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Demolished houses transformed into scenic lakes

Demolished houses transformed into scenic lakes

A new recreational area is the result of innovative cooperation between home owners and Odense Water Ltd. who together solved the problems of flooded basements after extreme downpours.

Residents along the street of Ejersmindevej in the Sanderum suburb of Odense on Funen, who have previously lived with the threat of flooding, can at last lay their fears to rest. This is thanks to two new lakes (flood retention basins) in the suburb created by Odense Water Ltd., which benefit residents by giving them a new recreational area and at the same time protect the area against future flooding.

Ejersmindevej is a residential street that had been forced into submission in the face of the extreme downpours that have hit Denmark during the past five to ten years. Since 2005, the area has been seriously affected three times by rainstorms that neither sewers, storm sewers nor flood retention basins could prevent from flooding basements. 

Waterworks bought flooded houses
Following unusual developments in events since the summer of 2006, a solution was found. Odense Water Ltd. bought seven of the particularly flood-prone houses in an area where two new lakes (basins) with greenery could be established. In March 2009 work started on demolishing the houses and excavating the basins.

The three new basins can hold about 10,000m3, which means that they can cope with powerful downpours, statistically likely to occur only once every 50 years. So, the suburb of Sanderum has acquired a new recreational area to enjoy and the residents that remain no longer need to worry about flooded basements. The project has cost about DKK 30 mill. including the purchase of the seven houses.

"Altogether the area benefits from this solution. We get a new recreational area, and Odense Water Ltd. has really listened to the residents' wishes in connection with the creation of the new area. My neighbour is a bird enthusiast, and I know that his and others' wishes have been listened to and acted on after the public hearings," says Heidi Nielsen. She also thinks that it is good that nobody has been forced into things.

The photos above show Ejersmindevej 18-28 during (left) and after demolition (right).

Serious flooding required new solutions
According to Nena Kroghsbo, MSc in engineering and project manager at Odense Water Ltd., the first serious flooding in the area occurred in 2005 and 2006. And given that predicted climate change, with more extreme downpours was only likely to exacerbate flooding problems, the company decided that a new solution was required.

Proposals were considered for various types of basins of 5,000-10,000m3, as well as expansion of the existing sewers or a new sewer leading to Odense River. However none of these proposals were viable because of legislation, nature protection issues or plans for the area.

At a meeting in November 2007 between Odense Water Ltd. and the Municipality of Odense, a number of issues were identified as prerequisites for the new solutions.

  • There is a shortage of green areas in Sanderum  
  • Open spaces in Sanderum are too small in relation to requirements and recommendations 
  • Lakes must not cover all green areas  
  • One large lake is better than several small ones 
  • We must avoid conflicts with private property owners in relation to the location of the basins  
  • We must find a common solution that is supported by all involved parties


Home owners' proposal held water
Initially a number of ideas came up after the prerequisites had been specified, but in the end it was the local residents who came up with the best idea.  The idea was that Odense Water Ltd. should buy some of the flooded properties and locate the extension of the existing Ejersmindevej flood retention basin there.

Odense Water Ltd. was happy to develop a model that allowed home owners to enter a voluntary agreement in which they could sell their house to the company and move away from the "danger area". Odense Water Ltd. established that it would be legally possible to expand the Ejersmindevej basin such that it would have an adequate storage volume, if at the same time another area could be established as a flood retention basin.

The best and cheapest solution
In January 2008 Odense Water Ltd. and the home owners agreed on a procedure to sell the houses:
Three independent estate agents would assess the cost of rehousing each home owner to the same standard that each home owner had come from. These assessments would then be used to establish the final sales price. The sales price would be calculated as a weighted average price, such that the lowest price would be weighted with 25%, the highest price with 25% and the middle price with 50%. The result was, that of the nine home owners who received an offer for their house, seven accepted. 

Nena Kroghsbo emphasises that a crucial aspect for Odense Water Ltd. has been that the process was voluntary and nobody felt themselves forced into a sale. "And it's also worth noting that the home owners' solution is by far the cheapest when compared to our own solutions," she says.