Flooding: Before & After

Before a Flood Strikes —Consider building modifications

If your existing property is in a flood plain, you may wish to make structural changes to protect it. If you are building a new structure, there are important things you should consider.

The first step in either case is to make a thorough study of flood elevation levels and the flood history of your area. Contact your local public works or soil conservation office for this information.

If you cannot avoid building in an area that has a possibility of flooding, consider building your home on pilings so flood waters would flow beneath the structure. Consider a home built on well compacted fill or one with minimum damage. Homes can be attractive and still meet this need.

If your existing home is in a flood-prone area, there are ways to protect it from flooding in some cases. These methods require modifications in construction that must be done in advance. They can be broken down into two types, permanent and emergency.

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Permanent Protection

Permanent modifications involve changes to the home or the area surrounding the home which prevent flood waters from reaching the interior of the structure. These include:

• Construction of berm walls, subdivision levees and retaining walls (either attached to the home or out away from the home). With each of these, several options exist in terms of materials and appearance. These are costly alternatives for protection of your home; however, comparing those costs against the cost of restoring a flood-damaged home may make the relatively minor construction more appealing.

• Jacking the house up off its present foundation (a more costly alternative for some houses) and supporting it at a height well above anticipated flood levels. Usually, a house mover is contracted to raise the house and a second contractor may be involved in building new foundations, the new ground level may be left open or closed in for additional living space. If it is to be closed in, select finish materials which require minimal protection from flooding and are easily cleaned up after flooding occurs.
  
  Between pilings, use:

  • Removable panels
  • Screens or Louvers
  • Collapsible Block
  • Hinged Panels
  
  While all of the alternatives are costly, they may serve to raise property values if well done. They will definitely reduce the risk and extent of future flood damage.

Each home and site offers a specific set of problems. Secure the services of experienced, licensed architects or engineers before making major modifications.

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Emergency Protection

The emergency procedures involve wrapping the home with polyethylene and using a sump pump to remove water that might seep through. This procedure requires four to five hours work and depends on the structure itself to support the pressures associated with the flood waters. Although structural failure is rare, significant damage is possible if the flood water rises more than two feet above the floor.

To be successful, this procedure requires you gather materials in advance and that there is enough time before the flood waters reach your home. You will need the help of four to six people and it will cost $500 - $700.

Procedure for "wrapping" a home:

• Dig a trench approximately 8 inches deep and 8-10 inches wide around the perimeter of the house, right at the base of the structure,
• Place a 2-inch diameter PVC pipe at the bottom of the wall just above the trench. The purpose of this pipe is to carry any water that may leak around the polyethylene back to the sump pump for removal.
• Drill one-half-inch holes approximately 8 inches on center.
• Place the polyethylene film 6 mils thick and 8 feet wide, on the wall to a height of about 4 feet and attach it with duct tape and masonry nails. Drape the rest of the film down into and across the trench. Use loose sand to fill the trench on top of the polyethylene.
• The polyethylene film, although waterproof, is not very strong. Bridge any open areas around the home before you wrap with polyethylene. Use 2" X 4" and 2" X 6" lumber to construct beams that allow you to span these open areas. Use half-inch plywood sheets on the outside of the beams before placing the polyethylene over the plywood.

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