Future challenges for water hazard early warning systems

Researchers have reviewed early warning systems (EWS) for water hazards, such as flash flooding, landslides, river flooding and coastal flooding. They conclude that EWS continue to provide valuable information to allow emergency services and local communities prepare for water-related natural hazards. However, there are a number of challenges to address to gain the most benefit from EWS.

Climate change is likely to increase the number of extreme weather events, which in turn will increase the number of natural disasters affecting people in Europe. The EU Floods Directive¹ and the UN’s Hyogo Framework for Action² are two key policies designed to help protect communities at risk and endorse EWS as an important component of risk reduction strategies.

The researchers, working under the EU KULTURisk project³, reviewed EWS for flash flooding and surface water flooding, landslides, river flooding and coastal flooding, focusing on European examples. They identified the similarities between the many different systems used for different hazards and the challenges they face in future.

Many EWS rely on numerical weather predictions (NWP), as these cover large areas and can simulate future weather conditions. However, NWP do have some limitations that need to be considered in EWS design: surface water flooding, landslides and flash floods are caused by extreme rainfall peaks in a local area, which are often on too small a scale to be picked up by NWP. Although ‘ensemble weather’ forecasting, whereby risks for river floods and storm surges are quantified and predicted, can give a better understanding of such uncertainty.

Flood and storm surge EWS are increasingly relying on ensemble weather predictions instead, which can help estimate the uncertainty of prediction, essential for longer lead times. These are made up of a number of NWP and simulate sets of possible future weather evolutions. Examples of EWS successfully using ensemble forecasting include the Netherlands’ Storm Surge Warning Service and the Environment Agency of England and Wales’s coastal storm surge system.

The similarities between EWS also mean that they could be improved by adapting methods from other systems. For example, landslide and flash flood EWS work on similar timescales and spatial resolutions, so could work together. The short range capabilities of these systems could also benefit other EWS, as could their rapid response times. The research also highlights the strong coordination in the coastal warning community, which brings together several different institutions and often makes information freely available online.

The study also identifies several important challenges for EWS, such as the need for integrated systems that can respond to multiple different hazards that cross national boundaries. Such initiatives are already being developed, and examples include the European Flood Alert System and the World Meteorological Organization’s Severe Weather Information Centre.

Future EWS also need to improve data visualisation and the ways in which information and warnings are shared. This should include information on hazard location and type, expected onset and duration, severity and likelihood of exceeding warning thresholds. This information needs to be easily accessible and easy to understand. Finally, the researchers recommend that EWS are integrated into government policy and disaster responses, and stakeholders, including local communities, are trained in emergency procedures following a warning.

1. See: http://ec.europa.eu/environment/water/flood_risk/index.htm
2. See: www.unisdr.org/2005/wcdr/intergover/official-doc/L-docs/Hyogo-framework-for-action-english.pdf
3. Knowledge-based approach to develop a cULTUre of Risk prevention (KULTURisk) is supported by the European Commission under the Seventh Framework Programme. See: www.kulturisk.eu