Fens, the

Level, low-lying tracts of reclaimed marsh in eastern England, west and south of the Wash, covering an area of around 40,000 sq km/15,500 sq mi, about 115 km/70 mi north–south and 55 km/34 mi east–west. They fall within the counties of Lincolnshire, Cambridgeshire, and Norfolk. Formerly a bay of the North Sea, they are now crossed by numerous drainage canals and form some of the most fertile and productive agricultural land in Britain. The southern peat portion of the Fens is known as the Bedford Level.

The first drainage attempts were made by the Romans. After the Norman Conquest an earthwork 100 km/60 mi long was constructed as a barrage against the sea. In 1634 the 4th Earl of Bedford commissioned the Dutch water-engineer Cornelius Vermuyden to drain the Bedford Level, introducing Dutch drainage methods to the Fens.

Features The main rivers flowing through the area are the Great Ouse, Witham, Welland, and Nene, and many small watercourses also intersect the area. Before the present system of drainage was developed, the whole district was waterlogged and consisted of marshy swamps, wide pools, and lagoons. Woad continues to be grown in some areas for its blue dye. There are a number of windmills, now mostly disused, on the flats. The area is noted for its bulb fields, especially around Spalding.

Ecology Northeast of Cambridge, attempts have been made to preserve the raised bogs of Burwell Fen and Wicken Fen undrained as nature reserves, but agriculture in the surrounding area has affected water levels, partially destroying their ecology. Areas such as Lopham Fen and Redgrave Fen are also recognized as having important ecological value for specific animal and plant life, including otters, great raft spiders, rare birds, and the marsh hellibore orchid, although their existence is considerably threatened by land drainage and groundwater draw-down for public supplies. Wildfowl and fish remain abundant in the rivers and marshlands, but ecological problems have been caused by the introduction of fish species such as the zander, a voracious predator.

History The region was once the home of the ancient Iceni, who were led in revolt against the Romans by Queen Boudicca. The Romans dug drainage channels, the Caer or Car Dykes from Lincoln to Ramsey, and constructed earthen embankments along the Welland and the seashore, some stretches of which can still be seen. Following an unsuccessful attempt to drain Deeping Fen during the reign of William (I) the Conqueror, the district was abandoned, although the forest portions were preserved between the 12th and 14th centuries as royal hunting areas.

Small communities, known as fen slodgers, enclosed and embanked portions of the land to create islands with fields and pasture, gathering reed for thatching, and living on wildfowl and fish. The drainage of the land in the 15th and 16th centuries threatened their way of life, and local opposition was expressed by attempts to break down the newly created banks and dams. However, vast areas were systematically drained in the 17th century by the great landowners, using the Dutch methods introduced by Cornelius Vermuyden, and though flooding was still occurring, by the 18th century the way of life of the fen slodgers had almost disappeared. Drainage of the Fens continued during the 18th century and many pumping windmills were installed. In the 19th century steam pumps were introduced, and the land was successfully drained; these were replaced by diesel and electric pumps. Wicken Fen remains undrained.

Religious communities The isolated areas of higher ground above the surrounding levels were occupied by cells and monastic establishments as early as the 7th century. Until the time of the Dissolution of the Monasteries, the religious houses at Peterborough, Ely, Crowland, Ramsey, Thorney, and elsewhere succeeded in draining and cultivating some of the land in the vicinity of their communities.

Flooding and flood protection Frequent flooding has been caused when high spring tides occur at the same time as rivers are swollen with water drained off the land. Sluices, closed at high tide, are used to keep sea water from entering the rivers, but they also prevent the outflow from escaping. The consequent piling up of fresh water strains the river banks to breaking point. Following severe flooding along much of the English coast in March 1947, a large-scale flood protection scheme for the Fens was established in 1954 by the Great Ouse River Board. An intercepting channel around the edge of the Fens was constructed from Barton Mills in Suffolk to Denver in Norfolk, the river from Denver to the mouth of the Cam was widened and deepened, and a relief channel was built to carry the flood water direct to an outfall at King's Lynn. The scheme was completed in 1963. A tunnel was also developed to convey water from the Ouse above Downham Sluice to the River Stour, from where it is taken to augment local supplies in Essex.