Analysis: Network operators seek novel solutions to weather threats
Unprecedented levels of wind and rain have led to failures in the UK’s power and transport networks, raising questions about the nation’s critical national infrastructure.
Winter storm season came early for Britons as the St Jude storm knocked out power in more than 850,000 homes and shut down rail services across the south of England in late October 2013. On 5 December the worst North Sea tidal surge since January 1953 hit eastern England, though flood defences built in response to the historic surge largely did their job.The festive season brought no respite. December 2013 was the windiest on record, with 70mph winds that led to power cuts for about 750,000 properties and left thousands flooded.
Since then a conveyor belt of storms has continued to dump huge amounts of rain on an already sodden England. Meteorologists have blamed the jet stream, an air current that flows around the northern hemisphere, which appeared to become stuck over Britain.
The Environment Agency (EA) has come under fire and much column-space has been devoted to whether successive governments have invested enough into flood defences, but as executive director of flood and coastal risk management at the EA David Rooke explained, while 6,500 properties were flooded this winter more than 1.3 million were protected. “No government across the world can protect all people, in all property from all flooding,” he said.
The Pitt Review into the 2007 floods suggested more of the UK’s limited resources should be diverted to early warning. The agency teamed up with the Met Office to create the Flood Forecasting Centre, which uses the Met Office’s supercomputer to forecast all forms of flooding with greater accuracy and longer lead times. Tidal forecasts for the east coast are now up to five days ahead, according to Rooke.
While longer lead times have made it easier to prepare for extreme weather, they can only help so much and the Pitt Review placed a burden of responsibility on infrastructure operators. Although thousands were left without power in 2007, it was near-misses at Walham substation, which serves 500,000 people in Gloucestershire and south Wales, and a number of electricity substations around Sheffield, that brought home the vulnerabilities of this critical facet of the UK’s infrastructure.
There has now been a massive investment across the industry. The National Grid is midway through a £100m programme running until 2020 that aims to protect its assets against even the rarest flooding events. As well as permanent flood defences, the company also relies on more than 2km of mobile barriers and eight high-volume pumps that can move three tonnes of water a minute. “We have had a few challenging days but our system has been fantastically resilient,” said head of network engineering Jon Fenn.
Despite its area being one of the worst hit, Western Power Distribution’s policy manager Paul Jewell said precautions the firm has taken have paid off. The focus has been on coastal and river flooding, but last year the EA began to publish information on surface water and rain-related flooding. Jewell said this will be an area of focus for distribution network operators (DNOs) in the next Price Review Period.
Nevertheless, DNO bosses were accused of “complacency” by Commons Energy Select Committee chairman Tim Yeo due to their slow reactions to the wind damage that caused the Christmas power cuts. In response, Basil Scarsella, chief executive of UK Power Networks, which covers east and south-east England, said the severity and duration of the storms had overwhelmed the DNOs’ normal mutual aid arrangements.
The rail network has been most visibly disrupted by the extreme weather. Network Rail chief executive Mark Carne gave the Commons Transport Select Committee a preliminary cost estimate of around £170m, with more than 280 sites affected. The damage has been caused by floods and groundwater, landslips and coastal erosion, notably the collapse of the sea wall at Dawlish that severed the rail link to south-west England.
Carne said Network Rail will issue a report on network resilience in September, but that the traditional approach to using historical weather data to assess the future resilience of railway infrastructure would need to be revised. “We need to reconsider the flood defences and coastal defences,” he told the committee.
The case of Dawlish highlights the unpredictable nature of recent extreme weather, which Professor Jim Hall, director of the Environmental Change Institute at Oxford University, said means “we are still in a mode of discovery by disaster”. The situation is made worse by complex interdependencies between different infrastructure.
He said: “Each utility is regulated in a different way and although resilience is being underlined in the role of the regulators, it isn’t always the number one priority.”
These interdependencies can cause what are known as cascade failures – where breakdown of one component in a system causes failures in other areas. A prime example is that of Gatwick Airport on Christmas Eve, where flooded electricity sub-stations caused a power cut at the north terminal that forced the airport to cancel dozens of flights.
According to the IET’s Professor Will Stewart this interconnectedness is a double-edged sword. “It makes the systems smarter and more resilient, but also means that extensive damage to one system can cause problems with others,” he said. “The real challenge will be to find new ways to plan and manage the integrated system.”
One suggestion comes from Cardiff University’s Professor Roger Falconer, who points to a proposed tidal lagoon at Bridgwater Bay in Somerset. The project could generate up to 3.6GW of electricity as water passes through turbines, but more importantly the lagoon could shield the coast from storm surges as well drop the tidal level to create a sufficient gradient to drain the Somerset Levels when rivers are in danger of flooding.
Dual use of infrastructure was highlighted by the Engineering the Future group in its 2011 report ‘Infrastructure, Engineering and Climate Change Adaptation’, which also called for a greater focus on systems thinking and breaking down silos. Resilience work in one sector is wasted, it pointed out, if it depends on another less well-protected sector.