[b]By the end of this century, sea levels could rise worldwide by three feet or more, inundating coastal cities and spurring catastrophic storms roughly every three years.

In Africa, at least 20 cities — including Cairo, Egypt; Cape Town, South Africa; and Kinshasa, Democratic Republic of the Congo — are especially vulnerable to rising seas. At the top of the list is Lagos, Nigeria, a fast-growing, low-lying coastal city of 13 million. By the year 2100, sea levels there are expected to have risen nearly 4 feet.

Houses and roads in Lagos are built on sponge-like terrain that was once sandbars, lagoons, and mangrove swamps. Lagos is also riven with a confluence of inland rivers, adding to its vulnerability to flooding. In 2011, intense rainfall flooded homes, overwhelmed sewers, and turned streets into rivers. Hardest hit in such events are the poor. Slums already hold 70 percent of people in Lagos, a city that draws 3,000 more residents every day.

In the face of that watery future, Nigerian architect Kunlé Adeyemi, founder of the firm NLÉ and a recent visitor to Harvard, proposes a solution: Build houses that float. His African Water Cities Project envisions a future in which modular coastal dwellings are built on platforms stacked with flotation devices.

Adeyemi delivered a lecture on the project March 7 at Harvard’s Graduate School of Design (GSD). That week and the next, he was one of four architects on campus who work in Africa, attending one conference on African development and another on public spaces.

Their projects are spread out in South Africa, Tanzania, Uganda, Liberia, Rwanda, and Nigeria. But they share the idea that architecture can be a powerful tool for social justice, including an appreciation of all things local, from labor and crafts to materials and design.

For his floating cities, Adeyemi had a ready-made local model: Makoko, a slum Venice of 2,200 buildings and 150,000 people on the edge of Lagos. “Everything happens on water,” he said of what he called a “dream world” on the edge of the sea. “It’s an example of maximum urbanization with minimum means.” The streets are water, the cars are gondolas, and the houses are propped on stilts.

Inspired by the clever minimalism of the local residents, he showed a picture of a house with a lumber roof and a bamboo facade. Its owner stood near the kitchen space and open-air bathroom. “This man has all he needs,” said Adeyemi.

Makoko’s commerce is afloat too. In another picture, a woman rowed from house to house in a boat full of goods, sort of the local “mall,” he said. Century-old Makoko also provides Lagos with a third of its fish and most of its milled lumber.[/b]

One “seed,” afloat

Adeyemi’s prototype structure — he called it a “seed” — was started in 2011 and dedicated earlier this month. The Makoko Floating School is a three-story, 720-square-foot building afloat on a platform of recycled barrels and fitted with solar panels. Its louvered sides and peaked roof, sloping into a rainwater collection system, echo the aesthetics of the nearby houses. “It’s not quite a building,” said Adeyemi, “and it’s not quite a boat.”

Read more : http://news.harvard.edu/gazette/story/2013/03/a-vision-of-floating-cities/