Sequential Test Updates
The Sequential Test previously relied upon the Flood Zones as defined by the Flood Map for Planning, with a requirement to steer new development “to Flood Zone 1 (areas with a low probability of river or sea flooding).”. As the NPPF changed in July 2021 to incorporate all sources of flooding when assessing flood risk with a greater emphasis on the impacts of climate change, the PPG has now been updated to follow suit. The Sequential Test now seeks “to steer new development to areas with the lowest risk of flooding, taking all sources of flood risk and climate change into account”. The guidance goes on to clarify that “Where it is not possible to locate development in low-risk areas, the Sequential Test should go on to compare reasonably available sites:
- Within medium risk areas; and
- Then, only where there are no reasonably available sites in low and medium risk areas, within high-risk areas.”
Many Local Planning Authorities currently rely on the Flood Map for Planning to identify Sites in Flood Zones 2 and 3 to trigger the Sequential Test. This change in policy places a greater reliance on the Strategic Flood Risk Assessment, used to inform Local Plan policies, to identify Sites which are at risk of flooding in the future to trigger the Sequential Test.
As well as identifying a larger number of Sites, additional detail added to the PPG requires that the starting point for the application of the Sequential Test should assume no defence infrastructure, reflecting that many locations currently rely on the protection of flood defences which will be dependent on the long-term funding, maintenance and renewal of this infrastructure.
Following an assessment of the ‘undefended’ scenario, then the role of flood risk management infrastructure, such as defences, should be considered. This includes an assessment of the impact of exceedance and/or failure of the infrastructure as appropriate. An important clarification is that it will not be appropriate for planning purposes to consider the probability of failure of a flood defences due to the long-term uncertainties.
Where it is necessary to consider alternative sites, the PPG now clarifies that the absence of a 5-year housing land supply is not a relevant consideration for application of the Sequential Test for individual applications and that the site does not need to be within the clients ownership to be considered ‘reasonably available’.
The search area remains to be relevant to the catchment area of the proposed development, typically defined by the Local Planning Authority. However, clarification is provided that alternative sites could include a series of smaller sites and/or part of a larger development if these would be capable of accommodating the proposed development, which could have significant implications for development being brought forward in areas with ready supply of developable land.
When considering the availability of land within the district, the Local Planning Authority will hold information on sites identified through the housing and/or economic land availability assessments. However, it has now been clarified that sites currently available on the open market should also be considered.
Where it has been identified that there are ‘reasonably available’ sites in a lower risk area than the proposed development, development would be refused. However, if it can be demonstrated that, accounting for wider sustainable development objectives, application of relevant local and national policies, would provide a clear reason for refusing development in any alternative locations identified, then it is appropriate to move onto the Exception Test.
In the latest updates to the NPPF in July 2021, there were no changes to the wording of the Exception Test or its application. Once it has been demonstrated that the Sequential Test can be passed, it should then still be demonstrated that:
- development that has to be in a flood risk area will provide wider sustainability benefits to the community that outweigh flood risk; and
- 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.
Despite a move away from the EA’s Flood Zones within the Sequential Test in the PPG, the circumstances under which the Exception Test is applicable are defined by Table 2 of the PPG (previously Table 3) – which remains the same as before with only the subtle title change to ‘Flood risk vulnerability and flood zone ‘incompatibility’.
However, the updated PPG provides more in depth guidance on how both parts of the Test should be applied, which is stricter than the previous iteration (Link);
- The PPG still requires the development to demonstrate wider sustainability benefits to be provided for the first part of the test, otherwise planning permission should not be granted. It further clarifies that the impacts of flood risk on social, economic and environmental factors should be considered. One major change however that the PPG no longer states that “If a potential site allocation fails to score positively against the aims and objectives of the sustainability appraisal, or is not otherwise capable of demonstrating sustainability benefits, the local planning authority should consider whether the use of planning conditions and/or planning obligations could make it do so.”
- With respect to the second part of the Exception Test, stating that, where possible, flood risk should be reduced overall, the PPG has been updated to state “In order to demonstrate that the Exception Test has been satisfied without securing measures that would reduce flood risk overall, it will need to be demonstrated that such measures cannot be identified or are unfeasible.”
Design Flood Definition
Following the updates to the NPPF in July 2021, to acknowledge the risk of flooding from all sources including an emphasis on the impacts of climate change, the updates to the PPG include changes to the definition of the ‘design flood event’ which defines the magnitude event against which a proposed development is assessed within an FRA. The PPG now states;
“This is a flood event of a given annual flood probability, which is generally taken as:
- river flooding likely to occur with a 1% annual probability (a 1 in 100 chance each year); or
- tidal flooding with a 0.5% annual probability (1 in 200 chance each year); or
- surface water flooding likely to occur with a 1% annual probability (a 1 in 100 chance each year),
plus an appropriate allowance for climate change.”
Previously, the definition of the design flood did not include an appropriate allowance for climate change. Furthermore, the introduction of surface water to the definition of the design flood event enforces the requirement to assess the impacts of such an event including an allowance for climate change. This information is available through Surface Water Management Plans or Strategic Flood Risk Assessments for certain areas of England, but currently there is no national assessment of the impacts of climate change on surface water flood risk. For Sites identified to be at a ‘medium’ risk of flooding by the Environment Agency ‘Flood Risk from Surface Water’ mapping it may be necessary to undertake numerical flood modelling to quantify the risk of flooding with climate change.
Functional Floodplain Definition
The definition of the functional floodplain is now regarded as the 3.3% AEP, or 1 in 30 year event. Previously this was defined as the 5% AEP or the 1 in 20 year event. This has major implications for proposed developments that are near watercourses or that might otherwise be defined as functional floodplain.
Despite a move to include surface water in the definition of the design flood event, the definition of the functional floodplain remains to be relevant to flood risk from rivers or the sea.
In addition, the definition no longer recognises areas which are prevented by flooding from solid buildings from being outside of the functional floodplain, although it does assume flood management infrastructure is operating as intended.
With no clear national mapping of the 1 in 30 event, this could be problematic for developers to understand the implications. In short, it is likely that we will need to consult with the EA and LLFAs to understand the new allocation and to make sure that we offer comprehensive advice to clients. It is interesting and important to note that the guidance states that “the identification of the functional floodplain should take account of local circumstances and not be defined solely on rigid probability parameters”. So while the 1 in 30 is an approximation, local knowledge and information will still need to be taken into account.
Lifetime of Development
With the definition of the design flood now including a requirement to consider the impacts of climate change, the PPG has been updated to reinforce guidance on the period of time which a development should be considered for, referred to as the development lifetime.
The previous iteration of the PPG was much simpler, stating that residential development “should be considered for a minimum of 100 years, unless there is specific justification for considering a shorter period” and that the “lifetime of a non-residential development depends on the characteristics of that development” to be justified by the applicant and agreed by the LPA and EA. Whilst not specified in any guidance, industry best practice has generally been to apply a 60-year design lifetime to non-residential development, such as commercial, educational or industrial uses. The latest iteration of the guidance now adds to this stating that 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.
This change has the potential to affect development, particularly at tidal risk, where the EA’s guidance for assessing climate change is different for a 75-year and 100-year lifetime. Many flood models which assess tidal risk only include a 60-year and 100-year lifetime, and due to their publication dates, may only assess up to the years 2070 and 2100. For Sites located in areas affected by tidal flooding, it may be necessary to undertake further analysis to assess the impacts of this longer lifetime for non-residential uses, and even provide an up-to-date assessment for a full 100-year lifetime for residential uses.
Minor, Major and "Non-Major" Development Definitions
Both the NPPF and PPG refer to requirements for ‘major development’, defined in accordance with the definition set out in The Town and Country Planning (Development Management Procedure) (England) Order 2010. This is a standard planning definition used by the Local Planning Authority, and sits alongside the definition of ‘householder development’.
Development which sites between ‘householder’ and ‘major’ development is considered as ‘minor development’ from a planning perspective. However, this is not to be confused with ‘minor development (in terms of flood risk)’ which is referenced within both the NPPF and PPG. For ‘minor development (in terms of flood risk)’ there are certain exemptions, such as the Sequential and Exception Test. Furthermore, such development falls under the EA’s Flood Risk Standing Advice, and is the responsibility of the Local Authority to assess with respect to flood risk.
In the latest PPG, certain guidance is relevant to development which is not classified as ‘major development’ and to save confusion of covering the types of application which this includes, the guidance covers this with the introduction of the simpler term of ‘non-major development’.
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Changes of Use
With respect to a change of use, the previous PPG simply reiterated that a Flood Risk Assessment “may” need mitigation to ensure future users of the development will not be placed in danger from flood hazards throughout the lifetime of the development, and that it should be demonstrated that the objectives of the NPPF are met. The most recent iteration takes a more direct approach to identifying the issues relating to changes of use in relation to flood risk, rather than reiterating the NPPF. It acknowledges that such applications may increase the vulnerability by more than just by changing the use class but also by also “resulting in occupation or use by people who are more vulnerable than the previous occupants/users to risks from flooding” or “sub-division of a home into a series of flats may introduce more people or confine dwellings to the ground floor”.
Implementation of mitigation measures are encouraged to improve the flood resilience of an existing development, even where the vulnerability is not increasing, especially where older properties may not have been subject to a Flood Risk Assessment or appropriate mitigation, or where the severity/nature of flooding has changed over time (i.e. due to climate change). Consequently, this may result in increased requirements for Flood Risk Assessments to accompany change of use applications.
This iteration of the PPG adopts an updated hierarchical approach to flood risk within the guidance. The hierarchy states that (in order of preference) flood risk to development should be reduced through:
- Avoidance of flood risk in plan making, decision making and within sites through sequential allocation.
- Control of flood risk through engagement with flood risk management authorities
- Mitigation of flood risk through use of flood resistance and resilience measures
- Management of residual flood risk through management measures and flood warnings.
The PPG emphasises that such an approach should be considered early in the design process to iron out any conflicting design requirements. A new addition to the PPG is that it explicitly states that tensions between flood risk matters and planning matters do not justify unsafe development. Examples of this include;
- The impact of raised floor levels on access. For the former, there is a focus on ensuring that design is inclusive, and encourages innovative design to mitigate flood risk whilst not excluding certain sections of society, such as the elderly or those with less mobility.
- Where historic buildings are involved, guidance states that no flood resilience for historic properties is recommended alongside early consultation with Historic England.
- Structural safety of buildings should be considered, especially for flood depths greater than 600mm where the PPG recommends that a structural engineer is consulted.
The previous iteration of the PPG focussed on the off-site impacts of minor development. However, the latest version not only identifies that development in flood risk areas can result in a loss of floodplain storage, but also highlights the deflection or constriction of flood flow routes or through inadequate management of surface water (Link).
Flow routes that are deflected or constricted by development proposals, it will need to be demonstrated that such routes can be safely managed as part of the Flood Risk Assessment.
The PPG now specifies that where it is not possible to provide on-site level-per-level compensatory storage, it may be acceptable to provide storage off-site provided it is hydraulically and hydrologically linked.
It clarifies the concerns with respect to the use of voids below buildings, clarifying that this approach should “not normally be relied upon” for compensating for any loss in floodplain storage. Also, confirms that the loss of floodplain storage is “less likely to be a concern” in areas benefitting from appropriate flood risk management infrastructure or where the source of flood risk is solely tidal.
In addition to the above, a notable addition to the PPG is clarification of the approach where it is not possible to fully mitigate the impacts of development on flood risk elsewhere. The guidance requires that the “site-specific flood risk assessment will need to fully detail the extent and nature of the increase in risk and address its significance. This is likely to be a key consideration in whether planning permission is granted”. Whilst this does not provide a solution, it does identify that there may be circumstances where unavoidable impacts will be considered rather than immediately refused.
The PPG adds that a flood risk activity permit may also be required for activity (e.g. land raising) in the floodplain of a main river if it could affect flood flow or storage, and potential impacts are not controlled by a planning permission.
Safe Access and Egress
One of the largest changes to the PPG has been the focus on emergency response and safe access and egress from both new and existing development. The guidance acknowledges the challenges that may be presented to occupants/users who are less mobile or have physical impairment. It has always been a requirement to assess the availability of safe access/egress during design flood conditions, but the latest iteration of the guidance now also requires an assessment of the “ability of residents and users to….evacuate before an extreme flood (0.1% annual probability of flooding with allowance for climate change)”. Many flood modelling studies do not include an assessment of the impact of climate change during a 0.1% annual probability event (1 in 1000 chance each year).
The guidance identities that an increase in the number of people living or working in areas of flood risk could increase the scale of evacuation required during a flood event. A significant change in the PPG is the introduction of the concept of mitigating such impact on emergency response. The guidance suggests that either design considerations within the development, or off-site works could be proposed to reduce the consequence of flooding either locally or in the wider area respectively.
Paragraph 187 of the NPPF (July 2021) is referenced with regards to the applicant (or ‘agent of change’) being required to provide suitable mitigation before the completion of development for any significant adverse effect on existing businesses or community facilities in its vicinity (including change of use). The PPG states “where the impact cannot be wholly mitigated, developers need to cover the full cost of any additional emergency services provision needed”. Details on the cost implications of this are not provided, but it is likely the provision will be made through Community Infrastructure Levy or Section 106 contributions.
In addition to covering the full cost of any additional emergency services provision for impacts on existing businesses or community facilities, the PPG states that for new development “downstream of a reservoir”, the implications for reservoir safety and reservoir owners/operators should be considered (Link). Costs such as improving the design of the dam to reduce flood risk, operation of the reservoir, and general maintenance costs should be covered by the applicant as an ‘agent of change’ under Paragraph 187 of the NPPF. The application of this guidance is yet to be clarified, but it is likely the provision will be made through Community Infrastructure Levy or Section 106 contributions.
The PPG adds that the potential impacts of development on the operation of the reservoir should be considered, particularly where impacts could affect management of flood risk or the supply of water. The aforementioned costs are stated to be relating to development “downstream of a reservoir”, and appears to be a separate point, but it is unclear whether such impacts are also chargeable under the ‘agent of change’ clause.
Another major addition to the PPG is additional detail with respect to quantifying and mitigating ‘residual risks’ of flooding – it now has its own section!
The definition of residual risk has been extended from just the risk to a development once any site-specific flood mitigation measures are taken into account, to include the risk from flood risk management infrastructure.
Whilst the residual risks from flood risk management still include the following;
- a breach of a raised flood defence, blockage of a surface water conveyance system or failure of a pumped drainage system;
- failure of a reservoir; and
- a flood event that exceeds a flood management design standard, such as a flood that overtops a raised flood defence, or an intense rainfall event which the drainage system cannot accommodate.
The PPG now includes additional guidance on the likely presence of flood risk management infrastructure in the future. It should be considered whether flood risk infrastructure is likely to be improved to keep pace with climate change, e.g. is funding available and what are the funding options (e.g. Community Infrastructure Levy, planning obligations / S106 agreements, or Partnership Funding). This information is likely to come from the Local Planning Authority, in conjunction with Risk Management Authorities. For each circumstance, the PPG advises;
- “Where flood risk management infrastructure is likely to be improved to keep pace with climate change, the potential consequences of flooding resulting from breach or failure of that improved infrastructure is likely to be the main driver for mitigation.
- Where infrastructure is unlikely to be improved, the potential consequences of flooding resulting from overtopping or the design standard being exceeded will also be an important consideration. It is important to consider the consequences of both overtopping and breach, as the nature of flooding will be different in each case.”
Due to the potential for rapid onset of fast-flowing and deep flooding, with little to no warning of a failure, development should avoid internal flooding and ensure that people are not exposed to hazardous flooding. The latter applies irrespective of the development’s vulnerability classification. An emergency plan, or Flood Warning and Evacuation Plan, is likely to be fundamental in such circumstance to ensure users/occupants can be safe.
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