Flood Risk Assessment in Stockport

A flood risk assessment in Stockport has to read three rivers and the drains together. The Goyt and the Tame meet in the town centre to form the Mersey, and the council treats the whole borough as a critical drainage area because its surface water and sewer flooding is among the worst in the North West. Our consultants prepare flood risk assessments in Stockport for planning, property purchase, mortgage and insurance, along with sequential and exception tests and surface water drainage strategies.

On this page Stockport means the town's built-up area: the centre and Portwood, Lancashire Hill and Brinnington, the Heatons (Heaton Norris, Heaton Chapel, Heaton Moor and Heaton Mersey), Edgeley, Cale Green, Shaw Heath, Davenport, Great Moor, Offerton and Stepping Hill, in the SK1, SK2, SK3 and SK4 postcode districts. Reddish, Cheadle, Bramhall, Hazel Grove and Marple are separate built-up areas, but Stockport Council decides planning applications and acts as Lead Local Flood Authority across all of them, so the rules below apply there too.

On 1 January 2025 the Mersey at Brinksway reached 5.03 m, the highest level ever recorded there, and fire crews used boats to take about 400 residents out of Meadow Mill in Portwood after the Tame overtopped its banks.

To talk through a Stockport site, ring our flood risk consultants on 01293 214444 or email enquiries@unda.co.uk.

Where the Goyt and Tame become the Mersey: Stockport's rivers

Two main rivers become a third in the town. The Goyt arrives from the south-east past Bredbury and Offerton, the Tame from the north through Reddish Vale, and the two join at Portwood to form the River Mersey. From there the Mersey runs west beneath the town centre and Merseyway, then out past Brinksway and Heaton Mersey. Both feeders drain steep Pennine catchments, which is why they rise fast after heavy rain in the hills. A fourth main river, the Hempshaw Brook, runs for about a kilometre from south of the centre past Hillgate, much of it in culvert, to join the Mersey at Great Underbank.

Through the town centre, the Mersey's protection is mostly private high ground with some walls, and the Environment Agency holds no record of its condition. The 2026 SFRA adds that defence assets across the borough are nearing the end of their design life, and the Flood Map for Planning ignores them anyway. Any Stockport site behind a wall or bank should be assessed as if it could fail; our note on residual flood risk explains what that means for floor levels and a way out.

Check a Stockport postcode, from Heaton Chapel to Stepping Hill

Enter a Stockport postcode below to see the Environment Agency's river, surface water and reservoir data, or open our full flood risk map for anywhere in England. The coral line is the 2022 ONS built-up area for Stockport, about 24 square kilometres, from the Heatons in the north-west to Stepping Hill in the south-east. On most streets the surface water layer will say more than the river layer, and our guide to flood zones 1, 2 and 3 sets out what each layer measures.

Stockport flooding from 2016 to New Year's Day 2025

Stockport floods most often when intense rain overwhelms its drains and sewers, and worst when the same rain fills the rivers. The council has investigated each major event since 2016 under Section 19 of the Flood and Water Management Act, and some places, Meadow Mill and the Brinksway gauge among them, appear more than once.

1. 8 to 16 June 2016. Prolonged, intense rain flooded homes across the borough from several sources at once, the council's investigation found: surface water, sewers, rivers and groundwater.
2. 13 September 2016. A downpour after a dry spell overloaded the drains, and more than 650 properties suffered sewer flooding, with the Heatons, Reddish, Davenport, Cale Green and Stepping Hill among the worst hit. Blocked screens on the Hempshaw Brook culverts flooded commercial premises in the town centre the same month.
3. 28 to 31 July 2019. Five days of rain, 200 mm of it at the Cat and Fiddle gauge in the hills to the south-east, left 776 properties flooded across the borough and closed the A555.
4. 20 February 2022. During Storms Eunice and Franklin, heavy rain in the Goyt catchment backed the Tame up at the confluence and flooded the Meadow Mill area. The Mersey at Brinksway reached 4.342 m, then its highest on record.
5. 31 December 2024 to 1 January 2025. The Cheadle rain gauge took 81.8 mm in just over half a day, and Stockport had the heaviest rain in Greater Manchester that night. The Tame flooded the ground floors at Meadow Mill, the Mersey rose to 5.032 m at Brinksway and flooded industrial units off Ford Street, and the council counted about 639 properties affected, 114 internally, with more than 400 evacuated.

The council's report on the 2025 flood puts the main cause down to record river levels, which stopped surface water and sewer outfalls from discharging, rather than blocked gullies. That matters for any new outfall to the Goyt, Tame or Mersey: it may be under water just when the site needs it. You can follow the Environment Agency gauges at Brinksway, Portwood and Lower Bredbury on our live river levels map, and our explainer on Section 19 flood investigations covers how these reports come about.

Under Merseyway: what the town centre flood study found

Stockport Council plans around 8,000 new homes in the town centre, through its regeneration frameworks for Town Centre West and Town Centre East, so the 2024 Level 2 SFRA for the centre is the study most applicants there will meet. Prepared by Jacobs, it divides the centre into eleven assessment areas and rates river flooding a high risk in six of them.

• Merseyway and Great Underbank. In a 1-in-1,000-year flood the Mersey overtops at a low point of 39.83 m AOD just upstream of its culverted section, and water runs west into the Merseyway shopping centre, Great Underbank, Bridgefield Street and Prince's Street, up to 2.5 m deep. The study rates that flow a danger to most people.
• Ponding in the precinct. Surface water gathers at low spots in the shopping centre, up to 600 mm deep near Prince's Street in a 1-in-30-year storm and 900 mm in a 1-in-100-year storm.
• The Hempshaw Brook culverts. A rebuilt model of the brook tested 90% blockages at the Waterloo Road and Wellington Street culvert inlets. A blocked downstream inlet floods commercial property at Hopes Carr and flats on Manchester Road in a 1-in-20-year event.
• Groundwater may rise. Robinsons' Unicorn Brewery was licensed to pump up to 3,637 cubic metres a day from the sandstone beneath the centre, which probably held groundwater down. With brewing moving to Bredbury, the 2026 SFRA asks developers to investigate a rebound, and the council already hears of cellars flooding in Edgeley and near the Hempshaw Brook.
• The Exception Test may follow. The 2026 SFRA accepts that regeneration cannot always avoid risk. If a search of town centre sites finds nothing suitable at lower risk, the Exception Test may be needed, supported by site-level detail on depth and hazard.

For a town centre site the Level 2 study sets much of the brief. It asks site assessments to check the condition of the Mersey and Hempshaw Brook culverts and to model surface water along Great Underbank and in the shopping centre, with groundwater tested through ground investigation. Our guide to culverts, ownership and consent explains who answers for each one.

One critical drainage area: the drainage numbers Stockport sets

Every site in Stockport lies in a critical drainage area. The council's local guidance designates the whole borough because it is one of the worst places in the North West for surface water and sewer flooding, and the 2026 SFRA recommends keeping it that way. In practice small schemes face drainage tests that much of England reserves for larger ones.

• Half the runoff from brownfield land. Core Strategy policy SD-6 requires development on previously developed land to cut unattenuated runoff by at least 50%, and greenfield sites must not increase it.
• Floors above the road. Policy SIE-3 expects new buildings in a critical drainage area to have floor levels at least 300 mm above road level. Where river flooding is the issue, the council's guidance asks for floors above the 1-in-100-year flood with climate change plus 600 mm, given in metres above ordnance datum.
• Sewers already under strain. United Utilities logged 2,634 sewer flooding incidents in the borough between 2009 and 2025, 1,295 of them inside buildings. Holiday Lane in Offerton accounted for 662 before a sewer upgrade was finished in 2021.
• Paving counts. Where new hard standing needs planning permission, the Core Strategy expects it to be permeable or to drain to another form of SuDS.
• Ground that varies. The town centre, Edgeley and the north of the borough sit mainly on sandstone, while clay is more common to the south and east. Water soaks readily into the sandstone, which helps a soakaway but also feeds the groundwater that floods cellars.

Stockport Interchange shows the standard at scale. Its two-acre rooftop park sits over a blue roof designed for a 1-in-100-year storm with a 40% climate change allowance, releasing water to the Mersey at greenfield rates and keeping it out of the combined sewer. In June 2026 it was named overall winner of the susdrain SuDS Awards. For a smaller plot, our ground conditions checker gives a first view of soakaway potential, a BRE 365 infiltration test settles it, and our article on critical drainage areas compares the rules elsewhere.

Policy SD-6, the new Local Plan and the tests a Stockport scheme must pass

Applications are decided against the Stockport Core Strategy of March 2011 and the saved policies of the 2006 Unitary Development Plan Review, including EP1.7 on development and flood risk. Stockport is not part of Places for Everyone, the joint plan the other nine Greater Manchester councils adopted in 2024, so its own new Local Plan to 2042 will replace them. That plan reached its final consultation in September 2026, closing on 8 November, with submission due by the end of the year and adoption expected in winter 2027/28.

Two details in the draft plan change what an assessment has to show. The plan expects assessments to model the 41% peak river flow allowance for the Upper Mersey catchment and to draw design flood depths on the elevations and sections, and its 0.5 ha threshold brings mid-sized Flood Zone 1 schemes into scope. The council's Level 1 SFRA of July 2026, prepared by Arcadis, updates the 2019 Greater Manchester study for the whole borough and sits on the council's flood risk evidence page with the 2024 town centre Level 2 SFRA.

Stockport Council, as Lead Local Flood Authority, reviews surface water proposals and gives its drainage guidance to applicants on request. Nationally, a Stockport application sits under chapter 18 of the August 2026 NPPF, and the 2025 National Standards for sustainable drainage now set the discharge rates the draft plan points to. The Local Plan documents hold the full policy wording.

From cellars to riverside flats: when a flood risk assessment in Stockport is needed

With the whole borough a critical drainage area, far more Stockport schemes need an assessment than the flood zones alone suggest. The table is a starting point; the final answer turns on the Flood Map for Planning, the 2026 SFRA and the details of the scheme.

Conversions are common in the older parts of town: see our notes on turning a house into flats and on basement and cellar conversions in a flood zone. For the Flood Zone 1 cases, our article on surface water flooding and planning covers what councils now ask.

Reports our consultants prepare for sites from Portwood to the Heatons

The people who ask us about Stockport sites range from developers and architects to planning consultants, homeowners, buyers and businesses, and the three main reports answer different questions. The flood risk assessment shows the site is safe; the sequential test shows no lower-risk site is reasonably available; the drainage strategy shows where rain falling on the site will go. The rows below set out why each one comes up here.

• Rivers, drains and groundwater together. Where three main rivers meet over sandstone and a stretched sewer network, a flood risk assessment has to weigh river levels, surface water, sewer surcharge and groundwater side by side.
• Applications under SD-6 and SIE-3. From a Merseyway conversion to a house in Offerton, a flood risk assessment for planning gives the council the evidence its adopted policies and the 2026 SFRA call for.
• Before exchange in the SK1 to SK4 districts. Conveyancing searches often flag surface water around the Heatons, Davenport and Edgeley; a flood risk survey for property purchase looks at the house itself, its floor levels and its cellar.
• Regeneration on riverside land. With thousands of homes planned in the centre and parts of it in Flood Zones 2 and 3, many schemes need a sequential and exception test built on an area of search the council will accept.
• SuDS on minor schemes too. Draft policy INF 4 asks for a SuDS strategy on minor schemes as well as major ones, so a drainage strategy now forms part of most Stockport applications.
• The 50% cut on brownfield land. A surface water drainage strategy shows runoff reduced by at least half under SD-6, following the hierarchy that leaves combined sewers until last.
• After the permission. The draft plan says the council will attach conditions on surface water management to schemes; our consultants put together the details for the discharge of drainage conditions so building can start.
• Proving a site is not functional floodplain. Where no detailed model exists, the 2026 SFRA treats all of Flood Zone 3 as functional floodplain and leaves the developer to show otherwise, which flood modelling for a Stockport river site can do.
• Cellars over the sandstone. With the brewery abstraction ending and cellars already flooding in Edgeley, a town centre basement may need a groundwater flood risk assessment.
• Homes in the Goyt and Mersey warning area. Draft INF 3 expects occupants to sign up to Environment Agency warnings, and riverside schemes from Portwood to Chestergate may need a flood warning and evacuation plan.
• Streets with a flood history. On streets that flooded in 2016, 2019 or January 2025, renewal can bring awkward questions, and insurance flood risk assessments give an insurer site-specific evidence instead of a postcode band.
• Riverside businesses. Twenty commercial premises flooded at Meadow Mill in 2025 and industrial units off Ford Street went under; business continuity flood assessments set out what a tenant can move, raise or protect before the warning comes.
• Estates inside warning areas. Meadow Industrial Estate and the estates at Barton Road and Riverview lie inside Environment Agency warning areas, and a due diligence flood risk assessment gives buyers and lenders a view before they commit.
• Large schemes and sewer capacity. Draft policy INF 6 asks schemes over 150 homes or 1,000 square metres to show the wastewater capacity exists, and in a borough with a long record of sewer flooding, a foul drainage strategy is how that case is made.
• Before buying regeneration land. Much of the housing planned for Town Centre West and Town Centre East has yet to reach planning, and a flood risk feasibility study shows how many homes a riverside plot can take once floodplain and river buffers are set aside. Better to know that before money is committed.

Reporting a flood in Stockport, from the Tame to the sewers

Stockport's flooding comes from rivers, rain, sewers and the ground, and each has a different owner. Where life is at risk the number is 999; a power cut caused by flooding goes to 105.

The council publishes its flood investigation reports and its local flood risk management strategy, and our guide to sewer flooding explains who answers for which pipe. Upstream, the Goyt drains Whaley Bridge, where part of the Toddbrook Reservoir spillway collapsed in August 2019.

What Stockport buyers, owners and developers ask about flooding

To discuss a site anywhere from Heaton Mersey to Stepping Hill, call our chartered flood risk consultants on 01293 214444 or email enquiries@unda.co.uk. Unda Consulting Limited is a CIWEM Business Partner, and every report is checked and signed off by one of our senior consultants. Downstream, the Mersey runs on to Didsbury, covered on our Manchester page. Rochdale to the north and Cheshire to the south have pages of their own, and the rest are on our list of every area we cover.