First built in the 1600s, the Ouse Washes is an important flood defence but it needs ongoing maintenance to protect the surrounding land.
Our impact
90M m3
Flood water storage
30km
Reservoir length
487,000
Material tonnage required to complete the project
The Ouse Washes reservoir is a vast construction of more than 30kms. In summer months it is usually dry.
The birds keep coming back, and so must the engineers
Forming the largest area of washland in the UK, work on the Ouse Washes is a long running project.
Washland is grazing pasture that floods in the winter and creates a rich habitat for waterfowl and wading birds.
This winter flooding also provides a vital flood storage reservoir system that protects homes, businesses and prime agricultural land on the Norfolk/Cambridgeshire border.
However, the earth banks that hold the water have to be monitored and maintained, and because of the area’s sensitive habitats, work can only safely take place in the summer months.
The Jackson team got to know the area very well, returning to work for six summer seasons and a further two years on a maintenance contract.
Balancing act: Vehicle movements are restricted to protect wildlife including over-wintering as well as nesting birds.
The flood bank was raised by a metre over a distance of 30km.
Bank and ditch defences
An inspection of the Ouse Washes for the Environment Agency in 2013 recommended measures to address changes to the bank crest level caused by settlement.
It was hardly surprising, given the age of the structure. The reservoir was originally constructed in the seventeenth century under plans laid out by the Dutch engineer and ‘father of the fens’, Sir Cornelius Vermuyden.
The maintenance work required was on a monumental scale, raising the bank by a metre over a distance of 30km.
Supporting structures
In addition to the main work of raising the flood banks, the Jackson team carried out a number of supporting construction and engineering projects.
A new bridge and 100m flood wall was constructed at Welches Dam pumping station along with the installation of of a series of new hides for birdwatchers.
The team also extended a retaining wall at Sutton Gault and installed an temporary flood barrier at Welney.
The Welney Wash Road is a low point along the bank that increases the flood risk to the nearby village. In the past, the community had to rely on sandbags for protection whereas the new system consists of a quickly-erected, reusable barrier that ties into a concrete support wall on each side of the road.
The temporary flood barrier at Welney can be erected quickly if flooding is forecast.
