Flood Risk & Drainage Requirements for Hammersmith & Fulham

Hammersmith & Fulham decides flood risk and drainage for itself. As a London borough, the council is both the planning authority that determines your application and the Lead Local Flood Authority that checks your surface-water drainage — there is no separate county body to satisfy. Roughly two-thirds of the borough sits within a flood risk zone, and the council's own planning guidance is direct about the consequence: if your site is in a flood risk zone, you must send a flood risk assessment with your application.

We prepare the flood risk assessments and drainage strategies that get schemes through Hammersmith & Fulham's validation and past its planning officers, the borough's own drainage team and the Environment Agency — for planning, property purchase, mortgage and insurance, and BREEAM, alongside sequential and exception tests and surface-water drainage strategies (SuDS).

The borough's Local Plan treats flood risk and water use as one problem under Policy CC3, and surface water run-off as its own dedicated policy under CC4 — so a scheme that satisfies the flood map but ignores the drainage hierarchy is only half-way to a compliant application here.

Flood risk and drainage for Hammersmith & Fulham planning, at a glance

• One council, two roles. Hammersmith & Fulham Council is both the Local Planning Authority that decides your application and the Lead Local Flood Authority (LLFA) responsible for surface water, groundwater and ordinary watercourses under the Flood and Water Management Act 2010.
• Two-thirds of the borough is in a flood risk zone. The council requires a flood risk assessment for any application within one, and its validation checklists extend the trigger to basements and surface-water hotspots too.
• The flagship policies are CC3 and CC4. Adopted in the Hammersmith & Fulham Local Plan 2018, Policy CC3 covers flood risk and water use and Policy CC4 covers surface water run-off and sustainable drainage, and the plan's climate change chapter treats both as core requirements.
• Major schemes need the London Sustainable Drainage Proforma. Hammersmith & Fulham is one of London's 33 Lead Local Flood Authorities that expect the pan-London proforma alongside a major scheme's SuDS strategy, following the Sustainable Drainage Design and Evaluation Guide.
• Discharge follows the greenfield-first hierarchy. The borough expects surface water run-off held to greenfield rates wherever a site allows it, tightening to three times the calculated greenfield rate as the ceiling on previously developed land.
• Free, no-obligation quote. One of our experienced flood risk consultants will get back to you within 60 minutes.

Who decides flood risk and drainage for a Hammersmith & Fulham application?

Three bodies matter, and knowing which one you are actually dealing with saves time. Hammersmith & Fulham Council is the Local Planning Authority: its officers determine your application against the Local Plan. The same council is also the Lead Local Flood Authority (LLFA), and in that role it is a statutory consultee on surface water drainage for major development — so on a large scheme you are, in effect, satisfying two different functions of one organisation. The Environment Agency sits alongside both as the statutory consultee for development affected by the tidal River Thames, taking the lead where a site sits in Flood Zone 2 or 3.

• Local Planning Authority. Hammersmith & Fulham Council determines the application and applies Local Plan policies CC3 and CC4.
• Lead Local Flood Authority. The same council, acting under the Flood and Water Management Act 2010, checks surface water, groundwater and ordinary watercourse drainage and is a statutory consultee for major applications.
• Environment Agency. Statutory consultee for sites affected by the tidal Thames, and the author of the flood zone mapping a Hammersmith & Fulham assessment has to work from.
• No Internal Drainage Board. The borough's own Local Flood Risk Management Strategy lists the council, the Environment Agency, Thames Water and the highway authorities as the risk management authorities here — there is no IDB layer to add to the picture.

Our guide to what an LLFA actually does and our explainer on the Environment Agency's planning role set out how these functions divide in most English authorities; Hammersmith & Fulham is simpler than a two-tier county because one council holds two of the three roles.

Does a Hammersmith & Fulham development need a flood risk assessment or drainage strategy?

The starting point is the flood map, but Hammersmith & Fulham's own validation requirements go further than the flood zone alone. Basements, lightwells and sites in a surface-water hotspot can all trigger a requirement even in Flood Zone 1.

If you are not sure which row applies to your site, send us the address. We check it against the current Environment Agency mapping and Hammersmith & Fulham's own validation lists and tell you what, if anything, you need — as part of a free, no-obligation quote.

Hammersmith & Fulham's Local Plan flood and drainage policies

This is where a Hammersmith & Fulham application actually gets tested. The council adopted its current Local Plan on 28 February 2018, replacing the earlier Core Strategy and Development Management Local Plan. Two policies carry the flood and drainage requirement, and a further two sit underneath them for basement schemes specifically.

Policy CC3 — minimising flood risk and reducing water use

Policy CC3 is Hammersmith & Fulham's core flood risk policy, and it requires development to reduce water use and minimise current and future flood risk by implementing a set of practical measures rather than leaving the point to national policy alone. In practice, officers use it to check that a flood risk assessment has looked at every source affecting the site — not just the Thames — and that the design keeps the development safe for its lifetime, including an allowance for climate change.

Policy CC4 — surface water run-off and sustainable drainage

Policy CC4 gives drainage the same standing as flood risk rather than folding it into a single generic clause. It expects development to cut surface water run-off and adopt sustainable drainage following the reuse-infiltrate-attenuate-discharge hierarchy, which is why a Hammersmith & Fulham drainage strategy needs to show what was ruled out (infiltration, typically, given the borough's river-gravel-over-clay ground conditions) before it defaults to a sewer connection.

Basements: SPD Housing Policy 9 and Design Policy 12

Basements get their own layer of scrutiny in a borough where lower-ground and basement rooms have taken the brunt of recent flooding. The Planning Guidance Supplementary Planning Document, adopted alongside the 2018 Local Plan, sets basement acceptability tests under Housing Policy 9 and a design-assessment requirement for lightwells and excavation depth under Design Policy 12. Both were reinforced in the emerging Local Plan review: draft Policy DH10 would require new basements to include active drainage devices against sewer flooding and restrict new basement flats in areas at risk of rapid inundation from a Thames defence breach.

The emerging Local Plan: draft policies CR7 and DH10

Hammersmith & Fulham ran a Regulation 18 consultation on a full Local Plan review between 29 October and 10 December 2025, and the consultation is now closed with responses due to be assessed. The draft climate resilience chapter carries Policy CR7, which would require development in areas at risk from any source — including a modelled Thames breach — to be made safe without increasing risk elsewhere, and names specific future defence levels the Thames Estuary 2100 plan targets for the borough. Treat CR7 and DH10 as a strong signal of where the council's thinking is heading, not as adopted law: cite the current CC3/CC4 framework for a live application, and flag the emerging policy where a scheme's timescale might overlap adoption.

Hammersmith & Fulham's SuDS and drainage requirements

Drainage is not a formality behind the flood risk assessment here — it is very often the part of the application that decides whether the scheme validates at all. Hammersmith & Fulham's own planning guidance recommends major applications follow the Sustainable Drainage Design and Evaluation Guide and complete the London Sustainable Drainage Proforma — the borough's own version of the pan-London form sits on the Greater London Authority's site as the Hammersmith & Fulham SuDS proforma.

• Infiltration first, but check it works. The SuDS hierarchy asks you to try infiltration before attenuation and sewer discharge, but much of the borough sits on river gravels over London Clay, where groundwater can sit close to the surface and defeat a soakaway that looked viable on paper. A BRE 365 infiltration test settles the question rather than assuming it.
• The four pillars still apply. Whatever the discharge route, Hammersmith & Fulham's officers expect a strategy to address water quantity, water quality, amenity and biodiversity, not attenuation volume alone.
• A combined sewer means surcharge risk, not just capacity. Nearly all of the borough's drainage runs through a Victorian combined sewer system, so a strategy has to address surcharge protection for basement and lower-ground rooms, not only how much rain a pipe can carry.
• The proforma is a summary, not a substitute. The SuDS proforma distils the strategy's key figures for the LLFA; it is only as strong as the calculations behind it, and an incomplete or last-minute proforma is a common reason schemes get flagged at validation.

Our drainage strategy and SuDS design service covers exactly this calculation, and our drainage calculators and BRE 365 infiltration rate calculator are free to use if you want a first indication before committing to a full strategy.

Hammersmith & Fulham's Strategic Flood Risk Assessment

The council's own Strategic Flood Risk Assessment is the evidence base a site-specific assessment has to sit within. It was prepared for the council by Capita URS (now part of AECOM) and is dated 2016 — it updates earlier assessments from 2009 and 2010 and draws on the borough's Surface Water Management Plan, completed in April 2015.

• Functional floodplain is narrow. The SFRA finds only a small area of functional floodplain (Flood Zone 3b) within the borough, associated with a short section of Chiswick Mall, alongside the tidal foreshore which plays a role in how the tidal Thames functions without formally counting as floodplain.
• Critical Drainage Areas are mapped, not just implied. The borough's Surface Water Management Plan identifies Critical Drainage Areas across the borough, which the SFRA maps and a site-specific assessment should check a proposal against.
• It is not the same document as the West London SFRA. The separate West London Strategic Flood Risk Assessment covers Barnet, Brent, Ealing, Harrow, Hillingdon and Hounslow only — Hammersmith & Fulham is not one of the six boroughs it assesses, so do not cite it for a Hammersmith & Fulham site.
• It feeds the sequential test for the council's own allocations. Sites the council has already allocated in the Local Plan were pre-screened against the SFRA; for any other site, the applicant carries out their own sequential and exception test where the trigger applies.

You can read the council's Strategic Flood Risk Assessment and its accompanying maps directly, alongside the Local Flood Risk Management Strategy, which explains how the council and its partners understand and manage flood risk borough-wide.

Validating a Hammersmith & Fulham application: what you need to submit

An application that is missing a required flood or drainage document does not get refused — it does not get registered at all, and the determination clock never starts. Hammersmith & Fulham publishes separate validation checklists for major and for minor/householder applications, and both name flood risk and drainage documents explicitly.

• Major applications. The council's Major Applications validation checklist asks whether the proposal is within Flood Zone 2 or 3 and relates to a basement or ground-floor level, and lists a sustainable drainage strategy (which can be included within the flood risk assessment) as a required document.
• Minor, householder and full applications. The minor and householder checklist asks the same flood zone/basement question and extends it explicitly to sites in a surface-water flooding hotspot — a broader trigger than the major checklist uses.
• Read the guidance page first. The council's own planning guidance page states plainly that if your application is for a property in a flood risk zone, you must send a flood risk assessment, and links its SFRA maps and the Environment Agency's advice.
• Missing documents are the most common invalidation reason. Our guide to why applications get invalidated for flood risk and drainage covers the documents LPAs most often treat as mandatory, and how to check what your site needs before you submit.

How national flood risk and drainage policy applies to a Hammersmith & Fulham application

Hammersmith & Fulham's own policies sit on top of the national framework, and a compliant application has to satisfy both. The National Planning Policy Framework sets the sequential, risk-based approach to site selection and the flood zone system the council's mapping follows; the September 2025 Planning Practice Guidance update extended the sequential test to surface water and groundwater sources, which matters in a borough where those two sources, not the river, cause most of the damage. The 2025 National Standards for Sustainable Drainage Systems add a rainfall-interception target on top of the discharge-rate approach Hammersmith & Fulham already applies through Policy CC4 and the London Plan.

A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct reports. They frequently travel together in a Hammersmith & Fulham submission, but they answer different questions: is the site safe, should the development be here rather than somewhere lower-risk, and where does the surface water go. Our page on NPPF flood risk guidance explains how the three tests fit together nationally, before Hammersmith & Fulham's own policies are applied on top.

Hammersmith & Fulham's flood risk profile, in brief

The borough's flood risk splits fairly cleanly by source and geography. The tidal Thames sets the flood zones along the riverside frontage from around Chiswick Mall and Hammersmith through to Sands End, held back by the Thames Barrier and the raised river walls; inland, it is the ageing combined sewer network and surface water that do most of the damage. On 12 July 2021, an intense storm flooded several hundred properties across the borough in a matter of hours, most of it foul water surcharging back into basements rather than river water — the event that hardened the council's focus on drainage evidence, not just flood-zone status, in its validation practice.

The borough's buried Counter's Creek, once a real stream and now a Thames Water sewer running roughly along the boundary with Kensington and Chelsea, is the other recurring name in Hammersmith & Fulham flood risk work — Thames Water's Counters Creek Flood Alleviation Scheme has fitted pumped protection to over a thousand basements across the two boroughs since 2018.

For the borough's full flood history, its named flood-warning areas and a place-by-place breakdown of the risk, see our guide to flood risk assessment in Fulham, which covers the physical picture in depth. This page focuses on what the council requires once you know your site is affected.

Growth, regeneration and how Hammersmith & Fulham applies its rules

Where the borough is planning growth tells you where flood and drainage capacity is likely to be scrutinised hardest.

• Old Oak Common is not decided by Hammersmith & Fulham. Part of the borough falls within the Old Oak and Park Royal Development Corporation's area, and OPDC — not Hammersmith & Fulham Council — is the planning authority for applications there. The Greater London Authority's Integrated Water Management Strategy has flagged a genuine lack of drainage infrastructure capacity across the wider Opportunity Area, so a site near Old Oak Common needs its planning authority confirmed before anything else.
• King Street, Hammersmith, is a live flood consideration. The Environment Agency's own Thames Estuary 2100 guidance for the area states directly that the King Street area is at risk of flooding, in a section of the borough earmarked for a long-running regeneration masterplan.
• Fulham's riverside sits in the highest-probability flood zone. The Environment Agency confirms a tidal defence policy applies along this stretch, and notes there is currently no dedicated riverside flood strategy for the area — which puts more weight on a site-specific assessment to fill that gap.
• Pre-application advice is available and charged. The council operates a tiered pre-application service — from written advice on a householder scheme through to meetings for larger residential and commercial proposals — which is a practical way to test a drainage approach before submission on a constrained site.

How Unda helps with flood risk and drainage for Hammersmith & Fulham planning

We are experts on flood risk and drainage in Hammersmith & Fulham's planning system, not a firm claiming a local address for the sake of it — and for this kind of work, understanding the borough's own policies and its officers' expectations matters more than a postcode. We combine the national policy framework with a close reading of the local evidence: the SFRA, the borough's Local Plan policies, the council's validation checklists, and the drainage hierarchy its LLFA function applies.

Where a clean, site-specific assessment can show a development is not actually within an area at risk, it can remove the need for further tests at application stage; where it cannot, we prepare the sequential and exception test to make the planning case instead. Read more on our flood risk assessments hub, or see the other authorities and areas we cover across England and Wales.

Flood risk and drainage services for every situation in Hammersmith & Fulham's area

Not every assessment we prepare here is for a live planning application. People come to us at different points — buying a flat near the river, renewing insurance after a scare, chasing a BREEAM credit, or discharging a drainage condition once permission is granted.

• Flood risk assessment for planning. The core report submitted with an application to satisfy the NPPF and Hammersmith & Fulham's own Local Plan policies.
• Flood risk survey for property purchase. For buyers, lenders and conveyancers when a search flags risk on a Hammersmith & Fulham home.
• Flood risk assessment for insurance. For owners facing raised premiums or restricted cover, aimed at brokers and underwriters.
• BREEAM flood risk assessment. Structured around BREEAM Pol 03, framed differently from a planning report because it is credit-driven rather than safety-driven.
• Groundwater assessment. A dedicated look at the borough's river gravels and perched water table where a basement or soakaway design depends on it.
• Flood modelling. Site-specific hydraulic modelling where national mapping is not detailed enough for a riverside or Counter's Creek-adjacent site.
• Drainage strategy and SuDS design. The surface-water engineering that satisfies Policy CC4 and the London Sustainable Drainage Proforma.
• Preliminary drainage design. An early, outline-stage read that flags infiltration and capacity problems before they affect the layout.
• Discharge of drainage conditions. The detailed-design stage once permission is granted, proving the scheme can handle the climate-change-adjusted design storm.

Official bodies and contacts for developers

Beyond the planning application itself, a handful of contacts are worth knowing if you are developing in Hammersmith & Fulham.

Frequently asked questions about flood risk and drainage for Hammersmith & Fulham planning