Memorandum from the Environment Agency
(BIC 07)
SUMMARY
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.
1.0 INTRODUCTION
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 (http://www.standardsforhighways.co.uk/dmrb/vol11/section3/11s3p10.pdf)
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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