AN “UNPRECEDENTED” combination of factors led to the disastrous flooding across the borough on Boxing Day, Environment Agency officials have said.

Speaking at a public question time held at Radcliffe Civic Suite last Thursday, Mark Garratt, the authority’s area flood risk manager, told residents that the extreme levels of rain coupled with a severely saturated catchment area caused the chaos that affected hundreds of homes.

He was joined by council chief executive Mike Owen, council leader Cllr Mike Connolly, and the borough’s MPs, David Nuttall and Ivan Lewis, as they answered questions from an audience of over 100 flood victims.

Residents from Radcliffe, Bury, Summerseat, and Ramsbottom were all present and demanded answers on why the flooding had been so severe.

A written answer from the Environment Agency and Bury Council given to members of the Radcliffe Residents Flood Action Group said: “This is a ‘flashy’ river catchment – meaning the natural topography of the land can have a significant influence on how quickly river levels rise and fall.

“There are steep gradients upstream of the Irwell and shallow soils on underlying bedrock which means rainfall run-off to the river is rapid. What we saw on Boxing Day was approximately a month’s worth of rainfall in 24 hours on an already saturated catchment.

“This combination of factors – extreme rain, a saturated catchment with steep upstream gradients meant river levels responded dramatically. The scale of what occurred was unprecedented.

“All of the river gauges across the area registered the highest ever levels since records began in 1937. This was a natural phenomenon.”

Even if the EA had dredged or widened the rivers beforehand it would have made “little difference” because of the scale of the rainfall, Mr Garratt said.

Rumours that have been circulating since Boxing Day about flood gates downstream being closed or malfunctioning were also strongly refuted.

The statement added: “There are no mechanical gates or sluices within the river channel. The River Irwell ultimately flows into the Manchester Ship Canal that does have locks and sluices.

“Should these not have worked then Salford Quays would have been affected. Bury is such a distance away and also at a higher elevation, so it would not have been affected by defence works downstream.”

Environment Agency officials also gave reasons for the lack of flood warnings issued on Boxing Day, saying unexpected changes in the forecast and damaged or destroyed equipment were to blame.

They said: “There was a significant shift in the forecast that brought Storm Eva further south than was anticipated. The rainfall totals were also double what was anticipated. This, combined with the speed river levels responded, meant the existing flood warning service was placed under extreme pressure.

“Various gauges were damaged and in some cases destroyed. Due to the rapid nature of the event, several hundred river alarms were triggered simultaneously. The EA is reviewing the system to make it more robust and already have plans in place to improve the network, including: repairing damaged assets; reviewing our current trigger levels and thresholds; improving our forecast models using the extreme data from Boxing Day; using data to create more targeted flood warning areas; reviewing how warnings are received by local people.

“The EA and Bury Council are very keen to work with the community on this and around the possibility of setting up a flood action group. This would help improve communications, planning and preparations before incidents occur.”