Flood risk assessments for Tower Hamlets planning applications
Tower Hamlets' validation page asks for a flood risk assessment on applications in Environment Agency Flood Zone 2 or 3 that involve a new build or a basement or ground floor extension. We write it for a fixed £395, including the breach risk behind the Thames defences that the borough's own flood strategy describes.
Fixed fee from £395 · all prices
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What the Tower Hamlets validation page says
The council's flood risk assessment validation page says an assessment is "Required for all applications in Environment Agency Flood Zone 2, or 3" relating to new builds and basement or ground floor extensions. It asks that the assessment identify and assess the risks of all forms of flooding to and from the development, and that it include the design of surface water management systems including Sustainable Drainage Systems.
The page shows no version number or date when we read it on 29 October 2026, and it cites policies D.OWS4 and D.ES5 of the Local Plan 2031 (January 2020). It does not name an upper-floor-only extension, so if that is your project in Zone 2 or 3, ask the planning officer before you pay for a report and we will tell you what the Environment Agency's standing advice says.
Flood Risk Assessments in Tower Hamlets
from £395
Every price is the full fixed fee you pay. No VAT is charged. Council application fees are paid to the council separately.
What you get
- Your address checked on the Environment Agency flood map for planning
- A written assessment in the structure Tower Hamlets asks for
- Tidal breach risk behind the Thames defences set out for your site
- Floor levels and a safe way out tied to your drawings
- A short surface water and SuDS note for the council
- The assessment as a PDF for the planning application
- Check the flood map
Flood zone and surface water risk for your exact address, before any fee is spent.
- Match the council's page
Is your scheme a new build, or a basement or ground floor extension in Zone 2 or 3?
- Test the breach scenario
Residual risk if the tidal defences were breached, set against your floor levels.
- Design the response
Floor levels, resilience, safe access and a surface water drainage note.
- Write and submit
A concise PDF for the planning officer, referenced to your drawings.
Why the Thames defences do not end the question
Tower Hamlets' Local Flood Risk Management Strategy says the Thames Barrier and the tidal defence walls, embankments and gates on the Thames and the River Lee give the borough protection of 1 in 1000, a 0.1% chance in any year. It then adds that there is a residual risk of flooding from breaches of the tidal defences, caused by human interference or defence failure, and that the Environment Agency has modelled that risk.
That is why a site can sit in a flood zone on the map and still be defended. An assessment does not argue the flood zone away. It states what the breach scenario would do to your ground floor, sets floor levels and resilience against it, and shows how occupants leave safely.
For a simple extension the Environment Agency's guidance says you may be able to write the assessment yourself, and a minor extension is a household or non-domestic extension of no more than 250 square metres.
Critical Drainage Areas and surface water
The same strategy says Critical Drainage Areas were identified from a surface water study concluded in 2017, as places where heavy rain is more likely to flood homes and businesses. Much of the borough is paved and drains to a combined sewer system built in the Victorian period, whose capacity for rainwater is limited.
So a site far from the river can still need drainage thought. The validation page asks for the design of surface water management systems, and we put a short sustainable drainage note inside the assessment. Where the council wants a fuller strategy, our SuDS drainage statement is a separate fixed-fee service, and the assessment with a statement together is £625.
The River Lee and Hackney Wick
Most of the borough's flood question is tidal, but the strategy notes some remaining fluvial risk from the River Lee in the Hackney Wick area, around White Post Lane and Dace Road. If your address is there, the assessment looks at river flooding as well as the Thames breach scenario, and checks whether the site is within 20 metres of a main river or flood defence as the Environment Agency's guidance asks.
Basements and ground floor extensions
Tower Hamlets names basement and ground floor extensions in Zone 2 or 3 specifically, and that is where water arrives from several directions at once. Floor levels, a safe route up and out, and drainage that cannot back up all have to agree with your drawings. If you are planning one, our basement conversion drawings are prepared with the assessment in mind.
For a simple extension the Environment Agency's guidance says you may be able to write the assessment yourself, and a minor extension is a household or non-domestic extension of no more than 250 square metres. We say so honestly: if the standing advice covers your scheme, you may not need us.
Fee, and what happens next
The fixed fee is £395, the total you pay, and no VAT is charged. It covers the flood map check, the written assessment and a drainage note for a house, extension or small conversion. For a major scheme or one needing bespoke river modelling a specialist hydrologist is brought in, and we say so and quote them separately before you commit.
Send the address and a line on what you want to build. If the map shows Flood Zone 1 with no surface water risk, we tell you so and you pay nothing.
Sources
Every figure on this page, where it comes from and a link to the original.
| Figure | Source | Link |
|---|---|---|
| Flood Zone 2, or 3 | Tower Hamlets Council, Flood Risk Assessment (local validation list page; no version date shown, read 29 Oct 2026) (source wording: "Required for all applications in Environment Agency Flood Zone 2, or 3" "relating to new builds and basement or ground floor extensions.") | www.towerhamlets.gov.uk |
| surface water management systems | Tower Hamlets Council, Flood Risk Assessment validation page (source wording: "The FRA should include the design of surface water management systems including Sustainable Drainage Systems (SUDs)") | www.towerhamlets.gov.uk |
| D.OWS4 and D.ES5 | Tower Hamlets Council, Flood Risk Assessment validation page cites (source wording: "Policies D.OWS4, D.ES5 of the LBTH Local Plan 2031 (January 2020)") | www.towerhamlets.gov.uk |
| 1 in 1000 | Tower Hamlets Local Flood Risk Management Strategy (revision history to v1.3, 2017): Thames Barrier and associated tidal defences provide (source wording: "protection of 1 in 1000 (0.1% chance in any year)") | www.towerhamlets.gov.uk |
| residual risk | Tower Hamlets Local Flood Risk Management Strategy (source wording: "There is a residual risk of flooding from breaches of the tidal defences caused by human interference or through defence failure. The Environment Agency has undertaken breach modelling which maps this risk.") | www.towerhamlets.gov.uk |
| Critical Drainage Areas | Tower Hamlets Local Flood Risk Management Strategy (source wording: "The CDAs have been identified as result of a surface water study, concluded in 2017"; CDA = Critical Drainage Areas) | www.towerhamlets.gov.uk |
| White Post Lane and Dace Road | Tower Hamlets Local Flood Risk Management Strategy (source wording: "There remains some risk of fluvial flooding from the River Lee in the Hackney Wick area of Tower Hamlets around White Post Lane and Dace Road.") | www.towerhamlets.gov.uk |
| 250 square metres | Environment Agency, Flood risk assessments: applying for planning permission (source wording: "A minor extension is a household or non-domestic extension with a floor space of no more than 250 square metres") | www.gov.uk |
The full guide lives on our sister site
We still prepare this for a fixed £395. The detailed guide to it is on fixedfeeplans.co.uk, part of the same practice.
Questions people ask
Does every Tower Hamlets application need a flood risk assessment?
My house is protected by the Thames Barrier. Why is it in a flood zone?
I live near Hackney Wick. Is that different?
Can I write it myself for a small extension?
Will the assessment guarantee permission?
Photographs: Christopher Hilton (CC BY-SA 2.0).
