Could we build incredible cities
that act like giant sponges and save thousands of lives,
all by just copying what nature does already?
Let’s explore that.
So, here’s the problem:
Let’s say that it rains a lot,
and you live in a city that’s covered in concrete streets and buildings
and other hard surfaces
where all that rainwater has nowhere to go,
so instead of seeping into the ground
like it would in a forest or a grassland,
it just kind of flows,
which means it can easily overwhelm city drain systems
and cause flooding,
from just small, annoying floods
that make getting to work a little bit harder,
all the way to huge floods that cost millions
or even billions of dollars in damages.
And all of those manmade structures that we use
like concrete gutters and drainage tunnels,
they’re all known as gray infrastructure, by the way.
Just remember that for later.
Now, since 1995, flooding has killed over 157,000 people,
and it’s the leading natural disaster around the world.
And seeing as climate change is turning our weather system
a little bit loopy,
we’re gonna be facing a lot more extreme weather events in the future,
including more of that flooding,
which is actually something
we got a sneak peek of just last year in 2021;
with floods across Europe that destroyed entire villages,
and parts of China experiencing
once in a millennia rainfall and flooding.
I combine that with the fact that by 2050
the world’s population living in cities
is expected to almost double,
we’ve gotta figure something out.
So, what if we looked to nature for the solution?
Instead of fighting against big old Mother Nature
with unnatural solutions,
what if we could just work with it?
And what if I told you there’s an idea that does just that?
And it’s called ‘sponge cities.’
Here’s how they work:
Sponge cities use a lot of green architecture principles
to create spaces that are designed to absorb water
just like a sponge.
To do this, they use things like porous pavements and roads,
tree planting, roofs that are covered in plants and soil
that retain water,
huge green spaces filled with interconnected waterways,
channels, and ponds,
and also areas that act like things
like parks when it’s dry, but wetlands
when rivers just need a little bit of extra space to overflow—
which is exactly how wetlands are supposed to work
before they’re paved over and turned into cities
in the first place.
The system passively absorbs flood water
with its sponge-like structure.
And when this is combined with better gray infrastructure
you can create cities that can handle almost four times
the amount of rainwater than normal cities are able to,
and they can reduce flooding by around 50%.
But it also comes with a heap of other benefits.
The water that’s absorbed is also passively cleaned
and can be slowly collected and stored away
for use by the cities,
which is really important
seeing as urban areas actually struggle
with having access to clean water supplies.
Biodiversity is also increased
with whole ecosystems flourishing within cities
alongside the human wildlife that already lives there.
And it can also have a massive impact
on what’s called the ‘Heat Island Effect,’
which is where cities generally get really hot,
because that same infrastructure that can’t absorb water
turns out to be really good at absorbing heat.
So the extra plants and green surfaces in a sponge city
can keep cities cooler.
And then on top of all of that,
there’s also the huge impact that more green spaces have
on improving mental health and just overall well-being.
So, if the idea is so good, where are all the sponge cities?
Well, the idea of them was really pushed
by a Chinese architect called Professor Kongjian Yu,
who is inspired from old Chinese irrigation systems
called ‘mulberry fish ponds’—
and he’s been bringing them to life for decades.
China already has 30 sponge city projects
that it’s working on right now,
that aims to be completed by 2030,
that’ll soak up and reuse 70% of urban rainfall.
And on the other side of the world,
there are places like Rummelsberg in East Berlin,
which is an actual large scale example of a sponge city
that has things like green roofs.
And instead of storm sewer systems,
they have these green channels called ‘swales’
that let rainwater actually get into the ground
And now places like the U.S. and Indonesia
are looking to adopt these ideas as well.
And it’s not surprising all of these places wanna give it a try.
I mean, it leads to better lives
while it’s also protecting against a really serious threat.
So it seems to me like a win-win all around.
So obviously, I’ve gotta ask, “What’s the catch?”
Well, to create a sponge city
either from scratch or retrofitting an existing city,
you’ve gotta commit like 100%,
because it relies on all of these different systems
of green buildings and green spaces
and all of that other stuff actually working together
to actually stop flooding from wrecking a city.
And it’s also expensive.
Like, look at China’s project,
their massive aim of 30 sponge cities
is gonna cost at least one trillion U.S. dollars nationwide,
which is billions of dollars
for the individual cities themselves.
And this is over a period of like 10 or more years.
So to make all of the systems work together properly,
you first need proper commitment to investing
that massive amount of money.
And then you need a bunch of different government units
to collaborate properly,
which you can probably guess
isn’t the easiest thing to achieve.
And Zhengzhou in China is a beautiful example of that.
that it’s one of china’s front runners in their sponge city projects
but in 2021, when that freak, once-in-a-millennia rain hit,
it couldn’t cope.
But that doesn’t mean that sponge cities don’t work,
because Zhengzhou is meant to be spending
billions of dollars on becoming a sponge city.
But so far, it’s only spent millions,
which means it hasn’t really done enough yet
to see the impact of the sponge city idea.
But something it did prove is
that floods are really expensive.
Like if you were to hand an invoice
over to the government units for the cost of the flood,
it would show that the overall damage from the floods
was worth as much as the estimated total cost
of turning it into a sponge city.
And that’s just for one flood.
So, it would probably have just been cheaper
if they had just gone full throttle
with the project from day one.
And that is a key lesson.
Even if these projects are expensive,
they’re gonna prevent bad stuff from happening
that can be even more expensive, and even deadly.
Obviously, the best solution for climate change
and things like flooding that’ll come with it
is to just stop it and prevent it in the first place.
But honestly, we might not do enough quick enough
for that to actually happen.
So we do need to think about ways that we can adapt
to the things that are probably coming our way.
So sponge cities show us that
we’ve still got a lot to learn about how we create our urban spaces,
and it shows that nature might have the solutions
that we are looking for,
even for problems we didn’t know we could solve.
But for a lot of solutions,
we’ve gotta commit fully to actually see the results,
which is a great lesson.
But if I’m being honest,
these sponge cities just look cool as hell
to live in anyway.
So I say, let’s just build as many of them as possible.
Could we build incredible cities