainfall event.

The Blue Edge (Den Blå Kant) will be the residents of Svendborg's new common harbour space between the city and the sea. Three sluiceways and a belt of fixed and mobile dikes along the outer perimeter of Svendborg Harbour will protect the area against storm surges of up to three meters above mean sea level. Svendborg city lies elevated compared to the harbour. The project will therefore also establish several emergency flood channels leading stormwater runoff from the city directly into the harbour basin. The harbour basin can be used as a reservoir to protect the harbour area onshore against flooding during cloudbursts when the city sends cascades of water downhill. Svendborg Municipality estimates the total project cost to be several hundred million kroner. The municipality therefore also expects the full project will take more than ten years to complete. Once complete, however, the harbour area of Svendborg will be able to withstand a 100-year storm surge event and a 100-year rainfall event.

Vejle Municipality, the local water utility company and a local housing association have joined forces in a climate change adaptation project to prepare some of the eastern district of Vejle for more extreme rainfall in the future. The climate project consists of five sub-projects to ensure rainwater is effectively channelled into Vejle Fjord rather than into basements and onto roads. The new area will also offer a recreational space for play, ball games and outdoor relaxation. The first sub-project is the Climate Park: a green 750-square-metre wedge with an open, several-hundred-meter-long water channel. The Climate Park sub-project is part of a larger climate project in the eastern district of Vejle, the aim of which is to channel rainwater runoff along a 3.5-kilometre-long conduit from the higher-lying northern part of the district downhill into the fjord. The entire water passage can cope with as much water as will fall during an 80-year to 100-year rainfall event, projected to the year 2100.

The more than 90-year-old green oasis, Enghaveparken, in the Vesterbro district of Copenhagen has been transformed following an extensive renovation project. The park is now one of the largest climate change adaptation projects in the City of Copenhagen. The project to renovate Enghaveparken was a collaboration between the municipality, Områdefornyelsen Vesterbro (municipal district renewal initiative) and HOFOR – Greater Copenhagen Utility. Several foundations also contributed to the project, and residents in the area were invited to be a part of the project as well. Following the project, Enghaveparken can now retain 22,600 cubic meters of stormwater runoff, and normal rainfall channelled to the park can be reused. In addition, major upgrades have been made to Enghaveparken, so that the park now has improved facilities for play, recreation and nature experiences. All renovation and renewal work was carried out with respect for the park's original architectural characteristics.

In the small town of Gedved north of Horsens, Jutland, the Danish Nature Agency has established an almost 42-hectare stormwater wetland area, including a restored Gedved Lake. The purpose of the project is to reduce the amount of nitrogen that ends up in Horsens Fjord. At the same time, the project has improved the natural habitat, i.e. by introducing a wildlife corridor. Horsens Municipality has also designed the new stormwater wetlands to serve as a buffer during heavy precipitation events. Downstream of the new wetlands, properties near Gedved Mill used to be troubled by flooding. However, after establishment of the new lake, even the record amounts of rain during the autumn of 2019 did not cause problems. How substantial a precipitation event the lake can cope with has not been calculated.

In downtown Kolding, the local utility company and the municipality worked together with the city’s residents to establish a multipurpose urban natural landscape. In the future, a retention basin will manage the area’s stormwater runoff, taking some of the load off the sewer system and preventing roads and basements from the worst impacts from flooding.