Flood Risk Assessment in Rochester

Rochester stands on the tidal reach of the River Medway, a few miles up from where the estuary opens into the Thames. A flood risk assessment in Rochester has to treat the Medway as what it is here — a tidal watercourse that can carry a North Sea storm surge upstream into the town in a matter of hours, as it did in 1953 — rather than as an ordinary inland river.

We prepare flood risk assessments in Rochester for planning applications, property purchase, mortgage and insurance, and BREEAM, alongside sequential and exception tests and surface-water drainage strategies (SuDS). Architects, planning consultants, developers, landowners, home buyers and businesses come to us for a site read that holds up with Medway Council and the Environment Agency, whether the site sits on the Rochester Riverside regeneration land, in the historic centre around the High Street and cathedral precinct, or further out towards Borstal and Wainscott. We work the same way across the rest of Kent, including the neighbouring Medway towns of Gillingham, upstream at Maidstone, and further down the estuary at the Isle of Sheppey.

If you need a quote or want to talk a site through, contact one of our experienced flood risk consultants on 01293 214444.

During the East Coast flood of the night of 31 January to 1 February 1953, the tidal surge pushed so far up the Medway estuary that water reached 4.85 metres above Ordnance Datum at Rochester Bridge, flooding the High Street area and the riverside factories and schools around it — a benchmark Medway Council still uses in its flood risk assessments today.

Flood risk assessment in Rochester at a glance

• The Medway is tidal here. Rochester sits on the tidal Medway estuary, so river flood risk behaves like coastal flooding, not upstream river flooding, and is assessed differently in a flood risk assessment.
• Water reached 4.85m above Ordnance Datum at Rochester Bridge in 1953. Medway Council's own Strategic Flood Risk Assessment also records tidal flood events in 1927, 1949, 1960 and 1965, and a flood wall breach forced evacuations at nearby Canal Road, Strood, in December 2013.
• Medway Council is the Lead Local Flood Authority. It leads on surface water, groundwater and ordinary watercourses and is also the local planning authority; the Environment Agency leads on the tidal Medway itself.
• Major regeneration sits on the floodplain. The Rochester Riverside scheme, around 1,400 new homes, was engineered and elevated above flood levels before building began — the kind of mitigation a flood risk assessment has to justify and prove.

Check flood risk anywhere around Rochester

Rochester and the rest of the Medway unitary authority area are outlined below. Screen any postcode against Environment Agency data for rivers and sea, surface water and the planning flood zones, with a climate outlook to 2125. It is an indicative first pass, not a substitute for a site-specific flood risk assessment in Rochester.

A history of flooding in Rochester

Rochester's worst flood in living memory came from the sea, not the sky. On the night of 31 January to 1 February 1953, a storm surge in the North Sea combined with a high spring tide and pushed water up the Medway estuary, flooding low-lying parts of Rochester and Strood and reaching a recorded 4.85 metres above Ordnance Datum at Rochester Bridge.

• 1953 — the East Coast flood. The Medway Towns "escaped fairly lightly" compared with the rest of Kent, but low-lying Rochester and Strood flooded badly. In Rochester, the Style and Winch mineral water factory at Acorn Wharf and the Meux brewery at Old Foundry Wharf flooded; the Rochester Math School's cricket field and the old swimming baths on the Esplanade went under water; the Casino ice-skating rink and classrooms at St Nicholas Girls School in Corporation Street flooded too. In neighbouring Strood, Canal Road and the High Street were soon under water, along with the Winget factory in Commercial Road. (Source: KentOnline)
• Earlier and later tidal surges. Medway Council's own Strategic Flood Risk Assessment records further historical tidal flood events on the Medway in 1927, 1949, 1960 and 1965, each with its own recorded water level.
• December 2013. Around 300 homes across Medway were told to evacuate late at night after a flood wall was reported breached at Canal Road, Strood, with a rest centre opened at Strood Leisure Centre. Deteriorating weather into January and February 2014 triggered a further multi-agency response and unusually high groundwater levels across the wider area.

The mechanics behind all of this are the same North Sea storm-surge process that has repeatedly threatened London further downstream; our note on the Thames Barrier and tidal surges sets out how a surge builds and travels up an estuary like the Medway, and our piece on sea level rise and coastal flooding explains why events like 1953 are expected to become more frequent, not less, over a development's lifetime.

Ground that has flooded once tends to flood again: the 1953 surge line at Rochester Bridge and the 2013 breach at Canal Road, Strood, both sit close to land that is now being redeveloped, which is exactly why a robust flood risk assessment treats this recorded history as evidence, not background colour.

Flood risk in Rochester: the tidal Medway, surface water and groundwater

Three sources matter for a flood risk assessment in Rochester: the tidal Medway itself, surface water that overwhelms drains in the older parts of the town, and groundwater rising through the chalk and river-terrace deposits that underlie much of Medway. Each behaves differently, and each needs its own evidence in the report.

• Fluvial and tidal modelling. The Flood Map for this stretch of the Medway was derived from detailed river modelling completed by JBA Consulting in 2015, mapping the natural floodplain for river and tidal flood risk.
• Ordinary watercourses. Responsibility for smaller ditches and watercourses in parts of the Medway catchment sits with Internal Drainage Boards — the Upper Medway, Lower Medway and North Kent Marshes boards — alongside Medway Council's role as Lead Local Flood Authority.
• Groundwater isn't a separate report. See our note on groundwater flooding — it's a source every groundwater flood risk assessment considers within the wider report, not a different kind of flood risk assessment.
• Flood zones. The Environment Agency's Flood Map for Planning shows Flood Zones 2 and 3 along this stretch of the estuary; our guide to Flood Zones 1, 2 and 3 explains what each means for a development.

Planning policy and Medway Council as your Lead Local Flood Authority

Two authorities set the rules for development in Rochester. The Environment Agency leads on the tidal Medway itself; Medway Council, as Lead Local Flood Authority, leads on surface water, groundwater and ordinary watercourses, and is also the local planning authority that will determine your application.

Medway's Local Flood Risk Management Strategy (2023–2028) records the area as being at high risk of river, coastal and surface flooding, and it has suffered several major and minor floods since the previous strategy. Its companion Level 2 Strategic Flood Risk Assessment uses detailed hydraulic modelling of the Medway together with LiDAR ground-level data — including the 4.85m AOD level recorded at Rochester Bridge in 1953 — to set flood levels for the emerging Medway Local Plan, currently at Regulation 19 stage. That plan applies a central climate change allowance of 20% for the 2050s and 2070s, rising to an upper-end allowance of up to 45%, and expects surface water to be managed through sustainable drainage rather than discharged to the foul or combined sewer, under guidance set out in Medway's own SuDS design guidance and its recent joint agreement with Southern Water to reduce surface run-off and storm overflows across the Medway towns.

What your flood risk assessment in Rochester must show

• Risk assessed from every credible source, using the Flood Map for Planning and local Medway data.
• An appropriate location, tested against the Sequential Test where policy requires it.
• Safe for its lifetime, once the Environment Agency's climate change allowances are applied.
• No increase in flood risk elsewhere, with attenuation and, where needed, compensatory storage.
• Residual risk managed, with safe access, egress and finished floor levels above the modelled tidal levels.

Development and flood risk assessment in Rochester

Rochester's development pressure sits squarely on the floodplain, which is why flood risk assessment plays such a central role in what gets built and where.

• Rochester Riverside. Medway Council's flagship regeneration scheme, delivered with Homes England, is bringing around 1,400 new homes to brownfield land between Rochester Bridge and Doust Way. Both partners invested heavily in flood defences, remediation and engineering works, and the site was decontaminated and elevated above flood levels; one section could not be built on because of increased flood risk and was allocated as green space instead.
• Acorn Wharf. The Gas House Road site that flooded in 1953, when the Style and Winch mineral water factory stood there, is now the subject of a riverside regeneration scheme for around 132 flats, recommended for planning approval — a reminder that a formerly flooded site still needs a robust flood risk assessment before it can be redeveloped.
• The historic centre. The High Street, Corporation Street and the cathedral precinct sit close to the tidal Medway, so conversions and infill schemes there often turn on the same tidal and surface water evidence as the larger regeneration sites.

A site that flooded once, like Acorn Wharf in 1953, doesn't get a pass because it's being redeveloped. A flood risk assessment in Rochester has to show the finished scheme is safe over its whole lifetime, allowing for climate change, wherever on the estuary it sits.

How Unda helps with flood risk assessment in Rochester

We act as the accurate translation layer between your scheme and what Medway Council and the Environment Agency require. We are experts on the way flooding actually behaves in Rochester, not a generic report mill.

A flood risk assessment in Rochester from Unda assesses every credible source — the tidal Medway, surface water, groundwater, sewers and any ordinary watercourse nearby — compares modelled flood levels, including the historic 1953 benchmark at Rochester Bridge, against your proposed floor levels, sets safe access and egress, and recommends mitigation Medway Council and the Environment Agency will accept. We are a CIWEM Business Partner with chartered members, and a senior consultant signs off every report. Where the council needs it, a surface-water drainage strategy sits alongside the assessment as a separate report, so the two cases stay consistent and an objection has nowhere to land.

Flood risk assessments and related reports for every situation in Rochester

A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct reports. They often travel together in a planning submission, but they answer different questions: is the site safe, should the development be here, and where does the surface water go. We prepare all three in Rochester, alongside the right form of assessment for buyers, lenders and BREEAM.

Flood risk assessments

• Flood risk assessment for planning. The core report, site-specific and prepared to satisfy the NPPF, the Environment Agency and Medway Council. Groundwater and, where needed, flood modelling are assessed within it rather than as separate reports.
• Homebuyer and property-purchase survey. For conveyancing, where a search has flagged tidal Medway or surface water risk and you need the actual building assessed, not a broad map. Flood risk is also one of the questions buyers and lenders ask about most — see our note on how flood risk affects house prices.
• Flood risk assessment for insurance. Property-specific evidence for brokers and underwriters where premiums have risen or cover has been restricted.
• Flood risk assessment for BREEAM. Structured around BREEAM Pol 03, which is credit-driven rather than safety-driven, so a planning flood risk assessment alone rarely satisfies it.
• Groundwater flood risk. A defensible design water table for Medway-side and chalk sites and any basement, assessed as a source within the assessment, or as a standalone hydrogeological study on complex sites.

Sequential and Exception Tests

The Sequential and Exception Tests are a separate, locational report about whether a development should be in a higher-risk location at all. The Sequential Test defines an area of search, identifies reasonably available lower-risk sites and justifies the proposed site; the Exception Test is the second gate where development still needs to proceed. This is a live policy area in Kent specifically — our note on the Faversham appeal, on the Medway Estuary and Swale downstream of Rochester, shows how an Inspector has recently approached the test on this same estuary system.

Drainage strategy and SuDS

• Sustainable drainage strategy (SuDS). Surface-water engineering — calculates existing versus proposed runoff and proposes SuDS to meet Medway Council's discharge standards.
• Preliminary drainage design. The early, outline read that flags infiltration issues before they affect layout and land value.
• Discharge of drainage conditions. The detailed stage to discharge a pre-commencement or pre-occupation drainage condition.
• Flood modelling. 1D and 2D hydraulic modelling — a technique that feeds the assessment, Sequential Test or drainage design where national mapping of the tidal Medway is not enough.

Early in a drainage strategy it helps to know whether the ground will take water: our free geology and ground conditions map and BRE 365 infiltration rate calculator give an indicative read before a trial pit, and the drainage calculators help size the scheme. You can screen a postcode on our flood risk map, and every report is overseen by a chartered flood risk consultant who stays involved past the report to answer objections.

Rochester flood resources and contacts

The most reliable Rochester flood information comes from the lead authorities. For an immediate threat to life during a flood, always call 999; for a power cut during flooding, call 105.

• Check for flooding in Rochester. Live Environment Agency warnings at flood-warning-information.service.gov.uk; sign up for flood warnings or call Floodline on 0345 988 1188.
• Medway Council flood and water management. Lead Local Flood Authority guidance and reporting at medway.gov.uk, including how to report flooding.
• Kent and Medway Resilience Forum. Multi-agency flooding guidance at kentprepared.org.uk.
• Live river levels. Whether the Medway is running high right now via our live river levels map.

For flooding from a blocked or burst sewer, contact Southern Water directly. For broader policy context, our notes on the Environment Agency's planning role and on tidal (sea) flooding are a good starting point.

Flood risk assessment in Rochester: frequently asked questions