In late January 2018, Paris seemed to be drowning. Both the Seine and the Marne rivers overflowed for their banks, forcing some suburban city-dwellers to have to row to reach their houses, while the iconic Zouave statue on the Pont d’Alma was even given a life-vest. That was just before snow engulfed the French capital.
Cities in Europe will suffer from heat and heat waves as well as from extreme rainfall which will be a new challenge for planners and health care services. Cities will need to adapt drastically to avoid catastrophes. While reducing carbon emissions is key to tackle the global issue there are various ways to make cities more resilient.
Informing people about approaching heat waves is one important issue. Doing so, all possible information and communication sources should be activated. Apps, social networks such as WhatsApp or Facebook groups can prove handy provided they are used with consistency as explained by social scientists observing social media response to disasters in California.
These practices bring nature back into the built space and make use of its great properties to balance heat and also heavy rainfall by filtration, absorption, percolation and seeping functionality. Open soils in parks, on lawns, in cemeteries or urban gardens are highly suitable for this but also green roofs, rooftop raingardens or green walls. All buffer heat and emit transpiration coolness.
Revitalized brownfields and their conversion into large public parks and greenspaces can become a hit such as the urban farms set up in the middle of Berlin, Germany, in Edinburgh in the UK, Malmö or Leipzig in Sweden just to list a few. It can also take the shape of bioswales – linear vegetated channels, specifically designed to attenuate and treat storm water runoff.
Trees and forests, in addition, also emit essentials which are good for human’s lung function and respiratory power. Thus, green spaces have great synergies to balance heat, heavy rainfall and transport emissions (particles, nitrogen oxides).
Blueing the city means to increase open water surfaces and create areas which can be flooded (in the Seine wetlands for example) or where water can stand. These are the more technological answer in case wetlands or riparian areas are not available or totally embanked.
A resilient city in terms of its eco-climatological conditions is a city which takes into consideration what I sketched above and which holds areas for greening and blueing and invests in an excellent and flexible information/communication network.
In addition, complementaries between green, blue and built (grey) infrastructure should be taken into consideration and not mutually ignored. For example, dams are sometimes necessary as bioswales can only take up a certain amount of water.
Beyond technical considerations, we also need to take into account the political aspect of a resilient city : first and foremost, it is a space where citizens should all access the necessary information to mitigate catastrophe, free of charge, as a civil and municipal service.
That is why, instead of blocking the water, other cities think to welcoming it. For instance, the city of Hamburg, in the Netherlands has the project to create a new floodplain for river Elbe to restore “some natural balance to a dockland area”, which has been under stress for half a century due to heavy ship traffic.
Of course a large 100-years flood cannot be buffered or balanced by bioswales or lawns along a floodplain; but it can reduce peaks and make flood velocity lower and give people more time to react.
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