Even a small amount of water inside a home can cause costly damage. Here’s how to assess your flood risk and what to do if you’re in the danger zone.

It’s a mystery to me why they weren’t taking proactive steps to move structures,” said Syracuse University associate professor Sarah Pralle.

FEMA is anticipated to open a 90-day public appeal and comment period in the winter where property owners can formally challenge the flood zone designation but they must provide scientific or technical data to back up their request.

The risk of the catastrophic flooding that struck Texas Hill Country as people slept on July 4 and left at least 120 dead was potentially underestimated by federal authorities, according to an ABC News analysis of Federal Emergency Management Agency data, satellite imagery and risk modeling.

On average, it takes five to seven years to develop and implement a new FEMA Flood Insurance Rate Map. As a result, many maps across the U.S. are significantly out of date, often failing to reflect current land use, urban development or evolving flood risks from extreme weather.