We’re Only Seeing the Beginning of the Texas Floods’ Deadly Toll

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July has been the month of the flash flood. The floods in Texas were particularly devastating: more than 130 deaths, 101 people still missing, and an estimated $18 billion to $22 billion in damage. Those were followed by floods in North Carolina, New Mexico, Chicago, and New York. More are forecast for the coming week, including in areas already hard-hit.

Even in places where the floods have let up, the storm isn’t over: Floods can lead to excess deaths long after the actual event. “The health impacts of flooding aren’t just immediate,” wrote Katelyn Jetelina last week in her newsletter, Your Local Epidemiologist. “They often unfold over weeks and months.”

Indeed, a recent study found that between 2000 and 2020 across the U.S., there were an estimated 22,000 additional deaths attributable to flooding. For reference, the National Weather Service estimates that there are around 127 deaths per year from flooding—that adds up to a little more than 2,500 direct deaths during that 20-year period. These 22,000 excess deaths, on the other hand, were caused by heart attacks, strokes, respiratory disease, and infectious diseases as much as a year out from the actual flood event. Another global study that looked at floods in 761 communities across 35 countries also found increased mortality risks, including cardiovascular and respiratory mortality, in the two months after the flooding event.

Floods—like other natural disasters—cause emotional stress for people who have been displaced or lost loved ones, and that stress can take a physical toll. Then there’s the fact that flooding can lead to mold growth in homes, which leads to increased risks for all sorts of things, including respiratory diseases and neurological disorders. Infectious diseases can spread after a flood if overwhelmed sewage systems contaminate local bodies of water. And people who have been displaced due to a natural disaster may lose access to necessary medications and health care. (Somewhat oddly, floods were associated with a decrease in deaths related to dementia and hypertensive diseases, possibly due to fewer diagnoses in the wake of a disrupted health care system or hastened death by another cause.)

Older populations tend to be more vulnerable to these delayed impacts, as well as people with lower income or in less developed areas. In the 2000–2020 study, the causes varied by racial background: While white people represented the largest percentage of lives lost overall, Black and Hispanic people were more affected by external causes, such as lack of access to health care as a result of the flood.

These insidious side effects linger and lurk, and it’s thanks to studies that look at long-term associations that they don’t go entirely uncounted. But those studies all share another takeaway: There need to be more of these studies. As a review of cardiovascular impacts following extreme storms noted, while “a growing body of evidence suggests that victims of hurricanes have increased incidence of cardiovascular disease,” there’s a “lack of rigorous long-term evaluation of hurricane exposure,” and an absence of exploration into the mechanisms that might lead to worsened cardiovascular outcomes.

In other words, a flood’s death toll extends long past when we usually stop counting. As flooding and other natural disasters get worse due to climate change, the lives lost will eventually feel incalculable.