Saving lives and reducing damage with flood early warnings

By Professor Hannah Cloke, hydrologist, Water@Reading

If you knew there was a strong chance that your local river was about to burst its banks and sweep away your house, you’d get yourself, and your family, out of harm’s way.

Yet tragically, despite major advances in flood forecasting, hundreds of people every year still die in floods. Either warnings are not getting through, or people and authorities are failing to take appropriate action.

Severe flooding brought on by a strong coastal El Nino has left more than 90 dead and hundreds of thousands homeless in Northern Peru [photo: Maria-Helena Ramos]

This month has again seen severe flooding in many parts of the world, including Peru and Australia, leading to loss of life and destruction of homes and livelihoods.

We will never be able to stop such awful floods. But there are some vital steps that we can take to reduce the risk from these events and to save lives.

In recent years we have been taking great strides in our capability to provide early flood warnings, so that people can prepare for upcoming floods – often before it even starts to rain.

The Water@Reading research group at the University of Reading works alongside flood forecasters to develop better forecasts and warnings, such as those of the European Flood Awareness System (EFAS) and the Global Flood Awareness System (GloFAS), part of the EU’s Copernicus Emergency Management Service.

But how do we know if we’re doing a good job? How can we convince people that the warnings are accurate, and worth acting on?

A first step is to consider how much we have been able to improve the value of the flood forecasts. We undertook a continental scale analysis of potential avoided flood damages and thousands of flood forecasts from the EFAS and we’ve estimated that there is a substantial monetary benefit in cross-border continental-scale flood early warning systems.

Evidence for investment

In Europe, the benefits are substantial – saving around £400 of avoided damage for every £1 invested in flood forecasts.

These flood forecasting systems are expensive. They are very complicated to run and test, and eat up computer processing power and data, meaning only the world’s most powerful supercomputers are capable of running them. But it is crucial that efforts to assess their effectiveness don’t just focus on average water levels in all our rivers – instead, we must concentrate on the areas where people actually live.

We need strong evidence that shows how improving the science behind the early warning system will improve the outcome for people receiving the warnings. In short, we must show how extra investment in the science will help save lives, and protect property.

Our research, published this week in Environmental Research Letters, shows for the first time that value of the EFAS forecasts is increased substantially by using forecasts from many different weather forecasting centres as inputs to our flood forecasting system.

These findings underline the fact that effective disaster risk management has collaboration and partnership at its heart.

We can use this evidence to support development in other continents. This will help improve resilience to floods, particularly in some of the world’s most vulnerable areas, where early warning systems could make a real difference to saving lives and reducing disaster risk.

Reference: Hannah L Cloke, Florian Pappenberger, Paul J Smithand Fredrik Wetterhall (2017) How do I know if I’ve improved my continental scale flood early warning system?  Environmental Research Letters doi: 10.1088/1748-9326/aa625a 

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