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alternative to pier raising houses
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The Buoyant FoundationAn alternative approach to flood protection for
existing homes in New Orleans and S. Louisiana
Elizabeth C. English, PhD Associate Professor
University of Waterloo Ontario, Canada
Aerial photograph of New Orleans after Hurricane Katrinahttp://qhst-seniors.blogspot.com/2008/01/teaching-levees.html
Why Use Buoyant Foundations?
Why Use Buoyant Foundations?
In the aftermath of Hurricanes Katrina and Rita, home-owners in low-lying areas of South Louisiana are facing the issue of elevating their houses to comply with the new Base Flood Elevation (BFE) requirements. In addition, many New Orleanians who are not required to elevate their houses remain concerned about their safety in the absence of substantially improved levees.
New Orleans, 8 Sept 2005photo by E. C. English
Why Use Buoyant Foundations?
Permanently elevating a house, perhaps by as much as 12-15 feet, may reduce the risk of flooding but it creates new problems, such as difficult access to living areas, loss of neighborhood character and an increase in the vulnerability of the structure to wind damage. With permanent static elevation, even if a house is raised to the BFE or higher, it can still flood in an extreme event. In the meantime, residents must live with daily inconvenience and a reduced quality of life in the hope of avoiding flooding in a future event that is statistically very rare indeed.
http://www.streetphoto.com/images/New_Orleans_Flooded_Blue_House.jpg
REBUILD SAFELY
Why Use Buoyant Foundations?
A look at floating docks and houseboats suggests that there is an alternative approach, one that allows homes to remain close to the ground under normal conditions but rise as much as necessary, even above the BFE, when flooding occurs. There are existing precedents of cost-effective amphibious houses, or houses that normally rest on the ground but float on buoyant foundations during a flood, both abroad in the Netherlands and at home along the rivers and bayous of South Louisiana. Existing buoyant foundation in So. Louisiana
photo by E. C. English
FLOAT WHEN IT FLOODS
Why Use Buoyant Foundations?
Why not capitalize on the advantages of buoyant founda-tions in the rebuild-ing of New Orleans and flood-prone areas throughout South Louisiana?
Existing buoyant foundation in South Louisiana photo by Stuart Broussard
Problems with Elevated HomesPermanent static elevation is much more expensive Access is difficult – especially for the elderly & disabledGreater risk of wind damage in a future hurricaneCreates gap-toothed effect in the neighborhoodHomes lose relationship to the streetLoss of neighborhood character
Elevated homes at Raccourci Old River, Pointe Coupee Parish, LA photos by D. D. Ewing
Is this what we want to see in New Orleans?There must be a better way.
BUOYANT FOUNDATIONSCreate homes that float in a flood
AdvantagesHouse remains close to the ground Less susceptible to hurricane wind damageElevates house to exactly what is required to
stay above water, even if above BFEAlleviates problem of soil subsidenceLooks essentially the same as before KatrinaOriginal traditional architecture is preserved Neighborhood retains original character
The Netherlands builds new amphibious homes(At less than 5% increase in cost overthe cost of conventional construction)
Precedents
New homes in the Netherlands photos courtesy of Toine Smits, Radboud University Nijmegen, Netherlands
New amphibious homes in Maasbommel, Netherlands
photos by Hans van Beek
And here at home in Louisiana --
Buoyant homes at Raccourci Old River, Pointe Coupee Parish, LA photos by D. D. Ewing
Louisiana ingenuity at work!
Average cost of buoyancy system is around $5,000
Buoyant homes at Raccourci Old River, Pointe Coupee Parish, LA
When the Mississippi River rises in the spring, it floods Old River -- this happens almost every year, sometimes several times.
Dry in September Flooded in February
For over 30 years, amphibious houses at Raccourci Old River have been rising and falling reliably with the level of flooding of the Mississippi River.
Buoyant foundations are not new!
Dry in September Flooded in February
So why fight floodwater
when you can float on it?
How It Works
Figure Created by Ben Morvant
It basically works like a floating dock. A steel frame that holds the flotation blocks is attachedto the underside of the house. There are four “vertical guid-ance” poles not far from thecorners of the house. Thetops of the poles are attached to the steel frame. The poles telescope out of the ground, allowingthe house to move up and down. Utility lines have either self-sealing “breakaway” connections or long, coiled “umbilical” lines. When floodingoccurs, the flotation blocks lift the house, with the steel frame transferring the forces between thehouse and the blocks. The vertical guidance poles keep the house from going anywhere except straight up and down on top of the water.
Section drawing of a shotgun house with a buoyant foundation installed, showing buoyancy blocks under the house and vertical guidance posts that telescope out of the ground
Figure Created by Stuart Broussard
How It Works
A steel frame attaches to the underside of the house and holds the buoyancy blocks off the ground. The house remains sitting on its original piers after the buoyant foundation has been installed.
How It Works
Existing ShotgunHouse
Shotgun House Elevated to 6ft
Shotgun House on a Buoyant Foundation
Figure Created by Stuart Broussard
The addition of a buoyant foundation has minimal visual impact
Figure Created by Stuart Broussard
Even less with bushes!
Figure Created by Stuart Broussard
Existing Condition House Elevated to 6 feet House on Buoyant Foundation
Comparison of 3 Conditions
Existing House
House Elevated to 6ft
House on Buoyant Foundation
Existing House
House Elevated to 6ft
House on Buoyant Foundation
Now add water. . .
Existing House
House Elevated to 6ft
House on Buoyant Foundation
Which house would you choose?
Five LSU Mechanical Engineering students built a platform with a buoyant foundation to test the design for flotation and stability:
Scott Schroth Dustin Husser Dustin EwingMatt GuidryBen Morvant
Students from the LSU Hurricane Center added a house frame and built the flood tank to run the tests:
Stuart Broussard Ezra Boyd
Setting the piers
Adding the platform
Attaching the metal frame
Setting the vertical guidance poles(Note pole design has since been changed to telescoping poles)
The buoyancy blocks
Sliding sleeves go around the posts
Completed buoyant foundation
Adding the house frame and flood tank
House frame almost complete
Moving the platform to put down a liner
Installation of tank liner
A layer of sand holds down the liner
Now add water . . .
LIFT-OFF!
Now we're floating
Add more water and the piers go under
Resting on the water
Aerial view
Water barrels and sandbags are added to simulate weight of house and contents
Moving the sandbags to tilt the house
Testing complete!
In the news
Dr. Elizabeth English LSU Hurricane Center,[email protected] Associate Professor- Research
Dr. Marc Levitan LSU Hurricane Center, Director [email protected] Dept of Civil Engineering,
Associate Professor
Dr. Leslie Rosso Dept of Construction Management, [email protected] Associate Professor
Dr. Warren Waggenspack College of Engineering, [email protected] Associate Dean
LSU Faculty Team
LSU Student TeamsMechanical Engineering
Hurricane Center
Scott Schroth Dustin Husser Dustin EwingMatt GuidryBen Morvant
Stuart BroussardEzra Boyd
Weidlinger Associates Inc.Innovative Technology Group Inc. J P Morgan Chase Bank Capitol Steel
Corporate Sponsors
Flooded shotgun house, New Orleans, 8 Sept 2005 photo by E. C. English
Let's be sure this never happens again
Thank you for visiting our website www.buoyantfoundation.org