Residents of the La Vita Bella nursing home in Dickinson, Tex., sit in waist-deep floodwaters caused by Hurricane Harvey on Aug. 27. Authorities said all the residents were safely evacuated from the facility. (Trudy Lampson via AP)

One of the most heartbreaking photographs from Hurricane Harvey shows a handful of nursing home residents sitting in wheelchairs in waist-deep water. Their assisted living facility, like countless other properties affected by the flooding in Texas, was located outside the 100-year flood hazard zone.

Here’s what this means: These areas were not considered at high risk for flooding, according to the National Flood Insurance Program’s flood-mapping program, or at least not high enough to carry mandatory flood insurance. The 100-year flood zone designates areas that have a 1 percent chance of flooding each year, a term that can be misunderstood to mean it occurs only once every 100 years. The 100-year flood standard (and 500-year standard) is based on probability, not history.

And here’s the big lesson from Hurricane Harvey: The U.S. government’s flood zone designation, and the maps based on it, may not predict future flood risks accurately, particularly as climate change alters sea levels and weather patterns.

My research focuses on flood mapping under the National Flood Insurance Program (NFIP). While the NFIP has protected lives and saved billions of dollars in damage since Congress enacted it close to 50 years ago, it has suffered from policy neglect and political interference. Moreover, the flood insurance mapping program is ill equipped to help us adapt to climate change.

FEMA maps may be outdated

The Federal Emergency Management Agency (FEMA) administers the NFIP and uses the flood hazard maps to set flood insurance rates and flood mitigation regulations. After an initial investment in mapping the nation’s flood zones in the 1970s, FEMA’s efforts to extend and update flood maps stalled when funding for the program stagnated between 1980 and the early 2000s. During this time, individuals were making decisions about where to live, and communities expanded with new development — and these plans relied on increasingly outdated maps. Not surprisingly, development in flood-prone areas continued, including communities that would later be designated part of the NFIP program.

In the early 2000s, Congress finally funded a map modernization program to update the nation’s flood maps. This program has been only partially successful. One problem is that FEMA used a significant amount of funding to digitize existing paper maps, rather than fund new engineering studies to improve their accuracy. A second issue is that FEMA prioritizes remapping projects based on population, meaning that rural areas that are likely to see new development are often unmapped.

The politics of flood mapping

And there’s a third problem: Politics can shape the remapping process in ways that leave communities vulnerable. Local elected leaders are sensitive to their constituents’ concerns. So a good outcome for local politicians and their constituents would be to see a reduction in the size of the flood zone and the severity of the hazard designation — this means fewer homeowners must purchase mandatory National Flood Insurance, and there are fewer hurdles for local development projects.

FEMA remapping can work the other way, leaving homeowners who suddenly find themselves living in the 100-year flood zone understandably worried about the costs of flood insurance and the impact on property values. The larger remapping conversation then centers on the costs of revising the flood hazard zones rather than the risks associated with flooding.

FEMA lets local communities challenge the flood zone maps through an appeals process. For example, New Orleans negotiated for seven years with FEMA to convince the agency in 2016 that recent infrastructure projects reduced the city’s flood risk.

The result? The latest flood maps show that more than half of the population of New Orleans is no longer in the high-risk flood zone even though many residents live at or below sea level.

At times, local elected officials ask congressional delegations to contact FEMA officials on their behalf. FEMA may bow to this political pressure and reconsider the community’s flood maps and flood hazard zones in ways that leave vulnerable populations unnecessarily at risk.

It is important to note that many towns and cities across the United States have worked hard to mitigate their flood risk and plan for future flood scenarios. FEMA officials and flood experts acknowledge the efforts of these communities, especially those subject to frequent flooding — and also praise engineers and planners who try to steer local conversations toward risk reduction. But local bureaucrats are subject to political pressures from above and may not prevail over elected officials.

Individual property owners can also appeal if their homes are included in a flood hazard zone, saving themselves hundreds or thousands of dollars in flood insurance premiums if they can afford to hire a land surveyor. Lower-income residents are at a disadvantage in this process, being unable to afford an appeal or flood insurance premiums.

In my research in Syracuse, N.Y., the expanded flood zone finalized in the 2016 FEMA maps included some of the city’s poorest neighborhoods. Many of the African American residents are the first in their families to achieve homeownership and fear that inclusion in a flood zone means that their homes will be worthless and neighborhoods will be deserted. However, the solution is not to exclude such properties from the flood hazard zone, but to mitigate flood hazard risks, offer low-cost loans so homeowners can flood-proof their homes and subsidize their flood insurance to make it affordable.

The added challenge of climate change

Climate change is rendering many flood maps unreliable — even those recently updated with the latest technology. Flood insurance rate maps are static products, illustrating flood hazards based on historical data. History, however, may prove a poor predictor of the frequency and intensity of flooding because of sea-level rise, stronger storms and heavier rain events associated with climate change.

Without accurate maps that reflect future risk as well as current hazards, we cannot keep individuals, communities and the nation safe. And we will find it increasingly difficult to minimize property damage and protect critical infrastructure.

FEMA has embarked on a new mapping program called “Risk MAP,” designed to better communicate flood risk based on evolving factors such as real estate development and changing weather patterns. This is a welcome addition to FEMA’s mapping program, but the new program will be effective only if local communities and their leaders take these maps seriously.

Sarah Pralle is an associate professor of political science at the Maxwell School at Syracuse University. She is the author of “Branching Out, Digging In: Environmental Advocacy and Agenda Setting” (Georgetown University Press, 2006).