“Manchester Ship Canal: The Future of the Upper Reaches” stated: “The Act of Parliament approving construction of the Canal imposed an obligation on the Manchester Ship Canal Company not to worsen the flood risk but in fact the construction of the canal improved the flow capacity of the waterway so that for the last ninety years there has been no significant flood risk between Manchester and Warrington. At each lock large sluices were constructed and these have been able to pass even the largest floods downstream to Runcorn where sluices at the mouth of the River Weaver pass them safely into the estuary.”
“the sluicing capacity on the canal was sufficient to pass most flood flows and endure most tidal events without widespread overtopping of banks on either the canal or the lower Mersey. Potential flood risks have, however, been identified in a number of areas, including a reach of the River Irwell upstream of Trafford Road Bridge. The canal itself is predicted to flood during fluvial events downstream of Barton Swing Bridge and in the Latchford pond and around Eastham during tidal events.”
“If climate change materialises in the manner currently predicted and leads to the estimated 20% increase then water levels in the canal would increase during the flood event with 1% chance of occurring in any one year (100 year return period). ...the existing standard of flood protection along the Manchester Ship Canal is generally above the 0.5% annual probability (200 year return period) flood equivalent except in the vicinity of Salford Quays, Salteye Brook confluence and the largely uninhabited Thelwall floodplain near Rixton junction. More widespread inundation of properties would be expected during the flood event with a 0.1% chance of occurring in any one year (1,000 year return period flood event)”
“As part of our ongoing discussions on managing flood risk in relation to the Manchester Ship Canal we have been reviewing our approach to producing flood maps. Over the last few months we have considered the views and evidence you have put to us and involved colleagues throughout the organisation including our Director of Flood Risk Management, David Rooke. I can now confirm the approach we intend to take to producing a Flood Map for the Manchester Ship Canal. Our Flood Map shows “Flood Zones” and “Areas Benefiting from Defences”
“For the purposes of carrying out its flood defence functions the [Agency] shall from time to time carry out surveys of the areas in relation to which it carries out those functions.”
“This guidance states that: • the susceptibility of land to flooding is a material planning consideration; • the Environment Agency has the lead role in providing advice on flood issues, at a strategic level and in relation to planning applications; • policies in development plans should outline the consideration which will be given to flood issues, recognising the uncertainties that are inherent in the prediction of flooding and that flood risk is expected to increase as a result of climate change; • planning authorities should apply the precautionary principle to the issue of flood risk, using a risk-based search sequence to avoid such risk where possible and managing it elsewhere; • planning authorities should recognise the importance of functional flood plains, where water flows or is held at times of flood, and avoid inappropriate development on undeveloped and undefended flood plains; • developers should fund the provision and maintenance of flood defences that are required because of the development; and • planning policies and decisions should recognise that the consideration of flood risk and its management needs to be applied on a whole-catchment basis and not be restricted to flood plains.” • the susceptibility of land to flooding is a material planning consideration; • the Environment Agency has the lead role in providing advice on flood issues, at a strategic level and in relation to planning applications; • policies in development plans should outline the consideration which will be given to flood issues, recognising the uncertainties that are inherent in the prediction of flooding and that flood risk is expected to increase as a result of climate change; • planning authorities should apply the precautionary principle to the issue of flood risk, using a risk-based search sequence to avoid such risk where possible and managing it elsewhere; • planning authorities should recognise the importance of functional flood plains, where water flows or is held at times of flood, and avoid inappropriate development on undeveloped and undefended flood plains; • developers should fund the provision and maintenance of flood defences that are required because of the development; and • planning policies and decisions should recognise that the consideration of flood risk and its management needs to be applied on a whole-catchment basis and not be restricted to flood plains.”
“9. Historically, development has taken place in both river and coastal flood plains. .. However, the growth of built development within flood plains over the centuries has increasingly required engineering works to defend properties against the risk of flooding.... 10. Flood risk involves both the statistical probability of a flood occurring and the scale of the potential consequences. ... While flood defence works can reduce the risk of flooding, they cannot eliminate it. For example, a flood bank designed to contain a particular level of flood will be overtopped by one that is more severe. Flood risk is also expected to increase over time as a result of climate change. It is important that those who plan and occupy development in flood risk areas are aware of the remaining risk, despite the presence of flood defences, and the steps that they should take in the event of a flood.... 11. Continued construction of hard-engineered flood defences to protect development in areas exposed to frequent or extensive flooding may not be sustainable in the long term.... 12. ...Potential damage from flooding is both uncertain and unpredictable but it can be significant and, in the case of soil loss, potentially irreversible. Because of this the Government considers that the objectives of sustainable development require that action through the planning system to manage development and flood risk should be based on the precautionary principle. The precautionary principle 13. “Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”
“A decision to take measures without waiting until all the necessary scientific knowledge is available is clearly a precaution-based approach. Decision-makers are constantly faced with the dilemma of balancing the freedoms and rights of individuals, industry and organisations with the need to reduce or eliminate the risk of adverse effects to the environment or to health. Finding the correct balance so that proportionate, non-discriminatory, transparent and coherent decisions can be arrived at, which at the same time provide the chosen level of protection, requires a structured decision making process with detailed scientific and other objective information. This structure is provided by the three elements of risk analysis: the assessment of risk, the choice of risk management strategy and the communication of the risk. Any assessment of risk that is made should be based on the existing body of scientific and statistical data. Most decisions are taken where there is sufficient information available for appropriate preventative measures to be taken but in other circumstances, these data may be wanting in some respects. Whether or not to invoke the Precautionary Principle is a decision exercised where scientific information is insufficient, inconclusive, or uncertain and where there are indications that the possible effects on the environment, or human, animal or plant health may be potentially dangerous and inconsistent with the chosen level of protection.”
“5. The aims of planning policy on development and flood risk are to ensure that flood risk is taken into account at all stages in the planning process to avoid inappropriate development in areas at risk of flooding, and to direct development away from areas at highest risk. Where new development is, exceptionally, necessary in such areas, policy aims to make it safe without increasing flood risk elsewhere and where possible, reducing flood risk overall. 6. Regional planning bodies (RPBs) and local planning authorities (LPAs) should prepare and implement planning strategies that help to deliver sustainable development by: Appraising risk • identifying land at risk and the degree of risk of flooding from river, sea and other sources in their areas; • preparing Regional Flood Risk Appraisals (RFRAs) or Strategic Flood Risk Assessments (SFRAs) as appropriate, as freestanding assessments that contribute to the Sustainability Appraisal of their plans; Managing risk • framing policies for the location of development which avoid flood risk to people and property where possible, and manage any residual risk, taking account of the impacts of climate change; • only permitting development in areas of flood risk when there are no reasonably available sites in areas of lower flood risks and benefits of the development outweigh the risk from flooding; Reducing risk • safeguarding land from development that is required for current and future flood management eg conveyance and storage of flood water, and flood defences; • reducing flood risk to and from new development through location, layout and design, incorporating sustainable drainage systems (SUDS); • using opportunities offered by new development to reduce the causes and impacts of flooding...”
“LPAs allocating land in LDDs for development should apply the sequential test (see Annex D and Table D.1.) to demonstrate that there are no reasonably available sites in areas with a lower probability of flooding that would be appropriate to the type of development or land use proposed. A sequential approach should be used in areas known to be at risk from other forms of flooding. 17. In areas at risk of river or sea flooding, preference should be given to locating new development in Flood Zone 1. If there is no reasonably available site in Flood Zone 1, the flood vulnerability of the proposed development (see Table D.2, Annex D) can be taken into account in locating development in Flood Zone 2 and then Flood Zone 3. Within each Flood Zone new development should be directed to sites at the lowest probability of flooding from all sources (see Annex C) as indicated by the SFRA.”
“Flood Zones are defined in Table D.1. Annex D. The Flood Zones refer to the probability of flooding from rivers, the sea and tidal sources and ignore the presence of existing defences, because these can be breached, overtopped and may not be in existence for the lifetime of the development.”
“D1 The risk-based Sequential Test should be applied at all stages of planning. Its aim is to steer new development to areas at the lowest probability of flooding (Zone 1). D2 The Flood Zones are the starting point for the sequential approach. Zones 2 and 3 are shown on the Environment Agency Flood Map with Flood Zone 1 being all the land falling outside Zones 2 and 3. These Flood Zones refer to the probability of sea and river flooding only, ignoring the presence of existing defences. D3 Regional Flood Risk Appraisals ... will refer to Environment Agency Flood Maps and will utilise further information such as Strategic Flood Risk Assessments to allow flood risks to be taken into account in a broad regional context ... D4 Strategic Flood Risk Assessments (SFRAs) (see Annex E) will refine information on the probability of flooding, taking other sources of flooding (see Annex C) and the impacts of climate change into account. D5 The overall aim of decision-makers should be to steer new development to Flood Zone 1. Where there are no reasonably available sites in Flood Zone 1, decision makers identifying broad locations for development and infrastructure, allocating land in spatial plans or determining applications for development at any particular location should take into account the flood risk vulnerability of land uses and consider reasonably available sites in Flood Zone 2, applying the Exception Test if required. Only where there are no reasonably available sites in Flood Zones 1 or 2 should the decision-makers consider the suitability of sites in Flood Zone 3, taking into account the flood risk vulnerability of land uses and applying the Exception Test if required. D6 Within each Flood Zone, new development should be directed first to sites with the lowest probability of flooding and the flood vulnerability of the intended use matched to the flood risk of the site, e.g. higher vulnerability uses located on parts of the site at lowest probability of flooding.”
“The Exception Test is only appropriate for use where there are large areas in Flood Zones 2 and 3, where the Sequential Test alone cannot deliver acceptable sites, but where some continuing development is necessary for wider sustainable development reasons, taking into account the need to avoid social or economic blight and the need for essential civil infrastructure to remain operational during floods ...”
“consider both the potential adverse and beneficial effects of flood risk management infrastructure including raised defences, flow channels, flood storage areas and other artificial features together with the consequences of their failure;” “consider and quantify the different types of flooding (whether from natural and (sic) human sources and including joint and cumulative effects) and identify flood risk reduction measures, so that assessments are fit for the purpose of the decisions being made;” “include the assessment of the remaining (known as ‘residual’) risk (see Annex G) after risk reduction measures have been taken into account and demonstrate that this is acceptable for the particular development or land use;”
“Annual exceedance probability The estimated probability of a flood of given magnitude occurring or being exceeded in any year. Expressed as, for example, 1 in 100 chance or 1 percent.” “Flood defence Flood defence infrastructure, such as flood walls and embankments, intended to protect an area against flooding to a specified standard of protection.” “Flood map A map produced by the Environment Agency providing an indication of the likelihood of flooding within all areas of England and Wales, assuming there are no flood defences. Only covers river and sea flooding.” “Flood risk management measure Any measure which reduces flood risk such as flood defences.” “Flood Zone A geographic area within which the flood risk is in a particular range, as defined within PPS25.” “Precautionary principle Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.” “Standard of protection The design event or standard to which a building, asset or area is protected against flooding, generally expressed as an annual exceedance probability.”
“4.3 PPG25 uses a sequential method for assessing risk across the floodplain. Flood risk assessments may be required for proposed developments, particularly for those within the extreme flood outline (0.1% annual probability event). The LPAs and developers are now looking to us as experts on flood risk to provide clear advice to incorporate into their flood risk assessments for a particular site. In our support of PPG25, we will provide quality-assured data and information to LPAs on the probability of flooding within the extreme flood outline, so that they can assess the potential impacts of a development. We will also support LPAs and developers to develop strategic and local flood risk assessments.” ... “Government Planning Policy 8.1 To support the planning process and the implementation of PPG25 ..., we will provide planning authorities with information on flood risk. Both PPG25 ... define flood risk as the probability of a flood occurring, and categorise flood risk areas into three flood zones. ... 8.2 PPG25... states that “flood zones should be identified from Agency flood data ignoring the presence of flood defences. LPAs should, with the Agency, identify those areas currently protected by defences and the standard of protection provided by those defences”
“Area Benefiting from Defences The area that is protected by a defence or defence system against flooding at the 1% annual probability fluvial event and 0.5% annual probability tidal event, assuming all defences remain intact and function perfectly.” “Defence Term embracing both formal defence and de facto defences.” “De facto defence A structure that provides a flood defence function but for which flood defence is a secondary or indirect purpose.” “Formal defence A formal defence asset that directly limits the spread of flood water and, primarily because of this function, is owned and/or maintained by its present owner, regardless of whether this is the Environment Agency, another authority or a private owner.”
“3.4 State of the Catchment or Tidal Area All areas shall be considered as in their present-day “real-life” state, with existing development and surface land form. ... By considering the present “real-life” state, the assessment will take into account the possible obstruction or direction to flow of flood water offered by the built environment as well as the similar effect provided by flood defences. However, in so doing, the intent shall be not to over-complicate the assessment. Thus in general the obstruction to flow of flood water offered by buildings, boundary walls, fences and the like can be ignored. Exceptions can be made if local Environment Agency staff consider certain buildings or walls will provide secure barriers to the flow of flood water and thus act as de facto defences if they have a material effect on the spread of flood water, though openings through the embankments must be taken into account. Existing embankments, bridges and other features crossing a river floodplain shall be taken as in-place, giving their combined effect on flows and flood levels along the river.” “3.5 Flood Defences The assessment shall consider all existing flood defences as being in place and acting together to control flow and limit flood spreading. The effect of defence elements individually shall not be considered. The defences may be in any ownership ... They shall include formally designated defences and can include de facto defence structures where these are recognised by local staff as being secure in limiting the extent of flooding.... 3.6 Mapping Flood Defences Whilst de facto defences shall be incorporated into the assessment of areas benefiting from defences, they shall not be mapped in the Flood Map. The flood defences that shall be shown on the Flood Map are those structures that are formally maintained as defences and whose purpose is to limit the spread of flood water over the land. As such, the structures will be: • Raised walls, including demountable walls. • Embankments, including coastal dune and shingle ridges. • Barriers and barrages. • Flood storage areas created by a structure of structures (here it is the flood storage area and the water retaining structure that shall be mapped as flood defences, not outlet control sluices and the like). • Land drainage pumping stations. ... Structures whose purpose is to aid normal operation rather than provide flood protection shall not be mapped as flood defences. Examples are weirs, sluices controlling normal water levels, locks, trash screens and offshore breakwaters. ... 3.7 Condition of Flood Defences Flood defences and other operating structures shall be assumed to act perfectly. There shall be no consideration of operational or structural failure, nor of blockage.”
“Flood Events: Consider the following flood events when defining ABDs for the Flood Map: 1 in 100 annual probability (1% AP) fluvial flood... When considering the 1% AP fluvial flood, assume a worst case scenario... State of the catchment area ...: Identification of ABDs shall consider the present day state of a catchment ... area, taking into account the possible obstruction or diversion of floodwater offered by infrastructure and the built environment, as well as effect of flood defences. Take into account infrastructure and the built environment when assessing the “without defences” flood extents for the Flood Map. This condition also includes the basic river and coastal infrastructure, such as: • ... • structures whose purpose is to aid normal operation rather than provide flood protection. Such structures include weirs, sluices, lock, trash screens and offshore breakwaters; Flood Defences to include in the ABD assessment Flood defences to consider can be categorised as: • formal defences and • de facto defences Formal defences are structures formally maintained as flood defence. The primary purpose of those structures would be to limit the spread of flood water over land. Example structures are: • raised walls, including demountable walls; • embankments, including coastal shingle ridges; • barriers and barrages; • engineered or controlled flood storage areas, created by a structure of combination of structures; • land drainage pumping stations De facto defences De facto defences are other structures that provide secure barriers to the flow of flood waters, in the manner of a formal flood defence, but for which this flood defence function is a by-product, perhaps unintentional, of their primary purpose... Water supply reservoirs may be included where formal agreement for flood control is in place. ... Condition of Flood Defences: Assume that flood defences act perfectly during flood events. This includes opening or closing flood gates and the like where this is intended. There shall be no consideration of: • Operational or structural failures; flood risk allowing for the probability of structural failure is assessed by the National Flood Risk Assessment (NaFRA) methodology. This element of the Flood Risk Mapping Strategy is separate from the identification of ABDs; • failures due to blockage; • flooding due to seepage through flood defences or their foundations. This criterion is adopted so that the Flood Map has a clear objective basis. Including breaching scenarios introduces elements of subjective judgement into the Flood Map which are not desirable.”
“This policy defines what is included on the Flood Map. The Flood Map comprises the following data: The Flood Map comprises the following data: 1. Flood Zones Flood Zones are areas which could be affected in the event of flooding from rivers ... Flood zones ignore the presence of the following types of flood defence and structures: • Raised walls and embankments • Barriers, barrages and gates • Engineered or controlled flood storage areas • Pumping stations Other infrastructure, including bridges, culverts, engineered channels and bypass channels, and embankments (e.g. railway or road embankments) that are not flood defences, is included in all modelling and mapping of flood zones (apart from our national generalised modelling produced in 2004). The Flood Zones policy statement details the purpose and development of flood zones. 2. Flood Defences The Flood Map shows the location of the following types of flood defences: • Raised walls and embankments • Tidal barriers and barrages • Engineered or controlled flood storage areas • Pumping stations All other types of flood defences or structures, or natural or manmade infrastructure, including bridges, culverts, engineered channels and bypass channels, embankments that are not flood defences, and natural washlands, are not shown on the Flood Map.”
“Areas benefiting from flood defences Areas benefiting from flood defences are defined as those areas which benefit from formal flood defences in the event of flooding from rivers with a 1% (1 in 100) chance in any given year. ... If the defences were not there, these areas would be flooded. In mapping areas benefiting from flood defences, we assume that flood defences and other operating structures act perfectly and give the same level of protection as when our assessment of the area was carried out....If the defence needs to be operated (for example, a flood gate) then an assessment of an area benefiting from flood defences assumes that the defence will be appropriately operated.” “Explanatory Note Background Flood defences do not completely remove the chance of flooding. They can be overtopped by water levels which exceed the capacity of the defences. They can be breached if the condition is inadequate or conditions are harsh. Some defences – such as flood gates – can fail to operate, or manual operation may not be put into effect... Types of Flood Defences We may map areas benefiting from the following types of flood defence: • Raised walls and embankments • Tidal barriers and barrages • Engineered or controlled flood storage areas • Land Drainage Pumping stations We will not map areas benefiting from other infrastructure, such as bridges, culverts, engineered channels and bypass channels, and embankments that are not flood defences, as these structures are included in modelling and mapping Flood Zones. This does not mean that these structures cannot reduce or increase flood risk.” “Areas benefiting from flood defences Areas benefiting from flood defences are defined as those areas which benefit from formal flood defences in the event of flooding from rivers with a 1% (1 in 100) chance in any given year. ... If the defences were not there, these areas would be flooded. In mapping areas benefiting from flood defences, we assume that flood defences and other operating structures act perfectly and give the same level of protection as when our assessment of the area was carried out....If the defence needs to be operated (for example, a flood gate) then an assessment of an area benefiting from flood defences assumes that the defence will be appropriately operated.” “Explanatory Note Background Flood defences do not completely remove the chance of flooding. They can be overtopped by water levels which exceed the capacity of the defences. They can be breached if the condition is inadequate or conditions are harsh. Some defences – such as flood gates – can fail to operate, or manual operation may not be put into effect... Types of Flood Defences We may map areas benefiting from the following types of flood defence: • Raised walls and embankments • Tidal barriers and barrages • Engineered or controlled flood storage areas • Land Drainage Pumping stations We will not map areas benefiting from other infrastructure, such as bridges, culverts, engineered channels and bypass channels, and embankments that are not flood defences, as these structures are included in modelling and mapping Flood Zones. This does not mean that these structures cannot reduce or increase flood risk.”
“Policy Flood Zones show areas of land that could flood from rivers and/or from the sea. They identify the extents over which flooding could occur, if the flooding is not constrained by flood defences.” “Purpose Flood Zones are designed for strategic spatial and development planning purposes in England. The definition of each Flood Zone originates from .. (PPS 25) ... We are not required to map the outer boundary of Flood Zone 3b...” “Objectives 1. To ensure a consistent approach to production, amendment and communication of Flood Zones 2. To ensure that only appropriate data are used for production of Flood Zones and that its source and quality are recorded. 3. To ensure that Flood Zones meet the requirements of planning policy; in particular, that Flood Zones are: • Not constrained by formal raised flood defences • Consistent and reliable • Defensible and auditable • Probability-based • Precautionary.” “Background ... We interpret PPS25 to mean that flooding is not constrained by formal raised flood defences. Therefore the Flood Zones ignore the effect of defences in reducing the probability of flooding but do not underestimate the extents of flooding where defences increase the area potentially at risk. Other types of flood defences or infrastructure (whether or not their primary purpose is flood alleviation) such as engineered river channels, bypass channels, culverts and bridges are considered as existing infrastructure for the purpose of Flood Zones. In principle this means they are included when modelling and mapping Flood Zones. This principle also applies to embankments that are not flood defences, although any pathways through the embankment should be taken into account.”
“17. It has long been established that a planning authority must proceed upon a proper understanding of the development plan: see, for example, Gransden & Co Ltd v Secretary of State for the Environment(1985) 54 P & CR 86 , 94 per Woolf J, affd(1986) 54 P & CR 361 ; Horsham DC v Secretary of State for the Environment(1991) 63 P & CR 2319 , 225-226 per Nolan LJ. The need for a proper understanding follows, in the first place, from the fact that the planning authority is required by statute to have regard to the provisions of the development plan: it cannot have regard to the provisions of the plan if it fails to understand them. It also follows from the legal status given to the development plan by section 25 of the 1997 Act. The effect of the predecessor of section 25, namelysection 18A of the Town and Country (Planning) Scotland Act 1972 (as inserted bysection 58 of the Planning and Compensation Act 1991 ), was considered by the House of Lords in the case of City of Edinburgh Council v Secretary of State for Scotland 1998 SC (HL) 33,[1997] 1 WLR 1447 . It is sufficient for present purposes to cite a passage from the speech of Lord Clyde, with whom the other members of the House expressed their agreement. At p.44, 1459, his lordship observed: “In the practical application of sec. 18A it will obviously be necessary for the decision-maker to consider the development plan, identify any provisions which are relevant to the question before him and make a proper interpretation of them. His decision will be open to challenge if he fails to have regard to a policy in the development plan which is relevant to the application or fails properly to interpret it.” 18. In the present case, the planning authority was required by section 25 to consider whether the proposed development was in accordance with the development plan and, if not, whether material considerations justified departing from the plan. In order to carry out that exercise, the planning authority required to proceed on the basis of what Lord Clyde described as “a proper interpretation” of the relevant provisions of the plan. We were however referred by counsel to a number of judicial dicta which were said to support the proposition that the meaning of the development plan was a matter to be determined by the planning authority: the court, it was submitted, had no role in determining the meaning of the plan unless the view taken by the planning authority could be characterised as perverse or irrational. That submission, if correct, would deprive sections 25 and 37(2) of the 1997 Act of much of their effect, and would drain the need for a “proper interpretation” of the plan of much of its meaning and purpose. It would also make little practical sense. The development plan is a carefully drafted and considered statement of policy, published in order to inform the public of the approach which will be followed by planning authorities in decision-making unless there is good reason to depart from it. It is intended to guide the behaviour of developers and planning authorities. As in other areas of administrative law, the policies which it sets out are designed to secure consistency and direction in the exercise of discretionary powers, while allowing a measure of flexibility to be retained. These considerations point away from the view that the meaning of the plan is in principle a matter which each planning authority is entitled to determine from time to time as it pleases, within the limits of rationality. On the contrary, these considerations suggest that in principle, in this area of public administration as in others (as discussed, for example, in R (Raissi) v Secretary of State for the Home Department[2008] QB 836 ), policy statements should be interpreted objectively in accordance with the language used, read as always in its proper context. 19. That is not to say that such statements should be construed as if they were statutory or contractual provisions. Although a development plan has a legal status and legal effects, it is not analogous in its nature or purpose to a statute or a contract. As has often been observed, development plans are full of broad statements of policy, many of which may be mutually irreconcilable, so that in a particular case one must give way to another. In addition, many of the provisons of development plans are framed in language whose application to a given set of facts requires the exercise of judgment. Such matters fall within the jurisdiction of the planning authorities, and their exercise of judgment can only be challenged on the ground that it is irrational or perverse (Tesco Stores Ltd v Secretary of State for the Environment[1995] 1 WLR 759 , 780 per Lord Hoffmann). Nevertheless, planning authorities do not live in the world of Humpty Dumpty: they cannot make the development plan mean whatever they would like it to mean. “In the practical application of sec. 18A it will obviously be necessary for the decision-maker to consider the development plan, identify any provisions which are relevant to the question before him and make a proper interpretation of them. His decision will be open to challenge if he fails to have regard to a policy in the development plan which is relevant to the application or fails properly to interpret it.” 20. The principal authority referred to in relation to this matter was the judgment of Brooke LJ in R v Derbyshire County Council, Ex p. Woods [1997] JPL 958, at 967. Properly understood, however, what was said there is not inconsistent with the approach which I have described. In the passage in question, Brooke LJ stated: “If there is a dispute about the meaning of the words included in a policy document which a planning authority is bound to take into account, it is of course for the court to determine as a matter of law what the words are capable of meaning. If the decision maker attaches a meaning to the words they are not properly capable of bearing, then it will have made an error of law, and it will have failed properly to understand the policy.”
“The main outcome of the SFRA and associated Sequential Testing of the Strategic Locations, undertaken in accordance with national guidance, is that Pomona Island is not a preferred location for residential development. For this reason, neither this Policy nor Policy SL1 makes an allowance for this location to contribute towards the Council’s housing land target, above what has already been permitted by way of the outstanding full planning permission for 546 residential units on part of Pomona which does not expire until May 2012.”
“Flood risk management measure Any measure which reduces flood risk such as flood defences.”
“9. ... the growth of built development within flood plains over the centuries has increasingly required engineering works to defend properties against the risk of flooding.... 10 ... While flood defence works can reduce the risk of flooding, they cannot eliminate it. For example, a flood bank designed to contain a particular level of flood will be overtopped by one that is more severe... It is important that those who plan and occupy development in flood risk areas are aware of the remaining risk, despite the presence of flood defences... 11. Continued construction of hard-engineered flood defences to protect development in areas exposed to frequent or extensive flooding may not be sustainable in the long term....”
“De facto defence A structure that provides a flood defence function but for which flood defence is a secondary or indirect purpose.” “Formal defence A formal defence asset that directly limits the spread of flood water and, primarily because of this function, is owned and/or maintained by its present owner, regardless of whether this is the Environment Agency, another authority or a private owner.”
“Formal defences are structures formally maintained as flood defence. The primary purpose of those structures would be to limit the spread of flood water over land.”
“Structures whose purpose is to aid normal operation rather than provide flood protection shall not be mapped as flood defences. Examples are weirs, sluices controlling normal water levels, locks, trash screens and offshore breakwaters.”
“A structure on river, canal etc. with an adjustable gate or gates by which the volume or flow of water is controlled; a gate in such a structure.”
“Objectives 1. To ensure a consistent approach to production, amendment and communication of Flood Zones 3. To ensure that Flood Zones meet the requirements of planning policy; in particular, that Flood Zones are: • Not constrained by formal raised flood defences • Consistent and reliable • Defensible and auditable” 94. Ms Kate Marks, National Office, Head of Flood and Coastal Risk Mapping and Modelling, in her email dated15 October 2010 , confirmed that the Flood Zone mapping had to be “a nationally consistent product”. 95. In concluding that the Defendant’s policies are intended to define and categorise flood defences, between “formal” and “de facto” defences, I have also had regard to the purpose of these policies. As I have already described, the mapping of Flood Zones triggers the Sequential Test, which in turn steers new development away from the higher risk Flood Zones at all stages of the planning process. Since Flood Zoning may have a drastic impact upon future development, it is appropriate that both PPS25, and the Defendant’s own policies, are careful to limit the extent of the flood defences which are to be disregarded when mapping Flood Zones. Both are required, by EU law, to apply the precautionary principle in a proportionate way (see the ‘Communication from the European Commission on the precautionary principle’, cited above), to strike a balance between risk avoidance on the one hand, and economic development on the other. 96. This approach on the part of the Government and the Defendant should not be misconstrued as minimising the importance of effective flood risk assessment, precautions and prevention. It is important to distinguish between the specific function of Flood Zone mapping, which is relatively narrow in scope, and the wider function of flood risk mapping, in the Flood Map and the National Flood Risk Assessment, which assesses the probability of flooding, taking all relevant factors into account. The Defendant’s current strategy, as set out in its ‘Flood and Coastal Risk Management Risk Mapping Strategy 2010 – 2015’ is to replace the Flood Map with mapping developed using “probabilistic methods”
“... we mapped flood risk in a way that did not enable the range of flood risk for a particular location to be understood, and did not take into account all the factors which could affect that risk. Our Flood Map shows an outline of an area at risk, but not the distribution of risk within that outline. An area is either at risk from a flood of a particular magnitude, or not. This way of looking at mapping is an example of what is sometimes called a deterministic approach. The Flood Zones are an example of this approach... .... We have begun using a way of assessing risk that provides a far more realistic understanding of how likely an area is to flood. With this method, we can now talk about the distribution of the likelihood of flooding within an area. In other words, we can predict the likely extent of flooding in much more detail. This method is an example of what is sometimes called a probabilistic approach.”
“Formal defence A formal defence asset that directly limits the spread of flood water and, primarily because of this function, is owned and/or maintained by its present owner, regardless of whether this is the Environment Agency, another authority or a private owner.” “Formal defences are structures formally maintained as flood defence. The primary purpose of those structures would be to limit the spread of flood water over land.” 102. On the evidence, the sluices are not owned or maintained by the Claimants for the purpose of providing a formal defence against flooding. Their primary purpose is to regulate water levels in the Canal, not to limit the spread of flood water over land. 103. In my judgment, the Defendant’s internal emails indicate that its officers did not give adequate consideration to the distinction between ‘formal’ and ‘de facto’ defences. 104. My conclusion is, therefore, that the Defendant failed properly to interpret, apply or have regard to its own policy when it classified the sluices on the Canal as formal flood defences, and based its Flood Zone assessment and mapping on the assumption that the sluices would fail and remain closed. 105. Furthermore, for the same reasons, it was irrational, in a Wednesbury sense, for the Defendant to conclude that the sluices came within the descriptions of “formal defences” as set out in its policies. Ground 2 106. Since the Claimants have succeeded on Ground 1, they do not need to pursue Ground 2. However, in case the claim goes further, I have set out my conclusions on Ground 2 also, proceeding on the alternative basis that the sluices are ‘formal defences’ under the Defendant’s policies. 107. The Claimants alleged that the Defendant erred in: a) failing to take into account a relevant consideration, namely, the minute risk that all four sluice gates in any one sluice would fail to open; b) insofar as it did take the agreed evidence into account, it was irrational and disproportionate to conclude that the flood risk should be assessed on the basis that all the sluice gates might fail in the closed position; c) insofar as its conclusion was in accordance with its policy, it adopted an inflexible approach, slavishly adhering to its policy, which was inconsistent with the approach adopted in respect of other watercourses. 108. It is common ground that the Claimants were given the opportunity to make informal representations and submit evidence to the Defendant whilst it was considering how to map the Canal. 109. The Defendant disclosed a number of internal emails which candidly revealed the exchanges of views and deliberations among its officers, leading up to the decision. The final word in the Defendant’s deliberations is set out in an email from Ms Kate Marks, National Office, Head of Flood and Coastal Risk Mapping and Modelling, dated15 October 2010 which reads: “The Flood Zones as described in PPS25 are deterministic outputs and undefended in line the precautionary principle. They are designed to be a ‘worst case’ undefended scenario to provide initial knowledge that is then built upon with further residual risk analysis and local knowledge of conditions through mechanisms such as the EA ABD product, and SFRA work by the local authority. However, this knowledge is in addition to the Flood Zones, and unless it strictly meets the requirements of the Flood Zones products, should not be used to update it. I understand that you feel you’re a ‘special case’ and however the Flood Zones, which is a national product, doesn’t (and in fact shouldn’t) accommodate special cases. Following your logic, it could be argued that the Thames Barrier is also a ‘special case’ being a well maintained structure with a low risk of failure, but that isn’t treated as a special case either and the Flood Zones for London show the undefended scenario in line with the rest of the country. If we therefore decided to take a special case in one location, what this would then mean elsewhere is a) increased cost to the UK taxpayer because we would be forced to re-run flood zones all over the country in order to maintain its status as a nationally consistent product and b) it would undermine the objectives and therefore confidence of PPS25 because it would not represent the precautionary worst case scenario. As per your initial discussions with Iain from December last year ... I would like to reiterate the point that the undefended scenario for the sluice gates is that they are closed. ....in your discussions with key partners you can bring in the additional information you and they have on risk such as the ABD which I hear assumes the gates work as designed and I understand that for the Manchester Ship Canal then the whole of Flood Zone 3 would also be shown as an ABD when it comes to publishing the data on our website. You may wish to focus your discussions with partners therefore on the different evidence base you have for theoretical (Flood Zones) risk, vs. you (and your partners’) enhanced evidence base for a reduced residual risk based on operating rules and likelihood of failure.” 110. In my judgment, it is apparent from the internal emails disclosed to the Court that the Defendant did take into account the agreed evidence that the risk of failure of the sluice gates was remote when making their decision. However, it correctly concluded that, under PPS25 and its own policies, it had to be assumed that the formal flood defences had failed when mapping Flood Zones. So the reliability of the sluice gates was not a relevant factor at that stage of the assessment. 111. It is clear from the emails that the Defendant did apply its mind to the question whether, for Flood Zone mapping, the sluice gates should be assumed to be open or closed, wholly or partially. 112. On the assumption that these sluices were formal flood defences, Ms Marks was correct to conclude that, in accordance with the policies, it has to be assumed that the sluices fail to operate. The sluices prevent flooding by opening, thus allowing high waters to pass safely down the Canal. The worst case scenario is that the sluices cannot be opened, as the water would then be trapped in the pond created by the locks and the sluice, and it would eventually overflow the banks of the Canal. Ironically, on this scenario, the sluices and the locks artificially create a flood since, if they did not exist, the water could flow freely down the Canal. 113. The Claimants contended that this was irrational and disproportionate in a Wednesbury sense. In my judgment, the Defendant applied the policies correctly; it is the policies which have resulted in the outcome which the Claimants consider to be irrational and disproportionate. The Claimants have not challenged the lawfulness of the policies in this claim for judicial review. 114. In my judgment, the Defendant was required to apply PPS25 on the mapping of Flood Zones, which considerably limited the scope of its discretionary powers. As a public body administering a sizeable project, it was desirable in the interests of good administration for it to issue its own policies setting out the way in which it would implement PPS25. It was required to adhere to its own policies, unless there was a legitimate reason to depart from them. On the other hand, it should not apply its policies with a rigidity which excluded the possibility of exceptions. It would also be acting unfairly if it was capricious or arbitrary in deciding whether to allow exceptions in individual cases. 115. The emails showed that the Defendant considered whether it should treat the Canal as an exception to its policy, as requested by the Claimants, because of its unique characteristics, and taking into account that the risk of flooding was very low. Ms Marks concluded that there were no grounds upon which to make an exception, and if the Canal was treated as a special case, this would undermine the national consistency of the Flood Zones and the Flood Map. In my judgment, this conclusion cannot be impugned as unlawful. 116. The Defendant did consider the Claimants’ case that other sites had been treated differently and more favourably and it acknowledged privately that there were inconsistencies in the way it was applying its policies. Mr Lukey said in his witness statement that this debate had prompted a review of other comparable sites. Unfortunately for the Claimants, the Defendant has since concluded that the Upper Thames sluices should also have been categorised as formal flood defences. Judging from the summaries I have been shown in relation to other sites, in the ‘Manchester Ship Canal Flood Risk Mapping Comparable Study’ (2010) and an internal paper called ‘Summary of approaches’ by Tilak Peiris, who led the team responsible for producing the Flood Map, there may have been inconsistencies in the application of the policy, although I accept that it is not possible to reach a firm conclusion in the absence of the detailed assessments, as each site assessment is fact-sensitive. Judging from the internal emails, the Defendant’s staff experience genuine difficulty in correctly understanding and applying the policies to specific sites. I do not consider that this provides a sufficient basis upon which to conclude that the decision in this particular case was unlawful. 117. For the reasons set out above, the Claimants have failed to establish Ground 2 of their claim. River/Canal 118. After the hearing, but before judgment, I asked the parties for submissions on a further issue, namely, the appropriate way to assess a canal under PPS25 and the Defendant’s policies when conducting the Flood Zoning exercise. 119. The Flood Map “only covers river and sea flooding” (Glossary), not flooding from the other sources set out in Annex C. This is confirmed elsewhere in PPS25: a) “The Flood Zones refer to the probability of flooding from rivers, the sea and tidal sources” (paragraph 17, FN 6) b) “These Flood Zones refer to the probability of sea and river flooding only” (D2). 120. The other sources of flooding set out in Annex C (e.g. flooding from artificial sources such as canals), are to be assessed at a later stage, in the Strategic Flood Risk Assessments (see D4). 121. The same distinction between river and sea flooding and flooding from other sources was made in PPG25, paragraph 30. It was anticipated that local assessments of flood risks from other sources would be required in addition. The special characteristics of canals were recognised in paragraphs 37 and 38. 122. The Defendant’s policy 541_05 confirms that Flood Zones only cover flooding from rivers and the sea and advises that navigation channels should be treated as part of the infrastructure: “Flood Zones show areas of land that could flood from rivers and/or from the sea. They identify the extents over which flooding could occur, if the flooding is not constrained by flood defences. ... Flood Zones do not provide information on flooding from groundwater or other sources. State of the catchment/tidal area Identification of ABDs shall consider the present day state of a catchment/tidal area, taking into account the possible obstruction or diversion of flood water offered by infrastructure and the built environment, as well as the effect of flood defences. Take into account infrastructure and the built environment when assessing the “without defences” flood extents for the Flood Map. This condition also includes the basic river and coastal infrastructure, such as: • river and navigation channels, even if they have been purposely engineered to aid flood alleviation”
“I have always considered canals as infrastructure and therefore should remain in place and operated in whatever way they are normally to determine the flood zone.” 125. Ms Shirley Greenwood, FCRM Policy Adviser Mapping and Modelling, in an email dated13 April 2010 , agreed that the Defendant’s policy was to treat all watercourse ‘channels’ as ‘infrastructure’ which are modelled to remain in normal operation when mapping Flood Zones. However, she distinguished between the watercourse itself and the hydraulic structures on the watercourse, and concluded that “flood defence sluices, gates etc.” on a watercourse which protect from flooding should be disregarded when mapping Flood Zones, consistently with the treatment of other flood defences. 126. A somewhat different approach was adopted in a draft “Question and Answer” document which states: “Why have we decided to map this information now? In its upper reaches, the Manchester Ship Canal is formed from the rivers Irwell and Mersey. It is an important strategic watercourse draining a large portion of the Greater Manchester area. It also plays an important part in managing flood risk in the surrounding areas. As part of our role as the lead body for flood risk management it is crucial that we develop a good understanding of flood risk from the Manchester Ship Canal just as we do from other large watercourses.” 127. Counsel for the Defendant, in their written submissions, developed this approach further (on instructions), arguing that the Canal should be treated as if it was a river for the purposes of the policies, because it receives the flow of several rivers in the vicinity and “has tidal interactions in its lower section”