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Six mayors have joined forces to flood-proof an area around a river

Six mayors have joined forces to flood-proof an area around a river

Six municipalities surrounding Copenhagen risk flooding in the event of cloudbursts and storm surges. A major cross-municipal project will address this risk.

As a part of railway construction work, residents in Vestegnen, a suburban area to Copenhagen, will be protected against future flooding after extreme rainfall. The construction work is taking place along Store Vejleå river, which runs through the six municipalities that make up Vestegnen. Three of the municipalities will be donating land to one of Denmark's largest stormwater systems.

In 2007 and 2011, the municipalities of Ishøj and Vallensbæk experienced heavy rainfall that led to the flooding of tunnels, roads and basements. A solution to the problem is now under way, which will safeguard residents in the area close to Store Vejleå against flooding in the future.


"The rainfall in July 2007 left a lasting impression on many Ishøj residents who had their homes flooded and lost valuable assets. Next time, one of the neighbouring municipalities could be hit. We have therefore joined forces across the municipalities in the area in order to avoid problems in the future," Mayor of Ishøj Municipality Ole Bjørstop said.

Vestegnen has a beautiful natural river, marsh and lake system which, under normal conditions, collects and transports stormwater. However, due to climate change, cloudbursts have become so intense that the stormwater floods the river banks.


"With this new solution we have struck a good balance between reducing the risk of homes being flooded while at the same time thinking about nature. For example, we will preserve the grazing area by Vallensbæk Marsh," said Mayor of Vallensbæk Municipality Henrik Rasmussen.

The wastewater treatment companies in the six municipalities will be in charge of planning and executing the project. New treatment basins and pumping stations will be added to what will become one of the largest stormwater systems in Denmark. Today, the system includes lakes and marshes in the vicinity of Store Vejleå, to which the six municipalities lead their stormwater.

"To ensure a good aquatic environment in future, part of the project will be to establish flood retention basins in Høje-Taastrup, which will treat the increased amounts of stormwater before they are discharged to Vallensbæk Lake. In this way we will ensure that our common recreational areas stay clean," said Mayor of Høje-Taastrup Municipality Michael Ziegler.

In future, a new electronic and automated control system will signal when the water level in the lake becomes too high, and a sluice will then open and lead the water on to the adjacent Vallensbæk Marsh. In order to avoid flooding of the residential neighbourhood, controlled flooding will be performed of the marsh. This means the system will use the area's natural ability to retain the stormwater.

Furthermore, an emergency pump will be installed at Ishøj Harbour which can pump the river water over the sluice during prolonged high water levels.


"In Albertslund, the risk of flooding is not as great as in Ishøj and Vallensbæk, however our stormwater ultimately ends up in our neighbours' backyards, and we are therefore responsible for helping find durable solutions to the problem," said Mayor of the Municipality of Albertslund Steen Christiansen.


The mayors of Brøndby and Glostrup municipalities share his view:


"We want to take responsibility to ensure that the increased amounts of rainwater that fall on Brøndby are led on to Store Vejleå in an appropriate manner, " said Mayor of Brøndby Municipality Ib Terp.


"Water knows no borders and we are all at risk of being affected if our common water system overflows. Solving the problem together is therefore the only right thing to do," said Mayor of Glostrup Municipality John Engelhardt.

It is anticipated the new system will be ready for use in 2014. Before the project can be commenced, the project plans need to be approved by all six municipal councils, the wastewater treatment companies and the authorities.

Total expenditure for the stormwater system, new pumping stations and control systems is expected to amount to around DKK 40 million. This amount will primarily be financed through the compensation which Rail Net Denmark will pay to the utility companies in connection with the establishment of the new high-speed link between Copenhagen and Ringsted.