Flood Damaged Buildings

Flood Damaged Buildings: excerpts from FEMA Publication 348 “Protecting Building Utilities from Flood Damage”, June 1998.

Floodplains are home to almost 10 million households Nationwide. In an average year, 150 lives are lost and over $3 billion in property damage occurs from floods (1998). A large proportion of flood damage is incurred by service equipment and building components such as furnaces, water heaters, air conditioning compressors, water supply pipes, septic tanks, electrical wiring and control panels, and insulation.

Buildings should be designed and constructed to avoid or resist the hazards that exist in floodplains, including:

  • Lateral hydrostatic and buoyant forces caused by standing or slow moving floodwater;
  • Hydrodynamic forces from moderate or fast flowing floodwaters as well as ocean wave action;
  • Impact forces on buildings caused by floating debris;
  • Localized ponding of floodwater caused by poor drainage on the property;
  • Erosion and scoring caused by the removal of soil, beach sand and other loose material by moving floodwater;
  • Mudslides and debris flows in alluvial fan floodplains;
  • Movable stream beds caused by erosion;
  • Site specific soil or geotechnical considerations such as soil pressure, bearing capacity, shrink-swell potential, and permeability; and
  • Contamination of the property caused by dissolved chemicals, sediment, suspended solids and other pollutants contained in the floodwaters.

It is important therefore, that designers of buildings in floodplains account for all possible hazards that buildings could encounter.

Flood inundation can cause serious problems and costly repair bills for homeowners. The force of moving water and floating debris can destroy equipment leading to costly replacement bills.  Other damaging impacts that typically occur include:

  • Inundation of electrical switches, control panels, and receptacles causes short circuits, corrosion, and the possibilities for electrical shock hazards and fires.
  • Inundation can cause floatation of underground and above-ground tanks (septic, fuel), severance of pipe connections, and rupture of tanks.
  • Flood induced damage to pipes, septic tanks, manholes, and on-site wells can contaminate wastewater and water supply systems thereby rendering an otherwise habitable building uninhabitable, and can cause hazardous waste to be released into floodwater.

If your home or business is damaged by a flood, keep in mind that it is always possible that your building will be flooded again in the future. Give serious consideration to using flood-resistant building materials as you repair and rebuild your damaged building. Elevating the building above the 1% annual chance flood elevation (100-year flood elevation) is also an effective solution plus it will help the homeowner obtain a better flood insurance policy rate.

Helping Disaster Survivors:

Recovering from a disaster:

Financial Assistance: 

More Information:

Answers to Questions about Substantially Damaged Buildings  FEMA 213


Repairing Your Flooded Home FEMA L-198


County of Ventura Instructional Handout: 50% Substantial Improvement

Reduce Your Risk from Natural Disasters Brochure L231
Homeowner's Guide to Retrofitting fema_l235_brochure_cvr