Thousands evacuated amid fears UK's Toddbrook Reservoir will collapse
Water flowing into a damaged reservoir feared to be on the edge of collapse has been "reduced considerably" after efforts by the military and emergency services.
Thousands of people were evacuated after Toddbrook Reservoir - which contains around 1.3 million tonnes of water - threatened to flood the Derbyshire town of Whaley Bridge.
But an RAF Chinook and firefighters using high-volume pumps appear to have stabilised the "unprecedented, fast-moving, emergency situation" caused by heavy rain.
Images taken early on Friday morning show the helicopter dropping one-ton sandbags to bolster the damaged part of the structure.
Julie Sharman, chief operating officer of the Canal and River Trust which runs the reservoir, said securing the dam and lowering water levels further was the main priority.
She told BBC Radio 4's Today programme: "The operation loading the front face of the dam using the Chinook helicopter is in process and is going to go on for most of the day here.
"Additional pumping is going in and the good news is that the inflow to the reservoir has reduced considerably.
"We've lowered the level of the water in the reservoir by 200mm. We are obviously aiming to get that down considerably more."
Police have also closed railway lines in the Whaley Bridge area over the flood fears.
The annual inspection of the structure by a senior engineer was last November, said Richard Parry, chief executive of the Canal and River Trust.
After thousands spent the night away from their homes, police said a timescale for evacuees returning is "currently unknown".
Carolyn Whittle, who lives in Meadowfield, on the hillside in Whaley Bridge, said: "I've lived in Whaley (Bridge) for the best part of 45 years, and I've never seen water flood over the dam like that, ever, nor thought that we could possibly be at risk in this way."
The Environment Agency issued a "danger to life" warning covering the River Goyt on Thursday, as the river could "rise rapidly" due to water rushing in from the reservoir.
Toddbrook Reservoir is on the north-west edge of the Peak District National Park and was built in 1831, according to experts, although the Environment Agency record it as being built in 1840-41.
The structure supplies water to the Peak Forest Canal, a waterway running between the town and Ashton under Lyne, Greater Manchester.