Flood Risk Assessment in Yorkshire

Our team at Unda use years of experience to prepare comprehensive flood risk assessments and drainage strategies for commercial and residential sites right across Yorkshire. A flood risk assessment in Yorkshire shows your local planning authority that a development will stay safe from flooding for its whole lifetime, without pushing flood risk onto anyone else.

Yorkshire is a big, varied region, and so is its flooding. We assess every source that matters here, from the Ouse and its tributaries through the Vale of York, to the tidal Humber and the eroding Holderness coast, to the surface water that overwhelms drains in Leeds, Sheffield and Hull. We then deal directly with the Environment Agency and the relevant lead local flood authority on your behalf, guiding architects, planning consultants, developers and landowners through to approval.

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

Flood risk assessment in Yorkshire at a glance

• Every source in one region. River, tidal, coastal, surface water and groundwater flooding all occur across Yorkshire, often on the same scheme.
• 4,000 homes and 2,000 businesses were caught up in the 2015 Boxing Day floods, at an economic cost of around half a billion pounds.
• 13 lead local flood authorities cover Yorkshire, from North Yorkshire Council to the metropolitan boroughs of Leeds, Sheffield and Bradford. We work with all of them.
• Flood Zone 1 is not a free pass. Since the 2025 PPG update, surface water risk can trigger an assessment even on a Flood Zone 1 site.

Check flood risk anywhere in Yorkshire

Yorkshire is outlined below. Screen any postcode in the region 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.

Flood risk in Yorkshire: rivers, coast and surface water

Yorkshire faces almost every type of flooding there is. River flooding dominates the Vale of York and the Pennine valleys, the tidal Humber and the North Sea coast bring saltwater risk to the east, and surface water now threatens the built-up centres of Leeds, Sheffield, Bradford and Hull. Most sites here face more than one source at once, which is why a desktop map rarely satisfies a planning officer on its own.

Nearly all of Yorkshire drains through one river system. The Swale, Ure, Nidd, Wharfe, Aire, Calder, Don and Derwent feed the Ouse, which carries their combined flow through York and on to the Humber. Add the River Hull, the Foss and the Esk, and you have a region where a heavy, prolonged rainfall event in the Pennines becomes a flood peak in the lowlands a day or two later. Understanding which watercourse drives the risk on a given site, and how it behaves, is the heart of a credible fluvial flood risk assessment.

• Rivers (fluvial). The Ouse and its tributaries flood the Vale of York and the Pennine towns. Calderdale, the Aire valley through Leeds, and the Don through Sheffield, Rotherham and Doncaster carry the highest river risk. Land in Flood Zones 2 and 3 along these corridors almost always needs an FRA.
• Tidal and coastal. The Humber is one of the most tidally vulnerable estuaries in the UK, and the Holderness coast is the fastest-eroding coastline in Europe. A North Sea surge here is a saltwater event, governed by tide and surge rather than rainfall. See our guide to tidal and sea flooding.
• Surface water (pluvial). Now the most widespread flood risk in England. Intense rain overwhelms drains in built-up Sheffield, Leeds, Hull and Bradford. Since the 2025 PPG update, surface water on the Flood Map for Planning can trigger an assessment even on a Flood Zone 1 site.
• Groundwater. The Chalk of the Yorkshire Wolds and the magnesian limestone belt can raise water tables that flood low-lying ground and basements without ever showing on a river map. Critical for any soakaway or below-ground level. See groundwater flooding.

Hull is the textbook case for why a single map is never enough: around nine in ten of the city sits below high-tide level, so it is squeezed between the tidal Humber, the River Hull and surface water that has nowhere to drain by gravity. A scheme there has to reconcile all three. Our wider notes on the sources of flood risk and on surface water and planning set out how these sources interact.

A history of flooding in Yorkshire

These dated events are why local authorities here scrutinise development so closely, and why a flood risk assessment in Yorkshire has to be evidence-led rather than generic. Each one reshaped local policy and the flood defences a developer now has to design around.

• 1947 — the post-war thaw. A sudden thaw on heavy snow, followed by intense rain, broke riverbanks across the country, with parts of Yorkshire among the worst hit. It pushed central government toward formal flood-control policy.
• 2000 — York and the Ouse. The Ouse rose to around 5.4 m above normal and flooded roughly 540 properties in York, with several hundred more saved only by the Foss Barrier. We mark the anniversary in York and the River Ouse remember the floods of 2000.
• 2007 — Hull and Sheffield. Summer deluges flooded more than 7,000 properties in Hull and overwhelmed the Lower Don Valley in Sheffield. Around 15,500 properties flooded across Hull and the East Riding. The event triggered the Pitt Review and, in turn, the Flood and Water Management Act 2010.
• 2013 — the Humber tidal surge. On 5 December a North Sea surge overtopped defences, flooding around 260 properties in Hull and more than 400 in the East Riding — the most serious tidal event on the estuary since 1953.
• 2015 — the Boxing Day floods. Storm Eva flooded around 4,000 homes and 2,000 businesses, including 627 properties in York. The Aire reached a record 2.95 m at Leeds, and Calderdale towns such as Hebden Bridge and Mytholmroyd were devastated. The economic cost reached about half a billion pounds.
• 2019 — Fishlake and the Don. A month's rain in a day sent the Don over its defences, flooding around 173 properties in Fishlake and roughly 1,600 across Doncaster, with 1,200 homes evacuated.
• 2023 — Storm Babet. The River Rother reached its highest recorded level, wrecking around 150 homes in Catcliffe and Treeton and flooding 182 properties across Rotherham. Yorkshire recorded its wettest three-day period on record.

A pattern runs through all of it: ground that flooded once tends to flood again. A robust assessment treats this recorded history as evidence, not background colour.

Flood defences and schemes protecting Yorkshire

Major investment has followed each of these events, and the schemes change what a development next to them has to prove. A new defence reduces the chance of flooding, but it never removes it, and planning policy still expects the residual risk to be assessed.

• Leeds Flood Alleviation Scheme. A £200 million, two-phase scheme on the Aire, completed in 2024, protecting more than 4,000 homes and over a thousand businesses to a 1-in-200-year standard, with climate change allowed for.
• York and the Foss Barrier. A £38 million upgrade after 2015 gave the barrier far greater pumping capacity, and wider works now better protect over 2,000 properties across the city.
• Humber 2100+. The Environment Agency and the estuary's local authorities are developing a long-term plan to manage tidal and sea-level-rise risk around the Humber for the next century and beyond.
• Hull and Living With Water. Hull and the East Riding have invested heavily since 2013, with the Living With Water partnership recognised internationally for building a more water-resilient city.

The catch for developers is the one we set out in residual flood risk and why a site stays in a flood zone after defences are built: the Flood Map for Planning is drawn as if the defences are not there, so a defended site can still sit in Flood Zone 3. Fishlake, where a defence below its design standard was overtopped, is the cautionary tale. Climate change makes this sharper still, which is why an assessment applies the Environment Agency's river-modelling allowances over the development's lifetime.

Planning policy and your Lead Local Flood Authority in Yorkshire

Two kinds of authority set the rules. The Environment Agency leads on the main rivers and the tidal Humber and coast. A Lead Local Flood Authority (LLFA) leads on surface water, groundwater and ordinary watercourses — and Yorkshire has thirteen of them, not the three the region once had.

Local government reorganisation has redrawn this map. North Yorkshire became a single unitary council in 2023, and the City of York, the East Riding and Hull are each unitary LLFAs in their own right. West and South Yorkshire have no county council; each metropolitan borough is its own LLFA. So a developer in Yorkshire deals with whichever authority covers the site, alongside the Environment Agency and the role the LLFA plays as statutory consultee on surface water drainage. Our overview of who manages flood risk in England explains how the pieces fit together.

Your assessment and drainage strategy must satisfy national policy — the NPPF and its Planning Practice Guidance — and the local framework: the relevant council's Local Flood Risk Management Strategy, its Strategic Flood Risk Assessment and adopted Local Plan flood policies. Where a higher-risk site is involved, the Sequential and Exception Tests apply, and the right vulnerability classification has to be argued. On drainage, the 2025 national SuDS standards and the four pillars of SuDS shape what each LLFA will accept.

What your flood risk assessment in Yorkshire must show

• Risk assessed from every credible source, using the Flood Map for Planning and local data.
• An appropriate location, tested against the Sequential Test where policy requires it.
• Safe for its lifetime, once the 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. Get one of these wrong and the application stalls, as our note on LLFA drainage objections shows.

Development and flood risk assessment in Yorkshire

Yorkshire's development is as varied as its geography, 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 objection that holds an application up for months.

• City-centre and riverside regeneration. Schemes in Leeds, Sheffield and Hull frequently sit in Flood Zones 2 and 3, needing finished floor levels, safe access and egress, and often compensatory flood storage.
• Pennine valley sites. Narrow, fast-responding catchments in Calderdale and the upper Aire mean little warning time, so safety and resilience carry real weight in the assessment.
• Coastal and estuary development. Holderness, the Humber bank and the East Riding bring tidal modelling, sea-level rise and, on parts of the coast, erosion into the picture — see sea-level rise and coastal flooding.
• Rural and agricultural schemes. Conversions and new builds across the Dales, the Wolds and the Vale of York often turn on surface water and ordinary watercourses rather than a main river, and on the right drainage information for planning.

Climate change is not optional here. A Yorkshire assessment must apply the Environment Agency's allowances for higher river flows, rainfall and sea levels over the development's lifetime — generally 100 years for housing — which sets floor levels, freeboard and how much attenuation a drainage scheme needs.

Home buyers and businesses come to us too. A flood risk question can affect mortgage lending and house prices, and a conveyancing search is not the same thing as a planning-grade assessment. Knowing which you actually need saves time and money, and our guide on doing your own assessment explains where the line falls.

How Unda helps with flood risk assessment in Yorkshire

We act as the accurate translation layer between your scheme and the requirements set by the Environment Agency, the relevant Yorkshire LLFA and national planning policy. We are experts on the region's flooding, not a generic report mill.

A flood risk assessment in Yorkshire from Unda assesses every credible source — the Ouse, Aire, Calder, Don or the tidal Humber, down to surface water, groundwater, sewers 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, the drainage strategy sits alongside the assessment so the two cases stay consistent and an objection has nowhere to land.

Our flood risk services for Yorkshire

• Flood risk assessment for planning. Site-specific reports that satisfy the Environment Agency and your Yorkshire LPA.
• Groundwater flood risk assessment. A defensible design water table for Wolds Chalk and basement sites, not a guess.
• Surface water drainage strategy and SuDS. Designed to each LLFA's standards from the first sketch.
• Sequential and Exception Test reports. Prepared alongside the assessment where policy requires them.
• Chartered flood risk consultants. Specialists who stay involved past the report to answer objections.
• How a flood risk assessment is done. What a robust report contains and how the process runs.

Yorkshire flood resources and contacts

The most reliable Yorkshire flood information comes from the lead authorities. For an immediate threat to life during a flood, always call 999.

• Check for flooding in Yorkshire. Environment Agency live warnings, river levels and maps at check-for-flooding.service.gov.uk.
• North Yorkshire flood and water management. The county's LLFA strategy and reporting at North Yorkshire Council.
• Yorkshire Regional Flood and Coastal Committee. Regional investment and priorities via the Yorkshire RFCC.
• York and the Foss Barrier. The Environment Agency's record of the Foss Barrier upgrade and new defences.
• Leeds Flood Alleviation Scheme. Scheme detail and coverage from Leeds City Council.
• Live river levels. Whether the Ouse, Aire or Don are running high right now via our live river levels map.

For flooding from blocked or burst sewers, contact Yorkshire Water. For broader policy context, our notes on the Environment Agency's planning role and on flood zones 1, 2 and 3 are a good starting point.

Flood risk assessment in Yorkshire: frequently asked questions