The hazards of the flood insurance system

The people of Atlanta are finding out this week what the people of Fargo Moorhead found out last March: You can’t depend on government flood maps anymore.

The maps are used to determine high- and low-risk areas in the event of flooding, but they’re also offering misleading ‘advice’ to homeowners who are trying to figure out the byzantine system of buying flood insurance. The Atlanta Journal Constitution reports today that the system is spelling financial disaster for many residents of the flooding.


But in reality, the maps aren’t nearly as reliable as homeowners might want them to be. They are often hopelessly outdated, especially in a rapidly-developing place like Atlanta where new homes and parking lots can shift the flood zone’s boundaries.

Even when the maps are up- to-date, they measure the flood expected to result from a storm that has a 1 percent chance of occurring in any given year. Storms can exceed that expectation. And even in lesser rainfalls, floodwaters can travel beyond the official zones because drainage systems may be blocked or overwhelmed. When that happens the water backs up and can rush into the homes nearby.

During the Red River flooding last spring in Clay County, we found only 190 homes inside the “flood plain” were covered by insurance. There were about 11,000 structures damaged or threatened by the flood.

  • Aaron

    This is a more common scenario than people might think. Most of the Flood Insurance Rate Maps (FIRM) were created in the 1970′s, and are just now starting to be updated. With such a boom in construction in the last 30 yrs, it is absurd to base finished floor levels for homes and businesses on flood levels from a time when a floodplain may have had less than 30% of the hard surfaces it has now. The responsibility of determining flood levels should be up to the local watershed districts and municipalities. The cost would be significant, but would undoubtedly be less than the cumulative damage caused to structures built in an inappropriate area.

    That being said, buildings are typically set 2-3ft above the 1% occurrence interval storm event. Stronger storm events can and do happen – causing flooding. We will never be able to ensure a flood-free nation, but I think investment in independent floodplain studies would significantly reduce the social and economic costs of flooding.