Floods

The Intergovernmental Panel on Climate Change defines floods as “the overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas that are not normally submerged. Floods include river (fluvial) floods, flash floods, urban floods, pluvial floods, sewer floods, coastal floods, and glacial lake outburst floods”. Flash floods account for approximately 85% of the flooding cases worldwide and also have the highest mortality rate (defined as the number of deaths per number of people affected). Floods are among the world’s deadliest disasters with more than 5000 lives lost annually. This is a consequence of the increasing frequency of heavy precipitation, changes in upstream land-use and a continuously increasing concentration of population and assets in flood-prone areas. This is often exacerbated by inadequate flood planning and management practices. Sea-level rise has increased vulnerability to storm surges and related coastal flooding.

Floods are the most common form of natural disaster in the European Region, which has experienced in recent years some of the largest flooding events in its history. A 10th of the urban population in the European Region is currently living in areas potentially at risk of flooding. Moreover, climate change is projected to result in more frequent and more intense heavy precipitation events, making them 9 times more likely to occur. This will likely increase the frequency and intensity of floods of various types such flash floods, coastal and river floods, and snowmelt floods. Without appropriate adaptation, river flooding is projected to affect 250 000–400 000 additional people per year in the European Region by the 2080s, more than doubling the numbers from 1961–1990. The populations most severely affected will be those of central Europe and the British Isles. Rises in sea-level and coastal storm surges will affect several million more people, in particular in northern and western Europe, by 2080.

Floods can affect both physical and mental well-being. Beyond the widespread nature of the phenomenon, the effects of flooding on health are diverse and significant, ranging from mortality and injuries resulting from trauma and drowning, to infectious diseases and mental health problems (acute and long term). In the last 50 years, some of the deadliest floods in the European Region with more than 200 casualties have been the 2024 floods in the Valencia region of Spain, the 2021 floods in central and western Europe, and the 1970 floods in Romania. Flooding has occurred in 50 of the 53 countries of the WHO European Region during the past 2 decades. This have caused more than 2000 deaths, other health effects, property losses, damage to health facilities, displacement and enormous economic costs, with the most severe taking place in Germany, Romania, the Russian Federation, Spain, Türkiye, the western Balkans and the United Kingdom.

Populations that are particularly vulnerable to adverse effects of flooding include the elderly, children, people with chronic illnesses or physical impairments and pregnant women. People accommodated in temporary shelters are more prone to acquire health problems due to the higher probability of exposure to infectious disease pathogens in communal accommodations and the disruption of their regular health-care provision.

Flooding increases the risk of:

• heart attacks and respiratory problems
• infectious disease, particularly in children
• waterborne diseases due to contact with contaminated flood water, debris and mud
• mosquito-borne diseases as the stagnant water may create suitable sites for mosquito breeding.

Up to 75% of people affected by flooding suffer from mental health problems: trauma, mental distress in the short term potentially leading to longer-term posttraumatic stress disorder, anxiety, insomnia, psychosis and depression.

The magnitude of the physical and human health cost of floods can be reduced if adequate emergency preparedness and planning are implemented, mitigation actions are undertaken, and timely and coordinated responses are launched through and after the event. Resilient and proactive health systems that anticipate needs and challenges are more likely to respond effectively during emergencies, saving lives and alleviating human suffering. WHO/Europe is mandated to support Member States in their efforts to achieve health security and minimize health impacts of disasters, including floods.

The WHO/Europe publication “Flooding: managing health risks in the WHO European Region” proposes a range of measures to protect public health, organized around prevention, preparedness, response and recovery. Experiences in the Region indicate a need to shift the emphasis from disaster response to long-term risk management. The approach should include health impact assessments of structural measures to combat flooding, specific building regulations in flood-prone areas and insurance policies. Approaches to manage the health risks of floods should be based on the common policies, plans and measures for all types of hazards, before addressing the specific issues associated with floods.

A number of information sheets on public health advice for health authorities, health professionals, local authorities and emergency managers on preparedness and response for flood events are also provided within the publication.