BE6 Customers reliant on electricity substations in areas at flood risk

Energy security requires a complex system to generate, store, and distribute energy. Physical infrastructure may be vulnerable to the impacts of climate change because of the potential for flooding, damage to power lines and disruption to power stations (The Scottish Government, 2011). In common with most countries, Scotland’s energy capacity has evolved as a primarily centralised network, which means that it is dependent on a relatively inflexible system of critical infrastructural assets (The Scottish Government, 2011).

Substations are critical to transmitting and distributing energy across the electricity network. Flooding coupled with the loss of power can have a severe effect on communities, particularly if other critical infrastructure services are also affected (eg water supply, sewage treatment and land drainage), and may require mass evacuation. Loss of other services that depend on electrical power, such as the emergency services and public communications (e.g. TV, internet, telephony), can also have a large impact on society (ENA, 2009) causing fear and distress to those affected (Pitt, 2008). 

Repairing substation equipment damaged by floods may take weeks, and where replacement is required the disruption may last for months (ENA, 2009).  This indicator shows the numbers of people and services at risk due to flooding of electricity substations (primary or grid) and is one of four that consider the resilience of electricity substations to flood events.

Related indicators

BE5 Electricity substations located in areas at flood risk

BE7 Substations in areas at flood risk with completed Flood Risk Assessments

BE8 Substations in areas at flood risk with completed or planned flood protection works

Severe flooding incidents occurred in England during 2005 (Carlisle) and 2007 (South Midlands & Yorkshire) highlighting that electricity substations across the UK were potentially vulnerable to flooding. These events called into question whether historic levels of flood protection would be sufficient to protect UK substations in the longer term given the projected effects of climate change (ENA, 2009).  However, due mainly to differences in topography, Scotland has not experienced the same level of river and coastal flooding as England so the increase in risk to its substations may be less severe than further south in the UK.

The projected rise in sea level and frequency of severe weather events are expected to ‘increase the severity and frequency of natural hazard threats to critical energy infrastructure, including exposure to flooding, extreme temperatures, and subsidence’ (The Scottish Government, 2011). This may increase the number of substations in areas at risk of flooding, and therefore the number of customers who are likely to be affected by flooding.

Although distribution networks are inherently resilient, specific points in the network may be at risk of flooding, either from more severe, or more frequent, flooding, which could result in more regular or prolonged interruptions to supplies for Scottish customers on a localised basis. This vulnerability represents a risk to existing energy infrastructure and will also have implications for future infrastructure plans and investments (The Scottish Government, 2011).

New standards relating to the resilience of electricity substations (ETR138) will increase the level of substation protection against flooding (ENA, 2009), thus reducing the risk of increased flooding.

The data for 2012-2013 provide a baseline number of customers reliant onmajor electricity substations located in areas at risk of flooding. There are two competing patterns to consider. Climate change projections include sea level rise and more frequent severe weather events, both of which may place more major substations at risk over time, consequently increasing the number of customers reliant on ‘at risk’ substations. However, the implementation of new guidelines on the security of primary and grid substations (ETR138) will ensure that the flood resilience of existing major substations is increased. Additionally, future developments will not be located in areas at high risk of flooding. It is therefore predicted that although flood risk may increase, the implementation of ETR 138 should ensure the security of the electricity network, thereby stabilising or decreasing the number of customers at potential risk of supply loss due to flooding of major substations.

Currently, the assessment of major electricity substations at risk of flooding reflects only fluvial and coastal flood risk; because these are the only data SEPA provide (ENA, 2009). 

This suggests that the total number of major substations at risk of flooding, and consequently the number of customers dependent on this category of substation, may be higher than reported once additional sources of flooding are considered. The latest iteration of SEPA flood maps (SEPA, 2015) include pluvial flooding, and it is recommended that this indicator should be developed as information about additional sources of flooding become available.

A further limitation is that ‘the number of customers reliant on electricity substations at risk of flooding’ metric does not differentiate between domestic and industrial/commercial customers. The figure of 260,503 customers dependent on 43 substations includes two substations that each serve only one customer, but loss of service to these two substations may have a wider impact, as the customers that they serve also supply services to the public. Similarly, loss of power to the critical customers reliant on these major substations would also have a more severe societal impact than the numbers alone might suggest. Critical customers include hospitals, underground stations, pumping stations and sewage works.