Risk/opportunity:(from the Climate Change Risk Assessment for Scotland 2012):
FL7/24/27 Flooding of non-residential property
SCCAP theme: Buildings and infrastructureSociety
B2: Provide the knowledge, skills and tools to manage climate change impacts on buildings and infrastructure
2010-2012: 45 of 250 water treatment works (18%) lie within SEPA’s 0.5% Annual Probability indicative coastal and fluvial flood boundaries (but have not experience historical flooding issues).
Although there are additional treatment works known to have experienced flooding, the number could not be verified at the time of study.
- Clean water is a basic requirement, and security of water services is crucial to society.
- Some Scottish water treatment works (WTW) have already experienced flooding, and others may be at risk now and in the future due to climate change.
- Until 2002, water assets were managed at regional and local levels, with case-by-case management. From 2006 Scottish Water has undertaken flood risk assessments at a national level, followed by interventions where required
- The Scottish Water Asset Register includes wastewater treatment works, water treatment works and pumping stations. The methodology for assessment of asset flood risk to any of these commissioned by Scottish Water are broadly similar.
The ability to provide safe drinking water is a fundamental requirement of society. Understanding the risk to water services is important for Scottish Water, in order to inform both central strategic objectives and local asset management plans. Scottish Water has responsibility for more than 250 water treatment works, as well as for around 1,380 service reservoirs and water towers and almost 600 water pumping stations.
The infrastructure supporting the treatment and delivery of water may be vulnerable to climate change impacts due to flooding (Scottish Government, 2011). Flooding of water treatment assets can arise due to inundation via fluvial, coastal or pluvial sources. Failure of the water treatment function arises principally due to the impact upon critical equipment (particularly electrical) rather than due to impact on process.
In 2012 Scottish Water undertook a Flood Risk Assessment for 45 water treatment works, identified as a priority from a total of more than 250. From this, appropriate interventions were identified and addressed through a coordinated programme of capital investment and maintenance (Scottish Water, 2012a).
Service resilience is an increasing focus for Scottish Water, covering a range of factors, of which climate change is one. The approach is set out in their 2015-21 Regulatory Business Plan (Scottish Water, 2014).
Between 2006 and 2010, Scottish Water worked to improve their understanding of flood risk across the water asset base. Raw water storage, raw water pumping stations, water treatment works, treated water pumping stations, wastewater pumping stations and wastewater treatment works were examined in a desk based study using SEPA’s 1:200 flood risk maps (coastal & fluvial) and anecdotal records of surface water flooding of assets. This information was consolidated into an asset flood risk register.
Following the introduction of the Flood Risk Management (Scotland) Act 2009 and the subsequent release of SEPA’s National Flood Risk Assessment 2011, Scottish Water was able to refresh the way in which it assesses the flood resilience of its asset base. In 2012, Scottish Water commissioned the development of an asset selection methodology(Scottish Water, 2012a), with the aim of better understanding the risk exposure and intervention options for a number of water treatment works and other assets. This methodology identified 45 water treatment assets as requiring a more detailed flood risk assessment (defined on the basis of sites that lay within SEPA’s 0.5% annual probability indicative coastal and fluvial flood boundaries but that had not already been flooded) (Scottish Water, 2012b). It is possible that, at the time of this study, there were additional treatment works known to have experienced flooding however, this information could not be verified.
It is widely accepted that climate change will bring an increase in sudden and intense rainfall, coastal flooding will become more frequent and more severe, and sea-level will rise (Scottish Government, 2009). More specifically, climate change will influence catchment response through an increase in peak rainfall intensity, thus also increasing peak fluvial flows. With respect to coastal flooding, climate change will bring an increase in both sea levels and in storminess, making those assets located nearer Scottish shores more susceptible to waves and breaches of defence crest levels. This overtopping of coastal defences may result in increased flood risk due to ponding (as influenced by topography) or may result in structural problems due to the ingress of seawater from coastal spray.
Scottish Water is now developing a more risk-based approach that focuses on critical assets in order to prioritise the management of flood risk.
The data for 2010-2012 offer a baseline to measure the number of water treatment works located in areas at risk of flooding. However, this is based only on risk as identified through location mapped to SEPA’s 0.5% Annual Probability indicative coastal and fluvial flood boundaries. In other words, it is simply a measure of assets that lie within the flood risk area. The indicator and data do not confirm the outcome of flood risk assessments; neither do they yield detail on interventions to manage the risk. Use of this data should hence be undertaken with care.
Dixon and Tawn (1997). Estimates of extreme sea conditions: spatial analyses for the UK coast. POL report 112.
SEPA (2010). Technical Flood Risk Guidance for Stakeholders, 2010, Version 6.0. Ref SS-NFR-P-022.
Coastal flood boundary conditions for UK mainland and islands. Environment Agency, 2011.
SEPA (2011). National Flood Risk Assessment. Available at: http://www.sepa.org.uk/flooding/flood_risk_management/national_flood_risk_assessment.aspx
Scottish Government (2009). Scotland’s Climate Change Adaptation Framework (SCCAF). Water Resource Management Action Plan. Available at http://www.gov.scot/Resource/Doc/295166/0091322.pdf
Scottish Government (2011). Scotland’s Climate Change Adaptation Framework (SCCAF). Energy Sector Action Plan. Available at: http://www.gov.scot/Resource/Doc/175776/0114907.pdf
Scottish Water (2012a). Asset Flood Resilience, Asset Selection Methodology, SW Ref: 401191-0000-20-GEN-0001, July 2012.
Scottish Water (2012b). Asset Flood resilience, Flood risk assessments. Hydrological and hydraulic modelling strategy to assess flood hazard at asset sites. SW report reference: 401191-0000-20-GEN-0003, 2012.
Scottish Water (2014). Strategic Projections and Business Plan 2015-2021 http://www.scottishwater.co.uk/about-us/publications/strategic-projections
This indicator was compiled by Professor Lynne Jack and colleagues at Heriot Watt University with input from Scottish Water. The data on assets at flood risk was provided by Scottish Water.
Katherine Beckmann, Heriot-Watt University / CXC contributed to this indicator.