The Growing Health Impacts of Flooding in a Changing Climate: Insights from a Special Report

A recent report in The New England Journal of Medicine underscores the rising health risks associated with flood exposure driven by climate change. This international research highlights injuries, diseases, mental health harms, and the vulnerabilities of at-risk populations.

Background

Flooding, the most frequent climate hazard, has surged in both frequency and intensity due to climate change, affecting over 1.65 billion people worldwide between 2000 and 2019. Altered precipitation, soil moisture, and cryosphere dynamics drive this trend. Under high greenhouse gas emission scenarios, annual flood exposure could increase by approximately 14 times by 2071–2100, potentially impacting 97.6 million people annually.

The health effects of flooding include immediate fatalities, injuries, waterborne and vector-borne diseases, mental health issues, and disruptions to healthcare access. Vulnerable groups—such as children, older adults, and low-income communities—disproportionately bear these impacts. Further research is needed to understand long-term health outcomes and effective mitigation strategies.

Health Risks of Floods

Mortality

Floods directly cause fatalities through drowning, hypothermia, electrocution, and structural failures. Secondary deaths arise from exacerbated chronic illnesses, infectious diseases, and mental health conditions. A multi-country study showed a 2.1% increase in overall mortality within two months of flooding, attributed to disrupted healthcare, poor sanitation, and psychological stress.

Injuries and Environmental Hazards

Nonfatal injuries—such as cuts, fractures, and debris-related trauma—are common. Floods also mobilize hazardous chemicals, exemplified by Hurricane Florence, where toxic coal ash contaminated ecosystems. Additionally, improper generator use in disaster zones heightens carbon monoxide poisoning risks.

Spread of Infectious Diseases

Floodwaters foster waterborne diseases like leptospirosis and hepatitis, while overcrowded shelters increase respiratory infections. Stagnant water enables mosquito breeding, intensifying malaria and dengue risks. For instance, stagnant floodwaters boost mosquito activity, escalating outbreaks of mosquito-borne diseases. Contaminated water supplies also lead to gastrointestinal illnesses.

Noncommunicable Diseases

Flood-disrupted healthcare services worsen chronic conditions like hypertension and diabetes. For example, U.S. veterans affected by Hurricane Sandy experienced a 26% rise in uncontrolled hypertension a year after the event. Vulnerable populations face heightened risks of cardiovascular issues and cognitive decline due to reduced healthcare access.

Vulnerable Populations

Pregnant Women and Children

Flood exposure increases pregnancy complications and losses, often due to stress and infections. Children in low-income regions suffer disproportionately from undernutrition and severe wasting. Repeated flooding in India, for example, left children 3.37 times more likely to suffer from wasting compared to those in unaffected areas.

Mental Health

Displacement and financial loss from flooding amplify risks of depression, anxiety, and PTSD. Displaced individuals are up to 95% more likely to experience depression. Children, in particular, face cognitive impairments, academic challenges, and increased exposure to domestic and sexual violence post-disaster.

Inequitable Flood Impacts

Socioeconomic Disparities

Low-income populations face higher mortality and disease burdens during floods. Urban poor communities, such as those in Indonesia, endure respiratory infections and mental health challenges due to inadequate sanitation and healthcare. In the U.S., economically disadvantaged and minority communities in flood-prone areas experience higher rates of chronic illness, low birth weight, and mental health disorders, exacerbated by systemic disinvestment.

Gender Disparities

Men are at greater risk of physical harm due to occupational exposure, while women in low-income regions face caregiving burdens and resource limitations, heightening vulnerability to adverse outcomes.

Interventions to Reduce Health Impacts

Prevention Strategies

Structural measures like levees and improved drainage systems mitigate flood damage but often contribute to greenhouse gas emissions. Nature-based solutions—such as wetland restoration and green infrastructure—offer sustainable alternatives by reducing water flow and enhancing ecosystem health.

Preparedness and Public Awareness

Preparedness measures include public education, evacuation planning, and early warning systems. For example, during the 2019 Odisha floods, advanced warning systems enabled the evacuation of 1.5 million people. Health systems must bolster disaster-readiness by training staff, securing resources, and establishing resilient infrastructure.

Emergency Response and Recovery

Post-flood recovery efforts prioritize hygiene, mold remediation, and healthcare delivery through telemedicine. Vaccination campaigns and disease surveillance systems help prevent outbreaks. Coordinated efforts during the 2010 Pakistan floods, for instance, rescued 1.4 million people and conducted widespread health screenings.

Conclusions

Flooding, intensified by climate change, poses significant health risks ranging from fatalities and injuries to infectious diseases and mental health challenges. Vulnerable groups, including children, older adults, and low-income communities, face the greatest burdens. Addressing these inequities requires integrated prevention, preparedness, response, and recovery strategies. Investments in data collection, early warning systems, and research into long-term health impacts—especially in low- and middle-income countries—are critical for mitigating these growing threats.