Berlin offers a model for how cities can cope with increasingly regular extreme floods

Flooding in Texas after Hurricane Harvey grew to be one of the most damaging Atlantic hurricanes in recent years. Image: US Army Photo.

We’ve become accustomed to quasi-apocalyptic images of cities swapping streets for rivers.

Typhoon Hato led to deluges in Hong Kong and Macau, causing £757m and £1.1bn worth of damage, respectively. Hurricanes Irma, Maria, and Jose battered the Carribbean and the south-easternmost states of the United States, while Hurricane Harvey was devastating to coastal areas of Texas.

Houston, Havana, Roseau, Miami, San Juan, St John’s – the list of cities overcome by water and wind this year is a long one.

Even aside from such dramatic events, abnormal rainfalls have caused extraordinary floods in several cities across the world.

Mumbai and Dhaka were just two cities caught up in the vast flooding across India, Nepal, and Bangladesh, which killed at least 1,200 people and put one-third of Bangladesh underwater.

Cities across central and southern China – from Chongqing to Changsha, down into Duyun and Jiangxi province – saw serious flooding, with more than 18,000 homes destroyed.

Flooding in Mumbai in August 2017. Image: News Measurements Network Live.

In Quebec in Canada, nearly 2,500 homes were flooded across Montreal and Laval, while Paris, Berlin, and parts of Switzerland have all spent time partially underwater recently. Images from the French capital, where water gushed and danced down the steps into metro stations, were particularly striking.

One neighbourhood in Berlin is trying to ensure that cities can become better-adapted to the increasing likelihood of extraordinary wet weather events.

The theory rests on the logical foundation that cities are inherently unnatural. By smothering the earth in concrete and tarmac and loading it up with vast structures of brick, steel, and glass, cities interfere with the way nature regulates itself.

The concentration of buildings, people, and activity increases temperatures – while tarmac and concrete surfaces naturally absorb, retain, and emit heat, only pushing the mercury higher.

On the aquatic side of the equation, unnatural, man-built road and pavement surfaces stop any falling water absorbing into the ground and then naturally providing moisture for soil and vegetation during dryer periods, while also evaporating to provide a kind of natural air conditioning.

The area of Rummelsburg in the city’s east, was built 20 years ago and serves as an exemplary model of the ‘Sponge City’ concept – ‘Stadtschwamm’ in German.

Rummelsberg, from ground level. Image: Lotse.

Buildings are wrapped in green walls, roofs, and garden terraces, with thick tranches of soil up to 80cm deep, while roadside trenches between pavements and streets create a miniature urban wetland, which can retain water and both feed it into the water table and evaporate it to keep the city cool.

During heavy rainfall, the thick layers of greenery handle the water better than the conventional concrete-and-drainage system. There’s less likelihood of drains overflowing because they’re blocked or merely overwhelmed, and pavements are less likely to be transformed into temporary white water rafting courses.

The system is also better for water quality in lakes and rivers. During extreme weather events, the grit and grime of urban living can be swept straight into these bodies of water, where unnatural substances can harm animals and plants, and natural materials like pollen and leaves can overwhelm marine life by giving them too many nutrients in one go.

While it’s a great idea, of course, it can be hard to put into practice. While many cities – London included – are on a splurge of building new developments that often conform to higher eco-friendly standards (and could be encouraged, or mandated, to conform to ‘Sponge City’ design benchmarks), the vast bulk of prohibitive surfaces have already been built.


The cities of the UK, for example, already have their streets, pavements, tiled and concrete roofs – so retrofitting is the order of the day. This can be more expensive, more difficult, and can be tricky to incentivise. And while there could be profiteering enticements – a building with an accessible green roof is likely to be more interesting and appealing to buyers and renters, and public or commercial buildings could grow produce in these spaces – it’s unclear whether that will be a significant enough boon.

Nonetheless, as extreme weather events become less out of the ordinary, adapting our greatest centres of population to better accommodate the demands of nature seems like common sense – even if it does mean boggy pavements.

Jack May is a regular contributor to CityMetric and tweets as @JackO_May.

Want more of this stuff? Follow CityMetric on Twitter or Facebook.

 
 
 
 

Where did London’s parakeets come from?

Parakeets in the skies above Wormwood Scrubs, west London. Image: Getty.

Visitors to London’s many green spaces would have to be stubbornly looking at their feet to not see one of the UK’s most exotic birds.  Dubbed “posh pigeons” by unimaginative Londoners, these brilliant green parakeets stand out among the fauna of Northern Europe’s mostly grey cities.

‘Parakeets’ is actually an umbrella term referring to the multiple species, which can now be found in London, Amsterdam, Brussels, Paris and various German cities. By far the most common is the Indian ring-necked parakeet, easily recognisable by the stylish red ring around their neck, a matching red beak and, of course, the loud squawking.

In the last 50 years these migrants from South Asia have arrived and thrived, settling into their own ecological niche. In the UK, London is a particular stronghold, but although they may have originally settled in the leafy streets of Twickenham, the birds can now be found in cities as far north as Glasgow.

The story of how they ended up in London is a matter of some discussion and plenty of myth. One often reported theory is that the capitals’ current population are the descendants of birds that escaped from Shepperton Studios during filming of The African Queen, starring Humphrey Bogart and Katharine Hepburn. Others would tell you that they escaped from Syon Park in the early 1970s, when a piece of debris from a passing plane damaged the aviary and allowed them to escape. This chimes with their original concentration in South West London.
My favourite story by far is that they were released by Jimi Hendrix on Carnaby Street in the late 60s. Bored of London’s grey skyline, he set the little fellas free to liven up the place.

However they got here, from 1970 onwards their numbers boomed. In 1992, 700 birds were recorded in London Bird Report. By 1998, 2,845 were seen in the London Area, and by 2006 the ring-neck parakeet was 15th most sighted bird in London.


Darwin would be proud at how well they adapted to the new environment. Toughened up by the hard Himalayan climate, they handle the cold northern European winters better than most locals. Global warming is often brought up in discussions of the parakeets, but it is certainly only part of the story.
It helps, too, that the birds have a 35 year lifespan and few local predators, enabling them to breed freely.

As with any new species, the debate has raged about whether they are harmful to the ecosystem. Strangely reminiscent of the debate over human migrants, often the birds have often been accused of stealing the homes of the natives. The parakeets do nest in tree cavities also used by jackdaws, owls and woodpeckers – but there is little evidence that native species are being muscled out. 

The also provide a food source for Britain's embattled birds of prey. Owls and peregrine falcons have been know to eat them. Charlie and Tom, two city dwelling falcons monitored by Nathalie Mahieu, often bring back parakeets as food.
Of more concern is the new arrivals’ effect on plants and trees. By 2009 their numbers in the UK had grown so much that they were added to the “general licence” of species, which can be killed without individual permission if they are causing damage.

And Parrotnet, am EU funded research project studying the development of parakeet populations across Europe, has warned of the risk they pose to agriculture. In their native India, the parakeets are known to cause widespread damage to crops. As agriculture develops in the UK in line with warmer climates, crops such as maize, grapes and sunflower will become more popular. In India the birds have been documented as reducing maize crops by 81 per cent.

So the parakeets remain divisive. Environmentalist Tony Juniper has disparagingly described them as “the grey squirrel of the skies”. By contrast, the University of York biologist Chris D. Thomas has argued that the parakeets should be left free to move and breed. He sees those wary of the parakeet boom of “irrational persecution” of the bird.

For good or ill the parakeets are here to stay. As so often with migrants of all kinds, there has been some unease about the impact they have had – but the birds, popular amongst Londoners, certainly add colour to the city. Thriving in the urban environment thousands of miles from their natural habitat, they are a metropolitan bird for Europe’s metropolitan cities. 

Want more of this stuff? Follow CityMetric on Twitter or Facebook