Impact on reservoirs of 2007 summer floods
Reservoir incidents
Eighteen reservoir incidents were reported to us during the floods in June and July. Most of the incidents occurred in the Midlands, North East and North West of England. These incidents were due to the intense rainfall in the catchments from which the reservoirs collect water.
Most reservoirs are built with an overflow to help manage additional water. Once the water in a reservoir reaches a certain level the water would then go down the overflow. The majority of the incidents during the floods related to reservoirs where the overflow couldn’t take any more water and therefore the water went over or was close to the top of the dam.
When the water in a reservoir flows over an earth embankment it can cause serious erosion damage, threatening the stability of the structure.
Ulley Reservoir
The most high profile incident occurred at Ulley Reservoir in South Yorkshire. A torrent of floodwater damaged a section of the masonry spillway and eroded part of the reservoir embankment. A huge multi-agency effort was needed to drain the reservoir and to make emergency repairs, preventing a possible collapse and major flooding downstream.
During the event 1,000 people were evacuated from their homes in Catcliffe, Whiston and Treeton as a result of the situation at Ulley Reservoir and because of flooding from the River Rother. The M1 motorway was also closed for over 40 hours.
In our role as lead reservoir authority, we’ve commissioned an investigation into the events at Ulley and are working closely with the industry to make sure lessons are learnt and to further improve reservoir safety in future.
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More information about reservoir safety and how they are regulated.