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Written by Kathryn Foster, Cornell University
As sea-level rise worsens the impacts of hurricanes and storm surges, it also leads to more frequent tidal and seasonal floods in coastal areas, commonly referred to as sunny-day, blue sky, or nuisance flooding. The annual number of days with sunny-day flooding has more than doubled since 2000, with projections that it will triple by 2050, averaging 45-85 days a year nationwide (NOAA, 2025). Current research, such as Mueller et al. (2024), is beginning to document the many impacts of sunny-day flooding and other types of flooding on residential health.
Mortality: Research shows that in Florida, a 20-mm (0.79 in.) increase in tidal flooding depth raises mortality rates by 0.46% to 0.60% among adults 65 and older. Sea-level rise could contribute to an additional 130 elderly deaths annually in Florida relative to 2019 (Mueller et al. 2024).
Similarly, longer-lasting floods have greater impacts on mortality than other types of floods, such as flash floods (Lynch et al., 2025). An increase in frequency and severity of seasonal tidal flooding could increase the risk of mortality by blocking roads to medical services, such as regular doctor’s appointments, pharmacies, and hospitals. Other research supports these conclusions, finding that with anticipated intensified flooding, elderly populations will become more vulnerable to morbidity and mortality risks, largely due to mobility constraints among aging adults (Paavola, 2017; Hu et al., 2018; Sheahan et al., 2025). The mortality effects of flooding primarily affect those who require at least 8.85 minutes to reach the nearest hospital (Mueller et al. 2024).
Infectious Diseases: Seasonal tidal flooding may also increase the incidence of waterborne and infectious diseases in the United States. As flooding increases, communities are exposed to standing water around their homes for longer periods. Seasonal floods are strongly associated with increased hospitalizations for Legionnaire’s disease, a type of pneumonia caused by Legionella bacteria that grows in warm, moist climates (Lynch and Shaman 2022). Enteric infections may also arise from drinking water contamination and sewerage disruption (Carr et al., 2024; Wright et al., 2018), and mosquito-borne diseases and infections may occur from exposure to polluted flood waters (Wright et al., 2018).
Previous research on coastal storms finds that these events are associated with the spread of certain infectious diseases, such as E. Coli, Legionnaires’, Cryptosporidiosis, Paratyphoid fever, and Dengue in certain areas (Lynch and Shaman 2023; Zheng et al., 2017). These studies similarly posit that the spread of infectious disease will increase alongside predicted increases in coastal storms due to climate change. Although not yet explicitly studied, researchers hypothesize that the spread of infectious diseases associated with coastal storms will also be linked to seasonal tidal flooding (Lynch and Shaman 2022). This provides ground for future research to examine how increasing tidal floods relate to the rise in infectious diseases, like that of coastal storms.
Other Impacts: Furthermore, other hazards, such as snakebites and wound infections, may occur with tidal flooding and prolonged inundation of residential areas (Wright et al., 2018). Flooding increases residents’ exposure to venomous snakes, as snakes try to enter homes to find dry land or as water snakes are found in inundated streets, leading to a potential health hazard if bitten (Ochoa et al., 2018). Furthermore, as residents document having to walk through flooded streets during seasonal tidal flooding, wounds may become infected by the floodwater, or unseen hazards in the water may cause wounds (Wright et al., 2018). While these hazards are beginning to be documented, little research has examined their relationship to tidal flooding; future research could fill this gap by examining the association between reported snake bites and wound infections and tidal flooding.
From Research to Policy: These studies highlight that the costs of climate change go beyond heat impacts, emphasizing that the increased frequency and severity of seasonal tidal flooding may directly affect residents’ health. Mueller and colleagues (2024) suggest that communities design programs to improve transportation options for the elderly during the sunny-day flooding season. Furthermore, other researchers suggest that public health initiatives should inform clinicians and residents alike about the health risks of seasonal flooding (Lynch and Shaman, 2022). Alongside public-health initiatives, more effective and equitable preparations for flood risk should be put in place to better mitigate seasonal flooding-related health risks, especially for elderly adults in these communities (Lynch et al., 2025). Such initiatives could include increasing flood-risk awareness by hosting community classes on flood preparation, stockpiling essential medical supplies (Yodsubana and Nuntaboot, 2021), coordinating resource and information sharing with government agencies, healthcare providers, and community groups for elderly residents (Madani Hosseini et al., 2024), and constructing seawalls and elevating roads to prevent road closures (Mueller et al., 2024).
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