The latest U.K. Climate Projections 2009 (UKCP09)¹ indicate that rising sea levels and increasingly severe and frequent rainstorms mean the risk of flooding will increase for people, communities, and key infrastructure such as roads, railways, power substations, and water treatment plants.

This article focusses on some of the more extreme weather events, particularly flood events since these have posed perhaps the most significant challenges for U.K. infrastructure in recent years, and the initial steps being taken to adapt to these challenges.

The U.K. is not alone in this experience of extreme weather, a U.K. Government Office for Science report, “Measuring the Human and Economic Impact of Disasters”, gives a global perspective on natural disaster trends over the last century and notes that between 1961-1970, one in 138 people worldwide were affected by natural hazards compared to one in 28 in the decade 2001-2010, and the economic costs associated with these natural disasters increased more than eightfold.

Stormy Weather in the U.K.

The U.K. has certainly experienced some unusual weather events in the last decade or so as detailed by the U.K. Met Office and as highlighted by year in Figure 1.
Some of the more significant flood events are briefly summarised below and the locations are indicated on the map in Figure 2:

• Autumn 2000 - the wettest since records began in 1776, with 489 millimetres (mm) of rain. Flooding in York, Shrewsbury, Lewes, Uckfield, and Maidstone affected more than 10,000 households and caused damage in excess of 1 billion GBP.
• Summer 2007 - the wettest summer on record. Yorkshire suffered many road and rail closures, power cuts, and evacuations, with Sheffield severely hit. Other areas heavily affected include Hull, Gloucestershire, and Worcestershire. Around 48,000 households and 7,300 businesses were flooded and the damage caused was in excess of 3 billion GBP. Damage to critical infrastructure was estimated at over 650 million GBP.
• November 2009 - the heaviest rainfall ever in the U.K., 316.4mm in 24 hours. Flooding was concentrated in Cumbria including Cockermouth, Keswick, Workington, Kendal, and Ulverston. Four people were killed as a direct result of the flooding.
• December 2013 - the stormiest since 1969. On 5 December, Scotland’s rail network shutdown and 100,000 homes were without electricity. On the 6th of December, the east coast of England experienced the highest tidal surge in 60 years.
• January 2014 - England’s wettest January since records began in 1776. Southern England had 175mm of rain from 1-28 January. Flooding was severe in the Somerset Levels, the Thames Valley, Worcestershire, and Herefordshire. Over 5,800 properties flooded and the damage caused was in excess of 0.5 billion GBP.

Some Challenges Posed by Flooding to U.K. Infrastructure

Electricity Supply

• Summer 2007 - floods caused 40,000 people in Gloucestershire to lose their electricity supply for 24 hours. Walham substation in Gloucestershire was close to being inundated; if this had happened 500,000 people would have lost their electricity supply. In Yorkshire four major electrical substations and 55 secondary substations were flooded, affecting the electricity supply to 130,000 people.
• December 2013 - from the 24th to the 27th storms and high winds caused 50,000 households to lose their electricity supply.
• 12 February 2014 - 130,000 homes lost their electricity supply.

Water Supply

• Summer 2007 - the flooding of the Mythe water treatment plant in Gloucestershire caused the loss of water supplies to 350,000 people for up to 17 days.

Roads

• Summer 2007 - 10,000 people were stranded in their cars on the M5 motorway in Gloucestershire.
• November 2009 - Flooding in Cumbria caused six road bridges to collapse, cutting off communities.
• Winters of 2012 and 2013 - Many local roads were inundated and impassable during the flooding of the Somerset Levels.

Railway

Summer 2007 - heavy rainfall resulted in embankment landslips and flooding on the railway.

Winter 2013/2014 - the floods of 2013/14 inundated large areas of Somerset for months, severing railway communications in North Somerset and washing away the railway line at Dawlish on the Devon coast. Railway service for passengers west of Exeter with the rest of the country was discontinued for 2 months while the line was repaired. Coastal railway lines in Wales and Cumbria were also closed for weeks following damage from storms coinciding with high tides. Inland railways at various locations around the country were also closed for repairs due to several large scale embankment landslips following very heavy rainfall.

Improving the Resilience of U.K. Infrastructure to Flooding

An example of how infrastructure and flood warning improvements can dramatically reduce damage and save life was experienced on the 6 December 2013 when the east coast of England experienced the highest tidal surge in 60 years. Warnings were given and thousands of people were successfully evacuated, preventing the terrible loss of life experienced in the 1953 flood event (see Network Issue 72, “United Kingdom Coastal Monitoring and Forecasting”, by Neil Fanning which discusses improvements to coastal flood forecasting).

The flooding experienced in the last decade or so has challenged the U.K. to make further improvements to the resilience of our infrastructure. The U.K. government invited independent reviews following the Easter 1998 floods (by Peter Bye) and again following the summer floods of 2007 (by Sir Michael Pitt). The Pitt Review made many recommendations, including the development of a national standard of resilience against flooding.

Sector Resilience Plans

In 2009, the government initiated the development of Sector Resilience Plans (SRPs) for the U.K.’s national infrastructure, defined by the government as “those facilities, systems, sites, and networks necessary for the functioning of the country and the delivery of the essential services upon which daily life in the U.K. depends”.

Sector Resilience Plans are based on the relevant risks to this infrastructure as identified in the National Risk Assessment (NRA), which provides a government assessment of the likelihood and potential impact of civil emergencies (including the risk of terrorism, major accidents, and natural hazards) that may directly affect the U.K. over the next 5 years. An unclassified summary is issued annually. The Sector Resilience Plans are produced annually and present the risk and vulnerability of each infrastructure sector², the desirable level of resilience, a programme of actions for achieving the desired resilience level, and methods of reporting the progress towards achieving the target resilience.

Findings of Sector Resilience Plans

Some of the early findings of the Sector Resilience Plans focused on flooding for the following sectors are detailed below:

Energy

Electricity supply – electricity transmission and distribution companies plan to provide a target level of protection of 0.1 percent annual flooding probability (1 in 1000 year standard) for critical assets. A similar approach is being taken for gas supply assets.

The U.K.’s Committee on Climate Change issued the Adaptation Subcommittee Progress Report 2014, “Managing climate risks to well-being and the economy”, which notes the following:

• By 2013, flood risk assessments had been completed for nearly 80 percent of the major distribution substations identified as being at flood risk. The remaining substations are due to have flood risk assessments completed by 2015.
• Progress with the implementation of flood protection measures generally appears to be on track, with nearly 20 percent of the 300 major substations located in areas susceptible to river and coastal flooding having already benefited from protection, and most of the remainder on course to have measures implemented by 2020.

Water

Water supply – the water sector is vulnerable to flooding due to the position of assets close to rivers and lakes. In 2009, the water regulator Ofwat allowed water companies to increase charges to customers to protect assets to 0.5 percent annual flooding probability (meaning protection to a level that has a 1 in 200 chance of being equalled or exceeded each year).

Legislation in the form of a new Water Act was introduced in May 2014 specifically to:

• reform the water industry to make it more innovative and responsive to customers;
• increase the resilience of water supplies to natural hazards such as drought and floods;
• bring forward measures to address the availability and affordability of insurance for those households at high flood risk; and
• ensure a smooth transition to the free market over the longer term.

Transport

A large range of transport options are available (road, rail, aviation, and shipping), and these can provide alternatives in the event of disruption to part of the strategic transport network. Following the significant damage to railway infrastructure during the winter 2013/2014 storms and flooding, the railway sector set up weather resilience and climate change adaption plans for major routes, and a special study was conducted following the destruction and repair of the coastal line at Dawlish (Figure 3). Further reviews have been undertaken following the winter 2013/2014 flooding including the July 2014 Transport Resilience Review titled “A review of the resilience of the transport network to extreme weather events”. The following is a selection of recommendations from this review:

Strategic Road Network

Given the importance of drainage to resilience, the Highways Agency (HA) should complete its drainage asset inventory. The review also recommends that the HA should consult with freight operators about restricting high-sided vehicles from travelling on exposed sections of the strategic road network during high winds, so that these locations can be kept open longer for all other users. It further recommends that the HA works with the Met Office to improve wind forecasts for the benefit of lorry (truck) fleet operators.

Local Roads

It is recommended that local highway authorities identify a ‘resilient network’ to which they will give priority, in order to maintain economic activity and access to key services during extreme weather. In locations where formal reviews of the winter’s events have been held, local authorities should ensure that recommendations are enacted. In those locations that were not affected, local authorities should nevertheless continue to prepare for future extreme weather.

Railways

The correlation of earthwork slips with heavy rainfall derailments is shown in Figure 4, reproduced from the Transport Resilience Review published in July 2014.
On engineering structures, the review recommends that Network Rail:

• continues to trial newly available condition monitoring and slope stabilisation technologies; and
• develops plans to raise track heights and raise lineside equipment cabinets above track level on sections of track at risk of flooding, as part of its new Route Resilience Plans.

 Lineside trees were found to be a major factor in the winter 2013 disruption and it is recommended that Network Rail:

• develops a ten-year strategy to significantly reduce the number of trees, particularly those posing a risk to the railway and its users, and the overall level of vegetation.

WSP

WSP has supported the U.K. Environment Agency with a range of real-time system projects over the past 20 years, including the following:

telemetry data gathering (see Network Issue 45, “Telemetry and Forecasting Systems for Managing Rivers and the Environment” by Alan Knott);
weather radar visualisation system;

the specification and procurement of the National Flood Forecasting System and the development of flood forecasting models for the Southern Region (see Network Issue 77, “A Forecasting Modelling System to Help Protect the South East of England from the Impact of Flooding”).

Recent examples of WSP teams working with clients to examine opportunities to improve infrastructure resiliency include:

Highways Agency 2009: A consortium, including WSP and the U.K. Met Office, helped to develop the Highway Agency climate change adaption framework including an adaptation model which provides a framework for systematically managing the impacts of climate change.

Dorset County Council in 2012: WSP was appointed to design and supervise ground investigation and subsequent slope stabilisation measures for the steep slopes above both portals of the U.K.’s oldest road tunnel at Beaminster.

Network Rail in 2013-2014: WSP undertook the investigation, design, and submission of whole life cost remediation proposals which were accepted without rework by Network Rail for fourteen railway earthworks (twelve embankments and two rock cuttings) across Kent, Sussex, and London, which had become substandard as a result of movements through either displacement or weathering.

The U.K. Environment Agency in 2013: WSP collected information on climate change impacts to U.K. industry sectors, including agriculture, forestry, business and services, the built environment, health and wellbeing, local government, infrastructure, and the natural environment. The purpose of this work was to identify how much relevant information each sector could access, whether they were in a position to use it to make appropriate resiliency decisions, and how to improve the Environment Agency ‘Climate Ready Support Service’ to better serve those particular sector needs.

Transport for Greater Manchester (TfGM) in 2014: WSP assisted TfGM project managers by developing a toolkit that (among a number of other sustainability and whole-life costing topics) prompted them to consider the potential impacts of flooding and climate change by asking the scheme designers key questions such as: “Have climate change impacts been considered in the design of your asset?” and “How have you adapted the design of your asset to prepare it for the likely impacts of climate change?”

Network Rail in 2015: WSP assisted Network Rail in improving its prediction and response to adverse weather events by helping re-write the structural and a wind codes of practice. These make use of a wind speed weather map and now include a U.K. weather map for ice and snow prediction.

Acknowledgement

The author would like to thank the following WSP staff: Alan Knott for his encouragement and helpful comments on early drafts of this paper, Tim Danson for sharing recent sustainability team project references, John Morris and Mungo Stacey for sharing a reference to a recent Network Rail project, Ian King for sharing a reference to a project for Dorset County Council, Adrian Dolecki for sharing a reference for embankment remediation design for Network Rail, and Andrew Porter for sharing a reference for the Highways Agency Climate Change Framework project.

¹UKCP09 is the fifth generation of climate change information for the U.K., and its projections are based on a new methodology designed by the Met Office. Climate science and computer modelling have advanced significantly - UKCP09 reflects scientists’ best understanding of how the climate system operates, how it might change in the future, and allows a measure of the uncertainty in future climate projections to be included.
²U.K. national infrastructure is categorized into nine sectors: communications, emergency services, energy, finance, food, government, health, transport, and water.