Lake dam walls restored at Blickling and Felbrigg estates in Norfolk

The lakes at Blickling Estate and Felbrigg are much-loved features of the landscape. Blickling’s lake was formed in 1729 by damming the Silvergate stream which runs into the River Bure from Pond Meadow. Measuring 2km at its widest point, the lake is teeming with wildlife including carp, pike, reed warblers and great crested grebes. Felbrigg’s lake covers 11 acres and pike, tench, otters, grey wagtails and water rail reed warblers are all regularly in residence. 

2018 survey findings identified issues with the brickworks in the dam walls of both lakes. Last year, a programme of meticulous re-pointing and replacement of failed bricks begun at Felbrigg lake, and this autumn the project has been completed. Similar re-pointing work has been carried out at Blickling lake. This work, undertaken by Dennys Construction, will ensure the longevity and strength of the lake walls and enable them to continue acting as dams, protecting the surrounding land from water seepage. 

Much of the work required at both sites sits below the water level, so temporary cofferdams were required to hold water back with minimal disruption to wildlife in and around the lakes. This required a feat of remarkably effective engineering – the cofferdams consist of modular frames assembled and immersed on the lake beds to enclose the working areas, before plastic membranes are secured to the framework. The working areas are then dewatered using pumps, discharging water into the stream or back into the lake. Hydrostatic pressure creates a freestanding structure to hold water back. 

The conservation work at Blickling had the added complexity of requiring repairs to the sluice-gate mechanism. This helps control the water levels of the lake and prevents unexpected flooding to the surrounding land. With the temporary cofferdam in place, the sluice gate was revealed for the first time.

National Trust Project Manager, Katherine Garwood, explained

“With the water removed, it was incredible to see that the outfall was brickwork and not concrete as we had previously assumed. It also features intricate ironwork detailing – this was completely unexpected, as it was designed to be submerged under the water.”

“We were also excited to discover that the sluice-gate mechanism was not just one single gate, but instead it features two gates, enabling water levels to be lowered from the top surface of the lake as well as from the bottom, depending on the circumstances.”

Blickling’s dedicated volunteer engineers, who have in the past helped to restore a waterwheel and water pumps, used their valuable skills to repair the sluice gate. They refurbished the salvageable parts and worked out what was missing, designing new components so that the sluice could once again be fully operational. Their enthusiasm for the project, along with their extensive knowledge of all things water related at Blickling has been key to the success of the project.

Blickling Estate’s General Manager, Heather Jermy, explained

“Local changes in climate are leading to increased rainfall in short periods, and it’s more important than ever that we can manage water levels across the Blickling Estate. We are grateful for the dedicated work and expertise the volunteer engineers have contributed to this vital restoration project, which has been part-funded by a gift in a will from a former volunteer at Blickling.”

Emily Long, Project Manager, Riverlands – Upper Bure River Valley, added

“Maintaining our ornamental lakes is a much-needed part of our modern waterscape. Whilst not natural in origin, they represent important habitats hosting a range of fish, amphibians, and invertebrates, as well as playing a role in flood management. The lakes at Blickling and Felbrigg bring to life how important water has been to our places throughout history, whether for fishing or unbeatable landscape views. It’s fantastic to undertake works to protect them so they may continue to play a part in making our catchment healthy, clean, and rich in wildlife.”