In an effort to indicate flood-prone areas, and the type of structures and residents that will be most impacted during flooding, researchers at the Furman Center for Real Estate and Urban Policy at New York University have launched an interactive map — FloodzoneData.us maps out national, state, county and census tract-level estimates of the housing stock and population in floodplains.
The floodplains, as defined by the Federal Emergency Management Agency (FEMA), are broken down into two categories:
the 100-year floodplain, which has a 1 percent chance of flooding every year; and the 500-year floodplain, which carries a 0.2 percent probability of flood inundation. The tool, released last week, uses the data made available by the National Housing Preservation Database, the U.S. Census Bureau, FEMA and the Furman Center.
In an accompanying data brief (PDF), demographics are broken down into three considerations: size and tenure, building age, and subsidized housing. Understanding the populations most at risk of flooding that will cause permanent displacement or ruined structures is necessary for policymakers, service providers and community members to confront the risks and prepare resilience plans.
According to the data, Florida, Texas and California have the largest number of households in the floodplain. While that's not surprising as these three states have large coastlines and are some of the most populated states, it is helpful in understanding the scale of the problem.
Understanding who is living in those units will also impact how emergency and resilience plans are implemented. While a majority of households are owner-occupied single-family houses, renters may have much different incentives for an expected flood. While homeowners may be more willing to retrofit a house, residents receiving housing assistance may have fewer options.
One pitfall of the available FEMA data is that it does not take rising sea levels into account. As sea levels rise, flooding will become more commonplace for a larger swath of the U.S. This map serves as a jumping-off point for city planners with the expectation that as the climate irrefutably changes, preparing for a rise in flooded households will have to become a standard practice.