FEMA’s maps undercount the U.S. flooding risk by about 6 million homes — and some of those maps are two decades old

If your home isn’t in a federally designated flood zone, flooding might seem like someone else’s problem. No one requires you to buy flood insurance, and the map suggests you’re in the clear. But reality may be very different.

Mounting evidence reveals that significantly more homes are at risk of flooding than is indicated by FEMA’s 100-year flood maps – about 6 million more, and 14.6 million properties in all, by one estimate. The official maps are commonly outdated, and some are two decades old. Even when updated, they typically rely on historical flood data rather than future risk projections.

But there’s another problem that redrawing the lines won’t solve.

FEMA’s flood maps answer only one question: Is the water likely to reach my neighborhood? They don’t assess an individual home’s risks or what the impacts are likely to be when the water rises.

To understand the impact, more comprehensive data is needed, including the probable flood depth at the home, the building’s age and construction quality, and insurance coverage.

Same street, different risks

When these other factors are considered, your home’s true flood risk is far more complex than the map might seem to indicate.

The data shows how two houses on the same street can face radically different risks from flooding, even when located in the same flood zone – and where local governments can help.

One home may be newer, well maintained and covered by flood insurance. Another may be decades older, at the low end of the same street where water runs deeper during a flood, and is in poor repair and uninsured. The same storm would leave them in very different predicaments, with very different paths to........

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