Flooding

Policy POSP2: Strategic flood risk policy

  1. All new development:
    1. Will be located to minimise flood risk, mitigating any residual risk through design and management measures, and ensuring that flood risk to other areas is not materially increased; and
    2. Will incorporate appropriate surface water drainage mitigation measures, and will implement sustainable drainage (SuDS) principles, to minimise its own risk of flooding and to not materially increase the flood risk to other areas.
  2. Particular care will be required in relation to habitats designated as being of international, national, regional and local importance in the area and beyond which are water sensitive.
  3. Development proposals which would have an adverse impact on flood risk management will be refused.

Reasoned Justification

Flooding can cause damage to property and infrastructure. Tidal flooding can be particularly damaging. The threat of flooding can also cause fear and distress to people and in some cases, flooding can lead to injury[16] and even loss of life. Risks relate not just to property but also to essential infrastructure and utilities required to support development. Flooding can also precipitate pollution, which could have a significant and detrimental impact on the nature conservation interest of the Broads, and the duty of the Authority to protect this resource is an important consideration. Inappropriate flooding can also harm the important habitats and species who rely on/live in the Broads. This can have long term consequences for site maintenance and achieving conservation objectives. On the other hand, flooding is also a natural process within a floodplain and in some circumstances, it can be beneficial to wildlife.

Approximately 82.5% of the Broads Authority Executive Area is covered by flood zone 3 (3, 3a & 3b). This equates to 25,472 hectares. The Broads Authority boundary is tightly drawn around the edge of the floodplain. The extent and nature of flood risk, with significant areas of ‘functional floodplain’, mean that flood risk is a major constraint on development in the Broads.

The flood risk in the Broads is mainly from both fluvial and tidal sources, and the whole character and development in the Broads over many hundreds of years has been closely associated with the water environment and flood risk. Much of the area is defended by flood defence embankments, maintained by the Environment Agency. The flood defences, where they exist, only reduce the risk of flooding and will never eliminate it, and the risk of overtopping or a breach of defences remains.

Reasonable alternative options

No policy

Sustainability appraisal summary

The following is a summary of the assessment of the policy and alternative(s).

A: Having a policy :4 positives. 0 negatives. 0 ? Overall, positive.

B: No policy: 0 positives. 0 negatives. 4 ?

How has the existing policy been used since adoption in May 2019?

According to recent Annual Monitoring Reports, the policy has been used and schemes have been permitted in accordance with the policy.

Why has the alternative option been discounted?

Flood risk is such an issue in the Broads. Having a policy is therefore favoured.

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Policy PODM7: Development and flood risk

  1. Development within the Environment Agency’s flood risk zones[17] will be acceptable only when:
    1. It is compatible with national policy and when the sequential test and the exception test, where applicable, have been satisfied;
    2. A site-specific Flood Risk Assessment, where required, demonstrates an acceptable flood risk and/or suitable flood protection mitigation measures are incorporated into the proposals, where necessary, which can be satisfactorily implemented;
    3. A flood response plan, where required, has been produced that is appropriate and deliverable;
    4. It would not affect the ability for future flood alleviation projects to be undertaken;
    5. It has been informed by an assessment of and respond to existing and proposed ground conditions, groundwater; and
    6. They demonstrate how the design of buildings and the surrounding environment (including pavements, highways, parking areas, driveways, gardens, public green spaces, planting, and drainage) has been planned to be resilient to the ongoing and predicted impacts of climate change, including the design of road surfaces and drainage systems to cope with more frequent episodes of extreme heat and rain.

    2. Site-Specific Flood Risk Assessment

  2. The Site-Specific Flood Risk Assessment will need to meet the requirements of the NPPG and include, demonstrate, or assess:
    1. That the development is safe for its lifetime, taking into account the vulnerability of its users and climate change;
    2. Whether the proposed development will make a significant contribution to achieving the objectives of the Local Plan;
    3. Whether the development involves the redevelopment of previously developed land or buildings and would result in environmental improvements over the current condition of the site;
    4. Whether appropriate measures to ensure resilience to potential flooding have been incorporated into the development;
    5. Whether appropriate, measures to reduce the risk of flooding (on and offsite), including sustainable drainage systems, have been incorporated;
    6. Where the proposal involves the replacement of an existing building, whether the replacement building is located and/or designed without increasing flood risk and, where possible, to reduce the risks and effects of flooding;
    7. Whether acceptable flood risk and/or suitable flood protection mitigation measures are incorporated into the proposals, where necessary, which can be satisfactorily implemented;
    8. Whether the risk of flooding is not increased elsewhere and, wherever possible, is reduced;
    9. That the integrity of existing coastal and river defences is not undermined;
    10. That the development does not reduce the potential of land used for current or future flood management;
    11. Compatibility with the appropriate Catchment Flood Management Plan or Shoreline Management Plan;
    12. Use of development to reduce the risk of flooding through location, layout and design and incorporate sustainable drainage systems to minimise surface water run-off and avoid pollution (see PODM8);
    13. That sites at little or no risk of flooding are developed in preference to areas at higher risk;
    14. There is safe access and egress from the site;
    15. There are management and maintenance plans for flood protection/mitigation measures, including arrangements for adoption by any public authority or statutory undertaker and any other arrangements to secure the operation of the scheme throughout its lifetime;
    16. That the development would not negatively impact on water quality of surface water and ground water; and
    17. There is an adequate, deliverable, and appropriate Flood Response Plan (FRP) – see template and guidance at Appendix 6.
  3. For minor development[18] , a Local Flood Risk Tick Sheet has been produced – see Appendix 7 to assist applicants in producing a flood risk assessment for minor developments.

    4. Relocation to a lower probability of flooding

  4. The relocation of existing development to an undeveloped site with a lower probability of flooding will be permitted where:
    1. The vacated site would be reinstated as naturally functioning flood plain;
    2. The benefits of flood risk reduction outweigh the benefits of leaving the proposed new site undeveloped; and
    3. The development of the proposed new site is appropriate when considered against the other policies of the Local Plan.

    5. Replacement of an existing residential property in flood zone 3a

  5. In the case of the replacement of an existing residential property in flood zone 3a, the replacement dwelling must be on a like-for-like basis, with no increase in the number of bedrooms, on the same sized footprint[19] and wherever possible being relocated in a less vulnerable part of the site.

    6. Sequential test requirements

  6. A site is considered to be reasonably available if all of the following apply. It should be noted that there is some guidance in the NPPG[20] and the following criteria add to what the NPPG says.
  7. The site is available to be developed (including considering site ownership or whether the owners of sites have any intention of them being developed); and
    1. The site is within the agreed area of search; and
    2. The site is of comparable size in that it can accommodate the requirements of the proposed development; and
    3. The site is not safeguarded in the relevant Local Plan (including Minerals and Waste) or Neighbourhood Plan for another use; and
    4. It does not conflict with any other policies in the Local Plan.
    5. A site is not considered to be reasonably available if they fail to meet any of the above requirements or already have planning permission for a development that is likely to be implemented.
  8. The area of search should be guided by the requirement for the proposed development in a particular area and should be discussed with the Broads Authority at the pre-application stage.
  9. The Authority considers the following areas of search to be reasonable. It should be noted that there is some guidance in the NPPG[21] and the following criteria add to what the NPPG says.
    1. The rest of the particular district within the Broads Authority Executive Area
    2. Within the entire Parish (including the part that may be out of the Broads)
    3. Other settlements/parishes that are nearby (that may be out of the district)
    4. Or a wider/another area as appropriate and subject to agreement with the Broads Authority
    5. To prove that a development will provide wider sustainability benefits to the community that outweigh the flood risk, the Authority will use the most up to date Local Plan Sustainability Appraisal Objectives as well as guidance in the NPPG[22]. The current objectives are set out at Appendix 8.

    10. Exceptions test requirements

  10. The following will also be applied as part of the Exception Test:
    1. The development must not compromise future flood alleviation or flood defence schemes;
    2. The site-specific Flood Risk Assessment must demonstrate how resilience to flooding has been incorporated through a design which does not detract from the character and appearance of the locality;
    3. The site-specific Flood Risk Assessment must demonstrate how the development will be compatible with the nature of flooding in the Broads, considering climate change and sea level rise over the planned life of the development (see the section on climate change); and
    4. In the case of the replacement of a residential property, a residential development must be on a like-for-like basis, with no increase in the number of bedrooms, on the same sized footprint[23], potentially being relocated in a less vulnerable part of the site.

    11. Flood Defences

  11. Any required additional or enhanced flood defences should not conflict with the purposes and special qualities of the Broads.

Reasoned Justification

National Planning Practice Guidance (NPPG) states that ‘flood risk’ is a combination of the probability and the potential consequences of flooding from all sources – including from rivers and the sea, directly from rainfall on the ground surface and rising groundwater, overwhelmed sewers, and drainage systems, and from reservoirs, canals and lakes and other artificial sources.

Flood alleviation and preparing for the impact of climate change are key issues in the Broads, and a number of approaches could address this. It will also be essential to ensure that measures to minimise the risk of flooding from all sources of flood risk to new development do not themselves lead to development which, by virtue of its scale, layout, or design, is visually damaging to its surroundings. Therefore, even though the principle of development may be acceptable, acceptability in terms of design, landscape character, and impact on the environment must also be addressed.

All developments should be located in areas identified as being at the lowest risk of flooding.

Given the importance and relevance of flood risk issues to the Broads applicants should, in developing proposals, have regard to national flood risk guidance and policy, as set out in the NPPF and NPPG.

The Government also states in the NPPG that ‘Local authorities and developers should seek opportunities to reduce the overall level of flood risk in the area and beyond’. The policy seeks opportunities to reduce the overall level of flood risk.

Flood zones

Flood Zones refer to the probability of river and sea flooding, ignoring the presence of defences. They are shown on the Environment Agency’s Flood Map for Planning (Rivers and Sea)[24] and defined in the NPPG. They are also shown in a Strategic Flood Risk Assessment (see later text).

Flood Risk Advice

The Authority takes advice from the Environment Agency (EA) and Norfolk and Suffolk Lead Local Flood Authorities (LLFA) on flood related issues concerning development. The EA is responsible for flood defence and has permissive powers to carry out work to construct and improve flood defences.

Causes of Flooding in the Broads

The causes of flooding in the Broads are complex and flooding will continue to be a significant risk in much of the area into the foreseeable future. Developers should be aware of this situation. The risk of flooding must continue to be a material consideration in dealing with Broads’ planning applications and may be a reason for refusal of planning permission in some cases. In the uncertainty about the nature and extent of flood risk in the Broads, it is open to developers to commission their own risk assessment of the potential for flooding at a particular site. Risks relate not just to property but also to essential infrastructure and utilities required to support development, and to the emergency services’ ability to respond to an event. Inappropriate flooding can also harm the important habitats and species for which the Broads are important, which can have long term consequences for site maintenance and the achievement of conservation objectives.

Site-Specific Flood Risk Assessments

The EA says that ‘a Flood Risk Assessment (FRA) is required for all development:

  • within flood zones 2, 3 or 3b
  • within flood zone 1 with a site area of 1 hectare or more
  • within areas with critical drainage problems
  • within flood zone 1 where your LPA’s SFRA shows it will be at risk of flooding from rivers or the sea in future
  • that increases the vulnerability classification and is in flood zone 1 where your LPA’s SFRA shows it is at risk from other sources of flooding’.

The FRA should demonstrate how flood risk from all sources of flooding to the development itself, and flood risk to others, would be managed. It will also be expected to take climate change into account, identify flood reduction measures that will be incorporated into the development, including the use of Sustainable Drainage Systems, and provide an assessment of any residual risk. The FRA should be proportionate to the level of risk and the scale, nature and location of the development. The checklist set out in the NPPG[25] should be used to produce an FRA, but the FRA should also address the additional considerations set out in the policy.

To help the preparation of FRAs for householder development and other minor extensions in Flood Zones 2 and 3 the Broads Authority and Environment Agency have produced a Ticksheet template - see Appendix 7. This will assist applicants in producing a flood risk assessment for minor developments. It is in conformity with the NPPG FRA guidance and is designed to be user friendly for the applicant yet provide the information the BA needs to determine applications.

If you are carrying out an FRA for a development, you need to follow the Environment Agency’s standing advice[26] as follows:

Follow standing advice for vulnerable developments for developments (including change of use) in flood zone 2 and have a vulnerability classification of:

  • ‘more vulnerable’ (except for landfills, waste facility sites, caravan or camping sites)
  • ‘less vulnerable’ (except for waste treatment sites, mineral processing sites, water treatment plants and sewage treatment plants)
  • ‘water compatible’

Use the advice for minor extensions to complete an assessment for a minor extension in flood zone 2 or 3. A minor extension is a household or non-domestic extension with a floor space of no more than 250 square metres.

If your development is not covered by the standing advice:

Safe access and egress

Part (n) of the policy requires the FRA to demonstrate safe access and egress from the site. Where it has been demonstrated that this would not be possible due to unsafe flood depths on or surrounding the site, the safety of occupants will need to be managed through a Flood Response Plan (FRP) (also see Dry Island section below). The FRP should demonstrate that occupants will be kept safe and not exposed to flood hazards. This may be through evacuation in advance of a flood and/or remaining in situ within an appropriate refuge. The Authority has produced a Flood Response Plan template[27] for applicants. The acceptability of the plan and its ability to keep occupants safe will be assessed as part of the planning application.

Replacement Dwellings

Replacement dwellings in flood zone 3a are required to be on a like-for-like basis, as any increase in size is likely to expand into functional floodplain (flood zone 3b), thus putting more property and possibly more people at risk of flooding. The change to the functional floodplain could increase flood risk elsewhere.

Sequential and Exceptions Tests – general

In accordance with national policy, development in Environment Agency Flood Zones 2 and 3 will only be permitted when the Sequential Test and the Exception Test, where applicable, have been satisfied. The Sequential Test will be carried out by the Authority, drawing upon information submitted by the applicant.

Sequential test

Although the sequential test must be applied, due to the limited availability of sites in Flood Zone 1, the main objective, as applied to the Broads, is likely to be to reduce flood risk to new development through the application of the sequential approach and to maximise opportunities to build in resilience both at the site and buildings level through design. The improvement of safety and management of risk, including response to risk, must be addressed at the design stage.

The following sections elaborate on how various elements of the Sequential Test should be addressed. In applying the sequential test, the Authority will use the following:

A site is considered to be reasonably available if all of the following apply:

  1. The site is available to be developed (including considering site ownership or whether the owners of sites have any intention of them being developed); and
  2. The site is within the agreed area of search; and
  3. The site is of comparable size in that it can accommodate the requirements of the proposed development; and
  4. The site is not safeguarded in the relevant Local Plan (including Minerals and Waste) or Neighbourhood Plan for another use; and
  5. It does not conflict with any other policies in the Local Plan.

A site is not considered to be reasonably available if they fail to meet any of the above requirements or already have planning permission for a development that is likely to be implemented.

The area of search should be guided by the requirement for the proposed development in a particular area and should be discussed with the Broads Authority at the pre-application stage.

The Authority considers the following areas of search to be reasonable:

  1. The rest of the particular district within the Broads Authority Executive Area
  2. Within the entire Parish (including the part that may be out of the Broads)
  3. Other settlements/parishes that are nearby (that may be out of the district)
  4. Or a wider/another area as appropriate and subject to agreement with the Broads Authority

It is acknowledged that the area of search could be outside of the Broads Authority Executive Area and would require discussions with other Local Planning Authorities (and proposals would therefore need to comply with relevant planning policies of the relevant Local Planning Authorities). However, sites that are at less risk of flooding could be in the part of the settlement that is not in the Broads.

The Authority acknowledges that some schemes are site specific, such as the regeneration of a particular brownfield site or extension of a building, so it is impractical to change the location.

In all cases the developer must justify with evidence to the Broads Authority what area of search has been used when making the application.

If there are found to be other reasonably available sites at a lower risk of flooding, then the development has failed the Sequential Test, and this could lead to refusal of planning permission. Failing to pass the Sequential Test is sufficient grounds for refusal, as it would make the proposal contrary to the NPPF and Local Plan policies.

If, however, there are no other reasonably available sites, then the development has passed the Sequential Test. The Exception Test may also need to be undertaken at this point (if required).

Exceptions Test

Where an exception test is necessary, the applicant’s FRA must include sufficient information to enable this assessment to be undertaken. For the purposes of this policy, ‘footprint’ will be defined as the aggregate ground floor area of the existing on-site buildings, including outbuildings that affect the functionality of the floodplain, but excluding temporary buildings, open spaces with direct external access between wings of a building, and areas of hard standing.

The NPPF2023 at paragraph 170 says that for the Exception Test to be passed ‘it should be demonstrated that: a) the development would provide wider sustainability benefits to the community that outweigh the flood risk’. To assess this, the Authority will use the most up to date Local Plan Sustainability Appraisal Objectives. The current objectives are set out at Appendix 8.

The NPPF2023 at paragraph 170 goes on to say that for the Exception Test to be passed ‘b) the development will be safe for its lifetime taking account of the vulnerability of its users, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall’. The NPPG says:

  • Residential development can be assumed to have a lifetime of at least 100 years, unless there is specific justification for considering a different period.
  • The lifetime of a non-residential development depends on the characteristics of that development but a period of at least 75 years is likely to form a starting point for assessment.

In addition to these conditions, the following will also be applied as part of the Exception Test:

  • The development must not compromise future flood alleviation or flood defence schemes;
  • The Flood Risk Assessment must demonstrate how resilience to flooding has been incorporated through a design which does not detract from the character of the locality;
  • The site-specific Flood Risk Assessment must demonstrate how the development will be compatible with the nature of flooding in the Broads, considering climate change and sea level rise over the planned life of the development (see the section on climate change); and,
  • in the case of the replacement of a residential property, a residential development must be on a like-for-like basis, with no increase in the number of bedrooms, on the same sized footprint[28], potentially being relocated in a less vulnerable part of the site.

Climate change allowances

Climate change allowances can be found here: https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances. These will result in increases in flood level of between 1.2m and 1.6m compared to present day flood levels (this is a cumulative rise from 2000 to 2125).

Principles for development in flood zone 3

The approach in any particular case will depend on the nature of the land and the specific functionality of the floodplain, considering the presence of built structures and site infrastructure. The following principles will apply to development in flood zone 3.

In the case of a ‘greenfield’ site which has not been the subject of any previous development, the site could function as an unconstrained, open floodplain, subject to the presence of any ‘defences’. It may provide areas for water storage in times of flood and may have other value associated with this, for example as wet woodland.

Sites categorised as “brownfield sites which have been previously developed” will often cover sites larger than a single plot and may have been in use for a variety of uses, often employment based. These will often be characterised by areas of built development, including buildings and hardstanding, with undeveloped areas which might include vegetated margins or open areas. Parts of the site may function as functional floodplain and parts will not. The functionality of any part will depend on the way in which the water would behave in times of flood. If flood waters which inundate the site in a 1:20 (5%) annual probability event can pass under or through a building or sit on land this will be defined as functional floodplain. Where an existing building or structure acts as a barrier to flood water then its functionality is compromised, and it will not be classified as Flood Zone 3b and can be described as Flood Zone 3a.

When considering development proposals for brownfield sites which have been previously developed, the objective is to locate development in a sequentially appropriate manner on the site and to reduce risk through design. An initial site appraisal should identify the different flood risk zones on the site (where applicable) and differentiate between areas of Flood Zone 3a and Flood Zone 3b, as described above.

The objective when looking at development proposals on previously developed brownfield sites is to seek opportunities to restore the functionality of the floodplain. This must, however, be balanced against the need to maintain the land uses and development which support the economic and social viability of the Broads communities. So, the over- riding principle in respect of development is that it should not increase risk above the existing level.

Development should be located in a sequentially appropriate manner (which considers areas of lower flood risk first as discussed in this policy and supporting text) across any flood risk zones, in accordance with the NPPG. Where there is existing development within Flood Zone 3a or 3b, opportunities to improve flood risk should follow the following hierarchy:

  1. relocate development to Flood Zone 1 (subject to other sources of flooding as discussed previously)
  2. relocate development to a lower flood risk zone
  3. ensure there is no net increase in the development area within Flood Zone 3a.

Land uses or development which is of a higher level of vulnerability, as defined in the NPPG, than existing or previous uses on the site will only be permitted if it complies with table 3[29] of the NPPG and all the other policy requirements (such as safety and not increasing flood risk elsewhere).

Sites categorised as “brownfield sites which are currently developed” will often cover individual sites where replacement development is proposed. These will often be smaller plots and are owner occupied with limited (if any) opportunity for relocating development to an area of lesser flood risk, either on-site or elsewhere.

When considering proposals for replacement development, an initial appraisal should identify whether the development is in Flood Zone 3a or Flood Zone 3b.

If the site is in Flood Zone 3b, new water compatible development and essential infrastructure that has been subject to the Exception Test (as defined in the NPPG) will be permitted or a like-for-like replacement of an existing use. As detailed above, existing built development on site may prevent parts of the site from functioning as Flood Zone 3b, meaning it will be considered as Flood Zone 3a. In those cases, it may be acceptable to locate development appropriate to Flood Zone 3a within the extent of the previously developed footprint. This will be subject to the usual considerations in terms of safety of the development.

If the site is in Flood Zone 3a, new development for water compatible uses, less vulnerable uses or more vulnerable subject to the Exception Test (as defined in the NPPG) will be permitted or a like-for-like replacement of an existing use. In all cases the safety of the proposed development would need to be considered.

The objective when looking at development proposals on brownfield sites which are currently developed is to ensure that development does not increase flood risk to the site or the building or elsewhere above the existing level. Opportunities to reduce flood risk should also be considered.

The Authority may permit the relocation of existing development out of Flood Zone 3b to an undeveloped site with a lower probability of flooding where the vacated site is reinstated as naturally functioning floodplain, and where the benefits to flood risk outweigh the benefits of leaving the new site undeveloped. Such proposals will be considered against adopted planning policies.

Existing footprint of development in Flood Zone 3b and Permitted Development (PD)

Firstly, the following only applies to development within Flood Risk Zone 3b where ‘more vulnerable’ development is not considered appropriate, according to the NPPG.

For a replacement dwelling in Flood Zone 3b the existing footprint is currently defined in the footnote to policy PODM7 [30]. This does not make any reference to permitted development rights, only to existing buildings. The ‘like for like’ requirement of the policy is still valid as that is the starting point for the application – that the base position for any replacement dwelling in flood zone 3b is like for like. The Authority and Environment Agency consider that a scheme for a replacement dwelling may only include what is permitted through PD rights Class A enlargement, improvement, or other alteration of a dwelling house[31] as a pragmatic approach. The inclusion of these PD rights in the calculation of footprint is considered a reasonable approach to take, as it would avoid the need for applicants to first construct a rear extension only to include it in the calculations for a replacement dwelling. It is important to note however that there may be other considerations that might be relevant to decision making other than flood risk; for example, landscape character impacts.

If an application for a replacement dwelling is approved, the PD rights for extensions/outbuildings will be removed by the Authority to restrict further development within the functional floodplain. Householder PD rights would also be removed when permitting householder extensions within Flood Zone 3B, for the same reason; to restrict the further development within the functional floodplain.

Flood response plan template.

A site-specific Flood Response Plan will always be required for development in flood zone 3. The client/developer responsibilities for health and safety and facilities management may also require a site-specific flood response plan. These are important considerations on commercial sites and are potential requirements for compliance with the Construction (Design and Management) Regulations 2015[32].

They can form one means of managing residual risk where a development is found to be acceptable in flood risk terms and is a valuable document for owners and occupiers of all property at risk of flooding to have in place. The Authority has produced guidance and a suggested structure for these plans. The guidance and structure can be found at Appendix 6.

SUDS

Sustainable Drainage Systems (SuDS) are an alternative to traditional drainage systems that aim to reduce the total amount, flow, and rate of surface water run-off. There is a range of possible SuDs techniques that can be used, although not all techniques will be appropriate for individual development sites. Surface water run-off proposals should address the requirements of the Flood and Water Management Act 2010. See policy PODM8: Surface water run-off.

Dry Islands

Dry Islands are areas of a lower flood risk surrounded by areas of higher flood risk, such as flood zone 1 surrounded by flood zone 3. While development may be suitable in flood risk terms in the lower flood risk zone, in times of flood the area could effectively become an island. The issue here is about safe access and egress at times of flood. In the Broads, dry islands tend to occur in more isolated areas that may not experience development. However, there may be requirements for a Flood Response Plan to be produced for development in dry islands. When looking at the flood risk of a proposal, it will be important to assess the wider area as well as on the site.

Other consents that may also be required

Applicants should be aware that in accordance with the Environmental Permitting Regulations 2010 there is a need to obtain an Environmental Permit[33] from the Environment Agency for flood risk activities for work or structures in, under, over or within 16m from a main river and from any flood defence structure or culvert. The works may fall under one or more of the following categories: Exemption, Exclusion, Standard Rules Permit, Bespoke permit. Anyone carrying out these activities without a permit where one is required is breaking the law.

Section 23 of The Land Drainage Act 1991 requires applicants who wish to affect the flow of an ordinary watercourse, for instance to culvert, dam, weir or install a headwall into a watercourse, to obtain consent from the drainage board concerned.

Reservoir Flooding

The Authority will also consider issues relating to reservoir flooding, as per Government guidance: Reservoir flood maps: when and how to use them - GOV.UK (www.gov.uk)

Status of the 2020 Flood Risk Supplementary Planning Document on adoption of the Local Plan

The Broads Authority has a Flood Risk Supplementary Planning Document (SPD)[34] . The Government have indicated that they plan to stop SPDs being produced. They intend for Supplementary Plans to take their place. At the time of writing, this change had not been formally put in place. As such, the 2020 SPD remains in place. The review of the Local Plan as well as the potential for SPDs to not be relevant or not be produced any more, offer the opportunity to bring into the Local Plan relevant sections of the SPD. It is proposed that aspects of the SPD deemed not appropriate for this Local Plan become part of a new Flood Risk Guidance document that will be completed after the Local Plan is produced.

Strategic Flood Risk Assessment (SFRA)

SFRAs are important for the production of Local Plans. The Broads is covered by four separate SFRAs completed in 2017/2018[35] . However, a large area of the Broads Authority Executive Area has not been assessed as part of this work as the model needs to be purchased, updated, and run by the Environment Agency to produce SFRA equivalent information. It is intended that this will be completed as part of the Broadland Futures Initiative and there could therefore be adjustments to flood zone 3 as a result - see the Position Statement between the Broads Authority and Environment Agency[36] produced in July 2018 for more information. It is accepted that there is uncertainty about the precise boundaries of the functional flood plain (flood zone 3b) and the Environment Agency work should contribute to the understanding of this area. It is also accepted that due to natural processes and other activities, the functional flood plain can change over time. Where detailed modelling is not available, Indicative Flood Zone 3b has been used in the Norfolk part of the Broads. A similar approach has been used in the Waveney SFRA but on those maps, flood zones are 3b where modelled and 3 elsewhere. Due to the nature of flooding in the Broads, it is expected that Flood Zone 3a and Flood Zone 3b have similar extents so Indicative Flood Zone 3b/flood zone 3 is precautionary but reasonable. As set out in national policy, planning applications for schemes in flood zones 2 and 3 require site-specific flood risk assessments and these will determine the precise detail of flood risk on site.

Reasonable alternative options

No policy

Original policy

Sustainability appraisal summary

The following is a summary of the assessment of the policy and alternative(s).

A: Original policy: 5 positives. 0 negatives. 0 ? Overall, positive.

B: Amended policy: positives. 0 negatives. 0 ? Overall, positive.

C: No policy: 0 positives. 0 negatives. ?

How has the existing policy been used since adoption in May 2019?

According to recent Annual Monitoring Reports, the policy has been used and schemes have been permitted in accordance with the policy.

Why has the alternative option been discounted?

Flooding is a real issue in the Broads. The policy provides local detail and elaborates on national policy and so is favoured. The amended policy brings in parts of the Flood Risk SPD because SPDs may not be in place in the near future.

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Policy PODM8: Surface water run-off

  1. All development proposals will need to incorporate measures to attenuate surface water run-off in a manner appropriate to the Broads. This will need to reflect the characteristics of the site in accordance with a drainage hierarchy for rainwater so that, in order of priority, they:
    1. Continue natural discharge processes;
    2. Store water for later use;
    3. Adopt shallow infiltration techniques in areas of suitable porosity;
    4. Store water in open water features for gradual release to a watercourse;
    5. Store water in sealed water features for gradual release to a watercourse;
    6. Discharge direct to a watercourse;
    7. Discharge direct to a surface water drain (highways, Anglian Water or other body or within private ownership);
    8. Discharge direct to deep infiltration or borehole soakaways; or
    9. Discharge direct to a combined sewer
  2. The surface water runoff rate that will occur as a consequence of the development is required to be no more than the existing pre development greenfield runoff rate. Brownfield sites should aim to reduce runoff as close to greenfield rates as possible. The discharge rate for brownfield sites should be no more than the rate prior to any new development. Applicants are encouraged to seek betterment in surface water runoff as part of their proposals for brownfield sites. The runoff rate should be agreed with the Local Planning Authority, in conjunction with the Lead Local Flood Authority and where relevant, sewerage undertaker.
  3. Sustainable Drainage Systems (SuDS) shall be used unless, following adequate assessment, soil conditions and/or engineering feasibility dictate otherwise. These should be designed and implemented following the general principles set out at Appendix 9 as well as any relevant guidance or standards that are in place.
  4. Proposals to address surface water must be considered at an early stage of the scheme design process. The following criteria need to be addressed when designing measures to address surface water:
    1. Use a risk assessment on treatment stages to reflect the type of proposed development and how surface water run-off and drainage will affect the receptor. A 1.2m clearance between the base of infiltration SuDS and the peak seasonal groundwater levels is required;
    2. Take the current drainage arrangements of the area into account (including groundwater levels);
    3. Take natural site drainage and topography into account;
    4. Effectively manage water including maintenance of and, where possible improvement to water quality; and
    5. Provide amenity for local residents whilst ensuring a safe environment.
  5. Where SuDS via ground infiltration is feasible, to ensure that SuDS discharge water from the development at the same or lesser rate as prior to construction, developers must undertake groundwater monitoring within the winter period and winter percolation testing in accordance with the current procedure[37] .
  6. Minor developments that increase the footprint of an impermeable surface are required, where appropriate, to incorporate mitigation measures to reduce surface water runoff, manage surface water flood risk to the development itself and to others, maximise the use of permeable materials to increase infiltration capacity, incorporate on-site water storage, and make use of green roofs and green walls wherever reasonably practicable and appropriate, in accordance with design policies.
  7. Within the critical drainage catchments as identified by the Lead Local Flood Authority, and in other areas where the best available evidence indicates that a serious and exceptional risk of surface water flooding exists, all development proposals involving new buildings, extensions and additional areas of hard surfacing shall ensure that adequate and appropriate consideration has been given to mitigating surface water flood risk.
  8. Schemes that involve SuDS will be required to provide details of the management regime to ensure effective operation of the type of SuDS delivered in perpetuity.

Reasoned Justification

The policy seeks to ensure that surface water run-off is discharged as high up the following hierarchy (as set out in the NPPG) as possible:

  • into the ground (infiltration);
  • to a surface water body;
  • to a surface water sewer, highway drain, or another drainage system;
  • to a combined sewer.

Sustainable drainage systems (SuDS) slow the rate of surface water run-off and improve infiltration, by mimicking natural drainage in both rural and urban areas. This reduces the risk of flash flooding, which occurs when rainwater rapidly flows into the public sewerage and drainage systems. SuDS can also be used to enhance the environment of a site by contributing to green infrastructure and providing habitats for wildlife.

The Government has issued a written statement in relation to SuDS[38] saying that ‘we expect local planning policies and decisions on planning applications relating to major development (developments of 10 dwellings or more; or equivalent non-residential or mixed development) to ensure that sustainable drainage systems for the management of run-off are put in place, unless demonstrated to be inappropriate.’ The policy seeks to address this direction.

Watercourses in the Broads are regulated and maintained by the Internal Drainage Board or by private landowners. The IDB have their own local surface water policy which takes precedence over national best practice (Development - Water Management Alliance (wlma.org.uk)).

Potential to reduce phosphorous in surface water runoff

The Authority encourages using SuDS to reduce phosphorus in surface water runoff. Please see this guide.

Types of SuDS

The Broads is ideally suited for this sort of approach, as dykes and other forms of holding basins are characteristic of the landscape. The most effective form of water management is a naturally functioning floodplain and development proposals should aim to maximise opportunities to restore a naturally functioning floodplain where possible. A range of possible SUDs techniques can be used, although not all techniques will be appropriate for individual development sites. Examples of SuDS include retention ponds (a depression that holds water even during dry weather conditions), water butts, and swales (long vegetative depressions that are normally dry except during and after heavy rainfall).

Designing SuDS

An appropriate amount of land-take should be allowed to account for SuDS within any development. To be most effective, SuDS proposals need to be integrated into scheme designs at an early stage and not retrofitted once the layout has already been established.

Special consideration will need to be given to the design of the drainage system when there are known flooding issues within the immediate catchment of the development. Generally, known flooding issues correlate with areas shown as high-risk flooding on the Government Risk of Surface Water Flooding (RoSWF) maps, but the Lead Local Flood Authority (LLFA) will highlight any relevant information if consulted on a scheme. The Interactive PDFs produced as part of the SFRA work[39] (referred to previously) show areas that are subject to surface water flooding.

The scope of any drainage strategy should be proportionate to the scale of the development and the amount and type of flood risk the development site is subject to. As part of the strategy, it will be important to identify existing drainage arrangements to determine options for draining the site and the impact of the proposal post-development.

In some instances, it may not be appropriate to lessen significant amounts of water due to ecological considerations, but water quality issues should always be considered. A risk assessment should be undertaken, and appropriate treatment stages introduced if the receiving environment is assessed as being sensitive to development.

Normal infiltration SuDS should be no deeper than 2m below ground level, with a minimum of 1.2m clearance between the base of infiltration SuDS and the peak seasonal groundwater levels. Monitoring/ testing of groundwater must be undertaken in winter, as this tends to be the time of year that sees most precipitation and higher groundwater levels.

Advice from Norfolk County Council (one of the two LLFAs covering the Broads) is that deep infiltration or borehole soakaways should be one of the final options for consideration. While these methods can provide groundwater recharge via infiltration at depth, they do not mimic the natural drainage system as shallow infiltration does.

The Environment Agency would not normally support the use of deep bore soakaway systems, as these can present an unacceptable risk to the groundwater environment. Where applications are proposing their use, they should provide supporting documentation that clearly demonstrates why other SuDS discharge options are not appropriate. Each application for deep bore soakaways should also be supported by a detailed risk assessment demonstrating that their use will not impact on groundwater quality.  If deep bore soakaways are proposed, the developer may require an environmental permit from the Agency for a direct discharge to groundwater[40].  Granting of planning permission does not automatically mean a developer will be awarded an environmental permit, and early engagement with the Agency is recommended where deep bore soakaways are proposed.

Areas with concentrated surface water risk will be identified by the Lead Local Flood Authorities as Critical Drainage Catchments[41] (CDCs). The CDCs are the focus for partner engagement, detailed analysis and the potential implementation of flood protection schemes, as well as the production of Surface Water Management Plans[42] that look in detail at places that have suffered surface water flooding or have a high surface water flood risk. Currently, there are no CDCs in the Broads Authority area.

The following guidance will be useful when designing SuDS schemes:

Management, maintenance, and adoption of SuDS

Managing SuDS during the construction phase is important to make sure they are effective. Once constructed a management plan needs to be in place, along with appropriate resources, to ensure they continue to operate in perpetuity. Anglian Water’s standards for adopting SuDs may be viewed here: Sustainable surface water drainage (anglianwater.co.uk). SuDS can also be adopted by other bodies such as Management Companies.

Additional information

Various sources of technical information can be used when addressing surface water and designing SuDS:

Reasonable alternative options

No policy

Original policy

Sustainability appraisal summary

The following is a summary of the assessment of the policy and alternative(s).

A: Original policy: 7 positives. 0 negatives. 0 ? Overall, positive.

B: Amended policy: 7 positives. 0 negatives. 0 ? Overall, positive.

c: No policy: 0 positives. 0 negatives. 7 ?

How has the existing policy been used since adoption in May 2019?

According to recent Annual Monitoring Reports, the policy has been used and schemes have been permitted in accordance with the policy.

Why has the alternative option been discounted?

SuDS are an important component in tackling flood risk and so a policy is favoured. The amendment brings in design considerations to make sure that any SuDS are designed as well as possible.

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