An online mapping system operated by the Federal Emergency Management Agency puts flood information about your home at your fingertips.

The mapping tool predicts the potential for flooding, even in areas that may not have seen high water for a century or more, but few Americans are aware of the system.

Most Americans can enter a street address and get a result.

The system is useful for people trying to decide on their own whether or not to evacuate in an extreme weather situation such as Hurricane Harvey.

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In the Washington area, the system shows that floodwaters could get as far as the Federal Triangle and the Ellipse in an extreme flooding scenario.

The National Weather service also provides online predictive flood mapping to the public in the D.C. area. The model can be used to predict flood impact far beyond the highest historic flood.

It is possible to model flood levels in the Potomac near the Tidal Basin of 18 feet. The highest historic crest is just over 11 feet. The National Weather Service model shows water could come within a block of the White House in the most extreme scenario envisioned.

Emergency Planners in Washington say the city has identified as many as 100 shelter locations in the city. Approximately one in 20 residents have disabilities or illnesses that would make them vulnerable and in need of assistance in the case of an evacuation.

Regardless of the type of emergency, DC Homeland Security and Emergency Management Agency spokesperson Nicole Peckumn says every person should be prepared for an extreme event.

"Be aware. Make a kit, Have a plan," said Peckumn.