Flood Risk Assessment for Essential Infrastructure

What counts as essential infrastructure?

Essential infrastructure is defined in table 2 of Annex F to the NPPF. In the version published on 17 August 2026 it comprises:

• “Essential transport infrastructure (including mass evacuation routes) which has to cross the area at risk.”
• “Essential utility infrastructure which has to be located in a flood risk area for operational reasons, including for electricity generation and storage, electricity network infrastructure, telecommunications infrastructure, water supply reservoirs and water treatment works that need to remain operational in times of flood.”
• Wind turbines.
• Solar farms.
• Hydrogen production facilities.
• Carbon capture, distribution and storage facilities.
• Heat networks.
• Data centres.
• Electric vehicle charging stations.

Two points about this list matter in practice. First, the location qualifiers apply only to the transport item (“has to cross the area at risk”) and the utility item (“has to be located in a flood risk area for operational reasons”), not to the named types. On the face of table 2, a data centre or solar farm is essential infrastructure without needing to show an operational reason for its location. Second, the words “substation”, “battery” and “power station” do not appear anywhere in Annex F. Substations and battery energy storage fall within the utility item, as “electricity network infrastructure” and “electricity generation and storage”. That item is defined by the NPPF itself as infrastructure “which has to be located in a flood risk area for operational reasons”, the same wording as the previous Annex 3, so the FRA should explain why the asset needs its location. For electrical infrastructure this is usually the grid connection point.

Hazardous substances. Installations that need hazardous substances consent, or that fall under the Control of Major Accident Hazards (COMAH) Regulations 2015, are highly vulnerable. But where there is a demonstrable need for such installations, “including bulk storage associated with port or similar facilities, and energy infrastructure and carbon capture or storage”, to be at coastal, water-side or other high flood risk areas, Annex F says they should be classified as essential infrastructure.

Mixed schemes. Where a scheme has elements in different vulnerability classes, “the highest vulnerability category should be used, unless the development is considered in its component parts” (notes to Annex F, table 3). In our experience, a data centre campus with offices, or a solar farm with a battery compound, can often be assessed component by component.

How is each type of infrastructure classified?

This table brings together the classification of the infrastructure we are most often asked about, in England, Wales and Scotland.

How infrastructure is classified in England, Wales and Scotland (Aegaea summary of NPPF Annex F table 2, TAN15 Figure 4 and the NPF4 glossary)

Essential utility infrastructure is defined in Annex F, table 2 as infrastructure “which has to be located in a flood risk area for operational reasons”.

Can essential infrastructure be built in a flood zone?

Yes, in any flood zone in England, provided the policy tests are met. Under Annex F, table 3 of the NPPF (August 2026), essential infrastructure is compatible with Flood Zones 1 and 2 without the exception test, and needs the exception test in Flood Zones 3a and 3b.

Essential infrastructure by flood zone (NPPF Annex F, table 3 and notes; PPG table 2)

Planning Practice Guidance table 2 (paragraph 079, revised August 2022) shows the same result for essential infrastructure: no exception test in Zones 1 and 2, and the exception test required in Zones 3a and 3b. Its notes add that the table “does not show the application of the Sequential Test which should be applied first”.

Annex F’s specific wording on floodplain storage and flows applies in Flood Zone 3b only. In Flood Zone 3a, essential infrastructure must still pass all three parts of the exception test, including not increasing flood risk elsewhere, and meet Policy F7, so lost floodplain storage usually still has to be compensated.

Flood zones in England cover river and sea flooding only. Surface water, groundwater and other sources do not change the table 3 answer, but they still count for the sequential test (Policy F5) and for safety (Policy F7).

Does essential infrastructure need the sequential test?

Usually, yes. Policy F5 of the NPPF has no exemption for essential infrastructure. The sequential test applies in areas at current or future risk of flooding from any source, unless one of the general exemptions in F5(2) applies, for example where the flood risk assessment shows that no built development, including access, will be in an area at risk.

Each scheme is different. Where a substation, battery compound or similar plant is added to an existing solar farm or energy site, it may fall within the exemption for small non-residential extensions with a footprint of less than 250 m² (F5(2)(c)(ii)), and Planning Practice Guidance asks for a pragmatic approach to “comparatively small extensions to existing premises” (paragraph 027a). A standalone substation on a new site is more likely to need its own sequential test. For infrastructure of regional or national importance, the area of search may reasonably extend beyond the local planning authority boundary (paragraph 027a).

Where the sequential test is not required, the exception test is not required either (Policy F6(2)(a)).

How do you pass the exception test for essential infrastructure?

Under Policy F6(1)(b) of the NPPF (August 2026), the exception test has three parts, and all must be met. The table shows what each part asks, and the evidence that usually satisfies it for an infrastructure scheme:

Exception test evidence for infrastructure schemes (NPPF Policy F6(1)(b); typical evidence is Aegaea practice)

Climate change. The Environment Agency’s guidance, Flood risk assessments: climate change allowances (last updated 27 May 2022; checked 19 October 2026), says essential infrastructure in Flood Zones 2, 3a and 3b should use the higher central peak river flow allowance, and the upper end allowance where a credible maximum scenario is appropriate. For sea level rise, flood risk assessments should assess both the higher central and upper end allowances. The guidance predates the August 2026 NPPF, which added data centres and EV charging to essential infrastructure, so we agree the allowances with the council and the Environment Agency at scoping.

Data centres and flood risk

Data centres are listed as essential infrastructure in Annex F, table 2 of the NPPF published on 17 August 2026. In England a data centre is therefore compatible with Flood Zones 1 and 2 without the exception test, and can be considered in Flood Zones 3a and 3b subject to it. Because the policies became material considerations on the day of publication (Annex A, paragraph 1) and Annex A has no transitional arrangement for applications, applications still undetermined on 17 August 2026 should now be assessed against the new classification.

In our experience, the flood risk work for a data centre is unusually demanding, for two reasons. The asset must keep running through a flood, so electrical plant, cooling, fuel and access all need to be designed around the flood level, not just the building floor. And data centres are large, so the footprint, land raising and drainage can affect flood risk elsewhere, which is the third part of the exception test.

Substations, battery storage, solar and charging hubs

Substations, battery energy storage systems (BESS), solar farms and electric vehicle charging stations need a flood risk assessment where Policy F4(1) or F4(2) applies, and it should be “appropriate to the scale, nature, and location of development” (F4(3)).

• Substations and BESS are not named in Annex F, but fall within its essential utility infrastructure wording, “electricity network infrastructure” and “electricity generation and storage”. As essential infrastructure, they need the exception test in Flood Zones 3a and 3b, and in Flood Zone 3a they should be designed and constructed to remain operational and safe in times of flood (Annex F, table 3; PPG table 2).
• Solar farms are named as essential infrastructure. A battery compound within a solar scheme can be assessed as a separate component.
• EV charging stations are named as essential infrastructure. Where a charging hub is assessed in component parts, the parking and circulation areas are less vulnerable, and less vulnerable development should be refused in Flood Zone 3b, so in 3b the layout matters.

For electrical infrastructure the key design questions are usually the flood level to which equipment must be raised or protected, and how the site is reached during a flood.

Aegaea has produced flood risk assessments for substation and switch-room projects, and supports infrastructure clients from site selection through to discharge of planning conditions.

What changed for essential infrastructure in August 2026?

The NPPF published on 17 August 2026 moved the vulnerability classification from the old Annex 3 into Annex F, table 2, and changed the essential infrastructure list.

• Newly named: hydrogen production facilities; carbon capture, distribution and storage facilities; heat networks; data centres; and electric vehicle charging stations.
• Already listed before: wind turbines and solar farms were essential infrastructure under the previous Annex 3.
• Reworded utility item: the old item covered “electricity supply including generation, storage and distribution systems” and named power stations and grid and primary substations. The new item drops those named assets, refers to “electricity generation and storage, electricity network infrastructure”, and adds telecommunications infrastructure and water supply reservoirs. Battery storage was therefore already within the old wording.
• Unchanged: utility and transport infrastructure is essential infrastructure only where it has to be in a flood risk area for operational reasons, or has to cross the area at risk.

Planning Practice Guidance and the Environment Agency’s flood risk standing advice still refer to the old Annex 3. Our sequential and exception tests guide explains what has and has not been updated.

What does an essential infrastructure FRA include?

An Aegaea flood risk assessment for essential infrastructure typically covers:

• the vulnerability classification under Annex F, with reasoning where it is not obvious, such as BESS or substations;
• flood risk from all sources, including rivers, sea, surface water, groundwater, sewers and reservoirs, now and with climate change;
• design flood levels for equipment, plant and access, and the resilience measures needed to remain operational;
• the sequential test position and, where required, evidence for all three parts of the exception test;
• floodplain storage and flow effects, with hydraulic modelling where needed;
• a surface water drainage strategy meeting Policy F8 and the National Standards for Sustainable Drainage Systems;
• an emergency plan, often a Flood Warning and Evacuation Plan (FWEP), for staff and visitors.

Essential infrastructure in Wales and Scotland

Wales. TAN15’s vulnerability table (Figure 4) has no essential infrastructure category. It uses three classes, and how an energy scheme is classified decides which rules apply:

• Less vulnerable: “Transport and utilities infrastructure” and “Renewable energy generation facilities (excluding hydro generation)”. Hydro generation is water compatible.
• Highly vulnerable: “Especially vulnerable industrial development (e.g. power generating and distribution elements of power stations, transformers, chemical plants, incinerators)”.
• Not named: battery storage, data centres, telecoms, and water and sewage treatment. Decision makers apply professional judgement (para 9.5), and in larger or mixed schemes some parts can be treated as highly vulnerable and others as less vulnerable (para 9.6).

How paragraphs 10.22 and 10.23 fit together in Zone 3. Paragraph 10.22 says no new highly vulnerable development on greenfield land should be permitted in Zone 3 “regardless of the conclusion of any Flood Consequences Assessments”. Paragraph 10.23 then deals with “Other proposals”, and it is there that proposals for national or energy security, climate change mitigation or public health “may also, by exception, be appropriate provided that their locational need is clear and the potential consequences from flooding have been considered and found to be acceptable”. Read together:

• the energy-security exception in 10.23 applies to proposals that 10.22 does not cover: less vulnerable development, and redevelopment of previously developed land;
• it does not reopen 10.22, so a transformer, substation or generating plant classed as highly vulnerable on greenfield land in Zone 3 is not made acceptable by an energy-security case;
• a solar or wind scheme’s generating arrays (less vulnerable) on greenfield land in Zone 3 can use the 10.23 route, but any transformers or substation classed as highly vulnerable should sit outside Zone 3, because a site in two or more zones is assessed land use by land use against each zone (para 15.5);
• whatever is permitted must meet the section 11 thresholds for its category: flood-free in the 1% river and 0.5% sea events plus climate change (para 11.7 and Figure 5), and in the 0.1% event no more than 600 mm depth with 0.15 m/s for highly vulnerable or 0.3 m/s for less vulnerable development (Figure 6).

The same split applies at plan level: allocations for highly vulnerable new development must not be made in Zone 3, while less vulnerable allocations need exceptional circumstances, such as energy security, with a clear locational need (para 10.20). Paragraph 10.22 also requires Welsh Ministers to be notified of any highly vulnerable greenfield proposal in Zone 3 that a council intends to approve. Because the classification of substations and transformers turns on professional judgement, we agree it with the council and NRW at pre-application. See our Flood Consequences Assessments in Wales page.

Scotland. National Planning Framework 4 (NPF4) Policy 22(a) supports development in a flood risk area only in four cases, the first being “essential infrastructure where the location is required for operational reasons”. NPF4’s glossary defines essential infrastructure to include digital and telecommunications infrastructure, renewable, low-carbon and zero-emission technologies for electricity generation, distribution and transmission grid networks and primary substations, water and waste water infrastructure, and transport identified in the local development plan.

Why Aegaea

• Chartered sign-off. Every report is reviewed and signed off by a Chartered member of CIWEM.
• Modelling in-house. TUFLOW, Flood Modeller, HEC-RAS and InfoWorks ICM, so the third part of the exception test can be evidenced, not asserted.
• Early input. We work from site selection, when moving plant or access out of the floodplain is cheapest.
• Three nations. We work to the NPPF in England, TAN15 in Wales and NPF4 in Scotland.
• Speed. Many FRAs are delivered in 5 to 10 working days once data is received; schemes needing new modelling are programmed with you.

Send us the site boundary and the scheme type. We’ll confirm the classification and what the exception test will need. Contact us or call 020 8156 6076.