Protecting vital infrastructure as sea levels rise

hump we’re going to go through over the next few centuries?”

How to raise entire cities

When the town of Galveston in Texas was largely destroyed by a hurricane-driven flood in 1900, its citizens decided on a no-nonsense strategy to stop it happening again. They jacked up surviving buildings and shoved sediment in underneath, raising the town by 5 meters. This approach is unlikely to be copied any time soon, though. Lifting buildings is expensive, and would seriously disrupt the workings of an intricately wired-up modern city.

One alternative is using seawater to solve the problem. Andrea Comerlati of the University of Padua in Italy has proposed raising Venice by pumping water into the bedrock 700 meters beneath the city. According to his calculations it would take only 12 wells and 10 years to lift the city by 10 to 40 centimeters.

That could help in the short run but it is not even halfway toward compensating for a meter or more of future sea-level rise. It has another downside, too: if the pumps stop, the land will deflate and the city will sink. “To create permanent uplift, you need a layer of solid matter,” says Lawrence Murdoch of Clemson University in South Carolina.

His suggestion is to pump some sort of slurry down a network of boreholes. He reckons that if the geology is right, the high-pressure fluid will create horizontal fractures in the rock that spread out from each borehole, eventually joining up into one continuous layer. When the water gets squeezed out again, the solid particles left behind will form a permanent new layer.

Murdoch has done some small-scale experiments to show that the fracturing does work, and is hoping to get funding for larger field tests. This method has the potential to lift up land areas by several meters, he says. “And disturbance to life at the surface would be relatively slight.”

As a side benefit, you could get rid of waste materials this way. Murdoch suggests using ash from coal-fired power stations, which should set like concrete.

The method might even be used for larger coastal regions, rather than just cities. “I think that it would scale up fairly well,” says Murdoch. Inevitably, money will be the key. To raise a square kilometer of land by a meter would cost roughly $8 million, he calculates. While that might be a bargain for an island airport or a city in the developed world, it is unlikely to help farmers in Bangladesh. Lifting up the land may be strictly for the rich.