Lead Local Flood Authority (LLFA): What It Is and What It Means for Your Application

A Lead Local Flood Authority (LLFA) is the county council or unitary authority responsible for managing local flood risk across its area: surface water, groundwater and ordinary watercourses. On major planning applications it is a statutory consultee on surface water drainage, so its advice on your drainage strategy has to be taken into account before permission is granted.

That last clause is where the confusion usually starts. The LLFA does not decide your application, and in practice it rarely needs to, because on a major scheme an unresolved drainage objection will stall determination whatever the planning officer happens to think of everything else in the submission. Most of the delay we see at this stage is avoidable, and it is avoidable early, while the layout can still move.

Surface water is now the most widespread flood source in England, with around 4.6 million properties exposed and the figure up 43% on the previous estimate, which puts the LLFA's remit at the centre of far more applications than it was a decade ago.

What is a Lead Local Flood Authority?

LLFA stands for Lead Local Flood Authority. In England these are the county councils and unitary authorities that lead on managing local flood risk under the Flood and Water Management Act 2010. The word "local" is doing precise work in that phrase. It means flooding from surface water, groundwater and ordinary watercourses, and it excludes main rivers, the sea and reservoirs, which stay with the Environment Agency.

The role came out of the 2007 floods and the Pitt Review that followed them. Before 2010 no single local body was accountable for surface water flooding, which is much of why the response to 2007 was so fragmented, and Parliament's answer was to name one authority per area and give it a defined set of statutory duties. Unda covers the origin story in the Pitt Review: impact, legacy and the gaps that remain.

• Surface water Rainfall that runs off the ground rather than soaking in. This is the dominant source on most development sites, urban and greenfield alike.
• Groundwater Water emerging from below, usually where the water table rises seasonally. It decides whether infiltration drainage is viable at all.
• Ordinary watercourses Every ditch, brook, culvert and drain not designated a main river. The LLFA consents works affecting them under the Land Drainage Act 1991.

An LLFA belongs to a wider group of Risk Management Authorities that also takes in the Environment Agency, district councils, water and sewerage companies, internal drainage boards and highways authorities. Who is responsible for managing flood risk in England sets out how they fit together, and the Local Government Association keeps a short summary of flood risk roles and responsibilities across all of them.

Which council is your Lead Local Flood Authority?

Your LLFA is the county council or unitary authority covering the site. In two-tier areas that is the county council, not the district or borough that will actually determine your application. In unitary authorities, London boroughs and metropolitan districts, one body does both jobs.

This distinction matters more than it sounds. Two-tier means two organisations, two sets of guidance and two timetables, so that on a site in Elmbridge the borough council determines the application while Surrey County Council, as Lead Local Flood Authority, sets the drainage and SuDS requirements the application has to satisfy. Send the drainage strategy to the wrong one and it sits with a team that has no remit to comment on it. In a unitary area such as Calderdale or Kingston upon Thames the same authority reads your flood risk assessment and your drainage strategy, which is simpler, though not reliably faster.

If the site address does not make the answer obvious, find the upper-tier or unitary council for the postcode through the government's find your local council tool, then look for its SuDS or drainage planning advice pages.

Local standards then vary far more than national policy implies, which is the part that catches consultants working outside their usual patch. Essex County Council restricts surface water to the greenfield 1-in-1-year runoff rate; Somerset applies a 2 l/s/ha cap in the River Tone catchment and will not accept pumped SuDS; every London borough requires the London Sustainable Drainage Proforma. None of that is in the NPPF. Unda keeps a guide for each authority at flood risk assessments by local authority area.

One caveat on timing. England's local government reorganisation merges many two-tier areas into unitary authorities from April 2027, moving LLFA duties from county to unitary on vesting day, but the existing councils remain the LLFA for every live application until then. Local government reorganisation and what it means for flood risk and planning covers the transition.

What does an LLFA do?

Outside the planning system, an LLFA carries six statutory duties under the Flood and Water Management Act 2010 and the Land Drainage Act 1991. Its job is to lead, coordinate and record local flood risk. It does not maintain main rivers or the coast.

Two of those produce documents worth finding before you design anything. Section 19 investigation reports are a public record of where an area has actually flooded and why, so a scheme that contradicts one will not survive consultation; the asset register will tell you whether the culvert or headwall on your boundary belongs to somebody else.

The ordinary watercourse duty is the one that catches people out. If your drainage design outfalls to a ditch you need consent from the LLFA under the Land Drainage Act 1991, separately from planning permission, and there is no retrospective route if you build first. See ordinary watercourse consent (OWC) explained, and main rivers and ordinary watercourses for where the boundary between the two regimes falls.

When is the LLFA consulted on your planning application?

The LLFA has been a statutory consultee on the surface water drainage aspects of major development since 15 April 2015. The change was announced in a written ministerial statement of 18 December 2014, which set out that "the Government's expectation is that sustainable drainage systems will be provided in new developments wherever this is appropriate".

"Major development" is not a matter of judgement. Article 2(1) of the Town and Country Planning (Development Management Procedure) (England) Order 2015 defines it:

• 10 or more dwellings Or a residential site of 0.5 hectares or more where the number of dwellings is not yet known.
• 1,000 square metres or more of floor space The usual trigger for commercial, industrial and institutional schemes.
• A site area of 1 hectare or more Whatever is being built on it.
• Minerals and waste development Both are major development in their own right.

Planning Practice Guidance puts it plainly: "When considering proposals for major development the local planning authority will need to consult the lead local flood authority on surface water drainage."

A site sitting entirely in Flood Zone 1, with no river or tidal risk at all, can still face a full LLFA review, because the trigger is the scale of the development rather than the flood zone it sits in.

Below the threshold there is no statutory duty to consult, though plenty of authorities do anyway: some designate critical drainage areas where smaller schemes are caught, and Mid Sussex runs its own in-house flood risk and drainage team that reviews minor applications too. Since December 2024 the NPPF has also expected sustainable drainage on any application that could affect drainage, proportionate to its scale. No consultee does not mean no requirement.

What does the LLFA actually read in your drainage strategy?

The LLFA is checking one thing: whether the development can manage its own runoff without increasing flood risk elsewhere. It is not assessing the scheme's planning merits, its architecture, or its flood risk from rivers, and it will work through the surface water case in a fairly consistent order regardless of how the report itself is arranged.

1. Where the water goes. Whether you have worked down the discharge hierarchy, from reuse to infiltration to a watercourse to a surface water sewer and only then to a combined sewer, and evidenced why you stopped where you did. Cost alone has never been sufficient justification for dropping a tier.
2. Whether you tested that assumption. Infiltration has to be demonstrated by in-situ testing to BRE Digest 365, not assumed from a geology map. This is the single most common failure point, and the cheapest to avoid.
3. The discharge rate and the calculations behind it. Restricted to the greenfield rate the local authority specifies, modelled to the 1 in 100 year event with a current climate change allowance and an urban creep uplift.
4. What happens when the design event is exceeded. Exceedance flow routing: where water goes in a storm bigger than the one you designed for, or when something blocks. Consistently requested, consistently missing.
5. Who maintains it, and for how long. A whole-life maintenance plan for every drainage feature, with the responsible party named.

Unda's surface water drainage strategy service covers all five, and what drainage information is needed for planning permission sets out what belongs in the application against what can reasonably be left to a condition.

If you are proposing infiltration, check the ground before you commit the layout to it: Unda's soakaway ground conditions checker and BRE 365 infiltration rate calculator are both free.

What the LLFA measures you against changed in 2025. Defra published updated National Standards for Sustainable Drainage Systems on 19 June 2025, the first substantial refresh in a decade, setting seven standards covering runoff destinations, interception, extreme rainfall, water quality, amenity, biodiversity and maintenance. They remain non-statutory guidance, which does not stop LLFAs applying them as though they were not. Unda covers them fully in the 2025 national standards for SuDS and the SuDS hierarchy explained.

Does the LLFA's advice bind the planning authority?

No. The LLFA advises and the local planning authority decides. Its response is a material consideration the planning authority must take into account, but the LPA can grant permission against it, and occasionally does, usually where the objection is technical rather than fundamental and can be dealt with by a well-drafted condition instead.

That distinction is narrower than it looks, because national policy points the same way. The December 2024 National Planning Policy Framework, still the framework in force as at August 2026, requires at paragraph 182:

An officer granting permission over a live drainage objection has to explain in writing why the advice was outweighed, and few will attempt that on a major application when the alternative is simply waiting for better evidence. That is why an unresolved LLFA objection works as a stop even though it is formally only advice.

There are limits on what an LLFA can ask for, and they are worth knowing. It cannot use a condition to make you fix flooding you did not cause, which betterment planning conditions covers. For the decision-maker's side of the same relationship, see what is a local planning authority (LPA)?

What happens if the LLFA objects?

Most LLFA objections are holding objections, which pause determination until the drainage evidence is resolved rather than rejecting the development in principle. The usual cause is a strategy that went straight to sewer discharge without testing infiltration first, and the usual fix is more evidence rather than a redesign.

This is where applications most often stall, so Unda covers it separately and in depth. LLFA objection: how to fix your drainage strategy works through each common objection, the evidence that clears it, and when a revision will do instead of starting again.

LLFA, LPA and the Environment Agency: who reviews what?

Three bodies can look at flood risk on the same application, and the line between them runs by flood source rather than by document.

• The Environment Agency Flood risk from main rivers, the sea and reservoirs. Consulted on development in Flood Zones 2 and 3 and within 20 metres of a main river. See the Environment Agency: flood risk and planning.
• The Lead Local Flood Authority Surface water, groundwater and ordinary watercourses. Consulted on the drainage strategy for major development.
• The local planning authority The decision-maker. Weighs both responses and determines the application.

On a riverside major scheme you will deal with all three, and it is worth being clear that the Environment Agency is not consulted on surface water at all. If you are unsure which reports your site needs, flood risk assessment and drainage strategy: do you need both? works through the decision.

Getting the drainage right before it reaches the LLFA

LLFA requirements are cheapest to meet while the layout can still move. Infiltration testing, groundwater monitoring and a discharge point that actually works are constraints on the site plan rather than additions to it, and treating them as a reporting exercise to be picked up once the masterplan is fixed is how a straightforward scheme turns into an expensive one. Retrofitting attenuation is where budgets and programmes go. By then the cheap options have gone.

Unda prepares surface water drainage strategies and SuDS designs, flood risk assessments for planning and drainage strategies for planning applications, written to the specific authority's standards rather than a generic template.

Frequently asked questions