Lead local flood authority pre-application advice
The lead local flood authority sets your discharge rate and decides which drainage components it will accept. Asking before you lay out the plots saves redesign.
LLFA pre-application advice on drainage is worth getting before the site layout is fixed, because the lead local flood authority is the body that will set the acceptable discharge rate, decide whether infiltration is credible on your ground conditions, and say which surface water drainage components it is prepared to adopt or accept. On major development it is a statutory consultee for surface water drainage, so its position at application stage is close to determinative. Asking early costs a letter. Asking late costs a redesign of the plot layout.
The advice is not a decision and does not bind the authority. It still changes outcomes, because most of what the authority will object to later is predictable from the first exchange.
What the lead local flood authority actually does
Lead local flood authorities were created by the Flood and Water Management Act 2010 and are the county council or the unitary authority for the area, which means on a two-tier area the flood body and the planning body are different organisations. They manage local flood risk from surface water, ordinary watercourses and groundwater, and they consent works affecting ordinary watercourses.
Since 2015 they have been consulted on surface water drainage for major development, which in this context means ten or more dwellings, 1,000 m² or more of floorspace or a site of 0.5 hectares or more. Below that threshold the authority has no statutory role, although many planning authorities still take informal advice from it.
One thing that has not happened: Schedule 3 to the 2010 Act, which would create SuDS approving bodies and a separate approval regime, has never been brought into force in England. As at October 2026 the position remains that drainage is handled through the planning system. Government has indicated an intention to implement Schedule 3, so check the current position before assuming the regime is unchanged.
What it will and will not advise on
The useful answers you can get before an application are narrower than people hope, and broader than most applicants ask for.
| Will usually advise on | Will usually not advise on |
|---|---|
| The discharge rate it expects, and the basis for it | Whether permission will be granted |
| Whether infiltration is plausible on the local geology | Detailed hydraulic calculations on your behalf |
| Acceptable and unacceptable component types | The water undertaker's capacity position |
| Whether the site is in a critical drainage area | Adoption terms for a private system |
| The rainfall and climate change allowances to apply | Costs |
| Information it expects at application stage | Highway drainage design approval |
Charging varies. Some lead local flood authorities publish a pre-application fee schedule for drainage advice and some provide it free as part of the planning authority's pre-application service, so check the authority's own published page rather than assuming.
The questions worth asking in writing
Write them as numbered questions and the answers come back in the same order. Vague enquiries get vague replies.
- What discharge rate will you expect for this site, and should it be the greenfield rate for the whole site or for the developed area only?
- On a brownfield site, what level of betterment against the existing positively drained rate do you require?
- Which rainfall dataset and which climate change allowance should the calculations use?
- Is the site in a critical drainage area or an area of known surface water flooding?
- Do you accept infiltration here, and what infiltration testing standard and depth do you require?
- Which components will you not accept, and are there any you require?
- What long-term maintenance arrangements do you expect, and will you consider adoption?
- What do you need to see in the drainage submission for the application to be assessed without a holding objection?
Question eight is the one that pays for itself. An answer to it is effectively a checklist, and it stops the first consultation response being a request for information you could have supplied.
What to send with the enquiry
Keep it short and spatial. A location plan with the red line, an existing site plan showing levels and any positively drained areas, a topographical survey if you have one, and a sketch of the proposed layout showing where you think the attenuation will go.
Add the results of any infiltration testing already done, and say which standard it followed. Add the site's flood risk position from the published mapping. Say which rainfall dataset you intend to use as well, since the authority may prefer another, and our note on which rainfall dataset to cite explains the difference it makes to the storage volume. Add the proposed outfall and whether you have asked the riparian owner or the undertaker about it.
But do not send a full drainage design. You are asking for the parameters, and a finished design invites a line-by-line critique of calculations you may be about to change. It also tends to anchor the conversation on your assumptions rather than on the authority's requirements, which is the wrong way round at this stage.
Turnaround and how to use the answer
Expect weeks rather than days, and longer where the enquiry needs a site visit. Where the authority charges, the fee usually buys a stated turnaround.
When the answer arrives, put the parameters straight into the layout. The discharge rate determines attenuation volume, the volume determines the footprint, and the footprint determines how many plots fit. That chain is why drainage advice taken after the layout is drawn produces the worst outcomes.
Then quote the advice in the drainage strategy submitted with the application, with the date and the reference. Where you have departed from it, say so and give the reason in a sentence. An officer who can see that the strategy follows the advice given moves faster than one who has to work out whether it does.
Where early advice changes the layout
Four patterns recur.
Infiltration refused on clay. If the authority will not accept soakaways, you need attenuation and a controlled outfall, which needs storage volume and a gravity route to the outfall. On a flat site that can mean a pumped solution, and pumped surface water is resisted almost everywhere.
A low discharge rate. Where the authority requires the greenfield rate for the whole site rather than the developed area, the attenuation volume rises sharply and the basin grows.
Above-ground storage required. Many authorities now prefer open attenuation over tanks for maintenance and amenity reasons, which takes developable land out of the scheme and needs to be designed as usable space rather than a fenced hole.
Exceedance routing. The requirement to show where water goes when the system is overwhelmed can force finished floor levels up and change the road profile. Levels cost nothing to change on a sketch and a great deal to change on a planning drawing.
On sloping sites all four interact, and our note on managing runoff on a steeply sloping site deals with the sequencing.
Illustrative example: a 0.8 hectare greenfield site for 14 houses, where the authority requires discharge at the greenfield mean annual flood rate for the whole site and refuses infiltration on the basis of local geology. The attenuation basin and its access strip take up part of the frontage, and the plot count falls by one. Better to find that out on a sketch than after a planning submission. The figures here are illustrative only.
Before you commission anything, enter your postcode on PlanScope to see which reports the site is likely to need, including a flood risk assessment where the site sits in Flood Zone 2 or 3 or is one hectare or more.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Is the lead local flood authority the same as the planning authority?
Not always. In two-tier areas the lead local flood authority is the county council while the planning authority is the district or borough. In unitary areas they are the same organisation but usually different teams. Address drainage enquiries to the flood risk team by name rather than to general planning enquiries.
Do I need lead local flood authority advice for a single house?
It has no statutory role below the major development threshold of ten dwellings, 1,000 square metres or half a hectare. Many planning authorities still seek informal comments on smaller schemes, particularly in critical drainage areas. For one plot, proportionate information on a drainage layout is usually what is expected.
Does pre-application advice bind the authority at application stage?
No. Pre-application advice is officer advice and does not fetter the authority's discretion or the eventual decision. It still has practical weight, because a strategy that follows written advice is harder to object to and quicker to assess. Quote the advice, its date and its reference in the submitted strategy.
What happens if the authority refuses infiltration?
You design for attenuation with a controlled discharge to a watercourse or sewer instead, which needs storage volume, a gravity route to the outfall and the outfall owner's agreement. On flat sites that can point to pumping, which is generally resisted. The practical answer is often to reduce impermeable area or rearrange the layout.
Has the SuDS approval regime in the Flood and Water Management Act started?
Schedule 3 to the Flood and Water Management Act 2010 has never been brought into force in England, so surface water drainage is still handled through the planning system. Government has stated an intention to implement it. As at October 2026 the position is unchanged, so confirm before assuming a separate approval applies.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.