Gravel removal is set to start within weeks as part of key work to reduce Carlisle’s flood risk.

Long term improvements to the city’s flood defences are still a few years away, but Environment Agency (EA) bosses insist they are doing everything they can ahead of the upcoming winter.

A key part of that is gravel removal at trigger points – particularly Holme Head Bay at Denton Holme, where contractors are set to move onto the site to remove an estimated 7,000 to 10,000 tonnes of gravel from the River Caldew.

Andy Brown, the EA’s flood and coastal risk manager, explained that it is not a case of taking out gravel right along the waterway. Instead they have a considered approach focusing on problem areas.

“Across the city we’ve got a number of strategic, significant points – locations where we monitor the build up of gravel,” he said.

Craig Cowperthwaite, a senior flood management advisor, explained that if it builds up in these locations it can have a knock-on effect downstream, adding to the flood risk

Holme Head weir at Denton Holme is one of the key points in Carlisle – and gravel levels are currently high following the last floods.

He added: “It’s about taking the gravel out where it has the most impact in reducing flood risk. If you take the gravel outI here you do not have to take it out further down the river.”

Mr Brown explained that when they built the flood wall at Denton Holme they deliberately included a large access gate and ramp at Holme Head to ensure they can get in and out easily with machinery.

There are other similar trigger points elsewhere. They also monitor the build up of vegetation and islands, which can slow water flow.

And Mr Cowperthwaite said that although the 2005 and 2015 floods had the biggest impact on Carlisle in terms of properties, the Caldew’s highest levels were actually recorded in 2012. “It wasn’t as widely reported because no homes flooded but it was actually June 2012,” he said.

Mr Brown is keen to stress that December’s devastating floods were not caused by the defences failing.

“There was very little damage to the main defences – 10km of defences protecting the city. There was a bit of damage to the floodbank at Willowholme, where we did some repair works, but not much else,” he said. The problem was the height of the water.

He explained that the walls, built after the 2005 floods, were built to withstand a certain level based on the probability of major flooding. But they can’t guarantee when these exceptional events will happen, as Cumbria discovered.

Mr Brown said this time the problem, not experienced previously to the same extent, was not just heavy rainfall from a single storm, but the “clustering” of severe weather events – something he said appears to be happening more frequently.

For example in November last year it was initially believed Storm Abigail was going to hit Cumbria hard, prompting major resilience preparations. However, its course changed and disaster was averted – until Desmond hit a few weeks later. This was followed closely by Eva and Frank, which all had further effects on the already-troubled county.

Mr Brown said the solution, long term, may be upstream water storage, to help reduce flows down from higher ground so rivers can cope better. But this won’t happen overnight.

He also expects some of the flood walls to be built higher, but said all these things need careful planning to ensure they don’t simply move the problem from one place to another.

As part of this they have been analysing exactly where the water came from during the floods, and said it is not as simple as if the river’s getting high and the water over-topping the defences. For example, Carlisle’s Viaduct Estate was left underwater during the floods but investigations have revealed that rather than going over the wall, water initially came down an unexpected route.

Mr Brown said: “What’s happened is that flood water has gotten on to the railway line further up and come in that way. At this point the flood wall was still holding. For me this is where the conversation changes. It’s suddenly not just about flood defences but also about how the road and railway network affects flood risk. How they can act as a flow route.”

Why didn’t that happen in 2005? Mr Cowperthwaite says it is because back then there was no flood wall, so the river started flooding the area much earlier.

“You can see that managing flood risk is like a jigsaw puzzle, putting all these pieces together,” he added.

Meetings are now underway with Network Rail to talk about what investment is needed to eliminate these risks in the future. Repair work is also set to start soon around Botcherby Bridge, which many believe acted as a dam and added to the flooding in that part of the city. The future of that structure will be reviewed, but again it is unlikely major changes will happen quickly.

Mr Brown says that although the Caldew and the Petteril were affected, the main problem during Storm Desmond was the Eden, which had a knock on effect elsewhere.

There are calls to reopen one of the closed arches at Eden Bridge. Mr Cowperthwaite said that was a possibility, but they first need to analyse what impact that would have downstream.

In Denton Holme the defences held, and most of this area escaped - unlike 2005.

“The thing is no two floods are ever the same. What we now have to plan for is something that allows for the Caldew, Petteril and Eden all peaking at the same time as high tide.

“I’d be surprised if we do not end up doing something upstream, and I’d be surprised if we are not looking to increase the height of some of the defences we already have,” Mr Brown said.

The village of Rickerby, which has flooded repeatedly, has been allocated funding for defences, which could be one of the first schemes to be delivered. In the meantime temporary defences, which the EA has previously said could be used to protect parts of Cumbria until long term solutions are found, could be an option.

Mr Brown said there is a national stockpile which is now being expanded.

But for safety reasons they can only be used in certain circumstances, depending on the speed of the river flow for example.

“In theory it might be possible to use them in parts of Carlisle,” he said. “But we had record-breaking overflows on the Eden, so we’d have to be sure they would hold up at those speeds.”

As for the long term schemes, campaigners in Carlisle have been calling for the EA to bring in experts from other countries to help hurry these along.

But Mr Brown insisted they are already working with these companies and described the criticism as “misguided”.