Flood Risk & Drainage Requirements for Haringey

Haringey Policy DM25 requires every major scheme in the borough to cut surface water flows to the greenfield runoff rate for a 1 in 100 year critical storm, and asks minor schemes to cut their existing runoff by at least half. The rule sits in the Development Management DPD adopted on 24 July 2017, beside Policy DM24 on flood risk and Policy DM26 on the borough's nine Critical Drainage Areas. Haringey Council checks it twice, as the local planning authority and again as its own Lead Local Flood Authority.

The second thing to know before a drawing is fixed is how Haringey maps flood risk. The April 2022 Strategic Flood Risk Assessment puts land inside the Environment Agency's 1 in 100 surface water extent into Flood Zone 3a. A street with no river anywhere near it can therefore face the same tests as a plot beside the Lee. A replacement Local Plan is on its way (the Regulation 18 draft was consulted on from October to December 2025), but DM24 to DM29 and Strategic Policy SP5 decide applications today. To talk a site through, call 01293 214444 or email enquiries@unda.co.uk.

Planning authority and LLFA in one building: who decides what at Haringey

As a London borough, Haringey answers to no county tier: one council takes both the planning decision and the drainage sign-off. The council's sustainable drainage and planning page puts it in one line: "Haringey Council is both the Lead Local Flood Authority and Local Planning Authority." No internal drainage board covers any part of Greater London. What the LLFA role involves, and when it is consulted, is set out in our guide to the Lead Local Flood Authority.

How the Environment Agency handles a planning consultation, standing advice included, is covered in our explainer on the Environment Agency in flood risk planning. For the wider role of a council as planning authority, see how local planning authorities handle flood risk and SuDS.

Policies DM24 to DM29 and SP5: the Haringey Local Plan on flood risk and drainage

Haringey's adopted plan is four documents: the Strategic Policies, adopted in March 2013 and altered on 24 July 2017 (SP5 itself was not among the alterations), and three documents adopted that same day, the Development Management DPD, the Site Allocations DPD and the Tottenham Area Action Plan. The water and flood policies are SP5 and DM24 to DM29. The London Plan 2021 is part of the same development plan, so SI 12 and SI 13 apply as well.

Requirements checked November 2026.

Policy DM25 (Sustainable Drainage Systems): the runoff limits in Haringey

DM25 sets its runoff limits by the size of the scheme. Part B(a) reads: "All major development proposals will be required to reduce surface water flows to a greenfield run-off rate for a 1 in 100 year critical storm event". Part B(b) asks minor schemes to "aim to achieve a greenfield run-off rate and, at a minimum, achieve a 50 per cent reduction on existing site run-off rates", and Part B(c) asks all other development for at least one 'at source' SuDS measure; the supporting text names householder schemes, extensions and conversions among them.

The supporting text closes the usual escape route. Paragraph 4.87 says that where a scheme cannot reach greenfield, rates should be "minimised as far as possible", and that a previously developed site's existing high runoff "will not constitute justification". In practice an officer will look for the greenfield rate worked out for the site, the existing rate, the proposed rate, and the storage that closes the gap. A strategy that compares the new scheme only with the old one, or that sends roof water straight to the sewer without testing reuse, infiltration and green roofs first, draws questions from the LLFA.

How we meet it: our surface water drainage strategy for a Haringey site calculates greenfield and existing runoff and sizes attenuation for the 1 in 100 year event with climate change. It also records each step of the hierarchy that was tested and why it was or was not used. On a minor scheme the 50 per cent figure is shown against the measured existing site, so the council can see the reduction rather than take it on trust.

Policy DM24 (Managing and Reducing Flood Risk): sequential test, floor levels and Zone 3b

DM24 asks any scheme in Flood Zone 2 or 3a for "sufficient evidence for the Council to assess whether the requirements of the Sequential Test and Exception Test, where required, have been satisfied", informed by a site-specific flood risk assessment that covers every source. Part B(c)(i) sets finished floor levels "no lower than 300mm above the 1 in 100 chance in any given year, including an allowance for climate change, flood level", and Part D rules out everything except water compatible uses and essential infrastructure in Flood Zone 3b as the SFRA defines it.

Two details save work. Paragraph 4.74 says allocated sites that passed the Sequential Test during plan-making need not repeat it unless the use differs from the allocation, which matters for the Tottenham Area Action Plan sites in Flood Zone 2. And because the SFRA treats the 1 in 100 surface water extent as Flood Zone 3a, the DM24 tests can bite on sites the national flood map shows as Zone 1. Our sequential and exception test reports set the area of search and the alternative sites out for the case officer; the background is in our explainer on what the sequential and exception tests are.

Policy DM26 (Critical Drainage Areas): flood risk away from any river

DM26 is the policy that reaches sites the river maps never touch. Part A requires that "All proposals for new development within a Critical Drainage Area (CDA) will be required to incorporate measures to reduce the overall level of flood risk in the CDA." Part B adds that a scheme in a Local Flood Risk Zone must include a statement on how flood risk has been addressed, and that the council may ask for a full site-specific assessment.

The nine CDAs come from Haringey's own Surface Water Management Plan, prepared in 2011 under the Drain London programme, and each contains Local Flood Risk Zones showing where flooding is predicted. The council's published validation list also asks for a flood risk assessment with all major development and any new residential units inside a CDA. We check a site against the CDA and Local Flood Risk Zone maps at the quote stage. Where it falls inside one, we show in the report what the scheme does for the catchment beyond its own plot. More on how these areas work is in our article on Critical Drainage Areas and planning.

Policy SP5 (Water Management and Flooding): the strategic test

SP5 opens: "The Council will require all development in Haringey to be water efficient during construction and operation and to reduce all forms of flood risk." Its bullets carry the NPPF Sequential and Exception Tests, SuDS "from strategic to individual site level", and restoring the Blue Ribbon Network, including Pymmes Brook, Moselle Brook and the River Lee, "deculverting wherever feasible". Decisions on a typical application turn on the DM policies, but SP5 is the policy officers cite when a large scheme has a chance to open up a culvert and does not take it.

Policy DM27 (Protecting and Improving Groundwater Quality and Quantity): basements and infiltration

DM27 protects groundwater as a resource and asks, in Part C(b), that "Appropriate construction techniques are used in order to limit disturbance to natural groundwater flows". It bears on two things at once: deep foundations and basements that could block or divert flow, and soakaways that could carry pollution into an aquifer or a Source Protection Zone. Paragraph 4.94 is direct about the second: new development "should not propose unsuitable drainage measures, such as infiltration, which could adversely impact on water quality". Our reports treat groundwater both as a flood source and as something the drainage must not harm, and any infiltration proposal is backed by BRE 365 testing.

Policy DM28 (Protecting and Enhancing Watercourses and Flood Defences): the buffer and the culverts

DM28 Part A says new development "must be set back at a distance of 8 meters from a main river and 5 meters from an ordinary watercourse, or at an appropriate width as agreed by the Council and the Environment Agency". Part C requires major development, and asks minor development, to investigate and secure the restoration of culverted sections. Paragraph 4.101 treats culverts as flood defences and expects sites over them to examine deculverting within the flood risk assessment, naming the Moselle Brook and Stonebridge Brook in Tottenham and Northumberland Park. If the case against opening a culvert is not written down, expect the council to ask for it. We set out that case, with the levels and the reasons, in the FRA. Background on the structures themselves is in what a culvert is.

Policy DM29 (On-Site Management of Waste Water and Water Supply): sewer capacity

DM29 Part A(a) requires applicants to "Demonstrate that the local public sewer network has adequate capacity to serve the existing and proposed development", or to find another route for the water, and Part A(b) requires surface and foul systems to be kept apart. Paragraph 4.107 adds that where Thames Water has raised capacity concerns, including on the strategic Tottenham sites, the developer prepares a drainage strategy with Thames Water, including a model of network capacity, so that any upgrade is made ahead of occupation. The SFRA asks major schemes to show an agreement in principle from Thames Water for any new connection, and our drainage strategy records where that stands.

Policy SI 12 (Flood risk management) of the London Plan, beside the Lee and Pymmes Brook

SI 12 Part C says: "Development proposals should ensure that flood risk is minimised and mitigated, and that residual risk is addressed. This should include, where possible, making space for water and aiming for development to be set back from the banks of watercourses." On a Haringey site beside the Lee or the Pymmes Brook it overlaps with DM28's buffer, and the FRA answers both together.

Policy SI 13 (Sustainable drainage) of the London Plan: the six-step hierarchy

SI 13 Part B asks development to "aim to achieve greenfield run-off rates and ensure that surface water run-off is managed as close to its source as possible", preferring green over grey features. Its hierarchy runs from rainwater use, through infiltration, green attenuation and discharge to a watercourse, to a surface water sewer and finally a combined sewer. DM25 Part A points straight at it, which is why a Haringey drainage strategy has to give a reason at each step it skips.

The new Haringey Local Plan: draft Policies CR4 and CR5 at Regulation 18

Haringey is preparing a single Local Plan to replace all four 2017 documents. The Regulation 18 draft was consulted on from 10 October to 19 December 2025, and the council says it will prepare and consult on a Proposed Submission (Regulation 19) plan "in the second half of 2026". At 4 November 2026 that version had not been published. The Local Development Scheme approved in March 2025, which put Regulation 19 in May to June 2026 and adoption in February 2027, has slipped.

In the Regulation 18 draft, flood risk moves to draft Policy CR4 (Managing and Reducing Flood Risk) and drainage to draft Policy CR5 (Sustainable Drainage). Draft CR5 Part A(1) would ask all proposals to "restrict surface water runoff rates to greenfield 1 in 100 year rates, including the appropriate allowance for climate change", with no separate figure for minor schemes, and draft CR5 Part D would require a completed Haringey SuDS Proforma for all major developments and for minor developments "making significant changes to existing surface water drainage".

Draft CR4 (Regulation 18) would set FRA triggers in the policy itself, including minor schemes and changes of use inside a Critical Drainage Area, ban basements in Flood Zones 3a and 3b, and ask for Groundwater Screening Assessments where there is a groundwater risk. Watercourses would move from DM28 to draft Policy G8 (Regulation 18) and water efficiency from DM29 to draft Policy CR6 (Regulation 18). None of this has weight beyond a draft yet: the 2017 wording decides applications until the new plan is examined and adopted.

Triggers on a Haringey application: assessment, sequential test or drainage strategy

A flood risk assessment, a sequential or exception test and a drainage strategy answer three separate questions: whether the site is safe, whether it should be developed at all given the alternatives, and where the rain goes once it is built. In Haringey they are triggered by different documents, set out below.

Flood and drainage evidence left out of a submission tends to come back as a request or an objection, and it costs less to supply at the start; our guide to applications invalidated for flood risk and drainage covers the usual gaps. You can screen a postcode against the national flood zones and surface water extents on our flood risk map before you instruct anyone.

Haringey's Local SuDS Standards: what the LLFA checks in a drainage strategy

The LLFA assesses drainage against the Local SuDS Standards published in May 2025 as Appendix D of the Local Flood Risk Management Strategy. They supplement the national standards on water quantity and quality, and the LLFA says it will evaluate SuDS on "all major developments and all minor developments which are situated in or influence areas designated of being at flood risk". The council's SuDS page still links an older design requirements guide marked as a living draft of May 2016.

• Greenfield sites (LS2a). Peak runoff for the 1 in 1 year and 1 in 100 year events "should never exceed the peak greenfield runoff rate for the same event".
• Previously developed sites (LS3a, LS3b). As close as reasonably practicable to greenfield and never above the pre-development rate; where greenfield rates cannot be reached, Haringey asks for 50 per cent of the greenfield attenuation volume with outflows held at greenfield rates.
• Volume (LS5, LS6). The 1 in 100 year, 6 hour runoff volume kept as close to greenfield as practicable; where it cannot be, a maximum discharge of Qbar for the 1 in 100 year event with climate change, or hydraulic modelling showing no increase in risk downstream.
• Flooding on site (LS7, LS8, LS9). No flooding anywhere on the site during a 1 in 30 year event, no water in buildings, basements or utility plant up to the 1 in 100 year storm, and exceedance routes for anything larger.
• Water quality (LS15, LS16). On greenfield sites no runoff from the first 5 mm of rainfall; treatment where runoff is likely to be contaminated.
• Climate change. DM25 sizes storage with an allowance for climate change, which the strategy takes from the Environment Agency's climate change allowances, last updated 27 May 2022.
• Maintenance. The SFRA asks for lifetime management to be designed into the proposals, and for a Haringey SuDS Proforma with every application that needs a drainage strategy.

Paragraph F8 of the NPPF now asks for SuDS designed in accordance with the 2025 National Standards for Sustainable Drainage Systems; we found no Haringey statement adopting them, so a strategy for the borough meets both sets and says where each applies. Our summary of the 2025 National Standards explains what changed. For an early read on soakaways, the ground conditions checker, the BRE 365 calculator and our drainage calculators give a first figure. What the pro-forma asks for is in our guide to the SuDS proforma, and the usual grounds for an objection are in why an LLFA objects.

The April 2022 SFRA and the August 2024 validation list

Haringey's current evidence is the Strategic Flood Risk Assessment Level 1, Version 1.4, April 2022, prepared by Metis Consultants (the council's evidence page credits Jeremy Benn Associates). JBA wrote Haringey's Level 2 SFRA, prepared in August 2013 and revised as a February 2015 draft, which is still online and is the Level 2 evidence the DM24 supporting text refers to. The 2022 Level 1 calls it "Haringey's most recent Level 2 SFRA" and says its own mapping supersedes the 2015 maps, so flood extents come from the 2022 report. The draft Local Plan (Regulation 18, paragraph 21.64) says a new Level 2 will be commissioned for the Regulation 19 stage.

Three of its definitions change what a site needs. Flood Zone 3b is "Land within EA modelled fluvial flood risk extents predicted for up to and including 1 in 20 year return period events, allowing for the impact of flood defences", plus the Environment Agency's flood storage areas; it does not include surface water. Flood Zone 3a (surface water) is the Agency's 1 in 100 surface water extent, and sites in it are "treated as if it were in Flood Zone 3" for the NPPF and for site-specific FRAs. And Table 6-1 sets the local floor level and basement rules that sit beside DM24. Our explainer on what SFRAs are covers how councils use them.

The local validation list took effect on 29 August 2024 and is now more than two years old. It is still the council's published guidance on what to submit, but until Haringey republishes it the council cannot strictly insist on its local items before registering an application. Its flood risk assessment item repeats the national trigger and adds major development and new homes in a Critical Drainage Area; its drainage item asks major schemes for drainage details, a sustainable drainage plan and the council's drainage pro-formas. The same evidence is what DM24, DM26 and the SFRA ask for when the application is decided, so leaving it out moves the problem rather than avoiding it. Getting the drainage information in at validation, not leaving it to a condition, is the subject of our guide to what drainage information planning needs.

Chapter 18 of the NPPF on a Haringey site

The August 2026 National Planning Policy Framework holds flood risk in Chapter 18, policies F1 to F9. F4 lists when a site-specific assessment must go in with an application; one trigger is land an SFRA shows at risk from any source, which brings Haringey's surface water Zone 3a straight in. F5 is the sequential test. It exempts sites at risk of surface water flooding only where the layout and mitigation keep occupiers safe for the lifetime of the development, and on a Haringey site that exemption has to be argued in the FRA, not assumed. F6 is the exception test and F7 the safety test.

F8 echoes the borough's own policy most closely: SuDS designed to the National Standards, maintenance in place, LLFA advice taken on major schemes, and development that should "where possible remove existing culverts and renaturalise existing river channels", which is DM28 in national form. The latest revision of the flood risk Planning Practice Guidance is dated 17 September 2025. Our page on NPPF guidance and advice explains the national tests in more depth.

Where Haringey floods: surface water, the Lee and the culverted brooks

Most of Haringey's flood risk falls from the sky. The DM DPD says the SFRA "has identified surface water run-off as the greatest risk to the Borough with regard to flooding", and the storms of July 2021 showed it. The council's Section 19 report for South Tottenham records 31 reports of flooding to the council after the rain of 12 July 2021 and 47 after 25 July. The council's flood investigation page holds the reports and the strategy.

River risk is concentrated in the east. The River Lee and the Lee Navigation run along the borough's eastern edge, and the Environment Agency runs a warning area for Pymmes Brook at Upper Edmonton and Tottenham. The Moselle Brook and Stonebridge Brook run largely in culvert under Tottenham, which is why DM28 and SP5 return to deculverting. The national flood map for planning gives the starting zones; the live river levels map shows the gauges.

For the local story in the most exposed part of the borough, see our page on flood risk assessment in Tottenham; for the river from its source, our River Lea flood risk page. Haringey's place in the capital's picture is on our London flood risk hub, and the city-wide plan for rain is summarised in what the 2025-30 London Surface Water Strategy means for planning. Other councils' requirements are listed on our local authorities page.

Reports we prepare for Haringey Council applications

We have prepared flood risk and drainage reports for schemes submitted to Haringey Council. Each report below answers a different question, and each is tied to the Haringey policy or document that asks for it.

• Site-specific flood risk. DM24 and the SFRA's surface water Zone 3a decide how far a flood risk assessment has to go, from a short statement in a Local Flood Risk Zone to a full report beside the Lee.
• The planning submission. A flood risk assessment for planning written to DM24, the SFRA and the council's published validation list.
• Buying in the borough. A flood risk survey for property purchase where a search flags surface water risk on a Haringey street with no river in sight.
• Testing alternative sites. DM24 B asks for Sequential and Exception Test evidence in Flood Zones 2 and 3a; our sequential and exception test report sets the area of search out.
• Drainage for the whole scheme. DM29 wants sewer capacity and separate systems shown, which a drainage strategy brings together with the SuDS case.
• Runoff to DM25. The greenfield 1 in 100 year limit for majors and the 50 per cent cut for minors are calculated in a surface water drainage strategy.
• After permission. Where Haringey attaches a drainage condition, we prepare the information for the discharge of drainage conditions.
• National policy. Chapter 18 and the surface water exemption in F5 are explained in our NPPF guidance advice.
• Groundwater. DM27 asks for construction that limits disturbance to groundwater flows; a groundwater assessment answers it for basements and deep foundations.
• Modelled levels. The Local SuDS Standards ask for detailed hydraulic modelling where a scheme cannot meet the volume or on-site flooding standards, which our flood modelling provides.
• Safe access. DM24 B(c)(ii) asks for safe access and egress or an emergency evacuation plan, set out in a flood warning and evacuation plan.
• Foul water. DM29 B asks for a foul drainage assessment wherever non-mains drainage is proposed, covered by a foul drainage strategy.
• Homes that have flooded. The July 2021 storms flooded Haringey homes and businesses; an insurance flood risk assessment gives an insurer a site-specific view.
• Commercial land. Several Tottenham Area Action Plan site allocations are marked as in or partly in Flood Zone 2; a due diligence report covers the flood position for a buyer or lender.

Questions applicants ask about Haringey Council's flood and drainage rules

Our chartered consultants at Unda Consulting Limited can be reached on 01293 214444 or at enquiries@unda.co.uk, or you can start a quote online. Reports for applications to Haringey come from Unda Consulting Limited, a CIWEM Business Partner.