King's Sedgemoor Drain
King's Sedgemoor Drain | |
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Location | |
Country | England |
State | Somerset |
Region | Somerset Levels |
Physical characteristics | |
Source | River Cary |
• location | Henley Corner, Somerset, England |
• coordinates | 51°05′26″N 2°48′28″W / 51.09056°N 2.80778°W |
Mouth | River Parrett |
• location | Dunball, Somerset, England |
• coordinates | 51°09′42″N 2°59′19″W / 51.16167°N 2.98861°W |
King's Sedgemoor Drain is an artificial drainage channel which diverts the River Cary in Somerset, England along the southern flank of the Polden Hills, to discharge into the River Parrett at Dunball near Bridgwater. As the name suggests, the channel is used to help drain the peat moors of King's Sedgemoor. There was opposition to drainage schemes from the local inhabitants, who feared that they would lose their common grazing rights. However, the main channel was constructed between 1791 and 1795, and despite some defects, brought some relief from flooding to the area.
The drain was upgraded during the
Background
The area through which the drain runs was farmed as common land when it was owned by the
King's Sedgemoor was described by Arthur Young in his travelogue of 1771. It was generally flooded, and the water had "no way to get off but by evaporation." Although he felt that its condition was a disgrace to the Nation, he was also convinced that it could be improved by drainage. Drainage schemes were promoted in 1772, 1776 and 1788, and Richard Locke published a map showing what might be achieved in the 1780s. All this came to nothing, as the commoners and some of the manorial lords resisted the plans, while there was well-documented fraud among those proposing the schemes. The 1776 scheme was in reality an attempt by Lord Bolinbroke to raise money to settle a gambling debt.
Construction
Sedgmoor Drainage Act 1791 | |
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Act of Parliament | |
Dates | |
Royal assent | 13 May 1791 |
The Sedgmoor Drainage Act 1791 (
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The 10.5-mile (16.9 km) channel of the King's Sedgemoor Drain was completed in 1795, running from the River Cary at Henley Corner to Dunball, to divert the River Cary around the south-western edge of the Polden Hills. The engineer for the scheme was Robert Anstice, who lived in Bridgwater and went on to become the first county surveyor for Somerset.[7] Problems were experienced with new foundations for the sluice at Dunball, which was built on ground which had until 1677 been a meander in the river. White's plans had proposed running the channel further downstream to Nine Streams Reach, but this had been opposed by landowners, and so the clyse was built at Dunball. The unsuitable conditions at Dunball resulted in the clyse being built about 4 feet (1.2 m) too high, and the shallower gradient caused sedimentation in the channels. Earth banks, built from the spoil, caused the underlying peat to rise up in the centre of the drain. A timber floor in the drain was built to restrict this, but the recurrent problem of the peat rising up was not finally solved until the banks were moved further back and in many cases, spread over the adjoining fields.[8]
The scheme included a number of new bridges, with the main ones being at Crandon, Bawdrip, Parchey and Greylake. Penning sluices were fitted to the bridges at Bawdrip and Greylake, to allow the water to be used for irrigation, but in many cases, the bridge openings were too small, with the result that water stacked up behind them in flood conditions. In addition to the main channel, which increased in width from 26.5 to 55 feet (8.1 to 16.8 m) as it approached Dunball, the "Eighteen Feet Rhyne" was built to drain the moor to the north of Henley Corner, and rhynes at Aller, Chedzoy, Shapwick and Street were also 18 feet (5.5 m) wide. Other rhynes were 15 feet (4.6 m) wide.[8] When the scheme was finished, it had cost over £32,000. £15,000 of the total had been spent on engineering work, and the scheme resulted in improvements to the drainage of an area of 11,000 acres (4,500 ha).[4]
Maintenance
The next 140 years were marked by an inability to take action on the part of those responsible for the maintenance of the drainage scheme. Once completed, it came under the jurisdiction of the Commissioners of Sewers, and routine maintenance did not take place. In 1811, the commissioners pinned their hopes on the proposed Bristol to Taunton canal, which would have crossed the drain by an aqueduct, which would have included a new clyse at a lower level than the Dunball outlet, but the canal project came to nothing. The banks continued to slip, and the peat continued to rise up in the bottom of the drain. They asked Robert Anstice to produce a report on the condition of the drain in 1816, but it was 1818 before the report was produced and highlighted the poor state of repair of the system. They also asked for a report on ways to make the bridges wider, but nothing came of it. Ten years later, they commissioned another report, but the local landowners took matters into their own hands and asked Josiah Easton to inspect the drain.[9]
Easton reported that the drain was now nearly useless, and that £10,000 would be needed to put it back into good order. In 1829, he published a proposal to improve the drain so that it would be navigable from Dunball to Yeovil. Drainage required the water levels to be lower, but navigation required them to be higher, and so the scheme came to nothing. The commissioners scoured the drain, but no real progress was made. In 1842, another report was commissioned, from a Mr. Glyn. His two alternatives were to lower the clyse at Dunball by 4 feet (1.2 m), and to convert the lower part of the channel into a reservoir. Steam engines would be used to pump water into it, and it would empty by gravity at low tide. The Commissioners were unsure whether their powers allowed them to start such work, so they did nothing. In 1844, with the clyse doors in imminent danger of collapse, they paid for the cill to be lowered by 20 inches (51 cm) and fitted new doors, but the moors still flooded during most winters.[10]
The commissioners were replaced following the passing of the
Modern era
The passing of the
As part of the war effort, an explosives factory,
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.[7] 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.[16] 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,[17] which allow water level management to be controlled in a more flexible manner.[18]
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.[19]
Wildlife
In mid-2008, an eel-pass was installed at Greylake Sluice, consisting of an open-topped metal channel, fitted with bristles on its base, which allows glass eels returning from the Sargasso Sea to wiggle their way past the sluice. The channel is equipped with an infra-red camera, to allow the movement of eels to be monitored during the night. The installation, together with a similar one at Oath lock on the River Parrett, has provided valuable information on the migration and decline of eels.[20] The Drain is well stocked with fish, and was used, together with the Huntspill River, as the location for the Division 1 National Fishing Championships in 2008.[21]
At Greylake the
Water Quality
The Environment Agency measure water quality of the river systems in England. Each is given an overall ecological status, which may be one of five levels: high, good, moderate, poor and bad. There are several components that are used to determine this, including biological status, which looks at the quantity and varieties of
The water quality of the King's Sedgemoor Drain was as follows in 2019.
Section | Ecological Status | Chemical Status | Length | Catchment | Channel |
---|---|---|---|---|---|
King's Sedgemoor Drain - Henley Sluice to mouth[24] | Moderate | Fail | 17.3 miles (27.8 km) | 44.63 square miles (115.6 km2) | artificial |
The data includes the Sowy River from the point at which it leaves the River Parrett. Like many rivers in the UK, the chemical status changed from good to fail in 2019, due to the presence of polybrominated diphenyl ethers (PBDE) and mercury compounds, neither of which had previously been included in the assessment.
Route
In Roman times the course of the River Parrett near Puriton was quite different from that of today. It followed part of the route of the present day King's Sedgemoor Drain, forming almost a great loop along the southern flank of the Polden Hills.[25]
The Drain starts at a narrow sluice at Henley Corner, near
Westonzoyland village is a little further to the west, near where the
Point | Coordinates (Links to map resources) |
OS Grid Ref | Notes |
---|---|---|---|
Dunball Clyce | 51°09′40″N 2°59′17″W / 51.161°N 2.988°W | ST309407 | Junction with River Parrett |
Sowy River Junction | 51°06′43″N 2°53′17″W / 51.112°N 2.888°W | ST379351 | River Parret flood channel |
Greylake Sluice | 51°06′22″N 2°51′47″W / 51.106°N 2.863°W | ST396344 | |
Henley Corner | 51°05′24″N 2°48′29″W / 51.090°N 2.808°W | ST435327 | Junction with River Cary |
Bibliography
- Billingsley, John (1798). General View of the Agriculture of the County of Somerset. R. Cruttwell.
- Dunning, Robert, ed. (2004). "A History of the County of Somerset: Volume 8: The Poldens and the Levels". British History Online. Retrieved 24 January 2009.
- Gathercole, Clare (1998). "Down End". English Heritage Extensive Urban Survey. South West Heritage Trust. Archived from the original on 8 February 2021.
- East, Gordon (February 1937). "Land Utilization in England at the End of the Eighteenth Century". The Geographical Journal. 89 (2). Blackwell Publishing on behalf of The Royal Geographical Society (with the Institute of British Geographers): 156–172. JSTOR 1786126.
- Otter, R. A. (1994). Civil Engineering Heritage: Southern England. Thomas Telford. ISBN 978-0-7277-1971-3.
- Skempton, Sir Alec; et al. (2002). A Biographical Dictionary of Civil Engineers in Great Britain and Ireland: 1500 to 1830. Thomas Telford Publishers. ISBN 978-0-7277-2939-2.
- ISBN 978-0-521-07486-5.
References
- ^ Dunning 2004, pp. 1–7
- ^ Williams 1970, pp. 145–146
- ^ Williams 1970, pp. 146–147
- ^ a b c Skempton 2002, pp. 776–777
- ^ Billingsley 1798
- ^ East 1937, pp. 156–172
- ^ a b Otter 1994, p. 94
- ^ a b Williams 1970, pp. 147–150
- ^ Williams 1970, pp. 218–219
- ^ Williams 1970, pp. 219–220
- ^ Williams 1970, pp. 220–221
- ^ Williams 1970, pp. 234–235
- ^ Williams 1970, pp. 237–238
- ^ Williams 1970, pp. 238–240
- ^ Panel for Historical Engineering Works, Newsletter. Institute of Civil Engineers. March 2006. p. 6.
- ^ "Newsletter" (PDF). May Gurney. Winter 2006. p. 6. Archived from the original (PDF) on 1 October 2011. Retrieved 16 November 2010.
- ^ "Bespoke Design Case Study - Greylake Sluice" (PDF). Aquatic Control Engineering. p. 5. Archived from the original (PDF) on 3 September 2011. Retrieved 16 November 2010.
- ^ "Written Answers, 22 July 2008 : Column 1012W". House of Commons, Hansard. Retrieved 16 November 2010.
- ISBN 1-85705-788-0. Archived from the original(PDF) on 19 March 2009. Retrieved 16 November 2010.
- ^ "Groundbreaking project saves glass eels". BBC Somerset. Archived from the original on 1 April 2017. Retrieved 16 November 2010.
- ^ "Division 1 National". Bridgwater Angling Association. Archived from the original on 2 January 2009. Retrieved 16 November 2010.
- ^ "About Greylake". RSPB. Archived from the original on 24 September 2020. Retrieved 16 November 2010.
- ^ "Glossary (see Biological quality element; Chemical status; and Ecological status)". Catchment Data Explorer. Environment Agency. Retrieved 17 May 2017.
- ^ "King's Sedgemoor Drain - Henley Sluice to mouth". Catchment Data Explorer. Environment Agency.
- ^ Gathercole 1998.
- ^ "Westonzoyland Airfield". Somerset Historic Environment Record. Somerset County Council. Retrieved 16 November 2010.
- ^ "Greylake SSSI citation" (PDF). Natural England. Archived (PDF) from the original on 8 February 2021. Retrieved 16 November 2010.
- ^ "Battle of Sedgemoor". UK Battlefields Resource Centre. Archived from the original on 24 May 2020. Retrieved 27 January 2009.
- ^ Ordnance Survey, 1:25,000 map
External links
Media related to King's Sedgemoor Drain at Wikimedia Commons