WEBVTT

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Climate change is 
bringing heavier rains

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and increased flooding 
to many urban areas.

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Hamburg, Germany is no exception.

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That's why hydrologist  
Andreas Kuchenbecker wants

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to help weather- 
and waterproof the city.

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We can only protect 
ourselves if we know

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how big the burden 
will be in the future.

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If we don't carry out measurements,
all we can do is guess.

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The scientist has set up 
30 weather stations that send him

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data from every corner of the city.

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These precipitation gauges show how
much rain has fallen in each area.

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This is basically a tank
that collects the precipitation.

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And then it weighs it,
using a very precise scale.

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We can see in real time how much
rain has fallen in this location.

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This data is used to calculate
what might happen in the future.

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We need to understand what would
happen if we had a downpour

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with an intensity of eight,
or an intensity of ten.

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It's better if we don't wait until
we actually have that kind of

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rainfall event, but instead feed
our models with our data,

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and use the models to
predict what would happen.

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This kind of weather data will help

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the municipal water authority 
plan for the future.

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Andreas Kuchenbecker and
his colleague Andreas Baier

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are using new simulation software
to generate a model for Hamburg.

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They can now generate 
predictions for every address

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and location in the city.

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Using the simulation software,
they're testing various solutions.

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Could a trench in this city
park help divert excess rainwater?

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I wouldn't make it too big,
I don't think it's necessary.

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Let's start with ten centimeters.

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OK, sounds good.

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On the other side  of the street,

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a retaining wall 
could protect the houses.

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They sketch it in, and the 
software calculates where

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the retaining wall and the 
trench would divert the water.

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Let's check if raising it
made a difference.

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Yes, OK. The water only reaches
the curb, and everything else

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flows toward the park,
just the way we want it to.

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Nice.

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In the park, the ground 
will soak up the water —

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one example of how Hamburg is 
being turned into a 'sponge city'.

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Areas where water can seep
into the ground, green rooftops,

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water-permeable surfacing, 
and rainwater tanks

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are all part of the package.

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Rainwater will be put to good
use right on the spot — sustaining

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plants during heat waves, and
allowing for evaporative cooling —

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making Hamburg
more climate-resilient.

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Turning the city into a sponge city
would be beneficial in two ways.

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First, we'd be reducing
the burden of heavy rainfall.

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And we'd be reducing
the burden of long dry spells.

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So we'd have a win-win situation,
while also protecting

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our drainage and drinking 
water supply systems.

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The city's schools are
also getting in on the act.

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This schoolyard is
being revamped in accordance

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with Kuchenbecker's simulations.

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Environmental engineer 
Bo Willem Friedrichsen is in charge.

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It's another layer in
the transformation of Hamburg

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into a sponge city, a city dotted
with areas that can absorb water.

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Almost all the roofs drain
into rentention basins.

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That has several advantages.

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It's good for the
natural water balance,

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and helps replenish 
the groundwater.

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Plus the evaporation from the
basin helps cool down the city.

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Here you go.

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To the top of the embankment.

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The top, right.

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Pull it tight.

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We're at 9.9 meters.

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Andreas Kuchenbecker enters
the new basin into his model.

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It's amazing how much a
basin like this can absorb.

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This is the nicest part.

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We come up with an idea
in theory, do all sorts of

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measurements and simulations.

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And then we watch it become
a reality here in this schoolyard.

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It's one of the great 
parts of our work,

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and it's hugely motivating.

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A number of other 
areas in the schoolyard

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have also been
turned into sponges.

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Like here, behind the school.

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Large areas of asphalt 
were removed here,

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and replaced with
a water-permeable surface.

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They allow the rainwater
to seep into the groundwater.

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You can see the water first starts
to flow, but pretty soon it gets

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absorbed and then flows
down into the groundwater.

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The rain helps keep the soil here
moist — rather than just ending up

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 in the city's sewage system.

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What's important is that we
get started, that we start

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trying things and gaining
expierence, bit by bit.

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Later generations will 
learn from our experiences,

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and maybe improve on it.

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But someone has to
take the first step.

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By working with water
rather than against it, Hamburg is

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implementing nature-based 
solutions for a sustainable future.