Flood Risk Assessment in Bermondsey

A flood risk assessment in Bermondsey is mostly about a river wall and what lies behind it. The tidal Thames runs along the north of the district from Tower Bridge past St Saviour's Dock to Bermondsey Wall. South of the wall the land falls towards a low basin that Southwark's flood study puts close to sea level. We prepare flood risk assessments here for planning applications, house purchases, mortgages and insurance, together with sequential and exception tests and surface water drainage strategies.

On this page Bermondsey means three Southwark wards. London Bridge and West Bermondsey takes in Bermondsey Street, Tower Bridge Road and the streets west to London Bridge station. North Bermondsey runs from Shad Thames, Dockhead and Jacob's Island along the river and Jamaica Road, and South Bermondsey covers the Blue, Bermondsey Spa and Southwark Park Road. That is the eastern end of the SE1 postcode district and the western end of SE16. Rotherhithe, Canada Water and Southwark Park lie east of the outline and the Old Kent Road ward to the south; the same council and flood evidence apply there, but they are not drawn here.

Southwark's own flood study models a breach of the river wall at Butlers Wharf in Shad Thames. On the Biscuit Factory and Chambers Wharf housing sites, it rates the hazard from a breach as a danger to most or all people.

To talk through a site with one of our flood risk consultants, call 01293 214444 or email enquiries@unda.co.uk.

Is Bermondsey really the place most at risk of being abandoned to flooding?

No flood authority has said so. The claim came from October 2025 press coverage of an insurance industry analysis by Aviva, when Time Out and Southwark News ran headlines naming Bermondsey as the area most at risk of being abandoned to flooding. Aviva's own briefing is narrower, and it never uses the word.

• What Aviva measured. Its Building Future Communities constituency statistics apply the Environment Agency's NaFRA2 projections for 2050 to Ordnance Survey address data. Bermondsey and Old Southwark comes first in England for the share of properties with river and coastal flood risk in 2050: 90.4%, with the number at risk rising from 46,940 in 2025 to 53,864.
• The area is bigger than Bermondsey. The constituency runs from the South Bank to Rotherhithe, so the figure also covers Borough, Bankside and Rotherhithe.
• The headlines disagreed with each other. Southwark News gave a 90% rise over 15 years in its opening line and 92% over 25 years further down. Time Out printed 92% in one article and 90.4% in another. Aviva's table gives 90.4% as a share of properties, not as an increase.
• No source says the district will be given up. The briefing says nothing about abandonment, uninsurability or retreat. Its figure shows how much of northern Southwark relies on the Thames defences, which planning already assumes: the Flood Map for Planning ignores the defences and places most of the north of the borough in Flood Zone 3.

A purchase or a planning application turns instead on how one building would fare if the wall were overtopped or breached, and whether a scheme can show the council it would stay safe. Our articles on Aviva's findings at six famous landmarks and on what NaFRA2 found explain the national data. Whether homes could become uninsurable is covered in a separate article.

Behind the river wall: the breach case on the Bermondsey frontage

The Thames Barrier and the river walls protect the whole borough against a combined tide and river flood with about a 1-in-1,000 chance in any year, according to the 2017 Southwark Strategic Flood Risk Assessment. A Bermondsey scheme has to answer the residual risk instead. That means water coming over the wall in a bigger event, or through it where a section fails.

• The wall stands higher than the streets behind it. Ground beside the river is around 4 to 5 m AOD and falls south into a basin the SFRA puts close to 0 m AOD east of Walworth. Water that got past the wall would find lower ground inland instead of draining back to the river.
• Three modelled breaches face this frontage. The Environment Agency's 2014 breach model, used in the SFRA, tests 20 m breaches at the Tower Bridge abutment, at Butlers Wharf and at Farrands Wharf on Bermondsey Wall. Each is run for present-day, 2065 and 2100 water levels, and our guide to residual flood risk explains how that evidence is used on a site.
• The gauge across the river. The Environment Agency's Tower Pier gauge, across the river by the Tower of London, has recorded a highest level of 4.81 m against a statutory defence level of 5.28 m, so even the biggest tide on its record stopped less than half a metre below the defence level.
• The walls are due to be raised. Southwark Plan policy P68 notes the Thames Estuary 2100 expectation that the wall from Bankside to Rotherhithe goes up by 0.5 m by 2065 and another 0.5 m by 2100. Bermondsey sits in the Wandsworth to Deptford policy unit under policy P5, where defence owners should adapt and raise the defences by 2050. Our article on the Thames Barrier looks at the barrier's own future.
• Space has to be left for that work. P68 sets riverside development back 10 m from the defence wall, and the SFRA asks for a 16 m buffer in tidal areas. Part of a frontage layout is fixed by the wall before any flood level is calculated.

Check a postcode from Shad Thames to the Blue

Enter a Bermondsey postcode below to screen it against Environment Agency data for rivers and the sea, surface water and reservoirs, or open our full flood risk map for anywhere in England. The coral line follows the three wards: Rotherhithe and Southwark Park sit beyond its eastern edge, the Old Kent Road ward beyond its southern edge. The flood zone shown ignores the river wall. The government's long-term flood risk service allows for it, which is why the same Bermondsey street can look safe on one map and high risk on the other (how the two maps differ).

Floods in Bermondsey, from 1928 to today's warnings

Bermondsey's tidal record is short. The defences have mostly held, but not always. The dates below come from the old borough's own health report and the flood history in the Southwark SFRA.

1. 7 January 1928. After a high tide and strong winds the river overflowed its banks. The Metropolitan Borough of Bermondsey, which then included Rotherhithe, counted seventy streets, 1,213 houses and 1,285 families affected, with water four feet deep around Silver Street. Nobody in the borough died. Its medical officer's report for 1928 records £22,619 raised in relief funds and grants.
2. 10 December 2005. The Thames Barrier was not closed, and residents near the floodgates had little warning. Water came over the Southwark frontage and into some basements to a depth of 4 to 6 inches, the SFRA records.
3. October 2006 to March 2007. A blocked road drain flooded a basement on Tooley Street and a blocked gully left water standing on Tower Bridge Road. Surface water also flooded Jamaica Road outside Bermondsey station; all three are logged in the council's surface water plan data.

To see whether a flood warning is in force in Bermondsey today, check the two Environment Agency tidal warning areas that cover the outline. Tidal Thames from Rotherhithe Station to London Bridge names north Bermondsey and London Bridge; Tidal Thames at South Bermondsey covers the land between the Old Kent Road and the railway. The Tower Pier gauge and the other tidal stations on the Thames are on our live river levels map.

Surface water, sewers, chalk groundwater and the Neckinger

Most flooding a Bermondsey property sees comes from rain, not the river. Southwark's Local Flood Risk Management Strategy 2023 to 2029 names surface water as the flooding residents are most likely to experience, and in Bermondsey two things decide how it behaves: the river gravels have no London Clay beneath them, and the combined sewers are short of capacity in a heavy storm.

Chambers Wharf, beside Chambers Street, was one of the Tideway Tunnel's main sites. Its 60 m shaft is where tunnel drives from the west and from the east met, and the site is now allocated for at least 587 homes. Our article on London's super sewer explains what the tunnel intercepts. Capacity for a new sewer connection is still a question for Thames Water at application stage.

New homes on defended land: the Biscuit Factory, Chambers Wharf and the Old Kent Road sites

The Southwark Plan expects Bermondsey's allocated sites to deliver about 2,300 homes and 22,000 m² of workspace, and the borough's own evidence puts them on defended Flood Zone 3 land. Southwark's Level 2 SFRA, updated in July 2020 for the plan's examination, assessed each allocation.

On every one of these sites the SFRA asks for the same things. Floors go at least 300 mm above the modelled 2100 breach level, and there are no basement dwellings. Safe access should run above the breach level towards Flood Zone 1; where it cannot, residents need a communal refuge inside the building, reached by internal stairs. Surface water is held to greenfield rates because the sewers are short of capacity. The wider Old Kent Road Opportunity Area, which reaches into West and South Bermondsey, has London Plan capacity for 12,000 homes and 5,000 jobs.

Policy P68, the 2017 SFRA and Southwark's drainage rules

Southwark Council is both the local planning authority and the Lead Local Flood Authority, so one council decides the application and comments on its drainage, while advice on the river wall and tidal flooding comes from the Environment Agency. The local test is policy P68, Reducing flood risk, in the Southwark Plan 2022, adopted on 23 February 2022 and running to 2036:

• No added risk. Development must not increase flood risk on or off the site, and must be designed to be safe and resilient to flooding.
• Floors 300 mm up. Finished floor levels must sit at least 300 mm above the predicted maximum water level on a site at risk. In Bermondsey that level is normally the 2100 breach level from the SFRA.
• Greenfield runoff for major schemes. Major development must cut surface water runoff to greenfield rates through SuDS. The hierarchy starts with storing rainwater for reuse and ends with the combined sewer, and garden paving must be permeable.
• A 10 m setback from the river. Sites on or next to the Thames frontage are set back 10 m from the defence wall, and the strip has to work as flood defence and public space at once.

The evidence behind P68 is the Southwark Strategic Flood Risk Assessment, produced in 2016 and adopted in March 2017. The council re-uploaded it to its new website in 2024, which is why some search results call it a 2024 document; our explainer covers what an SFRA is for. Southwark's developers' guide to surface water management limits discharge to the greenfield rate unless its flood risk team agrees another rate before submission. It also expects an assessment for any site in or near a Critical Drainage Area, and one of those covers the streets around London Bridge station.

London-wide, the London Plan 2021 still governs through policy SI 12 on flood risk management and SI 13 on sustainable drainage, and major schemes submit the SuDS proforma with their drainage strategy. A draft replacement plan was out for consultation from 16 July to 15 October 2026 and is not expected to be adopted before 2028, so applications decided before then are judged against the 2021 policies. Nationally, the flood tests sit in chapter 18 of the August 2026 NPPF. F4 decides when an assessment is required, F5 and F6 cover the sequential and exception tests, and F8 asks every development to meet the 2025 National Standards for sustainable drainage.

From a loft flat to a riverside block: when a flood risk assessment in Bermondsey is needed

Nearly every planning application in the three wards needs one, because most of the district lies in Flood Zone 3 behind the defences. The table shows how the common Bermondsey cases fall.

Where housing is proposed in Flood Zone 3, Southwark also looks for the sequential test. The Level 2 SFRA found the exception test necessary on every Bermondsey allocation it assessed.

Reports we prepare for Bermondsey, from Tower Bridge to the Blue

Which report a site needs depends on where it sits between the wall and the basin, and on who is asking. Every report is signed off by a senior consultant; the consultants who write them are chartered, and Unda is a CIWEM Business Partner.

• Homes and offices in the defended floodplain. Applications across the three wards need a flood risk assessment for planning that answers policy P68 and the SFRA's breach rules.
• Tide, rain, sewers and chalk together. On a single plot, a flood risk assessment weighs the breach case against surface water, the combined sewer and groundwater in the Chalk and Thanet Sand.
• Before exchange in Shad Thames or near the Blue. Warehouse flats on the river and terraces off Southwark Park Road raise lender questions that a flood risk survey for property purchase settles.
• Housing in Flood Zone 3. New homes on most Bermondsey sites face the sequential and exception test, as the Level 2 SFRA found at the Biscuit Factory, Tower Workshops and Chambers Wharf.
• Runoff from new building. Policy P68 asks major schemes for greenfield runoff, and our drainage strategy work shows Southwark Council how a scheme meets it.
• Clay, chalk or a crowded sewer. Infiltration is heavily constrained at the Biscuit Factory and possible elsewhere, so a surface water drainage strategy here starts with ground testing and Southwark's greenfield rate.
• After consent. Where Southwark Council attaches a drainage condition to a permission, we prepare the evidence for the discharge of drainage conditions.
• The depth a breach would bring. Where the 2014 breach points do not represent a site, flood modelling can set the 2100 breach level that floor heights depend on.
• A way out, or a refuge. The SFRA asks housing schemes for safe access above the breach level or a communal refuge, set out in a flood warning and evacuation plan tied to the Rotherhithe Station to London Bridge warning area.
• No London Clay cap. The Chalk and Thanet Sand lie close beneath the gravels in Bermondsey, so basement and soakaway schemes benefit from a groundwater flood risk assessment.
• Cover and premiums. Aviva ranked Bermondsey and Old Southwark first in England for river and coastal flood exposure in 2050, and a flood risk assessment for insurance gives an underwriter evidence about the building itself.
• Buying regeneration land. Bricklayers Arms, Crimscott Street and Mandela Way all need the exception test, so flood risk due diligence belongs before a land deal is struck.
• Workshops under the railway arches. The Southwark Plan names Bermondsey Street, Maltby Street and the railway viaducts as employment clusters, and a business continuity flood assessment helps occupiers there plan for a breach or a surcharged sewer.
• Sewer capacity. Southwark's flood strategy describes Thames Water's combined sewer around London Bridge as at capacity, so a foul drainage strategy should confirm a connection early.
• New workspace. The Bermondsey allocations are expected to add about 22,000 m² of workspace, where a BREEAM flood risk assessment supports the Pol 03 credits.

Warnings, reporting and the bodies responsible in Bermondsey

Call 999 when floodwater threatens anyone's life, and 105 for a power cut. Outside an emergency, responsibility divides between the bodies below.

Downstream on the same bank, Rotherhithe shares Bermondsey's TE2100 policy unit, and Deptford lies beyond it at the mouth of the Ravensbourne. Wapping faces Bermondsey across the river, the Isle of Dogs fills the next bend downstream, and Vauxhall is upstream on the south bank. The river itself has its own River Thames page, and every place we cover is listed on our areas page.

Bermondsey flooding: answers for buyers, landlords and developers

From Shad Thames to South Bermondsey, Unda Consulting Limited prepares flood risk assessments, sequential and exception tests and drainage strategies for homes, workspaces and development land. To discuss a site in Bermondsey, Dockhead or around Bermondsey Street, call 01293 214444 or email enquiries@unda.co.uk.