Climate change and urbanization are challenging cities in much of the world to find room for responsible housing for residents.

Rising sea levels repeatedly flood rapidly-growing slum areas, but residents have few options for homes further from coastlines. Floating cities, Dutch architect Koen Olthuis said in his recent TED Talk, could help cities and residents adapt to climate change and urbanization while they alleviate a host of urban ills.

Eight of the world’s 10 largest cities are located on the coasts, and 70 per cent of the world’s people is expected to live in cities by 2050. As such, it can be a challenge finding adequate room for housing at all levels of affordability in large cities. Olthuis  said two ideas must change in order to enable new solutions: the idea that cities are static, and the idea that cities are full.

In place of the more static cities of the past and present, Olthuis envisions a dynamic city that adapts to change easily.

“In an ideal world, we would have a city that is ready for buildings to change, so each time that something happens you can bring in new buildings,” he said.

He pointed out that cities were regarded as full in the past, until Elisha Otis developed the elevator and cities began to grow vertically. The next frontier, Olthuis believes, could be building where there is not even land.

“Our generation has to look at water; most of the big cities worldwide are next to the water; Tokyo, Hong Kong, New York, they all have water and we don’t use it, not for building,” he said.

Olthuis’ construction method uses blocks of rigid foam encased in concrete to create platforms that can span thousands of square metres. Platforms can be linked together for larger projects.

“We can build exactly the same house as we built on land, but then on water,” he said.

Married to the use of water for building are ‘city apps,’ which Olthuis describes as individual components that can be ordered from a supplier and added to a home, building, or neighbourhood. City apps, such as a sanitation or potable water app, could be leased by a city, business owner, or homeowner, constructed by a business elsewhere, and delivered as needed. Each app then could be used as long as needed, and then upgraded or transported elsewhere and re-used when the need is gone.

This model creates a market for private enterprise, Olthuis said, and also adds to cities’ flexibility and sustainability, while adhering to his concept of “scarless development.”

Cities become more flexible and sustainable when buildings can be moved and re-used easily and don’t need a foundation. Scarless development also furthers the sustainability of the projects, with Olthuis telling Inhabitat “the building leaves neither a physical footprint nor carbon footprint.”

Waterstudio, Olthuis’ architecture firm, is currently building the Communications App, a floating shipping container with 20 tablets and two television screens connected to the internet. The app will be delivered to Kampala, Uganda, when complete.

Building on water also provides opportunities for a more sustainable approach to heating and cooling. His concept for a floating mosque for the United Arab Emirates, for example, sees seawater recirculated through the walls to cool the building.

One project currently under development is The Westlands in the Netherlands. The Westlands will include floating social housing, floating apartment buildings and floating islands. The site is currently a polder, a low-lying area of land that’s protected by dikes and pumps. When the project is complete, the land will be inundated to a depth of about two metres.

Floating cities also offer increased safety in severe conditions such as earthquakes and hurricanes.

“We have cities all over the world that are threatened by floods,” Olthuis said, adding that floating buildings can rise with floodwaters, and can move up and down when pounded by hurricanes.

“Building on water is more safe than building on land,” he said.