King's Sedgemoor Drain - Modern Era

Modern Era

The passing of the Land Drainage Act 1930 held promise for the future. The many bodies responsible for small parts of Somerset's flood defences were swept away, and replaced by the Somerset Catchment Board. More importantly, perhaps, they did not have to prove that benefits would occur to a particular community in order to issue rates for drainage work, but could raise rates based on the rateable values of properties. This should have worked, but they soon became apprehensive, and reverted to producing reports, which were not actioned. However, inactivity gave way to action in 1939, when a new engineer was appointed, who saw it as his job to direct what needed to be done. Work began on improvements to the King's Sedgemoor Drain in 1939. The items to be addressed were the size of the channel, the size of the bridges, and the size of Dunball clyse, all of which were too small. The onset of the Second World War, just a few months later, threatened to stop the scheme, but did not.

As part of the war effort, an explosives factory, ROF Bridgwater, was built at Puriton. The Catchment Board needed to be able to guarantee that 4.5 million gallons (20.5 Megalitres) of process water would be available to the factory every day. To this end, the Huntspill River was constructed, a little further to the north, which was essentially a revival of a plan by J. Aubrey Clark in 1853, to provide better drainage for the Brue valley. King's Sedgemoor drain was deemed to be a backup source for water, should the Huntspill scheme fail, and so all of the work which had been planned before the war started was completed, to ensure that the volume of water needed was always available. Greylake sluice was built by the Somerset Rivers Catchment Board in 1942, and used guillotine gates to control water levels. The original plaque commemorating its completion was incorporated into the new structure when the sluice was rebuilt in 2006.

The drain was upgraded in 1972, as part of a £1.4 million scheme to construct a flood relief channel for the River Parrett. The 7.5-mile (12.1 km) embanked channel, called the Sowy River, runs from Monks Leaze Clyse below Langport to the King's Sedgemoor Drain near Westonzoyland Airfield. Improvements to the drain included the relocation and rebuilding of the clyse at Dunball, to create a fresh water seal which prevents salt water from entering the drain where it joins the River Parrett. A further scheme for improvements to the Greylake Sluice was completed at a cost of £2.95 million in 2006, and resulted in the engineering contractor winning the 2006 Environment Agency Project Excellence Awards, for the health and safety and environmental risk aspects of the project. The main features of the new design were two tilting sluice gates, each 13 by 10 feet (4.0 by 3.0 m) contained in a structure which was only half as high as the previous structure, which allow water level management to be controlled in a more flexible manner.

Floodwater is removed from many of the moors of the Somerset Levels by pumping stations, which were originally steam-powered. These were superseded by diesel engines, and more recently by electric pumps. The King's Sedgemoor Drain is unusual in that it operates entirely by gravity. Consideration was given to replacing Dunball clyse with a pumping station in 2002, which would have allowed water to be discharged into the estuary at all states of the tide, but this course of action was not followed. Management of the Drain is the responsibility of the Environment Agency, whereas the numerous rhynes or drainage ditches which feed into the Drain are the responsibility of several Internal Drainage Boards, who work together as the Parrett Consortium of Drainage Boards.