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Weathering the climate change storm

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At the start of November, Network Rail released dramatic video footage of a section of railway (pictured above) which had been left suspended in mid-air following a torrential downpour. Flooding near to the village of Pontrilas, south Herefordshire, on the Marches line between Abergavenny and Hereford, led to parts of the track foundations being completely washed away and left the railway in desperate need of repair.

“We understand how disruptive the closure of the Marches line will be to passengers and we’ll work as fast as we can to get it back up and running again,” said a Network Rail spokesperson, announcing the forced closure of this key route in and out of Wales. “Although we always plan for extreme weather it’s nearly impossible to mitigate such heavy rainfall of the like we’ve seen over the last 24 hours,” they added.

One battle in a bigger struggle

Despite the continuation of difficult weather conditions, engineers worked day and night to repair the railway. Around 100m of track was replaced, 300 tonnes of foundation material and 600 tonnes of ballast laid, and drains, signalling, power and telecoms cables inspected. As a result, a week later on November 2 the line re-opened – a day earlier than had been predicted.

While rail replacement buses helped to minimise disruption during the line’s closure, the incident was a reminder of just how vulnerable the railway is against the destructive power of extreme weather. Looking past the impact on performance and subsequent costs, had a passing train driver not reported the fast-flowing water that went on to cause the washout, there could have been grave consequences.

The damage at Pontrilas has now been fixed, but the incident is just one battle in a bigger struggle facing Network Rail. Rising temperatures across the globe are leading to more extreme weather conditions that can prevent trains from running and cause damage to essential railway assets. In June, hundreds of East Midlands Trains passengers were left stranded on trains trapped by a landslide near to Corby and, the same month, services on some lines were left running to restricted speed limits as hot weather threatened to bend or buckle the track.

“The very significant impacts that we already experience are likely to become more frequent and intense,” said Lisa Constable, Network Rail’s weather resilience and climate change adaptation strategy manager, who oversees the organisation’s long-term work to embed climate change risk in policies and procedures.

“When you look at the climate change prediction for the UK, you’ll see that we’re expecting to see hotter, drier summers and warmer, wetter winters with – when it does rain – the rain becoming more intense and, therefore, the risk of flash flooding and the associated impacts on the railway from lightning and high winds becoming more severe.”

Number crunch

Looking at Network Rail data for weather-related incidents in England, Scotland and Wales, the occurrence of wind, snow and flooding on the network has led to the most train delays between 2006/07 and 2017/18, while fog, heat and lightning has contributed to the least amount of delay minutes to train services, respectively. Other weather-related issues include: poor adhesion, most commonly caused by leaves on the line; cold temperatures; and subsidence.

On average across this period, subsidence has led to the greatest delay per incident at 650 minutes and adhesion the least amount of a delay at 12 minutes per recorded incident. Nevertheless, the far higher frequency of poor adhesion events on the railway means it is a bigger problem for Network Rail than subsidence. 

A fleet of 61 specialist trains and vehicles were put on standby to minimise the impact of the thousands of tonnes of leaves that fell onto the railway in the autumn, while engineers continuously monitor the sites most prone to landslips from afar with motion sensors and CCTV to detect soil and rock movement.

Lisa said that, in terms of delays and cancellations, weather-related incidents are costing Network Rail £100 million a year – and that doesn’t include the wider impact to the railway or economy, which could be as high as three times that figure. Looking at the Dawlish Sea Wall, when it was hit by a devastating storm in 2014 and the railway into the South West was subsequently for eight weeks, estimates put the impact on Cornwall’s economy at anywhere between £1 million a day up to £1 billion in total.

Serious threats

While extreme weather continues to cause significant disruption on the network, the railway has been fortunate that it hasn’t led to any serious accidents in recent years. Not since September 2016, when a landslip at Watford caused a train to collide with a derailed train, or before that in December 2015, when subsidence of Lamington viaduct resulted in serious deformations to the track, have there been serious reminders of the potential consequences.

“We learn lessons every time there’s an incident,” said Lisa. She explained that recent efforts to mitigate the impact of weather have been focused on hot weather because of its impact on performance this summer but that it’s her job to make sure other work to strengthen the railway’s weather resilience isn’t sidelined.

She added: “From an asset capability perspective and a safety perspective, I think there is a significant risk of earthworks and the potential for subsidence or landslide and flooding, particularly as we get more intense rainfall, and that safety risk from a derailment perspective.

“In terms of big-ticket things, as sea level rises our coastal infrastructure is going to come under even more pressure. The example at Dawlish is a very difficult and well-known example but there are other areas around the coast where we may not have experienced any big failures but we need to look at what the potential for that could be as storms get worse going forward.” 

Mitigating and managing risk

Over the last 10 years Network Rail has increased its efforts to strengthen the railway’s weather resilience in order to reduce disruption. As well as the introduction of technologies such as condition-monitoring devices, in a change of approach, all of Network Rail’s renewals, maintenance and enhancement work in CP7 will take into account future weather conditions, meaning the railway will gradually adapt to the impacts of climate change.

For example, there is a new requirement for projects that pass through the GRIP process to undertake a climate change impact assessment, the findings from which will inform development options to boost weather resilience. 

All of the routes produced weather resilience plans for CP5 and each is now producing fresh plans for CP6 – Wales being one of two routes to have already published its plans online. In its report, the Wales route reflects on flooding being its biggest problem in terms of extreme weather over the past 12 years.

While, reacting to the recent washout on the Marches line, a Network Rail spokesperson painted a bleak picture when they said it is “nearly impossible to mitigate such heavy rainfall”, the new report sheds some light on some of the route’s approaches to reducing the impact of flooding. This includes work to stabilise lineside cuttings, replace failed assets with something better, changing station canopy designs, improved drainage at high-risk sites and pre-emptive cleanses of those assets when extreme weather is forecast.

Network Rail as a whole also produces its own Weather Resilience and Climate Change Adaptation Strategy, which aims to ensure that assets will be better able to withstand the impact of current and future weather events, and also will be able to recover more rapidly when they occur.

Despite these efforts, Lisa is adamant that not enough is being done. While Network Rail has become better at managing day to day weather, the longer term focuses Lisa works on – such as building on-the-ground resilience – takes time because of the five-year investment programmes and the difficulty in encouraging expenditure now to save money further down the line.

She explained: “We haven’t had an increase in resources to the extent that is required. However, people are much more aware of potential climate change risk and there has been a shift in willingness to do something about it.”