Flood Risk and Drainage for EV Charging Infrastructure: What Developers Need to Know

There were 119,080 public chargers on the UK network on 1 April 2026, and 27,372 of them were rated 50kW or above. Almost all of it went in on land nobody picked for its flood characteristics: retail car parks, filling-station forecourts, roadside laybys, fleet depots on reclaimed industrial ground. A flood risk assessment for EV charging is not, then, a formality bolted onto the application at the end. It is the document that decides whether the electrical kit at the heart of the scheme can sit where the traffic case says it has to.

The awkward part is that the risk lands on the component developers think about least. A charger is a bollard on a plinth. The substation feeding it is a box full of switchgear with a low and fixed tolerance for water. And the framework that governs all of it changed on 17 August 2026, in a way that pulls EV charging further into the flood risk system rather than out of it.

Research published in April 2026 by Rebalance Earth with Dr Raghav Pant of the University of Oxford found that as little as 20 centimetres of floodwater can disable a secondary substation, with more than 27,000 businesses exposed to power loss and national economic losses running at roughly £90 million a day during severe weather.

When does an EV charging development need a flood risk assessment?

A site-specific assessment is required for all development in Flood Zones 2, 3a and 3b, and in Flood Zone 1 wherever the site is one hectare or more. The August 2026 National Planning Policy Framework lifted the old footnote-63 triggers into a free-standing policy, Policy F4, and widened the Flood Zone 1 net: an assessment is now needed on any site with critical drainage problems, and on any land the Flood Map for Planning or a strategic flood risk assessment shows at risk from any source, now or in future. The qualifier that used to sit here has gone. It once caught other-sources risk only where development would introduce a more vulnerable use; now the source is enough on its own.

On charging schemes the trigger is usually surface water, not a river, and under Policy F4 it now fires inside Flood Zone 1 as readily as outside it.

That widening cuts both ways. The same Framework added a surface-water-only exemption from the sequential test: where a site is at risk of surface water alone, Policy F5 no longer requires the test if the assessment shows clearly that layout, design and mitigation will keep users safe for the development's lifetime without increasing flood risk elsewhere. For a hub on a Flood Zone 1 forecourt with a mapped surface water flow path, that can be the difference between a clean application and a hunt for alternative sites. It holds only if the flood risk assessment carries the exemption, because the assessment is now the thing the exemption turns on.

• Critical drainage areas do not follow the flood zones. Most bays go on existing hardstanding in built-up catchments, and that land is frequently within a critical drainage area even where the Flood Map for Planning shows Zone 1.
• The one-hectare threshold is site area, not developed area. A hub occupying one corner of a 1.4-hectare retail car park sits on a site of one hectare or more. The red line decides it, not the footprint.
• Twenty metres from a main river pulls in the Environment Agency. Under the national flood risk standing advice, last updated on 28 May 2026, an authority must consult the Agency on major development in Flood Zone 1 within 20 metres of a main river, culverted ones included. Riverside car parks in market towns are the standing example.
• New plant changes the use in flood risk terms. Putting permanent electrical infrastructure onto land that was only ever a car park introduces an essential infrastructure use where there was a less vulnerable one. That is the whole of the next section.

If you want the general position on triggers rather than the EV-specific one, our guide to when you need a flood risk assessment covers it in full.

Why a charging scheme is not one land use in flood risk terms

This is the point most EV submissions miss, and the August 2026 NPPF has just sharpened it. A charging hub is not one classification under the flood risk vulnerability classification. It is at least two, sitting in different rows of the compatibility table inside the same red line, and the Framework has just moved the charging equipment itself into the more demanding row.

Car parks are less vulnerable development. That row is appropriate in Flood Zones 1, 2 and 3a without an Exception Test, and should be refused in Zone 3b. The charging equipment is now a different matter. Where the old Annex 3 treated chargers as ancillary plant to a car park, Annex F, Table 2 of the new Framework names the use in its own right.

So an essential infrastructure element is now baked into the definition of the scheme, not argued into it. A grid or primary substation was already essential infrastructure; co-located battery storage sits there too, under electricity storage; and the charging stations themselves have joined them. The car park surfacing is all that stays less vulnerable.

Two consequences follow, and they pull in opposite directions. The first is a note beneath Table 3: for a mixed development, the highest vulnerability category applies unless the scheme is considered in its component parts. Left unsplit, a hub is now an essential infrastructure development by default. Either you argue it in parts in the assessment, or you accept the harder row for the whole red line.

The second is a genuine opening. As essential infrastructure, an EV charging hub now has a route through the Exception Test even in Zone 3b functional floodplain, where a plain car park would simply be refused, provided it is designed to stay operational and safe in a flood, with no net loss of floodplain storage.

That is the trade the reclassification makes. It hands EV charging a way into higher-risk land that a car park does not have, and in the same breath imports an operational-in-flood design duty that a car park never carried. In Zone 3a the note is that essential infrastructure "should be designed and constructed to remain operational and safe in times of flood"; in Zone 3b, that plus no net loss of storage and no impedance of flows. Neither is a box to tick after consent. Both are levels-and-layout decisions for concept stage.

One qualifier keeps this in proportion. The Exception Test, and this whole essential infrastructure machinery, engages only where the site sits in a flood zone defined by rivers or the sea. Where the risk is surface water alone, the common case for a forecourt hub, Policy F6 does not bite at all, and the route is the surface-water exemption above: the flood risk assessment demonstrating lifetime safety under Policy F7. Getting that distinction right at the start decides which test you are even answering.

The substation is the weak point, not the charger

Distribution network operators already assess substation flood risk, to a standard more demanding than most planning submissions apply. Engineering Technical Report 138, published by the Energy Networks Association, requires predicted flood depths to be increased by 300 millimetres for uncertainty in data and modelling, with a further 20 per cent added for climate change on fluvial and pluvial sources. Where a site serves more than 10,000 unrecoverable connections, resilience against a 1-in-1,000-year event is the target.

That standard is applied by the network operator, at grid-connection stage, to protect network reliability. It is not applied by the local planning authority, which is answering a different question: whether the development is safe for its lifetime and does not increase flood risk elsewhere, now under Policy F7 of the August 2026 NPPF, reworded from "should only be allowed where" to "should be refused unless". The safety case is now something the scheme has to win rather than merely offer.

Two flood assessments are therefore done on the same site, to different standards, on separate timetables, for different purposes, and on most schemes neither party ever sees the other's work.

The consequence is predictable enough. A hub gets permission on an assessment that treats the substation compound as hardstanding. The operator's own flood assessment then requires a plinth, a raised floor level or a relocation that the approved layout has no room for. That means a redesign, fresh drainage calculations and often a variation application, arriving at the point in the programme where the connection agreement has already been signed. Note too that the two assessments may not even use the same climate change allowance, since ETR 138 sets its own uplift rather than following the Environment Agency's.

The design levels that never get reconciled

Three separate standards each set a height for the same charging bay, and nothing in the planning system requires anyone to reconcile them. PAS 1899:2022, the specification for accessible charging, puts the socket or outlet between 800 and 950 millimetres above the surface, the payment terminal's lowest point between 800 and 1,000 millimetres, and controls between 800 and 1,200 millimetres. It also wants a smooth, stable, slip-resistant, well-drained and uniform ground surface, at least 1,200 millimetres of clear space in front of the point of access, and a dropped kerb within 20 metres where the charge point sits at footway level.

Read the accessibility figures against a design flood level plus 300 millimetres of freeboard and the conflict is plain. On a site with a 600-millimetre design depth, the freeboard level lands at 900 millimetres, which is inside the accessible socket window. Accessibility pulls the equipment down and takes the kerbs away; flood resilience pushes it up and wants the kerbs kept. On a hub in Zone 3a or 3b the resilience side is no longer optional good practice. Keeping the charging station operational and safe in a flood is what the essential infrastructure classification now demands.

The guidance offers no clean answer, and it is better to say so than to pretend otherwise. What works in practice is to resolve it in the layout rather than in the specification: put the accessible bays at the high point of the site, fall away from them, raise the substation and equipment housing on a plinth instead of raising the bays, and route exceedance flows through the circulation area rather than the charging bays. That is a levels exercise for concept stage. No drainage condition can retrofit it.

What changes when a car park becomes a charging hub

The usual assumption is that a hub on existing hardstanding adds no impermeable area, so surface water is somebody else's problem. It adds more than people expect, and it changes where water goes as well as how much of it there is.

1. Quantify what is genuinely new. Canopies, equipment housing, transformer plinths and substation compounds all add roofed or sealed footprint. Kerbed and bunded compounds also redirect flows, which matters even where the area figure barely moves.
2. Work down the discharge hierarchy and record why each tier failed. The 2025 National Standards for Sustainable Drainage Systems set the order: collect for reuse, infiltrate, discharge to a watercourse, discharge to a surface water sewer, and only then to a combined sewer. From August 2026 that hierarchy carries direct policy weight. Policy F8 now requires drainage to be designed in accordance with the national standards for all development, major or minor, and cost alone has never been a sufficient reason to skip a tier. Our explainer on the SuDS hierarchy sets out how each step is tested.
3. Test infiltration properly, or rule it out properly. A BRE Digest 365 test on a former filling-station apron will often fail, and it should fail on the record, with the result in the strategy. An unevidenced assertion that infiltration is unfeasible is among the more common reasons a drainage strategy comes back.
4. Treat interception as a design requirement. The National Standards set a 5mm interception target. Where the only soft landscaping is a strip of verge, meeting it takes deliberate design rather than a note in the strategy.
5. Deal with the pollution pathway. A charging bay is still a vehicle-standing area, and where battery storage is co-located the National Fire Chiefs Council's grid-scale energy storage guidance, revised in December 2025, expects containment and management of water run-off, with drain closure valves and bunded or kerbed areas shown on the site plan. Those valves and bunds belong to the drainage design, not to the fire strategy alone.

One further change is worth flagging on riverside and town-centre sites. Policy F8(3) is new for 2026: it resists any fresh culverting of a watercourse without compelling reasons, and pushes schemes to open up and renaturalise existing culverts where they can. A forecourt crossed by a culverted ordinary watercourse can no longer treat that culvert as invisible.

Permeable paving is the obvious answer and often the wrong one. It works where infiltration rates support it and the sub-base is not compromised by heavy plant movements or existing contamination. On a brownfield forecourt, one or both of those conditions usually fails.

The gap where nobody statutorily consults the LLFA

Here is the structural problem with charging schemes. A lead local flood authority must be consulted on major development with surface water drainage. Major development means ten or more dwellings, a site of 0.5 hectares or more for residential, a building or buildings creating 1,000 square metres or more of floor space, or development on a site of one hectare or more.

A charging hub creates almost no floor space. If the red line also comes in under a hectare, the scheme is not major development, and there is no statutory obligation on the authority to consult the drainage authority at all.

A hub can therefore be consented with no input from the drainage authority, while still adding impermeable area and permanent electrical plant to a catchment already at capacity.

The August 2026 NPPF closes part of that gap, but only part. Annex C now lists a SuDS statement, setting out how the national SuDS standards have been met, as a national information requirement for any proposal that could affect drainage. On a planning application, an officer should now expect to see one whether or not the LLFA is a statutory consultee. Where there is no application, though, the requirement has nothing to bite on.

Permitted development is where that shows. The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 came into force on 29 May 2025 and widened Class E considerably: upstands up to 2.7 metres, and equipment housing up to 3 metres high and 29 cubic metres in any non-domestic off-street parking area, subject to exclusions within 5 metres of a highway and 10 metres of the curtilage of a dwellinghouse or block of flats, and one housing unit per parking area. That is a useful liberalisation for operators. It also means new structures arrive with no drainage condition and no SuDS statement attached, because there is no application to carry either.

None of that removes the liability. It removes the check that would have caught the problem. Our guide to what drainage information planning permission requires covers where the obligations sit when the statutory consultation does not bite.

What a flood risk assessment for EV charging needs to contain

For a charging scheme, the standard contents list needs four additions a generic assessment will not have.

• A component-by-component vulnerability position. State which parts of the scheme fall in which Annex F, Table 2 class, whether you are assessing the hub as a single essential infrastructure development or in component parts, and where the Exception Test is engaged, rather than classifying the whole red line as a car park.
• A reconciled set of levels. The design flood level with the appropriate climate change allowance, the freeboard, the finished floor level of the substation and equipment housing, and the accessible-bay surface level, shown together on one section so the officer and the network operator are reading the same drawing. On Zone 3a and 3b sites, add the demonstration that the essential infrastructure stays operational and safe in a flood.
• An exceedance route that avoids the electrical assets. Where water goes when the system is overwhelmed, and specifically that this exceedance route does not run through the substation compound, the feeder pillars or the cable trenches.
• A stated position on residual risk and operational continuity. Whether the hub is expected to keep working in a flood or merely to be safe. If the client wants continuity, say what that asks of the network operator and of the layout. These are different design briefs and they are worth separating in writing before anyone draws anything.

Pair that with the Annex C SuDS statement demonstrating the national standards, and get the four right at concept stage, and the rest of the application is ordinary work. Leave them to the drainage condition and the levels argument arrives after the connection agreement is signed, which is the expensive end of the programme. Unda prepares flood risk assessments for planning and surface water drainage strategies for EV charging, forecourt and fleet-depot schemes across England and Wales, including the substation and battery storage elements that generic assessments tend to leave out.

Common questions on charging schemes and flood risk