Strategic Flood Risk Assessment

The full Strategic Flood Risk Assessment report and Strategic Flood Risk Assessment Addendum created by Metis Consultants Ltd is available to download from our website.

6.4 Town Centres

There are 4 designated town centres located in Kingston. These include:

• Kingston Town Centre
• Surbiton
• New Maldon
• Tolworth

These town centres are part of the London Plan’s Town Centre Network due to their community sustaining role and the functions that they serve. Kingston Town Centre is categorised as a ‘metropolitan’ centre, whereas the other three are categorised as ‘district’ centres. Each of these town centres play an important role as they provide transport links, housing, shops, services and employment opportunities.

Kingston Town Centre is at high risk of flooding (refer to Web Maps for details) and is a vital metropolitan location within the Borough. Kingston Town Centre is an important centre for commerce, tourism and history within the Borough. It is considered an important area for development, however there is high flood risk within the area. Any development located within Kingston Town Centre must provide an FRA based on the requirements set out in this SFRA. Additional requirements are presented in Table 6‑1 relating to finished floor levels.

6.5 Planning Applicants

This section provides specific guidance on the key flood risk management requirements for planning applications. The guidance provides information to ensure that development proposals are compliant.

6.5.1 Application of the Sequential and Exception Tests

Implementation of a sequential, risk-based approach is vital in determining the suitability of a site for development with regards to flood risk. For proposed development sites that require the application of the Sequential Test, and in some instances, the Exception Test, this SFRA document and the accompanying web maps provide the basis for applying these tests at a site-specific level.

Proposed development sites within multiple flood risk zones are classed under the highest risk Flood Zone present on site. For example, a site that partly falls within Flood Zone 1 and Flood Zone 2 is formally classified as a site in Flood Zone 2. The Flood Zone that each proposed site falls under helps inform the approach needed for the site and the information required for the planning application. The Sequential Test will need to be applied to steer the entire proposed site to the areas with the lowest risk of flooding. If the Exception Test is required, the application is based on the highest Flood Zone the site is in and will need to be passed for the planning application.

Sequential Test

The Sequential Test ensures that a sequential approach is followed to steer new development to areas with the lowest probability of flooding. For sites that require it, but have not undergone Sequential Testing as part of the site allocations identified in Kingston’s Core Strategy / Local Plan, a site-specific Sequential Test is required. The search area and definition of reasonable available alternative sites must be determined in line with the guidance below, in consultation with the LPA. The scope should include, but is not limited to, the bullet points below. Any scope should be shared with the LPA for review and agreement prior to the Test being undertaken.

• Search area: The default area should be the entire borough. This can be reduced where justified by the functional requirements of the development or relevant objectives of the Core Strategy. Examples of these include:
  
  • Functional requirements – Industrial or infrastructure developments that may service an area wider than Kingston.
  • Core Strategy objectives – Regeneration of a specific area may be targeted based on objectives set in the Core Strategy.
• Reasonable available sites: These generally include sites that are suitable (those that can accommodate the requirements of the proposed development), developable and deliverable. Sources of where these could be selected from include the following:
  
  • List of sites prepared as part of the evidence base or background documents produced to inform the Core Strategy / Local Plan. At the time of writing, Kingston is undertaking an additional ‘call for sites’ that will inform their new Local Plan, set to be adopted in the winter of 2021 / 2022.
  • Sites listed under a Local Authority’s brownfield land register, which contains information on previously developed sites that are appropriate for residential development. This includes sites with and without planning permission.

Exception Test

Following the application of the Sequential Test, if it is determined that the proposed development cannot be in an area with a lower probability of flooding, the Exception Test should be applied. The Exception Test is designed to help ensure that flood risk to both people and property will be managed across the lifetime of the proposed development. To pass the Exception Test, the PPG sets out two considerations that need to be achieved. Both considerations will need to be satisfactorily demonstrated to the LPA for the development to be allocated or permitted. The considerations are:

• The development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared; and
• A site-specific FRA must demonstrate that 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.

To satisfy the Exception Test, evidence demonstrating the development proposal’s sustainability benefits should be provided. The evidence should demonstrate the wider sustainability benefits that the development would bring at that specific site. This may include evidence demonstrating how the proposed development meets the objectives set out in the Theme 1 (Sustainability) of the Core Strategy, or evidence demonstrating policy compliance regarding affordable housing or defined housing needs for the area. In addition, the planning and design of the development needs to demonstrate that the site will remain safe and operational during a flood event and that the development will not increase flood risk elsewhere. This may involve:

• Designing buildings to avoid flooding by, for example, raising floor levels.
• Implementing resilient and / or resistant features to reduce the impact of a flood. For example, resilient features, such as installing electrical equipment above flood levels, are designed to ensure the internal elements of a property can be recovered as quickly and as cost effectively as possible. Flood resistant features, such as installing flood doors and barriers, are designed to ensure water stays out of a property up to a given height.
• Utilising SuDS as a priority.
• Mitigating the potential impacts of flooding through design and applying a sequential approach within the development site (for example ensuring more vulnerable development lies in lower risk parts of a site) and flood resilient and resistant construction.
• Developing emergency evacuation procedures. Flood warnings and / or flood alerts, these areas are included in the web maps and need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development.
• Leaving space in developments for flood risk management infrastructure to be maintained and enhanced.
• Providing adequate flood risk management infrastructure which will be maintained for the lifetime of the development.
• Not increasing the size of the built footprint or through the appropriate flood compensation methods as set out in Table 6‑1.

Applicants must also consider safe access and egress of the development throughout its lifetime. The applicant should liaise with the LPA and EA for borough-specific safe access and egress guidance. In general, as per the PPG paragraph 039, an applicant should consider the following regarding safe access and egress:

“Access considerations should include the voluntary and free movement of people during a design flood, as well as the potential for evacuation before a more extreme flood. Access and egress must be designed to be functional for changing circumstances over the lifetime of the development.” 

The PPG Flood Risk Vulnerability and Flood Zone Compatibility table sets out some circumstances where the Exception Test will need to be applied following the Sequential Test.

Flood Risk Vulnerability Classification

Below shows the zones and when development is appropriate

Zone 1

• essential infrastructure
• highly vulnerable
• more vulnerable
• less vulnerable
• water compatible

Zone 2

• essential infrastructure
• highly vulnerable (exception test required)
• more vulnerable
• less vulnerable
• water compatible

Zone 3a

• essential infrastructure (exception test required)
• more vulnerable (exception test required)
• less vulnerable
• water compatible

Zone 3b

• essential infrastructure (exception test required)
• water compatible

Application Exceptions

Paragraph 164 of the 2019 NPPF highlights planning application exceptions to Sequential and Exception Tests. Minor developments and change of use development proposals that fall under one of the following criteria should not be subject to the Sequential and Exception Tests:

• Householder developments within the curtilage of the existing dwelling.
• Small non-residential extensions (with a footprint of less than 250m²).
• Change of use developments – except for changes of use to a caravan, camping or chalet site, or to a mobile home or park home site.

Development proposals that fall under one of these criteria should still meet the requirements for site-specific FRAs as set out in this SFRA, the NPPF and the accompanying PPG.

6.5.2 Site-Specific Flood Risk Assessment (FRA)

Site-specific FRAs should be proportionate to the degree of flood risk, making the best use of available information. They should also be appropriate to the scale, nature and location of the development. For further information, see the ‘Site-specific FRA’ key requirement section in Table 6‑1 and the EA’s guidance on FRAs for Planning Applications.

The site-specific FRA requires potential flood depths to be addressed as part of flood risk management and emergency planning measures where there is a probability of flooding from any flood risk source. Depending on the circumstances, certain mitigation measures will need to be employed to demonstrate that the potential impacts of flood depth will be adequately addressed. The most appropriate measure depends on a range of different factors including flood risk source, the potential impact of the flood risk, and the vulnerability classification of the development amongst others.

Where major and minor developments are proposed within the Flood Zone 3a (surface water) extent (based on the Surface Water Flood Risk Web Map), Kingston requires the applicant to submit a FRA. Change of use developments that fall within the Flood Zone 3a extent and have a bearing on a site’s existing drainage regime, such as a change of use development as part of a landscaping proposal, also require an FRA. Additionally, if a site is located within Kingston Town Centre, Kingston requires the applicant to submit an FRA.

For further guidance on the preparation and development of a site-specific FRA, the PPG has a checklist to provide guidance through the process. Details on the requirements of emergency planning can be found in Table 6‑1.

6.5.3 Drainage Strategy

As part of, or separate to, site-specific FRAs, information demonstrating how surface water runoff generated by the development site will be managed may need to be presented. As FRAs are not required for all developments, producing a separate Drainage Strategy may be advisable. A Drainage Strategy is a report that demonstrates how surface water could affect a site of interest and the surrounding areas post-development.

The statement should include the proposed SuDS features which are to be incorporated in the development (to improve the existing runoff conditions), along with details for their long-term management and maintenance. A statement is required for all major developments. This includes sites identified as being at risk of surface water flooding, and those that have a history of surface water flooding.

All minor developments and developments categorised as ‘change of use’ which modify existing surface water drainage will also require a Drainage Strategy. For example, if a minor development or development categorised as a ‘change of use’ proposes to amend the existing landscaping, a Drainage Strategy is required.

Taking the appropriate climate change allowance into account, the statement needs to demonstrate how water is expected to behave on a site, determine the site’s infiltration potential, runoff rates, and flow pathways, both before and after the proposed development is in place. Submitted information needs to also demonstrate that the proposed development will not increase flood risk to the surrounding sites.

A SuDS Proforma is required to be submitted with the drainage strategy. At the time of writing (May 2021) a drainage strategy is required to be submitted for all major applications.

Further details on the SuDS requirements and SuDS implementation to address the impact of future growth are contained in Table 6‑1 and Section 6.5.4 respectively.

6.5.4 Sustainable Drainage Systems (SuDS)

SuDS incorporate a range of measures and management techniques designed to manage surface water runoff. All new developments should incorporate SuDS in line with the Non-Statutory Technical Standards for Sustainable Drainage Systems and Policy DM 4 of the Core Strategy.  

SuDS measures should aim to achieve greenfield runoff rates, providing management and attenuation features that ensure surface water runoff is managed as close to the source as possible. Greenfield runoff conditions must be achieved for any greenfield sites. Development on brownfield sites should aim to achieve greenfield runoff rates where practical. Several policy and guidance documents provide information to assist with the implementation of SuDS. In addition to the London Plan, the LSDAP and CIRIA guidance documents The SuDS Manual and Guidance on the Construction of SuDS provide important information.

Applications need to outline the SuDS measures that the proposed development will include, and demonstrate how they will connect with any piped drainage system, if infiltration is not possible. The submitted evidence needs to demonstrate that the London Plan drainage hierarchy (in line with Policy SI 13 Sustainable drainage) has been followed. Surface water management features higher up the drainage hierarchy should preferably be incorporated:

1. rainwater use as a resource (for example rainwater harvesting, blue roofs for irrigation)
2. rainwater infiltration to ground at or close to source
3. rainwater attenuation in green infrastructure features for gradual release (for example green roofs, rain gardens)
4. rainwater discharge direct to a watercourse (unless not appropriate)
5. controlled rainwater discharge to a surface water sewer or drain
6. controlled rainwater discharge to a combined sewer

Where information is available, the Groundwater, Sewer and Artificial Flood Risk Web Map, indicate where infiltration-based SuDS may be potentially suitable for use, where uncertainties exist and where they are unlikely to be suitable. Where infiltration SuDS are potentially suitable or uncertain, the applicant must provide site-specific infiltration testing or borehole data to justify use of non-infiltration-based surface water management techniques within their Drainage Strategy.

Not all developments that require a planning application have a bearing on a site’s existing drainage regime, or have the potential to impact flood risk locally. This may include certain minor developments that do not increase the built footprint of a site, do not introduce new building structures, and / or do not alter associated landscaping. However, this needs to be demonstrated in line with Policy SI 13 of the London Plan and Policy DM 4 of the Core Strategy, which require developments to demonstrate that the surface water discharge rate from the site is at the greenfield runoff rate. If this is not achievable, proposals need to demonstrate a betterment of the existing rate.

Some cases may not present an opportunity to improve on-site water management. However, efforts should be made to improve the site’s drainage systems as the current regime may have wider flood risk implications for the area. For further information, contact the LLFA. Further details on SuDS is provided in Table 6‑1.

6.5.5 Flood storage compensation and mitigation

Buildings and structures, or the raising of ground levels within the floodplain can reduce the ability to store floodwater in times of flood. This can result in an increase in the risk of flooding, as floodwater is forced elsewhere. Any part of the development that could result in the loss of floodplain storage (buildings, land raising etc.) should provide a direct replacement of volume. Compensatory volume must be provided at the same level as the lost storage for it to be ‘level-for-level’ and ‘volume-for-volume’. An equal volume of flood plain must be created to that taken up by the development. This equal volume must apply at all levels between the lowest point and the design flood level (1 in 100 year plus an allowance for climate change).

Level for level flood plain compensation is the preferred method of mitigation because voids, stilts or undercroft parking tend to become blocked over time by debris or domestic effects leading to a gradual loss of the proposed mitigation. If it is not possible to provide level for level flood plain compensation, then other forms of mitigation may be considered if agreed with the Local Planning Authority (LPA). An FRA must demonstrate that level-for-level compensation has been considered, explain why it was not possible to provide it and detail how any associated risks from the chosen form of mitigation can be minimised (See Table 6‑1).

If voids are proposed as an alternative form of mitigation these will need to be floodable, with the underside of the void above the 1 in 100 year (1% annual probability) flood level with an appropriate allowance for climate change. The LPA must also be satisfied that they can enforce a condition to maintain the voids as designed and that an adequate maintenance plan is in place to ensure the voids remain open for the lifetime of the development.

If the LPA are not satisfied that alternative mitigation measures are appropriate, then the applicant should revise their development proposals to ensure that there will be no increase in built footprint on this site.

6.6 Local Planning Authority – Development Management

This sub-section provides Development Management specific guidance to ensure that the key requirements for individual planning applications can be effectively evaluated and assessed. Development should be considered at a strategic level, so it is important to identify how individual development proposals fit within a wider flood risk management strategy for a given area. The guidance accompanies the information presented in Table 6‑1 and Table 6‑2.

The 2011 SWMP and updated 2019 SWMP should be used to inform decision making on development within the borough. CDAs and defined sub-catchments (refer Section 2.4.5) provide examples of SuDS that may be appropriate to specific areas within the borough and can be used to determine the feasibility of proposed schemes.

6.6.1 Application of the Sequential and Exception Tests

Implementation of a sequential, risk-based approach is vital in determining the suitability of a site for development with regards to flood risk. Applicants need to provide evidence to demonstrate that the Sequential Test, and in some instances, the Exception Test has been applied for any proposed development site that requires them. It is then for the LPA to consider the extent to which the Sequential Test and Exception Test considerations have been satisfied, considering the circumstances in any given case. This SFRA document, and the web maps, provide the basis for applying these tests at a site-specific level.

Guidance on development in London, and the types of sites and locations to be considered, has seen a push towards certain considerations. The current London Plan (2021) identifies small site developments making an important contribution towards meeting housing objectives (Policy H2 ‘Small sites’). In addition, the need to adopt a sequential approach to guide development for main town centres is also of importance. This is in line with Policy SD7 ‘Town centres: development principles and Development Plan Documents’. These are important considerations for boroughs when considering new development proposals.

The PPG contains information on development compatibility within different Flood Zones. This table works in conjunction with the PPG Flood Risk Vulnerability Classifications table to provide guidance on the types of development that may be considered as suitable within Flood Zones.

Sequential Test

The Sequential Test ensures that a sequential approach is followed to steer new development to areas with the lowest probability of flooding. This means that certain development proposals should not be permitted in high and medium flood risk areas, where there are reasonably available sites appropriate for the proposed development in areas of lower flood risk. Within each Flood Zone, all sources of flooding need to be considered when applying this risk-based approach to the proposed development site.

For sites that have not undergone Sequential Testing as part of the development of the Local Plan (e.g. site allocations), but require it, applicants will need to complete a site-specific Sequential Test and provide evidence that the Test has been undertaken as part of the planning application. For information on the Sequential Test search area and definition of reasonable available sites, see Section 6.5.1.

Exception Test

Applicants may need to provide evidence that the Exception Test has been applied if the Sequential Test demonstrates that the proposed development cannot be in an area at lower flood risk. Through the Exception Test, the applicant needs to demonstrate that flood risk to people and property will be managed across the lifetime of the proposed development. Applicants should also ensure that climate change factors are taken into consideration over the development's lifetime. The PPG sets out two considerations that need to be achieved to pass the Exception Test. Both considerations need to be satisfactorily demonstrated by the applicant before development can be allocated or permitted. These considerations are:

• The development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared; and
• A site-specific FRA must demonstrate that 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 PPG Flood Risk Vulnerability and Flood Zone Compatibility table sets out some circumstances for Exception Test application following Sequential Testing. Evidence of Exception Testing may need to be applied for developments within areas subject to redevelopment or regeneration. For developments that are part of regeneration strategies, it is likely that they will provide the wider sustainability benefits required to pass that aspect of the Exception Test. All submitted planning applications still need to demonstrate that the development will be safe for its lifetime, will not increase flood risk elsewhere and, where possible, will reduce flood risk overall. For information on how the second consideration of the Exception Test could be achieved by the applicant, see Section 6.5.1.

6.6.2 Site-Specific Flood Risk Assessment (FRA)

Site-specific FRAs should demonstrate how flood risk will be managed now and in the future over the proposed development’s lifetime. The FRA needs to take climate change into account, and the vulnerability of land use classification of the development (Refer to Table 2 – Flood Risk Vulnerability of the PPG). An FRA should be provided with a planning application for developments in the following circumstances:

• All development proposals in Flood Zones 2 and 3, including minor development and change of use [Note minor developments include property sub-division (as this is ‘development’ defined by Section 55 of the Town and Country Planning Act 1990) and extensions that exceed the parameters of Permitted Development defined by Planning Portal Guidance].
• Proposals for development areas that are 1 hectare or greater in Flood Zone 1.
• New proposals, or a change of use in development type to a more vulnerable class, where the proposed development could be affected by sources of flooding other than rivers and the sea.
• Proposals within areas with critical drainage problems as designated by the EA [Note that this does not include Critical Drainage Areas as defined by the Kingston SWMP – there are currently no such areas defined by the EA within the borough at the time of publication of this SFRA in June 2021].
• All major and minor developments are proposed within the Flood Zone 3a (surface water) extent.
• All development proposals within Kingston Town Centre.

Development Management should refer this SFRA and the accompanying Web Maps to applicants, highlighting the key areas that could impact their proposals. For development proposals in areas at risk of fluvial flooding, there is a statutory requirement for LPAs to consult with the EA before planning permission is granted under the Town and Country Planning (Development Management Procedure) (England) Order 2015. For advice on when the EA should be consulted, and guidance for where fluvial flood risk is an issue, the EA has developed Standing Advice. In addition, the PPG has a checklist which can aid in the process of reviewing a site-specific FRA.

6.6.3 Drainage Strategy

Applicants may need to demonstrate how surface water runoff generated by the development site will be managed. This may be demonstrated through a Drainage Strategy, a report that should demonstrate how surface water could affect a site of interest and the surrounding areas. A strategy is required for all major developments not categorised as ‘change of use’. All minor developments and developments categorised as ‘change of use’ which modify existing surface water drainage will also require a Drainage Strategy.

All major development proposals that have been identified as requiring a Drainage Strategy need to provide a completed Kingston SuDS Proforma. The Proforma has been divided into four sections which require applicants to demonstrate the following:

• Site and project information – Details of the proposed development, existing site and drainage system.
• Proposed discharge arrangement – Details regarding the infiltration feasibility for potential infiltration and the proposed surface water discharge method. The drainage hierarchy, which must be referred to, presented in the Sustainable Drainage Proforma is currently based on Policy SI 13 of the current London Plan and Policy 5.13 of the 2016 London Plan.
• Drainage Strategy – Details of the greenfield, brownfield (where relevant) and proposed discharge rates. Information regarding the proposed SuDS measures, along with their proposed catchment areas and storage capacities are also required.
• Supporting information – Details regarding the evidence and supporting information for the information provided in the Proforma, including proposed maintenance approaches.

DEFRA published the Non-Statutory Technical Standards for Sustainable Drainage Systems in March 2015. The document’s Standards, which an application should refer to, include:

• Flood risk outside the development
• Peak flow control
• Volume control
• Flood risk within the development
• Structural integrity
• Construction
• Designing for maintenance considerations

6.6.4 Sustainable Drainage Systems (SuDS)

These Standards should be used for the assessment of the Drainage Strategy and the accompanying SuDS Proforma submitted with planning applications.

SuDS incorporate a range of measures and management techniques designed to manage surface water runoff. They should mimic natural drainage approaches as closely as possible, providing an alternative to ‘hard engineered’ traditional drainage. SuDS provide opportunities to:

• Reduce the causes and impacts of flooding, providing opportunities to reduce the overall local flood risk through limiting surface water runoff rates and, where possible, volumes.
• Minimise pollution from urban runoff at source.
• Enable groundwater recharge where infiltration is possible.
• Combine water management with green space, providing environmental, amenity and recreational benefits.

Core Strategy Policy DM 4 (Water Management and Flood Risk) is a key policy for flood risk and water resource management. The policy requires applicants to follow the Mayor of London’s drainage hierarchy. The purpose of the drainage hierarchy is to ensure that reasonable measures are taken to sustainably manage and reduce the amount of rainfall being discharged from a development site. Applicants should take measures to ensure that surface water management features higher up the drainage hierarchy are incorporated. Where measures higher up the hierarchy have not been proposed, justification should be provided to demonstrate why it is not possible to implement certain features.

Policy SI13 (Sustainable drainage) of the current London Plan (2021) uses an updated drainage hierarchy which highlights the policy’s objective of prioritising green surface water management features over grey ones:

1. rainwater use as a resource (for example rainwater harvesting, blue roofs for irrigation)
2. rainwater infiltration to ground at or close to source
3. rainwater attenuation in green infrastructure features for gradual release (for example green roofs, rain gardens)
4. rainwater discharge direct to a watercourse (unless not appropriate)
5. controlled rainwater discharge to a surface water sewer or drain
6. controlled rainwater discharge to a combined sewer

Applicants should aim to reduce surface water discharge in line with the current Sustainable Drainage Hierarchy as set out in Policy SI 13. Measures should also be taken to prioritise green surface water management features over grey ones.

Applicants should aim to achieve greenfield runoff rates via their proposed SuDS measures and ensure that surface water runoff is managed as close to the source as possible. The proposed measures should be incorporated in line with the Non-Statutory Technical Standards for Sustainable Drainage Systems.

In April 2015, LLFAs became statutory consultees on major planning applications with surface water drainage implications. The associated Written Ministerial Statement HCWS161, alongside the London Plan, demonstrates the importance of applicants incorporating SuDS into their development proposals. This means that LPAs are required to consult LLFAs for expertise and technical advice on the management of surface water before reaching a decision on major planning applications under the Town and Country Planning (Development Management Procedure) (England) Order 2015.

The issues that are analysed by LLFAs and LPAs for planning applications are referred to as ‘material planning considerations’, issues that are relevant to the decision-making process. As stated in the Written Ministerial Statement HCWS161, SuDS are a material planning consideration for all major applications, and decisions on all planning applications require evidence that SuDS are implemented to ensure surface water is managed safely and sustainably on site. Further information on material planning considerations, planning applications and the decision making process can be found on the Determining a Planning Application guidance page.

6.7 Planning Policy

6.7.1 Application of the Sequential and Exception Tests

The NPPF highlights the need for a sequential, risk-based approach to be considered for development. This approach aims to keep development out of Flood Zones 2 and 3, and areas at risk from other sources of flooding, where possible. Implementation of this approach requires proposed development sites to be reviewed through the application of the Sequential Test, and in some instances, the Exception Test. This SFRA document, and the Web Maps, provide the basis for applying these tests, at the site-specific level.

Strategic application of the Tests for allocated sites, if required, are generally completed as part of the Local Plan development process by LPA officers (in consultation with the EA). This process should be informed by the initial screening assessment completed for current allocated sites. Recommendations for completing Level 2 SFRAs are made in Section 8 where further flood risk information and assessment may be required to inform the Tests. Guidance is provided in the following sections for application of the Tests at the Local Plan / strategic scale.

Sequential Test

The Sequential Test ensures that a sequential approach is followed to steer new development to areas with the lowest probability of flooding. This document provides the evidence base for the Sequential Test to be applied at a borough-wide or local level in preparation for a borough’s Local Plan and associated allocated sites, depending on where the site is located.

If the application of the Sequential Test demonstrates that development can be allocated in Flood Zone 1, the applicant will have passed the Sequential Test once the proposed development has been moved to a site in Flood Zone 1. However, some areas at lower flood risk may not be suitable for development due to various other reasons. In these instances, the Sequential Test should be applied to guide the development to the lowest risk area appropriate for the development type. This increases the possibility of facilitating development which is at the lowest risk of flooding in line with the relevant vulnerability of land use classification. The PPG flowchart demonstrating the ‘Application of the Sequential Test for Local Plan Preparation’ provides guidance.

The following process is recommended for the LPA to complete the Sequential Test for site allocations during Local Plan development based on the PPG’s development vulnerability classification:

1. Complete a screening assessment of all sites to identify flood risk sources and how they might be impacted by climate change. The Web Maps should be used to identify flooding from all sources as detailed in Section 5. The potential impacts of climate change for each assessed flood risk source is also provided. Risk assessment specific guidance for the application of climate change is provided in Section 4.
2. Assess how long it is anticipated each development will be present for (the ‘design life’). A design life of 100 years for residential development and 60 years for non-residential development is recommended if no other information is available.
3. Any ‘Highly Vulnerable’ developments should be located within Flood Zone 1. If this is not possible due to a lack of suitable sites, then locations in Flood Zone 2 can be considered where the Exception Test can be passed. If no suitable sites exist in Flood Zones 1 or 2, then further opportunities for development locations should be sought (this could be within or outside the borough)
4. A similar process can then be applied to ‘More Vulnerable’ developments with priority given to locations within Flood Zones 1 and 2. If there are no suitable sites, then Flood Zone 3a can be considered where the Exception Test can be passed.
5. ‘Less Vulnerable’ developments can then be located within remaining sites in Flood Zones 1, 2 and 3a (in that order of preference). This development classification is not appropriate for Flood Zone 3b.
6. ‘Essential Infrastructure’ should also be preferentially located in the lowest risk Flood Zone available for the type of infrastructure. This development can be in Flood Zone 3a or 3b after passing the Exception Test.
7. ‘Water Compatible’ development should be allocated last as they generally have the fewest constraints with regards to flood risk.

Where proposed site allocations are at a risk of flooding from one or more sources, Level 2 SFRA recommendations are made in Section 8 for specific allocated sites. The Level 2 SFRA can provide site-specific flood risk management recommendations and an assessment of whether the site could pass the Exception Test on this basis.

Exception Test

The Exception Test should be applied after the Sequential Test if it has been determined that a proposed development cannot be located in an area with a lower flood risk. To pass the Exception Test and ensure that flood risk to both people and property is effectively managed across the proposed development’s lifetime, the PPG sets out two considerations that need to be achieved. These considerations are:

• The development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared; and
• A site-specific FRA must demonstrate that 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 PPG’s ‘Application of the Exception Test for Local Plan Preparation’ flowchart provides guidance on applying the Exception Test for Local Plans. The flowchart highlights that following the borough-wide level Sequential Test, the Exception Test will need to be applied if certain development sites are not in an appropriate location. Guidance for what is deemed an appropriate location is based on NPPF flood risk policy as highlighted in Section 2.2.1. A Level 2 SFRA may also be used to assess allocated sites in more detail to determine if the Exception Test can be passed. Recommendations for Level 2 SFRAs assessments are made in Section 8.

6.8 Emergency Planning

Under the Civil Contingencies Act 2004, Kingston is designated as a Category 1 Responder. They are required to assess risks and respond appropriately in case of an emergency. This includes responding to a major flooding event. Kingston’s responsibilities under the Act are:

1. from time to time assess the risk of an emergency occurring;
2. from time to time assess the risk of an emergency making it necessary or expedient for the person or body to perform any of his or its functions;
3. maintain plans for the purpose of ensuring, so far as is reasonably practicable, that if an emergency occurs the person or body is able to continue to perform his or its functions;
4. maintain plans for the purpose of ensuring that if an emergency occurs or is likely to occur the person or body is able to perform his or its functions so far as necessary or desirable for the purpose of:
   
   1. preventing the emergency,
   2. reducing, controlling or mitigating its effects, or
   3. taking other action in connection with it

Section 5 of this SFRA and the accompanying Web Maps should be used to help Kingston’s Emergency Planning Unit to help inform response requirements in line with the Civil Contingencies Act 2004. Emergency planning can use the information to tailor needs to be area and risk specific.