In September 2024, Hurricane Helene made landfall in Florida, leading to impacts in coastal areas but most prominently driving intense precipitation north and westward in areas far from the coastline. Across Appalachia, the heavy rainfall caused riverbanks to overflow, turning small creeks into rushing rivers that swept houses off foundations. Over two hundred people died, thousands of homes were damaged or destroyed, and whole towns were leveled in the deluge (Hassan and Taft 2024).
The severity of the floods caught many off guard, particularly in inland towns like Asheville, North Carolina. For years, Asheville had been considered a “climate haven,” a place that would be safe from climate change–related disasters like extreme flooding. After all, the U.S. government’s flood risk maps didn’t convey that this level of flooding could happen in Asheville. According to the flood maps produced by the Federal Emergency Management Agency (FEMA), the standard reference for flood risk in the country, only 2 percent of properties in western North Carolina were marked as having a special risk of flooding (Crowe et al. 2024).
What happened in Appalachia last fall is not unique. When Hurricane Sandy hit New York City in 2012, over half of the homes that were damaged were not included in the flood-hazard zones on FEMA’s maps (Shaw et al. 2013). All across the country, from Dallas, Texas, to Barre, Vermont, residents have been hit by major flooding in areas outside of flood-hazard zones, without adequate preparation or flood insurance to help them through the crisis. According to FEMA, 40 percent of National Flood Insurance Program claims made between 2017 and 2019 were for properties that were either outside of FEMA’s flood-hazard zones or in areas that FEMA had yet to map (Oakford et al. 2024).
These extreme-weather events expose shortcomings in both how flood risk is calculated and how these risk maps are used and interpreted. These challenges carry significant ethical implications, particularly as vulnerable communities suffer disproportionate damage from extreme flood events (McGee 2021). As climate change amplifies both the frequency and severity of flooding events in the years to come, there is an urgent need for a more nuanced approach to modeling and communicating risk through maps, and for more equitable applications of these maps.
Limitations of Calculating and Representing Flood Risk
Calculating risk is tremendously difficult, as it requires estimating the probabilities of uncertain events—it’s an attempt at predicting what might happen in the future. In order to assess future conditions, it often makes sense to look at past trends. FEMA’s maps largely rely on historical data in order to determine current flood risk; the “Special Flood Hazard Areas” are determined by where there is a 1 percent chance of flooding in any given year, derived from historical data. While this may have once been a reliable method, with climate change, weather patterns are rapidly shifting and sea levels are rising. Future conditions will no doubt look different than in the past, but there is a great deal of uncertainty in modeling exactly where, to what extent, and with what likelihood future floods will occur.
Flood risk map-makers also face significant technical challenges with regards to predicting hydrological flows of different flood types. FEMA’s maps only represent the risk of river floods and coastal floods, both of which are linked to specific geographical features. If you live near a body of water, it’s relatively straightforward to understand how your home may be exposed to a flood risk. If you live in an area that is farther inland or away from any rivers, in contrast, you might not realize you face any flood risk based on these maps. What isn’t included on FEMA’s maps, however, is the risk of flash floods. Flash floods can happen anywhere, regardless of proximity to water bodies, and they occur rapidly, within just a few hours of heavy rainfall. Flash floods are particularly difficult to predict, and when they happen, they can be life-threatening.
To make it even more complicated, all of these flood types can occur simultaneously, creating compound flood events. For example, as Hurricane Helene approached the coast of Florida’s Big Bend region, it brought a 15-foot (4.5-meter) storm surge that coincided with high tide, causing coastal flooding. At the same time, the hurricane brought intense precipitation, exacerbating coastal flooding and creating flash-flood conditions in some inland areas. When the storm passed over Appalachia’s mountainous terrain, it caused severe river floods throughout the region, compounding the overall destruction.
When these different types of floods interact, the overall risk is amplified, creating a highly dangerous hazard that is greater than the sum of its parts. As Andrew Kruczkiewicz, a senior staff associate at the Columbia Climate School, explained, “There are so many direct and indirect relationships between these risk factors; they have a nonlinear relationship with each other. They are risk multipliers in themselves.”
Flood risk maps, like all cartographic representations, inherently simplify complex realities. This simplification becomes particularly challenging with all of the uncertainties and complexities around how different flood types interact and will interact in the future under changing climate conditions. Given these challenges, it is unrealistic to expect a single flood risk map to capture the full spectrum of potential risks. Instead, a more nuanced approach that acknowledges these limitations and uncertainties is necessary for effective flood risk assessment and response.
Challenges with Using Flood Risk Maps
While some degree of uncertainty in building flood risk maps is inevitable, the ways these maps are used and interpreted can also have significant impacts on outcomes for communities affected by flooding. FEMA’s mission is to “help people before, during and after disasters,” yet too often, the agency’s flood maps are not appropriately applied, inadvertently misleading communities into underestimating risk.
These shortcomings arise from the different ways these maps are used. Today, communities often use FEMA’s flood maps to learn about their flood risk, but these maps were initially designed to protect property by determining infrastructure regulations and insurance rates through the National Flood Insurance Program (Landau 2024). Sometimes, these different purposes can clash, at the expense of public safety.
FEMA’s maps outline Special Flood Hazard Areas, and any building that falls in one of those areas is required to incorporate flood-proofing measures, such as elevating mechanical equipment or using flood-resistant construction materials. However, because FEMA’s maps are based on present-day flood risk, significant challenges can arise when those same maps are used to inform adaptation decisions about infrastructure that will stand for decades into the future. Buildings that are constructed today may appear to be in a low-risk zone now, but in five, fifteen, or fifty years, that risk may significantly increase, putting future residents at risk if flood-proofing measures weren’t required.
FEMA’s flood maps are also a factor in how insurance premiums are determined under the National Flood Insurance Program. Any homeowner who lives in a Special Flood Hazard Area is required to purchase flood insurance if they want a federally backed mortgage. Oftentimes, real-estate developers and local governments are resistant to expanding flood hazard areas, because that would increase insurance premiums and require costly flood adaptation measures for buildings that previously weren’t in the high-risk zone. This creates a conflict between economic interests and public safety, as municipalities and developers have a financial stake in resisting map updates that may more accurately reflect flood risk. When FEMA proposed a new flood risk map in New York City that would expand the floodplain by 80 percent in 2015, the city disputed the change; since then, FEMA and the city have been working together to create a new map (Slowey 2015). When communities rely on these same insurance and zoning maps to learn about their current and future flood risk, it can create a misleading perception of risk.
To address these conflicting map uses, some cities are building their own specialized maps that address these different purposes. For example, New York City has been collaborating with FEMA to create updated maps for flood insurance and zoning requirements, while the city has also developed its own set of maps depicting long-term climate projections of coastal flooding and of inland stormwater flooding with the purpose of educating communities (NYC Hazard Mitigation Plan, n.d.). Together, these maps provide a fuller sense of different types of flood risk over time, and New Yorkers can access tools like the NYC Flood Hazard Mapper and the NYC Stormwater Flood Maps to learn how their neighborhoods may be affected.
Beyond impacting communities’ awareness of flood risk, FEMA’s maps can also inadvertently exacerbate inequality. Low-income households are significantly less likely to have flood insurance or the money necessary for flood-proofing measures or recovery efforts, leaving these communities vulnerable to financial devastation after a disaster (McGee 2021). FEMA provides some mitigation grants to help communities implement flood-proofing measures, but the distribution of these funds has been highly unequal, with more money allocated to majority white, high-income areas where property values are higher (McGee 2021). In addition to informing the distribution of flood mitigation grants, FEMA’s maps also serve as the foundation for the National Flood Insurance Program, which has been shown to amplify racial inequalities in some areas. A study led by Kruczkiewicz found that within relatively white counties in North Carolina, towns with a high non-white population were less likely to receive national insurance benefits compared to other majority-white areas in the same county (Kruczkiewicz et al. 2023). In recent years, FEMA has implemented some measures to more equitably distribute disaster relief and mitigation funding, though the effects of long-standing systemic inequalities continue to produce unequal outcomes.
By influencing insurance programs, mitigation funding, development decisions, and public perception of risk, FEMA’s flood maps can be used in ways that have severe ethical implications, worsening outcomes for vulnerable communities. More advanced flood risk projections may improve the accuracy of FEMA’s flood maps, but better data alone does not necessarily translate to meaningful, equitable disaster preparedness and response on the ground. As Kruczkiewicz explained, “Focusing solely on the pursuit of developing ‘better’ maps isn’t going to save the most vulnerable, and it could lead to an increase in disproportionality of impact from flood. […] Even if everyone has access to a forecast—it could be the most accurate forecast—if it’s increasing the gap, it’s not doing its job.”
In order to fully realize FEMA’s mission of assisting people through disasters, a critical examination of how these maps are used, who they are helping, and who they are harming is essential. The complexities of how flood risk maps are calculated, interpreted, and applied highlight the need for a more nuanced, ethically grounded approach to disaster preparedness that considers the needs of all community members. Ultimately, the most effective, equitable approach may require less mapping and more action.
The present-day flood risk map in New York City, based on FEMA’s Flood Insurance Rate Maps (FIRMs). Source: NYC Flood Hazard Mapper
The projected 2080 flood risk map in New York City, based on projections by the New York City Department of City Planning. Source: NYC Flood Hazard Mapper
The projected 2080 stormwater flood risk in New York City, based on data from the Department of Environmental Protection. Source: NYC Stormwater Flood Maps
Sources:
Crowe, K. et al. (2024, October 13). Federal flood maps underestimated risk in areas hit hardest by Hurricane Helene. Washington Post. https://www.washingtonpost.com/weather/2024/10/13/fema-flood-maps-hurricane-helene/.
Flavelle, C. et al. (2020, June 29). New data reveals hidden flood risk across America. New York Times. https://www.nytimes.com/interactive/2020/06/29/climate/hidden-flood-risk-maps.html.
Hassan, A. and Taft, I. (2024, October 6). What we know about Hurricane Helene’s destruction so far. New York Times. https://www.nytimes.com/2024/09/29/us/helene-destruction-florida-north-carolina.html
Kruczkiewicz, A. et al. (2023). Are underserved populations left out of national flood mitigation efforts and facing greater impact? A method to assess racial inequality at the census tract level. Journal of Climate Resilience & Climate Justice, 1, 78–92. https://doi.org/10.1162/crcj_a_00005
Landau, M.D. (2024, October 11). Many Americans are buying homes in flood zones—and don’t realize it. National Geographic. https://www.nationalgeographic.com/science/article/flood-maps-fema-risk-insurance
McGee, K. (2021). A place worth protecting: Rethinking cost-benefit analysis under FEMA’s flood-mitigation programs. University of Chicago Law Review, 88.8. https://lawreview.uchicago.edu/print-archive/place-worth-protecting-rethinking-cost-benefit-analysis-under-femas-flood-mitigation
NYC Hazard Mitigation Plan (n.d.). New York City Emergency Management. https://nychazardmitigation.com/documentation/hazard-profiles/flooding/
Oakford, S. et al. (2024, December 6). America underwater: Extreme floods expose the flaws in FEMA’s risk maps. Washington Post. https://www.washingtonpost.com/climate-environment/interactive/2022/fema-flood-risk-maps-failures/.
Rook, T. (2023, August 8). FEMA maps said they weren’t in a flood zone. Then came the rain. Grist. https://grist.org/extreme-weather/federal-maps-said-they-werent-in-a-flood-zone-then-came-the-rain/.
Shaw, A. et al. (2013, December 6). Federal flood maps left New York unprepared for Sandy — and FEMA knew it. ProPublica. https://www.propublica.org/article/federal-flood-maps-left-new-york-unprepared-for-sandy-and-fema-knew-it.
Slowey, K. (2015, December 10). Flooded with controversy: Developers, owners challenge new FEMA floodplain maps. Construction Dive. https://www.constructiondive.com/news/flooded-with-controversy-developers-owners-challenge-new-fema-floodplain/410537/
Tempus, A. (2020, November 19). Presto chango: How flood map revisions allow building in risky areas. Investigative Reporting Workshop. https://archive.investigativereportingworkshop.org/news/presto-chango-how-flood-map-revisions-allow-building-in-risky-areas/.
