How the project started
Historic Watercourses in the Redington Frognal Area
Meetings from 2015 (which focussed on the undiscovered headwaters of London rivers, especially those around Hampstead Heath) lead to the Neighbourhood Forum considering a project to map unidentified underground rivers, to form part of the evidence base for a Neighbourhood Plan policy on underground development. Arup was commissioned to research the hydrogeology of the Redington Frognal area and their Mapping Report was completed in April 2016, shown below. There is more on Historic Watercourses and flooding here.
Sub Surface Water Features in the Redington Frognal Area
Source: Arup / RedFrog
The Arup map of RedFrog underground rivers indicates the presence of many historic rivers, such as the Westbourne, East Westbourne, Cannon, Boundary Stream, unnamed rivers, springs, wells and ponds. Of these, one clean stretch of the underground Westbourne is known to remain: clean water runs between Branch Hill and Redington Gardens, where the stream can be heard.
Ponds in the Redington Frognal Area
The Arup map also records that at least 20 ponds had formerly existed in the area. These have since been covered over and, as elsewhere in the country, this has contributed to the catastrophic decline in biodiversity:
With this in mind, Redington Frognal Association applied for grant funding from both the Mayor London’s Greener City Fund and from the City Bridge Trust Enjoying Green Spaces Fund, with the aim of reinstating Branch Hill Pond. The applications were supported by Cllr. Spinella, Heath and Hampstead Society and Hampstead Neighbourhood Forum.
Award of Grant Funding to Redington Frognal Association
Redington Frognal Association applied for grant funding from both the Mayor London’s Greener City Fund and from the City Bridge Trust Enjoying Green Spaces Fund, with the aim of reinstating Branch Hill Pond. The applications were supported by Cllr. Spinella, Heath and Hampstead Society and Hampstead Neighbourhood Forum. Both applications were successful and, in 2018, Redington Frognal Association was awarded grant awards totalling £25,000.
Redington Frognal Association has been working together with the Superintendent of Hampstead Heath, and the funding has been spent on exploratory hydrological scoping work and design. This has been undertaken under the direction of the City of London’s team of Ecologists. Scoping work included the excavation of boreholes to analyse soil samples at thirteen different sites. The soil samples yielded were then laboratory tested for geotechnical and geo-environmental properties.
Area of former pond and window sampling rig, 25 June 2020
Ground investigation and soil sampling at Branch Hill
Wet ground at Branch Hill
Excavation and reinstatement of the former pond will attenuate the water that flows into the culvert beneath Branch Hill, thereby reducing any risk of surface water flooding. The reinstated pond will be a natural wildlife pond, which is expected to attract frogs and dragonflies. The pond will be fenced, inaccessible and unobtrusive. It will be important not to introduce fish, so as not to upset the delicate ecological balance.
The pond will provide a significant benefit for biodiversity and will look much like the No. 1 Pond in the Seven Sisters chain on the Heath Extension.
Planning Application for Reinstated Pond at Branch Hill
The pond received planning consent (2021/4816/P) on 22 December 2021, with excavation following in August 2022. Work on the pond is due to be completed in early 2023.
A Presentation on the Constable’s Pond Project
A pdf is available of the presentation by Jonathan Meares, the Conservation and Trees Manager for Hampstead Heath natural Environment, City of London Corporation, documenting how the Branch Hill Pond project will develop here:
Jonathan Meares – Constable’s Pond project 070222
Dr Adam Broadhead, Water Scientist at Arup, gave a video presentation to RedFrog in February 2022 about the daylighting of lost rivers. This is available here on the Underground Rivers page of the site.
Reinstated Branch Hill Pond, October 2022
Following exploratory works, excavation was completed in August 2022. The photo below shows the development of the pond reinstatement as of October 2022.
Project updates 2023
During 2023, water levels are being closely observed and will continue to be monitored over the dry summer months. The aim is to determine whether the pond is fed from groundwater, which is consistent with the pond as the source of the River Westbourne, or from rainwater.
Plants have been ordered for both the pond and the acid grassland hillside. Planting is scheduled for the wetter autumn months, to optimise their success.
Currently, the pond is being used as a dog wash pond. Neocotinoids, used as parasite treatments and preventatives, are powerful killers not only of bees but also of insect larvae, such as those of mayfly and dragonfly which are important food for birds and bats, among other species.
To preserve the pond for wildlife, it will therefore be necessary to erect fencing.