Memorandum submitted by the Institution
of Civil Engineers (ICE) (FL 101)
INSTITUTION OF
CIVIL ENGINEERS
1. The Institution of Civil Engineers (ICE)
is a UK-based international organisation with over 75,000 members
ranging from professional civil engineers to students. It is an
educational and qualifying body and has charitable status under
UK law. Founded in 1818, the ICE has become recognised worldwide
for its excellence as a centre of learning, as a qualifying body
and as a public voice for the profession.
PREVIOUS REPORTS
2. After the autumn 2000 floods, ICE was
asked by government to hold a Presidential Commission into flood
risk management. Many of the recommendations of the subsequent
report[27]
and its successor[28]
are still valid. The findings of the government's own 2004 Foresight[29]
report and the supporting technical volume[30],
to which many ICE members contributed, are also relevant.
FLOODING 2007—THE
CAUSES
3. The recent floods were noteworthy in
that they took place in June/July/August a period normally associated
with localised intense summer storms. On this occasion, a study
of the rainfall records suggest that the flooding followed a period
of persistent and extremely wet weather, more typical of winter
months. Around, Sheffield and Hull this resulted in normally permeable
soils becoming virtually impermeable, with the obvious consequences
for volumes of surface water. ICE recommends that the Committee
considers the issues around surface water management and not focus
purely on rivers bursting their banks. By way of example ICE believes
that 75% of the Gloucestershire's flooding was inland—relating
to drains and streams—and not main rivers.
DESIGN STANDARDS
4. There is a concern that there is a poor
understanding of the meaning of the terminology used to describe
the level of protection provided by flood defences. Defences designed
with a 1% probability of being breached in any one year are described
as operating to 1:100 year return period. The higher this period
is set, the higher the level of defence. This introduction of
time periods is aimed at making probability more readily understandable
but can also be misleading to the layperson. Taking a 1% probability
over 70 years, it can be shown that a 1:100 year flood has a 50%
probability of occurring during that period and a 15% probability
of occurring twice.
5. ICE supports a review of the suitability
of design standards for all flood defences. Property and infrastructure
in areas with fluvial (river) defences designed for a 1:100 year
incident were affected by the recent floods. Also, in many areas
with relatively high levels of fluvial defences, flooding occurred
due to the limitations of urban drainage systems, currently designed
to a maximum 1:30 year standard. This was certainly the case in
Hull where areas were inundated due to failure of land drainage
and public sewer pumping stations. Finally Planning Policy Statement
25 requires that promoters of new development in areas at risk
of coastal/tidal flooding ensure they are defended to a 1:200
year standard. However existing property in such areas is not,
as a matter of course, defended to this level through the public
purse indeed many defences offer standards as low as 1:10 years
or worse.
6. It is also the case that the actual risk
of flooding in any one area may be far greater than often anticipated
because the hazards arise from a variety of sources including
rivers, land drainage systems, sewer systems and coastal flooding.
This creates a cumulative risk, which can also be triggered by
a variety of different metrological conditions. To combat this
threat ICE recommends that the Committee examines how the institutional
and legal barriers to an integrated approach to urban drainage
and flooding can be overcome. Furthermore whilst brownfield development
is to be welcomed for its regeneration benefits, it does to add
a burden to existing Victorian drainage systems unless they are
strengthened.
7. There is evidence that the public is
increasingly risk averse and it is valid for society's changing
view of acceptable risk to affect Flood Risk Management policy
and by extension design criteria. Yet the impact of public opinion
on policy is not obvious. Any danger to life will clearly result
in a very low level of acceptable risk. However if risks are to
inundation of farmland, managed retreat may be an option.
8. Finally, in the case of genuinely extreme
events, overtopping of flood defences and drainage systems will
occur. This fact needs to be accepted and more done to ensure
that valuable infrastructure in areas at risk is resilient or
relocated.
FORECASTING
9. The Environment Agency has recently invested
in a National Flood forecasting system which provides a common
framework within which to operate a real time flood forecasting
model. This is a welcome development, but ICE is concerned that
flood forecasting capability varies considerably between EA regions.
Investment in flood forecasting models needs to be accelerated
to ensure the UK benefits from advances in forecasting. In particular
as hydrodynamic river flow modelling develops, it should be possible
to make a much more robust link between metrological forecasts
and consequential river flows. This will allow agencies to more
accurately predict size, location and timings of flooding of the
nature that affected Sheffield.
10. ICE believes that the EA issued flood
warnings in line with correct procedures but the Committee should
note:
— Warnings currently only identify
if a "zone threshold" is likely to be reached and do
not provide inflation on flood level and timing to owners of individual
properties
— The Agency is responsible for giving
flood warnings resulting from main rivers and the sea/tide. As
noted above, much of the recent flooding was a result of flash
flooding related to extreme rainfall. The Met Office with its
access to rainfall radar technology may be best placed to offer
localised warnings of flooding from these other sources. The inadequacies
of the warnings in June/July suggest that the EA and the Met Office
should work more closely in this area.
VULNERABILITY OF
CRITICAL INFRASTRUCTURE
11. The floods demonstrated the vulnerability
of critical infrastructure including water treatment works, national
grid key points and in Gloucestershire major roads including the
M5, M50 and A40. ICE recommends considering two linked issues:
— Improving factual knowledge of what
is at risk. We understand that Severn Trent did not believe that
its water treatment works at Tewkesbury was in an area of flood
risk. Whilst the EA's website does reveal the facility is situated
in a 1% flood risk zone, more work is clearly needed to ensure
that owners of facilities are aware of risks. Local Authorities
have a duty under the Civil Contingencies Act to develop community
risk registers. The Committee should examine the progress with
the production of these registers and how effective they are in
identifying infrastructure at risk and communicating this to owners.
— Much critical infrastructure in now
privately managed and decisions around siting and appropriate
levels of defences are based primarily on commercial and regulatory
considerations. Regulation could be imposed to require either
improved contingency planning or any actual guarantee of provision
(analogous to the duty on water companies to demonstrate drought
capability). We believe that there is a strong argument that the
public interest would be served by such a move but recognise that
there would be a financial cost, which providers are likely to
pass on to consumers.
ADVICE TO
THE PUBLIC
12. Our perception is that senior officials
and politicians were successfully mobilised to provide high level
information to the media. However authorities were not as successful
in providing details and data at a property by property basis
or even at a community scale. To an extent this is likely to be
a recurring problem, particularly in areas such as Tewkesbury
where the flooding incident involved two catchments simultaneously
(the Severn and the Avon) and rainfall related flash flooding,
increase the difficulty of predicting the combined event. A lesson
may be that flooding from numerous sources from different timed
events is extremely difficult to prevent by centralised measures
in high risk zones. In these circumstances it may be wise to place
all properties in the area on the EA's Automated Voice Flood Notification
System to enable owners take personal mitigation measures. However
ICE recognise that this is only likely to be effective in areas
of high risk, as residents in areas with 1 in 100 year risk, vulnerable
to an extreme event, are unlikely to act on a generalised warning
regarding an entire flood plain.
TEMPORARY DEFENCES
13. Temporary defences, both bespoke demountable
defences for specific locations and general temporary defences
(eg sandbags) are likely to be part of a long term sustainable
solution to flood risk management. Whilst temporary measures provide
flexibility and reduce visual intrusion, they are reliant on human
intervention and thus only as effective as the system they operate
within. Planning exercises are required to improve the smoothness
of the mobilisation and deployment of these resources. The public
that is protected by such defences also needs to be given a very
clear understanding of their advantages and disadvantages. Decision
makers should also be aware that, quite naturally, as memories
of flooding fades, so does the public perception of disadvantages
of temporary defences.
FLOOD RISK
MITIGATION—MANAGING
PROBABILITY AND
CONSEQUENCES
14. The "priority scoring" model
used by the Environment Agency since 2002 to allocate funds for
flood and coastal has in practice led to schemes that are economically
justifiable in cost/benefit terms not receiving funding. It should
also be noted that because the system is largely driven by assessment
of economic impact, it favours defences in more affluent areas
and/or areas with large populations.
15. Overall the Environment Agency is currently
spending circa £600 million per annum on flood defences.
The Association of British Insurers believes this should increase
to around £1 billion. The government's Foresight study
into future flooding estimates that changing weather and development
patterns suggest that the UK could need spend between £22
billion and £75 billion in the period up to 2080 on new engineered
flood defences. The public acceptability of this level of spending,
and also the carbon footprint of the necessary built assets, may
be a constraint. If so, government and the EA must engage in a
proper public dialogue, particularly with communities who will
not be defended to the extent that they may well expect.
16. A further aspect of the "priority
scoring" methodology, is that by allowing annual shifts in
priorities and budgets it exacerbates a "stop-start"
approach to developing flood risk infrastructure. This has hampered
recent efforts to develop long term plans for the development
and retention of skilled engineering staff, the shortage of which
was a key finding of ICE's Learning to Live with Rivers
report.
17. The Committee should note that the comments
above refer to coastal and main river schemes. The June/July events
suggest that significant investment may also be required to upgrade
drainage to address risks associated with flash flooding.
18. In the context of the likely need for
additional spending, it is alarming that the National Audit Office
found that in 2005-06, 29% of the Agency's capital budget for
river and coastal defence was spent on programme management and
planning[31].
This is above the level one would expect in the utilities sector
and suggests that the Agency's business processes would benefit
from streamlining.
SUSTAINABLE URBAN
DRAINAGE SYSTEMS
(SUDS) AND MANAGING
RUN OFF
19. SUDs which as far as possible mimic
the natural drainage of a site and deal with runoff close to where
rain falls are essential for all new development. We are concerned
that Planning Policy Statement 25 (PPS 25) is not prescriptive
enough in this respect.
20. However we recognise that SUDs cannot
provide a complete answer. The recent floods suggest that in the
case of genuinely extreme events the bulk of the flood water is
conveyed on the surface and SUDs will have only limited impact.
In these circumstances, the most effective way of avoiding indiscriminate
flooding of property is for urban development to be designed to
accommodate the passage of flood water safely on the surface.
Also as water flows downhill, low lying land should only be designated
for low level development and certainly not housing. Buildings
can also be designed to be more resilient to flooding.
PROSCRIBING DEVELOPMENT
IN FLOOD
PLAINS
21. It is not realistic to proscribe all
development in flood plains. Central to PPS 25 is the process
of matching type of development to degree of flood risk. The PPS's
"sequential test" instructs planning authorities to
show there are no reasonably available sites with a lower risk
of flooding appropriate to that type of development or land use.
Where a lower risk site can not be found, proposed development
is required to pass an "exception test" demanding that
the development makes a positive contribution to sustainable communities
and to reducing or managing flood risk.
22. These conditions need to be properly
enforced. In this context we are concerned that the Law Society
reports that in 2005, 21 major planning applications were granted
against Environment Agency advice on flood risk.[32]
BALANCE BETWEEN
INSURANCE, PUBLIC
INVESTMENT AND
PRIVATE PROVISION
23. At present the UK benefits from "shared"
flood risk insurance which is available to most property owners.
This situation, combined with a relatively high level of public
investment in flood risk management, currently provides a high
level of security compared with much of the world. The long term
viability of this situation relies on agreement between the insurance
industry and the government on where the balance should lie between
these two factors. At present the ABI has made it clear that it
will provide collective insurance for events less frequent than
1:75 years and in practice public investment determines who is
above or below that threshold. New development and climate change
are increasing flood risk but is seems unlikely that the insurance
industry will be willing to absorb ever increasing levels of risk.
This means that either public investment in flood risk management
will need to be increased or more of the cost passed directly
to owners of property directly at risk. In principle given that
the benefits of flood defence accrue very widely, it would be
reasonable to expect the public purse to meet the costs of defences
that are sustainable and cost effective.
FLOOD DEFENCE—SUCCESS
AND FAILURES
24. A full account of the success and failures
of defences will doubtless be provided by the EA, however some
examples are given below. One point that should be noted is that
the condition of flood defence assets does not appear to have
been a major issue, as most flooding took place where there was
no defence at all or where defences were overtopped.
25. A notable success was the use of demountable
defences at several sites including Bewdley. The corollary to
this is the problems at Upton-on-Severn where demountables were
stored 25 km away as they served a number of villages and were
not able to be delivered in time because of traffic problems caused
by the flooding. The defences were however deployed elsewhere
however, so were put to effective use.
26. Sheffield was impacted severely. The
rescue mission for its local reservoir which started to fail demonstrates
good and bad practice. Recent inspections appear not to have identified
the potential for failure. However the immediate response from
both professional advisors and the emergency services (closure
of the M1 and identifying areas of evacuation) avoided the potential
for disaster. In the event the reservoir maintained its overall
integrity and the required strengthening works are being implemented
in the short and longer term.
27. We also note that the River Tame defence
in Birmingham were overtopped, suggesting there is a case for
reviewing and increasing the protection provided to England's
second city.
ADMINISTRATIVE ARRANGEMENTS
AND RESPONSIBILITIES
28. The poor overall condition and lack
of maintenance of many watercourses was a factor in the recent
events.
29. The responsibility for critical ordinary
water courses lies with the Environment Agency. This is a recent
change following previous flood report recommendations. The EA
is not however adequately resourced so whilst they have adopted
the responsibility they have asked Internal Drainage Boards and
Local Authorities to act on their behalf to continue to manage
this type of watercourse. Problematically these bodies are also
short of funds.
30. The owners of non main rivers, streams
and watercourses do have responsibilities but often do not manage
their assets well due to lack of knowledge and funds.
31. ICE does not believe it is realistic
to attempt to place more responsibilities on riparian owners,
not least because the benefits from actions and/or defences created
accrue to a much wider section of society.
32. We would ask the Committee to examine
the case for shifting the criteria for ownership away from physical
location/size to one based on risk. Under such a system, all high
risk river systems would be publicly owned and managed. In addition
the Environment Agency does have enforcement powers over existing
riparian owners. The Committee may want to consider if the EA
has the funding, skills and other resources to effectively exercise
these powers.
CLEAN-UP
COSTS
33. The Bellwin formula appears to have
been too low to cover the clean up costs required for Gloucestershire,
Hull, Sheffield and Humberside. The government was forced to supplement
the cash derived from the formula with additional injections of
cash.
WIDER ISSUES
34. There is a danger that current activity
will focus almost exclusively on flooding related to rivers and
extreme rainfall. This masks the wider question of the adequacy
of the UK's defences against all forms of flooding, including
coastal and tidal flood events.
35. If taken together, the overall risk
of flooding from potential and combined sources of flood water
is probably understated. As noted in the body of our response,
when combinations of flood events occur simultaneously or build
on each other the difficulty of predicting and defending against
their impact is heightened. Models of the impact of climate change
suggest that such multi cause events are likely to become more
frequent. Climate change is also likely to place significant,
specific strain on Flood and Coastal Erosion Risk Management services.
36. In the long term "traditional"
flood defences, and the investment that goes with them, will need
to be complemented by an increased focus on urban design, building
standards and managed retreat. However the public must be engaged
with and understand the implications of this debate.
ICE
September 2007
27 Institution of Civil Engineers (2001), Learning
to Live with Rivers, London: ICE Back
28
Institution of Civil Engineers (2004), Engineering Skills for
Flood Risk Management, London: ICE Back
29
Office of Science and Technology (2004), Foresight, Future Flooding,
London: HMSO Back
30
Thorne, C, Evans, E and Penning-Rowsell, E (2007), Future Flooding
and Coastal Erosion Risk, London: Thomas Telford Ltd Back
31
National Audit Office (2007), Building and Maintaining River
and Coastal Flood Defences in England, London: HMSO Back
32
Law Society (2006), Response to consultation on PPS 25,
Law Society, London, UK Back
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