Flood Risk Assessment in Haringey

Haringey is unusual in one way that shapes every drainage and flood risk decision on a planning application: the council is both the local planning authority that determines your application and the Lead Local Flood Authority that assesses your drainage. There is no county tier to defer to, so the surface-water strategy the borough expects — and the way it reads a flood risk assessment — is decided in-house. Getting a development consented here means satisfying Haringey on flood risk and on drainage in equal measure, against its own Local Plan policies, its 2015 Strategic Flood Risk Assessment and its published SuDS requirements.

We prepare the reports a Haringey application needs — flood risk assessments for planning, surface-water drainage strategies (SuDS), sequential and exception tests — and also for property purchase, mortgage and insurance, and BREEAM. A flood risk assessment, a sequential test and a drainage strategy are three distinct reports. They often travel together in a submission, but they answer different questions: is the site safe, should the development be here, and where does the surface water go.

Surface water is the flood source most likely to be experienced in Haringey, and the borough has mapped nine Critical Drainage Areas where the drainage bar is higher — which is why a site in Flood Zone 1 with no river anywhere near it can still need a full drainage strategy before Haringey will validate the application.

To talk through what your site needs, call one of our experienced flood risk consultants on 01293 214444 or start a quote online and we will reply within 60 minutes.

Flood risk and drainage in Haringey at a glance

The essentials an agent or developer needs before submitting in the borough:

• One authority, two roles. The London Borough of Haringey is the local planning authority and its own Lead Local Flood Authority, so both the planning decision and the surface-water drainage sign-off sit with the same council.
• Dominant risk is surface water. Haringey's Strategic Flood Risk Assessment identifies surface-water run-off as the source most likely to cause flooding in the borough, above river flooding from the Lea.
• Flagship policies. Policy SP5 (Water Management and Flooding) sets the strategy; policies DM24–DM28 in the Development Management DPD carry the detailed flood, SuDS, critical-drainage, groundwater and watercourse requirements.
• Evidence base. The adopted Strategic Flood Risk Assessment (February 2015) maps the flood zones, the functional floodplain and the nine Critical Drainage Areas an application is tested against.
• Drainage expectation. As LLFA, Haringey follows the London Plan drainage hierarchy and expects development to manage surface water at source and move discharge as close to greenfield run-off rates as the site allows, with attenuation for the 1-in-100-year storm plus climate change.
• New Local Plan coming. Haringey consulted on a draft new Local Plan between October and December 2025; the SP5 and DM24–DM28 policies remain the adopted position until that plan is examined and adopted.

Who decides flood risk and drainage in Haringey?

Because Haringey is a London borough, it is a single unitary authority for these purposes — it does not share flood responsibilities with a county council the way a district in a two-tier area does. In practice, three bodies shape a Haringey application, and one of them wears two hats.

• Haringey as local planning authority. Determines the application and decides whether the flood risk and drainage evidence is acceptable, applying the Local Plan, the London Plan and national policy.
• Haringey as Lead Local Flood Authority. The statutory consultee on surface-water drainage for major development, assessing your SuDS proposals against its own technical requirements. Its drainage and flooding team can be reached at drainageandflooding@haringey.gov.uk. Our guide to the role of the LLFA explains what this consultee looks for.
• The Environment Agency. Responsible for main rivers, including the River Lea and Lee Navigation on the borough's eastern edge, and a statutory consultee where a site sits in Flood Zone 2 or 3 next to a main river. You can screen a site on the Environment Agency's flood service.
• Thames Water. The sewerage undertaker for the borough, relevant where surface water or foul flows discharge to the public sewer and where sewer capacity is a constraint.
• The Greater London Authority. The largest schemes are referable to the Mayor of London, adding the London Plan's flood and drainage policies as a further test on top of Haringey's own.

The single most useful thing to understand early is that the drainage sign-off and the planning decision are the same council. There is no separate county LLFA to satisfy, which can make Haringey quicker to engage — but it also means the borough's in-house drainage expectations are applied directly, and a weak surface-water strategy is caught at source. Our article on how local planning authorities handle flood and SuDS sets out the wider picture.

Does a Haringey application need a flood risk assessment or a drainage strategy?

Two separate tests apply, and a scheme can trigger one, the other, or both. A flood risk assessment is driven by where the site sits and what it is for; a drainage strategy is driven by the scale of the development and whether it lies in a Critical Drainage Area. The table below sets out when each is expected on a Haringey submission.

The trap most applicants fall into is assuming a Flood Zone 1 site in the west of the borough is exempt. Haringey's Critical Drainage Areas cut across the flood zones, so a modest scheme far from any river can still owe a full surface-water strategy. If the drainage or flood risk documents are missing or inadequate, the application can be held invalid at the door — our guide to planning applications invalidated for flood risk and drainage explains how to avoid that, and you can screen any postcode against the flood datasets with our free flood risk map.

Haringey's SuDS and drainage requirements

Drainage is where a Haringey application is most often won or lost, because the council assesses it directly as the Lead Local Flood Authority. Haringey expects sustainable drainage on all major development and reviews the proposals against its published SuDS Requirements for the LLFA Technical Assessment. The starting point is the London Plan drainage hierarchy: reuse rainwater, then let it soak away, then release it slowly to a watercourse, and only discharge to the sewer as a last resort.

• Follow the drainage hierarchy. Store and reuse, then infiltrate, then discharge to a watercourse, then — only if nothing else is feasible — to the sewer, with each step down justified in the strategy.
• Aim for greenfield run-off rates. In line with the London Plan, surface water should be managed at source and discharge moved as close to greenfield run-off as the site allows, with meaningful betterment on previously developed sites.
• Attenuate the design storm. Demonstrate no increase in run-off up to and including the 1-in-100-year event with an allowance for climate change, with exceedance flows routed safely.
• Prove or discount infiltration. Where soakaways are proposed, back them with BRE 365 infiltration testing; London clay across much of the borough often limits infiltration, which has to be shown, not assumed. Our geology and ground-conditions checker and BRE 365 calculator give an early read.
• Address the four SuDS pillars. Water quantity, water quality, amenity and biodiversity all have to be answered, in line with the 2025 national standards and the four pillars of SuDS.
• Complete the proforma. London boroughs expect a SuDS proforma summarising the scheme; our guide to the SuDS proforma explains what it captures.

Most Haringey drainage objections come down to the same handful of failings: a strategy that jumps straight to the sewer without justifying the steps above, discharge rates that are not restricted to greenfield equivalents, infiltration claimed without BRE 365 evidence, or no exceedance route for storms beyond the design event. Our article on why an LLFA objects to a drainage strategy works through each, and the drainage calculators help size storage before design begins. Where a condition needs discharging later, we handle the detailed drainage design stage too.

Haringey's Local Plan flood and drainage policies

The requirements above are anchored in Haringey's adopted development plan. The strategy sits in Policy SP5 of the Local Plan: Strategic Policies (2013–2026, with alterations adopted in July 2017), and the detailed tests sit in policies DM24 to DM28 of the Development Management DPD (adopted 2017). The table names each policy and what it obliges an applicant to demonstrate; the flagship policies are then explained below.

Policy SP5 — Water Management and Flooding

Policy SP5 is Haringey's strategic water policy. It requires development to reduce flood risk across the borough, to incorporate sustainable drainage, and to protect and improve water quality, applying a risk-based sequential approach to steer development away from the areas most at risk. It is the umbrella under which the DM policies operate, so a Haringey submission should show how the scheme delivers on SP5's aims as well as meeting the detailed DM tests.

Policy DM24 — Managing and Reducing Flood Risk

Policy DM24 carries the detailed flood risk requirement. It applies the sequential and, where necessary, exception tests, and requires development to be safe for its lifetime, accounting for climate change, without increasing flood risk elsewhere. In practice this means a site-specific flood risk assessment scaled to the flood zone and the vulnerability of the use, which is where the flood risk vulnerability classification comes in.

Policy DM25 — Sustainable Drainage Systems (SuDS)

Policy DM25 requires development to incorporate sustainable drainage in line with the drainage hierarchy, to restrict surface-water run-off and to manage it as close to source as possible. It is the policy your drainage strategy answers directly, and the one the Lead Local Flood Authority technical assessment is built around. A scheme that cannot show it has worked down the hierarchy, or that discharges freely to the sewer, is unlikely to satisfy DM25.

Policy DM26 — Critical Drainage Areas

Policy DM26 is the local twist that catches out sites nowhere near a river. Haringey has nine Critical Drainage Areas — identified through the Greater London Authority's Surface Water Management Plan — where surface-water flooding is concentrated and the drainage requirements are stricter. Development in a CDA has to meet enhanced surface-water standards regardless of its flood zone, so confirming whether a site sits inside one is an early, essential check.

Haringey's Strategic Flood Risk Assessment

Haringey's Strategic Flood Risk Assessment was produced by Jeremy Benn Associates and published in February 2015. It looks at flood risk from all sources across the borough and is the evidence base behind SP5 and DM24–DM28. For an applicant, three things in it matter most.

• It maps the flood zones and the functional floodplain. The SFRA classifies the functional floodplain (Flood Zone 3b) as the borough's high-function floodplain, which constrains what can be built where and informs the sequential test.
• It identifies the nine Critical Drainage Areas. These are the surface-water hotspots that trigger the enhanced DM26 requirements — the SFRA and the council's mapping are where you confirm whether your site falls within one.
• It confirms surface water as the dominant source. The assessment finds surface-water run-off the source most likely to cause flooding in Haringey, which is why the borough weights drainage so heavily.

The SFRA dates from 2015, and Haringey is preparing a new Local Plan with a refreshed evidence base, so it is worth checking the current council mapping alongside it. Where the national mapping or the SFRA is too coarse for a specific site — for example next to the Moselle Brook or the Lee Navigation — site-specific flood modelling may be needed to establish accurate levels.

What must accompany a Haringey application to validate?

Haringey's local validation requirements set out the flood and drainage documents an application must include to be registered. Submitting without them is the most common cause of avoidable delay, because the application is not validated until the missing evidence arrives.

• A site-specific flood risk assessment where the site is in Flood Zone 2 or 3, is 1 hectare or more in Flood Zone 1, sits in a Critical Drainage Area, or is otherwise flagged for surface-water risk.
• A surface-water drainage strategy for major development, demonstrating SuDS in line with DM25 and the LLFA technical requirements, with supporting calculations.
• A sequential test, and where it is passed but risk remains, an exception test, where the site lies in a higher-risk flood zone.
• A completed SuDS proforma summarising the drainage approach for the LLFA's assessment.
• Infiltration evidence where soakaways are relied on, and modelling outputs where flood levels have been derived for the site.

Getting the drainage information right at validation — rather than leaving it to be conditioned — heads off objections later. Our guide to what drainage is needed for planning permission covers what should be in at submission and what can reasonably be left to a condition.

How national policy applies in Haringey

Haringey's local policies sit on top of the national framework, which sets the baseline every English authority works from. A Haringey submission has to satisfy both.

• The NPPF and its Planning Practice Guidance establish the sequential, risk-based approach and the flood zones — the foundation DM24 applies locally. Our explainer on the NPPF and flood risk covers it.
• The Flood Map for Planning is the starting dataset for flood zones and surface-water risk, though it is indicative and often needs refining for a specific site — check it on the government's Flood Map for Planning.
• The national SuDS standards set the technical expectations DM25 and the LLFA build on, updated by the 2025 national standards.
• The London Plan adds the citywide flood-risk and sustainable-drainage policies, including the drainage hierarchy Haringey applies as LLFA — see the London Plan 2021.

Flood risk in Haringey's area

Haringey runs from the high ground around Highgate and Muswell Hill down to the Lea Valley on its eastern edge. Surface water is the dominant flood source, driven by run-off from the higher ground and by the borough's mapped Critical Drainage Areas; the River Lea and Lee Navigation bring fluvial risk along the eastern boundary, and the culverted Moselle Brook and Pymmes Brook shape risk through the middle and north of the borough. Recent surface-water flash floods, including in July 2021 and August 2022, prompted the council to commit further flood-mitigation funding and refresh its local flood risk strategy.

This page is about what the council requires; for the full picture of local rivers, flood history and how flooding behaves on the ground, see our dedicated page on flood risk assessment in Tottenham, which covers the eastern, most flood-exposed part of the borough in detail.

How Unda helps with Haringey applications

We are flood risk and drainage specialists who know the Haringey regime — the borough's dual role as planning authority and Lead Local Flood Authority, the SP5 and DM24–DM28 policies, the 2015 SFRA and the nine Critical Drainage Areas, and the SuDS technical assessment the council applies. We prepare the flood risk assessment and the drainage strategy so they answer Haringey's tests first time, and we deal directly with the council's drainage team and the Environment Agency where a scheme needs it.

Our consultants are chartered and the practice is a CIWEM Business Partner, with senior sign-off on every report. If a drainage strategy has already been objected to, or an application has been held invalid on flood grounds, we can review it and set out how to resolve it. Speak to one of our experienced flood risk consultants on 01293 214444, email enquiries@unda.co.uk, or start a quote. You can read more about our flood risk consultants and the flood risk assessments we produce.

Flood risk and drainage services for every situation in Haringey's area

Whatever the reason a Haringey site needs flood risk or drainage work, we cover it. Each of these is a distinct piece of work, matched to the question it answers.

• Flood risk assessment for planning. The core report for a Haringey application — flood risk assessment for planning.
• Surface-water drainage and SuDS. Strategy and design to satisfy the LLFA — drainage strategy, preliminary drainage design and discharge of drainage conditions.
• Sequential and exception tests. The locational justification where a site sits in a higher-risk zone — sequential and exception tests.
• Property purchase and insurance. Assessments for conveyancing and for cover — property purchase surveys and insurance flood risk assessments.
• BREEAM and groundwater. A BREEAM flood risk assessment for the Pol 03 credit, and groundwater assessment where ground conditions demand it.

Haringey flood risk and drainage: frequently asked questions