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