Memorandum submitted by Thames Water (FL
The rainfall of earlier this year was exceptional
in terms of recent history but is regarded by observers to be
indicative of the challenges likely to arise as a result of climate
change. Aside from the obvious distress caused to individuals,
the flooding highlighted the vulnerability of utility assets,
some of which were critical in that their being disabled resulted
in a protracted loss of acceptable service. It is clear that both
immediate and longer-term measures are required if the impact
of a similar event is to be reduced, but the longer-term measures
are difficult to agree and implement due to the fragmented responsibilities
for drainage and river management. We see the issues as falling
under three main headings:
Administrative (institutional): Responsibility
for managing flood risk, particularly in urban areas, is spread
across several authorities/bodies without an effective "overarching"
body. Tackling this is very likely to involve legislative change,
or at the very least, better clarification of roles and responsibilities.
Conversely, the dual foul/stormwater function of many existing
physical assets may make the creation of a "stormwater"
Costs and benefits: It is impracticable
to completely remove all flood risk. It is therefore an issue
for society to determine what level of protection is appropriate,
both now and in an uncertain future. In deriving what is "appropriate",
different degrees of protection might be suitable for different
types, or causes, of flooding event. Given that there is already
a shortfall against current standards in some areas, an early
agreement to future requirements is essential to avoid wasted
Funding: Linked to both the above
topics is the issue of how improvements should be funded. Again,
it is an issue for society to decide whether the cost of improvements
fall on those who benefit directly or whether they are spread
wider, either (for example) through customer water charges, or
We are aware of, and have responded to, the
recent consultation "Making Space for Water". This
consultation considered the Environment Agency as having a strategic
overview for all flooding matters, and we are supportive of the
principle of having such an umbrella organisation. Nonetheless,
we would welcome a broader, long-term review of all flood risk
management and delivery bodies. Ideally, this would establish
clear responsibilities and accountabilities, and facilitate an
integrated approach with solutions from a local through to catchment
scale. As such it is likely to involve organisational, funding
and legislative changes to the current framework. Without such
changes it is difficult to envisage how better integration might
1.1 Thames Water is the Water and Sewerage
Undertaker for the approximate region of the River Thames catchment.
One of our duties is to provide "effectual drainage",
which is interpreted by our economic regulator (Water Services
Regulation Authority, "Ofwat") and related to "levels
of service". As Ofwat also determines our overall charge
for services, there is a clear link between service level and
1.2 Our area includes Greater London and
other major conurbations in the south-east of England. Much of
London is served by "combined" sewersthere is
a single pipe for both foul and storm waters. This is a historical
legacy, and to provide separate systems has been assessed but
considered to be too expensive and disruptive. The threat of widespread
flooding in London is linked to sea levels and surge conditions,
but there are instances of local flooding related to the incapacity
of the existing urban drainage.
2.1 Responsibility for the different elements
of the drainage system is complex. Historically the system was
largely under public ownership, but at privatisation in 1989 the
drainage system was divided between water companies, the EA and
local authorities. The below paragraphs explain current responsibilities,
however it should be noted that Government is in the process of
consulting on water companies adopting most private drains and
sewers, thereby taking responsibility for their performance. We
anticipate that this will not occur before 2010.
2.2 Public Sewers
Water companies have a general duty to allow
lawful connection to the public sewer and maintain its effectiveness.
Where only one pipe is provided, customers may connect both foul
and surface (or storm) water.
2.3 Private sewers
Private sewers are the responsibility of the
2.4 Main Rivers (as defined on the "main
The EA is responsible for building, maintaining
and operating main river flood defenses. Through land drainage
consents, the Agency can limit the quantity of water discharged
through an outfall.
The County Council, Unitary Authority or London
Borough is usually responsible for local highway drainage. Highway
drainage may connect to a public sewer or directly to a watercourse
2.6 Water Courses (non main river) and Land
Local Authorities have limited discretionary
or permissive powers for dealing with non-main rivers and have
additional responsibilities if land is directly owned. All landowners
are responsible for ditches and watercourses that are on their
land or along boundaries of their land, except for those designated
as highway ditches or main rivers. Responsibility for maintaining
a watercourse may be split between many individuals, which can
make organising maintenance a problem. The Local Authority has
certain limited powers to advise owners and carry out work as
a last resort.
In addition to the above there is the major
role of the planning authorities to ensure the implementation
of the various codes of practice and policy guidance. However,
the Environment Agency (EA) has expressed its concern that some
local authorities are not sufficiently observing government policies
designed to ensure development needs are met without creating
unnecessary risks. Although most local authority development plans
do now include flood risk statements or policies, the EA reported
that, of the cases it was aware of, nearly 15% of the planning
decisions taken in 2003-04 were not in line with the government's
planning policy guidance on flood risk and development (PPG25).
Barbara Young, Chief Executive of the EA has commented, "There
is a persistent core of planning applications being approved contrary
to our advice, including a small but significant number of major
developments, many of which are for homes."
In summary, the above demonstrates that there
is a fragmented approach with differing statutory requirements,
and that even where guidance exists it may not be being implemented
3. OUR CURRENT
3.1 All flooding incidents are recorded
on our flooding history database, this is the main tool used to
determine investment in flood alleviation schemes. Whilst being
flooded is a hugely distressing experience for customers, preventing
flooding to all properties under all circumstances is not feasible.
TW are only funded by OFWAT to resolve flooding to properties
at risk from a 1 in 10 year storm, where the solution is cost-beneficial.
3.2 The problem of flooding is addressed
in order of priority and in doing this, three key points are considered:
The seriousness of the flooding
Likelihood of a repeat flooding
Cost of solution relative to the
number of homes affected
It is necessary to ensure that when looking
at a solution to any flooding issue it does not create a risk
of flooding elsewhere. Depending on local circumstances, and the
cause of the flooding consideration of a range of options is made
to reduce the risk of flooding.
3.3 Where the flooding is caused by a blockage,
sewer collapse or similar cause the solutions may be as follows
More regular sewer cleaning in areas
of known flood risk to minimise the possibility of blockages occurring
Seeking ways to stop wastewater backing
up from sewers into property or spilling out of manholes
Correcting any minor defects
These solutions are implemented, where possible
for all properties flooded due to blockages, even if this occurred
due to severe weather.
3.4 If the flooding is caused by overloaded
sewers (i.e. the sewers are unable to cope with the flow) different
solutions are appropriate. In these circumstances investigation
is made into an engineering solution for properties at risk of
flooding from a 1 in 10 year storm or less. These solutions may
take a number of years to design and implement, as well as being
costly. They include:
Building new sewers to increase the
capacity of the local system
Installing pumping stations to pump
the wastewater away more quickly
Providing storm overflows to allow
surplus water to escape from the sewerage network without causing
Sealing sewers to stop groundwater
seeping into them
Providing storage, such as underground
tanks or environmental ponds, so that storm water can overflow
harmlessly from the sewers.
The solutions that we implement to alleviate
flooding are designed to provide protection for rainfall events
occurring up to a 1 in 21 year return period. Because the above
engineering solutions can be subject to planning restrictions
and take time to put into effect, Thames Water may carry out mitigation
works at or near a property affected by a 1 in 10 year storm to
reduce the frequency of flooding in the short term.
3.5 The key consideration is whether the
current level of planned protection is appropriate, and we aim
to revise our designs post 2010 to offer 1 in 30 year return period
protection, subject to funding approval.
4. CURRENT INVESTMENT
4.1 Over £130 million has been invested
since 2005 to alleviate the risk of sewer flooding. This means
that we have reduced the risk of flooding due to overloaded sewers
at 2066 properties (by upgrading sewers and providing additional
storage for floodwater) and the risk of flooding due to blockages
and sewer collapses at 1381 properties.
4.2 A further £190 million will be
invested before 2010 to reduce the risk of flooding (due to overloaded
sewers) at a further 3595 properties, and the risk of flooding
due to blockages at a further 2165 properties in London and the
4.3 In total almost 6000 properties at risk
of internal flooding, and over 3000 properties at risk of external
flooding, will have been relieved by 2010.
4.4 We are also providing temporary measures
to alleviate the impact of sewer flooding to over 350 properties
where a permanent solution is too costly or not possible in the
next few years. We will continue to prioritise this investment
in conjunction with the Consumer Council for Water (CCW), refining
the process which we have developed over the last few years which
assesses the frequency and customer impact of flooding.
4.5 This means that by March 2010 there
will be approximately 6500 properties at risk of flooding due
to overloaded sewers at a frequency of more than 1:10 years (compared
to a register size of over 11,000 at March 2005).
5. OTHER INITIATIVES
5.1 It is recognised that simply building
greater capacity into our pipes and tanks cannot be the only strategy
for adapting to climate change in the future, and we are participating
in two Defra-sponsored Integrated Urban Drainage pilot schemes
which consider alternative approaches. However, organisational,
funding and legislative changes would be required to deliver these
alternative scenarios. In particular, much is often made of the
value of various types of "sustainable urban drainage structures"
(SUDs). Implementation of some of these approaches may not be
fully consistent with the "polluter pays" principle,
and nor do they necessarily fit well with existing statutory duties
5.2 It is critical that as well as identifying
the most appropriate framework for delivering integrated urban
drainage, any analysis should consider what appropriate funding
and incentive mechanisms are required to enable delivery and engender
change. Funding and incentive mechanisms should be transparent,
equitable, and embrace the "polluter pays" principle.
Thames Water is concerned that past precedent suggests that any
new unfunded burden would fall on Sewerage Undertakers, without
a corresponding uplift in bills.
5.3 In addition to activity to protect our
customers directly, we will be reviewing the risk to our own major
surface assetssuch as water and sewage treatment works,
which by their nature tend to be close to riversand the
consequences for service delivery should their operation be impacted.
5.4 Lastly, there is a need to integrate
climate change into the planning and regulatory framework for
urban drainage. The costs associated with climate change adaptation
are difficult to estimate but could be considerable, and there
is a need for a better understanding of the links between risk,
probability and cost. This better understanding must be extended
to the wider public, if we are to gain their acceptance of the
likely financial consequences.