Historic Landscapes and the 2010 Flood and Water Management Act

Posted on September 6th, 2011 by Charles Boot

Conference at Deer Park Hall, Pershore, Worcestershire on Tuesday 21 June 2011

report by Steffie Shields

The Reservoirs Act 1975, ensuring the safety of UK reservoirs, is being updated by the Flood and Water Management Act 2010, England and Wales. Haycock Associates liaised with English Heritage and other key organisations to host a conference for interested groups to share experiences of implementing these changes, where costs may be significant, and to summarise challenging requirements of the new Flood and Water Management Act for historic landscapes whilst maintaining a sensitive approach to management.

Professor Andy Hughes, Director of Dams & Water Resources, Atkins; Panel Engineer, Advisor to DEFRA, began the day with a historical perspective (see www.barrages-cfbr for his paper Reservoir Safety in the UK). The first reference to reservoir safety in the UK appeared in the Waterworks Clauses Act of 1863, where anyone who was concerned about reservoir safety could complain to two Justices of the Peace who would then investigate the issue and organize repairs/action. Then in 1925 three failures caused loss of life. On Monday 20 April 1925, heavy rain caused Skelmorlie reservoir dam to overtop, killing a woman and four children. On 2 November 1925, a cascade failure caused the death of 16 persons in Dalgarrog village, North Wales, when two dams failed, after poor quality construction. This led to the Reservoirs (Safety Provisions) Act 1930, applying to all reservoirs containing more than 5 million gallons and subject to inspection by an independent engineer. There was a responsibility under common law for accumulating water and filth, but no powers to enforce the Act or compel the owner to carry out works required in the interests of safety. The Reservoirs Act 1975 brought in the formation of a supervising Enforcement Authority nested in more than 136 different authorities, with the provision of a Supervising Engineer for each dam with a capacity of 25,000m3 to inspect the dam usually twice a year. The first formal Register was made. Every year since 1975, there have been three or four incidents of dam failure, though no loss of life. A guide ‘Floods and Reservoir Safety: An Engineering Guide’ (1978, updated 1989 and 1996) suggested standards and categorised dams in terms of the potential hazard to life and property downstream:

• Category A dams: where a community (10 or more people) are at risk.

• Category B dams: where inhabitants of isolated houses are at risk or where extensive damage would be caused (i.e. erosion of soils, severing a main road or rail communications).

• Category C dams: situations where there is negligible risk to human life, flood-threatened areas that are ‘inhabited’ only spasmodically e.g. footpaths etc and loss of livestock and crops.

• Category D dams: usually small dams where additional damage caused by the release of water may be insignificant if lake is small, where stored water would add no more than 10% to the volume or peak of the flood.

The 2003 Water Act called for better record keeping of ‘flood-plans’; inundation mapping, velocity and depth of water, on-site and off-site emergency planning. 136 different enforcement authorities were replaced with a single enforcement authority, the Environment Agency and Crown immunity was removed.

The Flood and Water Management Act 2010 includes more small reservoirs and cascades with a 10,000m3 threshold and will provide more monitoring, better maintenance, a risk-based-approach to protect persons and property against the escape of water. Statutory Inspections will have the force of law. Recommendations may be challenged at the report stage with a referee procedure. Owners will be given three years to resolve problems. Many historic water features previously exempt from regulation will now have to meet statutory standards and will be subject to inspection; those which pose a low risk to people and property downstream may be deregulated.

The choice of pragmatic and flexible engineers will be key for owners, so as to build and maintain stable level-crested, smooth dams with working valves, appropriate spillways, and ensure no trees in wrong positions, care with machinery, grass cut and no overgrown vegetation so that dams may be inspected. The advice is be safe, be legal, be sure.

Simon Rundle, Principal Counsel for Reservoirs, Environment Agency, continued the theme, pointing out that the average age of reservoirs is 110 years. Owners will be enforced to register. In Phase 1,

April 2012, every reservoir will be assessed, probably in three categories, high, medium and low risk, with necessary measures to be taken ‘as soon as practicable’. Phase 2, Oct 2013/2014 will require the registration of new large reservoirs and flood maps for those from 10,000m3 to 25,000m3. High-risk reservoirs will require a supervising engineer to make a statement of compliance on maintenance. Post incident reporting will become a legal requirement, and will enable the sharing of knowledge with owners/undertakers/lessees of ornamental lakes. In cases of dual, or even several ownership regarding upstream face, and downstream face, and road, or even different local authority areas, it will be a matter of negotiation on a case-by-case basis. Safety is paramount. Criminal charges may be brought for an offence of strict liability.

Andy Wimble, Regional Landscape Architect EH, considers approximately 13% of registered parks and gardens could be affected by this 2010 legislation. He endorsed the need for flexibility and pragmatism regarding issues of extreme weather and ground saturation, de-silting of lakes, die-back in trees, and warned of the cumulative effect of managing a chain of lakes or abandoned water features. ‘Heritage at Risk’ Funding is being extended to landscapes at risk. There are design issues such as the use of ‘riprap’ (loose stone construction) to counter rising water tables. Warning that landscapes are vulnerable to failure to understand the character and key components, he emphasised both the need to mitigate highly inappropriate, over-engineered solutions and the importance of dialogue, case studies and data gathering to help both an understanding of the history of features and how lakes are being used. Case studies included Bretton Country Park, EH Grade II, (home to Yorkshire Sculpture Park) restoration of the lakes created by damming the River Dearne; Plumpton Rocks, EH Grade II*, to retrieve the picturesque landscape as depicted in Turner’s c.1798 paintings; Alnwick Castle Estates looking at using hydro-power from cascades on the River Aln.

Wrest Park Old Park lake dam by Capability Brown newly restored by EH. By courtesy of the author

Wrest Park Old Park lake dam by Capability Brown newly restored by EH. By courtesy of the author

David Thackray, Head of Archaeology, National Trust, has been working on their policy publication Source to Sea. 5% of NT land and 2,000 buildings are at risk, with 120 NT properties at Flash Flood Risk. Slope is an issue, as is erosion, episodes of high rainfall and climate change. NT is looking at slowing the speed of water moving downstream, using land to absorb and store water. With coast erosion and sea level rises, nine coastal historic parks and gardens are in the flood risk zone. The restoration of the Stourhead dam is an example of good practice regarding hydrological, archaeological and biodiversity aspects. In Studley Royal water garden artificial islands caused by previous dredging have now been removed. At Woodchester, Gloucestershire, a chain of five lakes poses a serious health and safety risk to the Stroud valley community. Dense forestry creates a problem, casting deep shade on the lakes. Viewpoints have been obscured. The 25-year NT plan aims to take out the forestry and return the land to grazing. Some serious, austere engineering, including enlarging spillways, has followed appropriate historical research and design intentions to ensure water resource conservation in planning.

Dominic Cole, Principal Landscape Architect, Land Use Consultants, Chairman of the GHS, agreed that the brutal engineering at Woodchester works, because the sides of the valley are planted up. Water features placed on tops or on sides of hills cause problems; for example the scale and visual illusion at Prior Park with small ponds in a geologically unstable area of Bath. At Wardour Castle, Richard Woods’ dams had collapsed when trying to implement Lancelot Brown’s lake proposals. A fascinating plan of the contours of the Stowe landscape showed great amounts of earth-moving and excavated soil deposited, when Brown had problems sourcing water and failed to create a lake in the Grecian valley.

Nick Haycock, Director of Consulting, Haycock Associates, focused on hydrological perspectives, the challenges of catchment risks, and modifying catchment behaviour. Should we use smart hydrometrics to reduce reservoir management risk, or find softer solutions? He spoke of eleven water bodies on the 600-acre Hampstead Heath, the impact of people, and the problems of compaction and sorptivity, with some areas like concrete. Crisp, clear water is an aspiration. The badly silted lake at Croome was dredged, keeping the weir and original penstock systems. The need was for sympathetic solutions, particularly with a heronry on the island, the reduction of pollution and nitrogen because of significant wetlands and, with ground water seeping down the valley, alternating flow and run-off. He discussed warning systems, such as the rain radar now monitoring the weather on Hampstead Heath, and rain gauges and water-level recorders to trigger an alarm system.

Steve Capel-Davies, Partner & Past-Chair, Peter Brett Associates, concluded with a key case-study, Blenheim, having been involved for 8 years working with EH, Natural England and the Environment Agency where Vanbrugh built ’a monstrous bridge over a vast hollow’ (Thomas Whateley) and Brown dammed the modest river Glyme to create the Great Lake, 7½ million m3 of impounded water in a World Heritage Site. In 2007, a tractor made a hole in Brown’s underground spillway beside the dam. The cascade, with 7 to 8 metres drop, was also leaking. They cut down the plane trees below the dam and dug a 1m wide trench to remove eroded and breached sections of the dam, replacing the 600 mm core by back filling with bentonite (a form of clay) slurry (or cement made of hydrated aluminosilicate minerals, comprised chiefly of montmorillonite). Instead of underground, they built a serpentine armour-lock spillway as a path where vegetation will take root. 12,000 cubic metres of top-soil were imported, wildflowers and grass sewn, and evergreen shrubbery planted. A viewing area for visitors overlooks the Grand Cascade which was grouted, and limestone rocks placed either side to stop leakage. An area below the Swiss Bridge is being addressed that was once wetlands according to a 1920’s photograph, and also the river–lake, embanked and densely wooded all the way to Brown’s brick Lince Bridge and another 4-metre drop cascade.

New work on the cascade of  Lancelot Brown's dam at Blenheim Palace, World Heritage SIte. Photo by Sally Stradling

New work on the cascade of Lancelot Brown's dam at Blenheim Palace, World Heritage Site. Photo by Sally Stradling

A view in the opposite direction along Brown's Blenheim dam. Photo by Sally Stradling

A view in the opposite direction along Brown's Blenheim dam. Photo by Sally Stradling

Conclusion. A worthwhile day explaining the implementation of the 2010 Flood and Water Management Act, adding much to a gathering wisdom re hydro-projects in historic landscapes. Haycock Associates’ posters in the conference room: “Putting water first creates habitat for lives” and “Thinking big to solve problems at source” would seem to suggest a positive way forward for owners of historic landscapes, which will need to be individually addressed, carefully, sensitively, case by case. Personally speaking, I am concerned that Blenheim’s engineering solutions have set a precedent that may radically affect sense of place.

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