Flood Risk Assessment in Sheerness

Sheerness sits at the very mouth of the River Medway, where the estuary meets the Thames and the tidal Swale channel that separates the Isle of Sheppey from the Kent mainland. Blue Town, the docks and much of Marine Town were built out onto reclaimed marsh, and a large part of the town still sits at or below the level of a spring tide, kept dry only by the sea wall and embankments that ring the shore. We prepare a flood risk assessment in Sheerness for sites across the town centre, the seafront and the port, working out exactly how the tide, the heavy clay ground and a rising sea affect a specific property, then dealing directly with the Environment Agency and Kent County Council as Lead Local Flood Authority on your behalf.

We prepare flood risk assessments in Sheerness for planning, property purchase, mortgage and insurance, and BREEAM, alongside sequential and exception tests and surface-water drainage strategies (SuDS), guiding architects, planning consultants, developers, landowners, home buyers and businesses through to a decision.

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

Sheerness is a defended town, not an undefended one, and that distinction matters more here than almost anywhere else on the Kent coast. The Environment Agency's own strategy names Sheerness as a place where the sea wall must be raised twice over the coming decades just to hold the current standard of protection, which is exactly the residual risk a credible assessment has to prove a new development can withstand.

Under the Environment Agency's Medway Estuary and Swale strategy, the sea defence protecting Sheerness is due to have its crest raised to 5.4m AOD within three years and to 6.9m AOD within fifty, simply to keep pace with the rising tide — proof that even a long-defended site here still has to demonstrate its residual flood risk today.

Flood risk assessment in Sheerness at a glance

Sheerness is shaped by the tide more than any other single factor, but it rarely acts alone. Here is the picture in brief before the detail below.

• The tide is the dominant risk. The Thames, the Medway estuary and the Swale meet at Sheerness, and much of Blue Town, the docks and the seafront lie at or below high-tide level behind engineered defences.
• Defended does not mean low risk. The Environment Agency's Flood Map for Planning is drawn as if the sea wall were not there, so a well-defended Sheerness site can still sit in Flood Zone 3 and still needs its residual risk assessed.
• One Lead Local Flood Authority, one planning authority. Kent County Council is the Lead Local Flood Authority for surface water, groundwater and ordinary watercourses; Swale Borough Council determines planning applications and holds the local flood policies.
• The port sits on reclaimed land. Sheerness Docks was built out over drained marsh and mudflat, including the Lappel Bank foreshore, so ground conditions and defended tidal risk are central to any scheme there.
• Flood Zone 1 is not a free pass. Since the 2025 Planning Practice Guidance update, surface water pooling on the town's clay ground can trigger an assessment even where the river and sea map shows Flood Zone 1.

Where flood risk comes from across Sheerness

Tidal and coastal flooding dominates Sheerness. The town is bounded by the Thames estuary to the north, the Medway estuary to the west and the tidal Swale to the south, and most of its older, low-lying ground sits behind sea walls rather than above the flood line. Surface water gathers on the heavy clay the town is built on, and the wider Swale district carries a chalk groundwater risk further inland, so a site can face more than one source at once.

Establishing which source actually governs a site — a tidal surge from the estuary, run-off pooling on clay, or the residual risk behind a defence — is the heart of a credible tidal flood risk appraisal, and it is what separates a robust assessment from a generic one.

• Tidal and coastal. The main source in Sheerness. A surge in the Thames or Medway estuary, or along the Swale, is driven by sea level and storm surge rather than rainfall, and is rising as the sea level rises.
• Surface water (pluvial). Now the most widespread flood risk in England. The clay beneath Sheerness sheds rainfall rather than absorbing it, so intense rain collects in the low points of Blue Town and Mile Town. Since the 2025 PPG update, surface water on the Flood Map for Planning can trigger an assessment even in Flood Zone 1.
• Groundwater. The chalk that underlies the wider Swale district can saturate after a wet winter and raise the water table, while the town's own clay holds water near the surface — both undermine soakaway assumptions. See groundwater flooding.
• Residual risk behind the defences. The sea wall reduces the chance of flooding; it never removes it, and a site protected today can still flood if a defence is overtopped or breached in a severe surge — see residual flood risk.

A history of flooding in Sheerness

Sheerness has flooded on the tide more than once in living memory, and each event has left a specific, well-documented account of how the water moved through the town. That detail is what a credible assessment tests a site against, not a generic reference to "coastal risk."

• 1953 — the North Sea flood. On the night of 31 January 1953 the surge that struck the whole east coast breached the defences around Sheppey. In Marine Town, residents of Unity Street and Clyde Street used rowing boats to get clear of their homes, and the rest centre at the Welfare Clinic on Invicta Road had to relocate to the Sheerness Technical Institute when power failed. More than 150 evacuees were moved on to Halfway, and over 30 people were treated for exposure at Sheppey General Hospital. The old Sheerness bridge crossing was already under water over the wheels of cars by half past midnight, and the Kingsferry crossing was left marooned in around four miles of floodwater, cutting the town off from the mainland until Royal Navy divers cleared a way through some ten days later.
• January 1978. Floodwater filled Beachfields and Pavilion Gardens before pouring into the High Street, Railway Road, The Broadway and Trinity Road. A family in Delamark Road used a rowing boat to get about, basements along Marine Parade flooded, and the presses of the Sheerness Times Guardian stood under three feet of water, delaying that week's edition. No deaths were recorded, but the flood reached deep into the ordinary streets of the town centre.
• December 2013 — Storm Xaver. The tide at Sheerness reached its highest level since the Thames Barrier was completed, though still around half a metre to a metre below the 1953 peak. Good warning and a well-rehearsed response meant Sheerness and Queenborough themselves escaped the most severe "danger to life" warnings issued elsewhere on the north Kent coast that night — but the surge was a reminder that the risk has not gone away.

Dated, local flood history like this is evidence, not background colour. It shows how Sheerness has behaved before, and a credible assessment uses it to test how a site would perform during a surge today and over its lifetime, allowing for climate change.

Flood defences and the Sheerness benefit area

Almost the whole town depends on engineered defences, and a long-term Environment Agency strategy sets out exactly how they are managed. A defence lowers the chance of flooding; it never removes it, and planning policy still expects the residual risk behind it to be assessed.

The Environment Agency's Medway Estuary and Swale strategy names Sheerness as its own benefit area, split into two parts: the Minster Cliffs frontage, managed for coastal erosion, and the main Sheerness-to-Minster and Rushenden-to-Sheerness frontage, which carries the flood defences that protect the town and the port. The policy for the town itself, across every stage of the strategy, is to hold the line — but holding the line still means the defence has to be raised as sea levels rise.

• Crest levels are rising twice over. The preferred approach raises the defence crest around Sheerness to 5.4m AOD within three years of the strategy starting, and to 6.9m AOD within fifty years, lifting the standard of protection from around a 1-in-16-year event today toward a 1-in-1,000-year standard.
• Named assets sit behind the defence. Sheerness Docks, the A249/A250 approach roads, Sheerness-on-Sea station, Queenborough Marina and the Klondyke and Sheppey Plant industrial estates are all identified as assets protected by this stretch of frontage.
• Funded work is already under way. The Barton's Point shingle recycling scheme, funded through national flood defence grant-in-aid, is designed to raise the standard of protection at that frontage and defends several thousand properties along the shore between Sheerness and Minster.
• The benefit clearly outweighs the cost. The Environment Agency's own appraisal values the benefit of maintaining and raising these defences at many times their cost over the life of the strategy — the clearest official confirmation that this frontage is expected to be actively managed, not abandoned.

Planning policy and your Lead Local Flood Authority in Sheerness

Flood risk in Sheerness is judged against national policy — the NPPF and its Planning Practice Guidance — applied locally by the Environment Agency, Kent County Council as Lead Local Flood Authority, and Swale Borough Council as the planning authority. A good report speaks to all three.

Kent County Council is the Lead Local Flood Authority for surface water, groundwater and ordinary watercourses across the Swale district, and the statutory drainage consultee on major applications. Swale Borough Council determines planning applications and holds the local flood evidence and policies, including its Strategic Flood Risk Assessment. Swale's adopted Local Plan expects a further 200 or so dwellings in and around Sheerness through windfall and infill sites, and the Local Plan Review, now under way, will set the policy for the next generation of applications — while the borough's five-year housing land supply has recently run below the required level, which tends to sharpen scrutiny of exactly how flood risk is handled on any site that comes forward.

Sheerness Docks, regeneration and why people need a flood risk assessment here

The reasons people come to us reflect how Sheerness is changing. The docks, the town centre and the seafront each throw up a different case for an assessment, and each setting changes what the report has to prove.

• Expansion at the port. Sheerness Docks, operated by Peel Ports as one of the UK's larger vehicle-import and timber-handling terminals, continues to expand on reclaimed estuary land, including a new ro-ro berth and berth-extension works at the quayside. Reclaimed ground, defended tidal risk and quay-side drainage are central to any scheme here.
• Town centre and seafront regeneration. The £20 million Sheerness Revival programme, funded through the government's Levelling Up Fund, is redeveloping Beachfields and the seafront leisure centre, extending the local college and converting the Masters House into workspace — each project bringing new buildings onto ground close to the sea wall.
• Residential infill. Much of the town's planned housing growth is windfall and infill development within the existing built-up area of Blue Town, Mile Town and Marine Town, rather than one large new estate, so flood risk has to be assessed site by site.
• Homebuyers and older housing stock. Sheerness's older terraces, many close to the historic dockyard and the seafront, can carry a flood-risk flag that affects a mortgage or a purchase; a conveyancing search is not the same as a planning-grade assessment, and knowing which you need saves time and money.

How Unda helps with flood risk assessment in Sheerness

We act as the accurate translation layer between your scheme and the requirements set by the Environment Agency, Kent County Council as Lead Local Flood Authority, Swale Borough Council and national planning policy. We have prepared more than 5,000 flood risk assessments since 2014, we are a CIWEM business partner, and a senior flood risk consultant signs off every report.

A flood risk assessment in Sheerness from Unda assesses every credible source — the tidal estuaries and the Swale, surface water on the clay, groundwater and the residual risk behind the town's defences — compares modelled flood and surge levels against your proposed floor levels, sets safe access and egress, and recommends mitigation the regulators will accept. 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.

That same approach — reading the modelled data against the real ground — is how we clarified a high-risk surface water flag so a purchase could proceed, and it is how we approach a defended tidal site in Sheerness. Our flood risk consultants stay involved past the report to answer the questions the Environment Agency or local authority come back with.

Flood risk assessments for every situation in Sheerness

A flood risk assessment, a sequential or exception test and a drainage strategy are three different reports. They often travel together in a Sheerness 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 each of them, 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 and its Planning Practice Guidance, the Environment Agency and Swale Borough 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 or surface-water risk and you need the actual building assessed, not a broad map.
• Flood risk assessment for insurance. Property-specific evidence for brokers and underwriters where premiums have risen or cover has been restricted — common on a defended coast.
• Flood risk assessment for BREEAM. Structured around BREEAM Pol 03, which is credit-driven rather than safety-driven, so a planning FRA alone rarely satisfies it.
• Groundwater flood risk. A defensible design water table for clay sites and any basement — assessed as a source within the FRA, or as a standalone hydrogeological assessment 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. On a defended, low-lying town like Sheerness, the locational case often matters as much as the site assessment itself, and recent Kent appeal decisions have shown just how closely this test is now examined.

Drainage strategy and SuDS

• Sustainable drainage strategy (SuDS). Surface-water engineering — calculates existing versus proposed run-off and proposes SuDS, in line with the national standards for SuDS, to hold discharge within the required rate, usually by attenuation on the town's low-permeability clay.
• Preliminary drainage design. The early, outline read that flags infiltration and outfall 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 is not enough, including tidal breach and overtopping analysis.

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 — useful in Sheerness, where clay and reclaimed ground often complicate infiltration — 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.

Sheerness flood resources and emergency contacts

If you need to report flooding, check a tide level, or prepare for a flood in Sheerness, these are the bodies to contact. In a life-threatening flood emergency always call 999.

• Check for flooding in Sheerness. Environment Agency live warnings and alerts for the Sheerness, Minster and Queenborough flood warning area at check-for-flooding.service.gov.uk; sign up for flood warnings or call Floodline on 0345 988 1188.
• Kent County Council flood team. Report and read about surface water, groundwater and ordinary watercourse flooding at Kent County Council.
• Swale Borough Council. Planning, the Strategic Flood Risk Assessment and local flood evidence at Swale Borough Council.
• Tidal and coastal risk. The long-term plan for the town's defences in the Environment Agency's Medway Estuary and Swale strategy.
• Live river and tide levels. Whether levels around the Swale are running high right now via our live river levels map.

For broader context, our notes on the Flood Map for Planning and on flood zones 1, 2 and 3 are a good starting point, and you can check the official Flood Map for Planning for any site. Sheerness sits within our wider coverage of flood risk assessment in the Isle of Sheppey and flood risk assessment in Kent.

Flood risk assessment in Sheerness: frequently asked questions