Flood Risk Assessment in Hackney

A flood risk assessment in Hackney is mostly about rain. The River Lee runs along the borough's eastern edge, but the larger risk lies in the streets west of it, where heavy storms overwhelm combined sewers in Homerton, Upper Clapton, Stoke Newington and around Hackney Downs. We prepare flood risk assessments here for planning, property purchase, mortgages and insurance, along with sequential and exception tests and surface water drainage strategies.

This page covers the whole London Borough of Hackney: Hackney Central, Dalston, Stoke Newington, Stamford Hill, Upper and Lower Clapton, Homerton, Hackney Downs, Shacklewell, De Beauvoir Town, Haggerston, Hoxton, Shoreditch, Woodberry Down and the marshes by Lea Bridge, mainly in the E5, E8, E9, N16 and N1 postcode districts. Hackney Wick, on the Olympic Park side, has its own page.

Hackney's Surface Water Management Plan found that 22,500 homes and 4,000 other properties in the borough could flood more than 3 cm deep in a 1 in 100 year rainstorm.

To talk through a site, phone our experienced flood risk consultants on 01293 214444 or write to enquiries@unda.co.uk; a free, no-obligation quote usually follows within 60 minutes.

Nine critical drainage areas: where Hackney floods in heavy rain

Hackney's surface water risk is concentrated in nine critical drainage areas drawn by the council's 2013 Surface Water Management Plan. Ground falls from the north-west, along the Islington and Haringey boundaries, towards the Lee, and the plan traces overland flow along the valley taken by Amhurst Road and Wick Road. Three of the nine follow railway lines, and two cross into Islington and Tower Hamlets.

The receptor counts come from the plan's 1 in 100 year modelling and include homes, businesses and infrastructure. Its authors rejected separating the combined sewers under Wick Road and Northwold Road as too disruptive for the benefit, so new development is expected to hold water back on site instead. Our guide to what a critical drainage area means for an application sets out the extra evidence these areas bring.

The risk is expected to grow. The Greater London Authority's 2026 Regional Flood Risk Assessment places Hackney among the three boroughs with the largest share of land at high surface water risk once climate change is allowed for, and the 2025-30 London Surface Water Strategy chose the Lee Valley as one of its first two catchment partnerships (what that strategy changes for planning).

Checking an address from Stamford Hill to Shoreditch

Enter a Hackney postcode to screen it against the Environment Agency's river, surface water and reservoir data, or open our flood risk map for anywhere in England. The coral line follows the borough boundary, from Woodberry Down and the reservoirs in the north to Shoreditch in the south and the Lee in the east. The critical drainage areas are council mapping and do not appear in the screening.

Hackney Marsh, Lea Bridge and the River Lee

The Lee is Hackney's only main river. It enters the borough at Lea Bridge, where the Lee Navigation, known here as the Hackney Cut, branches off and runs south along the western side of Hackney Marshes. Much of the floodplain inside the borough is open ground: the marsh, its playing fields and the old Middlesex Filter Beds. The homes and businesses closest to the river are around Lea Bridge Road and, south of the marshes, in Hackney Wick.

• The Lea Bridge gauge. The Environment Agency's gauge normally reads 5.78 to 6.10 m. Low-lying land can flood above 6.10 m and property above 6.40 m; its highest level, 6.52 m, came on 4 January 2024, and the Agency's records place historic flooding on Lea Bridge Road at 6.78 m.
• The warning area. Lower River Lee at Hackney and Walthamstow covers Lea Bridge, Hackney Marsh and Hackney Wick, and anyone nearby can sign up for its warnings.
• Relief channel near its limit. Hackney's 2016 flood strategy records that the River Lee Flood Relief Channel almost reached capacity in 1987, 1993, 2000 and 2013.
• Ground raised by rubble. Much of Hackney Marshes stands higher than it once did because rubble from bombed buildings was tipped there after the Second World War.
• Tide and river. The 2010 Level 2 assessment found the tidal influence of the Thames reaches up the Lee only as far as the Lea Bridge sluices, so the Lee through most of Hackney floods from rain on its catchment upstream, which the Thames Barrier does not hold back.

Levels at the gauge are on our live river levels map beside the other Lee gauges. The river's full course, from Luton through Enfield and Tottenham to Bow Creek, is on our River Lea page, and the reach below Hackney is covered by our Stratford page.

Storms, hail and burst mains: what Hackney has recorded

Since the Lee spread across the marshes in 1947, Hackney's flood record has been a string of short, local events, mostly from rain and the drains. The council's 2016 Local Flood Risk Management Strategy and the 2013 plan list the ones below.

1. March 1947. The Lee flooded across Hackney Marsh and along the north-eastern edge of the borough.
2. 1997 to 2007, sewers. Thames Water's records held 44 sewer flooding incidents in the Stamford Hill area and three in Shoreditch.
3. 1999 to 2009, surface water. Incidents were logged at Brownswood Road, Cazenove Road, Stamford Hill, Mare Street, Otteway Court and Dunsmure Road, and Transport for London recorded six on Wick Road, which lies in a dip.
4. 2002 to 2010, groundwater. Standing water was recorded at Kyverdale Road and Osbaldeston Road in Upper Clapton, Curtain Road and Union Walk in Shoreditch and Elsdale Street in Homerton.
5. September 2014. A short storm of rain and hail flooded Wick Road, Kenworthy Road and streets in Dalston and Stoke Newington.
6. 11 December 2016. A burst water main flooded Northwold Road in Stoke Newington; dozens of homes and businesses were evacuated and the council opened Stoke Newington Town Hall as a shelter.
7. 23 October 2022. A thunderstorm flooded the A10 at Cazenove Road in Stamford Hill, a junction already in the strategy's records; the Mayor reported three households affected.

The flood maps show where water is modelled to go; records like these show where it has actually gone, and an assessment of a Hackney site checks both. Our article on why some floods get a formal investigation explains how the council decides which ones to report on.

Woodberry Down, the New River and the Stoke Newington reservoirs

Two storage reservoirs, built in 1833 to hold water from the New River, sit on the northern edge of the borough. The East Reservoir, owned by Thames Water and still used to hold water before treatment at Walthamstow, opened to the public as Woodberry Wetlands in 2016. The West Reservoir belongs to the council and is now a water sports centre.

• Next to the largest regeneration. The Woodberry Down estate beside the East Reservoir is being rebuilt as more than 5,500 homes over about 20 years, work that began in 2009.
• How the risk is shown. The Environment Agency's reservoir maps show where water would go if a dam failed, with the rivers at normal level and in flood; the council's emergency page lists both Stoke Newington reservoirs and the King George V reservoir in Enfield.
• The New River. Thames Water runs the New River, an aqueduct dug in the early 1600s, through Stoke Newington to the reservoirs; it is not a main river, and problems on it go to Thames Water.
• What a scheme has to show. Reservoir risk does not change the flood zone, but it bears on safe access, basement bedrooms and uses such as care homes and schools.

For a site near Lordship Road, Seven Sisters Road or the reservoir paths, an assessment says whether the reservoir extent reaches it and what that means for the layout. Our note on how reservoir flooding is assessed goes into the method.

Gravel, basements and groundwater under Shoreditch and Clapton

Most of Hackney sits on London Clay, but river terrace sand and gravel covers the clay in places, and that is where groundwater can rise. The 2013 plan's groundwater mapping shows the greatest potential in the south-west of the borough, in Shoreditch, over a large deposit of Hackney Gravel, with the recorded incidents clustered close by. Two records north-west of Stoke Newington sit on clay outside the mapped zone.

• Why it matters for basements. Water perched in gravel above the clay has nowhere to drain, so a new basement can meet it or push it towards a neighbour's cellar.
• What LP53 asks. An assessment is required for any basement in an area of elevated groundwater risk in Flood Zone 1, and a basement must not increase groundwater flooding on the site or nearby.
• Planned work. Hackney's measures in the second-cycle flood risk management plan include a borough groundwater study and a practice guide on basement development, both listed with target dates in 2024 and 2025.

The evidence a council expects before anyone digs is set out in two of our guides, on checking groundwater risk on a site and on basement and cellar conversions in a flood zone.

LP53 and the London Plan: the flood policies a Hackney application must meet

Outside the former Olympic Park area, a Hackney application is judged against the Hackney Local Plan 2033 (LP33), adopted in July 2020, alongside the London Plan 2021 and chapter 18 of the August 2026 NPPF. Policy LP53 Water and Flooding asks for a site-specific assessment in more situations than national policy does.

• National policy. NPPF policy F4 sets when an assessment is needed, F5 and F6 the sequential and exception tests, and F8 asks for drainage to the 2025 National Standards for sustainable drainage.
• The London Plan. Policy SI 12 asks schemes to manage flood risk from all sources and residual risk; SI 13 sets the London drainage hierarchy, with a combined sewer as the last resort.
• When LP53 needs an assessment. Any development in Flood Zone 2 or 3, including minor works and changes of use; sites of a hectare or more; smaller Flood Zone 1 sites at risk from other sources; major or basement schemes in high surface water or groundwater risk areas; and all development in Flood Zone 1 inside a critical drainage area.
• Runoff and sewers. Greenfield runoff rates through on-site storage and SuDS, with planning obligations where that is shown to be unfeasible, and proof from Thames Water that sewer capacity exists before occupation.
• Hackney Wick and the Olympic Park. Sites inside the former Legacy Corporation boundary follow its Local Plan 2020 to 2036 instead; our Hackney Wick page sets out how.

The council has started a new Local Plan, which it expects to use from 2029, so LP53 governs for some years yet. The flood evidence behind it is older still: a Level 2 SFRA from 2010 with a climate change supplement of 2018, and the 2016 flood strategy.

Combined sewers and SuDS: what Hackney expects of drainage

Hackney's drainage is mainly combined sewers, carrying rain and foul water in one pipe, so rain kept out of the pipes on one site leaves more room in them for the streets downhill, where surcharging sewers reach basements first. The council's sustainable drainage page sets out what goes in with an application.

• Major schemes. A sustainable drainage strategy with climate change allowances, a management and maintenance plan and the London Sustainable Drainage Proforma, as a validation requirement.
• Smaller schemes. The council asks minor applications to complete the proforma too, particularly inside critical drainage areas, and to use water butts, green or blue roofs and permeable paving.
• Its own guidance. A four-part design and evaluation guide, a surface water drainage checklist, a maintenance guide and the council's SuDS proforma spreadsheet.
• Infiltration. On London Clay a soakaway rarely works, so any claim needs testing; our BRE 365 infiltration calculator shows how a test becomes a design rate.

Two notes go further: one on the London SuDS proforma explains what each part of the form asks for, and one on combined, foul and surface water sewers explains why the type of sewer matters to the discharge rate.

From a Dalston basement to a Woodberry Down block: when you need a flood risk assessment in Hackney

Whether a flood risk assessment in Hackney is needed turns on the flood zone, the critical drainage areas, the ground and whether a basement is involved. The table covers the schemes we are asked about most often in the borough.

Reports for Hackney sites, from the Downs Estate to Lea Bridge

A flood risk assessment asks if a site is safe, a sequential test asks if it is the right place to build, and a drainage strategy asks where the rain goes. Hackney sites tend to need the following.

• Rain, river, reservoir and ground together. A flood risk assessment for a Hackney site sets the local critical drainage area, the Lee, the Stoke Newington reservoirs, the sewers and any gravel beneath it against one proposal.
• Applications judged under LP53. Hackney asks for a flood risk assessment for planning in Flood Zones 2 and 3, on sites of a hectare or more, and for any Flood Zone 1 scheme inside one of its nine critical drainage areas.
• Buying on a street that has flooded. A flood risk survey for property purchase looks at one house or flat on Northwold Road, the Downs Estate or near Lea Bridge, including its basement and the way water reaches it.
• Homes near the marshes. Housing proposed in the Lee floodplain by Lea Bridge or Hackney Marsh needs a sequential and exception test to show why the site should be used at all.
• Combined sewers almost everywhere. Because most of Hackney drains to combined sewers, a drainage strategy has to show how much rainwater the scheme keeps out of them.
• Major schemes and the London proforma. Hackney's validation list asks for a surface water drainage strategy with the London Sustainable Drainage Proforma on every major application, allowing for climate change.
• Conditions on a permission. Where consent arrives with a drainage condition, we prepare the material the council's flood team needs for the discharge of drainage conditions.
• Gravel under Shoreditch and Clapton. The surface water plan's groundwater map is highest over the Hackney Gravel in Shoreditch, so a basement there or in Upper Clapton calls for a groundwater flood risk assessment.
• Levels beside the Lee. The borough's river evidence still depends on its 2010 Level 2 assessment and a 2018 climate change supplement, so flood modelling can set current levels for a site near Lea Bridge.
• Inside the Lea Bridge warning area. Homes, hostels or schools in the Environment Agency's Lower River Lee at Hackney and Walthamstow area may need a flood warning and evacuation plan.
• Cover for flats in a critical drainage area. Owners in the Northwold Road or Wick Road areas, where hundreds of homes sit in mapped flood paths, can give an underwriter a flood risk assessment for insurance for their own building.
• Offices and workspace under LP53. LP53 expects new non-domestic buildings to reach BREEAM Excellent, and a BREEAM flood risk assessment supports the flood credits on a Shoreditch or Dalston scheme.

Council, Thames Water or the Canal & River Trust: reporting flooding in Hackney

Who to call in Hackney depends on where the water comes from. The Environment Agency deals with the Lee, the council with rain, groundwater and the roads, Thames Water with the sewers, the water mains and the New River, and the Canal & River Trust with the Lee Navigation and the Regent's Canal.

The government's long term flood risk service gives the official result for a single address. Haringey, upstream on the Lee, has its own council page, the Isle of Dogs page covers the tidal Thames near the mouth of the Lee, and our London page and the areas we cover list the rest.

Questions about flood risk in Hackney, Dalston and Stoke Newington

Unda Consulting Limited is a CIWEM Business Partner, and a senior consultant checks and signs every Hackney report before it is issued. For a site anywhere in the borough, call our chartered flood risk consultants on 01293 214444 or email enquiries@unda.co.uk.