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.
The Levels are a low-lying area around above mean sea level (O.D.) which have been prone to flooding from fresh water and occasional salt water inundations. People have attempted to drain the area for hundreds of years. In the Middle Ages, the monasteries of Glastonbury, Athelney, and Muchelney reclaimed and enclosed much of the land. Drains and artificial rivers have been built and pumping stations installed.
During December 2013 and January 2014 heavy rainfall led to extensive flooding with over 600 houses and of agricultural land, including North Moor, Curry and Hay Moors and Greylake, affected. The villages of Thorney and Muchelney were cut off with many houses flooded. Northmoor Green, which is more commonly known as Moorland, was also severely affected. Flood relief activities included the use of rescue boats and the army. High volume pumps were brought in from the Netherlands and installed at several points to try to relieve the flooding.
There were demands for ongoing dredging of the main rivers, although hydrology experts agreed that this would not significantly help the problem of flooding. Prince Charles and several senior politicians visited the area and controversy arose about the role of the Environment Agency. Better farming and development practices, and some drainage works, were recommended to reduce flood risks in the area.
Geography.
The Levels occupy an area of about , bisected by the Polden Hills; the areas to the south are drained by the River Parrett, and the areas to the north by the rivers Axe and Brue. The Somerset Levels consist of marine clay "levels" along the coast, and inland (often peat-based) "moors"; agriculturally, about 70 percent is used as grassland and the rest is arable. Willow and teazel are grown commercially and peat is extracted. The Levels are about above mean sea level (O.D.). The general elevation of water is O.D. The area's topography consists of two basins mainly surrounded by hills, the runoff from which forms rivers that originally meandered across the plain but have now been controlled by embanking and "clyses" (the local name for a sluice).
Although underlain by much older Triassic age formations that protrude to form what would once have been islands—such as Athelney, Brent Knoll, Burrow Mump and Glastonbury Tor—the lowland landscape was formed only during the last 10,000 years, following the end of the last ice age. Although sea level changes since the Pliocene led to changes in sea level and the laying down of vegetation, the peak of the peat formation took place in swamp conditions around 6,000 years ago, although in some areas it continued into medieval times.
It is a mainly agricultural region, typically with open fields of permanent grass surrounded by ditches with willow trees. Access to individual areas of the Moors and Levels, especially for cattle, was provided by means of "droves", i.e. green lanes, leading off the public highways. Some of the old roads, in contrast to the old hollow ways found in other areas of England, are causeways raised above the level of the surrounding land, with a drainage ditch running along each side. As a result of the wetland nature of the Moors and Levels, the area contains a rich biodiversity of national and international importance. It supports a great variety of plant and bird species and is an important feeding ground for birds. The Levels and Moors include 32 Sites of Special Scientific Interest, of which 12 are also Special Protection Areas. The area has been extensively studied for its biodiversity and heritage, and has a growing tourism industry.
High-risk development and high-risk farming practices.
In 2011, within Sedgemoor District, there were 5,400 properties in significant flood risk areas, 11% of the total. Furthermore, almost 900 of these high-risk properties had been built since 2011, a rate of development nearly three times higher than lower-risk areas of the Levels.
Farming practices have changed in ways that worsen problems with runoff. Around 70% of deep peat in the Somerset Levels and Moors is likely to be losing carbon due to intensive livestock grazing, cultivation and direct extraction. Maize cultivation has increased, and most soils under maize were damaged to the extent that rainfall is unable to penetrate the upper soil layers, resulting in silt-laden runoff.
History of flood defence.
The area is prone to winter floods of fresh water and occasional salt water inundations. The worst in recorded history was the Bristol Channel floods of 1607, which resulted in the drowning of an estimated 2,000 or more people in this and other areas; houses and villages swept away; an estimated of farmland inundated; and livestock killed. Maximum tidal heights are about a metre higher than 1607, due to a combination of postglacial rebound (0.6m), global sea level rise (0.2m) and other factors including localised peat shrinkage (0.2m). Another severe flood occurred in 1872–1873, when over were underwater from October to March.
Early attempts to control the water levels were possibly made by the Romans, but were not widespread. The "Domesday Book" recorded that drainage of the higher grounds was under way, although the moors at Wedmoor were said to be useless. In the Middle Ages, the monasteries of Glastonbury, Athelney, and Muchelney were responsible for much of the drainage. In 1129, the Abbot of Glastonbury was recorded as inspecting enclosed land at Lympsham. Efforts to control flooding on the Parrett were recorded around the same date. In 1234, were reclaimed near Westonzoyland and, from the accounts in the abbey's rent books, this had increased to by 1240.
Drains.
Flooding of adjacent moor land was partially addressed during the 13th century by the construction of a number of embankment walls to contain the Parrett. They included Southlake Wall, Burrow Wall, and Lake Wall. The River Tone was also diverted by the Abbot of Athelney and other land owners into a new embanked channel, joining the River Parrett upstream from its original confluence. The main drainage outlets flowing through the Moors and Levels are the rivers Axe, Brue, Huntspill, Parrett, Tone, and Yeo, together with the King's Sedgemoor Drain, an artificial channel into which the River Cary now runs. Previously, the Cary ran into the Tone while the Brue ran through Meare Pool (now drained) and the Panborough Gap, and then into the Axe. Another accomplishment in the Middle Ages was the construction of the tidal Pillrow Cut, joining the Brue and Axe. In 1500, there was said to be of floodable land of which only had been reclaimed. In 1597, of land were recovered near the Parrett estuary; a few years later, near Pawlett were recovered by means of embankments; and three further reclamations, totaling , had been undertaken downstream of Bridgwater by 1660.
In the early 17th century, during the time of King James I, abortive plans were made to drain and enclose much of Sedgemoor, which the local Lords supported but opposed by the Commoners who would have lost grazing rights. In 1632, Charles I sold the Crown's interest in the scheme, and it was taken over by a consortium that included Sir Cornelius Vermuyden, a Dutch drainage engineer. However, the work was delayed by the English Civil War and later defeated in parliament after local opposition. In 1638, it was reported that nearly of Tealham and Tadham Moors were not reclaimed, with a total of being undrained. Between 1785 and 1791, much of the lowest part of the peat moors was enclosed. In 1795, John Billingsley advocated enclosure and the digging of rhynes (a local name for drainage channels, pronounced "reens" in the east and rhyne to the west) between plots, and wrote in his "Agriculture of the County of Somerset" that had been enclosed in the last 20 years in Wedmore and Meare, at Nyland, at Blackford, at Mark, in Shapwick, and at Westhay. At Westhay Moor in the early 19th century, it was shown how peat bogs could be successfully drained and top-dressed with silt deposited via flooding, creating a very rich soil. The character of the soil was also changed by the spreading of clay and silt from the digging of King's Sedgemoor Drain.
The man-made Huntspill River was constructed during World War II with sluices at both ends to provide a guaranteed daily supply of of "process water". It was intended that in the summer, when water supply was lower, it would serve as a reservoir with water pumped from the moors; and in winter serve as a drainage channel, via gravity drainage. Geotechnical problems prevented it from being dug as deep as originally intended and so gravity-drainage of the moors was not possible: thus, water is pumped up into the river throughout the year. The Sowy River between the River Parrett and King's Sedgemoor Drain was completed in 1972. The Levels and Moors are now artificially drained by a network of rhynes which are pumped up into "drains". Water levels are managed by the Levels internal drainage boards (IDBs); the Levels are not as intensively drained or farmed as the East Anglian fens, historically a similar area of low marsh. One of the approaches to reducing the risk of flooding within the catchment area of the Parrett is the planting of new woodlands.
Since 1990, the drainage boards have been charged with watching the rhynes and keeping them clear, under the overall responsibility of the Environment Agency. Although the Environment Agency have made plans for the regular winter flooding, still in recent years this has resulted in a number of villages — including Langport, Muchelney and Westonzoyland — being cut off. In November 2012, during the 2012 Great Britain and Ireland floods, after six days Somerset County Council-funded BARB rescue boats reached Muchelney on 29 November, rescuing nearly 100 people.
Controversy about the management of the drainage and flood protection has previously involved the activities of IDBs. However, IDBs have been actively participating with the Parrett Catchment Partnership, a partnership of 30 organisations that aims to create a consensus on how water is to be managed, in particular, looking at new ways to achieve sustainable benefits for all local stakeholders.
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 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. The scheme is also used to encourage water birds.
The Environment Agency's current "Parrett Catchment Flood Management Plan", published in December 2009, divides the Parrett catchment area into eight sub-areas, with the Somerset Levels and Moors falling into sub-area 6 and Bridgwater falling into sub-area 7. As part of the published flood risk assessments for both these sub-areas, it is recognised that: at a future date a tidal clyse may be needed on the Parrett; this causes a funding dilemma; and, geomorphology studies of the Parrett and the Tone are needed to help address many of the uncertainties associated with a tidal exclusion project.
Pumps.
Little attempt was made during the 17th and 18th centuries to pump water, possibly because the coal-driven Newcomen steam engines would have been uneconomical. It is not clear why windmills were not employed, as they were on the Fens of East Anglia, but only two examples have been recorded on the Levels: one at Bleadon at the mouth of the River Axe, where a sea wall had been built, and the other at Common Moor north of Glastonbury, which was being drained following a private act of Parliament in 1721, the Glastonbury Inclosure Act 1721 (8 Geo. 1. c. "16" Pr.). The first steam pumping station was Westonzoyland Pumping Station in 1830, followed by more effective ones from 1860. Automatic electric pumps are used today.
Rainfall.
Along with the rest of South West England the Somerset Levels have a temperate climate, which is generally wetter and milder than the rest