Flood Risk Assessment in Hackney Wick

Hackney Wick sits where London's regeneration story runs straight into one of the capital's oldest engineered rivers. To the west, the River Lea and the Hackney Cut hold back a floodplain that flooded routinely before Georgian engineers straightened the channel; to the east, Fish Island's converted warehouses back onto the Lee Navigation, just upstream of the tidal Thames. A flood risk assessment in Hackney Wick has to read that whole picture: the main river, the surface water that collects in a designated critical drainage area, and the groundwater sitting in the gravel beneath a neighbourhood built on reclaimed marsh. Unda prepares flood risk assessments in Hackney Wick for planning, property purchase, mortgage and insurance, and BREEAM, alongside sequential and exception tests and surface-water drainage strategies (SuDS), each built around how flooding actually behaves on this stretch of the Lea.

Speak to one of our experienced flood risk consultants on 01293 214444 or email enquiries@unda.co.uk, or start a quote below and we will come back to you within 60 minutes.

On the night of 4 January 2024, a sluice failure on the Lea Bridge system let the Lee Navigation burst its banks between Dace Road and Wick Lane, flooding around 10 acres of Hackney Wick and Fish Island and leading around 50 people to be evacuated from homes and studios.

• Dominant sources. Fluvial flooding from the River Lea and the Lee Navigation, surface water within Hackney's Critical Drainage Area 1 (CDA1), and groundwater in the river terrace gravels beneath the site.
• Flood zones. Hackney Wick includes land mapped as Flood Zone 2 and Flood Zone 3, and even lower-probability parts of the neighbourhood still sit inside CDA1.
• Lead Local Flood Authority. Hackney Council on the west side of the Hackney Cut; Tower Hamlets Council across the water in Fish Island.
• Planning authority. Hackney Council and Tower Hamlets Council now determine applications here, since planning powers passed back from the London Legacy Development Corporation on 1 December 2024.

Flood risk in Hackney Wick: the Lea, the Cut and surface water

Hackney Wick's flood risk starts with water management, not just weather. The neighbourhood sits inside the Bow Back Rivers, a network of channels cut through the historic Lea floodplain in the 18th and 19th centuries and still operated as a single system today. Around 1770 the Hackney Cut straightened the River Lea, taming the marsh that once flooded routinely and opening the ground for the mills, factories and wharves that gave Fish Island its name. The fluvial flooding risk today comes from that same engineered system: the River Lea is a designated Main River, so the Environment Agency assesses and manages it, while the Lee Navigation and the Hackney Cut are managed for boat traffic by the Canal & River Trust.

The Lea Bridge Sluices, just north of Hackney Wick, hold the Lee Navigation at a steady level upstream of Old Ford Lock and pass floodwater on towards the tidal Bow Creek. Hackney Wick and Fish Island sit immediately upstream of that tidal limit, so day-to-day the risk here is fluvial and pluvial rather than tidal — though the wider Isle of Dogs and Lea Valley planning framework extends Thames Estuary 2100 considerations up the tidal reaches of the Lea towards Stratford, so a site-specific assessment needs to check exactly where a plot sits against that boundary.

Surface water is just as significant, and it is increasingly the dominant flood source across dense parts of the capital: the 2025-30 London Surface Water Strategy is a direct response to that pattern. Hackney Council's Surface Water Management Plan designates Hackney Wick as Critical Drainage Area 1 (CDA1), one of nine such areas across the borough where the combined effect of surface-water runoff from multiple developments raises the risk of flooding on and off site. Much of the ground here was built up as hard industrial standing long before modern drainage standards existed, and the Victorian combined sewer network — including the Northern Outfall Sewer, which begins its run to Beckton at Wick Lane — can surcharge under intense rainfall, a pattern covered in more detail in our guide to sewer flooding. Beneath the surface, British Geological Survey mapping shows recent alluvium over Hackney Gravel (a river terrace deposit) over London Clay and the Lambeth Group: ground that generally holds water near the surface and, combined with decades of industrial made ground, complicates both infiltration drainage and the reading of groundwater flooding on individual sites.

A history of flooding in Hackney Wick

Before the Hackney Cut was built, the marshland that became Hackney Wick and Fish Island flooded as a matter of course, which is why so little was built here until the canal cuttings of the 1700s and 1800s tamed the Lea enough for industry to move in. That engineered stability has held for most of the last two centuries, but it depends on infrastructure that can still fail. On 4 January 2024, Storm Henk brought heavy rain across east London; by the evening, the "high-high" water-level alarm had sounded at both Lea Bridge Sluices, and Sluice B had failed and needed to be opened manually. The Lee Navigation burst its banks between Dace Road and Wick Lane, submerging around 10 acres of Hackney Wick and Fish Island under water reported as around a metre deep in places.

London Fire Brigade sent around 10 fire engines and 70 firefighters to the area, leading roughly 50 people to safety and carrying out welfare checks on around 100 more who stayed in unaffected properties. A subsequent Section 19 flood investigation by Tower Hamlets Council, published in April 2025, recorded 61 reports of internal property flooding from the event. Space Studios — a charity providing affordable workspace for artists, including the London Centre for Book Arts — was among the worst-hit buildings, and a live-work unit at the former Britannia Works Factory on Dace Road took on around a metre of water. A local bookshop on Dace Road was also flooded overnight.

• 4 January 2024. Storm Henk triggers a sluice failure at Lea Bridge; the Lee Navigation overtops between Dace Road and Wick Lane.
• Around 10 acres flooded across Hackney Wick and Fish Island, with roughly 50 people evacuated and around 100 given welfare checks.
• 61 internal flooding reports recorded in Tower Hamlets Council's Section 19 investigation, published April 2025.
• Long history of marsh flooding predates the Hackney Cut (built around 1770), which first made large-scale development of the area possible.

Planning and drainage policy in Hackney Wick

Hackney Council is the Lead Local Flood Authority for the part of Hackney Wick that sits west of the Hackney Cut, coordinating flood risk from surface water, groundwater and ordinary watercourses and holding the borough's flood asset register; Tower Hamlets Council carries the same role across the water in Fish Island. Until 1 December 2024, planning applications across the wider Queen Elizabeth Olympic Park fringe — including Hackney Wick and Fish Island — were decided by the London Legacy Development Corporation (LLDC). Statutory Instrument 2024/918 ended the LLDC's planning powers from that date, so applications are now determined by Hackney Council or Tower Hamlets Council depending on which side of the Cut a site sits, working from the adopted LLDC Local Plan 2020–2036 place-based policies for Hackney Wick and Fish Island alongside each council's own Local Plan.

Those place-based policies matter because of what the evidence behind them found. A Flood Risk Review prepared for the Legacy Corporation concluded that, allowing for predicted climate change flood heights, simply trying to resist floodwater on Hackney Wick masterplan sites is likely to be dangerous — pushing schemes here towards resilience and controlled water entry rather than pure defence. One nearby brownfield scheme on Wallis Road shows what that looks like in practice: with no existing building to offset lost floodplain storage, the design used the site's existing shipping containers and a permeable, louvred ground floor, agreed with the Environment Agency and the former Legacy Corporation, so floodwater could enter flexible workspace at ground level rather than displace flood storage the site could not otherwise replace.

Because Hackney Wick sits inside CDA1, Hackney's sustainable drainage guidance applies alongside the borough-wide requirement to control surface water at source, and a surface-water drainage strategy is expected on the great majority of schemes here, not only the largest sites. A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct reports. They often travel together in a Hackney Wick planning submission, but they answer different questions: is the site safe, should the development be here, and where does the surface water go. Nationally, that framework sits within the wider NPPF flood risk policy that governs planning decisions across England, and Unda's NPPF flood risk guidance sets out how it applies more widely.

Development and regeneration in Hackney Wick

Hackney Wick is being rebuilt at a pace few London neighbourhoods can match, and almost all of that growth is happening on or beside the same floodplain the Hackney Cut was built to control. East Wick and Sweetwater, framing the western edge of Queen Elizabeth Olympic Park, will deliver around 1,165 homes; its first phase of 302 homes is complete and sold or let, and its second phase of 210 homes is under construction. Around Hackney Wick station, a separate scheme is bringing forward 190 new homes — half of them affordable — across four buildings, alongside more than 4,000 square metres of commercial space. Across Fish Island, Victorian and Edwardian warehouses within the conservation area are being converted from industrial use into the mixed residential, studio and workspace buildings that now define the area, several of which sit at ground level in Flood Zone 3 — part of a national pattern our analysis of new homes in flood risk areas looks at in more detail.

That pace of change has not gone unchallenged. Campaigners including Save Lea Marshes have raised concerns that further tall-building proposals near Hackney Marshes, on the opposite bank of the wider Lea Valley, could reduce flood storage capacity across the catchment — a reminder that flood risk in Hackney Wick is shaped by decisions taken well beyond any single site boundary, and why an assessment here has to look at the wider Bow Back Rivers system rather than the plot alone.

• East Wick and Sweetwater. Around 1,165 homes on the Park's western edge; Phase 1 (302 homes) complete, Phase 2 (210 homes) under construction.
• Hackney Wick station scheme. 190 new homes, half affordable, with over 4,000 sqm of commercial space.
• Fish Island conservation area. Warehouse-to-workspace and warehouse-to-residential conversions continue across a site largely mapped Flood Zone 3.
• Catchment-wide pressure. Local campaigners have raised flood-storage concerns over further development around the wider Lea Valley floodplain.

How Unda helps in Hackney Wick

Unda has prepared flood risk assessments and drainage strategies for sites across London's river and canal-side neighbourhoods — from the tidal Thames at the Isle of Dogs and Vauxhall to the upper Lea at Ware and Hertford, and the full range of areas Unda covers — and we bring that same approach to Hackney Wick: reading the River Lea, the Hackney Cut and the CDA1 surface-water designation together, rather than treating a site's flood zone in isolation. Our flood risk consultants deal directly with Hackney Council, Tower Hamlets Council, the Environment Agency and the Canal & River Trust, so the report reflects what those bodies actually need to see before granting approval.

Whatever stage a Hackney Wick scheme has reached — from an early feasibility check on a Fish Island warehouse conversion to a full planning submission on a Queen Elizabeth Olympic Park fringe site — our flood risk consultants can advise on what is needed and provide a fixed-fee quote within 60 minutes.

Flood risk assessments for every situation in Hackney Wick

People come to us for a flood risk assessment in Hackney Wick for planning permission, to buy or sell a property, to satisfy a mortgage lender or insurer, to achieve a BREEAM rating, and to design the surface-water drainage for a new scheme. We prepare the right assessment for each of those situations, always keeping a flood risk assessment, a sequential or exception test and a drainage strategy as separate, distinct pieces of work.

• Flood risk assessment for planning. The core report submitted with a planning application, assessing every source of flooding and showing a scheme stays safe for its lifetime, including the residual flood risk that remains once defences are taken into account.
• Flood risk survey for property purchase. An independent, site-specific assessment for homebuyers, solicitors and lenders during conveyancing.
• Flood risk assessment for insurance. Property-specific evidence for insurers, brokers and underwriters where cover or premiums are in question.
• Flood risk assessment for BREEAM. Structured to support BREEAM Pol 03 flood and surface water management credits.
• Sequential and exception test reports. A separate, locational report addressing whether a Hackney Wick site is an appropriate place for the proposed development.
• Surface-water drainage strategy (SuDS). Given CDA1, the great majority of Hackney Wick schemes need to show where their surface water goes, alongside discharge of drainage conditions and preliminary drainage design at earlier stages.
• Groundwater. Assessed as a source within every flood risk assessment here, given the site's alluvium and river terrace geology, rather than as a separate report.
• Flood modelling. Detailed hydraulic modelling where standard mapping is not sufficient to define flood levels around the Bow Back Rivers network.

Local flood risk management and emergency contacts in Hackney Wick

A number of official bodies manage flood risk in and around Hackney Wick, and knowing which one covers which source of flooding matters for both planning applications and reporting an incident.

• Sign up for flood warnings. Register for free Environment Agency flood warnings covering the Lower River Lee at Hackney and Walthamstow flood warning area, which includes Lea Bridge, Hackney Marsh and Hackney Wick.
• Check current conditions. Use Unda's free Flood Risk Map and Live River Levels Map for an indicative, first-look view of conditions around a Hackney Wick postcode.
• Check ground conditions. Given the alluvium and Hackney Gravel beneath the area, Unda's free Geology & Ground Conditions Checker gives an early read on whether infiltration drainage is likely to work before a trial pit is dug.
• Size a drainage scheme. Once ground conditions are known, Unda's free Drainage Calculators and BRE 365 Infiltration Rate Calculator support an early, defensible first pass at sizing.
• Riparian responsibilities. Owners of land next to the Lee Navigation and the Bow Back Rivers carry riparian ownership duties that can affect how a site is assessed and managed.

Flood risk assessment in Hackney Wick: frequently asked questions