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 They are often hopelessly outdated, especially in a rapidly-developing place like Atlanta where new homes and parking lots can shift the flood zone’s boundaries.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.