Why?

The “Zuiderdokken”, with a total surface area of 9 hectares, is the largest square in the city of Antwerp. The large square presently serves as a parking lot.

The Antwerp municipality drafted a master plan in which two underground parking spaces would be built over the course of 2018 – 2019. Consequently, the square itself will be “freed” from this mono-functionality and can therefore be completely renewed.  The city organised a design competition with a large emphasis on climate adaptation for the renewal of the square, because of its strategic location with regard to floods and heat stress.

The figure below shows the expected floods in the city of Antwerp for a return period of 5 years, taking into account a high climate scenario with a 2100 time horizon. Flood prone areas are indicated in blue, flood free areas in red. The Zuiderdokken square is represented by the black rectangle. The figure shows that the southern part of the city, where the Zuiderdokken square is situated, is particularly flood prone.

As a result of a high building density and the absence of large green areas within the city, night temperatures are higher within cities compared to rural areas. This is the so-called urban ‘heat island’ effect. The figure below shows the average difference in temperature between the city of Antwerp and the surrounding rural area during the summer. The Zuiderdokken square is situated in the red zone where the difference in temperature during summer is 4°C on average and even goes up to 8 to 9 °C during heat waves.

Climate adaptation therefore was an important precondition in the project definition of the design contest. All participants of the contest evidently proposed a park area with a focus on green and water. The contest was won by Tractebel, ADR Architects, Georges Descombes and Les Eclairistes Associés & Erik De Waele.

What?

The selected design team further elaborated this blue-green infrastructure in close collaboration with -and participation of- different stakeholders. Regarding blue infrastructure, the design included a combination of small and big measures that together constitute an integrated solution for water related challenges.

Half of the square, today almost completely impervious, will be reconstructed with permeable (grass fields) and semi-permeable (dolomite) surfacing. Water from the adjacent walkways will be buffered in rain gardens. These rain gardens have a relatively small buffer capacity (180 m³ in total), but are very important for educational purposes and for the ‘water experience’ of the by-passers, as water fluctuation will be visible here first, even at low rainfall intensities. Water play elements further contribute to these awareness and education functionalities. More substantial buffer capacities however, can be found on the ground level in two swales and a lowered meadow as well as in a large subsurface storage. The lowered meadow is the last link in the chain and will only be flooded under very extreme circumstances.

A total volume of 9000 m³ of water could be buffered. This corresponds to a total drainage surface of 25 ha for a return period of 20 years, taking into account a high climate scenario with a 2100 time horizon. The ambition of the city for this square highly corresponds with its strategic position for adaptation. Not only will water from the square be buffered, but also from a large part of the adjacent quarter ‘het Zuid’.

Reuse of water has also been considered. Rain water from each roof surrounding the square is collected into a communal rain water harvesting system with a capacity of 1500 m³. The collected water will be used to clean and replenish city sweeper trucks and to irrigate young trees. It will also be partly upgraded to drinking water which could be provided to buildings in the neighbourhood. This way the park also offers a solution to the increase of drought periods and resulting water shortages in the future.

The communal rainwater harvesting buffer will be an intelligent system. The buffer has to be as full as possible for reuse purposes, and as empty as possible for water storage purposes. These requirements seem contradictory at first, but can be reconciled if we can operate the buffer based on rainfall predictions. When heavy rainfall is expected, the buffer will proactively be (partly) emptied in order to free some space to buffer the expected rainfall. This water will be partly led to the area in front of the monument called “Waterpoort” (water gate). Water in this areas therefore will be an indication of rainfall in the coming hours. The entirety of the square will be constructed in the period of 2019 until 2022.

With whom?

In order to have an integrated solution with a broad support a process was followed based on participation and co-creation. Following stakeholders were involved:

• AG Vespa, public real estate cooperation
• Rio-link (local sewer system manager )
• water-link (drinking water company)
• the city, design of public space
• the city, inspection and maintenance of public space
• the city, sports and play
• MPA, mobility and parking Antwerp
• QPark: concessionaire of the underground parking
• Van Laere: contractor for the underground parking
• fire brigade
• citizens
• architects and designers from Tractebel and ADR and the consultancy firm IMDC
• Triple Living (private real estate cooperation)
• Today for Tomorrow (private real estate cooperation)

How?

• group 1: AG Vespa, Rio-link, the city design of public space, the city, inspection and maintenance of public space, the city, sports and play, architects and designers from Tractebel and ADR; consultancy firm IMDC
  empowering through multi-stakeholder engagement
• group 2: citizens
  consulting through organised events
• group 3: water-link, fire brigade,  the city, inspection and maintenance of public space, architects and designers from Tractebel and ADR; consultancy firm IMDC
  empowering through cost benefit analysis
• group 4: MPA, QPark, Van Laere, Triple Living, Today for Tomorrow
  collaborating through bilateral meetings

Progress (update January 2019)

Detailed design of the square is finished and a building permit has been submitted.

The actual construction is on hold as the the permit for the underground parking has been suspended. The city still holds the intention of carrying out the climate adaptive measures at a later stage.