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Environment Agency 'trigger points' target Somerset floods

The Environment Agency has produced seven ‘trigger point’ videos to show people in Somerset what it will do – where and when – to combat flooding.

The animations explain how the Environment Agency will use its 21 permanent pumping stations in Somerset and deploy mobile pumps when specific roads are flooding, heavy rainfall is forecast for the next 3-5 days (with a cumulative total of 100 mm or greater) and moor water levels are rising at 50 mm/hour, or higher. All three criteria will have to be for action to be taken.

Trigger points are needed because the Environment Agency’s permanent pumps in its pumping stations are set to operate automatically according to water levels in the rhynes draining the moor. These pumps cannot operate if the receiving river is full, when spillways are operating or river banks are overflowing.

(Rhynes are drainage ditches, or canals, used to turn areas of wetland at around sea level into useful pasture).

The Environment Agency’s trigger points are at:

• Currymoor, Saltmoor and Northmoor Pumping Stations

• Huish Episcopi Pumping Station

• Long Load Pumping Station

• Monk's Leaze Clyse

• Westonzoyland Pumping Station

• Westover Pumping Station

• West Sedgemoor Pumping Station


Currymoor, Saltmoor and Northmoor Pumping Stations

As Northmoor, Saltmoor and Currymoor triggers are interlinked, the Environment Agency has developed these together.

The level on Currymoor rises when Hookbridge Spillway runs, spilling water from the River Tone into Currymoor.  At this point, the permanent pumps cannot operate as the River Tone is full. Cuts Road floods first, and then New Road (between West Lyng and North Curry). 

The local trigger point is when New Road floods. The Environment Agency has designated this as the local trigger point for Northmoor, Saltmoor and Currymoor to ensure that it can put the additional temporary pump capacity in place well in advance of any likely increase in water levels in Northmoor and Saltmoor. This will ensure the temporary pumps are as effective as possible and will be installed in one go.


Huish Episcopi Pumping Station

When flooding is predicted the Environment Agency will manually close all inlets to the moor and water will continue through the river systems, as with Westover Pumping Station. The permanent pumps will continue to operate automatically until the River Yeo overtops its banks. The land starts to flood and then flooding reaches the Langport to Muchelney road, then the Muchelney to Long Load road.

The local trigger point for Huish Episcopi Pumping Station is when the Muchelney to Long Load road floods. At this point the Environment Agency will install additional temporary pumps at the pumping station to operate once the Yeo is below bank height.


Long Load Pumping Station

When flooding is predicted the Environment Agency will manually close all inlets to the moor and water will continue through the river systems. The permanent pumps will continue to operate until the River Yeo overtops its banks. 

Our local trigger point for Long Load is when the Long Sutton road floods. The Environment Agency will, at this point, install additional temporary pumps at the pumping station. As soon as the river is below bank height, the Environment Agency will turn on the pumps in sequence to avoid overtopping.


Monk's Leaze Clyse

When flooding is predicted, the Environment Agency opens Oath Lock. It also partially opens Monk's Leaze Clyse to lower river levels in the River Parrett and allow pumping to continue upstream of Langport.

At the onset of flooding, the Environment Agency closes Monk's Leaze Clyse because Allermoor and Beasley’s Spillways will run. (Having the Clyse open AND spillways running may increase the flood risk in the Sowy system.)

When the River Parrett levels are declining and spillways are predicted to stop running, the Environment Agency fully opens Monk's Leaze Clyse in stages to ensure that as, much as practicable, water in the Sowy is kept below bank height downstream of Beer Wall as desired by the Internal Drainage Board. 

The Environment Agency will install temporary pumps at Dunball before it fully opens Monk's Leaze Clyse.


Westonzoyland Pumping Station

When flooding is predicted, the Environment Agency will manually close all inlets to the moor and water will continue through the river systems. When flooding occurs and lowest fields flood, the Environment Agency will operate the permanent pump. The  local trigger point for Westonzoyland is when the lowest road in Middlezoy floods, then the Environment Agency will install an additional pump at the pumping station. All pumps operate on all but highest tide peaks.

NB: no additional pumps can be added at Lakewall.


Westover Pumping Station

When flooding is predicted, the Environment Agency will manually close all inlets to the moor and water will continue through the river systems. The permanent pumps will continue to operate automatically until the River Parrett overtops its banks upstream.  

The Drayton to Muchelney road floods first, then the lowest part of the Westover Trading Estate road. This is the local trigger point for Westover and at this point, the Environment Agency will install additional temporary pumps at the pumping station.


West Sedgemoor Pumping Station

The permanent pumps at West Sedgemoor will continue to operate automatically until the River Parrett reaches a level where Beasley’s Spillway runs. 

The Environment Agency’s local trigger point here is when the lowest roads flood. The Environment Agency will install additional temporary pumps at West Sedgemoor Pumping Station ready for when it can resume pumping. When Beasley’s Spillway stops running, the Environment Agency will turn on in sequence all permanent and temporary pumps.

If you would like to get in touch please contact us at sra@somerset.gov.uk or tel: 01823 355111
The Flood Action Plan is now overseen by the Somerset Rivers Authority and can be contacted on the above.