People are being urged to avoid the area around Toddbrook Reservoir after heavy rain caused damage to a dam wall.
Whaley Bridge Memorial Park has been closed and people are urged to not visit the area.
Photos sent in by readers appear to show damage to part of the dam wall at Toddbrook Reservoir.
A spokesperson for Derbyshire police said: "Officers are currently in attendance at an incident at the Toddbrook Reservoir following reports of damage to a wall of the reservoir.
"There are currently a number of road closures with local diversions in place.
"At this stage we are not evacuating the area and we are working with partners to assess the stability of the structure.
"People are asked to avoid the area at this time and further information will made available as we have it."
Derbyshire Fire and Rescue Service are also in attendance.
The reservoir is owned by the Canal & River Trust. A spokesperson for the organisation said: "We’ve got a team of engineers on site at the moment assessing the damage and determining what the next steps are.
"We’ll be in a position to provide updates as things become clearer."
This video, captured on Wednesday night by Phil Smith, shows flooding in the memorial park.
A further warning for rain has been issued by the Met Office and is in force from noon today until 8pm.