Ely Dry – Essex Wet: the Great Ouse Cut Off Channel

LogosIf you are regularly driving down the A10 between Ely and King’s Lynn, you may well have noticed, between Hilgay and Denver, a large sign next to a stream notifying that you are crossing the Cut Off Channel.

Have you ever wondered, like me, what’s the story of this relatively wide piece of water? Well, search no more, because here we will be lifting some of the mysteries.

Sign along A10, just north of Hilgay, when crossing the cut-off channel. Source: Google maps.

Sign along A10, just north of Hilgay, when crossing the Cut Off Channel. Source: Google maps.

In fact, the below information has been kindly supplied by Chris Holley, a Stretham-based local historian, who for many years has been researching engineering and other fascinating features in the Fen landscape. A few years back he wrote a substantial report just about the Cut Off Channel, from which the below information has been obtained. He provided me with a copy earlier this year, which has helped me to understand the history and functions of this intriguing canal.

Aftermath of the 1947 floods

A detailed study of drainage problems and ongoing flooding incidents in the Fens was carried out after a series of bad floods in 1936, 1937 and again in 1939, the Sir Murdoch MacDonald Report on Flood Protection published in 1940. Investment in flood prevention was, however, delayed by the Second World War. Following the very bad floods of March 1947 the MacDonald report was reactivated.

Vermuyden’s unbuilt solution

Cornelius Vermuyden, portrait, photo credit Valence House Museum. Source: http://www.bbc.co.uk/arts/yourpaintings/paintings/sir-cornelius-vermuyden-15951677-133559

Cornelius Vermuyden, portrait, photo credit Valence House Museum. Source: http://www.bbc.co.uk/arts/yourpaintings/paintings/sir-cornelius-vermuyden-15951677-133559

Despite Vermuyden’s 17th century large-scale drainage works, the Fens failed to remain dry, with bad flooding episodes happening regularly. This was not Vermuyden’s fault, since one of his proposals had simply never been built.  His drainage map, published in 1642, clearly shows a planned catchwater channel to collect flood waters from three rivers to the east of the Fens (the then-called Mildenhall, Brandon and Stoke Rivers) and divert them via a relief channel to north of his planned Denver Sluice.

The 1940 MacDonald report recommended building just such a cut off channel, collecting water from the same three rivers, now named the Lark, Little Ouse and Wissey.

A map from Cornelius Vermuyden, from his 1642 'Discourse Touching the Drayning of the Great Fennes'; Folger Shakespeare Library, Washington DC. Source: http://www.dbnl.org/tekst/_low001200301_01/_low001200301_01_0016.php

A map from Cornelius Vermuyden, from his 1642 ‘Discourse Touching the Drayning of the Great Fennes’; Folger Shakespeare Library, Washington DC. Source: http://www.dbnl.org/tekst/_low001200301_01/_low001200301_01_0016.php. The red arrow indicated Vermuyden’s proposed ‘cut off channel’. Note that north is to the right on this map.

In addition, this report also recommended building a new Relief Channel to take their surplus flood water away from the Fens and up to Kings Lynn, as well as improving the existing Ten Mile and Ely Great Ouse rivers from Denver to south of Ely.  Work on all three flood defence elements started in 1954 and finished ten years later, in 1964.

The Cut Off Channel’s functions

In short, the Cut-off channel was built to serve two functions:

  1. To relieve the River Great Ouse from the threat of rising floodwater
  2. To deliver excess water to reservoirs in Essex
Taken together, the two different uses of the Cut Off Channel serve to both keep Ely dry in winter and keep Essex wet in summer. Water flows northwards to prevent flooding during winter times, and flows southwards in summer times to deliver water in Essex.
Some amazing engineering has gone into ensuring that both functions can be carried out. The channel runs across 35 miles of fenland from Downham Market to Mildenhall, with numerous sluices along the way. The southern part also goes largely underground before arriving in Essex.

Great Ouse Cut Off Channel: northwards flow for Ouse flood protection

Since it is estimated that 40% of flood waters in the Fens come from the three eastern rivers (the Lark, Little Ouse and Wissey), the importance of the cut off channel for flood prevention becomes clear.

map showing cut off channel

Map showing the Cut Off Channel, in relation to the Great Ouse and its tributaries, the Lark, Little Ouse and Wissey. Source: report Chris Holley, 2005.

When the Great Ouse Cut Off Channel is flowing northwards for Ouse Flood Protection, the water flows starts at the Lark Head Sluice on the River Lark at Barton Mills, when the sluice is opened.  There are four weirs to control the water levels during the considerable fall between the Lark at Barton Mills and the Little Ouse at Hockwold.

River Wissey

At Stoke Ferry, the River Wissey flows in an aqueduct over the Cut Off Channel. Image by Chris Holley.

The Cut Off Channel then flows northwards and intersects the River Little Ouse at the Hockwold Sluice at Hockwold, and then intersects the River Wissey at the Wissey Sluice at Stoke Ferry, and thence to Denver Sluice.

Cut off Channel seen from A10, flowing west towards the Denver Sluice. Photo by Chris Holley

Cut off Channel seen from A10, flowing west towards the Denver Sluice. Photo by Chris Holley

At each of these intersections, the Cut Off Channel goes underneath the Little Ouse and Wissey rivers in a siphon or U-tube, and can draw water from the two rivers when the appropriate sluice gates are opened and closed.

The Relief Channel starts at Denver and takes water from the Cut Off Channel through the Impounding Sluice, and/or from the Ely Ouse through the A G Wright Sluice, down to the Tail Sluice at Saddle Bow near Kings Lynn.  The Relief Channel acts as an
additional flood water storage reservoir, which can be evacuated out to sea at
low tide.

Cut Off Channel

Section of the OS map showing where the Cut Off Channel joins other waterways at the Denver Sluice complex. Source: report by Chris Holley.

Denver Complex 2

Close-up of Denver Sluice complex, showing the various waterways coming together at this important node. Source: report by Chris Holley.

Great Ouse Cut Off channel: southwards flow for Ouse-to-Essex water transfer

Essex regularly suffers from droughts in summer. In 1964 it was realised there was insufficient water to support expansion, development and growing consumer demand in south Essex.  In 1968 it was proposed to reverse the flow and use part of the Cut Off Channel to take surplus fresh water southwards from the Great Ouse at Denver Sluice and  deliver it down to existing reservoirs in Essex.

The Ely Ouse To Essex Water Transfer Scheme was completed in 1971, taking water down to Abberton Reservoir 87 miles south, and to Hanningfield Reservoir 90 miles south.  Although existing watercourses are utilised for about two-thirds of the distance, a new tunnel and new pipelines and storage tanks all had to be built.

When the flow of the Cut Off Channel is reversed southwards for Ouse To Essex Water Transfer, water is diverted through the Diversion Sluice at Denver and flows up the Cut Off Channel, through the siphon under the River Wissey at Stoke Ferry, to Blackdyke Intake at Feltwell, between Stoke Ferry and Hockwold.

Black Dyke intake

Representation showing the physical layout of the shaft at Blackdyke Intake, the tunnel, and the uptake shaft at Kennett Pumping Station. Source: report by Chris Holley.

Water is extracted from the Cut Off Channel at Blackdyke Intake, where it plunges 90 feet down a huge shaft into a long tunnel under the hills and under the A11 near Newmarket, to Kennett Pumping Station.  At Kennett, water is pumped 280 feet up to the surface again, then by pipeline under the hills by the A14 to Kirtling Green Outfall and Kirtling Brook, where it joins the River Stour to Wixoe Pumping Station near Haverhill. From Wixoe Pumping Station, water flows by various means to three Essex reservoirs.

Want to know more?

If you would like to know more about the history of and engineering works along the Cut Off Channel, Chris Holley has produced a richly illustrated and detailed 92-page report, titled ‘Ely Dry – Essex Wet: the Great Ouse Cut Off Channel’. You can contact him for more information, or to purchase a copy through chrishcs@btinternet.com

A synopsis of Chris’ report can also be downloaded here: Cut Off Channel Synopsis 2

Interpretation board at the Denver Sluice, explaining the origin and function of the Cut off channel

Interpretation board at the Denver Sluice, explaining the origin and function of the Cut off channel. Image by Chris Holley.

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What is special about the OWLP area?

LogosThe OWLP landscape provides extensive wide views and contains huge skies, while being dominated by rivers, drains and ditches that cut across some of the most productive agricultural land in England. This landscape means different things to different people: some can find it featureless and intimidating whereas others find it exhilarating and value its tranquillity and distinctive lifestyles.

Now we have finalised the boundaries for the Ouse Washes Landscape Partnership scheme and we have a defined area, the following question may need reconsidering: what is it that makes the OWLP area special?

In a previous post, I have set out what came out of workshops held regarding the unique qualities and ‘specialness’ and ‘distinctiveness’ of the OWLP area. As part of further discussions with our key partners, ongoing research and discussions with local community groups, we have been able to refine this information.

This then also fed into the Landscape Conservation Action Plan, a key document we recently submitted as part of our stage 2 bid to the Heritage Lottery Fund. The below word cloud formed part of our ‘Statement of Significance’ and sums up what we believe makes the OWLP area special:

WordItOut-Word-cloud-285478_2

Word cloud, summarising what makes the OWLP area special. Created using http://worditout.com

The OWLP landscape is of important for several reasons:

Internationally protected wildlife and wetlands

At 3,000 ha the Great Ouse Wetland network , which lies fully within the OWLP boundary, is one of the most extensive and most important wetland areas in the UK. It comprises of a network of nature reserves, many of which are owned by nature conservation bodies, including the WWT Welney, RSPB Ouse Washes nature, RSPB Fen Drayton Lakes and RSPB Ouse Fen reserves, with further schemes planned including those to be created by the Environment Agency near Sutton and Coveney. Within the heart of this landscape is the Ouse Washes itself, one of the most important areas of lowland wet grassland in Britain.

The expanding network of reserves form a crucial core area in the proposed Fen-wide ecological connectivity network of wetland habitats, crucial for the survival of many rare and endangered flora and fauna species. The restored wetland areas which incorporate a particular high percentage of lowland meadows and reedbeds provide for a tranquillity not easily found elsewhere.

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Fen Drayton Lakes. Image by Sheils Flynn for OWLP scheme.

Rich Archaeology

The OWLP area is of at least national significance for its repository of well-preserved, often waterlogged archaeological and palaeo-environmental remains. The OWLP area contains 18 Scheduled Ancient Monuments, including the well-preserved Earith Civil War Bulwark and several clusters of prehistoric barrows. The area contains especially rich prehistoric and Roman Period archaeology. The abundance of prehistoric remains in the southern part of the OWLP area demonstrate clear evidence for a major prehistoric ceremonial landscape, extending right across the floor of the Great Ouse valley.

Amazing engineering history

This man-made landscape lies largely below sea level demonstrating man’s amazing efforts in drainage engineering, executed here on a grand scale: with its abundant sluices, banks and dykes the whole landscape can be considered as a civil engineering monument. Human intervention regarding its management is as vital today as it was when, in the 17th century, the Ouse Washes in between the Bedford Rivers were created. The survival of the nationally significant Bedford Level Corporation archival collection, curated for by Cambridgeshire Archives, provides us with a unique insight in the historic developments of the drainage schemes in the area.

Unique Experiments

The landscape has also played host to some amazing social, economic and environmental experiments including the Flat Earth Society using the landscape to prove the earth is disc-shaped, the utopian social living experiment at Colony Farm in Manea in the mid-19th century, and the late 20th century hovertrain experimental track.

 

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