This is how flooding can impact our health
Flooding is devastating in every aspect: from property and infrastructure damage to loss of life and wider health impacts. As floods become increasingly common for more people in a warming world, we look at the effects on human health.
Dadu district, Sindh province, Pakistan
People in a flooded Pakistani village scramble for food rations as they battle the downwash from an army helicopter delivering aid. These unprecedented floods affected approximately 20 million people and destroyed homes, crops and infrastructure, leaving millions vulnerable to malnutrition and waterborne disease such as cholera. Estimates of the total number of people killed range from 1,200 to 2,200, while an estimated 14 million people were left homeless.
The Pakistan floods of 2010 were the result of record monsoon rainfall. As our planet continues to change in ways that are unprecedented in human history, the direct threat to health becomes increasingly urgent. We need to better understand how different populations are affected by climate change so that we can take the necessary actions to protect human health.
Credit:
Daniel Berehulak, Getty Images / Wellcome Photography Prize 2019
Licence: Attribution, Non-Commercial, No Derivative Works CC BY-NC-ND
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Summary
What are the health effects of floods?
- Climate change makes extreme weather events more common, and more people are likely to experience flooding.
- Diseases, mental health problems and undernutrition or malnutrition are some of the health effects of flooding.
Flooding is the most common natural disaster globally, affecting more than two billion people worldwide between 1998 and 2017 and with 44% of disasters worldwide associated with it.
As climate change makes the world increasingly susceptible to extreme weather events, more people are likely to experience flooding and its devastation, including its serious impacts on our health.
The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report published in March 2022 highlighted that climate hazards such as flooding are “increasingly contributing to a growing number of adverse health outcomes”.
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In this explainer video, we uncover some of the many physical and mental health risks of flooding — joined by Professor Collins Iwuji and Associate Professor Catherine Butler.
Narrator: Floods have been making headlines lately. Bangladesh. The U.S. Italy. Libya. People across the world have experienced some of the worst events on record. And with global warming changing weather patterns, flooding will just become more and more likely.
When floods strike, we're used to seeing the immediate aftermath: destroyed buildings, streets underwater, and death tolls. But what you don't often see is the huge impact on people’s health that lasts far beyond the event itself.
These are the unexpected health threats of flooding.
When you think about floods, especially if you’ve never been affected by them, it's easy to think of health risks like drowning or hypothermia. And of course, that's not wrong. Though the reality for people hit by flooding is much wider ranging and can continue for months, or even years, once the water clears.
This was the case for Pakistan. In 2022, record-breaking floods submerged a third of the country. Soon after, the number of malaria cases quadrupled to at least 1.6 million — the highest in over 30 years. And it wasn't just malaria. Cases of dengue, typhoid, and skin infections surged, to name a few. Outbreaks like these are incredibly common after a flood.
Take Bangladesh. In 2023, excessive rainfall combined with high temperatures and high humidity contributed to the country's most severe outbreak of dengue on record.
The same year, in the Philippines, leptospirosis cases jumped due to increasing floodwater.
And Libya’s floods during Storm Daniel caused a spread of diarrhoea which had the potential to spark a second devastating crisis.
But why does flooding cause a surge in these types of diseases?
Well — periods of intense rainfall and floods can lead to a buildup of water. From small spots, like people's rooftops and water storage containers, to large pools of it, especially where outdoor drainage isn't effective.
This water is a perfect hatching ground for the mosquitoes that carry diseases like dengue and malaria.
As the flooding intensifies, it can also infiltrate and damage sanitation facilities, causing sewage systems to overflow, contaminating people's homes and water supplies. This can then spread waterborne diseases like cholera and hepatitis A.
Floods are, by their nature, highly destructive. Whilst they make epidemics more likely, they can also disrupt an entire country's health infrastructure — reversing years of disease control.
Collin Iwuiji: Damage to businesses and loss of income could also result in some people prioritising their livelihood sustenance over their healthcare.
Narrator: That was Professor Collins Iwuiji, from the Africa Health Research Institute.
Collin Iwuiji: Damage to residential homes and forced displacement can result in them being housed in temporary shelters which are often overcrowded. And because of this overcrowding, there's loss of privacy and no confidentiality. So people suffering chronic diseases like HIV might be reluctant to disclose their status to healthcare providers due to stigma.
Narrator: And it extends beyond infectious disease. Access to ongoing medication, surgery, birth control, and period care, are all interrupted by large flooding disasters.
So what about impacts beyond the physical? If we go back to Pakistan, where recent flooding caused a surge in malaria cases, another health crisis was underway... a crisis in mental health.
With locals of all ages distressed by the floods — the loss of life, land, livelihood — there just wasn't the right support readily available.
When people live through a flooding disaster, chances are, they witness some potentially traumatic events. This can lead to high levels of psychological distress. Some might even develop mental health problems like post-traumatic stress disorder, depression, or substance use disorders.
We asked Catherine Butler, Associate Professor at the University of Exeter, for one reason why this might be happening.
Catherine Butler: Evacuation, displacement – so people having to move out of their homes to other areas – can break up communities and really destroy the support networks that might otherwise reduce the mental health impact of the flood.
Narrator: And it's not just the direct impact of floods. Unemployment, food and water insecurity, or homelessness following the disaster can also affect mental health.
Catherine Butler: There's also a mental health burden associated with the people that are responding to the floods; that are involved in the response process. Certainly, in our research in the UK, it was evident that the people that had been first responders in a lot of instances of flooding had experiences mental health issues as well.
Narrator: This meta-analysis reviewed 23 different studies on the mental health impact of floods around the world. Although rates did vary a lot between events, and decreased over time, it found that almost 3 in every 10 flood survivors experienced post-traumatic stress disorder.
The thing is, individuals, families, and communities often show high levels of resilience in the face of extreme weather events.
According to a 2010 study, most people fully recover or maintain good mental health if they can access the right support. But with escalating and more frequent flooding disasters, we don't know if this sort of resilience can last in the long-term.
So — climate change is making flooding events more likely and more extreme. Both the physical and mental health impacts are going to grow. We urgently need more research and policy action to bring in adaptations at scale, helping communities adapt to floods.
For example, we can protect more natural floodplains, rivers, and coastlines to manage flood risk. We can build flood defences and we can roll out accurate flood forecasts which help teams to prepare, reducing the damage.
Collin Iwuiji: During the time of a disaster or a flood is not the time to start putting people together to respond. It should not be a reactionary thing. This should be, like, teams that are already existing. They are trained, they know what to do when there is a flood event or any other extreme weather event.
Narrator: Though, to put it bluntly, these adaptations won't be enough. We urgently need our governments to support the transition away from fossil fuels, if we want to prevent climate change from getting any worse. And limit the disasters in the first place.
Collin Iwuiji: I think we need long term studies on both the physical and mental health outcomes. Especially amongst vulnerable individuals like children, the elderly, pregnant women, people with disabilities. But we need data prior, during and after the floods.
Narrator: There is hope, that if we do all this, we may be able to minimise those exposed to floods. But as recent events have shown, we can't wait around. We need action now.
What are the health effects of flooding?
The health impacts of disasters like flooding are complex and cascading, and can impact any one person or population simultaneously.
The kinds of health risks any given community might experience, the severity of them, and just how vulnerable they might be can differ depending on various factors. Geography, population size and density as well as levels of preparedness and resilience are part of it. The flood’s characteristics also play into this, whether it’s flash floods, coastal floods, riverine floods, or permanent floods for low-lying areas.
Floods can directly and indirectly affect human health in both the short and long term. Additionally, it’s not just communities who have experienced flooding whose health is at risk. Disaster responders, healthcare professionals and critical service providers can also be affected.
Drowning is often top of mind when it comes to health risks of flooding. But the risks can range from injuries, hypothermia and animal bites to infectious diseases, undernutrition and mental health problems.
When disasters like floods strike, there is a lot of focus on economic impact and property damage, as well as human casualties. But these also overlap with health concerns in many ways.
Flooding can strain health services due to damaged infrastructure, loss of health professionals and access to medicine, which could delay care or treatment for those who need it.
The economic fallout or loss of possessions and livelihoods due to a flooding disaster can result in financial uncertainty that may affect mental health, to say nothing of the grief from losing loved ones.
Below is an overview of common flooding related health impacts.
Diseases
Diseases and outbreaks are another major health concern in the event of flooding.
These can come in the form of waterborne diseases, which are those that come from drinking or coming into contact with contaminated water. These can include diarrhoea, cholera, typhoid fever and leptospirosis.
It can also sometimes be vector-borne diseases, which come from an intermediate species carrying the disease pathogen like a mosquito. Vector-borne diseases that come about from flooding include dengue fever and malaria.
Lagos, Nigeria, 2019.
A mother carries her children to school through a flooded street.
Credit:
Nyancho NwaNri / Wellcome Photography Prize 2020
Licence: All Rights Reserved
Flooding increases the risk of these diseases and potential outbreaks in populations because it can cause sewage overflow as well as damage to water supply and sanitation facilities. Contamination of drinking water can lead to typhoid fever, cholera and hepatitis A.
In areas at risk of coastal flooding, there’s also the possibility of salt-water intrusion to drinking water as well as hypertension and eclampsia.
Once floodwaters have receded, stagnant water left behind in gardens, parts of the home or even farming lands can become a breeding ground for mosquitoes and lead to diseases like dengue or malaria.
Bangladesh had its worst dengue outbreak in 2019, with over 100,000 cases and 179 deaths. The outbreak was attributed to flooding in that year’s monsoon season.
Additionally, displacement and eventual overcrowding in evacuation centres can bring about other issues such as pulmonary and systemic fungal infections from moulds. According to the European Climate and Health Observatory, people that have evacuated to temporary shelters are more likely to be exposed to infectious diseases and pathogens, so are “more prone” to health problems.
Injuries can also potentially lead to infections or diseases such as leptospirosis, a disease that spreads through water contaminated with rodent urine coming into contact with the skin.
In the Philippines – the third most vulnerable country to natural hazards and among the most at risk from climate change – there have been increases in leptospirosis, typhoid fever and dengue after heavy rainfall and flooding.
Mental health problems
Mental health problems, which can occur later, are often overlooked and not as well studied relative to the immediate health impacts caused by flooding. So far, it is known that the experience of surviving a flooding disaster can impact people after the event and sometimes for many years down the line.
Anxiety, depression, post-traumatic stress disorder or PTSD, psychosis and insomnia are some of the common mental health problems that come up in the aftermath of a flooding disaster.
In the UK, flood victims were between 4 to 8.7 times at risk of long-term mental health problems compared to people who did not experience flooding. In one case, rain became a trigger for a woman's PTSD after experiencing flooding in 2000.
The process of clean-up, recovery and rebuilding can be a source of stress, more so if they are not managed well by both government and the private sector.
Lagos, Nigeria, 2019
The flooding in this home forced the owners to vacate it, leaving behind their belongings.
Credit:
Nyancho NwaNri / Wellcome Photography Prize 2020
Licence: All Rights Reserved
Disruptions to basic facilities and supplies such as electricity, water and food can likewise be distressing and impact mental health, especially when these are prolonged.
In July 2021, heavy rainfall contributed to some of the worst flooding Western Europe has seen in decades, with over 200 casualties and billions of euros worth of damage. The World Health Organization issued public health advice on the long-term health impacts stemming from disrupted access to essential services and slow recovery. The Center for Disaster Philanthropy then highlighted mental health as a top priority for those affected.
Undernutrition or malnutrition
Though rarely considered, despite evidence for it, undernutrition or malnutrition is another health impact that can result from flooding disasters. Victims have been known to eat less during or after flooding, and often lose access to regular food supplies.
Food systems such as agriculture can also be significantly disrupted because of flooding. This can affect both the quantity and quality of food available and lead to food insecurity and undernutrition.
In parts of South Sudan, flooding due to years of historic rains led to the displacement of hundreds of thousands of people with many resorting to eating wild food such as water lilies owing to the loss of crops and livestock as food sources. Around 7.7 million people were estimated to be at risk of severe food insecurity.
Adapting to the future
Climate change is already exacerbating flooding as warmer temperatures can increase precipitation and cause extreme weather events.
Around 86 million more people have become exposed to flooding from 2000 to 2015. And 1.81 billion people are estimated to already face significant flood risk.
What can we do?
Learning to adapt will be crucial to deal with the health impacts of flooding, alongside mitigation efforts such as reducing emissions.
In Europe alone it’s estimated that without preventive measures up to 2.2 million people will be exposed to coastal flooding by 2100. That number goes down to 1.4 million people with moderate mitigation measures but without adaptation, and as low as 0.6 million if adaptation is factored in.
The health impacts of flooding can only get worse if the world does not take decisive and swift action on climate change.
We’re funding vital research into the impact climate change has on human health around the world, at national, regional and global levels. Explore our current funding call:
Climate and Mental Health Award: Uncovering mechanisms between heat and mental health
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