Derbyshire police has detailed the plan to secure the dam wall at Toddbrook Reservoir after it was badly damaged by heavy rain.
In a statement, the force's Deputy Chief Constable Rachel Swann said access to Whaley Bridge was stopped and parts of the town, as well as further areas downstream, were evacuated following an assessment by structural engineers.
Emergency services, partner agencies and volunteers remain at the scene, with help coming from across the country.
READ MORE: Toddbrook Reservoir: Chinook helicopter being brought in to Whaley Bridge to help secure dam wall
The plan to secure the dam wall now is:
* Use 400 tonnes of aggregate to divert water from entering the reservoir and into other surrounding watercourses designed for this purpose.
* Use water pumps to remove water from the reservoir to relieve pressure on the dam wall.
* Once the above measures reduce the water to a level that is safe – work will then begin on the dam wall itself.
READ MORE: Toddbrook Reservoir: More properties evacuated as work continues on Whaley Bridge dam - live updates
A Chinook helicopter is being brought in to help move the aggregate.