buoyant foundation powerpoint

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,english@hurricane.lsu.edu Associate Professor- Research

Dr. Marc Levitan LSU Hurricane Center, Director levitan@hurricane.lsu.edu Dept of Civil Engineering,

Associate Professor

Dr. Leslie Rosso Dept of Construction Management, llrosso@lsu.edu Associate Professor

Dr. Warren Waggenspack College of Engineering, mewagg@me.lsu.edu 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