Researchers identify key social vulnerability factors relating flood risks to buildings and crops

Floods are among the most destructive natural hazards, causing billions of dollars in economic loss each year.   By 2050, flood-related losses in the United States are expected to increase by 26%, with the share of properties facing at least a 1% annual chance of moderate to major flooding rising from 9% to 10%.

Though flooding is a widespread and relatively common hazard in the U.S., not all communities experience flood risks in the same way. In a study published in Natural Hazards, a Princeton-led research team examined the relationship between social vulnerability and flood risk, providing valuable insights into how flood impacts vary across different social and economic contexts.  

The Data and Methods

Social vulnerability - or the degree in which communities are more susceptible to harm due to their social, economic, or demographic characteristics - exacerbates flood impacts.  As policymakers pursue strategies that both reduce risk and inequity, social vulnerability indices have become valuable tools for guiding hazard mitigation investment.  However, most studies tend to use the same indicators, overlooking the nuances of how different hazard types and exposed assets are associated with different population vulnerabilities.  

Using advanced flood modeling and spatial analysis techniques, Dr. Sina Razzaghi Asl and colleagues address this research gap and provide a nuanced assessment of flood-related damage and risk.  By integrating social vulnerability indicators with flood risk data for crops and buildings, the researchers identified how factors like income, housing, and language barriers help explain patterns of economic loss.

“Our research highlights that the drivers of flood risk are not universal.  What makes a community vulnerable to building damage is not the same as what increases the risk to crops,” says lead author Sina R. Asl, a postdoctoral researcher at Princeton University’s C-PREE. “Understanding these differences is crucial for implementing effective flood mitigation and disaster recovery strategies.”

The Findings: Risk-Increasing vs. Risk-Reducing Factors

The study reveals that building flood risk is the most severe in urban areas with a high proportion of renters. This aligns with the widely-recognized vulnerability of renters, who often lack the financial resources to afford flood insurance and the legal right to implement structural flood protections.  

When it comes to buildings, areas with more mobile homes or vacant houses tend to face less flood risk. This doesn’t mean these places are safer or better equipped. Mobile homes are often less protective against floods, and vacant houses mean fewer people and properties are at risk in the first place. These areas, often rural and less populated, just have less to lose when floods hit. 

“Renters often have less capacity to prepare for or recover from flooding,” explains co-author Eric Tate, a Professor of Public and International Affairs at Princeton University. “They are more likely to face financial hardship and housing instability after a disaster.”

In contrast, areas with lower linguistic isolation tend to experience reduced crop risk, though the researchers caution that protective factors, such as soil type or local flood defenses, may also contribute to reduced crop risk, as indicated by the low explanatory power of these models. Lower crop flood risk is more strongly associated with employment in natural resource industries, such as farming and forestry. 

These findings remind us that flood risks hit communities differently. “What might appear as lower risk in some cases may instead reflect different patterns of exposure and social vulnerability,” explains Tate. “Flood vulnerability depends on where you are and the precariousness of your situation.”

The study also finds that as flood risk increases,  social vulnerability traits become more pronounced, with extractive industry employment, rental housing, and mobile home prevalence showing strong associations with elevated flood risk. 

“This means that as extreme weather events become more frequent, the disparities in flood risk will only grow,” says R. Asl.

How to Move Forward

With flood risks projected to rise in the coming decades, the researchers emphasize the importance of tailored, hazard-specific policies to protect vulnerable populations. Otherwise, implementing a one-size-fits-all approach will only continue to exacerbate the unequal burden of flooding shouldered by the susceptible communities.  

“Mitigation efforts need to account for the unique social and economic conditions that drive risk in different regions,” says Tate. “A one-size-fits-all approach won’t be enough to address the growing threats posed by climate change-driven flooding.”

The study, “Social vulnerability correlates of flood risk to crops and buildings,” was published in Natural Hazards on January 24, 2025.  The authors include Sina Razzaghi Asl (School of Public and International Affairs, Princeton University), Asif Rahman (California Governor’s Office of Emergency Services, Sacramento, CA), Eric Tate (School of Public and International Affairs, Princeton University), William Lehman (U.S. Army Corps of Engineers, Claremore, OK), and Oliver Wing (School of Geographical Sciences, University of Bristol).