New way to predict river flood risk could help prepare for disasters

We could now have the ability to higher predict which rivers are prone to excessive flooding, even when they haven’t brought about extreme floods earlier than.

Extreme flooding, such because the devastating 2021 floods in Germany that killed a minimum of 196 individuals, is tough to foretell, says Stefano Basso on the Norwegian Institute for Water Research in Oslo. Typically, researchers solely know a river is liable to excessive floods if this has occurred previously. “For this method to work, you have to wait for something bad to happen,” says Basso.

To search for different methods to foretell excessive flood threat, Basso and his colleagues analysed discharge and flooding knowledge from 101 rivers in Germany and the US going again a minimum of 30 years.

They break up the floods into two teams: those who have been small in magnitude and anticipated for that river, and those who have been excessive. The second group consisted of floods that have been between 20 and 35 instances greater than a traditional flood for a selected river.

The researchers studied the properties of the rivers that had skilled these excessive floods, together with elements reminiscent of magnitude and frequency of rainfall and the way rapidly water appeared to move from the encircling areas to the river.

From this evaluation, the researchers got here up with two parameters that appeared to clarify whether or not a river was more likely to trigger excessive flooding or not: how the realm draining to the river (referred to as the river basin) retains and releases water, and the steadiness between how a lot rain the river receives and the way a lot water evaporates from the area.

Basso and his colleagues then analysed knowledge going again a minimum of 10 years from 2519 rivers in Germany and the US, utilizing these two parameters to find out whether or not a river was more likely to trigger excessive flooding or not.

They recognized a number of rivers in Germany and the US that haven’t had excessive floods, however are regarded as prone to them. In Germany, they embody the Rems river in Baden-Württemberg and the Wörnitz and Vils rivers in Bavaria. In the US, rivers prone to excessive flooding embody the Baron Fork of the Illinois river and the Cowpasture river in Virginia. The staff is at present utilizing its mannequin to foretell which rivers are prone to excessive flooding within the UK.

Being capable of predict excessive floods is essential, says Basso, as a result of it’s these floods in city areas that officers are sometimes unprepared for and trigger essentially the most injury.

“Hydrologists have known for some time that the most catastrophic floods are generated by different physical processes than smaller ‘normal’ floods, but the beauty of this study is that, for the first time, it identifies the places that are more likely to experience these disasters,” says Paul Bates on the University of Bristol, UK.