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The dams project at Prior Park Landscape Garden

New trees in the foreground with established garden and the Palladian Bridge behind, Prior Park, Bath
New trees by the lower lake at Prior Park | © National Trust / Ruth Newell

Things have been a bit different at Prior Park in Bath recently, with the 18th-century dams having undergone an exciting, yet crucial, restoration project. It’s part of our ongoing aim to restore the garden to its 1764 state, at the time of creator Ralph Allen’s death, while also protecting the dams for the future. Here's all you need to know about the dams project and what it means for Prior Park.

What is happening?

Since we started caring for Prior Park Landscape Garden in 1993, the aim has been to restore the Georgian garden to how it looked in 1764, when its creator Ralph Allen died.

As part of this wider restoration, the recent project was working on restoring the dams at the lower end of the garden. Built in the mid-18th century, both time and the destructive American signal crayfish had taken their toll and the dams required expert attention to make them fit for the 21st century.

Now, in autumn 2022, we have started the replanting phase of the project. Over the coming months we'll plant nearly 4,000 trees, shrubs and ferns to populate the new shrubberies created as part of the dams project. The main construction work was completed at the end of spring 2022 when the lakes were refilled and the paths were opened around the lakes once again.

Work on the middle lake and dam

Before the project got under way, the middle lake stood empty for a few years in order to relieve the pressure on its damaged dam. While time has impacted the lakes’ condition, some pesky intruders have also caused significant damage: the American signal crayfish.

The American crustaceans’ persistent burrowing contributed to the instability of the bank. In fact, paths had to be closed when the banks’ deterioration led to sinkholes.

American signal crayfish found in the lakes at Prior Park, Bath
American signal crayfish, Prior Park | © National Trust/Rachel Beaumont

Much of the work on the middle lake focussed on protecting the dam and its banks from these unwanted guests. Better defence systems against their burrowing have been built into the banks and their long term impact will be controlled through the creation of a management plan to control numbers. The original 18th-century wall that lines the upstream face of the dam has also been repaired and extended, to help prevent the crayfish burrowing into the dam itself.

Work on the lower lake and dam

Another important aspect of the dams project was future-proofing the lower dam by improving the dam's infrastructure and capability, as well as re-profiling the lakes damaged banks.

Expert engineers and architects carefully considered how the lower dam should be re-designed to increase its water outlet capacity, in order to ensure that the dam would effectively manage an extreme weather event. Yet whilst modern thinking and advancement in engineering is central to the restoration of the dam, the project team has ensured that visually, the new design is in keeping with its 18th-century origins.

What happened at the lower lake

Before the works began, the lower lake was drained. Similarly to the middle lake, the banks of the lower lake had been deteriorating and gradually slipping into the lake. In fact, the banks had become so steep that some areas had to be roped off.

Stabilising the east bank created a more authentic sweeping lawn down to the water’s edge and opens up more of the garden to visitors.

To help restore the beautiful landscape seen in Thomas Robbins' 1762 sketch, the lower lake will see the weed reduced by an amphibious machine during the winter, to restore the reflections on the surface.

Although some trees needed to be removed to enable construction vehicles to access the lake area, the trees lost have been replaced with trees and shrubs that are more authentic and in keeping with the 18th-century style.

What the project involved

The project involved deconstructing the middle dam and adding a new clay core faced with stone, as well as maintaining the existing section of upstream face wall and building a new wall where there were gaps.

Timber edging has been added on the downstream face and the improved dam reprofiled, meaning it can safely overtop if faced with extreme flooding while retaining its historic integrity.

Similarly, the lower dam was upgraded to cope with extreme flooding. The works also restored the historic cascade between the middle and lower lakes so that it flows freely once again.

Archaeology team working on the Cascade at Prior Park, Bath
Archaeology team working on the Cascade at Prior Park, Bath | © National Trust Images/Dawn Biggs

Frequently asked questions

What impact will there be on visitors during the work?

As we enter the planting phase of the project, the garden is fully open to visitors who can access the lakes, dams and paths once more. There might be some small sections of the path closed around the lower lakes to allow for the gardening work from time to time.

Will the Tea Shed be closed?

We've installed a temporary Tea Shed in the Cabinet, at the top of the garden. This tranquil part of the garden is the ideal spot to enjoy tea and cake. The Tea Shed is open weekends and school holidays (Wed-Sun).

Can I still use the lower gate?

The lower gate is now open again for exit only. Unfortunately we are not able to offer entrance through this route at the moment.

How long will the work take?

Planting will be ongoing throughout the autumn and winter. The main phases of the works took around two and a half years, due to delays as a result of the Coronavirus pandemic and severe weather.

A view of the valley parkland with the Palladian Bridge, and beyond to the skyline of Bath, at Prior Park, Bath


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