SC080048 - Scoping Study - Modes of Dam Failure and Monitoring and Measuring Techniques

Theme:Sustainable Asset Management
Project status:Completed
Start date:05/11/2008
End date:30/09/2011
Contact:

PROJECT SUMMARY

In 2009, Defra produced a strategy for reservoir safety research and development. This identified a number of areas for research projects, which would draw together best practice, operational experience and recent developments in the management of existing dams in the UK. The Environment Agency’s new report provides the findings from a scoping study into two of the areas of research identified in the strategy. These are ‘modes of failure of dams and failure of monitoring techniques’ and ‘monitoring and measuring methods for embankment dams’.

The aim of the scoping study was to find out how much information is available to the reservoir industry on these two topics and whether or not there are any gaps in knowledge. The report will be used to help the Environment Agency decide which areas of research it should focus on in the future. In particular, the work will feed into a project on risk assessment of reservoirs, which started in 2010.

We found that to understand fully the modes of failure it is necessary to understand all the potential hazards to a dam. Forty-eight hazards are defined in the report, ranging from rapid drawdown of the reservoir to overflow failure. A summary of existing research is provided for each of the hazards and gaps in knowledge are identified.

Many of the hazards are covered by existing publications, a number of which need to be updated. Some modifications are required to the research projects identified in the Defra strategy and some new research projects are proposed. A few of the new projects could be implemented relatively quickly, as they will only require the production of a ‘Reservoir Technical Guidance Note’ using existing information:

  • surface erosion;
  • upstream membranes, and concrete and asphaltic facing;
  • crest fissuring;
  • controlled holding of water at a low level.

We also examined methods to monitor and measure embankment dams, as well as general monitoring techniques used on all dams. The methods are generally well documented in the publications:

  • Investigating embankment dams: a guide to the identification and repair of defects.
  • Building Research Establishment Report BR 303 (1996); and

An engineering guide to the safety of embankment dams in the United Kingdom. Second Edition. Building Research Establishment Report BR 363 (1999).

 

However, many monitoring techniques are implemented without a full understanding of their capabilities and purpose and they are not always able to detect failure in advance of an incident. Furthermore, for some techniques the reservoir community requires further guidance, such as seepage monitoring, leakage detection and remote sensing techniques [for example, light detection and ranging (LiDAR), aerial photographs and satellite imagery].

The scoping study on these two research topics concludes that some further research projects are required. Projects of highest priority recommended in the report are:

  • Reservoirs and ecological hazards: a best-practice guide to the management of animals and vegetation;
  • Reservoir safety: a checklist for surveillance;
  • Modes of failure of dams – trial risk assessment.

Projects of medium-to-high priority recommended in the report are:

  • Monitoring techniques for different indicators;
  • Risk management of reservoirs – a best-practice guide;
  • Reservoir engineering design to Eurocodes: draft guide for consultation.

A number of other areas that require research and guidance are identified as lower priority.

It is not possible to confirm at this time which, if any, of these recommendations will be taken forward.

 

The study was carried out in consultation with individuals from the reservoir industry, including reservoir owners, managers, supervising engineers, all reservoir panel engineers, consultants, academics and representatives from the Environment Agency. It will help the Environment Agency to understand the needs of the industry for guidance in the future. An added benefit is the definition of hazards and modes of failure, which can be used in the upcoming project on risk assessment of reservoirs.