The City of Vejle protects against climate change and establishes a new urban space

Rapid intervention with backs against the wall

The sluice works, the pump station and the new urban space were inaugurated in autumn 2016. The facility has already been in operation seven times during its first year.

The project started in 2013 when Vejle Municipality and the municipal wastewater utility came together to find a common solution to the city's many challenges with flooding.

Intensive collaboration between the partners meant that the DKK 30-million project could be decided, approved and completed in only three and a half years.

There has been a number of technical and geological challenges, and work to safeguard Vejle and its inhabitants against water from above and from the sea is far from over.

The municipality and the utility company are continuing their collaboration on other projects. These projects include another sluice, as well as dykes and local climate-change adaptation projects in various parts of the city.  

Repeated flooding

Downtown Vejle lies at the bottom of a river valley and receives water from the three watercourses Grejs Å, Vejle Å and Højen Å. Together, these watercourses have a total catchment area of 330 square kilometres.

At Downtown Vejle, Grejs Å forks into Omløbsåen and Mølleåen. Further downtown, these two watercourses come together in Sønderåen (part of Vejle Å). The slopes dropping down towards Downtown Vejle are steep with an inclination of up to 25% in some places.

Downtown Vejle moreover lies at the bottom of Vejle Fjord. All of these factors mean that the water system in Downtown Vejle is extremely complex.  

Throughout a number of years, Vejle has been plagued by flooding almost every year, for example following cloudbursts, extreme precipitation events and storm surges.

The new sluice was able to ward off a storm surge as recently as October 2017.

The water stood 1.51 meters above mean sea level. The City Council's risk management plan predicts that a 100-year event in 2050 would mean a water level in Vejle Fjord of 2 meters above mean sea level.

Coping with water from the skies, the sea and the hinterland

Vejle Municipality and the municipal wastewater utility have created a holistic solution that addresses many different challenges at once.  

The project in Downtown Vejle consists of a sluice, a pumping station, distribution works, a wildlife corridor, raised watercourse banks, improved runoff from the sewer system and a decision to require a higher spot height for future building and construction works.

The sluice is located at the mouth of Omløbsåen and consists of two sluice gates. The sluice can withstand water levels of up to 2.5 metres above mean sea level. This corresponds to a 100-year event in 2100.

The sluice gates can close in just a few minutes. Control of the gates and the pumps is in the process of being automated through an advanced control system called SMART VAND (smart water). This control system uses a rain radar and weather forecasts from the Danish Meteorological Institute, watercourse measurements and computer simulations.

The pumps are placed as part of the same construction as the sluice and can pump up to 7,500 litres of water per second from Omløbsåen into Sønderåen. 

The distribution works are located in Grejs Å where the watercourse branches into Omløbsåen and Mølleåen. When there is too much water in Grejs Å, the distribution works ensures that the water is regulated optimally to avert the flood risk.

The project has also taken account of nature by including a wildlife corridor so that fish such as seatrout and lamprey can migrate from the sea and fjord via Vejle Å and Omløbsåen up to their spawning grounds in the Grejs Å watercourse system.

A wall has been constructed that divides the water in Omløbsåen so that half of the water is regulated via the new distribution works, while the other half is allowed to continue its course along a 90-metre-long riffle through which the fish can pass.

The banks along the northern side of Sønderåen have been raised to 2.5 meters near the sluice and pumps. The city council has decided that any future buildings in

Downtown Vejle must be at a spot height of 2.5 meters as a precautionary measure.

The total climate-protection works are expected to have a lifespan of 50 years and they can cope with 10-year rain events and 100-year storm surges.

The sluice and the pumps as well as the distribution works can only manage a certain amount of water from Grejs Å, depending on the water level in Vejle Fjord.  To further reduce the risk of flooding in Downtown Vejle when Grejs Å carries extreme water amounts with it, the city has to find areas for temporary retention of the water in the catchment area to the Grejs Å watercourse system.

Work has been initiated to ensure this, and includes finding areas that can retain a minimum of 170,000 cubic metres of water. Among other things, there are plans to increase the height of the watercourse banks and embankments along sections of Vejle Å.

New attractive and popular urban area in Downtown Vejle

The municipality has used the occasion to transform a rather drab and boring urban area into an attractive urban space with areas for sitting and playing and steps leading all the way down to the water with open views to the cascading water by the pumps and sluices. A win-win solution for everyone.

SLA architects were tasked with linking the countryside areas adjacent to the city with the new technical installations.

Now canoes and kayaks can land at a pontoon bridge to which there is also access from the street.

From the pontoon bridge you can see the sluice and you can see the entire run of the water from the stream through the gratings to the pumps and further onwards to the pumping chamber and out into Sønderåen.

100% co-financing

The original project was budgeted at DKK 30 million. Of this, DKK 28.5 million were funded through wastewater charges via the so-called co-financing scheme. This corresponds to financing of 100%.

A total of DKK 1.5 million were paid by Vejle Municipality for improvement of the urban space and lighting around the technical installations. In addition to this, the city council funded the project with DKK 7 million for the new urban space integrated into the technical installations.  

The project will end up costing DKK 45-47 million. Of this, DKK 32-35 million will have come from the co-financing scheme.

The part of the budget overrun not covered through the wastewater charges has been funded by Vejle City Council.

A traditional project with sunken basins would, however, have been far more expensive, i.e. DKK 73 million.

Vejle Municipality pays for operation and maintenance of the urban spaces and the watercourses. The municipal wastewater utility is responsible and pays for operation of the technical installations.

Vejle municipality and Vejle City Council have overall responsibility

Due to time pressure, the citizens of Vejle have not been included more than absolutely necessary in the process.

The decision-making process has been transparent, as all cases have been processed on the basis of published agendas. This applies for case processing by the nature and environment committee, as well as case processing by the finance committee and the city council. There has been no criticism of the process from the public.  

The municipality and the utility have been on inspirational trips to Hamburg, Germany, and Aarhus, Denmark; i.e. to cities facing similar challenges as Vejle. Today, Vejle itself welcomes many visitors, who come to the city to seek inspiration.

Ulla Pia Geertsen from Vejle Municipality says several circumstances have been essential for the project's success: Good political backing and good project management in the municipality. In addition to this, good collaboration at technical level brought the project from plan to action.

As in all projects, there have been challenges, but these were dealt with along the way. 

COWI served as an advisor on the technical part of the project. Krüger assisted with the hydrology calculations. Orbicon served as an advisor with regard to the distribution works. SLA architects were responsible for the urban space.

Vejle Municipality says that there was constructive and solution-focussed dialogue and cooperation between the contractor, the architect and the advisors.  

Very little space and many obstacles along the way

Everything went very fast. Therefore, there were a number of factors that were not included from the beginning but which turned out to pose challenges later on. At the same time, technical aspects and requirements from the authorities caused problems. 

This is the first project that Vejle Municipality and the municipal wastewater utility have carried out together.

Due to time pressure, the budget had not been sufficiently consolidated. The budget did not take sufficient account of the required authority approvals and permits. Furthermore, the timetable for many project phases was too optimistic. The project's technical installations were delayed by about six months.

Government requirements pertaining to the water table in the construction site and the water quality in Grejs Å turned out to be more difficult to meet than anticipated.

With regard to the collaboration at management level, Vejle Municipality admits in hindsight that they neglected to carry out a more detailed matching of expectations.

For example, there was a failure in the beginning to realise the need for a common steering group. Such a steering group was not established until much later in the process.

The project also encountered problems with contaminated soil. Tightened requirements from the groundwater authority groundwater lowering meant that the selected sheet pile solution had to be changed.

A cloudburst meant that the watercourse authority tightened the requirements for water flow in Grejs Å. As a result, the construction process had to be changed.

Finally, there have been technical challenges with the sluice gates and gratings, among other things.

All in all, Project Manager Claus Weng Petersen from Vejle Municipality concludes that:

"It's difficult and there'll always be unpredictable, significant impacts; this is a basic condition for projects of this type. Accept it and make it work anyway! And remember to budget with a large time and financial buffer.