Learning to Live with Floodwater

July 20, 2015

For centuries we have fought flooding with defenses and suffered the consequences when they fail. But increasingly engineers and designers are looking into sustainable ways to cope with floodwater-to roll with it rather than trying to fight a losing battle against it.

The LifE (Long-term Initiatives for Flood-risk Environments) project for example, promotes non-defensive flood risk management developments. Instead of keeping water out, these are designed to allow floodwater to pass through with minimal risk to life and property. The argument is that flood-resilient development should give insurers and financiers the confidence to offer affordable, long-term policies and investment.

Recent years have seen growing interest in floating homes as away of developing property in flood-prone locations and/or where land is scarce. These are structures built to float on water, as distinct from boats adapted as dwellings. They can be found in Canada, the U.S., the Netherlands, Germany, and in several locations in Scandinavia. A 12-acre development has been approved for former docks in Glasgow, Scotland, and a 15-acre project incorporating homes, hotels, and leisure facilities is planned for London's Royal Docks.

A houseboat can drift away if it loses its moorings, but a floating home attached to piles won't. It can, however, rise and fall with water levels without sustaining any damage. Water, power,and sewage disposal services are flexible, so they can continue to function as the home shifts.

A more recent innovation is the amphibious home, which sits on dry land but can float when it needs to.  The UK's first amphibious home was completed in 2014 to the designs of Baca Architects, specialists in waterfront architecture and flood-resilient developments, and leaders of the LifE project.

This amphibious house is on an island in the River Thames near London, occupying the footprint of the home that stood on the lot previously. It sits snugly in an excavated "wet dock" with a mesh base that allows water to enter and escape naturally. The timber-framed structure has a waterproofed concrete basement that functions like the hull of a boat-it is entirely independent of the dock and becomes buoyant when water enters.

The house is currently able to rise up to 8 feet (2.5 meters) to cope with a 100-year flood event. This specification was arrived at by adding some wiggle room for climate change to worst-case scenario flood predictions from the UK's Environmental Agency. The home's ascent and descent are guided by four steel posts that can be extended if necessary to enable the home to cope with even higher flood levels in the future.

Baca Architects note that the London home cost about 20% more than a conventional structure without a basement because of the two foundation systems (dock and hull), but that costs were similar to those for a comparable home with a basement. 

Amphibious homes are not just for wealthy communities. The Buoyant Foundation Project was formed in 2006 to promote retrofitting New Orleans' traditional elevated wooden shotgun houses with buoyant (amphibious) foundations. Low-cost bamboo amphibious homes built over oil drum shave been designed for use in Southeast Asia, a pilot project home has been completed in Bangladesh, and Thailand is experimenting with various designs.

While they are not going to be the answer to the flood hazard-there is no one solution- amphibious structures are surely going to play their part. And we can expect to see a lot more non-defensive flood risk management in the future.

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