Climate interdependency risks for London’s transport sector: A systems approach to resilience

This article is an abridged version of the original report, which can be accessed for more detail and research purposes. The full, detailed project report is available upon request from katherinedrayson@tfl.gov.uk and friederikeholz@tfl.gov.uk

Summary

This report explores how climate change impacts the critical interdependencies between London’s Land-Based Transport Sector (LBTS) and other essential services such as power, water, and telecoms. The research combined a systems-mapping approach with a climate risk assessment, incorporating extensive stakeholder engagement. The main finding is that risks to London’s transport network from climate change are set to increase significantly, largely due to cascading failures from other infrastructure sectors. Key findings suggest:

• Surface water flooding is a major risk now and will intensify in the future.
• The transport sector’s dependency on the power grid will grow substantially with decarbonisation and electrification, increasing vulnerability to heatwaves and storms.
• There are significant knowledge gaps regarding the climate resilience of the telecoms sector, which represents a medium-level risk with low confidence in current assessments.
• Actions to address these risks require cross-sector collaboration, including creating shared risk registers, exploring co-funding for resilience measures, and developing best practices for green infrastructure.

Introduction

Under the Climate Change Act 2008, transport authorities voluntarily report on their climate adaptation progress through the Adaptation Reporting Power (ARP). For the fourth round of reporting (ARP4), the challenge is to understand how climate hazards create cascading impacts across different infrastructure sectors.

London’s transport network is already affected by severe weather, and climate change is projected to increase the frequency and intensity of heatwaves, drought, flooding, and sea level rise. In a congested urban environment like London, the failure of one system, such as the power grid, can trigger failures in another, such as transport. As the London Climate Resilience Review notes, “disruption to one part of the system has cascading effects”. The purpose of this research was to identify these interdependencies and assess how climate hazards will impact the delivery of transport services for Londoners.

Methodology

The project used a systems approach to analyse the complex problem of climate interdependency risks, in line with UK government recommendations. The methodology involved five key steps:

Prioritisation: A framework was used to prioritise these actions based on criteria such as risk level, co-benefits (win-win options), and adaptability, resulting in a list of short, medium, and long-term recommendations.

System frameworks: A review of existing documentation was conducted to establish high-level system maps for the LBTS and related sectors like power, water, telecoms, and environmental management.

Interdependency analysis: Through focus groups and a collaborative workshop with stakeholders from across sectors, these initial maps were refined into an integrated system map that identified key “hotspots” and organisational interfaces where risks are transferred.

Climate risk assessment: A formal risk assessment was conducted for 114 identified interdependency risks. Each risk was scored by multiplying its likelihood (informed by UKCP18 climate projections ) by its potential consequence (impact on safety, performance, and finances ). Risks were assessed for three time horizons: the present-day, the 2050s, and the 2080s.

Action development: Stakeholders co-developed a longlist of 52 risk-reduction actions in a dedicated workshop.

#1 Power sector interdependencies

Key Messages

• Increased demand for cooling during heatwaves will strain the power grid, creating a high risk of cascading failures impacting electrified transport services.
• Power transmission and distribution assets (pylons, substations, cables) are vulnerable to a wide range of climate hazards, including high winds, flooding, and extreme temperatures.
• As the transport sector electrifies its fleet and operations, its vulnerability to power sector disruptions will increase significantly into the 2050s.

The transport sector’s dependency on the power grid is one of the highest-scoring risks. Extreme high temperatures can reduce the efficiency of transmission lines and increase electricity demand for cooling, potentially leading to blackouts that disable traffic lights, signage, and rail systems. The 2019 power outage, which caused traffic light failures in London, serves as a key example. Furthermore, physical power infrastructure is vulnerable to damage from high winds and flooding, which can impact assets located far outside of London but still disrupt the city’s supply. The risk severity increases significantly in the 2050s as electrification of vehicles and smart motorway systems makes the LBTS ever more reliant on a stable power supply.

(Figure 3.1: Trends in total risk severity for each climate hazard, and the affected organisational interface across the three time horizons: today, 2050s, and 2080s )

Areas for action

• Establish a shared risk register to identify joint risks and co-create/co-fund adaptation solutions where a single intervention can deliver benefits for multiple interfaces.
• Ensure planning assumptions for extreme heat are aligned across power, rail, and road organisations.
• Lobby for changes to building regulations to manage risk to critical infrastructure from high temperatures.
• Join up adaptation investment across sectors to avoid redundancy and improve overall system resilience.

#2 Water and drainage interdependencies

Key Messages

• Pipe bursts, caused by ground movement from drought or temperature variation, can lead to localised flooding, closing roads, tracks, and stations.
• Surface water flooding, already a major risk, will be exacerbated as intense rainfall overwhelms urban drainage systems, a situation made worse by sea-level rise causing “tidal locking” of outfalls.
• While water companies have adaptation plans, risks are expected to increase beyond 2050 if investment does not keep pace with climate projections.

The LBTS is vulnerable to failures in London’s water infrastructure, primarily from pipe bursts and the capacity of the urban drainage system. London’s clay soils are prone to shrinking and swelling during droughts and heavy rainfall, causing ground movement that stresses and breaks aging pipes. The resulting floods can cause significant disruption, as seen in the January 2020 burst on Blackfriars Road that closed Southwark station.

An even greater risk is widespread surface water flooding, which is the highest-rated current climate hazard. Intense rainfall on hardened urban surfaces overwhelms the drainage network, causing track, road, and station closures. This risk is compounded by rising sea levels in the Thames Estuary, which can prevent drainage systems from discharging, trapping floodwater in the city.

Areas for action

• Contribute to the Thames Estuary 2100 plan updates to support the upgrading of London’s flood defences.
• Collect data during maintenance visits on transport assets most at risk from surface water flooding.
• Contribute to the Greater London Authority’s SuDS (Sustainable Drainage Systems) marketplace initiative and train project managers on the importance of incorporating SuDS into new designs.
• Explore data sharing models with water companies to improve understanding of network vulnerabilities and co-locate maintenance or upgrade works.

#3 Telecoms and other environmental risks

Key Messages

• The resilience of the telecoms network is a key uncertainty; failures could affect communications for staff, emergency responders, and the public.
• Poorly managed vegetation and green infrastructure can increase risks from storms (falling trees/leaves) and wildfires, but well-managed greening is a critical adaptation solution.
• Landslides on banksides and slopes adjacent to transport corridors, triggered by both drought and heavy rainfall, pose a growing risk to road and rail infrastructure.

Disruption to telecoms networks—operated by multiple external providers—is a medium-level risk, though scoring confidence is low due to limited engagement from the sector. Telecoms assets like data centres and street cabinets are vulnerable to flooding, while masts and cables are at risk from high winds.

Environmental interfaces also pose a significant risk. The expansion of green infrastructure is essential for urban cooling and flood management, but it must be carefully managed. An extended growing season coinciding with autumn storms can increase leaf fall on tracks, reducing adhesion and causing delays. Droughts can increase wildfire risk and cause die-off, which can damage road surfaces or block drainage systems. Similarly, the stability of slopes and banksides near road and rail lines is threatened by cycles of drought and intense rain, increasing landslide risk.

Areas for action

• Share research outputs on landslide and embankment failure to inform risk and adaptation measures for all asset owners.
• Prioritise engagement with the telecoms sector to close knowledge gaps on climate vulnerabilities.
• Develop and share best practices for the management of vegetation and green infrastructure, building on conversations with the Forestry Commission.
• Investigate co-funding models for vegetation management to mitigate shared risks from wildfires, storms, and landslides.

A collaborative path forward for a resilient London

To address the systemic and interconnected nature of climate risk, a more integrated and collaborative approach to adaptation is required. This project has demonstrated the value of combining systems thinking with stakeholder engagement to build a shared understanding of the risks facing London’s infrastructure. However, developing a complete picture and delivering effective solutions will require support from actors beyond the transport sector. To realise a climate-resilient London, long-term thinking must be further embedded in policy and investment cycles.

Areas for action

• Disseminate best practice guidance for the maintenance and management of green infrastructure, given its growing importance as a solution for multiple climate hazards like flooding and urban heat.
• Pursue greater regulatory commitment to co-ordinating cross-sectoral working groups. Making the ARP a mandatory requirement rather than a voluntary process would help address the limited convening power of a single organisation.
• Explore opportunities for co-funding adaptation projects across regulatory groups to enable multi-benefit solutions. A joint investment approval process, underpinned by a shared risk register, would deliver more effective and efficient outcomes for all.
• Standardise the use of data-sharing tools and models (such as Digital Twins) to identify pressure points across the entire system, helping to avoid redundant efforts and target investment where it is needed most.

Citation

Mott MacDonald. May 2024. Climate change and interdependency risks for London’s land based transport sector: ARP4 Interdependencies project report. London: Transport for London. https://tfl.gov.uk/corporate/about-tfl/adapting-to-climate-change