Select Committee on Environment, Food and Rural Affairs Minutes of Evidence

Memorandum submitted by Thames Water (FL 104)


  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" authority impracticable.

    —  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 expenditure.

    —  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 general taxation.

  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 be achieved.


  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 prices.

  1.2  Our area includes Greater London and other major conurbations in the south-east of England. Much of London is served by "combined" sewers—there 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 property/land owner.

2.4  Main Rivers (as defined on the "main river" map)

  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.

2.5  Roads

  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 or soakaway.

2.6  Water Courses (non main river) and Land Drainage

  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 fully.


  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 flooding

    —  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.


  4.1  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 Thames Valley.

  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).


  5.1  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 and responsibilities.

  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 assets—such as water and sewage treatment works, which by their nature tend to be close to rivers—and 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.

Thames Water

September 2007

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