Benefits of flood defences outweigh costs says study

Flooding in Lancaster. Claughton
Flooding in Lancaster. Claughton

Building dams to protect against climate change-fuelled floods saves cash, according to new research.

The long-term benefits far outweigh the cost - across the world, according to the first study of its kind.

Flooding on Church Street in Croston

Flooding on Church Street in Croston

It's even possible to reduce economic damage to below today's levels - even when global warming, growing populations and urbanisation are taken into account.

The findings come in the wake of the most extreme flooding on record across parts of the UK.

Co-author Professor Paul Bates, of Bristol University's school of geographical sciences and one of the co-authors of the research, said: "We've known for some time in countries such as the UK and the Netherlands the economic benefits of building flood defences far outweigh the costs.

"The main finding from this paper is to show this is also true more generally across the globe.

The railway bridge at Euxton

The railway bridge at Euxton

"Investment in flood defences is an effective measure for a wide range of countries and this paper helps provide policy makers with the evidence they need to better protect their populations."

Storm Desmond that devastated northern England - as well as parts of southern Scotland - caused an estimated insurance bill of more than £1.3bn.

The appraisal of the heavy rain of 2015-2016 revealed it ranked alongside the flooding of March 1947 as the largest event of the past century.

Prof Bates and colleagues assessed how much flood damage could be avoided in the future if new dikes are constructed - or those that are already in place are heightened.

They then assessed how much it would cost to build and maintain them and whether they would be cost-effective using a range of hydrological and economic models.

Study leader Dr Philip Ward, of Vrije University in Amsterdam, said: "It's well-known economic damages from floods are expected to increase over the coming decades due to climate change and an increase in population and assets in flood prone areas.

"However in this study we show flood damages in the year 2080 can actually be reduced to below today's level if we effectively invest in flood protection measures.

This is important information for policy-makers.

"The results help identify those regions where we could efficiently invest in flood protection and also highlight those regions in which other adaptation strategies may be needed like creating more room for rivers and constructing flood-resistant buildings."

The researchers hope the findings published in Nature Climate Change will allow for more informed dialogue on flood risk management at an international level.

Whilst past studies have shown flood risk will increase in the future this is the first to examine how this can be effectively addressed at the global scale.

The results and methods will be integrated in the Aqueduct Global Flood Analyzer, a tool developed by the World Resources Institute (WRI) in Washington DC.

Charles Iceland, aqueduct director at WRI, said: "In order to develop sound flood prevention strategies decision-makers need reliable estimates of the costs of building flood protection infrastructure and the benefits of that infrastructure in preventing future damages.

"We are in the process of working with the World Bank to incorporate these new cost and benefit estimates into the next version of the Aqueduct Global Flood Analyzer.

"The World Bank will use the resulting cost-benefit assessment tool to inform strategic dialogues with developing countries facing significant flood risk."

During Storm Desmond about 5,200 homes were flooded in Cumbria and Lancashire while tens of thousands more lost power after an electricity sub-station in Lancaster was flooded.

As well as Desmond,major storms Abigail, Frank and Gertrude also hit the UK that winter.