Emergency services worked into the night on Sunday at a reservoir in central England that threatens to flood an entire town, following further heavy rain.

More than 1,500 people have been evacuated from the Derbyshire town of Whaley Bridge after part of the dam wall holding back the Toddbrook Reservoir collapsed on Thursday following downpours.

Crews have been working around the clock to pump water out of the reservoir, with the level reduced by over four metres by Sunday, according to the Canal and River Trust, which owns the reservoir.

"We have planned ahead of time to ensure we have sufficient pumps working through the night to mitigate against the expected rainfall," the trust said, adding that the reservoir was only at 55 percent capacity.

A military Chinook helicopter has meanwhile also dropped 530 tonnes of aggregate to shore up the damaged part of the dam, and it is now being cemented into place.

"The levels of the reservoir are being monitored closely, including the impact that this is having on the wall and the surrounding infrastructure," Derbyshire police said in a statement.

Police said once a stable level was reached to allow engineers to assess damage to the wall, authorities would decide whether residents and businesses could return to Whaley Bridge.

Residents were allowed back on Saturday to collect any essential items, but this was stopped on Sunday.

"The current situation at the reservoir is still critical and the threat to life remains very high," said deputy police chief Rachel Swann.

If the dam fails, emergency services vehicles will sound their horns three times while a loud hailer will also blast out across the town — where some families have decided to stay put.

Prime Minister Boris Johnson visited the area on Friday, where he said the 180-year-old dam would require a "major rebuild".

Efforts to shore up UK dam intensify ahead of storms
Whaley Bridge, United Kingdom (AFP) Aug 3, 2019 – Emergency services battling to stop a reservoir dam in central England from collapsing brought in new pumps Saturday to reduce the water levels, as more storms were forecast.

Hundreds of people have been evacuated from the Derbyshire town of Whaley Bridge, after part of the dam holding back the Toddbrook Reservoir above them collapsed following heavy rain.

The Met Office weather centre warned of further downpours and thunderstorms in the area on Sunday.

During a visit on Friday evening, Prime Minister Boris Johnson described the dam wall as "dodgy but stable", but said the 180-year-old structure would require a "major rebuild".

A Royal Air Force Chinook helicopter has been dropping bags of aggregate onto the section of the dam spillway which was damaged on Thursday after heavy downpours.

A police spokeswoman told AFP that extra pumps were being put in on Saturday as officials raced to bring the water level down in the reservoir.

After two nights out of their homes, some locals were allowed back briefly on Saturday to collect any essential items — and family pets — but warned that there remained a high risk to life in the area.

British town evacuated as dam disintegrates
Whaley Bridge, United Kingdom (AFP) Aug 2, 2019 –

Hundreds of people were evacuated from a town in central England as a British military helicopter was called in Friday to prevent a reservoir dam from collapsing.

The Toddbrook Reservoir dam was feared to be on the verge of caving in following heavy rain, threatening the lives and homes of residents in Whaley Bridge.

One side of the dam spillway weakened when the panels started to come away on Thursday.

A Royal Air Force (RAF) helicopter lowered bags of aggregate into the damaged part of the dam wall on Friday, while 150 firefighters, deployed from around the country, have been pumping water out of the reservoir.

"It is a critical situation," said Julie Sharman, chief operating officer of the Canal and River Trust which runs the reservoir.

She said water levels had reduced by around eight inches (20 centimetres) overnight.

The British government has issued a "severe flooding — danger to life" warning for the area directly below the dam.

Standing at a police cordon, Sarah Hamlet, 32, a company director, told AFP: "It's very surreal. It doesn't seem like it's happening at all. It genuinely is a nightmare."

Whaley Bridge in Derbyshire is on the edge of the Peak District National Park and 16 miles (26 kilometres) southeast of the city of Manchester.

The reservoir, which contains around 1.3 million tonnes of water, dates back to the 19th century.

Fast-flowing water had been rushing over the spillway before the collapse.

– Residents 'cut off' –

"The rest of the village, if it actually bursts, it'll wipe it out because there's a school just at the bottom of the reservoir, there's a park for the kids at the bottom of the reservoir, and all the shops and amenities are there," said Martin, 56, a builder who lives in Whaley Bridge.

"And the train track is actually at the bottom and I've just found out that they've stopped all the trains now. So you're virtually cut off. If you go out of the town, you can't get back in," he told AFP.

The RAF Chinook heavy-lift helicopter was dropping some 400 one-tonne bags of sand, gravel and stone into place.

Prime Minister Boris Johnson said: "My thoughts are with those who have had to leave their homes and all of those who are affected.

"First responders, engineers and RAF crews are working around the clock to fix the dam."

Derbyshire Police assistant chief constable Kem Mehmet said more than a thousand people had been evacuated from areas that would be flooded immediately if the dam wall failed.

"As there is still a risk the dam will fail, please stay away from the area," he said.

He said "everything humanly possible" was being done "to save the reservoir wall and to protect the town".