The struggle to manage climate change
A seven-day forecast is one thing. Trying to grasp the complex relationship between weather and climate is another matter entirely.
Network Rail has been trying to fathom the consequences of climate change, as far as this can be predicted. Project Sponsor Alex Hinshelwood contributed to a report that first appeared in 2019, analysing the past and trying to make an educated guess about the future impact of rising temperatures.
Rainfall and flooding were responsible for the largest proportion of weather-related delay minutes on the Welsh rail network (27.8%), from 2006-07 to 2018-19. Climate change is expected to increase the frequency and severity of river flooding and rainstorms. There will be more frequent and intense summer rainstorms.
Guidance from the Environment Agency, relying on projections from 2009, suggests that rainstorms could be 10% more intense by the 2050s and 20% by the 2070s.
Dryer summers, when they arise, bring their own problems. Lower rainfall means that drains aren’t ‘self-cleansed’ and winter deluges can cause them to fail. That means a thorough drains maintenance schedule is essential, especially on riverside lines.
NR has produced its own guidance relating to increased river flows for all the Welsh catchments. Some of this makes for alarming reading - for instance, it predicts that flows in the Severn will rise 25% by the 2050s and 35% by the 2080s, and in West Wales by 25%40% by the 2050s and 30%-75% by the 2080s. Neither the scale nor the disparities make future planning easy.
Around 34 miles of the Wales Route’s coastal lines are vulnerable to overtopping, coastal erosion and storm surges. The risk of wind and flooding means stations and other buildings could have to close.
NR aims to use an established coastal weather forecasting system and asset monitoring to manage vulnerable locations. It also intends building on its current coastal and estuarine asset management strategy.
Coastal and inland flooding may have an impact on signalling location cases, track circuit equipment and cables. One remedy for the former, the report suggests, would be for location cases to be installed on raised platforms in high-risk areas.
From 2014-19, vulnerable earthworks across Wales bore the brunt of prolonged and heavy rainfall. In January 2018, 50 tonnes of mud and rock swept across the track at Dinas Rhondda on the line between Porth and Treherbert, causing a four-day closure. Extensive work was needed to improve the stability of lineside cuttings.
Several landslips occurred in October 2018, following Storm Callum. Track bed was washed away at Pontarddulais and Llandeilo, requiring replacement of 300 tonnes of ballast.
It was a destructive autumn all round, during which damage was caused to 21 of TfW’s 127-strong train fleet. Four months later, in February 2019, Storm Erik rolled in, flooding and closing the line near Nant-yDerry (Monmouthshire).
The Wales Route has a high level of vegetation. Removing lineside trees can reduce disruption, but “third-party” leaves also create “railhead contamination”, the report says.
Some factors are beyond NR’s control, such as change of use of adjacent land, adjoining boundaries and environments in poor condition.
NR plans preventative maintenance to repair low/medium-risk defects before these become a major problem. This should reduce the need to replace or carry out major works to “high risk or poorly performing assets”.
Foundation checks (scour assessments) of key structures such as Cegin Viaduct, Bodorgan Viaduct, River Towy Viaduct and Severn Viaduct have been carried out, along with improvement to drainage systems around locations such as Talerddig cutting, Caerphilly Tunnel north portal, Severn Tunnel eastern portal and Bangor Tunnel.