The damage and disruption caused by flooding cannot be underestimated, as the experience of recent years in the UK shows. Far from being complacent, National Grid has been investing in the resilience of its network. Douglas Dodds, Environment Resilience Specialist – Natural Hazards, describes what National Grid is doing to ensure security of supply.
Nobody, least of all National Grid, wants the lights to go out because of flooding. Security of supply is very important to us – we have a duty to British energy users to do everything we can to prevent the loss of power.
We’re in the sixth year of a programme of improvements designed to mitigate the risk of flooding, as well as to cope with changes predicted from climate change. The changes already carried out appear to be working. Last winter, none of our substations were flooded, even though in some cases, such as Walham in Gloucestershire, the surrounding areas were under water.
Storms and flooding
It’s helpful to think of the UK power distribution network in terms of the road network. Our high voltage lines and substations are the motorways of our network and need to be very resilient.
Storms and flooding often come hand in hand and high winds can often take out the poles and wires of the local distribution networks, leading to loss of power to people’s homes. That’s why it’s even more important that the national transmission infrastructure that we own and manage can stand up to adverse weather.
The events of recent years, notably 2007, have shown where the power system is most vulnerable to the risk of flooding. We take that risk seriously, and are about halfway through a programme of works agreed with the Department of Energy and Climate Change (DECC) and our regulator, OFGEM, to improve flood defences, primarily at our electricity substations.
Through our involvement on the Energy Networks Association (ENA) Resilience and Flooding Task Group, we know that the distribution network operators (DNOs) are also working hard to increase their flood resilience, too.
Sites at greatest risk
As you’d expect, the sites at greatest risk were prioritised before work began and have all had their risk level cut at least by half through a combination of permanent, temporary and portable measures.
Our £158m flood defence investment programme, which is focused on electrical substations, began in 2008 and runs to 2021. We’ve spent £28m so far on mitigating the risk of flooding on most of our high-risk sites. This work has lowered the risk level at these sites to 1-in-1000 – down from the 1-in-100 band that independent assessors had reported, following established criteria of the insurance industry.
Some of this investment went into purchasing the 1.7km of mobile flood defences and pumps that we now have on permanent standby – and we’ll be spending an extra £600m to bring that up to £2.4km by early 2015.
This mobile system can be deployed as soon as a flood warning is issued to give us a temporary measure of flood resilience where needed, until permanent solutions can be implemented through our investment programme.
We’re also assessing the needs of sites other than substations under a further £11.2m budget, applying the lessons learned from the mitigation of risk to substations to other above-ground assets. Typically any critical element of these assets is 2-4 metres above the ground and unlikely to flood. However, we are also looking at access, erosion issues and other factors with a view to protecting our property.
Deciding on priorities
Many factors influence what work we carry out and when. Among them are the longer-term plans for site redevelopment and whether flood mitigation can be combined with that work. Progress may not therefore be obvious to an outside observer. But we see this as following a sensible, cost-effective path rather than taking hasty, and ultimately more expensive, decisions.
The most suitable solution is determined on a site-by-site basis. In some cases, a permanent barrier of sheet piling topped with concrete can be installed, although it is an expensive option. Other sites may only need very minor works, such as expansion of drainage ditches or it may be decided that only certain buildings need to be protected on a particular site.
Environmental considerations are always part of our decisions. All planning applications contain studies that show our protective measures will not become a cause of flooding elsewhere.
Behind the scenes, we maintain round-the-clock vigilance. Information from the Environment Agency (EA) on flooding goes directly into our electricity control room to help us manage our systems. In addition, we also monitor the weather forecasts – as well as current and projected hydrological conditions – for potential risks. This often makes us aware of risks before the EA releases its flood warnings.
Our determination is always to take the best investment option for our UK customers without exposing them to unnecessary risk – and to do all within our power to keep the nation’s lights on.
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