Sowy River

Last updated

Sowy River
Sowy River.jpg
The Sowy River at Stathe
Location
Country England
State Somerset
Physical characteristics
Source River Parrett
  coordinates 51°02′41″N2°50′38″W / 51.04472°N 2.84389°W / 51.04472; -2.84389
Mouth King's Sedgemoor Drain
  coordinates
51°06′43″N02°53′16″W / 51.11194°N 2.88778°W / 51.11194; -2.88778 Coordinates: 51°06′43″N02°53′16″W / 51.11194°N 2.88778°W / 51.11194; -2.88778
Length12 km (7.5 mi)
Sowy River
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King's Sedgemoor Drain
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Sowy River footbridge
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Langacre Rhyne
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Bimpit Lane Bridge
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A361 Greylake Bridge
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Greylake Farm Bridge
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King's Sedgemoor Drain
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Head Drove Bridge
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A372 Beer Wall Bridge
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Langacre Rhyne
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Aller Drove Bridge
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River Parrett
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Stathe Bridge
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Oath lock and sluice
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Church Drove Bridge
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Oath Bridge
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Middle Moor footbridge
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Combe bridge
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Monks Leaze clyce
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River Parrett

The Sowy River is an artificial drainage channel in Somerset, England, designed to act as a flood relief channel for the River Parrett. Water from the Parrett can be diverted into it just below Langport, and is conveyed to the King's Sedgemoor Drain, which discharges back into the Parrett much nearer to its outfall into the Bristol Channel. Following extensive flooding of the surrounding land in 2014, new culverts to carry the river under the A372 road at Beer Wall were constructed, and a three-year project to raise the banks and widen the channel to increase its capacity was undertaken.

Contents

History

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 Parrett to the King's 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 King's Sedgemoor Drain and the rebuilding of the clyce at Dunball, to create a freshwater seal which prevents saltwater entering the drain from the river, cost £1.4 million. [1] The scheme was first proposed in 1961, following serious flooding in October 1960, when some 78 square miles (200 km2) of the Somerset levels were inundated. A channel with a proposed capacity of 1,060 cubic feet per second (30 m3/s) was proposed, but arguments about the cost of such a scheme resulted in the capacity being lowered to 600 cubic feet per second (17 m3/s). However, the bridges and sluices were either built to cope with the larger flow rates, or made so that they could be easily altered, if funding became available. Construction began in 1969 and was completed in 1972. [2] The scheme resulted in less flooding on Aller Moor. [3]

During 2009 and 2010 work was undertaken to upgrade sluice gates, watercourses and culverts to enable seasonal flooding of Southlake Moor during the winter diverting water from the Sowy River onto the moor. It has the capacity to hold 1.2 million cubic metres as part of a scheme by the Parrett Internal Drainage Board to restore ten floodplains in Somerset. In spring the water is drained away to enable the land to be used as pasture during the summer. [4] The scheme is also used to encourage water birds. In January 2010, when bird numbers were at their peak, some 4,000 wigeon, lapwing and teal were recorded on the moor, while other species sighted included Bewick's swan, pintail, shoveler, golden plover and gadwall. [5]

In January 2014, the A372 road at Beer Wall flooded, as culverts carrying the Sowy River and Langacre Rhyne were unable to cope with the volume of water. After water levels subsided a little, the road remained closed as pumps were placed on it to drain the surrounding land. The road reopened in March, but was closed again in September as flood prevention work began. [6] A trench was cut through the road to the east of the existing culvert for the Langacre Rhyne, where new culverts were to be constructed. In order to keep the road open during the winter, [7] two temporary bridges were installed, one to carry the road and another for pedestrians. The road bridge, with a span of 52 feet (16 m), was placed in position in just three hours, and remained in use for 26 weeks. [8] Four new culverts were built, each 9.8 by 6.9 feet (3.0 by 2.1 m), two to carry the realigned Langacre Rhyne, and two to carry part of the flow of the Sowy River. The culverts and the reconstruction of the road over the top of them was funded by the Department for Transport, [9] and the road reopened in July 2015. [10]

The next phase of the project was managed by the recently-formed Somerset Rivers Authority, and involved re-routing the Langacre Rhyne and the Sowy River through the new culverts. The work included the construction of foundation slabs for two tilting weirs, and this was funded by the Heart of the South West Local Enterprise Partnership. Beginning in April 2016, the two tilting weirs were built, and a bank to maintain the separation between the Sowy River and the new course of the Langacre Rhyne was constructed. This was the start of a three-year project to increase the capacity of the Sowy River and King's Sedgemoor Drain. [9]

While the Sowy River in theory had a design capacity of 600 cubic feet per second (17 m3/s), in practice this was not achieved, and where required, the right bank was raised by up to 1.6 feet (0.5 m) between Monk’s Leaze Clyce and the A372 at Beer Wall in order to achieve this capacity. The capacity of the channel between Beer Wall and the A361 at Greylake Bridge was increased to 850 cubic feet per second (24 m3/s) by raising both banks by up to 1 foot (0.3 m) in places, and by increasing the width of the channel on the right bank. Between Graylake Bridge and the King's Sedgemoor Drain, similar work was undertaken, but only the left bank needed raising, and widening took place on the right bank. Finally, the capacity of the King's Sedgemoor Drain between the Sowy outfall and Parchey Bridge was increased to 950 cubic feet per second (27 m3/s) by raising of both banks by up to 1.6 feet (0.5 m), and by widening the channel on the right bank. In one place, a backwater was created, up to 20 feet (6 m) wide, leaving an island some 16 feet (5 m) wide between the new channel and the old one. [11] Where widening was carried out, the new channel included a shelf 1 foot (0.3 m) below the normal summer water level, to increase the range of habitats available. [12] The scheme is not expected to completely prevent flooding of Middle Moor and Aller Moor, but the frequency and severity of such flooding is expected to be significantly reduced as a result of the work. [13]

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 invertebrates, angiosperms and fish. Chemical status, which compares the concentrations of various chemicals against known safe concentrations, is rated good or fail. [14]

The Sowy River and the King's Sedgemoor Drain are assessed as a single unit, and water quality was as follows in 2019.

SectionEcological StatusChemical StatusLengthCatchmentChannel
King's Sedgemoor Drain - Henley Sluice to mouth [15] Moderate Fail 17.3 miles (27.8 km)44.63 square miles (115.6 km2)artificial

Like many waterways 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.

Bibliography

Related Research Articles

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The River Parrett flows through the counties of Dorset and Somerset in South West England, from its source in the Thorney Mills springs in the hills around Chedington in Dorset. Flowing northwest through Somerset and the Somerset Levels to its mouth at Burnham-on-Sea, into the Bridgwater Bay nature reserve on the Bristol Channel, the Parrett and its tributaries drain an area of 660 square miles (1,700 km2) – about 50 per cent of Somerset's land area, with a population of 300,000.

Bridgwater and Taunton Canal Canal in south-west England

The Bridgwater and Taunton Canal is a canal in the south-west of England between Bridgwater and Taunton, opened in 1827 and linking the River Tone to the River Parrett. There were a number of abortive schemes to link the Bristol Channel to the English Channel by waterway in the 18th and early 19th centuries. These schemes followed the approximate route eventually taken by the Bridgwater and Taunton Canal, but the canal was instead built as part of a plan to link Bristol to Taunton by waterway.

Somerset Levels Coastal plain and wetland area of Somerset, England

The Somerset Levels are a coastal plain and wetland area of Somerset, England, running south from the Mendips to the Blackdown Hills.

River Huntspill River in Somerset, England

The River Huntspill is an artificial river, in the Somerset Levels, in the Sedgemoor district of Somerset, England. It was built in 1940 to supply process water to ROF Bridgwater, and has resulted in reduced flooding of the lower Brue Valley. Huntspill Sluice at the river's western end, also known as West Huntspill Sluice, separates it from the River Parrett.

River Tone River in Somerset, England

The River Tone is a river in the English county of Somerset. The river is about 33 kilometres (21 mi) long. Its source is at Beverton Pond near Huish Champflower in the Brendon Hills, and is dammed at Clatworthy Reservoir. The reservoir outfall continues through Taunton and Curry and Hay Moors, which are designated as a Site of Special Scientific Interest. Finally, it flows into the River Parrett at Burrowbridge.

River Cary (Somerset) River in Somerset, England

The River Cary is a river in Somerset, England. It is sourced from the Park Pond in Castle Cary and flows towards the southwest.

River Lymn River in Lincolnshire, England

The River Lymn is a river in Lincolnshire, England. It rises in the Wolds on the eastern slope of Castcliffe Hill in Fulletby parish. It flows south-eastwards to the Lincolnshire Marsh, where it becomes known as the Steeping River on the boundary of Great Steeping parish. The main channel is supplemented by the Wainfleet Relief Channel as it passes Wainfleet All Saints, and the relief channel is joined by the old course of the Lymn. Once the two channels rejoin, there are three flood defence structures to protect the region from flooding by the North Sea.

River Brue River in Somerset, England

The River Brue originates in the parish of Brewham in Somerset, England, and reaches the sea some 50 kilometres (31 mi) west at Burnham-on-Sea. It originally took a different route from Glastonbury to the sea, but this was changed by Glastonbury Abbey in the twelfth century. The river provides an important drainage route for water from a low-lying area which is prone to flooding which man has tried to manage through rhynes, canals, artificial rivers and sluices for centuries.

Kings Sedgemoor

King's Sedgemoor is a piece of rich animal habitat and farming land, that forms part of the Somerset Levels and Moors in South West England.

Westonzoyland Human settlement in England

Westonzoyland is a village and civil parish in Somerset, England. It is situated on the Somerset Levels, 4 miles (6.4 km) south east of Bridgwater.

Kings Sedgemoor Drain Artificial drainage channel in Somerset, England

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.

Westonzoyland Pumping Station Museum English industrial heritage museum

The Westonzoyland Pumping Station Museum of Steam Power and Land Drainage is a small industrial heritage museum dedicated to steam powered machinery at Westonzoyland in the English county of Somerset. It is a Grade II* listed building.

Southlake Moor

Southlake Moor is a 196.1 hectare biological Site of Special Scientific Interest near Burrow Mump and Burrowbridge in Somerset, notified in 1985.

West Sedgemoor

West Sedgemoor or West Sedge Moor is an area of the Somerset Levels, in Somerset, England, around 8 miles east of Taunton, which approximately coincides with the West Sedgemoor biological Site of Special Scientific Interest, a 1,016 hectare site notified as an SSSI in 1983. It is a flat, low-lying area of fields and meadows separated by water-filled rhynes and ditches. It is subject to controlled flooding in winter. It is drained by the River Parrett.

Westport Canal

The Westport Canal was built in the late 1830s to link Westport and Langport in Somerset, England. It was part of a larger scheme involving improvements to the River Parrett above Burrow Bridge. Langport is the point at which the River Yeo joins the River Parrett and the intention was to enable trade via the port at Bridgwater. It remained in use until the 1870s, but closed when the Somerset Drainage Commissioners took over control of the River Parrett. Despite a petition against closure by local people, the Commissioners ruled that navigation of the canal must cease due to their interpretation of the Act which gave them control of it, leaving the canal to serve as a drainage channel since 1878.

Othery Human settlement in England

The parish and village of Othery, established in 1515, sits on a detached extension of Sowy island on the Somerset Levels. It is 7 miles (11 km) east of Bridgwater and 4 miles (6 km) north-west of Langport. It borders the hamlets and villages of Pathe, Burrowbridge, Middlezoy, Westonzoyland and Aller, which it meets at Beer Wall. The border with Burrowbridge was defined in 1985, reducing Othery to 553 ha. Many of these borders are defined by ditches and walls created and rearranged, from the 13th century onwards, to drain and channel the waters of the River Cary and the River Parrett as they flooded the low-lying levels on their way to the Bristol Channel.

Winter flooding of 2013–14 on the Somerset Levels Flooding in Somerset, England

From December 2013 onwards the Somerset Levels suffered severe flooding as part of the wider 2013–2014 Atlantic winter storms in Europe and subsequent 2013–2014 United Kingdom winter floods. The Somerset Levels, or the Somerset Levels and Moors as they are less commonly but more correctly known, is a coastal plain and wetland area of central Somerset, in South West England, running south from the Mendip Hills to the Blackdown Hills.

Holderness Drain English water project

Holderness Drain is the main feature of a Land Drainage scheme for the area of Holderness to the east of the River Hull in the East Riding of Yorkshire, England. Construction began in 1764, and several notable civil engineers were involved with the scheme over the years. Despite the high costs of the initial scheme, it was not particularly successful, because of the refusal of the ship owners of Hull to allow an outlet at Marfleet. They insisted that the water be discharged into the River Hull to keep the channel free of silt. Following a period of agricultural depression and the building of new docks in the early 1800s, an outlet at Marfleet was finally authorised in 1832. A high level system still fed upland water to the Hull, but the low level system discharged into the Humber, where levels were considerably lower. Following the success of steam pumping on the Beverley and Barmston Drain, the trustees looked at such a possibility for the Holderness Drain, but the development of the Alexandra Dock in the 1880s and then the King George V Dock in 1913 provided a solution, as the docks were topped up with water pumped from the drain, to lessen the ingress of silt-laden water.

<span class="mw-page-title-main">Eller Beck</span> River in North Yorkshire, England

The Eller Beck is a small river in North Yorkshire, England, that flows through the town of Skipton and is a tributary of the River Aire. Its channel was heavily modified to supply water to mills in the 18th and 19th centuries, and although all the mills have closed, the water now supplies power to the National Grid, generated by a turbine at High Corn Mill. The beck flows through several underground culverts in Skipton that contribute to the flood risk. To alleviate flooding in Skipton town centre, a scheme involving two flood water storage reservoirs was designed and eventually completed in 2017.

References

  1. Otter 1994.
  2. SRA 2021.
  3. "The Parrett Catchment Water Management Strategy Action Plan" (PDF). Environment Agency. 2002. p. 28. ISBN   978-1-85705-788-1. Archived from the original (PDF) on 19 March 2009. Retrieved 28 December 2009.
  4. "Southlake Moor restored to floodplain by drainage board". BBC. 17 January 2011. Retrieved 19 January 2011.
  5. "Southlake Moor Favourable Condition Project Newsletter 2: Autumn 2010" (PDF). Parrett Drainage Board. Archived (PDF) from the original on 2 March 2022. Retrieved 19 January 2011.
  6. "Flood-hit A372 road to re-open with temporary bridge". BBC News. 9 December 2014.
  7. "Flood Schemes at Beer Wall and Muchelney". Somerset County Council. 2014. Archived from the original on 24 September 2021.
  8. "Reconnecting Somerset villages following severe flooding". Mabey Hire. Archived from the original on 22 April 2021.
  9. 1 2 "Concrete culverts installed as Somerset Beer Wall moves into third phase". Environment Analyst. 30 September 2015.
  10. "Beer Wall reopens after completion of flood prevention works". Somerset County Gazette. 20 July 2015. Archived from the original on 31 August 2022.
  11. EA 2020, p. 17.
  12. EA 2020, p. 19.
  13. EA 2020, p. 20.
  14. "Glossary (see Biological quality element; Chemical status; and Ecological status)". Catchment Data Explorer. Environment Agency. Retrieved 17 May 2017.
  15. "King's Sedgemoor Drain - Henley Sluice to mouth". Catchment Data Explorer. Environment Agency.

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