Flood Risk Assessment in Tilbury

Unda prepares flood risk assessments and drainage strategies for sites across Tilbury and the wider Borough of Thurrock. Tilbury sits on low, reclaimed marshland on the north bank of the tidal Thames, where a large part of the town lies in Flood Zone 3 behind tidal walls and embankments — so almost every development here has to engage with flood risk early. A flood risk assessment in Tilbury shows the council and the Environment Agency that your scheme will stay safe for its lifetime, with climate change allowed for, without increasing flood risk to anyone else.

People come to us for a flood risk assessment in Tilbury for many reasons: to secure planning permission, to buy or sell a property, to satisfy a mortgage lender or insurer, to achieve a BREEAM rating, and to design the surface-water drainage for a new scheme. We prepare flood risk assessments in Tilbury for planning, property purchase, mortgage and insurance, and BREEAM, alongside sequential and exception tests and surface-water drainage strategies. A flood risk assessment, a sequential or exception test and a drainage strategy are three different reports: one asks whether the site is safe, one asks whether the development should be there, and one asks where the surface water goes.

In 1953 the sea wall at Bill Meroy Creek next to Tilbury Fort gave way in the night and the North Sea flooded Tilbury Town — more than 2,500 homes went under and around 1,300 people were evacuated to higher ground. The defences are far stronger today, but the land they protect still sits below the high-tide line, which is why flood risk in Tilbury has to be taken seriously on every site.

Our flood risk consultants know Thurrock well: the tidal Thames frontage, the River Mardyke and the arterial drains behind the wall, the London clay and chalk beneath the town, and the way Thurrock Council applies national flood policy as a unitary Lead Local Flood Authority. Call +44 (0) 1293 214444, email enquiries@unda.co.uk, or start a quote and one of our experienced flood risk consultants will talk through your site.

Flood risk assessment in Tilbury at a glance

Tilbury is one of the most flood-exposed towns on the Essex side of the Thames estuary. The headline facts below shape almost every assessment we prepare here.

• Tidal Thames is the dominant risk. Most of Tilbury lies in Flood Zone 3, the high-probability zone, defended by tidal walls along the estuary frontage. The risk is not day-to-day flooding but a defence breach or overtopping in a surge tide.
• Thurrock is its own Lead Local Flood Authority. Tilbury is governed by Thurrock Council, a unitary authority, not by Essex County Council — so the local flood policy, the SFRA and the drainage standards that apply here are Thurrock's.
• Around 11,000 properties in Thurrock are at risk. A large part of the borough's urban area, from Purfleet through Grays to Tilbury and Chadwell St Mary, sits in Flood Zone 3.
• More than one source at once. Beyond the tide, the River Mardyke, a network of arterial drains and dykes, surface water in the borough's Areas of Critical Drainage, and groundwater in the chalk south-west of the town can all combine.
• Major regeneration on defended land. Tilbury2, the consented Tilbury3 and the wider Thames Freeport are bringing large brownfield schemes forward on land that needs careful flood and drainage work.

Check flood risk in Tilbury and across Thurrock

Thurrock, the borough Tilbury sits in, is 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 Tilbury.

Flood risk in Tilbury: the tidal Thames, the Mardyke and surface water

Tidal flooding from the Thames estuary dominates flood risk in Tilbury. The town is built on low-lying reclaimed marshland on the north bank of the river, much of it less than a metre above mean sea level, so without its defences a large part of Tilbury would sit below the level of a high spring tide. The main rivers and the sea are the Environment Agency's responsibility; the River Mardyke, the arterial drains and the dykes behind the wall sit with Thurrock Council. Most sites here face more than one source of flooding at once, which is exactly what a credible tidal and sea flood risk assessment has to pin down.

The underlying geology is dominated by London clay, with chalk closer to the surface in the south-west of the Tilbury and Thurrock area. That matters because groundwater flooding is a real risk where the chalk carries high water levels, and groundwater appears on no national flood map — it has to be assessed from local geology and monitoring. Behind the tidal wall, low ground drains slowly and relies on a managed system of drains and pumps, so surface-water flooding is a planning issue in its own right across the borough's Areas of Critical Drainage.

You can screen any Tilbury postcode on our free flood risk map, watch the estuary and its feeder rivers on the live river levels map, and check the ground beneath a site on our geology and ground conditions map before committing to a drainage approach.

A history of flooding in Tilbury

Tilbury's flood history is why the council and the Environment Agency scrutinise development here so closely, and why a flood risk assessment in Tilbury has to be evidence-led rather than generic. The defining event still shapes the defences a developer designs around today.

• 1953 — the North Sea flood. On the night of 31 January into 1 February 1953, a storm surge raised sea levels around three metres above normal. The wall at Bill Meroy Creek by Tilbury Fort failed, more than 2,500 homes in Tilbury flooded and about 1,300 people were evacuated. Across eastern England 307 people died, including 58 on nearby Canvey Island.
• The national response. The 1953 disaster led directly to the modern Thames tidal defence system, including the Thames Barrier downstream, and to the raised walls and gates that protect Tilbury today.
• A defended, not a risk-free, town. Tilbury has not seen a 1953-scale flood since, precisely because the defences hold back ordinary surge tides — but the consequence of a breach remains severe, which is what an assessment here has to address.

This is the classic pattern of residual flood risk: strong defences lower the chance of flooding but cannot remove it, and a site can remain in a high flood zone even after new defences are built.

The defences protecting Tilbury

Tilbury is defended by a continuous line of tidal walls and embankments along the Thames frontage, backed by local defences within the town. Two structures stand out, and both have been strengthened in recent years to keep pace with rising sea levels.

• The Tilbury dual-function lock gate. The gate at the dock entrance, which replaced the older Tilbury Barrier, can be closed to hold back a surge tide while still serving navigation.
• The Port of Tilbury flood defence gates. A roughly £34 million Environment Agency and Port of Tilbury scheme replaced the three pairs of lock gates at the port entrance — each gate around 15 metres tall and 19 metres wide — raising them and tying them into the flood walls so they protect thousands of homes and businesses as well as carrying shipping.
• The Thames Estuary 2100 plan. Tilbury sits in the Purfleet, Grays and Tilbury policy unit of the Environment Agency's long-term Thames Estuary 2100 strategy, where the policy is to keep raising and adapting defences so flood risk does not increase as the climate and the estuary change.

For developers this is the key point: being behind a defence does not remove the need for a flood risk assessment in Tilbury. The Environment Agency still expects safe access and escape, finished floor levels set above the modelled flood level, and an allowance for the defences being overtopped or breached.

Planning policy and your Lead Local Flood Authority in Tilbury

Two authorities set the rules for development in Tilbury. The Environment Agency leads on the tidal Thames and the main rivers. Thurrock Council is the Lead Local Flood Authority — and because Thurrock is a unitary authority, it holds those powers itself rather than Essex County Council. It manages surface water, groundwater and ordinary watercourses, and it is the statutory consultee on surface-water drainage for new development.

Thurrock's evidence base is unusually current. Its Strategic Flood Risk Assessment (Level 1) was completed in January 2024, with part revised in July 2024, and it underpins the Sequential Test and the borough's surface-water drainage requirements. Development must also satisfy the National Planning Policy Framework and its Planning Practice Guidance, which is where the sequential and exception tests come in.

What your flood risk assessment in Tilbury must show

Because most of the town is in Flood Zone 3, an assessment here has to do more than restate the flood maps. It needs to set finished floor levels above the modelled tidal flood level with freeboard, demonstrate safe access and escape during a flood, account for climate-change allowances over the development's lifetime, and address the residual risk of the defences being breached or overtopped. Where a site genuinely sits outside the area at risk, a clear site-specific assessment can show that and streamline the application.

Development and flood risk assessment in Tilbury

Tilbury is one of the busiest regeneration fronts on the Thames, and the kind of site you bring forward shapes the assessment you need. The right scope is the difference between a clean approval and a drainage or flood-risk objection that holds an application up for months.

• Port and logistics expansion. Tilbury2, the consented Tilbury3 on the former power station land, and the wider Thames Freeport are large brownfield schemes on defended estuary land, where tidal flood risk, safe access and surface-water drainage all have to be resolved together.
• Town regeneration and housing. New homes in Tilbury Town and across the Thurrock urban area sit in higher-vulnerability use classes, so the flood risk vulnerability classification and the Sequential Test matter from the outset.
• Brownfield infill and change of use. Smaller sites still need a proportionate assessment where they fall in Flood Zone 2 or 3, an Area of Critical Drainage, or where surface-water mapping shows risk.
• Commercial and industrial units. Warehousing and employment schemes need drainage designed to the local SuDS standard and, often, a strategy for keeping operations running during a flood.

Climate change is not optional on the estuary. A flood risk assessment in Tilbury has to apply the Environment Agency's allowances for sea-level rise and higher rainfall over the development's lifetime, which sets floor levels, freeboard and how much attenuation a drainage scheme has to provide.

How Unda helps with flood risk assessment in Tilbury

We act as the accurate translation layer between your scheme and the requirements set by the Environment Agency, Thurrock Council as Lead Local Flood Authority, and national planning policy. We are experts on Thurrock's flooding and its planning context, not a generic report mill, and we write every report to be approved first time.

Whether you need a report for planning, a property purchase, a lender or insurer, or a drainage strategy for a new scheme, our flood risk consultants will tell you quickly what your Tilbury site needs and what it does not.

Flood risk assessments for every situation in Tilbury

People need a flood risk assessment in Tilbury for many different reasons, and we prepare the right report for each. It helps to keep three things separate: a flood risk assessment, a sequential or exception test and a drainage strategy are distinct reports that answer different questions, even though they often travel together in a planning submission. Groundwater and flood modelling are not separate reports — groundwater is a source every assessment considers, and modelling is a technique that feeds one.

• Flood risk assessment for planning. The site-specific report that satisfies the NPPF and shows your development is safe for its lifetime without increasing risk elsewhere. Groundwater and, where needed, flood modelling are assessed within it.
• Flood risk survey for property purchase. An independent, property-specific survey for buyers and their advisers that goes beyond a conveyancing search to assess the actual building.
• Flood risk assessment for insurance. Property-level evidence for brokers and underwriters where cover has been restricted, declined or priced on flood risk — useful where mortgage lending is also affected.
• Flood risk assessment for BREEAM. Structured around BREEAM Pol 03 so a scheme keeps its flood and surface-water credits.
• Sequential and exception tests. The locational justification that a higher-risk site is the most appropriate available, prepared alongside the assessment.
• Groundwater flood risk. A defensible design groundwater level for the chalk and clay around Tilbury, tested against floor levels, basements and drainage.
• Surface-water drainage strategy (SuDS). A scheme that manages runoff to Thurrock's standard, following the four pillars of SuDS and the drainage hierarchy, with preliminary drainage design and discharge of drainage conditions where needed.

Our free drainage calculators and BRE 365 infiltration rate calculator help at the early design stage, and you can browse our case studies or the wider Essex area guide and nearby Basildon page for more local context.

Tilbury flood resources and contacts

The most reliable flood information for Tilbury 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 Tilbury. 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.
• Thurrock Council flood risk. Strategy, developer guidance and how to report flooding at Thurrock Council.
• Thames Estuary 2100. The Environment Agency's long-term tidal defence plan for the Purfleet, Grays and Tilbury policy unit.
• Regional oversight. Tilbury falls under the Anglian (Eastern) Regional Flood and Coastal Committee, and sewer flooding is managed by Anglian Water.

Flood risk assessment in Tilbury: frequently asked questions