What Is a SuDS Proforma and When Is It Required?

A SuDS proforma — also called a drainage proforma or sustainable drainage proforma — is a standardised summary form that accompanies a sustainable drainage strategy on a planning application, setting out the key drainage information in a fixed format so the Lead Local Flood Authority (LLFA) can judge quickly whether a scheme meets sustainable drainage policy. It does not replace the drainage strategy. It summarises it. A growing number of councils, every London borough among them, now ask for a SuDS proforma at validation, and a proforma that arrives incomplete or thrown together at the last minute is one of the more common reasons drainage gets flagged and an application stalls.

This guide covers what a SuDS proforma is, how the drainage proforma and the drainage strategy fit together, why authorities want one, what the London Sustainable Drainage Proforma and other LLFA-specific versions require, the data you need to complete one, and why it pays to deal with it early rather than at the end.

A SuDS proforma is a validation requirement, not an optional extra. Submit without one where it is required, or with fields left blank, and the application can stall before an officer has even weighed the scheme on its merits.

What is a SuDS proforma?

A SuDS proforma is a fixed-format summary document that distils the outputs of a site's drainage strategy so an assessing officer can check policy compliance at a glance. Rather than reading a full technical report from cover to cover, the officer sees the essentials laid out in the same order every time, and can confirm each one against the strategy behind it.

A proforma exists because sustainable drainage is judged against a consistent set of expectations. Every modern scheme is meant to deliver against the four pillars of SuDS, managing water quantity, water quality, amenity and biodiversity together, and the form is a quick way for an LLFA to see whether each has been addressed. It also asks the applicant to point to exactly where in the accompanying strategy each claim is evidenced, so nothing is taken on trust. What an officer typically reads off a completed proforma is:

• Site and existing drainage: the site, its catchment and how it drains today
• Proposed discharge route: where surface water will go, and by what method
• Runoff rates: the pre-development and post-development figures, and the restricted rate
• SuDS components: the features chosen and how they meet the four pillars
• Maintenance: who looks after each feature for the lifetime of the development

How does a SuDS proforma relate to the drainage strategy?

The drainage proforma and the drainage strategy are two documents doing two different jobs, and an authority that asks for a proforma still expects the strategy behind it. The proforma is a summary layer on top of the drainage strategy, not a substitute for it. The strategy is where the engineering lives: the ground investigation, the infiltration testing, the runoff calculations, the storage sizing and the layout that makes it all fit on the site. The proforma distils the results of that work into a short, standard form and cross-references the pages where each figure is justified.

Submitting a drainage proforma without the drainage strategy behind it does not satisfy the requirement. The form is the index; the strategy is the evidence, and the two have to agree field by field.

That relationship matters because a proforma is only ever as good as the strategy behind it. You cannot summarise a discharge rate you have not calculated, or confirm an infiltration-based design you have not tested for. It is also where the difference between a drainage strategy and detailed design shows up, which we cover in our guide to what drainage information is needed for planning permission. If the underlying strategy is thin, the proforma simply exposes the gaps in a format an officer can spot in seconds.

Why do some councils require a SuDS proforma?

Councils require a SuDS proforma for consistency and to front-load the information that matters. The LLFA is the statutory consultee on surface water drainage for major development, and it reviews a large number of schemes against the same national standards and local policies. A standard form means every submission arrives with the key outputs in the same place, which cuts the back-and-forth of requests for further information and speeds up assessment.

The Greater London Authority puts the purpose plainly:

For the applicant, that consistency cuts both ways. A well-completed proforma helps an officer say yes faster; a weak one gives them a clear, structured reason to object. Many of the reasons an LLFA objects to a drainage strategy show up first as blanks or vague answers on the proforma.

What is the London Sustainable Drainage Proforma?

The London Sustainable Drainage Proforma (LSDP) is the version used across the capital. Since 1 April 2019 all 33 of London's Lead Local Flood Authorities have required it to accompany a drainage strategy for major development, where national or local policy calls for one. It was developed by the Greater London Authority with the London Drainage Engineers' Group to bring consistency to both what applicants submit and what borough officers ask for. The London proforma is built around four sections:

• Site and project information: the site, its existing drainage and its constraints
• Discharge arrangement: the proposed route, tested against the drainage hierarchy in the London Plan
• Drainage strategy: pre- and post-development runoff rates and the SuDS measures proposed
• Supporting information: cross-references to the detailed layouts, utility plans and maintenance strategy

We set out how it works, and which boroughs require it, on our London Sustainable Drainage Proforma page, and the boroughs' own templates are published on the London City Hall website. It is required for major applications and recommended alongside minor ones.

Are there LLFA-specific proformas outside London?

Yes. There is no single national SuDS proforma, so requirements vary from one Lead Local Flood Authority to the next. London has the most uniform system, but other regions and individual councils have developed their own forms, and some rely on a local validation checklist instead.

The clearest example beyond London is the North West SuDS Pro-forma, produced by the North West Regional Flood and Coastal Committee and shared through The Flood Hub, which several North West authorities ask developers to complete. It requires applicants to confirm that SuDS components have been designed in line with the CIRIA SuDS Manual (C753) and that flows in excess of the 1 in 100 year rainfall event have been considered. Elsewhere, authorities such as Essex and Surrey publish their own technical assessment proformas, and many councils fold equivalent requirements into their local validation lists.

The practical lesson is the same everywhere: check the local planning authority's validation list and the LLFA's published guidance at the start of a project, not the day before submission.

What data does a SuDS proforma need?

A SuDS proforma needs the core outputs of a completed drainage design, presented as evidence rather than intention. The exact fields differ between authorities, but the information nearly always comes down to the same set of answers, each backed by a calculation, a test result or a drawing.

The bar has risen with the 2025 National Standards for Sustainable Drainage Systems, which set a discharge hierarchy prioritising reuse and infiltration, and an interception target that at least the first 5mm of rainfall be managed on site. A proforma that leans on piped discharge without ruling out managing water closer to source, or that claims infiltration without BRE 365 test results to support it, is likely to draw a query. The standards themselves are published on GOV.UK.

They remain guidance rather than law. Schedule 3 of the Flood and Water Management Act 2010 has still not been commenced in England, so there is no statutory SuDS approval body here as there is in Wales. A House of Commons Library briefing published on 4 February 2026 records the government's position:

That is exactly why the proforma matters more than its length suggests. With no statutory approval regime in England, the validation gate and the LLFA consultation response are where the national standards are actually applied, and the proforma is the form on which your scheme is measured against them.

When is a SuDS proforma required?

A SuDS proforma is generally required whenever a sustainable drainage strategy is required, which in practice means major development. The usual triggers are:

• Ten or more dwellings on the site
• One hectare or more of site area
• Over 1,000 square metres of floor space
• Minor development at risk: in a flood risk area, or within a critical drainage area where surface water is a known problem

In London the position is clear cut: the LSDP is required for all major applications and recommended for minor ones. Outside London it depends on the authority, so the reliable check is the local validation list and the LLFA's published guidance. Because a proforma is a validation requirement rather than an optional extra, submitting without one, or with one left half-complete, is one of the reasons a planning application gets invalidated before an officer has even looked at the merits of the scheme.

Why you should not leave the SuDS proforma until the last minute

Completing a SuDS proforma honestly forces the drainage design to already exist, which is exactly why it should not be left to the end. To fill it in properly you need four things already in place:

1. An agreed discharge route down the drainage hierarchy
2. Infiltration test results where infiltration is proposed
3. Calculated pre- and post-development runoff rates
4. A site layout with room for the SuDS features

If drainage has been treated as a formality to sort out after the layout is fixed, the proforma has a way of exposing that with uncomfortable clarity. Some of the evidence also has a lead time that cannot be compressed. Infiltration testing needs trial pits at the right depth, and where groundwater is a concern, monitoring often has to run through the wetter winter months. Discover that late and a scheme can lose a whole season.

Think of the proforma as the point where your drainage strategy has to prove it holds together, not as paperwork bolted on at the end. Get the strategy right early and the proforma becomes a short, confident summary; rush it, and the proforma is where the cracks show.

If you need a drainage strategy and the SuDS proforma to go with it, Unda's drainage consultants prepare both, in line with the national standards for sustainable drainage and your authority's local requirements. See our sustainable drainage strategy and design service, and we reply to every quote request within 60 minutes.

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