rains and drains

From January through to April this year there was a major exhibition at the Danish Architecture Centre under the title The Rain is Coming. It looked at climate change and the impact that will have on the architecture and planning of our cities. The conclusion was that climate change is happening already and that planning has to take that into account now but it can be seen as a way of making positive changes.

It is clear that for Denmark the climate changes will mean more rain and more intense storms and that drains and roads will not be able to cope with the sudden inundation of water. I have actually experienced this … shortly after I moved to Copenhagen there was a massive rain storm; the street drains backed up and the road and pavements were flooded and water streamed down into cellars. Further along the street many of the buildings have semi basements so there is half a flight of steps up to the entrance and main floor but short flights of steps down to a semi basement that in many buildings are used for shops or workshops. Many of these businesses were severely disrupted by the flood … water had to be pumped out, property dried out and in many cases floors relaid and walls re-plastered. At least one of the businesses is still closed a year on.

There are straightforward solutions that are being implemented throughout the city and in new developments. Many streets are being dug up to install more robust drains to replace simple gutters. These have a large buried concrete channel covered by a continuous grill rather than a gutter that drops water down into a drain at intervals. Permeable surfaces are now being installed so water will percolate down between cobbles or down through artificial playing surfaces on sports areas rather than sitting on the surface or flooding across to overloaded drains and well-planted ditches or hollows will be attractive green features for most of the year but will become streams or ponds when there is heavy rain.

Several major drainage and landscape schemes are now under way around the city. With so much land covered with buildings or roads there is less and less chance of water soaking away but if it is allowed to run straight into drains then they fail and can also compromise or damage the sewerage system with obvious consequences. The schemes are designed to hold back rainwater so that it can be released into the drains in a controlled way after a storm.

 


Enghaveparken

At Enghave, at the west end of Vesterbro, the park was laid out in 1929 with contemporary apartment blocks set around three sides and an earlier road and square to the east. Works there will hold water back temporarily - up to 26,000 cubic metres that runs off the surrounding streets - before it is released into the drains to run out into the sea.


Lindevangsparken

Lindevangen park out in the west part of the city is another large square surrounded by apartment buildings but here the solution looks much more natural with a deep drainage ditch along the east side that is carefully planted to look like a natural river. Again it will hold back water and there is a very large hollow across the south side of the park which will act as a temporary reservoir.

At the south-east corner there is a small triangular public area in front of a cafe and shops and here another hollow has been created but as a hard-landscape feature with a spiral open drain and fountains at the centre.



Tåsinge Plads

Tåsinge Plads and the Skt. Kjelds Kvarter are described as the first climate adapted urban space or climate resilient space in the city. Water running off the roads will be kept out of the sewer and will be used for the irrigation of new areas of planting. There will be a new open water course along Bryggervangen; the parking of cars will be rationalised so they will be relegated to the side of the street that is more often in shade and squares and the sunny side of streets will be planted with trees and sections of garden.

This work is also part of a wider plan to create green corridors through the city often associated with green cycle routes to encourage people to walk and bike but also to provide important areas of green in some parts of the city that are very heavily built up.



Sankt Annæ Plads

This is another major scheme to hold back and control rainwater … here in a long underground tank beneath the very long thin square before it is released into the harbour. Paving set down lower at the top end will encourage water to flow down into the square rather than along Bredgade - the main street that runs across the top of the square. 

Trees and grass are being reinstated now and the work of the tank system will not be obvious from pavement level although its effect will.

It is interesting, looking at historic maps, that in the early 18th century there was a large royal garden here running parallel to the harbour but later built over with the houses that are now the Amalienborg Palace. The church on the side of the present square was there when the garden was laid out so that acts as a reference point and you can see that there was then a garden canal along the line of what later became the square. The water tank takes the same course.

Control of rain water is crucial and nowhere more so than here. At the harbour end of the square is the National Theatre and what was, until ten years ago, the port facility for major Baltic ferries. The ferry facilities have been moved to the North Harbour and the former quay is to become a new public square but below the square, close to completion, is a new underground car park so clearly any issues with rainwater flooding had to be resolved as part of that development.



Amager

Much of the west side of Amager was claimed from the sea around 1900 but even the original island was low lying. For the extensive developments of Ørestad, land drains were again a crucial consideration for planning but again they have been made into a positive urban landscape feature with a series of wide shallow canals taking water down to the open common and nature reserve at the south end of Amager. These start at the new university district and many major new buildings are set along the canal. There are footbridges over the water, steps down, terraces and cafes alongside the canals and in one section several islands with seating.



Ladegårds Å

There is an incredibly ambitious proposal for Åboulevard - now a main road running out from the city on the west side of the lakes. From the 16th century this had been the line of an open river, Ladegårds Å, that brought fresh water into the lakes. In 1897 the river was dropped down into a culvert and a new wide road laid over the top. It now has very heavy traffic with several lanes in each direction and it is difficult to imagine that the fine apartment buildings on either side originally looked down onto a tree-lined river.

The proposal is to take road traffic underground into new tunnels. The river will be reinstated on the surface with narrower roads on either side and the river down the centre will take flood water from the surrounding streets down to the lakes rapidly where it can be held back before being released out through drains at the south end. There will be drains below the new road, in the bottom part of the tunnel, but in the event of very heavy flooding then the tunnels will be closed to traffic and the road space used as well for supplementary drains.