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Planning Advice Note PAN 69
Planning and Building Standards Advice on Flooding

PLANNING AND BUILDING STANDARDS

35. The planning and building standards systems are both important in addressing flooding issues. An objective of the 'Policy for Architecture for Scotland' (Scottish Executive, 2001) is to ensure that both systems promote and facilitate design quality in development. This would include ensuring that design quality is given greater significance as a material consideration in planning decisions and that the statutory building standards are supportive of the processes of design.

OVERVIEW OF THE PLANNING SYSTEM

36. The planning system is concerned with the future development and use of land and buildings. Planning is primarily a matter for local authorities (planning authorities), so that decisions can be taken at a local level. The three main duties of the planning department within the council are:

• Preparing development plans - which set out how much development may take place, where it will take place and where it is unlikely to be allowed;
• Making decisions on applications for planning permission; and
• Taking action against development that does not have permission.

37. Some minor forms of development are classed as 'permitted development' and don't require a planning application. However, all other proposals defined as 'development' need planning permission, and this includes a wide range of building and engineering work, and changes in the way land and buildings are used. The planning authority has to determine applications in line with the development plan unless a 'material consideration' suggests otherwise. This means a planning matter which is relevant to the application and can include, among other things, national policy, consultees' comments and the effect of the proposal on the environment.

38. Planning authorities are responsible for the control of development under the Town and Country Planning (Scotland) Act 1972 and they have a duty to take account of flooding issues where flooding is a material consideration in a planning decision. Planning applications can be refused on the grounds of flood risk. SPP 1 states that planning should take into account the possible impacts of climate change, for example greater rainfall and increased risk of flooding, in decisions regarding the location of new development and other changes in land use. SPP 1 also emphasises the role of the planning system in supporting prudent use of natural resources.

39. National planning policy is set out in SPP 7: Planning and Flooding and PAN 61: Planning and Sustainable Urban Drainage Systems gives advice on good practice in planning SuDS.

OVERVIEW OF THE BUILDING STANDARDS SYSTEM

40. Building control in Scotland has recently undergone a major review and a new system will come into force on 1st May 2005 to replace the Building (Scotland) Act 1959 and the Building Standards (Scotland) Regulations 1990. A new agency, the Scottish Building Standards Agency (SBSA), has been established to fulfil certain central functions. The Act will facilitate a system that will be more responsive to the needs of industry and the public and, due to the new structure of the standards, will allow more flexibility for designers to promote new and innovative design. Further information can be obtained from the Agency web site at www.sbsa.gov.uk

41. The Building (Scotland) Act 2003 gives Scottish Ministers the power to make Building Regulations to:

• secure the health, safety, welfare and convenience of persons in or about buildings and of others who may be affected by buildings or matters connected with buildings,
• further the conservation of fuel and power,
• further the achievement of sustainable development.

42. The building standards system complements the planning system. Proposals to erect a new building, to alter or extend an existing building, to convert a building or to demolish a building will normally require a building warrant before work starts. A warrant will normally be granted if the work proposed meets the functional standards set by the Building (Scotland) Regulations 2004.

43. Two Technical Handbooks, one covering domestic buildings and the other non-domestic buildings give guidance on achieving the standards. The Handbooks will be produced in hard copy, CD-ROM and on the SBSA web site and are programmed for publication by the end of October 2004. However until 30th April 2005, the Building Standards for compliance with the Building Standards (Scotland) Regulations 1990, as amended, are in force and all building warrant applications up until that date must comply with the 6th amendment of these Regulations.

44. Any reference in this document to building regulations and guidance on building standards, unless mentioned otherwise, is to the new system.

DEVELOPMENT PLANS

45. Information on flood risk, including flood risk maps, should be an input to the preparation of development plans from the beginning. For structure plans the key issue will probably be to factor information on flooding into the preparation of the strategy and use it as a constraint on the strategic land allocations. Structure plans cannot assume that flooding is a matter to be addressed only in local plans or through development control. If strategic development opportunities and allocations are made and it is subsequently discovered that they cannot be delivered without a flood prevention scheme, then SPP 7 says (at paragraph 3) it is unlikely that the Scottish Executive would support a flood prevention scheme which was required just to defend new development. In accordance with the SPP however, if allocations are considered where the risk of watercourse or coastal flooding is an issue, landraising (see paragraphs 110 to 112) is likely to offer a permanent and maintenance-free means of addressing flooding.

46. SPP 7 also says that structure plans can contribute to the wider objectives of management of the water environment and floods. This could include safeguarding major areas and storage capacity of the functional flood plain from development; considering options such as coastal realignment; and linking with river basin management planning under the Water Environment and Water Services (Scotland) Act 2003 (WEWS Act).

47. Proposals and policies for structure and local plans should be based on the Risk Framework in SPP 7. This does not set out a rigid sequential approach for identifying sites, but in applying it through their detailed policies, planning authorities may consider that sites with a low probability of flooding are likely to be preferable to sites with a higher probability, other things being equal.

48. SPP 7 also says that the potential for sites to flood must be considered in local plans. At each review, the plan should guide development away from land at risk of flooding, based on areas identified in the structure plan and any other relevant sources of information. Paragraph 43 of the SPP sets out in detail what the local plan should cover. A number of existing local plans contain clear policies which identify land with a high probability of flooding within the plan area and set out the implications for future development. For example, see the Strathearn Local Plan policy below.

49. The depiction of areas at risk of flooding on local plan maps should be carefully considered, taking into account the degree of certainty in the information, the likelihood of it being misunderstood and the potential for blight. It may sometimes be more appropriate to identify areas where consultation with SEPA may be required than to identify areas of flood risk. However, when the second generation of flood risk maps are published and available in the public domain planning authorities may wish to consider including the flood risk contours on local plan proposals maps to help in application of the risk framework set out in SPP 7. This would help to clearly highlight areas where a flood risk assessment is likely to be needed, and would also help identify sites where development is unlikely to be acceptable. Where a local authority is considering promoting a flood prevention scheme, this should also be signalled in the development plan.

50. The Arun District Local Plan also includes a map of the district indicating the Environment Agency's flood plain data, advising that the map is the latest available at the time the local plan was adopted and that updated flood plain data will be available on the Environment Agency website. The Spelthorne Borough Local Plan provides an example of a criteria based flooding policy.

SUPPLEMENTARY PLANNING GUIDANCE

51. Planning authorities may decide to provide a brief separate guidance note bringing together advice on planning and flooding. This type of supplementary planning guidance may be particularly helpful as an interim measure if the Council's policy on planning and flooding has not yet been incorporated in the development plan. See Clackmannanshire Council's Planning and Flooding Supplementary Advice Note, at www.clacksweb.org.uk/document/advnote9.pdf for an example of supplementary guidance dealing with flooding, and the City of Edinburgh's Development Quality Handbook - Planning and Flooding, August 2001.

52. Guided by policies in the development plan or supplementary guidance, developers should be aware at an early stage whether development on a particular site is likely to be acceptable or not. SPP 7 sets out the national policy context. The initial consideration of flood risk and the potential need for a flood risk assessment may be indicated by factors such as:

• the characteristics of the site;
• the use and design of the proposed development;
• the size of the area likely to flood;
• depth of water, likely flow rate and path, rate of rise and duration;
• existing flood prevention measures - extent, standard and maintenance regime;
• an allowance for freeboard;
• cumulative effects of development, especially the loss of flood storage capacity;
• cross boundary effects and the need for consultation with adjacent authorities;
• effects of a flood on access, including by emergency services;
• effects of a flood on proposed open spaces including gardens; and
• the extent to which the development, its materials and construction is designed to be water resistant.

53. Planning authorities must consult SEPA before granting planning permission where it appears to the planning authority that the development is likely to result in a material increase in the number of buildings at risk of being damaged by flooding. SEPA will give the planning authority clear advice where they consider that there is a significant flood risk, and in those circumstances if the planning authority intends to grant planning permission, it will need to notify Scottish Ministers.

Figure 1: PLANNING APPLICATIONS WHERE THERE MAY BE A FLOOD RISK

* In addition to SEPA, statutory consultations may be required with the water and sewerage authority and adjacent local authorities.

For further advice see Appendix D.

54. Some proposals for development or flood mitigation will be likely to affect the risk of flooding in an adjoining local authority area. Where this is the case, the neighbouring planning authority should be consulted. (See GDPO, Article 15) This will be particularly important where there may be cumulative impacts.

55. Calculating an allowance for freeboard (see glossary) is a specialist task which is best undertaken as part of a developer's flood risk assessment. SEPA's advice to planning authorities will incorporate their view on the appropriate allowance. The appropriate level of freeboard will take account of the flow and turbulence of the flood water, the speed, direction and duration of the wind, plus the extent of the water over which the wind blows. It is therefore not possible to give a universal figure for freeboard, but it should be determined through a consistent approach such as that adopted by the Environment Agency in their 'Fluvial Freeboard Guidance Note' 1999. Guidance on carrying out a flood risk assessment is available on SEPA's website www.sepa.org.uk

BUILDING WARRANT APPLICATIONS WHERE THERE MAY BE A FLOOD RISK

56. The Building Standards also require developers to take account of flooding.

Building Standard 3.3 states:

Every building must be designed and constructed in such a way that there will not be a threat to the building or the health of the occupants as a result of flooding and the accumulation of ground water.

57. In general all proposed building sites should be appraised initially to ascertain the risk of flooding of the land and an assessment made as to what effects the development may have on adjoining ground.

58. Ground below and immediately adjoining a building that is liable to accumulate floodwater or ground water requires treatment to be provided against the harmful effects of such water. The ground immediately adjoining a building means the area where any ground water would affect the structural stability of the building. Treatment could include a field drain system.

59. The drainage of ground water may be necessary for the following reasons:

• to increase the stability of the ground;
• to avoid surface flooding;
• to alleviate subsoil water pressures likely to cause dampness to below-ground accommodation;
• to assist in preventing damage to foundations of buildings;
• to prevent frost heave of subsoil that could cause fractures to structures such as concrete slabs.

The selection of an appropriate drainage layout will depend on the nature of the subsoil and the topography of the ground.

Building Standard 3.4 states:

Every building must be designed and constructed in such a way that there will not be a threat to the building or the health of the occupants as a result of moisture penetration from the ground

60. Water is the prime cause of deterioration in building materials and the presence of moisture encourages growth of mould that is injurious to health. Ground water can penetrate building fabric from below, rising vertically by capillary action. The effects of this rising damp are immediately recognisable. There may be horizontal 'tidemarks' sometimes several feet above the floor; below it the wall is discoloured with general darkening and patchiness. There may also be loose wallpaper, signs of mould growth and deterioration of plaster. Hygroscopic salts brought up from the ground tend to concentrate in the 'tidemark'.

61. Buildings therefore need to be constructed in such a way that rising damp neither damages the building fabric nor penetrates to the interior where it may constitute a health risk to occupants. The Technical Handbooks provide guidance on methods of preventing moisture from penetrating to the interior of buildings.

DRAINAGE ASSESSMENT

62. When flooding is an issue the provision of drainage is unlikely to be straightforward and a drainage assessment may be required. This is defined in SPP 7 as "a statement of the drainage issues relevant to a proposal and the suitable means of providing drainage. The length and detail should be proportionate to the issues. As appropriate it may include existing drainage systems and problems, infiltration, groundwater, surface water flow, foul and storm water disposal, SuDS and drainage related flooding issues (may also be called a Drainage Impact Assessment)." The assessment should demonstrate that the proposal would have a neutral or better effect on the risk of flooding. Planning authorities have a duty to consult Scottish Water and SEPA on appropriate planning applications, and where drainage is a significant issue, applicants should provide a drainage assessment as part of their supporting material.

63. The experience of drainage assessments in north-east Scotland shows that they are tailored to the circumstances of each site and proposed development. The issues typically addressed include:

• Brief description of the site and location;
• Pre-development foul and surface water drainage provision, including field drains;
• Surface water calculations;
• Surface water disposal, including SuDS design and flow attenuation;
• Foul drainage design proposal and standards;
• Maintenance regime;
• Any agreements reached with Scottish Water and SEPA.

The North East Scotland Flood Appraisal Group's Guidance for Developers and Regulators on Drainage Impact Assessment contains useful advice on the roles and responsibilities of the different parties in relation to drainage assessment and drainage measures. Details are included in the References section of this PAN.

64. The potential of garden ground and other open space to become waterlogged or suffer from localised flooding is something to be considered from the earliest stages of site proving. The problem may not be obvious from a site inspection as it often occurs intermittently, possibly on a seasonal basis or when rainfall is intense. It may be related to local fluctuations in the water table. Problems can arise or be made worse if the construction process involves re-grading, disturbing the soil profile or compacting the ground with heavy plant. The layout of buildings can also be a contributory factor because foundations can impede the flow of sub-surface water.

65. For large developments, proposals in areas where drainage is constrained or otherwise problematic, and where building works may affect drainage off-site, it is good practice for a drainage assessment (also referred to as drainage impact assessment) to be submitted with the planning application. The purpose is to assess the potential for flood risk and pollution, and show that a satisfactory means of waste and surface water drainage can be provided. Planning authorities may attach conditions but the developer has the primary responsibility for ensuring that the land and development are fit for purpose.

66. The assessment should take account of the expected impact of climate change. A cross-disciplinary project entitled AUDACIOUS is currently underway, bringing together hydrologists, building drainage and sewerage engineers, health, social and infrastructure economic specialists, to develop tools and procedures for the assessment and mitigation of the effects of climate change on urban drainage systems. See References for more information.

67. At the outline planning application stage the drainage assessment should indicate whether the sub-soil is suitable for use of infiltration SuDS, and the scale of system required. It should also provide other information including an assessment of any risk of flooding; highlight how the drainage system is to be integrated into the surrounding landscape; and demonstrate good ecological practice, e.g. identifying opportunities for habitat enhancement. Further advice is provided in PAN 61 from paragraph 23.

68. Planning authorities set out their approach to drainage and flooding through the development plan. In Aberdeen and Aberdeenshire, for example, the structure plan requires that SuDS form part of all new planning proposals. The Sustainable Urban Drainage Scottish Working Party is currently developing a national specification for drainage assessment.

69. A building warrant is also required prior to construction of surface water or wastewater drainage work serving a building and it is recommended that an early assessment of options is made before the design is developed too far. Building regulations cover work within the curtilage of a building only but drainage systems can impact on a much wider area. Designers should be aware of implications to the environment as a whole, when designing drainage systems.

70. Building Standard 3.6 relates to the design and construction of surface water drainage systems:

Every building, and hard surface within the curtilage of a building, must be provided with a drainage system that will: a) ensure the hygienic disposal of surface water without endangering the building and the health and safety of the people in and around the building; and b) have facilities for the separation and removal of silt and grit from the system.

71. Conventional piped surface water drainage systems can cause flooding and pollution and disrupt the water cycle to the detriment of water resources and the natural environment. An alternative approach is needed to reach a more sustainable solution. Sustainable drainage is a concept that focuses decisions about drainage on the environment and people. The concept takes account of the quantity and quality of surface water run-off and the amenity value of surface water in the urban environment. Sustainable Urban Drainage Systems (SuDS) are physical structures that are designed to store, treat and control surface water run-off. See also paragraphs 120 to 125.

72. Building Standard 3.7 relates to the design and construction of wastewater disposal systems:

Every wastewater drainage system serving a building must be designed and constructed in such a way as to ensure the safe and hygienic removal of wastewater from the building, and: a) that facilities for the separation and removal of oil, fat, grease and volatile substances from the system are provided; b) that discharge is to a public sewer or public wastewater treatment plant, where it is reasonably practicable to do so; c) that discharge is to a private wastewater treatment plant or septic tank where discharge to a public sewer or public wastewater treatment plant is not reasonably practicable.

The guidance to this standard provides recommendations for the design, construction and installation of drains and sewers from a building to the point of connection to a public sewer or public sewage treatment works and should also be used for all pipework connecting to a private wastewater treatment plant or septic tank.

73. Building Standards 3.8 and 3.9 relate to the design and construction of wastewater treatment works and infiltration systems:

Every private wastewater treatment plant or septic tank serving a building must be designed and constructed in such a way that it will ensure the safe temporary storage and treatment of wastewater prior to discharge.

Every private wastewater treatment system serving a building must be designed and constructed in such a way that the disposal of the wastewater to ground is safe, hygienic and will not pollute the environment.

74. Where it is not reasonably practicable to connect to a public sewer or a public wastewater treatment plant then discharge should be to a private wastewater treatment plant or septic tank. Treatment plants provide suitable conditions for the settlement, storage and partial decomposition of solids that need to be removed at regular intervals. The discharge can however still be harmful and will require great care when discharging to ground to ensure a suitable level of protection of the environment is achieved. A large number of small sewage treatment works in a limited area is undesirable.

75. The Building Standards also provide guidance where buildings are constructed over existing drainage pipes. Building Standard 3.5 states:

Buildings must not be constructed over an existing drain (including a field drain) that is to remain active.

76. The purpose of this standard is to ensure that existing drains continue to function properly without causing harm to the building or to the health of the occupants. In general, buildings should not be constructed over sewers or drains. They should be re-routed if reasonably practicable or re-constructed where they can not be re-routed. Where it is necessary to build over a public sewer the approval of the Water Authority must be obtained.

ENVIRONMENTAL IMPACT ASSESSMENT

77. 'Flood relief works' are included in Schedule 2 of the Environmental Impact Assessment Regulations. Paragraph 10(h) under 'Infrastructure projects' covers inland-waterway construction not included in Schedule 1, canalisation and flood-relief works where the area of the works exceeds 1 hectare. If it is likely to have significant environmental effects an EIA will be needed. 'Flood relief works' may include flood prevention schemes, landraising and other mitigation measures. The impact of flood relief works is especially dependent on the nature of the location and the potential effects of the surrounding ecology and hydrology. Schemes for which the area of the works would exceed five hectares or more than 2 km long would normally require EIA.

78. Considering environmental issues at an early stage has the advantage that design work can take account of any constraints and opportunities, helping to prevent costly mistakes. Where EIA is required, there are then three broad stages to the procedures - firstly, the developer - which will usually be the local authority, or its agents for a FPS- must compile detailed information about the likely significant environmental effects and measures to address them. Secondly the Environmental Statement (ES) must be publicised, giving all relevant authorities and the public an opportunity to give their views about the project and the ES. The ES, along with any other comments and representations must be taken into account in deciding whether to give consent for the development. Flooding may also be an issue for EIAs of other projects.

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