Perspective: Climate & infrastructureThe World's Aging Dams Are Not Built for Ever More Extreme Weather

The town of Whaley Bridge in the UK has had to be evacuated after damage to a dam built in 1831. The Toddbrook Reservoir is just one of many ageing dams worldwidenot designed for ever more extreme rainfall as the planet warms.

Michael Le Page writes in New Scientist that dams are typically designed to cope with a so-called 1-in-100-year flood event. But as the world warms the odds of extreme rainfall are changing, meaning the risk of failureis far greater. Engineers have been warning for yearsthat many old dams around the world are already unsafe and need upgrading or dismantling.

“The 1-in-100-year event is perhaps happening every five years,” says Roderick Smith at Imperial College London. “I’m absolutely convinced that it is due to climate change.”

What is happening at Toddbrook Reservoir, where 1500 people have had to evacuate, is very similar to what happened at the Oroville Dam in California in February 2017. Both are earthen dams where excess water flows over the top of the dam and down a concrete-lined spillway.

If this concrete is damaged, the water flowing down the spillway can rapidly erode the earth underneath, and there is a risk of the entire dam wall collapsing.

There is a much greater chance of this happening when extreme rainfall or melting of snow leads to very high water flows into already full dams. A 2018 study concluded that climate change exacerbated the high water flows that led to the erosion of the Oroville Dam spillway, where 190,000 people had to evacuate and repairs cost $1.1 billion.