Environment Agency in York gives its fullest account yet of why it raised the Foss barrier on Boxing Day

On Boxing Day, however, it wasn't the Ouse that was the main problem.

Yes, water levels in York's main river were eventually to rise to levels only a couple of centimetres below those of the great 2000 floods.

But what Environment Agency staff began to realise as Boxing Day dawned was that water levels in the Foss were rising even faster and quicker.

The Foss has a different catchment area to the Ouse. Water flows into the Foss from Easingwold and beyond. The ground upstream was already saturated after six weeks of rain, says the Environment Agency's flood resilience team leader Jon Knight. When another rainstorm burst, water levels in the Foss quickly began to rise.

They reached completely unprecedented, record levels. At the height of the 2000 floods, 17 tonnes of water a second were flowing through the Foss at Huntington. On Boxing Day 2015, the flow had soared to an incredible 25 tonnes of water a second. Further downstream, water from the flooded Tang Hall and Osbaldwick becks was also pouring into the swollen river.

For most of the day on Boxing Day, the Foss barrier remained closed, to prevent water from the Ouse backing up into the Foss basin. But there came a point when water levels in the Foss were actually higher than in the Ouse, says Environment Agency spokesman Steve Kirman. And they were still rising.

There was a reason for that. The Foss barrier, when lowered, acts as a dam to stop water from the Ouse backing up into the Foss. But it also stops water from the Foss escaping into the Ouse.

There are eight huge pumps which, in normal conditions, pump the water from the Foss out past the barrier and directly into the Ouse. If they didn't do that, the whole Foss basin would flood every time the barrier was lowered.

Between them, those eight pumps are able to cope with up to 30 tonnes of water every second. "That's the equivalent of a fuel tanker full of water every second," says Jon Knight.

A dam that can be opened. The Foss barrier

But on Boxing Day, the Environment Agency estimates there could have been as much as 35 tonnes of water every second flowing down into the mouth of the Foss. That's more than the pumps could cope with - which was why the water on the Foss side of the barrier was rising.

As early as 7am, the agency issued a flood alert. That was followed, at 10.41 am, by a more serious flood warning. "We knew that the pumps were struggling to cope," Jon Knight says.

Water volumes in the Foss continued to rise. At 11am, the agency held a telephone conference with the police, the city council and the fire service to discuss the worsening situation.

And still the levels of the Foss continued to rise. Then, to their horror, Environment Agency engineers realised that floodwater was actually seeping into the building that housed the electrics for the Foss barrier pumps.

A rescue operation in the Walmgate area

The building has waterproof doors and was supposed to be sealed. "But the water was starting to come in from underneath the building," says Steve Kirman.

Just why is one of the big questions that remains to be answered. But on that Boxing Day, with the waters rising and rising on the Foss side of the barriers, the Environment Agency was faced with a terrible decision.

There was a risk that the electrics could fail, which would mean the Foss barrier would be immovable. Should they leave it closed, in which case, with the pumps failing, it would dam the Foss? Or should they raise it, so that at least the waters of the Foss could get out into the Ouse?

At about 7pm that day, the decision was taken to raise the barrier. The reasoning was that this would allow the Foss to flow into the Ouse, thereby slowing the rate at which the Foss was rising, giving people more time, not less, to evacuate their properties.

At about the same time, a severe flood warning was sent out - a warning that there was a possible risk to life.

The decision to raise the barrier was taken collectively, by the Environment Agency's flood risk engineers and emergency planners, says Jon Knight. As the flood resilience team leader, he was one of the group that made the call.

It wasn't an easy decision.

"It was a tough decision for anybody who loves York. I live in York, and for me it was heartbreaking. But we knew that it was the right decision."

It wasn't a question of sacrificing a few hundred homes in the Foss basin to save others elsewhere, Steve Kirman stresses. "Those 600 properties - they would have flooded either way." But if the barrier had been left down, hundreds more homes and properties in the Foss basin would have flooded as well, as the waters of the Foss were dammed. "There would have been a more rapid inundation, which would have flooded up to 1,000 more homes," says Mr Knight. "They would have flooded more quickly, for longer and deeper."

The clean-up in the Huntington Road area

Questions remain. How could the building housing the barrier's electrics have flooded? Does the capacity of the barrier need to be increased? Why wasn't the Environment Agency aware in advance that the Foss barrier could potentially be overwhelmed in this way? And, given the increasing frequency and extent of floods, why hasn't the barrier ever been upgraded?

Given the extraordinary conditions on Boxing Day, however, the agency insists that on the day it made the right call.

Should the Environment Agency have been better prepared?

York Central MP Rachael Maskell has been asking some tough questions about why the Environment Agency wasn't better prepared for the failure of the Foss barrier.

Successive reports showed that the risk had been understood for years, she claimed - and yet no action to upgrade the barrier had been taken.

"I want to know why no action was taken to increase the capacity of the pumps at the barrier," she said.

A Mountain Rescue team takes Yorkshire Water officials to the Castle Mills pumping station

It is a question that the agency has yet to directly answer. It did, however, issue the following statement: “The building that houses the electrical systems was designed to be resilient and has watertight seals on all access doors. We know water got into the systems room and we are investigating why and how this happened and what needs to be done to safeguard its resilience in future. Whilst this investigation is ongoing we are not able to comment on the circumstances.

“The barrier is now operational again. The Environment Agency along with the military, with the support of our various contractors and the emergency services, worked round the clock to reinstate power to the barrier and the pumps and it was fully operational again on 30 December 2015."

The agency admits, however, that further work will be needed to permanently restore the barrier and improve its 'resilience'.

The Government recently announced that it would give £10 million to improve flood defences in York - money that will be spend mostly on the Foss barrier.

So what might it be spent on?

It is too early to say yet, the agency insists. But clearly something will need to be done to ensure the electrics don't flood again. The pumps themselves can't be raised, because they need to be able to pump water - but the electrics that operate them could be.

Increasing the capacity of the barrier might also involve adding extra pumps.

The agency won't be drawn. For now, it will say only that "we will advise local communities what the plan is ... in due course."

Were homeowners and businesses given enough warning?

The Agency says it put out three warnings on Boxing Day alone; a flood alert at about 7am; a flood warning at 10.41am; and a severe flood warning at about 7pm.

All of those alerts would have gone to anyone who had signed up for flood alerts. In addition, warnings were sent to landlines associated with properties in flood risk areas, and were put out through the media. The agency estimates that warnings were sent to about 80 per cent of properties at risk of flooding.

A future of more extreme flooding

Because of climate change, regular flooding is going to be a part of life in future, says the Environment Agency's flood resilience team leader Jon Knight - not just in York, but across the country and around the world.

"There will be more extreme rainfall, more extreme floods."

That means that cities like York will have to make themselves more 'resilient' - more able to cope with floods.

The city already is very resilient, Mr Knight says: just look at how pubs like the King's Arms on Queen's Staith is able to cope with being flooded three or four times a year.

But in future more businesses and ordinary householders in flood risk areas will have to become so.

So what should we all be doing?

The first thing is to find out whether your home or business is at risk of flooding, Mr Knight says.

You can do that quickly by visiting the government's flood risk website, www.gov.uk/check-if-youre-at-risk-of-flooding If you are in a flood risk area, you should sign up for flood alerts, Mr Knight says, by calling the 24-hour floodline on 0345 988 1188.

You should then try to do what you can to make sure your property is more resilient.

Have hard flooring with moveable rugs rather than carpets on ground floors. Think about moving the electrics higher up your walls. And above all, have a plan. "Be ready, for example, to move your valuables upstairs."

You can find out more about how to prepare your property for flooding at gov.uk/prepare-for-a-flood/improve-your-propertys-flood-protection