Flood Risk Assessment in Lincolnshire

A flood risk assessment in Lincolnshire is a site-specific report that examines how flooding could affect a development and shows the council it can go ahead safely without making flooding worse elsewhere. Lincolnshire is one of the most flood-exposed counties in England — low-lying fenland drained by pumps, three major rivers, and a long North Sea coast — so a clear, robust assessment is often what keeps a planning application moving.

We prepare flood risk assessments in Lincolnshire for planning, property purchase, mortgage and insurance, and BREEAM, alongside sequential and exception tests and surface-water drainage strategies (SuDS). Whether you are a developer, planning consultant, architect, agent, homebuyer or business, our chartered consultants translate the Environment Agency, Lead Local Flood Authority and national planning requirements into a report written to be approved first time.

Few counties in England test a development against flooding the way Lincolnshire does, and a clear, well-evidenced assessment is often what keeps a planning application on track.

Flood risk assessment in Lincolnshire at a glance

• One of England's highest-risk counties. Much of the Lincolnshire Fens sits at or below mean sea level and is kept dry only by embankments, drains and pumping, so river, coastal, surface-water and groundwater flooding can all affect a single site.
• Three Lead Local Flood Authorities. Lincolnshire County Council is the LLFA for the seven historic districts; North Lincolnshire and North East Lincolnshire are separate unitary authorities, each the LLFA for its own area. The Environment Agency leads on the main rivers and the sea.
• Most planning sites carry several risks at once. A site beside the Witham, Welland or an ordinary watercourse, on fen peat, or behind a coastal or tidal defence usually needs every source assessed — rivers and sea, surface water, groundwater and reservoirs.
• Sustainable drainage is expected. On major development the LLFA is a statutory consultee on surface water drainage, and a strategy that follows the SuDS hierarchy and local discharge limits from the start is the surest way to avoid an objection.
• A free, no-obligation quote within 60 minutes. Send us the site address and we will tell you quickly whether you need an assessment and what it should cover.

Check flood risk anywhere in Lincolnshire

Lincolnshire is outlined below. Screen any postcode in the county 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 assessment.

Why Lincolnshire floods: rivers, the Fens and the North Sea coast

Lincolnshire faces flooding from every direction. Three major rivers — the Witham, the Welland and the Trent on the western boundary — drain a large catchment towards the Wash, much of it across fenland that lies at or below sea level. On the coast, North Sea tides and storm surges threaten Boston, Skegness and the East Lindsey shore, while intense rainfall increasingly overwhelms drains in the towns. Many sites carry two or three of these risks together.

The River Witham is the county's defining watercourse: rising near South Witham, it runs roughly 132 kilometres through Grantham and Lincoln before turning south across the Fens to Boston and the Wash. The Welland drains the south of the county through Stamford and Spalding, the Steeping reaches the coast at Wainfleet, and a dense network of ordinary watercourses and artificial drains — among them the South Forty Foot Drain, the Barlings Eau, the River Glen, the Bain and the Slea — carries water across the low ground. Understanding which watercourse or drain governs the risk on a given site, and how it behaves, is the heart of a credible fluvial flood risk assessment.

Because so much of the county sits low and flat, water can arrive from the rivers, the sea and the sky at once, so a credible assessment has to weigh every source rather than just the obvious one.

Flood risk areas across Lincolnshire

Flood risk in Lincolnshire is concentrated where rivers, the coast and the fenland meet, but surface water now puts almost every town on the map. The towns most often identified at risk include Boston, Lincoln, Gainsborough, Spalding, Skegness, Mablethorpe, Holbeach and Wainfleet — though risk is site-specific, and a postcode in a "low risk" town can still sit on a floodplain or a critical drainage area.

• Boston and the Haven. One of the most flood-exposed towns in England, at risk from the tidal Haven, the Witham and surface water; the Boston Barrier was built specifically to address this.
• Lincoln. The Witham runs through the city, with the Brayford Pool and the lower High Street historically prone to fluvial and surface water flooding.
• The East Lindsey coast. Skegness, Mablethorpe and Sutton-on-Sea sit behind coastal defences on a shoreline that flooded catastrophically in 1953.
• The Fens and the Wash margins. Spalding, Holbeach and the South Holland fens lie on drained land below sea level, dependent on embankments and pumping.
• Wainfleet and the Steeping valley. The 2019 embankment breach showed how quickly a small river can inundate a fenland town.

National screening tools place these areas in context, but they do not decide a planning application. Our explainer on why you cannot use the long-term flood risk map for planning sets out the difference between the public risk service and the statutory Flood Map for Planning, and you can screen any Lincolnshire postcode on our free flood risk map.

A history of flooding in Lincolnshire

Lincolnshire's flood history is long and well documented, and it is exactly the kind of evidence the Environment Agency expects an assessment to engage with. From the 1953 North Sea flood to the Wainfleet breach of 2019 and the major incident of January 2025, the record shows risk from the coast, the rivers and increasingly from surface water.

• 1953 North Sea flood. The catastrophic storm surge of 31 January – 1 February 1953 devastated the Lincolnshire coast at Mablethorpe, Sutton-on-Sea and Ingoldmells, killing dozens and prompting the modern coastal defence programme.
• December 2013 tidal surge. The largest North Sea surge since 1953 overtopped defences in Boston, flooding hundreds of properties and directly prompting the Boston Barrier scheme.
• June 2019, Wainfleet. After roughly two months' rain fell in two days, the River Steeping embankment breached, evacuating hundreds of residents and requiring weeks of pumping, including by RAF helicopters.
• November 2019. The Barlings Eau and lower Witham flooded farmland, homes and caravan parks around Short Ferry, Fiskerton and Bardney.
• January 2025. Heavy rain on frozen, saturated ground triggered a major incident; around 88 properties flooded internally, worst in Boston and South Kesteven, with river levels at Boston peaking near 3.19 metres above datum on 7 January.

Lincolnshire's flooding increasingly comes from slow-moving groundwater and ordinary watercourses that fall outside national flood warning coverage, which is why the county is trialling a new local approach.

That local picture is the subject of our article on why Lincolnshire is trialling a new approach to flood warnings through its Project Groundwater initiative — a reminder that the assessed risk on a site can come from sources a generic map never shows.

Flood defences and drainage in Lincolnshire

Lincolnshire is one of the most heavily defended and intensively drained landscapes in the country, but defences reduce the probability of flooding rather than removing it. A site protected by the Boston Barrier, the coastal scheme or a fenland pumping system still carries residual risk, and planning policy requires that risk to be assessed over the development's lifetime.

• The Boston Barrier. An Environment Agency tidal-surge barrier on the Haven whose main gate became operational in December 2020, better protecting more than 14,000 homes and 800 businesses; remaining works are programmed to complete later this decade.
• The Lincshore coastal scheme. Annual beach nourishment between Mablethorpe and Skegness, running since 1994, maintains a roughly 1-in-200-year (0.5% annual probability) standard of tidal protection for around 30,000 properties and 35,000 hectares.
• Internal Drainage Boards. Around eleven IDBs — including the Black Sluice, Witham and Welland & Deepings boards — manage water levels across the low-lying Fens through channels, sluices and pumping stations, and their consent is often needed to discharge.
• The Fens 2100+ programme. The Environment Agency's long-term plan for the fenland catchments — including the Steeping, Lower Welland, South Forty Foot and Lower Witham Fens — is reshaping how flood risk is managed across the area.

A defence lowers the odds of flooding; it never removes them. Planning policy treats the residual risk behind every barrier and pumping station as something an assessment must still confront.

Because the Flood Map for Planning is drawn as if defences were absent, defended Lincolnshire sites frequently remain in Flood Zone 3. Our explainer on residual flood risk sets out what an assessment must show for those sites, and where ordinary watercourses run along a boundary, our guide to riparian ownership explains the maintenance and consent duties that come with them.

Planning policy and your Lead Local Flood Authority in Lincolnshire

For most of Lincolnshire the Lead Local Flood Authority is Lincolnshire County Council, responsible for surface water, groundwater and ordinary watercourses, while the Environment Agency leads on the main rivers and the sea. North Lincolnshire and North East Lincolnshire are separate unitary authorities and act as their own LLFAs. A development is assessed by whichever authority covers the site.

Lincolnshire County Council sets out its approach in the Joint Lincolnshire Flood Risk and Water Management Strategy and works alongside the Environment Agency, Anglian Water and the Internal Drainage Boards as Risk Management Authorities. Each local planning authority maintains a Strategic Flood Risk Assessment that a developer must engage with, and on major development the LLFA is a statutory consultee whose drainage advice the planning authority must take into account — a role explained in our note on what a Lead Local Flood Authority does.

• National policy. The NPPF and its Planning Practice Guidance apply a sequential, risk-based approach to all sources of flooding; see our NPPF flood risk guidance.
• Local Plans. The Central Lincolnshire Local Plan (Lincoln, North Kesteven and West Lindsey) and the South East Lincolnshire Local Plan (Boston and South Holland) carry flood and drainage policies each application must satisfy.
• Strategic Flood Risk Assessments. The relevant SFRA maps flood zones, surface water and critical drainage areas, and often sets the local standard for what an assessment must address.
• Sustainable drainage. Major development is expected to use SuDS designed to the 2025 national standards and local discharge limits; the LLFA reviews the strategy.
• Internal Drainage Board consent. Discharging to, or working near, an ordinary watercourse in an IDB district usually needs the board's consent in addition to planning permission.

An unresolved drainage objection can stop a planning authority determining an application for months. Our note on the most common reasons an LLFA objects to a planning application shows why getting the drainage case right from the outset matters.

Development and flood risk assessment in Lincolnshire

Lincolnshire's development pressures — housing growth around Lincoln and the market towns, agricultural and food-sector schemes across the Fens, energy and logistics on the larger sites, and coastal regeneration — nearly all interact with flood risk, because so much of the county sits on a floodplain, behind a defence or on drained land.

• Residential schemes. Housing classed as more vulnerable development in Flood Zones 2 or 3 needs an assessment and usually a sequential test; finished floor levels, safe access and compensation are recurring issues on valley and fen sites.
• Agricultural and food-sector development. Barns, glasshouses, processing and storage across the Fens often sit on land managed by an Internal Drainage Board, where discharge rates and consents shape the drainage strategy.
• Commercial, energy and logistics. Larger sites increase impermeable area and runoff, so a surface water drainage strategy is frequently conditioned even where river risk is low.
• Coastal and regeneration schemes. Development on the East Lindsey coast must address tidal and residual breach risk behind the defences over its full lifetime.
• Conversions and small sites. Even minor development in a critical drainage area or a surface-water hotspot can trigger an assessment or a drainage strategy.

How Unda helps with flood risk assessment in Lincolnshire

We act as the accurate translation layer between your scheme and the requirements set by the Environment Agency, the relevant Lincolnshire Lead Local Flood Authority and national planning policy. We are experts on the county's flooding, not a generic report mill.

A flood risk assessment in Lincolnshire from Unda assesses every credible source — the Witham, Welland and their tributaries, the tidal coast, surface water, groundwater rising through the limestone and fen silts, sewers, reservoirs and any ordinary watercourse on the boundary — compares modelled flood levels against your proposed floor levels, sets safe access and egress, and recommends mitigation the regulators 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 Lincolnshire

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, 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 your Lincolnshire planning authority. 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 river, coastal or surface-water risk and you need the actual building assessed, not a broad map. Flood history can affect value — see our note on whether 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, common in Lincolnshire's higher-risk towns.
• 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 limestone, Wolds chalk and fen-silt 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. A clean site-specific assessment showing the development is not actually within an area at risk can remove the need at application stage — a live policy area, as our note on what the Yatton judgment means for planning explains.

Drainage strategy and SuDS

• Sustainable drainage strategy (SuDS). Surface-water engineering — calculates existing versus proposed runoff and proposes SuDS to hold discharge within the local and Internal Drainage Board limits. Our explainer on the four pillars of SuDS sets out what a good scheme delivers.
• 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 is not enough.

Early in a drainage strategy it helps to know whether the ground will take water, which is rarely straightforward on Lincolnshire's clays, silts and high water tables: 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. For the full picture of what we do, see our flood risk assessment service.

Lincolnshire flood resources and contacts

The most reliable Lincolnshire 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 Lincolnshire. Environment Agency live warnings, river levels and maps at check-for-flooding.service.gov.uk; sign up for flood warnings or call Floodline on 0345 988 1188.
• Lincolnshire County Council flood risk management. Strategy, reporting and developer guidance at lincolnshire.gov.uk, including the Project Groundwater initiative.
• Boston Barrier scheme. The Environment Agency's tidal-surge barrier for Boston is detailed in the Boston Barrier scheme guidance.
• Coastal flood risk. The Lincolnshire Resilience Forum sets out coastal and tidal risk and how to prepare.
• Internal Drainage Boards. The boards managing fenland water levels are listed by the Association of Drainage Authorities (Lincolnshire).
• Live river levels. Whether the Witham or Welland are running high right now via our live river levels map.

North Lincolnshire and North East Lincolnshire are served by their own councils as Lead Local Flood Authorities, so a site in those areas is reported and assessed through them rather than the county council. For broader policy context, our notes on the Environment Agency's planning role and on groundwater in planning applications are a good starting point.

Flood risk assessment in Lincolnshire: frequently asked questions