Wandsworth drainage strategy and SuDS requirements

Name: Wandsworth SuDS requirements and drainage planning conditions
Creator: Trails
License: https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/

When a drainage design is needed, which runoff target to use and what Wandsworth planning conditions tend to ask for.

Trails Research·Updated 2026-09-03·10 min read

Council guidance checked 3 September 2026

The short version

Wandsworth expects new development to use SuDS. A major application needs drainage and surface-water management designs. If an FRA is required, it should also show how the proposal follows the London drainage hierarchy.

Major applications: Drainage and surface-water designs
Runoff objective: Greenfield rate where technically feasible
Fallback minimum: At least 50% peak-rate attenuation

Use this as a starting point. Check the current validation list and the particular flood and drainage constraints on your site before submitting.

Start by confirming what the council asks for and which flood-risk tests apply to the site. Then use the document list and technical checks to set the scope. Further down, we look at the drainage conditions and refusal reasons found in the borough's decision notices.

When is a drainage strategy or FRA needed?

Project situation	What to do	Status
Major development	Submit drainage and surface-water management designs for planning review.	Required
Development requiring an FRA	Use the FRA to demonstrate the London drainage hierarchy and the use of SuDS where feasible.	Required
Brownfield development above greenfield runoff	Show how far runoff has been reduced towards the greenfield rate and meet the policy fallback as a minimum.	Required
Site in a Critical Drainage Area or affected by mapped risk	Use the current SFRA and maps to define the assessment and design scope.	Check for this site
Infiltration or a sewer connection proposed	Provide the ground or connection evidence needed to show that the proposed discharge route is realistic.	Usually required

Application documents

What to send with the application

Prepare these first

Drainage and surface-water management designs for major development
Drainage-hierarchy assessment with runoff-rate and storage calculations
Layout, levels, exceedance behaviour and the proposed discharge arrangement
Site-specific adoption, access and maintenance arrangements

Add these if relevant

Flood risk assessment where national, SFRA or site-specific triggers apply
Ground and infiltration evidence where infiltration forms part of the strategy
Connection evidence where discharge to a sewer or watercourse is proposed
Flood-resilience or evacuation evidence where the risk assessment requires it

What the drawings and calculations need to show

Establish the planning and flood-risk trigger

Check the council's strategic flood risk assessment and current maps. The Lead Local Flood Authority will review a major proposal.

Follow the drainage hierarchy

Prioritise source-control SuDS and explain the ground conditions, infiltration potential and proposed discharge route.

Control runoff and size storage

Aim for greenfield runoff. Where that is not technically feasible, demonstrate how runoff has been minimised; the Local Plan sets a minimum 50% attenuation from the pre-development peak rate.

Design for climate change and operation

Use the current climate-change allowance, show exceedance behaviour and provide site-specific adoption and maintenance arrangements from the outset.

Example scope

Major redevelopment of an existing hard-surfaced site

A brownfield site already drains quickly to the sewer and the initial layout leaves limited room for open SuDS.

Test the drainage hierarchy and flood constraints before treating the existing sewer arrangement as the default.
Aim for greenfield runoff; if that is demonstrably impracticable, show the maximum achievable reduction and at least the policy fallback.
Coordinate attenuation storage, controls and exceedance with the levels and landscape design.
State who will adopt, access, inspect and maintain the system throughout its design life.

This example shows how the submission might be assembled. It is not a drainage design. The final scope depends on the site and the proposal.

Official forms and guidance

These links were checked 3 September 2026. Forms and validation requirements do change, so check the council website again before issuing the application.

What we found in the decision notices

From … planning decision notices from Wandsworth, refreshed daily

… of the approvals read carry a drainage or SuDS condition

… of those conditions must be discharged before work starts

What the drainage conditions actually ask for

The theme breakdown appears once enough drainage-conditioned approvals have been read to report it reliably.

Allow for discharge before agreeing a start date

There are not yet enough records to publish a reliable borough figure. Check the exact wording on the permission before agreeing the programme.

Copy the condition into a schedule and list the evidence that answers each clause.
Check that the calculations, drawings, specifications and maintenance plan use the same assumptions and references.
For a pre-commencement condition, secure the written discharge before starting any work covered by the restriction.
Where the condition asks for verification, keep site photographs, installation records and as-built information.

Understand the programme effect of a pre-commencement condition .

Reasons drainage submissions are refused

We have not read enough refusals in Wandsworth to publish a useful local breakdown. The London-wide analysis is available for wider context.

Projects attracting these conditions

There are not yet enough records to publish a reliable project-type breakdown.

About the data

The observed figures are computed from the planning decision notices from Wandsworth and are recalculated as we read more. We do not publish a rate when its sample is too small. This is not a complete record of every decision made by the authority, and it cannot tell you whether a document will be accepted for a particular site. Only aggregate figures appear here. See the full methodology or the London-wide picture.

Working in another borough? Compare drainage conditions and refusal patterns across London, then look at the individual schemes and project teams behind the figures.

See how Trails works for consultants →

Frequently asked questions

When is a drainage strategy required in Wandsworth?

Wandsworth expects new development to incorporate SuDS, and major planning applications must include drainage and surface-water management designs for Lead Local Flood Authority review. The site’s flood risks and the council’s validation requirements determine whether a separate flood risk assessment is also needed.

What runoff rate should a Wandsworth drainage strategy target?

The Local Plan says development should aim for greenfield runoff. Where that is not technically feasible, the applicant must demonstrate how every opportunity to reduce runoff has been taken; the minimum is at least 50% attenuation of the site’s pre-development peak runoff.

What supporting information should the Wandsworth submission include?

Explain the drainage hierarchy and ground conditions, then show the discharge arrangement, runoff and storage calculations and the climate-change allowance used. The drawings should include exceedance routes. Name the party that will adopt or maintain the system.

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.