New tool to aid defence schemes using facts from Leeds Boxing Day floods

University academics in Yorkshire have developed an innovative measurement to calculate the effectiveness of flood defence schemes after using data from the Boxing Day disaster five years ago.

Saturday, 28th March 2020, 6:00 am

A team of mathematicians from the University of Leeds have produced a protocol to show cost effective defence schemes based on results from the floods, which caused £500m damage to homes and businesses, over the festive period on 2015.

Professor Onno Bokhove, one of the project’s researchers from the university, said the work started after the Environment Agency wanted to develop the science underlying flood mitigation to help shape future policies.

“They wanted something that was more accessible, a way of communicating complex ideas clearly and simply,” said Professor Bokhove.

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Ultimately, the direct cost to the city was an estimated 36.8m, with the cost to the wider city region being more than 500m, according to Leeds Council. Photo credit: Other

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The graphic is overlaid with the options to hold back or to capture the flood waters, and how much each option will cost.

The researchers say the project will result in better decision making.

The work is a collaboration between applied mathematicians from the University of Leeds and civil engineers from the Université Grenoble Alpes in France.

The researchers have devised a graph that takes a hypothetical lake which is 6ft deep and the amount of water that needs to be contained in a valley to stop the river flooding. Photo credit: Other

The scientists revisited a concept at the heart of flood analysis, known as flood-excess volume (FEV).

To illustrate the idea, they used direct data from the floods which affected large parts of the UK on Boxing Day in 2015, including Leeds where huge amounts of water flooded from the River Aire.

The River Aire at Leeds Crown Point, which is usually 3ft high, rose to 9.5ft at 1am on December 27.

Its previous high was 8ft, recorded in June 2007.

A pedestrian wades through floodwater on Kirkstall Road Leeds past an abandoned car after the River Aire burst its banks. Photo credit: Tony Johnson

The volume of flood water that swamped Leeds translates into the hypothetical square lake, 6ft deep and with sides of 1.3-mile in length, that has been used in the anaylsis.

Professor Bokhove said to have prevented the flood, somewhere along the course of the river water preventative measures could have been put in place.

The researchers have also proposed a hypothetical scheme for increasing the flood defences to handle not only a one-in-100-year flood but also a one-in-200-year flood.

Over the six years to 2021, the Government will have spent £2.6bn on flood schemes in England, and further investment is expected.

Professor Bokhove is working alongside Professor Mark Kelmanson and Dr Tom Kent from the University of Leeds, and civil engineers Dr Guillaume Piton and Dr Jean-Marc Tacnet from the Université Grenoble Alpes.