The impact of flooding on bridges and other transport infrastructure in Cumbria - Transport Committee Contents

Memorandum from the Environment Agency (BIC 07)


  Floods can cause serious damage to important energy, water, communication and transport infrastructure. These impacts were demonstrated in Cumbria during November 2009 following unprecedented levels of rainfall. Our gauging station at Seathwaite Farm recorded 314mm over the 24 hours up to 1am on Friday 20 November—a record for the UK. The rain fell on already saturated ground and this resulted in severe flooding in Cumbria. The flooding caused the destruction of two large road bridges in Workington.


  1.1  The Environment Agency is the main delivery body for the management of flood and coastal erosion risks in England and Wales. Our responsibilities include carrying out and funding works that reduce flood risk from rivers and the sea, providing flood warnings to the public and emergency responders, and helping people understand their flood risk and to take appropriate action. We provide government with a strategic overview across all sources of flooding and coastal erosion in England, and assist the Welsh Assembly Government to take a similar approach in Wales.

  1.2  The Environment Agency provides information on flood risk and advises on the impact of any proposed mitigation measures. Our Catchment Flood Management Plans provide high level information on critical infrastructure by identifying individual sites with a greater than one in 100 year chance of flooding.

  1.3  Service operators are best placed to assess the resilience of essential transport infrastructure and supplies such as electricity, water and gas. With the use of our flood risk data, operators can work out what degree of flooding will cause asset failure, and combine this information with information about how critical the asset is, and if there are other means within a network of keeping services going in the event of flooding.

2.0  What were the causes of the collapse of the bridges in Cumbria? To what extent were the collapses caused by structural flaws, the age or state of maintenance of the bridges?

  This does not fall within our remit or expertise.

3.0  How likely is it that the recent experiences in Cumbria would be repeated in other parts of the country in the event of similar weather conditions? How well protected are the country's bridges to cope with the type of flooding events seen in Cumbria? What would be the implications if we continued as "business as usual"?

  3.1  The Environment Agency is not in a position to comment on the ability of the country's bridges to withstand particular scale events. However, when considering the impact of flooding on bridges, it is important to also consider that some bridges and other large pieces of infrastructure can, in their present location and form, impede the dispersal of flood water in a way that causes further damage to property and communities. This can even extend to other elements of transport infrastructure, such as erosion of approach embankments to a bridge.

  3.2  The level of rainfall recorded in Cumbria in late November 2009 was unprecedented. However, climate change will increase the risk of extreme weather events. This means that infrastructure and defences are likely to be more frequently tested by extreme weather events in the future.

4.0  To what extent is the nation's other transport infrastructure, such as roads and railway lines, adequately protected against severe flooding events?

  4.1  Potential flood damage to roads and railways is difficult to predict accurately at a national level. The vulnerability of roads and railways varies considerably depending upon their location and construction, and the costs associated with disruption depend upon the availability of alternative routes and services. We know however from major floods, such as in autumn 2000, that the damages to roads and railways can be significant. During the 2007 floods 10,000 people were trapped on the M5 motorway and other roads and railway facilities had to be closed.

  4.2  Our 2008 National Flood Risk Assessment identifies the number and types of important infrastructure and public services in flood risk areas. Our assessment is that in England about 10% of main roads and 21% of railways are at flood risk. In Wales 11% of main roads and 33% of railways are in flood risk areas.

5.0  What measures, if any, should the Government take to better protect bridges and transport infrastructure from flooding events? Is there a need for the Government to undertake a significant building programme to renew or replace bridges? What would be the estimate costs?

  5.1  As well as the impact of flooding on bridges, the reverse impact of bridges and transport infrastructure on flood risk also needs to be considered. The Environment Agency are involved in approving any specific proposals to repair or build new bridges over statutory "main rivers", while the drainage department of local authorities will consider proposals on smaller watercourses (principally through the Water Resources Act 1991 Section 109, Land Drainage Act 1991 Section 23, and Highways Act 1980 Section 339). We work alongside highway authorities or rail companies to ensure these works take account of flood risk in the location. Bridge design requirements are very site specific, however we would typically expect major new bridges to be able to pass a flood with an annual probability of occurrence of 1% (1 in 100) with no difference in water levels between the upstream and downstream sides (afflux), taking account of climate change. For structures such as new roads crossing flood plains, there may need to be additional flood arches in bridge approaches, to ensure no adverse effect on flood risk. Where bridges are to be re-built, we acknowledge the nature of the existing structure, but seek improvements to flood management commensurate with the nature of repairs. This inevitably depends on the specific nature of the repair, but can include raising the deck of the bridge above the highest water level lowering the bed level of the river at, and on either side of the bridge (particularly when scour protection is being installed there), providing additional flood openings, and removing redundant piers, debris and other obstructions from the river.

  5.2  Our relationships with transport providers are generally good in considering proposals for new and repaired structures. We deal with Network Rail, local authorities in their role as statutory highway authorities, the Highways Agency in England, and Transport Wales. We have worked with the Highways Agency on previous editions of the Design Manual for Roads and Bridges ( addressing flood and water pollution risk, and this document is widely used by local authorities and the devolved administrations. We recently (November 2009) signed a detailed memorandum of understanding with the Highways Agency, which includes working arrangements taking account of the complex legal provisions regarding highway infrastructure and management of flood risk. We also hope that some of these complexities can be reduced in forthcoming legislation, particularly any follow up to the Flood and Water Management Bill, which is currently being debated in Parliament.

  5.3  Following the 2007 summer floods, the Pitt Review recommended establishing a systematic programme to protect critical infrastructure from natural hazards, such as flooding. Recommendation 53 stated "A specific duty should be placed on economic regulators to build resilience in critical infrastructure".

  5.4  The Natural Hazards Team in the Cabinet Office is currently assessing the resilience of nine key sectors, including transportation to flooding. The team recommend the adoption of an initial minimum standard for the resilience of critical national infrastructure and essential services of one in 200 annual probability against flooding from all sources, and that reviews are undertaken every six years to ensure that this standard is maintained over time. They are consulting on the level of this standard (consultation closes 18 January). The Environment Agency is preparing its response to the consultation. Each Sector is also preparing a Sector Resilience plan to document progress within the Sector to improve resilience from flooding. During 2010, the Natural Hazards Team will be producing a National Resilience Plan.

  5.5  The Environment Agency has no powers to demand infrastructure operators take action to mitigate flood risk. However, by working with us and sharing information between Local Resilience Forum Partners and specifically infrastructure operators, we can better understand the risks they face, provide appropriate and timely warnings so they can take actions to reduce the impact of flooding on critical assets. We provide a specific flood warning service for organisations such as Network Rail who operate a bridge inspection service for their railway bridges triggered by our flood warnings. If thresholds are reached then speed restrictions or closures are put in place until site inspections have been undertaken. The Environment Agency is currently developing a tailored flood warning service known as Flood Warnings for Infrastructure and would encourage other operators with assets or networks of assets to take up the service. All operators need to assess their vulnerability to flood risk and take appropriate action. To date we have seen an inconsistent approach from operators around the country with no significant increase in resistance or resilience projects.

  5.6  Guidance will be produced for regulators by the Natural Hazards Team to enable them to support effectively a national programme of cross-sector resilience-building from all natural hazards. This will include measures to ensure that key utilities and public services take responsibility for protecting their operations from the consequences of flooding. The identification and delivery of measures to improve the resilience of critical infrastructure is partly dependent on regulatory review cycles (in the regulated sectors) and hence funding availability. This should form part of a wider climate change proofing of critical infrastructure, facilities and services. The Flood and Water Management Bill should help in this regard. Clause 13 of the Bill establishes a duty for relevant authorities to cooperate with local authorities and the Environment Agency to share information relevant to the management of flood risk from all sources to assist long term emergency and spatial planning.

January 2010

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