Hampstead Heath Ponds Project - City of London
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    Hampstead Heath, Men's Bathing Pond

    ​Sunset at the Men's Bathing Pond

Following advice from a government appointed panel engineer, the City carried out works on two chains of ponds on Hampstead Heath. This work was mitigated by important ecological improvements and ensuring the dams on Hampstead Heath can withstand extreme rainfall events.

Construction work on the Ponds Project was started in April 2015 and concluded in October 2016.​​

​Now that the construction period is over, there is a restoration period as grass and plants become established and the areas which were work compounds recover.

Why did the project take place?

Hampstead Heath is fortunate in having about 30 beautiful and much-loved ponds. Although they look natural, most are formed by man-made dams which are up to 300 years old. Three of the ponds are large enough to be classed as 'large raised reservoirs' under the Reservoir Act 1975, which means they are subject to a statutory inspection regime by a government appointed panel engineer.

Keeping North London safe from dam collapse

The City of London Corporation is responsible for ensuring that the pond dams on Hampstead Heath are safe. We were advised that we needed to take action to minimize the risk to life, property and infrastructure in North London, especially in Dartmouth Park, Gospel Oak and Kentish Town. The works have made the dams safe while minimising the impact on the natural environment of the Heath.

Protecting and enhancing the Heath

The design took into full account the need to preserve the Heath's landscape and habitat. We used the opportunity to make enhancements, including new paths, viewpoints and reed-beds. A team of landscape architects, ecologists and hydrologists worked alongside engineers to ensure that the works would improve water quality and biodiversity.

Watch the Ponds Project

See our dam-building time-lapse video below and watch the Ponds Project unfold.

​Further information

If you'd like more information on the Ponds Project, please contact us.


For a detailed timeline of the Ponds Project, please see below.


  • 14 August 1975 - A historic convective storm occurred over north London (170 mm over a three hour period recorded close to the Heath). Whilst there is evidence that a considerable amount fell as hail, it resulted in significant flooding and damage to two dams. Whilst Hampstead No. 1 held, the park manager was so concerned about Highgate No. 1 that he opened the valve releasing water into the surface water systems, which may have contributed to flooding downstream but stopped the dam from overtopping and potentially failing. The centre of the storm was situated west of the Heath. Other rainfall events have since caused overtopping of dams including one in early August 2002 and another smaller event in May 2010.

2006 - 2007

  • In 2006 specialist hydrologists Haycock associates were appointed to undertake a water quality and hydrological catchment assessment. Their investigation reviewed the hydrological functioning of the various lake chains around Hampstead Heath and provided recommendations for their management. The study identified issues with compaction and absorption of water. It was the first study to look in depth at the four water catchment areas that exist across the Heath and immediate environs of the site.
  • 2007 - A series of destructive floods occurred in various areas across the country during the summer of 2007. The worst hit areas were East Yorkshire, The Midlands, Yorkshire, Gloucestershire, Herefordshire, Worcestershire Oxfordshire, Berkshire and South Wales.
  • July 2007 – the Inspecting Engineer undertook a ten year statutory inspection on the three statutory reservoirs on the Heath, the resulting report stated that the overflow capacity on all the reservoirs was inadequate and recommended an assessment of the downstream impact and risk of breach be carried out.
  • On 8 August 2007 - Sir Michael Pitt was appointed by the Secretary of State for the Environment, Food and Rural Affairs to chair an independent review into the 2007 floods. His final report was published in June 2008 and the Government  began introducing new responsibilities for reservoir owners – under the Flood and Water Management Act 2010 (“the 2010 Act”).

2009 - 2010

  • 2009 – Following the recommendation in the 2007 inspection, the City of London Corporation (“the City”) commissioned their then Supervising Engineer, CARES Ltd, to undertake a Flood Risk Study for the three reservoirs, as well as Swan Pond on the Golders Hill Chain.  This concluded that the Hampstead No. 1 and Highgate No. 1 Ponds fell into the highest risk category and Swan Pond had a broadly acceptable risk of failure (due to the lower consequences of dam breach at this pond).  The report recommended further modelling of the effect of the pond chains, and improvement work to the ponds.
  • 2010 – The City commissioned Haycocks Associates to undertake a review of the hydrology and hydraulics of the dams within Hampstead Heath. The aim of the study was to determine the current operation of these structures and their compliance with reservoir legislation. Under changes to the 1975 Act set out in the 2010 Act (not yet brought into force) the minimum size of a large raised reservoir will be reduced to 10,000 cubic metres. It is anticipated that the new regulations will also provide for all ponds in a chain that have a combined volume of 10,000 cubic metres to be classed as large raised reservoirs, which would include all of the ponds in the Hampstead and Highgate chain. It is also anticipated that these ponds will be assessed as high-risk reservoirs – the new designation for large raised reservoirs that are subject to the most rigorous safety and inspection regime.
  • 2010 – The City appoints new Supervising Engineer, Dr Andy Hughes.


  • 2011 – Haycock’s report, reviewed by the Panel Engineer and published in April 2011, identified the probable maximum flow and the implications arising from it. The report, published in January 2011 said that the “spillway’’ (or capacity for controlled overflow) is inadequate and presents a risk. Based on the findings of this study, it was considered that the three existing large raised reservoirs are inadequate to meet the current requirements of the 1975 Act.  The report included concept ideas so that the reservoirs and ponds on both the Hampstead and Highgate chain of ponds comply with the existing and emerging reservoir legislation whilst also complying with the requirements of the Hampstead Heath Act 1871. This work included draft visualisations and provision of estimated capital costs. Given the deficiencies identified with the dam structures the Supervising Engineer advised the City Corporation that works would be required to ensure compliance with the Reservoirs Act. Failure to proceed on a timescale considered reasonable by the Supervising Engineer could result in a further statutory inspection and enforcement action by the Environment Agency to implement works within prescribed timeframe (normally two to three years).
  • January 2011 – Information about the proposed works was posted on the City’s website.
  • January 2011 – Evening Standard,  Camden New Journal and Ham & High run stories leading on risk to human life if dams are not improved.
  • April 2011 – Initial meetings with local residents and interested parties began.  A workshop was held that brought together Heath users, local groups and residents and City staff. This started a detailed dialogue that is planned to inform and consult Heath users and local people throughout the project. The outcome of the April workshop can be found on the website. The Heath and Hampstead Society and the Swimmers forum also met to discuss plans with officers from the City.
  • July 2011 - The City approved an Evaluation Report setting out the broad scope of works (circa £15M) to comply with  existing and emerging reservoir legislation while also considering  the Hampstead Heath Act 1871 and to improve water quality. Officers were instructed to commence production of a Detailed Design Report, taking the project to a position where a planning application could be submitted to the Local Planning Authority. In considering the need to meet public safety, whilst reconciling the works so that they fit with the character of the Heath, the City has approved an outline scheme that upgrades all of the ponds. This approach (as opposed to one which only focussed on the three existing large raised reservoirs) was selected as it mitigates against the risk of dam failure at any of the ponds. It also reduces the visual impact of the works in any one place by spreading the impact across all of the ponds. It avoids works being carried out on the three large raised reservoirs that would become redundant in future, and ensures full compliance once the 2010 Act is in full force, avoiding the need for further works at that time.
  • September 2011 – Officers propose the creation of a Flood Management and Water Quality Stakeholders Group. This group is to be made up of interested parties and will act as a conduit between the Hampstead Heath Consultative Committee and the City, feeding information to and from each to the other.
  • October 2011 – Lord Smith, Chairman of Environment Agency, speaking at a Committee dinner advised that the last statutory inspection of dams in 2007 had not included any recommendations to undertake any works to the dams and that the City were being pro-active in undertaking works. The Camden New Journal reported this as there now being no legal requirement for the proposed works.
  • October 2011 – Dr Andy Hughes responds to Lord Smith’s comments by saying work on the dams is necessary to protect against inevitable flooding, and the 2007 inspection did call for further studies – the Haycock report. Those studies have revealed that if a further statutory inspection were called, there would be Recommendations made in the Interests of Safety.
  • December 2011 – Leaflet: ‘Why work is needed’ produced by City.


  • January 2012 - Heath and Hampstead Society raise questions about the basis of the Institute of Civil Engineers evidence and methodology for the risk assessment in their Newsletter. The Society holds a meeting for its membership to discuss the project.
  • January 2012 – The City seeks further legal advice from a leading QC on the project.
  • February 2012 – Environment Agency commences the Flood and Water Management Act 2010 Schedule 4 (Reservoirs) Consultation on the Environment Agency’s approach to designating large raised reservoirs as high risk.
  • March 2012 – An invitation to tender for the different elements of the Design Team is sent by the City. This includes the landscaping, ecology, architectural elements associated with the project.  Negotiations commence for the engineering design with WS Atkins Ltd.
  • April 2012 - The Department for Environment, Food and Rural Affairs (Defra) have published a consultation on the Implementation of Amendments to the 1975 Act which closes on 17 May 2012.  The consultation considers a number of changes to the 1975 Act including reducing the threshold at which a water body is considered a large raised reservoir from 25,000 cubic metres to 10,000 cubic metres.
  • May 2012 – Response given to Defra particularly in relation to cascades and also criminal liabilities.
  • May 2012 – Meeting held on site with Members of Camden Council’s Environment Scrutiny Committee to consider the implications of the project.
  • June 2012 – Heavy rain cause flooding in Wales and South of England. In Wales a village of 600 people is evacuated when a slight breach appears in a reservoir dam. A controlled release of water prevents dam from failing and people are allowed to return home.
  • July 2012 – The Ponds Project Stakeholder Group meets for the first time. This group, comprising of 13 members includes representation from key interest and community groups and will meet regularly to discuss the project and provide advice and views to help influence the design and implementation of the scheme. The group is chaired independently of the City of London.
  • August 2012 – The appointment process of a Strategic Landscape Architect begins. This individual will perform a unique role to defend the landscape of the Heath throughout the duration of the project. Appointed by the City of London, they will work closely with local stakeholders and act as a conduit between them and the designers on the development of the proposed scheme. The Ponds Project Stakeholder Group have involvement in the appointment. As well as championing the landscape and contributing knowledge to the design thinking, the Strategic Landscape Architect will work independently of the Design Team and challenge, if necessary, any engineering solution that fails to respect the natural aspect of the Heath.
  • September 2012 – City of London begins informal consultation process with a series of ‘pop-up’ consultations taking place at various locations on the Heath. This is to both gauge public opinion and to spread information on the project.
  • October 2012 – Peter Wilder from Wilder Associates is appointed as Strategic Landscape Architect. Two companies are appointed to the Design Team: W.S Atkins will manage engineering, planning, landscape and ecology and Capita Symonds will act as the cost consultants and client representatives.
  • December 2012– Atkins produce a Design Review Method Statement with input from the Ponds Project Stakeholder Group and the Hampstead Heath Consultative Committee and approval from the Hampstead Heath Management Committee. This Statement sets out the next steps of the project, the first of which is a review of the hydrological data that forms the foundation of the project by the Design Team, led by Atkins. In parallel to this the Design Team review the environmental constraints for the Heath.


  • January and February 2013- The Ponds Project Stakeholder Group attend a workshop with the Strategic Landscape Architect to list the opportunities and thre​ats at each pond. Hampstead Heath staff repeat this exercise and all of the information gathered at both workshops is given to the Design Team. Meanwhile the public are asked for their initial views about what needs to be protected during the project and any enhancements they would like to see. The Strategic Landscape Architect produces a Critical Review to capture the consultation which has taken place.
  • March through to May 2013- The Design Team deliver their first major piece of work - a complete review of all of the hydrological data which forms the basis for the project. The results of this are described in the Design Flood Assessment and in a shorter and less technical form in the Design Flood Assessment Summary report. The Design Team found that using more refined modeling techniques provided a more accurate set of data and hence a clearer picture of the risk of potential flooding. Their results indicate that the scale of potential flooding in the worst case is significantly lower than the largest flood modeled by previous hydrologists. The Ponds Project Stakeholder Group and the Hampstead Heath Consultative Committee are briefed on this study and ask supplementary questions which are answered by the Design Team before it gains approval from the Hampstead Heath Management Committee on 9 May 2013.
  • June 2013 - the Design Team produced a Constrained Options Report and Appendices which details the process they went through in combining constraints, identified by the Ponds Project Stakeholder Group and the public, with engineering principals.
  • July and August 2013 - the Design Team produce a Shortlist Options Report. Various options, including the size of proposed new embankments on the Highgate and Hampstead pond chains, are explored in this report. The Stakeholder Group and the public comment on this report - a summary of their comments is attached to the report as Appendix C and the full comments are placed on the Shortlist Options Report.
  • August 2013 - Following a request from Stakeholders, the City agreed to produce a Quantitative Risk Assessment (QRA) to aid understanding of the baseline risks of dam failure for the two chains of ponds on Hampstead Heath. The QRA demonstrates a potential for loss of life in the event of dam failure which ranges from five people to over 1400 people. A position paper by Dr Andy Hughes is produced to read in conjunction with the QRA.
  • October 2013 - The Preferred Options Report is published by the Design Team. In this report,
    Design consultants, Atkins, look in more detail at two options on each chain of ponds and the trade-offs between the different heights of dams and the work required elsewhere on the chain. This report will form the basis of the non-statutory public consultation which will take place from the end of November until mid-February.
  • November 2013 - A non-statutory information sharing and consultation exercise commences. The public are invited to find out more about the project and fill in a questionnaire about the option they prefer.
  • December 2013 - Information signs are placed on the Heath, in close proximity to the ponds with detailed information on the proposals. Two exhibition displays, open daily until 17 February 2014, are located at Parliament Hill staff yard (near the cafe) and East Heath car park.


  • ​January/February 2014 - The City continues to give information and consult upon the latest proposals.
  • March - The Consultation results are published in a Summary Document and in the Full Report
  • June 2014 - The Preferred Solution Report is published. This report puts forward the case for the preferred solution for each chain of ponds and gives updates on refinements to the design following environmental reviews and the results of the Information Giving and Public Consultation. This report was heard by the Hampstead Heath Consultative Committee on 2 June 2014 and the Hampstead Heath, Queens Park and Highgate Wood Management Committee on 9 June 2014.
  • July 2014 - A planning application is submitted to Camden Council.
  • July 2014 - The Heath and Hampstead Society writes to the City with a letter before claim - the first stage in the Judicial Review process. The City responded on 28 July 2014.
  • October 2014 - The Design Team issue the Materials and Finishes Design Update which finalises the remaining outstanding design elements.
  • November 2014 - The Heath and Hampstead Society's Judicial Review is heard before Lady Justice Lang at the Royal Courts of Justice. On 28 November, Lady Justice Lang handed down her judgment. She rejected the Heath & Hampstead Society’s case that the City of London Corporation’s decision was unlawful and irrational, and refused the Society permission to appeal.




  • January 2015 - At Camden Council's Development Control Committee on Thursday 15 January, planning permission for the Ponds Project was granted subject to conditions and a Section 106 agreement.​
  • February 2015 - As part of the planning conditions, a Community Working Group is set up. This group, made up of ward councillors, residents associations, Heath societies and Heath users, will meet monthly for the duration of the project and will look at the impacts of the construction work.
  • April 2015 - work starts on site. The first big piece of work is to set up the compound on the western hillside next to Model Boating Pond and to install vehicle passing bays on the path between Parliament Hill and Model Boating Pond.
  • May 2015 - work commences at Viaduct Pond. At this location a spillway is created and an additional overflow pipe is added close to the existing overflow. The dam is raised by 20 cm and resurfaced.
  • June 2015 - top soil is stripped from the borrow pits on the hillside next to Model Boating Pond and work building the temporary sheet-pile dam commences.
  • July 2015 - work starts at Hampstead No. 2 and Hampstead No. 1. The first piece of work here is to create an outlet structure in the top corner of Hampstead No. 1.
  • August 2015 - Work on the Vale of Health pond commences. At this pond a spillway is created and a kerb installed to raise the dam. The path is also resurfaced.
  • September 2015 - Viaduct and Vale of Heath pond are completed.
  • Issues with the temporary dam cause delays at Model Boating Pond.
  • October 2015 - work commences on Stock Pond and at Ladies Pond.
  • December 2015 - work commences on Hampstead No. 1 Pond.


  • ​January 2016 - the work compound at Model Boating Pond is extended to be used for silt storage.
  • February 2016 - work begins at the Catchpit and the Ladies Pond building is demolished.
  • March 2016 - work starts at Mixed Pond.
  • April 2016 - Stock Pond is finished other than turfing.
  • May 2016 - Ladies Pond building reopens for swimming.
  • June 2016 - Hampstead No. 1 pond is completed, other than aquatic planting which has been delayed due to birds nesting in the vicinity.
  • June 2016: Work starts at Men's Pond and at Highgate No. 1 Pond.
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