The Leigh flood storage area (FSA) was built in 1982 following the devastating 1968 floods. It reduces the risk of flooding to 965 properties and 300 businesses in the town of Tonbridge, Kent.
The Leigh FSA is formed by a 1.3 kilometre-long, five-metre-high earth embankment across the Medway valley. The River Medway passes through a reinforced concrete control structure built into the embankment.
The 3 steel radial gates can be moved to either let the river flow normally, or to restrict the flow and hold water in the FSA, to control the amount of water flowing downstream.
The Environment Agency operates it at the peak of a flood event, when river levels passing through the structure are at their highest. However, at times of exceptional rainfall there will still be some flooding downstream, although this will be much less than if the FSA were not there.
Flooding on Christmas Eve 2013
The wettest December in over 100 years led to saturated ground and very responsive rivers in this area of Kent and elsewhere. Between 19 and 25 December ,the Medway catchment received over 110 millimetres of rainfall.
At 5:00am on Tuesday 24 December, the Leigh FSA was empty and the River Medway was flowing unrestricted in its normal channel. It was from this time that the Environment Agency started to store water to reduce river flows downstream. By 8:00pm, the FSA was storing water within 10 millimetres of its maximum limit of 5.5 million cubic metres of water.
Without the Leigh FSA, it has been calculated that a peak flow of 300 cubic metres of water per second would have passed through Tonbridge and other downstream communities. But by operating it, the Environment Agency could halve the amount of flow downstream.
The future of the Leigh FSA
Following the flooding over Christmas 2013, the Environment Agency is investigating what improvements can be made to increase the level of protection offered by the Leigh FSA. This includes the option of increasing storage by as much as 30 per cent. They are working with partners, including Kent County Council to raise the funds needed to progress this scheme more quickly than originally planned.
For more information about how the Leigh FSA works and how we operate it during flood events please contact the Environment Agency on 03708 506506 or email: firstname.lastname@example.org