Climate Risk Assessment for United Kingdom's "High Speed Two" Rail Network

The UK Government's proposed design for a new high speed railway between London and points north considered climate change-related risks, including flooding of tracks and overheating in tunnels. The risk assessment report discusses how those risks will be addressed in the proposed design for the project. The proposed project, High Speed Two (HS2), is designed to link eight of Britain’s ten largest cities and increase the capacity of the country’s rail infrastructure. The project is expected to cost 16 billion British pounds, with service to start in 2026.

High Speed Two Limited (HS2L), the public body responsible for project planning and delivery, conducted a high-level climate change risk and resilience assessment in order to identify climate-related hazards and propose resiliency measures. The findings of that assessment were published in 2013 as Volume 5 of the London-West Midlands Environmental Statement (ES). The ES uses UK Climate Projections from 2009 (UKCP09) to identify climate risks to HS2 infrastructure and assets. The two highest priority risks were flooding of track work, cuttings, and tunnels, and overheating in tunnels. The ES identified design measures to reduce these risks, including elevating the openings of ventilation shafts and portals and increasing the size of tunnels to allow for ventilation and cooling.

The risk assessment was intentionally high level. Therefore, HS2L did not apply a specific climate change scenario nor did they undertake a quantitative assessment of climate change projections. The ES uses broad descriptions of long-term changes provided by UKCP09 to qualitatively assess the effects of climate change on the proposed project. The ES considers climate impacts during the construction and operational lifetime of the project for which projections are available (2017-2099). UKCP09 projects warmer, drier summers; milder, wetter winters; an increase in annual average temperatures; more very hot days; more intense precipitation events; and more dry spells.

In addition to identifying climate impacts, the ES proposes design measures to reduce vulnerability to those impacts. In order to reduce flood risks, the design includes 1 meter of freeboard above the level associated with the 0.1% annual probability of flooding. In addition, railway drainage will be designed to accommodate storms associated with the 0.1% annual probability of flooding plus an additional 30% drainage capacity to allow for climate changes. In order to reduce the risk of overheating of trains within tunnels, the ES recommends the provision of adequate space within tunnels and shafts to accommodate future cooling needs. In addition, the ES cites the use of regenerative braking technology on trains as a way to reduce waste heat emissions in tunnels as well as reduce the carbon impact of rail operations.

The assessment of climate risks associated with the HS2 project provides an example of how the effects of climate change can be assessed and minimized in the development of rail transportation networks.

The development of HS2 will be a long-term project, and planning and construction will advance separately through two phases. As of March 2016, the UK government is in the process of advancing a Bill through Parliament to proceed with Phase One of the HS2 project; the Bill will grant powers to construct and maintain the portion of the railway from London to the West Midlands (Birmingham). Construction on Phase One is expected to start in 2017 Phase Two of HS2, which will run in a Y-shape from the West Midlands to Leeds and to Manchester, is still in earlier planning and study phases. The exact alignment for all of Phase Two has not yet been proposed, as the government is continuing to evaluate options and expects to announce a proposed route in fall of 2016. The government anticipates depositing a separate Bill in Parliament for Phase Two of HS2 in 2017. HS2 is expected to be operational as a network fully integrated with the rest of the UK rail network in approximately 2033, although Phase One and portions of Phase Two will likely open earlier.

This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on March 21, 2016.


Publication Date: November 2013


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Resource Types:

  • Assessment
  • Case study
  • Policy analysis/recommendations


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