To think of changing the results by reproducing the same gestures is staggering naivety. Throughout history, humans have innovated in the face of significant life-threatening challenges. Producing new means of survival is also the basis of our ability to adapt. All species adapt until a threat becomes too great too quickly for them to survive. This is what we are currently experiencing on a large scale with what is called the sixth mass extinction. We call this era the Anthropocene.
More than other natural factors, humans, through their actions, influence the transformations of their environment and the evolution of our planet. On this scale, we can say that our economic system and our way of life have become phenomenal vectors of inertia and destruction.
For its part, the water is anything but inert, especially in the spring, when the melting is in full swing. Beyond the out-of-control spring floods, the climate crisis is causing, among other causes, an increase in the frequency of heavy rains. We are now talking about atmospheric river, a phenomenon that comes with more overflows from sewer lines in rivers, lakes and the river. Wherever cities have high levels of impermeability, their underground infrastructures suffer as soon as heavy rains pour on their ground.
The phenomenon is easy to understand: the more floors you have covered with asphalt and concrete, the more water will go down the drain. Normally, this runoff should be absorbed by the surrounding soil, but the mode of development of our cities has made the natural permeability of surfaces disappear. Most city centers with high density have impermeability rates of more than 80%, or even up to 90%. In such cases, it is estimated that barely 1 to 2 millimeters of the first drops of water that fall will go into the ground. At 50%, on the other hand, it’s around 10 to 15 millimeters.
We understand better why our sewer pipes are completely under pressure when heavy rain comes. Some will respond to this problem by saying that we only have to enlarge the water pipes and everything will be tiguidou! I would say that’s the kind of thinking that follows the same logic as adding lanes to highways when they become too congested. Proposing similar solutions is the equivalent of repeating the same actions hoping to obtain different results. We turn arround. Instead, we must turn to innovation.
Last week, a Radio-Canada report presented a blue-green alley project in Pointe-Saint-Charles. The concept is simple: all you have to do is divert rainwater by redeveloping soils and buildings to reduce the pressure on the sewer network. A whole arsenal of means can be deployed to achieve this: the development of retention basins around the alley, the addition of membranes and plants to help capture water, the installation of drains dumping for filtration… up to the construction of green roofs that divert water from roof drains.
This is where the concept of the sponginess of our urban spaces lies. A report from the Union of Quebec Municipalities (UMQ) unveiled last week tells us that the challenge for local governments in Quebec will be adaptation to climate change. It is estimated that this could incur costs of nearly $20 billion over the next decade. With such sums, all good ideas to achieve lasting solutions are welcome. Especially since the problem will not stop in ten years.
Each identical street repair is a missed opportunity to reduce pressure on the city’s underground network. Admittedly, it may be relevant to take advantage of this to magnify certain behaviors. However, doing nothing on the surface to divert rainwater is absolutely counterproductive.
Especially since these developments can have other direct benefits for the urban environment. First of all, they promote and contribute to preserving biodiversity. More moisture in the soil also means cooler air. This is an excellent way to help reduce urban heat islands. Not to mention that, contrary to what some say, nature makes the city more beautiful. Yes, yes, there are still some to say that the place of nature is in the countryside.
The fundamental problem of our cities, it must be repeated, is their impermeability; not the size of their sewers. To enable them to adapt to climate change, they must be transformed into sponges capable of absorbing as much water as possible and thus reducing the impact on our underground infrastructures.
For example, we must stop thinking that a commercial street or a public place must be entirely covered with beautiful granite stones, with just a few pits here and there for trees. It is our bad planning habits that have led us to this catastrophic scenario. The time has come to change our approaches. Innovation, after all, is about doing things differently, not repeating the same mistakes.