River Parrett - Flood Prevention

Flood Prevention

The waters of the Severn Estuary, which are heavily laden with silt, flow into the lower reaches of the Parrett and the Tone on each tide. This silt can rapidly gather on the banks of the rivers reducing the capacity and performance of the channel, and increasing the risk of flooding of surrounding land.

The river is technically a highland carrier, as it is embanked and the water level is often higher than that of the land through which it flows. Water from the surrounding countryside does not therefore drain into the river naturally, and drainage schemes have relied on pumping to remove the water. The pumping station at Westonzoyland was built in 1830, the first mechanical pumping station on the Somerset Levels. It was designed to drain the area around Westonzoyland, Middlezoy and Othery, and the success of the drainage system led to the formation of Internal drainage boards and the construction of other pumping stations.

The pump at Westonzoyland originally comprised a beam engine and scoop wheel, which is similar to a water wheel, except that it is driven round by the engine and lifts water up to a higher level. After 25 years, there were problems pumping the water away as the land surface had dropped as it dried out. A better method was sought, and in 1861 a replacement pump was installed. The engine was built by Easton and Amos of London, to a design patented in 1858 by Charles Amos. It is a twin cylinder, vertical condensing engine, driving a centrifugal pump. A similar engine was on display at the Great Exhibition of 1851 and was shown to be able to lift 100 tons of water per minute (1,700 L/s), to a height of 6 feet (1.8 m). The Westonzoyland pump lifts water from the rhyne (pronounced "reen") into the River Parrett. The pump operated until 1951, when a new diesel-powered pumping station, capable of pumping 35 tons per minute (600 L/s) at any state of the tide, was built beside the old one. The pumping station is now an Industrial Heritage museum of steam powered machinery and land drainage, and houses most of the equipment from the disused Burrowbridge pumping station.

The Somerset River Authority was established in the 1960s, and later became part of Wessex Water. Tidal models were used to explore the relationship between any improvement to the river to reduce the likelihood of flooding and subsequent silting reducing the effects. Engineering works were undertaken at the Parrett, King's Sedgemoor Drain, and River Brue systems, in an attempt to ensure that agricultural land benefited from a potable water supply in the groundwaters from the Quantock Hills to the coastline.

Various measures including sluice gates, or clyce, have been deployed to try and control flooding. Completed in 1972, the Sowy River is a 7.5-mile (12.1 km) embanked channel which starts at Monks Leaze clyce below Langport, and carries excess water from the river to the Kings Sedgemoor Drain, from where it flows to the estuary by gravity, rejoining the Parrett near Dunball wharf. Construction of the channel, together with improvements to the Kings Sedgemoor Drain and the rebuilding of the clyce at Dunball, to create a fresh water seal which prevents salt water entering the drain from the river, cost £1.4 million. The scheme has resulted in less flooding on Aller Moor.

In the 1970s a study was commissioned by Wessex Water to investigate the likely effects of constructing a tide-excluding barrier, aimed at stopping the silt, just upriver of Dunball Wharf on the hydraulic, sedimentary and pollutant regime of the estuary. Results showed that a site further upriver could be viable.

The area around the estuary, known as Parrett Reach, around the Steart Peninsula has flooded many times during the last millennium. As a result, the Environment Agency, a non-departmental public body of the UK government's Department for Environment, Food and Rural Affairs, produced the Stolford to Combwich Coastal Defence Strategy Study in 2002, to examine options for the future. In July 2010 the Environment Agency presented plans to convert the peninsula into wetland habitat, if the proposed scheme goes ahead it will be the largest wetland habitat creation scheme in England.

Following summer floods of 1997 and the prolonged flooding of 1999/2000 the Parrett Catchment Project was formed, partly funded by the European Union Regional Development Fund, by 30 organisations, including; British Waterways, Campaign to Protect Rural England, The Countryside Agency, Department for Environment, Food and Rural Affairs, Environment Agency, Kings Sedgemoor and Cary Vale Internal Drainage Board (now part of Parrett Internal Drainage Board), Levels and Moors Partnership, National Farmers Union, Sedgemoor, Somerset County Council, South Somerset District Council, Taunton Deane and Wessex Water. They aim to tackle 12 areas, which, when combined, will make a significant contribution to reducing the adverse effects of flooding. These include the conversion of arable land, adoption of the Sustainable Drainage Systems (SuDS) approach to controlling rainwater runoff from developed areas, dredging, raising riverbanks and improving pumping facilities. Further studies of the possible beneficial effects of woodland in reducing flooding have also been undertaken.