New green oasis will keep basements dry in Kolding

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.

• Status: The urban park has stood the test

  The technical installations in the urban park stood ready before the opening in June 2019. As early as in March that year, the spillway installation proved its worth when prolonged and heavy rainfall sent large amounts of water towards downtown Kolding.

  
  The project was outlined in the municipality’s climate change adaptation plan in 2014, together with 10 other projects.

   

  The project is being financed over wastewater bills.

   

  The project took 18 months from the original tendering procedure until inauguration in June 2019 of the facilities and the 2-hectare urban park.

   

  In the event of heavy rainfall, a series of interconnected spillways will redistribute stormwater from the city’s major stormwater pipes to the urban park.

   

  The spillways were barely completed when they first proved their worth during a prolonged period with heavy rains in March 2019.

• Background: No more flooded basements and roads

  Downtown Kolding has been afflicted by repeated flooding during heavy rainfall. The project has prepared the city for more frequent rainfall events in the future. And the 80-year-old rather waterlogged urban park needed an upgrade anyway.

   

  Downtown Kolding is located on low-lying land. Stormwater runoff from the city districts and surrounding urban areas located on higher ground is collected in the city’s central stormwater and sewer pipes.

   

  The sewer and stormwater system is therefore often a bottleneck during cloudburst events and prolonged heavy rainfall. When the system is overloaded, there is a risk that a combination of stormwater and sewage gush forth from the sewers and run to places where it is not wanted.

   

  The municipality and the utility company see the rainwater as a resource that can be used to create new and exciting solutions for citizens, instead of a problem to be got rid off underground.

   

  The urban park had the perfect location for both these purposes.

• The solution: Retention basin and a nicely meandering canal with a double profile

  When one of the city’s main stormwater pipes are overloaded, a spillway will redistribute the stormwater from the pipe to the urban park. Here, the water is retained in a basin and then slowly further distributed.

  
  The urban park in Kolding is ideally placed between two of the city’s three large stormwater pipes.

   

  One of the pipes, the Marielund pipe, is prone to quickly filling up during prolonged and heavy rainfall with runoff from the surrounding high-lying areas. The climate change adaptation project incorporates a spillway with two wells into the pipeline.

   

  When the pipeline is close to overflowing, a sensor in one of the wells instructs the other well higher up to redirect water from a large inlet to a newly established pipe in the urban park instead of letting the water continue in the large, overloaded stormwater pipe.

   

  The inflow collects relatively clean water, which means the cleanest rainwater is being passed on to the recreational facilities.

   

  Inside the park, the water will be retained in an open pond that can hold up to 4,000m3 water. The pond was created using a dam.

   

  From the pond, the water is directed onwards to the other side of the park to another of the city’s large stormwater pipes, the Eng pipe.

   

  When it does not rain, a narrow stream winds it way across the bottom of the pond.

   

  The urban park is surrounded by dwellings that are home to many elderly people in particular, but there is also a special needs school.

   

  The municipality killed two birds with one stone by converting the urban park to a place with urban nature and school children helped plant some of the trees. The park also has a climate pavilion which can be used for resting and shelter, as well as for teaching. There is free access to the pavilion.

   

  Furthermore, a 700m2 ‘flower meadow’ was established in the park, as well as 11 raised gardens with edible plants and bushes. The park’s users can freely pick flowers from the majority of the garden beds.

   

  The urban park has been designed to withstand a 20-year event.

   

  In an upcoming project, the municipality of Kolding and the local utility company, BlueKolding, will establish a number of depressions along some of the roads running on higher ground above the urban park. The purpose of these depressions is to retain some of the water.

   

  There is also a plan to make use of the city’s lake, Slotsøen. The lake's current 10,000m3 water volume could be increased significantly.

   

  Once completed, and in combination with the urban park, the two projects will be able to protect downtown Kolding against a 100-year event.

• Benefits and added value: Accessibble for disabled people

  Downtown Kolding will be future-proofed against cloudbursts but the city now also has a slice of nature in the middle of the town that has also been made accessible for individuals with special needs. 

   

  The urban park can retain 4,000m³ of rainwater.

   

  The project is an alternative to having the utility company expand some of the existing sewer pipes.

   

  At the same time, the urban park has been transformed into an attractive natural landscape which is being widely frequented by the city’s residents, according to project manager Louise Langschwager Jensen.

   

  The newly planted trees in the park absorb water and CO2.

   

  The renovation of the park included applying a special type of gravel to paths that allows people in wheelchairs to use the park.

   

   

• Financing: The municipality and the utility company split the bill

  The climate change adaptation project in Kolding is being financed 100% over wastewater bills as a co-financed project.The renewal of the urban park was paid by Kolding Municipality.

   

  The climate change adaptation facilities have an expected lifetime of 50 years. The municipality took out a loan of DKK 10 million to pay for the technical installations. The loan is being repaid over the utility company’s wastewater bills.

   

  The municipality financed the DKK 900,000 cost of renewing the urban park.

   

  The climate pavilion was inaugurated in 2017 and was financed by the Danish Outdoor Council and the Danish Foundation for Culture and Sports Facilities, which each invested DKK 479,000 in the project. Kolding Municipality paid DKK 411,000 for the pavilion.

• The process and stakeholders: Collaboration has been super

  The project’s steering committee counted the utility company along with several representatives from the municipality’s department for urban and other development. Local citizens were invited to submit specific proposals and wishes. Design School Kolding also chipped in.

   

  According to the project manager from the municipality, Louise Langschwager Jensen, collaboration “has been super”. The project was approved as part of the municipality’s climate change adaptation plan in 2014. That same year, it was approved by the Water Division at central government level.

   

  The project was put up for tender at the beginning of 2018, and the new urban park was inaugurated in June 2019.

   

  The utility company and four divisions from the municipality formed the project’s steering committee. Broad participation was necessary because the project had to deal with several challenges at once.

   

  There were also citizens’ workshops. Citizens, school pupils and students from Design School Kolding came with proposals for the park’s layout and design.

• Barriers: Remember to set aside funds for maintaining and running things

  Although the project went well on all overall parameters, there are still lessons to be learned. Knowledge was lost, and the project did not include money to maintain and run the park.

   

  It is only natural that project organisation changes along the way in a long-term project.

   

  However, Kolding and the consulting company did not ensure that knowledge was passed on, said Project Manager Louise Langschwager Jensen.

   

  A lot of knowledge was therefore lost along the way. This includes important data about the bearing capacity of the soil. This meant spillways had to be re-dimensioned at the last minute.

   

   

  And you also need to remember to put aside money for maintaining and running urban landscapes,” said Louise Langschwager Jensen. This was not done with regard to the urban park. “And, naturally, the new urban park is more expensive to run than the old lawn that used to be there.”