By: Elizabeth English, Associate Professor, University of Waterloo School of Architecture. Email: firstname.lastname@example.org
As global climate change causes sea levels to rise and weather events to become more extreme, the occurrence of severe floods will become more common around the world. The large populations living in deltaic or riverine floodplain regions will be particularly severely affected, especially those living at the lowest levels of income.
There is increasing awareness worldwide that traditional flood mitigation strategies that alter the environment and create concentrations of risk, such as levee- and dike-building, only increase the likelihood of catastrophic consequences when eventual failure inevitably occurs. The greater the degree of artificial protection, and the confidence that builds in the communities living behind it, the more disastrous are the consequence when an unexpected failure occurs. New Orleans learned this lesson the hard way in 2005, when 80% of the city flooded due to numerous failures of the levee system in the aftermath of Hurricane Katrina.
Can we protect ourselves in other ways? Under certain circumstances, the answer is yes. Amphibious construction is an innovative, alternative, low-cost, low environmental impact flood mitigation strategy that can reduce the hazard vulnerability of housing in flood-prone regions and increase a community’s long-term disaster resilience. Amphibious foundations retain a home’s relationship to the ground by resting on the earth most of the time, but floating the house as high as necessary when flooding occurs. They can provide temporary elevation as needed, when needed, and do so with a sustainable solution that works in synchrony with floodwater instead of resisting it. Fully engineered and code-compliant modern amphibious foundations can be an appropriate and cost-effective flood mitigation solution for areas where rising flood waters are not accompanied by waves or high-velocity currents.
Successful amphibious foundation systems have been functioning for over thirty years in Raccourci Old River, Louisiana, where they provide more reliable and more convenient flood protection than can be obtained from permanent static elevation. In the last decade, the Netherlands has built amphibious housing in the Maasbommel region along the Maas River, which has a long history of severe flooding. In New Orleans’ Lower 9th Ward, the Make It Right Foundation completed the FLOAT House in 2009. Amphibious housing projects are also under development in the UK, France and Canada.
In a severe event where flooding may reach unanticipated depths, the fixed height of permanent static elevation (putting a house on “stilts”) may prove to be inadequate. The variable elevation provided by amphibious foundations accommodates not only short-term extreme flood levels but long-term land subsidence and sea level rise as well, by lifting the house to whatever elevation is necessary to keep it safely above water. Maasbommel in the Netherlands and Raccourci Old River in Louisiana both experienced extreme flood conditions in 2011, and the amphibious houses in both of these locations successfully demonstrated the reliability of this emerging technology.
As an alternative to permanent static elevation, a retrofitted amphibious foundation neither disrupts the appearance of a neighborhood nor necessitates the inconvenience of climbing long flights of stairs on a daily basis. How does such a retrofitted amphibious foundation work? It basically works like a floating dock. A steel frame that holds the flotation blocks is attached to the underside of the house. Four vertical guidance posts are installed not far from the corners of the house. Utility lines have either self-sealing ‘breakaway’ connections or long, coiled ‘umbilical’ lines. When flooding occurs, the flotation blocks lift the house and the vertical guidance posts resist any lateral forces from wind and/or flowing water. The house cannot go anywhere except straight up and down on top of the water. The entire system works completely passively, requiring no further preparations or interventions to perform safely in a case of catastrophic flooding.
The examples of amphibious construction cited above are all applications that serve moderate- to high-income populations in industrialized countries. However, amphibious technology has much to offer to rural and low-income populations in developing countries as well, either by inclusion in new low-cost housing projects or as a retrofit solution for existing communities. Amphibious construction can provide flood mitigation that is both more effective and considerably less expensive than other currently available options. It can dramatically reduce a community’s vulnerability both to regular, relatively mild, seasonal flooding, and to severe, otherwise-catastrophic flooding. Experimental amphibious homes have been constructed and are undergoing testing in Bangladesh, Thailand and Vietnam.
Amphibious foundations are a sustainable, low-impact flood proofing strategy that is rapidly gaining acceptance for applications around the globe. Our team is currently developing amphibious housing projects for flood-prone regions in Nicaragua and Bangladesh, for several Native American communities facing catastrophic land loss in south Louisiana, and for First Nations communities subject to severe seasonal flooding in northern Ontario and in Manitoba.