What are the human health consequences of flooding and the strategies to reduce them?

The issue

Floods are the most common natural disaster causing loss of life and economic damage in Europe, which experiences three types of floods: flash, riverine, and storm surges. Flash and riverine floods result from two main groups of meteorological events. In large- and medium-sized river basins in north and central Europe, flooding usually results either from wide-ranging and continuous precipitation or from snowmelt in connection with high antecedent soil saturation. The frequency of great floods increased during the twentieth century, underscoring the need for measures to prevent their negative health impacts.

Findings

The adverse human health consequences of flooding are complex, far-reaching and difficult to attribute to the flood event itself. There is very limited quantitative evidence of the health impacts of floods. The main health impacts are deaths, injuries and mental health illnesses during the flood event itself, during the restoration process, or from knock-on effects brought about by damage to major infrastructure including displacement of populations.

On average, the higher the water depth and the greater the flow velocity of a flood, the greater the damage to property. Most flood-related deaths can be attributed to rapid rise floods. Floods with fewer deaths and severe injuries were attributed to mild temperatures, government rescue plans, civilian rescue operations and disaster occurrence at times when most people were at home. Other health problems and injuries were reduced by measures taken by trained military personnel and by distribution of boots and gloves to other responders. Driving into flood waters is dangerous, as cars can become buoyant and swept away. The fatal effects of slow-rise river floods proved to be lower if people were aware of the risk of flooding and better prepared for a potential disaster. Sprains, strains, lacerations, abrasions and contusions are the most commonly reported injuries following floods. The risk of communicable disease outbreaks following flooding is small in industrialized countries (excluding tropical regions of industrialized countries like Australia) due to effective water treatment and sewage pumping, safe drinking-water, and public health infrastructure. However, national ministries and governments might need to take additional action on case-by-case bases.

Providing accurate information on safe management of flood water during evacuation and clean-up and on the actual situation is essential. Chronic health effects followed by flooding were explained by exposure to human and animal viruses during evacuation, or substantial psychological or physical stress at the time of flooding. Furthermore, flooding is associated with increased rates of anxiety and depression stemming from the experience itself, troubles brought about by geographic displacement, damage to the home or loss of familiar possessions and stress in dealing with builders and other repair people in the aftermath. The persistence of flood-related health effects is directly related to flood intensity. A comprehensive surveillance of morbidity from floods is limited, however. Hospitals, ambulances, retirement homes, schools and kindergarten in flood-prone are at risk, and evacuation of patients and vulnerable groups might represent a further risk.

Policy considerations

There is a need to shift emphasis from disaster response to risk management; to improve flood forecasting; to establish early warning systems, and to include health actors in the communication flow. Risk management in this area must cover a broad field, including health impact assessment of flood structural measures, regulations concerning building in flood prone areas, insurance policies, etc.

The harmful effects of flooding can be reduced by building codes, legislation to relocate structures away from flood-prone areas, planning appropriate land use and migration measures. The evidence, however, is inadequate concerning the effectiveness of comprehensive, risk-based emergency management programmes for reducing the adverse health effects of floods. The elderly, disabled, children, women, ethnic minorities and those on low incomes have been shown to be more vulnerable than others to the effects of flooding and may need special consideration during the response and recovery periods. However, more good-quality epidemiological data on these issues is still needed.

The views expressed in this summary are based on a publication of a HEN Network member agency and do not necessarily represent the decisions or stated policy of WHO/Europe.

Sources

Hajat S, et al. The human health consequences of flooding in Europe and the implications for public health: a review of the evidence. Applied Environmental Science and Public Health, 2003, 1(1):13-21. (http://www.openmindjournals.com/EnvSci1-1-Hajat.pdf. Accessed 10 December 2004)