Flood Risk Assessment in Nottinghamshire

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

Nottinghamshire is shaped by the River Trent, which crosses the county from Long Eaton in the south-west, past Nottingham and on through Newark towards the Humber. We assess every source that matters here — the Trent and its tributaries the Leen, Erewash, Greet, Devon and Idle, the surface water that overwhelms drains in Nottingham, Mansfield and Worksop, and the groundwater that rises through the Sherwood Sandstone in the north and west of the county — then deal directly with the Environment Agency and the relevant Lead Local Flood Authority on your behalf. We prepare flood risk assessments in Nottinghamshire 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.

The Trent rose to a record level north of Newark during Storm Henk in January 2024, beating the benchmark November 2000 flood — so a flood risk assessment in Nottinghamshire has to read the river, the surface water and the groundwater together, or it will not stand up to the Lead Local Flood Authority.

Phone +44 (0) 1293 214444 or email enquiries@unda.co.uk to speak to one of our experienced flood risk consultants, or start a quote and we will respond within 60 minutes.

Flood risk assessment in Nottinghamshire at a glance

• The River Trent is the dominant flood source. Most of the county's significant flooding comes from the Trent and its tributaries, with surface water and groundwater adding risk that the river maps alone do not show.
• Two Lead Local Flood Authorities cover the area. Nottinghamshire County Council leads on local flood risk across the county, and Nottingham City Council does the same within the city. We work with both, alongside the Environment Agency.
• Flood risk reaches well beyond the floodplain. Storm Babet in October 2023 and Storm Henk in January 2024 flooded homes and businesses from Worksop and Retford in the north to Newark, Radcliffe-on-Trent and West Bridgford in the south.
• A flood risk assessment is an evidence task. Every claim about flood levels, climate change allowances and mitigation has to be sourced and site-specific — a generic, place-name-swapped report is exactly what the Environment Agency and the council reject.

Check flood risk anywhere in Nottinghamshire

Nottinghamshire 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.

Flood risk in Nottinghamshire: the Trent, its tributaries and surface water

River flooding dominates Nottinghamshire. The River Trent crosses the whole county, gathering water from a catchment that reaches deep into the Midlands before it carries that flow north-east through Nottingham and Newark. Surface water now threatens the built-up parts of Nottingham, Mansfield, Worksop and Retford, and groundwater rises through the Sherwood Sandstone in the north and west — so many sites here face more than one source at once.

The River Trent and its tributaries

The Trent is a slow-responding lowland river, which gives some warning before it peaks but also means it stays high for days once a flood is under way. It collects a string of Nottinghamshire tributaries that each bring their own risk: the Leen through the north of Nottingham, the Erewash along the Derbyshire boundary, the Greet at Southwell, the Devon at Newark, and the Idle — fed by the Maun and Meden — draining Mansfield, Worksop and Retford before it reaches the Trent. Smaller watercourses such as Cocker Beck at Lowdham and Dover Beck can flood fast and have repeatedly put homes under water. Anyone developing land beside one of these channels also takes on riparian responsibilities that the Environment Agency and the council will expect to see addressed.

Surface water in Nottingham, Mansfield and the towns

Surface water is now the most widespread source of flood risk in England, and Nottinghamshire's urban centres feel it acutely. Where drains are at capacity, blocked or undersized, heavy rain runs off hard surfaces faster than the system can take it, which is a recognised constraint to development in parts of Nottingham City. A site can sit comfortably in Flood Zone 1 for rivers and still flood from surface water, which is why a careful reading of the critical drainage areas and the surface water mapping matters as much as the river data — and why national mapping is a starting point rather than the answer, as we explain in are flood maps accurate?

Groundwater and the Sherwood Sandstone

The geology divides the county. The Trent valley and the east sit largely on Mercia Mudstone — a clay that sheds water and frustrates soakaway drainage — while the north and west run on the permeable Sherwood Sandstone, a major aquifer. On the sandstone, infiltration drainage can work well, but a rising water table can also bring groundwater up into basements and low ground, and the legacy of the old North Nottinghamshire coalfield adds mine-water rebound to the picture in places. Groundwater appears on no national flood map, so it is assessed as a distinct source within the groundwater flood risk assessment that forms part of the wider report.

A history of flooding in Nottinghamshire

These dated events are why local authorities here scrutinise development so closely, and why a flood risk assessment in Nottinghamshire 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 benchmark Trent flood. Snowmelt and rain caused widespread flooding along the Trent valley and through Nottingham, prompting the major flood defences built in the 1950s, including the Holme Sluices at Colwick.
• November 2000 — the “Millennium” flood. The fifth largest flood recorded at Nottingham, with the Trent's peak flow running at around twelve times its normal rate. Some 15,000 homes were at risk but the 1950s defences held, sparing the city the devastation of 1947.
• July 2013 — Southwell and Lowdham. Intense summer rainfall sent the Greet through Southwell and Cocker Beck through Lowdham, flooding hundreds of homes in flash events that the main-river maps barely captured.
• October 2023 — Storm Babet. Nottinghamshire County Council's Section 19 investigations record internal flooding across the county, including Worksop, Southwell, Newark-on-Trent, Blidworth, Bilsthorpe, Kirkby-in-Ashfield and Toton — surface water and ordinary watercourses as much as the main rivers.
• January 2024 — Storm Henk. Falling on ground already saturated by Storm Babet, Henk flooded 344 homes and 40 businesses and closed 69 roads across Nottinghamshire, with more than 100 properties evacuated. The Trent reached a record level north of Newark, surpassing November 2000.
• A village that floods again and again. Lowdham has flooded in 1999, 2007, 2012, 2013, 2019, 2020, 2023 and 2024 — the clearest illustration in the county that a single past defence does not settle the risk.

Flood defences and schemes protecting Nottinghamshire

Large parts of the county are defended, but a defence reduces the chance of flooding rather than removing it. Understanding what protects a site — and what happens if that protection is overtopped or breached — is central to a sound assessment.

• Nottingham Left Bank Flood Alleviation Scheme. This £45 million Environment Agency scheme reduces flood risk to around 16,000 homes and businesses along a 27 km stretch of the Trent from Sawley to Colwick — the country's biggest inland flood defence by the number of properties protected — including raised and strengthened defences around Colwick and the Holme Sluices.
• Lowdham Cocker Beck Flood Alleviation Scheme. A new flood-storage area upstream of Lowdham, able to hold up to 100,000 cubic metres of water, designed to protect the village after decades of repeated flooding and expected to deliver close to £50 million in benefits.
• Residual risk stays on the map. Because the Environment Agency's Flood Map for Planning is drawn as if defences are not there, a defended site near the Trent or in West Bridgford can still sit in Flood Zone 3. The residual flood risk — what remains if a defence is overtopped or fails — has to be assessed over the development's lifetime.

Where a site sits behind a defence or beside a watercourse, demonstrating safe access and egress and the right floor levels often depends on understanding the breach and overtopping scenarios, which is where site-specific flood modelling earns its place within the assessment.

Planning policy and your Lead Local Flood Authority in Nottinghamshire

Two kinds of authority set the rules. The Environment Agency leads on the River Trent and the other main rivers. A Lead Local Flood Authority (LLFA) leads on surface water, groundwater and ordinary watercourses — and in Nottinghamshire that is Nottinghamshire County Council across the county and Nottingham City Council within the city.

A developer here deals with whichever authority covers the site, alongside the Environment Agency and the role the LLFA plays as statutory consultee on surface water drainage for major development. The Environment Agency's part in the process is set out in our guide to the Environment Agency and flood risk planning. When the drainage information is not robust enough, the result is usually an LLFA objection that holds the application up until it is resolved.

What your flood risk assessment in Nottinghamshire must show

Your assessment and drainage strategy must satisfy national policy — the NPPF and its Planning Practice Guidance — and the local framework: the county's Local Flood Risk Management Strategy, the relevant Strategic Flood Risk Assessment and each district's adopted Local Plan policies. Where a higher-risk site is involved, the Sequential and Exception Tests apply, a live area of policy shaped by cases such as the Yatton judgment. On drainage, the four pillars of SuDS and infiltration evidence to BRE 365 shape what each LLFA will accept — and on the Sherwood Sandstone, infiltration is often viable, while the Mercia Mudstone of the Trent valley usually is not.

Development and flood risk assessment in Nottinghamshire

Nottinghamshire carries a busy development pipeline, from city-centre regeneration to former colliery and industrial land, 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.

• Urban regeneration and infill. Schemes across Nottingham, Beeston and the wider conurbation usually turn on surface water and the capacity of an already-stretched drainage network, where a surface water drainage strategy often matters as much as the river assessment.
• Brownfield and former coalfield land. Mansfield, Ashfield and Bassetlaw carry extensive former colliery and industrial sites where made ground, mine-water rebound and contamination shape both the flood and the drainage case, and infiltration has to be tested rather than assumed.
• Trent valley and riverside sites. Development at Newark, Radcliffe-on-Trent and along the river frequently sits in Flood Zone 2 or 3, calling for finished floor levels, safe access and sometimes compensatory flood storage or floodable voids.
• Rural and agricultural schemes. Conversions and new builds across the Vale of Belvoir, Sherwood and the Idle catchment often hinge on ordinary watercourses and surface water rather than a main river, and on the right preliminary drainage design early on.

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

How Unda helps with flood risk assessment in Nottinghamshire

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

A flood risk assessment in Nottinghamshire from Unda assesses every credible source — the Trent and its tributaries, 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, rated 5.0 on Google, 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. You can read more about Unda and how our flood risk consultants work.

Flood risk assessments and related reports for every situation in Nottinghamshire

People need a flood risk assessment or drainage work in Nottinghamshire for many reasons. A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct reports: the assessment asks whether the site is safe, the sequential test asks whether the development should be there, and the drainage strategy asks where the surface water goes. We prepare all of them.

• Flood risk assessment for planning. The site-specific report prepared to satisfy the NPPF, the Environment Agency and your Nottinghamshire LPA. Groundwater and, where needed, flood modelling are assessed within it rather than as separate reports.
• Flood risk survey for property purchase. An independent, property-specific survey for home buyers and their advisers when a conveyancing search flags risk — flood risk can also affect house prices and insurability.
• Flood risk assessment for insurance. Property-specific evidence for brokers and underwriters where premiums rise, cover is restricted, or risk has been mapped inconsistently with the site.
• Flood risk assessment for BREEAM. Structured around BREEAM Pol 03 so flood and surface water credits are secured from the outset.
• Sequential and Exception Tests. The locational policy case for higher-risk sites, prepared alongside the assessment.
• Surface water drainage strategy and SuDS. Designed to the 2025 national standards and the local discharge hierarchy, with discharge of drainage conditions at the detailed stage.

We back this with free screening tools you are welcome to use: the flood risk map, the live river levels map for the Trent and its tributaries, the geology and ground conditions checker for soakaway feasibility on the Sherwood Sandstone, our drainage calculators and the BRE 365 infiltration rate calculator. For developments in Wales the equivalent report is a flood consequence assessment.

Nottinghamshire flood resources and contacts

The most reliable Nottinghamshire 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 Nottinghamshire. 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.
• Report and understand local flood risk. Nottinghamshire County Council's flooding help, strategy and reporting routes at nottinghamshire.gov.uk, including the Local Flood Risk Management Strategy and Section 19 flood investigation reports.
• Flood risk in the city. Nottingham City Council acts as the Lead Local Flood Authority within the city boundary.
• Schemes that reduce flooding. Details of the county's flood alleviation schemes, including Lowdham, are published by Nottinghamshire County Council.
• The statutory planning dataset. Flood zones for a site come from the Environment Agency's Flood Map for Planning — not the public long-term risk map, as we explain in our guide to the two flood maps.

Flood risk assessment in Nottinghamshire: frequently asked questions