Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail

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Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
2019 – 2024

Wessex
Route CP6 Weather Resilience and
Climate Change Adaption Plans
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
2   Wessex Route WRCCA Plan 2020

    Contents

    Director of Engineering & Asset Management statement                             3

    Executive summary                                                                4

    Introduction                                                                     6

    Wessex Route WRCCA Plan                                                         12

    Wessex Route vulnerability assessment                                           13

    Wessex Route impact assessment                                                  28

    Wessex Route WRCCA actions                                                      35

    Management and review                                                           39

    Purpose of this document

    This document; defines the Wessex Route Weather Resilience and Climate Change Adaptation (WRCCA)
    Plan for CP6 and reviews progress against the WRCCA Plan published for CP5. This is supported by
    an evaluation of the resilience of rail infrastructure to historical weather events and an awareness of
    potential impacts from regional climate change projections. The resilience of the rolling stock operating
    within the route is not specifically assessed.

    Wessex Route Weather Resilience and Climate Change Adaptation Plan – Version 1 October 2020.
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
Wessex Route WRCCA Plan 2020                                                                                   3

                        Director of Engineering &
                        Asset Management statement
                        The railway network has been significantly affected by severe weather
                        conditions including wind, snow, rainfall, lightning, heat and cold,
                        all of which can impact our passengers.

Figure 1
Repairing a track
washout in the
Axe Valley, Salisbury
to Exeter line –
November 2012

                        Climate change projections suggest we will be            form part of the CP6 investment plan. Plans to
                        entering a period with increasing average and            address these strategic risks will be developed in
                        maximum daily temperatures, drier Summers,               CP6 and funding to implement changes to the
                        wetter Winters, sea level rises and increased            infrastructure requested in future control periods.
                        storminess. Increased storminess and Winter              Through careful investment in the highest risk
                        rainfall will increase the risk of flooding, earthslip   sites, better monitoring of vulnerable locations
                        and coastal storm surges. Hotter and drier               and more comprehensive seasonal planning,
                        Summers will increase track buckles and the              Wessex Route will continue to reduce the impact
                        risk of desiccation related track quality                of severe weather on the passengers and our
                        problems respectively.                                   lineside neighbours through CP6.

                        Wessex Route is particularly vulnerable to               Stuart Kistruck
                        predicted changes in precipitation as significant        Southern Region Director Engineering &
                        parts of the route are constructed on moisture           Asset Management
                        sensitive clay. These parts of the route are
                        susceptible to desiccation, which impacts track
                        quality in Summer and Autumn, and embankment
                        failure during extended wet periods. While we are
                        able to mitigate the safety risk from these failures,
                        they have a direct and unacceptable impact on
                        journey times and passengers. Approximately 1/3
                        of the route runs in cuttings which are vulnerable
                        to earthslip during extended periods of wet
                        weather and during intense storms. The track in
                        these areas is also vulnerable to flooding as the
                        capacity of drainage systems is insufficient for
                        increased precipitation. There are several parts of
                        the route vulnerable to flooding from rivers and
                        the sea, funding to address these issues does not
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
4                     Wessex Route WRCCA Plan 2020

                       Executive summary
                       Current weather events can cause significant disruption to the
                       operation of train services and damage to rail infrastructure;
                       this has a negative impact on our customers.
                       Disruption leads to delays and cancellations to           Wessex Route is committed to supporting the
                       train services, and infrastructure damage can lead        improvement of weather and climate change
                       to lines being closed to rail traffic for extended        resilience through the delivery of the route-specific
                       periods. The UK Climate Change Projections 2018           objectives. We have developed an understanding
                       (UKCP18) indicate that there will be a shift to a         of our risks by; assessing our weather-related
                       warmer climate with significant changes in sea            vulnerabilities (for example Figure 2), identifying
                       level and the pattern and intensity of precipitation      root causes of historical performance impacts and
                       across the year. Changes in the frequency and             using UKCP18 climate change projections.
                       intensity of extreme weather events and seasonal
                                                                                 Our 2014 Route WRCCA Plan set out our Route
                       patterns as a result of this could alter the likelihood
                                                                                 WRCCA Strategy, summarised the findings of
                       and severity of weather event impacts. A detailed
                                                                                 our route vulnerability and impact assessments,
                       understanding of the vulnerability of rail assets
                                                                                 detailed the CP5 investments and actions that
                       to weather events, and potential impacts from
                                                                                 we would take to mitigate these and highlighted
                       climate change, are therefore needed to maintain
                                                                                 future considerations.
                       a resilient railway.

Figure 2
Wessex Route weather
attributed delay
minutes – 2006/07
to 2018/19

                                                                                 This updated plan reports our CP5 progress, sets
                                                                                 out our plan for CP6 and beyond and updates
                                                                                 our vulnerability and impact assessments to
                                                                                 account for changes in the Network Rail WRCCA
                                                                                 Strategy and guidance.
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
Wessex Route WRCCA Plan 2020                                                                                               5

                                   In 2017 the Network Rail guidance on the                              In CP6 Wessex Route will continue to deliver
                                   climate change projections to be used for                             works to mitigate weather and climate risk,
                                   impact assessment and planning was reviewed.                          these include;
                                   This recommended using the UKCP09 Medium
                                                                                                         •	
                                                                                                           A continuation of the programme of track
                                   scenario, 90th percentile probability1. With the
                                                                                                           drainage refurbishment and renewal,
                                   release of the UKCP18 data this has been updated
                                   to the UKCP18 Representative Concentration                            •	
                                                                                                           A significant programme of crest drainage
                                   Pathway (RCP) 6.0 90th percentile.                                      improvements to high risk cuttings,

                                   Key aspects of our CP5 delivery were;                                 •	
                                                                                                           Pro-active scour protection works to 4No.
                                                                                                           bridges, with risk score greater than 16,
                                   •	
                                     A significant pumped drainage system,
                                     constructed in 2017 at Fullwell in South West                       •	
                                                                                                           Further refurbishment of coastal defences at
                                     London to address a long-standing track                               Poole Harbour,
                                     flooding problem,                                                   •	
                                                                                                           Renewal of high-risk earthworks at 36 locations,
                                   •	
                                     Over 135,000m of track drainage refurbishment                       •	
                                                                                                           Refurbishment of high-risk earthworks at
                                     and renewal, reducing the incidence of track                          77 locations,
                                     flooding at locations throughout the route,
                                                                                                         •	
                                                                                                           Culvert works including relining where required
                                   •	
                                     Renewed or refurbished crest drainage to                              to 30No. poor condition culverts,
                                     the top 10 highest risk cuttings, significantly
                                     reducing landslip and derailment risk,                              •	
                                                                                                           Maintenance of existing monitoring systems
                                                                                                           on high risk earthworks, and the installation of
                                   •	
                                     A significant Department for Transport (DfT)                          monitoring on more high-risk sites, and
                                     funded project, constructed in 2018 to install
                                     two new bridges in the Axe Valley on the                            •	
                                                                                                           Renewal of two bridges at Yetminster, Dorset
                                     Salisbury to Exeter line to reduce the frequency                      at risk of failure during flood events.
                                     of track flooding and the risk of flooding related                  During CP6 Wessex Route will continue to work
                                     embankment failure and bridge scour,                                to understand vulnerability to a changing climate
                                   •	
                                     A DfT funded programme of resilience                                and to develop investment plans to address the
                                     improvements consisting of: enhanced crest                          risks in future control periods.
                                     drainage systems at Hedge End and Sway in                           Although the actions taken in CP5 improved
                                     Hampshire, and the replacement of a culvert                         aspects of our resilience, weather events continue
                                     at Sherburne Dorset with a significantly larger                     to impact our operations. Wessex Route is
                                     structure,                                                          committed to addressing the risks through the
                                   •	
                                     Monitoring equipment installations at 22 high                       timely, cost efficient and safe delivery of this
                                     risk cuttings and one high risk embankment to                       Route WRCCA Plan.
                                     alert engineers to earth movement that may
                                     indicate imminent landslips,

                                   •	
                                     River level monitoring equipment installations
                                     at 6 bridges at risk of flooding and scour
                                     to mitigate risk and minimize the use of
                                     operational restrictions to manage safety,

                                   •	
                                     Improved scour protection to 4No. bridges,
                                     reducing the risk of asset failure,

                                   •	
                                     Repair works, including relining to 2615m2 of
                                     culvert structures,

                                   •	
                                     Refurbishment to 1700m2 of coastal defences
                                     at Poole Harbour.

1Previous   recommendation used in the 2014 Route WRCCA Plans was UKCP09 High scenario, 50th percentile probability
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
6                           Wessex Route WRCCA Plan 2020

                            Introduction
                            The railway routinely operates in a wide range of weather conditions,
                            however adverse and extreme weather can still cause significant
                            disruption to our network, resulting in significant inconvenience to
                            customers who find their planned journeys delayed or cancelled.

                            Current weather events such as extreme rainfall,       •	Heat – high temperature impacts e.g. rail
                            snow (and the resultant melt water) and high              buckles, Temporary Speed Restrictions (TSRs),
                            temperatures can cause delays, raise operating            overheated electrical components,
                            costs and increase safety risks. During Summer
                                                                                   •	Lightning strike – e.g. track circuit and signalling
                            2018 an extended period of warm, dry weather
                                                                                      damage or power system failure,
                            led to extensive desiccation damage to the
                            track in areas where the track is constructed on       •	Snow – e.g. blocked lines and points failures,
                            embankments in areas of moisture sensitive
                                                                                   •	Subsidence – the impacts of landslips, rockfalls
                            clay. This resulted in deformation to the track at
                                                                                      and sinkholes, and
                            78 locations in the Wessex Route. In February
                            2019 train services were suspended between             •	Wind – e.g. trees and other items blown onto
                            Basingstoke and Winchester for over 8 hours after         the track and into the Overhead Line Equipment
                            a heavy fall of wet snow brought down trees,              (OLE) or TSRs.
                            blocking the line.
                                                                                   As this data includes the duration and location
                            We monitor the impact of weather events on             of each disruption, and attributes cause, it gives
                            the performance of our network by using delay          a high degree of granularity for use in analysing
                            minutes and Schedule 8 delay compensation
                                                                                   weather impacts and trends.
                            costs2. Incidents are recorded under 9 categories
                            as follows;                                            In the past 13 years (2006/07 to 2018/19) the
                                                                                   average annual number of Schedule 8 delay
                            •	Adhesion – line contamination leading to
                                                                                   minutes attributed to weather for the Wessex
                               traction loss, e.g. leaf fall, moisture, oils,
                                                                                   network was 137,838. This represents 12.9% of
                            •	Cold – e.g. ice accumulations on conductor rails,   the total number of delay minutes for all causes
                               points and in tunnels,                              over that period and equates to an average annual
                            •	Flooding – standing or flowing water leading        cost of £6.5m.
                               to asset damage or preventing trains from           The impacts of severe weather events on the
    Figure 3                   accessing the track,
    Wessex Route                                                                   Wessex Route can be clearly seen in Figure 3, for
    weather attributed      •	Fog – reduced visibility obscuring signals,         example;
    delay minutes by year
    – 2006/07 to 2018/19                                                           •	
                                                                                     Snowfalls of 2009 through to 2011 and
                                                                                     2017/18,

                                                                                   •	
                                                                                     Wind in a number of years, but particularly
                                                                                     2013/14 and 2018/19,

                                                                                   •	
                                                                                     Flooding in all years, but particularly in 2009/10,
                                                                                     2010/11, 2012/13 and 2016/17,

                                                                                   •	
                                                                                     Extreme heat in 2018/19, and

                                                                                   •	
                                                                                     Significant delay attributed to lightning in
                                                                                     2014/15 largely due to a single storm that
                                                                                     disabled a large signal box responsible for
                                                                                     controlling trains on a key part of the route.

                                                                                   2The compensation payments to passenger and freight train operators

                                                                                   for network disruption
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
Wessex Route WRCCA Plan 2020                                                                                                                      7

                                   The costs of weather attributed Schedule 8                                    Trends in the UK climate, and the UKCP18
                                   and 4 payments and the wider socio-economic                                   data, indicate that there has, and will continue
                                   impacts of rail disruption on the UK justify                                  to be, a shift to a warmer climate. Figure 4
                                   continued investments to increase current                                     illustrates the changes in frequency and severity
                                   weather resilience. Network Rail’s collaborative                              of Atlantic Winter storms and Figure 5 shows
                                   approach to understanding weather impacts in                                  observed increases in the Central England
                                   the increasingly interdependent infrastructure,                               Temperature record.
                                   societal and environmental systems is key to
                                   identifying appropriate resilience response that
                                   support our role in developing regional and
                                   national resilience.

Figure 4
Intensity and
frequency of high
latitude Atlantic
Winter storms3

Figure 5
Mean Central England
Temperature record4

3
 Xiaolan L. Wang, Y. Feng, G.P. Compo, V.R. Swail, F.W. Zwiers, R.J. Allan, P.D. Sardeshmukh. 2012. Trends and low frequency variability of extra-tropical cyclone activity in the
ensemble of twentieth century reanalysis
4
 Parker, D.E., T.P. Legg and C.K. Folland. 1992. A new daily Central England Temperature Series, 1772-1992. Int. J. Clim., Vol12, pp 317-342
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
8                                Wessex Route WRCCA Plan 2020

                                 Introduction continued
                                 UKCP18 projects an overall shift towards warmer   Examples of the changes are shown in Figure 6 for
                                 climates with drier Summers and wetter Winters    the mean daily maximum Summer temperature
                                 for the whole of the UK, although the level of    and Figure 7 for Winter precipitation.
                                 change will vary across the regions.

Figure 6
Change in mean daily
maximum Summer
temperature (°C) (left
to right; 2030s, 2050s
and 2070s) based
on a 1981–2000
baseline5

Figure 7
Change in Winter
precipitation (%) (left
to right; 2030s, 2050s,
2070s) based on a
1981–2000 baseline6

© UK Climate Projections, 2018
5

© UK Climate Projections, 2018
6
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
Wessex Route WRCCA Plan 2020                                                                                  9

                                  The potential increases in weather impacts due          For the 2014 Route WRCCA Plans, Network Rail’s
                                  to climate change support the business case             national guidance was to use the UKCP09 High
                                  for enhancing weather resilience action and             scenario, 50th percentile probability projections
                                  identifying actions that will deliver a railway that    as an appropriate benchmark on which to base
                                  is safe and more resilient to the effects of weather,   evaluations and decisions. In 2017 Network Rail
                                  now and in the future.                                  commissioned a review of its guidance taking
                                                                                          into account the Paris Agreement, advances
                                  The 2015 Paris Agreement unites nearly every
                                                                                          in climate science, additional years of climate
                                  nation in a common cause to undertake ambitious
                                                                                          observations and the then pending release of the
                                  efforts to combat climate change and adapt to
                                                                                          UKCP18 dataset.
                                  its effects. The central aim is for a strong global
                                  response to the threat that keeps the global            The conclusions of the review7 were that as we are
                                  temperature rise this century to well below 2°C         a safety critical focused organisation and a major
                                  above pre-industrial levels and to pursue efforts to    UK infrastructure manager the most appropriate
                                  limit it to 1.5°C.                                      UKCP projections to use are:

                                  The Department for the Environment, Food and            •	
                                                                                            UKCP18 – RCP6.0, 90th percentile probability
                                  Rural Affairs (Defra) provides national climate           as the baseline scenario for evaluations and
                                  change guidance in a number of ways to enable             decisions, and
                                  the assessment of future climate risks and the
                                                                                          •	
                                                                                            RCP8.5 90th percentile as the sensitivity test on
                                  planning of adaptation actions to maintain and
                                                                                            assets with a lifespan beyond 2050.
                                  improve resilience. Most important to Network
                                  Rail and the Wessex Route are;                          Analysis in this report has been updated to use
                                                                                          the UKCP18 projections where available. It should
                                  •	
                                    The UK Climate Projection data sets which are
                                                                                          be noted that some UKCP09 parameters have not
                                    produced by the Met Office Hadley Centre, and
                                                                                          been updated in UKCP18. Where this is the case,
                                  •	
                                    The National Adaptation Programme (NAP).              the UKCP09 data has been used and this is clearly
                                                                                          indicated in the report.
                                  The UK Climate Projection data sets are produced
                                  for use in assessing the future risk and impacts of
                                  the possible climate projections for the UK. They
                                  are used by government to conduct the 5 yearly
                                  UK Climate Change Risk Assessments (UKCCRA)
                                  and by individual organisations to understanding
                                  and planning for their specific risks.

7Identifying   a climate change planning scenario, JBA Consulting 22/02/18
Wessex 2019 - 2024 Route CP6 Weather Resilience and Climate Change Adaption Plans - Network Rail
10                     Wessex Route WRCCA Plan 2020

                       Introduction continued
                       The NAP is based upon the UKCCRA and is              Although climate change projections include
                       published by Defra every 5 years. It contains        uncertainties, associated with natural climate
                       a summary of the impacts expected for each           variability, climate modelling and future
                       sector of the UK economy and tables detailing        emissions, they and the actions from the
                       adaptation actions that the UK Government            NAP can be used to provide guidance on the
                       requires those sectors to undertake to ensure the    direction that the UK climate may take. Wessex
                       continuing resilience of the UK economy.             Route has therefore used the projections in the
                                                                            creation of this WRCCA Plan.
                       The sectorial actions are apportioned to key
                       stakeholders such as regulators and national         To ensure a consistent approach to WRCCA
                       infrastructure operators. Details of the Transport   consideration and action across Network Rail
                       Sector actions in the NAP 2018 that are              an iterative framework of key management
                       apportioned to Network Rail and hence the            stages is used (see Figure 8). The same
                       Wessex Route are included in Table 6 in the          framework has been applied to develop this
                       Wessex Route WRCCA Actions section of this Plan.     Route WRCCA plan.

Figure 8
Weather resilience
and climate change
adaptation framework                                        Strategy and
                                                                policy

                                Adaptation                Management                    Vulnerability
                                 options                   and review                   assessment

                                                               Impact
                                                             assessment
Wessex Route WRCCA Plan 2020                                                                             11

Network Rail will take a range of soft (changes     The following sections provide findings from the
to processes, standards, specifications and         updated Wessex Route vulnerability and impact
knowledge and skill base) and hard (engineered      assessments, and detail; progress on the CP5
solutions to increase resilience) WRCCA actions     resilience actions, actions planned for CP6 and
tailored to the level of risk and the strength of   additional actions for future consideration.
evidence for it. Examples include;

•	Do nothing/minimum – the option to do
   nothing/minimum and the risks should be
   evaluated,

•	No regrets – increasing current and future
   resilience without compromising future
   flexibility,

•	Precautionary – investment in adaptation now
   in anticipation of future risk, and

•	Adaptation pathways – staged adaptation
   balancing future risk and current investment
   funds through phased investment enabling
   assets to be retrofitted cost-effectively in
   the future.

                                                    Figure 9
                                                    Track defects resulting from desiccation in a clay
                                                    embankment near Guilford – September 2018
12                   Wessex Route WRCCA Plan 2020

                     Wessex Route WRCCA Plan
                     Network Rail’s WRCCA Policy sets out the approach to achieving
                     our company’s vision of ‘A better railway for a better Britain’
                     by creating a railway that is safer and more resilient to weather
                     impacts now and in the future.

                     It commits the business to seeking to apply the         Wessex Route Plan
                     following key principles;
                                                                             Wessex Route is committed to including current
                     •	Including current and future weather impacts in      and future weather impacts when prioritising,
                        our risk analysis and investment decision making     developing and delivering capital investment
                        and embedding climate change specifications          and to ensuring that weather and climate
                        into policies, procedures and standards,             change resilience is achieved at lowest whole life
                                                                             cost, where sufficient capital budget is available
                     •	Adapting at construction and at asset renewal,
                                                                             to achieve that aim. The route is committed
                        designing schemes to be resilient in the most
                                                                             to renewing on a like for better basis when
                        cost-effective manner and/or with passive
                                                                             catastrophic asset failure occurs.
                        provision for future weather conditions,
                                                                             Wessex Route has developed a register of areas
                     •	In the event of catastrophic asset failure
                                                                             and assets vulnerable to weather and climate
                        replacing on a like for better basis rather than
                                                                             risk, these registers will be maintained and
                        like for like, considering the whole life cost and
                                                                             improved during CP6, with mitigations for the
                        the best strategy for managing the railway,
                                                                             highest risks developed. Where route funding
                     •	Identifying high priority locations for proactive    cannot address risks, high level investment
                        resilience interventions and working to identify     plans will be developed, and schemes added to
                        funding sources for projects not included within     the enhancement work bank for future funding.
                        agreed Control Period funding, and
                                                                             Wessex Route will continue to improve operational
                     •	Working with stakeholders to identify                procedures used to mitigate weather risk and
                        opportunities to enhance our preparation for,        will work with professional partners to develop
                        response to and recovery from adverse/extreme        integrated plans to manage shared risks.
                        weather events.

Figure 10
Undertaking
temporary repairs
to a storm damaged
embankment at
Yeovil Somerset –
February 2014
Wessex Route WRCCA Plan 2020                                                                               13

Wessex Route
vulnerability assessment
In the 2014 Route WRCCA Plan this section provided details of the
general vulnerability of the national rail network and Wessex Route’s
specific vulnerabilities to current weather impacts, and regional
climate change projections.

This Plan updates the vulnerability assessment
                                                      Primary event                      Secondary event
taking account of;

• Advances in climate science,                      High temperature                           Drought

•	
  Improvements in our understanding of the
  impacts of weather and future climate, and           Low rainfall                        Dessication

•	
  Changes in Network Rail’s climate change
  policy and guidance since the last plan              High rainfall                    Interdependencies

  was published.
                                                      Sea level rise                           Earthslip
Network-wide weather vulnerability

The rail network and its component assets are
                                                     Low temperature                           Flooding
sensitive to the effects of a number of weather
types. These manifest as either primary events
                                                          Snow                                 Erosion
(one weather type) or secondary events which
are the result of these and/or a combination of
weather types. It should be noted that these are      Wind/storms                         Ground heave

the mechanisms by which impacts are felt, not the
actual impacts themselves. Figure 11 illustrates        Lightning
the primary event types and their related
secondary event types.
                                                           Fog

                                                    Figure 11
                                                    Examples of primary and secondary events
14   Wessex Route WRCCA Plan 2020

     Wessex Route
     vulnerability assessment continued
     Managing a complex array of assets with                The key findings of this work were that earthworks
     varying ages, condition and weather vulnerabilities    were the asset most affected by rainfall, OLE was
     across a wide range of bio-geographic regions          most sensitive to wind and that temperature
     in a variety of climates is a complex challenge.       impacted the widest range of assets. These and
     Interdependencies with other sectors of the            the detailed outputs behind them have been
     economy, for example power, telecoms and water         disseminated to Network Rail’s national asset
     infrastructure add to this.                            function teams and the routes for use in asset
                                                            maintenance and investment planning.
     Understanding current weather impacts is essential
     for assessing the probable effects of climate          As the above work was based upon current data the
     change and for the planning and implementation         changes to Network Rail’s national guidance for
     of appropriate cost-effective resilience investments   the climate change planning projections have not
     to adapt the network to the future impacts.            changed the conclusions.

     The 2014 Plan outlined how we monitor the impact       We continue to monitor and analyse this data and
     of weather on the performance of our network by        we now have a 13-year series increasing our capacity
     using Schedule 8 delay compensation costs and the      to discern trends in failures and performance.
     process we used to carry out a detailed analysis of    We have now made the raw data available and
     this data to understand;                               we are continuing to look at how we can improve
                                                            its use including through trend and performance
     •	The characteristics of weather-events that
                                                            reporting on a period, quarter an annual basis.
        trigger failures,

     •	The thresholds at which failure rates change, and

     •	Trends in the failures of assets and the
        performance of the network.
Wessex Route WRCCA Plan 2020                                                                                   15

                      Route weather vulnerability

                      Wessex Route has some specific vulnerability to          The repeated seasonal expansion and contraction
                      severe weather. The western parts of the route           can also, over long periods, push over retaining
                      pass through difficult topography requiring the          walls and results in embankments becoming
                      original railway builders to use numerous deep,          lower and wider over many years. This requires
                      steep cuttings, tunnels and large embankments            maintenance to maintain track geometry more
                      to maintain acceptable gradients. To minimize            intensively than in areas with more stable geology.
                      construction costs the lines were routed down river
                                                                               Southern parts of Wessex Route pass through the
                      valleys where possible, this has resulted in this part
                                                                               tidal flood zone, this causes infrequent disruption
                      of the route suffering from a high risk of earthslips
                                                                               at present, however future risk must be quantified
                      and flooding in wet weather conditions. This risk
                                                                               so that appropriate plans can be made before the
                      is raised further by the effect the Blackdown Hills
                                                                               risk of tidal flooding and coastal erosion becomes
                      has on locally increasing rainfall rates, and the
                                                                               unacceptable. During CP5 a study was undertaken
                      east west orientation of the Route in this area
                                                                               to quantify the coastal flooding and erosion risk
                      that means that storms tend to track along the
                                                                               and some erosion protection work has been
                      line resulting in flooding in multiple locations.
                                                                               progressed at Poole Harbour.
                      Roads in the area are also prone to flooding and
                      earthslip often making it difficult or impossible for    Specific vulnerabilities on the Wessex Route to
                      maintenance staff to access sites to quickly rectify     weather impacts include high-risk earthworks
                      problems. All tunnel approach cuttings on this line      on the Salisbury to Exeter line. This area of the
                      had crest drainage improved during CP5 to reduce         network passes through the Blackdown Hills
                      the risk of landslip, and all of these cuttings have     which are prone to failure during periods of
                      also had monitoring installed during CP5 to alert        heavy rain due to very soft geology and over
                      engineers should a landslip occur.                       steep earthworks. Honiton tunnel is a good
                                                                               example of the challenge in managing these
                      In large areas at the eastern part of the route
                                                                               assets. Improved drainage has been constructed
                      the underlying geology is of moisture sensitive
                                                                               during CP5, and the most vulnerable areas are
                      clay, a material that is prone to softening
                                                                               programmed for investment in CP6 to arrest
                      and expanding in wet Winter conditions and
                                                                               active landslips in the cutting. Similar conditions
                      shrinking when desiccated, a risk in dry Summers.
                                                                               exist on parts of the Weymouth to Bristol line and
                      This results in an elevated risk of landslip
                                                                               elsewhere on the route.
                      in wet Winters and difficulty in maintaining
                      track geometry in late Summer and early Autumn.

Figure 12
Honiton tunnel
earthwork failure –
February 2012
16                       Wessex Route WRCCA Plan 2020

                         Wessex Route
                         vulnerability assessment continued
                         Large sections of the Salisbury to Exeter line near   Several bridges within the route are at higher risk
                         Axminster run in the River Axe flood plain. Some of   of flood damage including those at Yetminster
                         the embankments and up to nine river crossings in     on the WEY line and at the River Frome on the
                         this area require modification to reduce the risk     Bournemouth main line. The Yetminster bridge
                         of flood damage. The embankment near Broom            will be replaced in early CP6, but due to technical
                         Level Crossing was strengthened with sheet piles      constraints the new bridges will not offer
                         in CP4 to reduce the chance of washout at this        significantly improved performance during flood
                         location in the future. In 2018 two new bridges       events. While the bridges remain at significant
                         were built, one at Broome Level Crossing and one      risk of inundation, they will however feature more
                         at Axe Farm Level Crossing to reduce the risk of      resilient construction, therefore reducing the risk of
                         future embankment failure. The line remains at        asset failure during flood events, and reducing the
                         significant risk of flooding due to the increasing    time taken to re-open the line following flooding.
                         river flows and the low height of the embankments     River level monitoring via Remote Condition
                         throughout the area.                                  Monitoring (RCM) and a robust procedure to
                                                                               stop traffic when river levels are unsafe will be
                                                                               maintained to ensure safety.

 Figure 13
 Track washout at
 Broom Crossing,
 Axe Valley –
 November 2012

 Figure 14                                                                                                     Figure 15
 Construction of new                                                                                           Yetminster bridge
 railway bridge in the                                                                                         during high river
 Axe Valley to reduce                                                                                          flows – January 2008
 future flood impact –
 September 2018
Wessex Route WRCCA Plan 2020                                                                                         17

                       Recent severe Winters have exposed the route to           function has entered into an agreement with the
                       significant flooding. The line at Datchet was closed      EA to build the ‘on railway’ portion of this project
                       for several days in early 2014 as a result of the River   consisting of removal of all railway infrastructure
                       Thames experiencing the highest levels recorded           from the new bridge locations, construction of
                       for over 40 years, reminding all that significant         the two new bridges and reinstatement and
                       parts of Greater London are at risk of flooding.          commissioning of railway assets and systems.
                       The Environment Agency (EA) has designed a
                                                                                 Large parts of the route near the South Coast are
                       scheme to improve the flood performance of
                                                                                 vulnerable to sea level rise including sections of
                       this section of the Thames. The EA is planning to
                                                                                 line near Poole Harbour and the Portsmouth line
                       undertake significant works in late CP6 to reduce
                                                                                 as it approaches through Portcreek Junction and
                       the flood risk to communities in the Datchet area.
                                                                                 crosses Portcreek Viaduct. This viaduct will require
                       This will require the construction of two new
                                                                                 replacement before mid-century as track level is
                       bridges under the Windsor and Eaton Riverside
                                                                                 currently predicted to be below flood levels at
                       branch and a new river channel adjacent to the
                                                                                 that time and is below the crest level of the new
                       railway to connect these two bridges to the main
                                                                                 flood defences recently constructed to protect
                       river channel. Wessex Route is actively engaged
                                                                                 Portsmouth from rising sea levels.
                       with the project. Network Rail’s Capital Delivery

Figure 16
Portcreek viaduct
at high tide – month
not known 2018

                       Large parts of Wessex Route are built on moisture         The BKE line forms part of the strategic freight
                       sensitive clay. Embankments constructed from this         network and there is no freight diversion due to
                       material are prone both to conventional failure           restricted gauge on all alternatives. Significant
                       when saturated in Winter but also to desiccation          works are required to improve resilience of the
                       where track quality is very difficult to maintain in      BKE line and in order for this work to take place a
                       dry Summer and Autumn conditions. This affects            freight diversion is likely to be required to facilitate
                       several lines but is most pronounced on the BKE           sufficient access to undertake such significant
                       line between Reading and Basingstoke, the GTW             work. Desiccation is likely to be an increasing
                       line from Guildford to Ash, the NGL line from             challenge to manage as longer, drier Summers
                       Guildford to Surbiton, the ETF line from Eastleigh        with higher average and peak temperatures lead
                       to Fareham, the BAE2 line from Gillingham to              to increased desiccation and therefore more
                       Yeovil, and elsewhere on the route, including the         shrinkage which is likely to lead to more track
                       BML line between Wimbledon and Woking.                    quality issues.
18                      Wessex Route WRCCA Plan 2020

                        Wessex Route
                        vulnerability assessment continued
                        Wessex Route is largely DC electrified and this         Heat speeds are currently well managed and
                        technology although extremely resilient in most         most jointed track has been removed from heavily
                        conditions is prone to icing. The worst effect          trafficked parts of the route with the small areas
                        occurs when rain falls on a conductor rail that is      of jointed track remaining largely programmed
                        below freezing. This happens infrequently but the       for removal in CP6. Maintenance work is
                        consequences are very disruptive, particularly if       programmed to minimize formation disturbance
                        this occurs early in the morning before rail traffic    during the Summer months. Increased
                        is busy enough to clear ice as it forms. Conductor      maintenance volumes in CP6 will allow the
                        rail icing is likely to be a reducing problem in the    track to enter the Summer period with better
                        future, and well targeted rail head treatment with      geometry and more consistent stressing,
                        hydrophobic products can significantly reduce           increasing resistance to desiccation and high
                        the impact of these conditions by preventing            temperatures. As average temperatures increase,
                        water freezing to the con-rail. DC electrification      the length of Summer in effect lengthens, and
                        is also unreliable if flooding occurs, this is likely   the window for intrusive track maintenance
                        to increase in frequency unless significant             will reduce. This will be a significant challenge for
                        improvements are made to the drainage asset.            maintenance teams who do not currently have
                        The areas of the route most at risk from coastal        access to any additional maintenance shifts
                        flooding are DC electrified. During CP6 the impact      in Winter.
                        of this emerging risk must be better understood
                                                                                As embankments weather they tend to become
                        and plans drawn up to mitigate them in the long
                                                                                narrower at the crest and over time they settle.
                        term. A significant proportion of snow related
                                                                                Most current track maintenance practices
                        delay in Winter 2018/19 was as a result of
                                                                                maintain the height of or raise the track, and the
                        coppiced hazel in chalk cuttings overturning onto
                                                                                position of the track must be maintained over
                        track and blocking the line. This vegetation cannot
                                                                                structures. These factors together have resulted
                        be removed as it is valuable dormouse habitat,
                                                                                in parts of the route suffering from having no
                        but it can be managed in a way that prevents it
                                                                                space at the crest for a safe cess and insufficient
                        posing a risk to the passage of trains.
                                                                                space to maintain a compliant ballast shoulder.
Figure 17                                                                       As temperatures increase, we must find a
Pinks Hill embankment                                                           cost-effective way to lower track in areas where
failure – July 2014
                                                                                this is possible, so it fits on the underline bridges
                                                                                and embankments, or undertake works to make
                                                                                space for the track formation on the narrow
                                                                                embankments. The lack of cess width in places
                                                                                not only makes maintaining track difficult, it
                                                                                increases the chance of track buckling during hot
                                                                                weather, therefore requiring speed restrictions
                                                                                during hot weather to manage safety. A narrow
                                                                                cess also increases the chance of earthwork
                                                                                failures during wet weather, such as at Pinks
                                                                                Hill near Guildford which failed in July 2014
                                                                                following a very wet Winter.
Wessex Route WRCCA Plan 2020                                                                              19

One of the most significant weather-related
safety and performance incidents in recent years
was the St Jude storm of the 27th and 28th October
2013; this brought down hundreds of trees across
the route. If storm intensity and frequency
increases, the impact of such weather events will
be significant unless the number of trees able to
fall on the line, both owned by Network Rail and
third-party owned, is reduced.

Summer 2018 was the driest recorded for
Wessex Route since we started tracking Soil
Moisture Deficit in 2000. The extended dry period
coincided with the highest number of days with
an average temperature over 20°C, 29 days
exceeded this threshold. The previous highest
number of days over 20°C was 22 days, recorded
in 2003 and in 2017. This run of hot dry weather
had a devastating impact on performance as
desiccation led to a significant upturn in track
defects needing a speed restriction to manage
safety. During September 2018 there were up to
                                                     Figure 18
62 speed restrictions imposed; this led to a PPM     Track impacted by desiccation between Guilford and
attrition of over 3%.                                Ash – Summer 2018
20                               Wessex Route WRCCA Plan 2020

                                Wessex Route
                                vulnerability assessment continued
                                Future climate change vulnerability

                                The complexity of the relationship between                        UKCP18 provides regional projections across
                                weather events and climate means that the                         13 administrative regions in Great Britain
                                UKCP18 data set cannot forecast future weather                    (Figure 19), The Wessex Route falls within two of
                                events. It projects modelled probabilistic trends                 these regions, South East England and South West
                                that can be used to understand the potential                      England. These regions are therefore considered
                                future risks associated with certain climates and                 as representative of the route for the purposes of
                                the likely changes in weather events/parameters.                  analysing future climate projections.
                                Network Rail therefore uses projections from the
                                                                                                  In the 2014 Plan charts were generated using the
                                UKCP18 data set as a future baseline to understand
                                                                                                  UKCP09 High emissions 50th percentile probability
                                potential risks and for making informed strategic
                                                                                                  scenario for the two regions to show the projected
                                decisions to increase future weather resilience.
                                                                                                  changes in temperature and precipitation from
                                                                                                  the 2020s to the 2080s relative to the baseline
                                                                                                  climate of the 1970s (1961-1990).

                                                                                                  For this report the charts and associated narrative
                                                                                                  have been updated to match the current Network
                                                                                                  Rail climate change guidance which uses the
                                                                                                  current UKCP18 climate projections where
                                                                                                  available. Replacing the UKCP09 emissions
                                                                                                  scenario used in the 2014 report with the UKCP18
                                                                                                  emissions scenarios noted in the introduction has
                                                                                                  involved a number of changes to the data used.
                                                                                                  These include:

                                                                                                  •	
                                                                                                    Using a new baseline period of 1981-2000,

                                                                                                  •	
                                                                                                    Moving from projection time periods of
                                                                                                    30 years (2020, 2050, 2080) to shorter
                                                                                                    20-year periods (2030, 2050, 2070), and

                                                                                                    The use of UKCP18 RCP 4.5 95th percentile
                                                                                                  •	
                                                                                                    data for sea level rise as a proxy for RCP 6.0
                                                                                                    data (UKCP18 did not model RCP 6.0 for
                                                                                                    sea level rise).

                                                                                                  Figure 19
                                                                                                  Map of UK administration
                                                                                                  regions used in UKCP188

 8
  Source: Met Office © Crown Copyright 2019 [available from UKCP18 Guidance: Data availability,
 access and formats: https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/
 research/ukcp/ukcp18-guidance-data-availability-access-and-formats.pdf]
Wessex Route WRCCA Plan 2020                                                                          21

                      Mean Daily Maximum Temperature change               South East England

                      The mean daily maximum temperature for both         The highest mean Summer temperatures are
                      regions is projected to increase in every month     expected to be in August for both the 2050s
                      of the year, with the greatest increases expected   and 2070s with increases of 4.6°C to 26.4°C
                      in the Summer months. This increase becomes         and 6.3°C to 28.1°C respectively. In Winter the
                      larger across the century.                          highest mean temperatures will be seen in
                                                                          December, with increases of 2.1°C to 10.1°C and
                                                                          2.9°C to 10.9°C respectively.

Figure 20
South East England,
mean daily maximum
temperature change
(°C) (RCP 6.0 90th
percentile)
22                    Wessex Route WRCCA Plan 2020

                      Wessex Route
                      vulnerability assessment continued
                      South West England

                      The highest mean daily maximum Summer               In Winter the highest mean temperatures will be
                      temperatures are expected to be in August for       seen in December for the 2050s, with increases of
                      both the 2050s and 2070s, with increases of         2.0°C to 10.4°C and February by the 2070s with
                      4.5°C to 25.0°C and 6.2°C to 26.8°C respectively.   increases of 3.6°C to 11.3°C.

Figure 21
South West England,
mean daily maximum
temperature change
(°C) (RCP 6.0 90th
percentile)
Wessex Route WRCCA Plan 2020                                                                             23

                      Mean Daily Minimum Temperature change                South East England

                      The mean daily minimum temperature for               The highest mean daily minimum temperatures
                      the regions is also projected to show increases      for Summer are expected to be in August, with
                      throughout the year with the highest in Summer.      increases of 3.1°C to 15.0°C by the 2050s and
                      The level of increase is expected to become higher   4.6°C to 16.5°C by the 2070s. The lowest mean
                      across the century.                                  minimum temperatures will still occur in February
                                                                           with expected increases being 2.5°C by the 2050s
                                                                           to 3.6°C, and by 3.5°C by the 2070s to 4.5°C.

Figure 22
South East England,
mean daily minimum
temperature change
(°C) (RCP 6.0 90th
percentile)

                      South West England

                      The highest mean daily minimum temperatures          minimum temperatures will still occur in February
                      for Summer are expected to be in August, with        with expected increases being 2.7°C by the 2050s
                      increases of 2.9°C to 14.7°C by the 2050s and        to 4.3°C, and 3.8°C by the 2070s to 5.5°C.
                      4.5°C to 16.3°C by the 2070s. The lowest mean

Figure 23
South West England,
mean daily minimum
temperature change
(°C) (RCP 6.0 90th
percentile)
24                     Wessex Route WRCCA Plan 2020

                       Wessex Route
                       vulnerability assessment continued
                       Mean daily precipitation                             South East England

                       The UKCP18 narrative for mean daily precipitation    In the 2050s and 2070s December will be the
                       in the regions is of significantly wetter Winters    wettest month with mean daily rainfall increases
                       and drier Summers. Network Rail’s chosen climate     of 34.8% to 3.8mm/day and 50.3% to 4.2mm/
                       change planning scenario (RCP 6.0 90th percentile)   day respectively. The driest month will be July
                       shows the upper range of Winter rainfall             showing decreases of 48.6% to 0.8mm/day by the
                       increases, but it does not illustrate the highest    2050s and 51.3% to 0.7mm/day by the 2070s.
                       potential Summer rainfall reductions. These are
                       best represented by the RCP 6.0 10th percentile
                       projections. Figure 24 and Figure 25 therefore
                       plot the RCP 6.0 50th percentile projections with
                       error bars that indicate the wider range of change
                       associated with the 10th and 90th percentiles.

Figure 24
South East England,
mean daily
precipitation change
(%) (RCP 6.0 50th
percentile with the
wider range showing
the 10th and 90th
percentiles)
Wessex Route WRCCA Plan 2020                                                                         25

                       South West England

                       In the 2050s and 2070s December will be the        The driest month will be July showing decreases
                       wettest month with mean daily rainfall increases   of 45.1% to 1.0mm/day by the 2050s and 54.5%
                       of 27.2% to 5.4mm/day and 38.4% to 5.8mm/day       to 0.8mm/day by the 2070s.
                       respectively (and in the 2070s, both January and
                       December receive 5.8mm/day).

Figure 25
South West
England, mean daily
precipitation change
(%) (RCP 6.0 50th
percentile with the
wider range showing
the 10th and 90th
percentiles)
26                                 Wessex Route WRCCA Plan 2020

                                  Wessex Route
                                  vulnerability assessment continued
                                   Storm intensity and river flows

                                   In addition to changes in total rainfall, climate                          climate change data, however, at the time of
                                   change is also expected to increase the frequency                          publishing this plan the guidance is still based
                                   and severity of river flooding events and individual                       on the UKCP09 Medium Emissions scenario. This
                                   rainstorm events, Summer rainstorms will show                              recommends that rainstorm intensities for the
                                   the largest increases.                                                     Wessex Route regions should be increased by
                                                                                                              10% for the 2050s and 20% for the 2080s.
                                   The EA produces guidance on the rainstorm
                                                                                                              Climate uplifts9 for river flows are provided by river
                                   intensity and river flow uplifts that should be used
                                                                                                              basin and those relevant to the Wessex Route
                                   to account for climate change. This guidance
                                                                                                              regions are shown in Table 1.
                                   is being reviewed due to the release of UKCP18

Table 1                             River basin                                      2050s uplift                                      2080s uplift
River flow uplifts
                                    Thames                                           25%                                               35%
(UKCP09)
                                    South East England                               30%                                               45%
                                    South West England                               30%                                               40%

                                   Sea level rise                                                             South East England
                                   Sea level varies around the coast due to                                   Margate will see the highest rises by 2050 and
                                   differences in coastal morphology and isostatic                            2070 of 34.8cm and 53.1cm respectively and
                                   rebound since the last ice age. As this also affects                       Brighton will see the lowest at 34.6cm and 52.9cm.
                                   the degree of sea level rise, UKCP18 projections
                                   have been obtained for 3 coastal locations in
                                   both of the administrative regions covered by the
                                   Wessex Route10.

Figure 26
Sea level rise
projections for
South East England
(cm) (RCP 4.5 95th
percentile)

  9
   EA higher central climate change estimate as the most comparable to Network Rail’s climate change planning scenario.
  10
    Sea level rise data in UKCP18 is not available for RCP 6.0, instead RCP 4.5 is used as a proxy on the recommendation of the Met Office.
  This is the most compatible with the Network Rail Primary planning scenario.
Wessex Route WRCCA Plan 2020                      27

                     South West England

                     Penzance will see the highest rises by 2050 and
                     2070 of 36.5cm and 55.6cm respectively and
                     Weston-Super-Mare will see the lowest at 34.1cm
                     and 52.2cm.

Figure 27
Sea level rise
projections for
South West England
(cm) (RCP 4.5
95th percentile)
28                     Wessex Route WRCCA Plan 2020

                       Wessex Route impact assessment
                       This section provides an update of the Wessex Route weather impact
                       assessment findings published in the 2014 Wessex Route WRCCA
                       Plan, including annual performance impacts and identification of
                       higher impact locations on the Route.

                       Performance impacts

                       The impact of weather events on our network’s          restrictions to be used to mitigate safety risk when
                       performance is monitored using delay minutes           a threshold is exceeded. This generates a lot of
                       and Schedule 8 delay compensation costs as             delay versus the published timetable, whereas for
                       proxies. As this data includes the duration and        landslip (recorded in S8 data as subsidence) failures
                       location of each disruption, and attributes cause,     often block lines, and the costs of recovering from
                       it gives a high degree of granularity for use in       landslip can run into several £million for a single
                       analysing weather impacts and trends.                  site. A project to identify the true cost of weather
                                                                              and climate change disruption and recovery is
                       It is acknowledged that Schedule 8 has limitations
                                                                              being progressed in CP6.
                       in recording the true cost of weather and disruption
                       and does not account for the full cost of severe       In the 2014 plan eight financial years of Schedule
                       weather events. Schedule 8 disproportionately          8 data were analysed to give an assessment of the
                       represents impacts that lead to delay, rather than     weather impacts for the Wessex Route. This Plan
                       those that close lines. Wind is over represented       updates that assessment using additional data
                       as operational processes require blanket speed         from the past 5 years, see Figure 28.

Figure 28
Wessex Route weather
attributed Schedule
8 costs – 2006/07 to
2018/19
Wessex Route WRCCA Plan 2020                                                                                                                      29

                                 The updated analysis shows that wind continues                            There is a high degree of confidence in the UKCP18
                                 to be the most significant weather impact costing                         projections for temperature, rainfall and sea level
                                 a total of £22.4m in the last 13 years. This is                           rise, but lower levels for wind, lightning and snow
                                 around one third or so more than the costs of                             fall. Planning for the latter parameters should
                                 adhesion and flooding and more than double                                still be undertaken, but outputs should be more
                                 that of snow and cold related incidents which cost                        flexible to acknowledge the higher possibility of
                                 £15.4m, £12.2m, £10.5m and £9.9m respectively                             alternative climate outcomes.
                                 over the same period.
                                                                                                           The findings from the combined analysis of
                                 Climate modelling cannot provide future weather                           current weather impacts and UKCP data (UKCP09
                                 forecasts, but it does give us projections for the                        for wind, lightning and snow and UKCP18 for
                                 trends in future weather patterns. Combining                              temperature, precipitation and sea level rise will
                                 these trends with our analysis of current weather                         be used in the prioritisation of resilience actions
                                 impacts allows us to understand the future                                as summarised in Table 2 below.
                                 vulnerability and possible impacts upon the
                                 Wessex Route.

Table 2                            Impact           Schedule                 Climate projections12                                                              Prioritisation
Prioritisation of                                   8 Cost per
weather-related                                     year11
impacts on                         Wind             Average £1.73m           Changes difficult to project, however generally expected to increase               High
Wessex Route                                        Highest £6.91m
                                   Adhesion         Average £1.19m           Complex relationship between multiple causes and their climate                     Medium
                                                    Highest £2.57m           projections
                                   Snow             Average £0.82m           Changes difficult to project, but increases in Autumn, Winter and Spring           Medium
                                                    Highest £3.73m           minimum temperatures suggest reduced snow days
                                   Lightning        Average £0.56m           Changes in storms difficult to project, however generally expected to              Medium
                                                    Highest £3.18m           increase
                                   Cold             Average £0.76m           Increases in mean minimum daily temperatures across the regions                    Low
                                                    Highest £2.14m           in Autumn, Winter and Spring ranging from 1.8oC in April to 2.9oC in
                                                                             September for the 2050s and 2.7oC in April to 4.6oC in September for
                                                                             the 2070s
                                   Subsidence       Average £0.25m           Increases in mean daily rainfall across the regions for late Autumn, Winter        High
                                                    Highest £0.72m           and early Spring months, for example; 13.2% in April and 39.8% in
                                                                             January by the 2050s becoming 16.7% in April and 56.3% in January by
                                                                             the 2070s
                                                                             Decreases in mean daily rainfall for late Spring through to early Autumn,
                                                                             for example; 26.3% in May and 49.3% in August by the 2050s becoming
                                                                             37.2% in May and 58.4% in August by the 2070s
                                                                             Increased frequency and intensity of Winter and Summer storms
                                   Heat             Average £0.27m           Increases in mean maximum daily temperatures across the regions                    Medium
                                                    Highest £1.87m           range from 2.0oC to 2.5oC (Winter) and 2.9oC to 4.6oC (Summer) by the
                                                                             2050s. In the 2070s this becomes 2.8oC to 3.6oC and 4.4oC to 6.3oC
                                                                             respectively
                                   Flooding         Average £0.94m           Increases in mean daily rainfall for late Autumn through to early Spring           High
                                                    Highest £3.60m           and increased intensity and frequency of Winter and Summer storms
                                                                             (see subsidence)
                                   Fog              Average
30   Wessex Route WRCCA Plan 2020

     Wessex Route impact
     assessment continued
     Identification of higher risk locations                 Heat impact assessment
     Since the publication of the last Plan the Wessex       Between 2006/07 and 2018/19 heat related
     Route network has continued to experience               incidents accounted for an average of 4,745 delay
     extreme weather events that have challenged             minutes and £0.27m in Schedule 8 costs per year.
     weaknesses in our assets and operations. Climate        This is 3.4% of Wessex’s annual average weather-
     change projects more frequent and intense               related delay minutes and 4.1% of the annual
     extreme weather events, so understanding the            average cost.
     impacts of current and future events is critical to
                                                             Track asset
     investment decision making.
                                                             As we experience longer periods of dry and hot
     The impacts of weather on our Route are captured
                                                             weather, the management of the track asset needs
     via analysis of the delay minute and Schedule 8
                                                             to change. The increasing number of train services
     cost data and the outputs of this allow high impact
                                                             coupled with our desire to minimise passenger
     frequency/cost sites to be identified and targeted
                                                             disruption means that the track asset needs to be
     for detailed assessment to:
                                                             managed in a way that makes it more resilient to
     •	
       Verify the attribution of the delay(s) to a           the changes in weather the Route is experiencing
       weather impact(s),                                    than was previously the case.
     •	
       Determine the root cause of the delay,                The management of the track asset will now need
                                                             to include more robust preparation in advance
     •	
       Identify if resilience action has been taken in
                                                             of the Summer. This will comprise completion
       the past or is already planned, and
                                                             of hot weather preparation works to eliminate
     •	
       Generate and prioritise appropriate resilience        deficiencies such as unstressed rails and ballast
       actions.                                              shortages earlier in the spring, and to improve
                                                             geometry. The management of track geometry
     In addition to the above assessments Wessex
                                                             and ballast disturbance works will need to
     Route has also identified potential future risks
                                                             be reduced in Summer to help prevent track
     and resilience actions based on climate change
                                                             buckles. Any shortfall in this activity leads to staff
     projections and Route knowledge.
                                                             being deployed on watchman duties and speed
     Combining these findings allows us to proactively       restrictions being imposed – the more extreme
     identify potential investments that would address       temperatures get, the wider the need for blanket
     current weaknesses and mitigate and/or enable           speed restrictions.
     the mitigation of future risks. This approach is
     critical to creating a railway that is safer and more   The current process and framework with which
     resilient to weather impacts now and in the future.     we balance the risks of track geometry faults and
                                                             track buckle needs to evolve. The development
                                                             and delivery of requirements set out for the hot
                                                             weather preparation of the track asset needs
                                                             to achieve a reduction in the overall number of
                                                             deficiencies and specifically target no deficiencies
                                                             on certain parts of the network. Requirements
                                                             for the management of the track asset during
                                                             prolonged periods of hot and dry weather also
                                                             need to be made more robust – giving front line
                                                             teams clearer guidance on the management of
                                                             deteriorating track geometry versus track buckle
                                                             risk. Network Rail standards will also need to be
                                                             reviewed and updated as part of this process.
Wessex Route WRCCA Plan 2020                                                                                31

Vegetation                                              Buildings
Although current research is not advanced enough        As the year will become warmer on average in all
for us to be able to understand the detailed            seasons, and heatwaves will increase in frequency,
risks and impacts of climate change on our line         intensity and duration, the current building stock
side vegetation at this time, we can make some          will require modification or enhancement to provide
general assumptions that allow us to consider our       an internal environment suitable for customers,
responses going forwards.                               staff and equipment (for example electrification,
                                                        signalling and vital communications equipment).
As the year will become warmer on average in all
                                                        Much of our current lineside and depot building
seasons, growing patterns will change significantly
                                                        stock comprises lightweight modular buildings
over time. Some species may not tolerate the new
                                                        with poor thermal performance
local conditions and their distribution patterns
may change. Long lived species, for example some        Longer dryer Summers will lead to increased
broad leaved trees will potentially be less able to     desiccation, this is likely to represent an increased
adapt. There is also emerging evidence that some        risk of desiccation related subsidence to buildings
tree diseases, such as Ash die back, are increasing     constructed on moisture sensitive clay.
in prevalence due to climate change induced tree
                                                        Wetter Winters and a greater frequency of intense
stress. If the health of trees suffers they will need
                                                        rainfall events will test the water tightness of the
to be felled to manage safety risk, this is likely to
                                                        building stock and it may be necessary to upgrade
be both very expensive and will require careful
                                                        rainwater goods, particularly on large station and
management to protect organisational reputation.
                                                        train shed roofs.
In areas where currently dominant vegetation
dies back, or is removed, there is the potential for    Structures
pioneer species to colonise the rail corridor. Many     Longer dryer Summers will lead to increased
of these are likely to grow vigorously in the warmer    desiccation, this is likely to represent an increased
prevailing conditions and may potentially grow for      risk of desiccation related subsidence to structures
more of the year. Under these circumstances the         constructed on moisture sensitive clay.
intensity of lineside management may need to
increase to maintain rail safety. Changes in species    As structures tend to have a significant operational
range may also introduce species completely new         life the predicted temperatures are outside the
to the UK, potentially including species injurious      range envisaged when many of the current
to health. More vigorous growth would mean              structures were designed and constructed. Some
that core safety activity such as examination           structural elements will expand beyond design
of earthworks, drainage and structures may be           limits, initially freezing expansion joints, then
more difficult if the asset is obscured by greater      generating significant stresses and strains within
vegetation growth year-round. This could drive          the structures for which they were not designed.
a greater need for vegetation management. Our           The impact of this is currently poorly understood
ability to achieve such management may face             as each structure is unique and calculating the
greater constraints if the bird nesting season shifts   impact of such heat induced load would require
or expands. Changes in our lineside habitats and        work on a structure by structure basis, with high
the wider climate issues may mean that we will          quality survey data available.
need to consider changes in our current vegetation
management practices, for example; we may not
wish to leave significant cut and chipped material
on site due to increased risk of line side fires.
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