Key points

• Floods are the most common and deadly natural disaster with about 150 to 200 occurring globally each year, causing around $40 billion worth of damage
• The World Health Organization estimates that an average of around 5,000 people a year are killed in floods
• Climate change has led to an increase in frequency and intensity of flooding
• 75 per cent of deaths from flooding are due to drowning but other threats include a rise in water – and vector-borne diseases, injuries from evacuation and disaster clean up, and contamination of food supplies

Overview

There are three types of flooding: coastal, fluvial (rivers) and groundwater. Coastal flooding is caused by high tides, low pressure weather systems and surge conditions caused by strong winds. As sea levels rise due to climate change the risk of flooding will increase.

Rivers burst their banks after periods of intense rainfall, leading to damage to the local environment, properties and essential services.

Surface water flooding occurs when rainfall overwhelms drainage systems and surface water sewers, with water flowing over land. This is hard to predict and can happen quickly after a period of intense rainfall. Urban and rural areas may be affected and further disruption could come in the form of sinkholes or landslides.

Climate change is partly to blame for an increased likelihood of floods, alongside changes in land use and growth in the number of people living in flood prone areas. A 2021 analysis in the journal Nature found that between 2000 and 2018 the number of people living in flood-prone areas around the world increased by just over 30 per cent.

In Europe, floods are the most common natural disaster with around a 10th of people across the continent living in at-risk areas. The British Isles and central Europe are thought to be most at risk. In July 2021 severe floods killed 243 people, including 196 in Germany and 39 in Belgium.

Health impacts

The World Health Organization estimates that an average of around 5,000 people a year globally are killed in floods. Around three quarters of deaths from floods are due to drowning but there can also be a range of other dangers. Research in the BMJ in 2023 found that deaths from all causes – not just those directly related to flooding – rose in the 25 days after the disaster and did not return to normal until after about two months.

Direct health impacts from flooding include:

• Vector-borne diseases such as malaria and dengue fever, due to large quantities of standing water providing a breeding ground for mosquitoes
• Outbreaks of water-borne diseases such as cholera or typhoid if sanitation systems are damaged
• Injuries, such as lacerations or punctures from evacuations and disaster clean-up
• Chemical hazards – burns from fires or exposure to corrosive chemicals, poisoning, respiratory tract injuries from inhalation of irritant gases
• Gastro-intestinal illnesses from contaminated food
• Psychological harm associated with emergency situations
• Disrupted health systems, facilities and services, leaving communities without access to health care

Useful links

who.int/health-topics/floods

wmo.int/topics/floods

gov.uk/national-flood-risk-register

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