London scoping - ukcip

7.3.2 Rail Transport
Final Report
155
Context
There exists a dense and extensive network of rail track in and around the Greater London area -
extending across the UK - that supports business, commuter and leisure travel in London.
Stakeholder consultation with sectoral representatives has borne out the general perception that
the rail network is climate sensitive and has vulnerabilities associated with climate change.
These are identified below.
Flooding and Rainfall Intensity Impacts
Clay shrinkage impacts upon structures on which the rail network is reliant, including bridges,
tunnels, embankments and cuttings. Therefore more reinforcement is necessary if an increasing
rate of disruptions is not to be expected. Land-slips may result for the same reason, if higher
winter rainfall intensities lead to increased instability in banking and slopes. A change of this
type has already been noticed in other parts of the UK e.g. South Scotland.
Flooding when drainage systems cannot cope. Water on the rails acts as a conductor for the
electricity in the rails and therefore its presence mimics the presence of a train at that location.
Consequently, the network control systems need to send engineers to such locations in order to
check what is happening. This checking process therefore results in delays to those trains that
are using the track. Bridge scour when high levels of river water, combined with debris, works
at the foundations of bridges. This reduces their stability and requires preventative expenditure.
It also results in disruption to the network when bridges are closed.
Flooding would cause disruption and reduce the mobility of Londoners, and cause knock-on
impacts through out the city. A recent example of the impact on flooding was on the 7 th August
2002 when five of London’s mainline stations were closed due to floods after intensive rainfall.
Travel within the capital, and into and out of the capital, was seriously affected by these floods.
The most vulnerable areas are those which are located in the flood plain of the Thames and its
tributaries (such as the Rivers Lee and Wandle). Areas of flood vulnerability are currently the
subject of targeted investment in flood mitigation schemes. High risk flood areas, such as those
associated with surface water drainage failure and shallow groundwater flooding, can also be
outside the flood plain.
Temperature Change Impacts
Direct sunlight accompanied by summer heat can causes ‘hot rails’ to buckle. The imposition of
speed restrictions in this situation is in order to mitigate the risk of buckling. In order to avoid
this, the rails need to be de-stressed which is a manual practice. The problem is most likely to
occur when there are rapid temperature changes between night and day and in extremely hot
weather.
Point heaters are used to ensure that points remain functioning in freezing conditions. It is
expected with the warmer winters predicted in the climate change scenarios that these point
heaters are likely to have to be used less often. There are therefore less likely to be technical
difficulties with the operation of these heaters, and less subsequent delays.