Floodplain, Flood Zones & Elevation: Protect Your Business From Flood Damage

Each year, the United States suffers hundreds of millions or even several billions of dollars in flood damage. Small businesses, which are the economic and often social engine of many communities, can be the most adversely affected by floods. What’s more, flash flooding is the leading cause of weather-related deaths in the U.S—causing an average of about 200 deaths annually. Flood waters also can carry with them a range of health and environmental problems. In order to avoid water damage, it is important to check a floodplain map to ensure that your property is not located in a floodplain. By looking at floodplain maps and flood zone maps, one can see base flood elevation and flood zones clearly identified. Also, don’t forget the importance of waterproofing basement areas in your flood-proofing efforts. Basement waterproofing can mean the difference between a wet basement due to basement flooding and a dry one.

The Importance of Elevation

When it comes to flooding, there is no better solution than adequate elevation, aside from choosing a location well outside of a 500-year floodplain. If such a location is not possible, the best way to increase the safety margin against flood damage is to raise the elevation of your building above the 500-year flood elevation. Flood-proofing your building is another option to reduce damage. Through The National Flood Insurance Program (NFIP), there is extensive regulation of floodplain development at the community level.

Permits are needed for a wide range of activities including construction of new buildings, additions to existing buildings, and substantial improvement to the interior of existing buildings that are within the most hazardous flood zones. Part of the permitting process involves whether your building site is higher than the base flood elevation (BFE), which is the elevation at which your property has a 1 percent chance of flooding annually, as indicated on the NFIP flood maps. Major storms and flash floods can cause waters to rise higher than the BFE—therefore, it is always a good investment to build in a safety factor several feet above the BFE.

This safety zone is called “freeboarding.” For example, IBHS’ FORTIFIED for Safer Business Program™, a package of enhanced voluntary construction standards that greatly increase a new light commercial building’s durability and resilience to natural hazards, requires FORTIFIED buildings to be at least 3 ft above the BFE or above the 500-year flood elevation. There also are ways to retrofit your existing building so that it meets or exceeds BFEs. While only a structural engineer/design professional can determine what is right for your property, the options include raising foundation onto pilings or columns, or adding landfill, as long as “no impact” floodplain requirements are met.

  • When elevating a building so that the walking surface of the lowest floor is at the minimum elevation, areas under the BFE can be used only for parking and limited storage—under-floor bathrooms, utilities, and ductwork are not allowed.
  • Equipment, utility connections and all interior utility systems including ductwork must be elevated above the BFE. In addition, fuel and propane tanks must be properly anchored, since they can become buoyant even in shallow water.

The Vulnerable Basement

Even above the BFE or outside the floodplain, basements are prone to floods because water may flow down into them. They also may have an increased hydrostatic pressure exerted upon them when the surrounding ground is saturated. Recognizing that elevation is the best form of mitigation, there are a number of additional measures business owners can take to reduce the likelihood and scope of basement flood damage.

  • Thoroughly inspect your basement and the surrounding property for evidence of water entry and sources of water flow and leakage.
  • Correct potential problems (e.g., extend and redirect downspouts, re-grade sloping landscape, and caulk any interior wall cracks).
  • Basement walls should be designed to resist hydrostatic pressure.
  • Use flood-resistant materials where possible, including floor coverings, wall coverings, and wall insulation. Most flood-resistant materials can withstand direct contact with water for at least 72 hours without being significantly damaged.
  • Do not store valuable equipment, documents, or inventory in any crawlspace or basement where flooding is possible.