London SuDS and drainage planning conditions: what the decision notices show

What London drainage and SuDS conditions actually ask for, how often discharge submissions fail, and how the burden varies by borough, from the decision notices we read every morning.

Trails Research·Updated 2026-09-10·5 min read
From our ongoing reading of London planning decision notices
… of drainage discharge submissions are refused
… of drainage conditions must be signed off before work starts
… of the drainage-conditioned work sits in one project type

Schemes are failing at the discharge stage: the point where a drainage condition attached at approval must be signed off before work can start. Every figure here carries its own sample and is recomputed each morning as more notices are read.

When a London council approves a scheme, it increasingly attaches a sustainable-drainage (SuDS) or flood condition. Before work starts, that condition has to be discharged: the drainage details submitted for sign-off. We read the resulting decision notices every morning, and this page sets out what they show: how often that step fails, what the conditions ask for, which kinds of project generate them, and how much the burden varies from one borough to the next. It is built from public planning records; individual schemes are never named.

Are SuDS discharge-of-condition applications being refused in London?

A refusal at the discharge stage does not mean the scheme was rejected: permission was already granted. It means the drainage details submitted to satisfy the condition did not pass, which stalls the start on site. The rate appears here once the sample clears our publication floor.

This is the stage where a drainage consultant earns the fee. The permission is in hand and the scheme is signed off; the one item still holding the start date is the drainage submission. Getting it approved first time is a programme saved, and the notices show how often that is not what happens. The grounds refusals cite are on their own page.

Does the drainage-condition burden vary between boroughs?

Rates differ between boroughs, driven by local flood-risk geography and each authority's policy stance. The borough range appears here once enough boroughs have been read past the publication bar.

What kinds of project pick up drainage conditions?

The project-type breakdown (new-build housing, basements, extensions) appears here once we have read enough notices to report it reliably.

What do the drainage conditions actually demand?

Common condition themes (attenuation and storage, discharge-rate limits, maintenance regimes, verification evidence) surface here as we read more notices.

Where does this come from?

We read planning decision notices across inner- and outer-London boroughs as part of our monitoring work, recomputed daily. Every figure on this page carries its own sample; a rate is published only when that sample clears a floor, and where it does not we withhold it rather than dress up a thin number. Only aggregate figures appear here: never a scheme address, an application reference, or condition wording. For sources and refresh cadence, see the methodology page.

This is the free, public view. Flood and drainage consultants use Trails to see the same picture at scheme level: every live application in their patch carrying a drainage condition, and the architect behind each one.

See how Trails works for consultants →

Frequently asked questions

Are SuDS discharge-of-condition applications being refused in London?
Yes: a material share of drainage discharge-of-condition submissions are refused. That is the stage where a drainage condition attached at approval is submitted for sign-off before work can start, so a refusal there is a different signal from a refusal at the application stage: the scheme was approved, but the drainage details submitted to discharge the condition did not pass. The count and the rate are on this page, recomputed daily from the decision notices we read across London.
What share of London planning approvals carry a drainage or SuDS condition?
It varies widely by borough, driven by local surface-water flood-risk geography and each authority’s policy stance. Sustainable drainage conditions are increasingly standard on approvals that add roof or hardstanding area, or that put habitable space below ground. The London-wide share and the range across boroughs are on this page, and the borough comparison guide ranks every borough we have read deeply, with the number of notices behind each figure.
What kinds of project pick up drainage conditions most often?
The drainage-conditioned work we read is concentrated in new-build homes and flats and in basement and lightwell schemes, with extensions and conversions behind them and commercial work a small share. That is consistent with what actually drives surface-water risk: work that adds roof or hardstanding area, or that puts habitable space below ground. The live breakdown is on this page.
Where does this flood and drainage planning data come from?
It is derived from published UK planning decision notices (the same public records a planning officer issues on determination), which we read across inner- and outer-London boroughs every morning. Only aggregate figures are shown: never a scheme address, an application reference, or condition wording. Every figure carries its own sample, and the page states how many relevant decisions we have read against how many were made. See the methodology page for sources and refresh cadence.

About this data

This article reports patterns in UK planning decision notices that Trails reads across London local planning authorities, recomputed daily. Every figure carries its own sample, and the London page shows how much of each borough's decisions we have read.

→ The full London flood & drainage picture→ Methodology and sources

About Trails

Trails reads London planning decision notices every morning and shows flood and drainage consultants which schemes have just picked up a drainage condition, which discharge submissions were refused, and the architect behind each one.

See how Trails works for consultants →