The health impact of climate-driven floods

Escalating floods linked to climate change are amplifying health inequities—explore how innovative solutions can protect the world’s most vulnerable communities.

Special Report: Share on Climate Change, Floods, and Human Health. Image Credit: nutt / Shutterstock

In a recent special report published in The New England Journal of Medicine, an international team of researchers examined the increasing health impacts of flood exposure driven by climate change, with a focus on injuries, diseases, mental health harms, and vulnerabilities in at-risk populations.

Background

Flooding, the most common climate hazard, has significantly increased in frequency and magnitude due to climate change, affecting over 1.65 billion people globally from 2000 to 2019. Altered precipitation patterns, soil moisture, and cryosphere changes drive these shifts, with projections indicating a dramatic rise in flood exposure and risk in vulnerable regions. For example, under high greenhouse gas emission scenarios, annual flood exposure is projected to increase by a factor of approximately 14 by 2071–2100, with 97.6 million people at risk of experiencing a 20-year flood annually. Health impacts of floods include immediate fatalities, injuries, waterborne and vector-borne diseases, mental health issues, and disruptions in healthcare access. Vulnerable populations, including children, older adults, and low-income communities, are disproportionately affected. Further research is essential to address knowledge gaps in long-term health consequences and strategies.

Health risks associated with floods

Mortality due to floods

Floods result in direct fatalities from drowning, hypothermia, electrocution, and explosions, often caused by rapid water flows or damaged infrastructure. Additionally, secondary deaths occur from exacerbated chronic illnesses, waterborne diseases, and mental health conditions. For instance, a multi-country study reported a 2.1% increase in overall mortality within two months of flood events attributed to disrupted healthcare, poor sanitation, and psychological stress.

Injuries and environmental hazards

Nonfatal injuries, including cuts, fractures, and trauma from debris, are common during floods. Moreover, floods can mobilize hazardous chemicals, as seen during Hurricane Florence, where toxic coal ash contaminated ecosystems. In addition, carbon monoxide poisoning is a significant risk in disaster-affected areas due to improper use of fuel-burning devices like generators.

Spread of Infectious Diseases

Floodwaters are fertile grounds for waterborne diseases like leptospirosis and hepatitis. Overcrowded shelters further elevate respiratory infections, while stagnant water encourages mosquito breeding, increasing malaria and dengue risks. For instance, stagnant floodwaters can raise mosquito biting activity and density, exacerbating outbreaks of mosquito-borne diseases. Additionally, contaminated water supplies heighten gastrointestinal illnesses.

Impact on noncommunicable diseases

Floods disrupt healthcare services, leading to untreated conditions like hypertension and diabetes. A study of U.S. veterans affected by Hurricane Sandy found a 26% rise in uncontrolled hypertension one year after healthcare facilities were disrupted. Cognitive decline and cardiovascular risks increase in vulnerable populations due to healthcare inaccessibility.

Vulnerabilities in specific populations

Pregnant women and children

Pregnant women exposed to floods face heightened risks of gestational complications and pregnancy loss due to stress and infections like hepatitis E. Children, particularly in low-income regions, suffer from undernutrition, with repeated flooding linked to severe wasting, as reported in rural India. Contributing factors include diarrhea, food insecurity, and inadequate care post-disaster. For example, children in repeatedly flooded Indian communities were 3.37 times more likely to suffer from severe wasting compared to those in non-flooded areas.

Mental health consequences

Flood-related displacement and financial loss significantly increase the risks of depression, anxiety, and Post-Traumatic Stress Disorder (PTSD). Displaced persons are up to 95% more likely to experience depression and 70% more likely to develop PTSD. Vulnerable groups, such as displaced individuals and those with prior trauma, are especially affected. Children experience cognitive impairments, poor academic performance, and heightened exposure to domestic and sexual violence post-flooding.

Inequitable Impacts of Flooding

Socioeconomic disparities

Flood-related mortality is inversely correlated with national income levels. Poor urban populations, such as those in Indonesia, suffer disproportionately from respiratory infections and depression due to inadequate sanitation and healthcare. In high-income countries like the United States (U.S.), economically disadvantaged and minority communities residing in flood-prone areas experience higher rates of cardiovascular disease, low birth weight, and mental health disorders. Racial disparities further exacerbate these risks, as communities of color in flood-prone U.S. areas often face systematic disinvestment in housing, healthcare, and education.

Gender disparities

Men face greater physical exposure to flood risks due to occupational and risk-taking behaviors, while women in low-income regions endure caregiving burdens and resource limitations, increasing their vulnerability to adverse outcomes.

Interventions to reduce health impacts

Prevention strategies

Structural measures like levees, dams, and improved drainage systems help mitigate flood impacts. However, these solutions often contribute to greenhouse gas emissions. Prioritizing low-emission alternatives, such as sourcing local materials and using nature-based solutions like restoring wetlands, is crucial. Nature-based approaches, such as restoring wetlands and implementing green infrastructure, offer sustainable alternatives by reducing water flow and promoting ecosystem health.

Preparedness and public awareness

Effective preparedness includes public education on flood risks, evacuation planning, and robust early warning systems. The Common Alerting Protocol enhances communication, ensuring timely warnings via multiple channels. During the 2019 Odisha floods, such early warning systems facilitated the evacuation of over 1.5 million people, prioritizing vulnerable groups like older adults and children. Health systems must secure resources, train staff, and implement disaster-ready infrastructure.

Emergency response and recovery

Post-flood recovery prioritizes hygiene and sanitation through Water, Sanitation, and Hygiene (WASH) kits and mold remediation. Telemedicine bridges healthcare gaps, offering remote care for injuries and chronic conditions. Vaccination campaigns and surveillance systems prevent outbreaks, as demonstrated in New Zealand, where genotyping traced a waterborne disease to contaminated runoff. In the 2010 Pakistan floods, coordinated humanitarian efforts rescued 1.4 million people and conducted large-scale health screenings.

Conclusions

To summarize, the study concludes that flooding, aggravated by climate change, poses significant short- and long-term health risks, including fatalities, injuries, infectious diseases, and mental health challenges. Vulnerable populations, such as children, the elderly, and economically disadvantaged groups, bear the brunt of these impacts, highlighting inequities in health outcomes. Effective management requires a comprehensive approach combining prevention, preparedness, response, and recovery. Structural and nature-based solutions, enhanced healthcare resilience, and public awareness programs are critical. Addressing these challenges demands robust data collection, improved early warning systems, and targeted research into long-term impacts, especially in low- and middle-income countries.