After the Storm: The Hidden Health Risks of Flooding in a Warming World

Report Looks at Five Major Health Threats From Flooding in a Warming World

A Union of Concerned Scientists news release

WASHINGTON (March 15, 2012)—Extreme precipitation and flooding, likely on the rise in a warming world, carry significant and often hidden health risks, according to a report, “After the Storm: The Hidden Health Risks of Flooding in a Warming World,” released today by the Union of Concerned Scientists (UCS).

“Damage from floods is typically measured in terms of lives lost and the cost of damage to buildings and infrastructure,” said Liz Perera, UCS public health analyst and one of the report’s co-authors.  “But what are often overlooked are the potentially costly public health impacts.”

The report calls attention to these impacts by listing the top five health risks of extreme precipitation and flooding:

  1. Drowning while driving: Almost half of 2010 flood fatalities involved people who drowned while attempting to drive through floodwaters. Only 18 inches of water can lift a car or SUV; once buoyant, the water will easily push the vehicle sideway. Most vehicles then tend to roll over, trapping those inside.
  2. Waterborne diseases contaminating drinking water: Extreme precipitation and flooding can sometimes overwhelm drinking water infrastructure and wells, which reduces or prevents water purification. Over half of all waterborne disease outbreaks in the United States occur in the aftermath of heavy rain.
  3. Sewage back-up in plumbing or basements: Flooding can cause local sewage lines and septic tanks to overflow, sometimes resulting in sewage backing up into people’s residences.
  4. Bacteria, sewage, and other contaminants in waterways: During flooding, untreated sewage, pesticides, and street contaminants (motor oil, dog excrement, etc.) can flow into local rivers, lakes, ponds, and even ocean beaches.
  5. Mold and dangerous indoor air quality: Water intrusion anywhere in a building can cause toxic mold to grow in ceilings, walls, or insulation.

Over half of all outbreaks of waterborne diseases in the U.S. occur in the aftermath of heavy rains,” said Perera.  “Health risks will likely increase as extreme rainfall events are projected to become more common in a warming world.”

Heavy rains can contaminate drinking and recreational water with sewage, petroleum products, pesticides, herbicides, and waste from farm animals, wildlife and pets. Floodwaters may contain more than 100 types of disease-causing bacteria, viruses and parasites.

“We think of waterborne illnesses as a problem in developing countries, but it’s a very real public health issue here in the U.S.,” said Dr. Marc Gorelick, division chief of pediatric emergency room medicine at Children’s Hospital of Wisconsin, in Milwaukee. “Climate change, because it likely causes heavier storms, could threaten our already vulnerable water supply and lead to more cases of gastrointestinal illness.”

Gorelick conducted a study which found that between 2002 and 2007, there was an 11 percent increase in gastrointestinal cases at Children’s Hospital within four days of heavy rains.

The UCS report also points out that flooded homes and buildings create a breeding ground for mold, which can cause debilitating respiratory and neurological problems. Mental health problems also tend to increase in the wake of extreme weather disasters.  These health problems can persist long after flood waters have receded.

Extreme weather events, such as heavy rains, are also creating challenges for waste water and water treatment plants.

“Like many older cities, heavy precipitation can put a strain on New York City’s infrastructure,” said Angela Licata, deputy commissioner for sustainability at the New York City Department of Environmental Protection. “We are continually innovating to meet that challenge, while maintaining and improving essential services.”

Other factors that affect flooding risks include where people live, how land is developed and the investments made in building resilience.

— Union of Concerned Scientists

11 Responses to After the Storm: The Hidden Health Risks of Flooding in a Warming World

  1. Paul Magnus says:

    There a mental health aspect also from the strain and displacement (often for extended periods) of individuals. Especially when events start to repeat.

  2. John McCormick says:

    i.e, Pakistan

  3. Mike Roddy says:

    The wood from houses has to go to a landfill after a flood, even if the house was built recently. There is just too much rot and mold.

    This is one more reason why all of our homes should be built with durable and inert materials. A concrete house survives floods, and a steel building’s elements can be recycled if they are water damaged.

  4. Be Green says:

    Drowning while driving? I never would have expected to see that on the list.

  5. John Tucker says:

    I hadn’t seen the Gorelick study, its very interesting:

    Association between Rainfall and Pediatric Emergency Department Visits for Acute Gastrointestinal Illness ( )

    Good list too.

    I believe also that after a contamination event normal chlorinations role as disinfectant possibly could be compromised in low concentration situations or stagnant reservoirs as well as in the water sources of people that depend on home well water systems (not to mention when combined with rising temperatures, high temperature events and pathogen resistance) – for a scary example Naegleria fowleri:

    Identification of Naegleria fowleri in Domestic Water Sources by Nested PCR
    ( )

    Newly Identified Tap Water Sources of Pathogenic Amoeba ( )

  6. Kate Cell says:

    Hi Paul,

    Thank you for raising this issue. Our report does discuss the mental health aspects, which are very important; some studies suggest that they are among the most costly impacts of flooding.

    Kate Cell
    Union of Concerned Scientists

  7. Merrelyn Emery says:

    Yes, particularly when they have not only lost their homes but also their farms or businesses and have no prospct of a livelihood for another year as is happening here – spuds, grapes etc rotting for the second year in a row, ME

  8. Rabid Doomsayer says:

    Read the whole document

    The whole paper presents a darker picture than the summary.

  9. Doug Bostrom says:

    Sewage back-up in plumbing or basements: Flooding can cause local sewage lines and septic tanks to overflow, sometimes resulting in sewage backing up into people’s residences.

    Ah, yes, near and dear to my own heart. We had an eruption of dubious “fountains” in the downstairs of our house, when local lift pumps for the county sewage system were overwhelmed by extreme rainfall which drove local rivers to historical record highs.

  10. Lou Grinzo says:

    I can attest to the physical and mental impacts of being a flood victim. I was a teenager (just barely) living in Wilkes-Barre, PA, when the Agnes flood hit and created a mess like most people can’t even imagine.

    We had deep water over a broad area, with all the property damage that implies, but we also had an effect that’s not often talked about: The wave of water that rushes through normally dry areas when dikes fail. On the west side of the river, in a little town named Forty Fort, when the dikes failed a cemetery was gutted, with caskets and bodies strewn over miles of flooded residential area. On the east side, the failed dikes resulted in numerous houses being blown right off their foundations. Months later you could walk through these neighborhoods, just blocks from where I lived at the time, without a single house standing, and look into the open basements and see furnaces, water heaters, bicycles, ice skates, etc.

    There are two groups of people in this world: Those with a deep fear of floods and those who haven’t lived through one.

  11. Hot Rod says:

    Number 1 danger listed is driving, as in
    Drowning While Driving
    Where It Comes From: Of the people killed in U.S. floods in 2010, 44 percent died in vehicles (NOAA 2010). Strong rains or rapid snowmelt can bring fastmoving water that is very unpredictable, and people make the poor decision to drive down a flooded road
    either because the vehicle in front of them makes it or because they think the water doesn’t look too deep.
    Only 18 inches of water can lift your car or SUV; once buoyant, the water will easily push the vehicle sideways. Most vehicles will then tend to roll over, trapping
    those inside and washing them downstream
    (NOAA 2012).

    any idea how many people this was? not stated in the document. Am I alone in thinking that if this is the number 1 danger I shouldn’t be too worried?