River Nene Flooding & Flood Risk

The River Nene floods, and when it does the consequences reach a long way. It gathers three arms above Northampton, then runs for more than a hundred miles across low, wide valley ground to Peterborough and out through the Fens to the Wash, so a single wet spell can put homes, farmland and development sites at risk from the edge of Daventry to the quays of Wisbech. Its worst modern flood killed two people and put around 2,500 Northampton homes under water on the Easter weekend of 1998. Unda prepares flood risk assessments, drainage strategies and related reports for sites across the Nene floodplain. To talk it through, call 01293 214444 or email enquiries@unda.co.uk.

Over the Easter weekend of 9–10 April 1998, a stationary band of rain fell on a saturated Nene catchment and the river burst through Northampton: two people died, about 2,500 homes flooded in the town, and the Wansford gauge downstream reached 2.941 metres, still its highest level on record.

• A big lowland river. The Nene runs about 169 kilometres (105 miles) from near Badby, west of Northampton, to the Wash at Sutton Bridge, which makes it the tenth-longest river in the United Kingdom.
• A designated Main River. The Environment Agency regulates the Nene along effectively its whole length, so the 8 metre byelaw margin and Flood Risk Activity Permits apply to work near it.
• Tidal for the last 45 kilometres. Below the Dog-in-a-Doublet sluice near Peterborough the river is tidal all the way to the Wash, which puts Wisbech and the lower Fens at risk from the sea as well as the river.
• Storage that has to be defended. The Nene Washes hold back floodwater over roughly 1,450 hectares east of Peterborough, kept in check by embankments the Environment Agency has spent around £26 million strengthening.

Check flood risk along the River Nene

The map below draws the River Nene in coral, with the Environment Agency’s live river gauges positioned along it. Click a gauge to see its latest level, its typical range and its record peak. Enter a postcode near the river to zoom in and screen that location against the Environment Agency’s flood data for rivers and sea, surface water, reservoirs and the flood zones used for planning. It is an indicative screening tool, not a flood risk assessment.

Why does the River Nene flood?

The Nene floods for reasons that change along its length, which is part of what makes it a demanding river to build near. In its upper catchment around Northampton it behaves like a responsive lowland river. Three arms, the Brampton, Kislingbury and Wootton branches, drain a catchment of impermeable clays and low, gently sloping farmland and meet in the town, so runoff from a wide area arrives at much the same time. Average rainfall across the catchment is modest, around 635 millimetres a year, but the ground gives water up quickly rather than storing it. That is why the river can rise sharply after prolonged or intense rain even though the region is comparatively dry.

Below Northampton the character shifts. The valley broadens and flattens, the gradient slackens, and the river spreads across a wide floodplain as it passes Wellingborough, Thrapston and Oundle on its way to Peterborough. Here the tributaries matter. The River Ise joins at Wellingborough, and Harper’s Brook and Willow Brook come in through the north Northamptonshire countryside, each adding to the volume the main channel has to carry. The catchment as a whole covers about 1,630 square kilometres and delivers a mean flow of roughly 9.3 cubic metres a second, but flood flows are many times that.

The lower river is different again. Below the Dog-in-a-Doublet sluice near Peterborough the Nene becomes tidal for its final 45 kilometres to the Wash, running in raised, embanked channels across land that in places lies at or below sea level. When a high tide meets high river flow the channel can tide-lock, with the sea holding the freshwater back, and the water has nowhere to go but onto the washlands set aside for it. This is the reach where fluvial and tidal risk combine, and it is why Wisbech, ten miles inland, still floods from the sea.

• Three arms, one town. The Brampton, Kislingbury and Wootton arms of the Nene converge at Northampton, concentrating runoff from a wide upper catchment into a single channel at the town.
• Impermeable ground, quick response. Clay-dominated geology and a low average rainfall of about 635 mm produce a river that stores little and rises quickly after heavy or prolonged rain.
• Gauged along its length. The Environment Agency records levels at Wansford, Orton Sluice and other stations on the river, and these gauges appear on the map above with their latest readings.
• Tide-locked at the bottom. Below Dog-in-a-Doublet the river is tidal to the Wash, so high tides can hold back flood flows and push risk onto the Fenland washlands.

A history of flooding on the River Nene

The Nene has a long and well-documented flood record, and the events on it fall into two families: the fluvial floods of the upper and middle river, and the tidal floods of the Fenland reach.

The most serious modern flood came over the Easter weekend of 1998. On 9 and 10 April, after an unusually wet spring, a slow-moving band of heavy rain settled over the Midlands and fell on ground that was already saturated. The Nene and its tributaries burst their banks, and Northampton took the worst of it. Around 2,500 homes flooded in the town, with the Far Cotton and St James districts particularly badly hit, thousands of people were evacuated, roughly 150 were treated for injury or hypothermia, and two lives were lost. Damage across Northamptonshire was estimated at £75 million. The flood reshaped the town’s defences. In the years that followed, the Environment Agency built the Northampton Washlands and new defences through the centre of the town where the three arms combine, and has since invested more than £12 million in flood risk management across the county.

The Fenland reach has its own benchmark. During the North Sea storm surge of 11–12 January 1978, the tidal Nene overtopped its banks on both of Wisbech’s Brinks, around a thousand people were evacuated, and one resident drowned in her home. Wisbech’s response was to raise the riverside banks by about 1.5 metres, replace railings with flood walls and install a line of flood gates. Those defences have been raised again since and are still being strengthened along Nene Quay.

More recent years have kept the record current. The Orton Sluice gauge set its high mark of 3.083 metres in November 2012, the river prompted flood warnings through Peterborough in December 2020, and the winters since have repeatedly brought the Nene out of bank, with flooding of the Embankment at Wellingborough and severe flood warnings issued along the middle river during the wettest spells. For anyone assessing a site near the river, this is the record a flood risk assessment has to reckon with.

Which areas does the River Nene put at risk?

Flood risk on the Nene is spread along its whole length, and the Environment Agency runs a formal warning service for the communities most exposed. Flood alert areas cover the river in broad reaches, the Upper, Middle and Lower Nene, while more precise flood warning areas sit over the towns where the Agency can warn individual properties, from Northampton down to the tidal defences at Wisbech. The table below sets out the main settlements at risk from source to mouth.

If your site sits within one of these areas, the Environment Agency’s flood map for planning is likely to place it in Flood Zone 2 or 3, which triggers the need for a site-specific flood risk assessment. You can screen any address against the live Environment Agency data using the map above, and the towns along the river are covered in more depth on our local pages for Northamptonshire, Wellingborough, Peterborough, Wisbech and the wider Cambridgeshire Fens, with the planning requirements of the Fenland district set out separately.

Is the River Nene a Main River, and what that means for your site

The River Nene is a designated Main River for effectively its whole length, which means the Environment Agency, rather than the local council, is the regulator for the channel and its immediate margins. That distinction matters if you are developing nearby. Works within 8 metres of the top of the bank generally need a Flood Risk Activity Permit from the Environment Agency before they start, sought alongside planning permission rather than instead of it, and a site in the river’s floodplain will normally need a flood risk assessment to support its application. In the Fenland reaches the picture gains another layer. The low, pumped land is drained through the Middle Level system and managed by internal drainage boards, whose consent may also be needed for works or new discharges. The many brooks and field ditches that feed the Nene are ordinary watercourses instead, regulated by the relevant lead local flood authority and by the riparian owners whose land they cross. Getting that classification right at the outset saves time and cost later.

• The 8 metre byelaw margin. Building, excavation or structures near the Nene usually require a Flood Risk Activity Permit, sought alongside planning permission.
• Internal drainage boards in the Fens. On the lower river the Middle Level and its drainage boards manage water levels, and their consent can be needed for works or new discharges.
• Know which watercourse you are on. The Nene itself is Environment Agency territory; its brooks and ditches are ordinary watercourses under the lead local flood authority. We confirm this for every site.

How the Nene’s flood risk is managed

Responsibility for flood risk on the Nene is shared, and it helps to know who does what. The river sits within the Anglian River Basin District, and the Environment Agency’s catchment-scale strategy is set out in the Nene Catchment Flood Management Plan. The Environment Agency regulates the Main River, maintains the Fenland flood defences and washlands, publishes the flood map for planning and issues flood warnings. Local flood risk, meaning surface water, groundwater and ordinary watercourses, falls to the lead local flood authorities the river passes through: West Northamptonshire and North Northamptonshire in the upper and middle catchment, then Peterborough and Cambridgeshire in the Fens, each with its own strategic flood risk assessment that a local application has to address. The Nene Washes are the keystone of the lower catchment’s defences, a washland reservoir roughly 20 kilometres long and up to 1.4 kilometres wide that floods deliberately to store river water when the tidal reach locks, holding floodwater back to protect Peterborough, the railway and thousands of hectares of farmland behind it. The embankments that contain it are the subject of the Environment Agency’s Whittlesey Washes South Barrier Bank scheme. Why land beside a river is kept clear for water in this way is explained in our guide to why floodplains matter.

How Unda helps with flood risk on the River Nene

Unda understand how the River Nene behaves in flood, and what the planning system and the Environment Agency expect from the reports that follow. We know how the upper river responds to rain above Northampton, how the middle valley spreads out of bank through Wellingborough and Oundle, and how the tidal reach and its washlands govern risk from Peterborough down to Wisbech. We prepare flood risk assessments and drainage strategies for developers, planning consultants, architects, agents and homeowners with sites the length of the valley. Every assessment rests on the same evidence the regulators use: the Environment Agency’s flood mapping, the river’s gauged levels and modelled flows, and the local planning policy that applies to the site.

If you are working on a site near the River Nene, talk to one of our experienced flood risk consultants about what your application will need.

Flood risk and drainage services for sites near the River Nene

A development near the Nene can call for several different reports, and it helps to be clear that they answer different questions. 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 address separate things: whether the site is safe from flooding, whether the development should be located here, and where the surface water goes. Unda prepares each of them for sites across the Nene catchment.

• Flood risk assessments for planning. Site-specific assessments dealing directly with the Environment Agency’s requirements for development in the river’s flood zones. See our flood risk assessment for planning service.
• Assessments for property purchase and insurance. Independent reports for buyers, owners and lenders through our flood risk survey for property purchase and flood risk assessment for insurance.
• Drainage strategies and SuDS. Surface-water designs that manage runoff and meet the discharge limits set by the lead local flood authority or drainage board, through our sustainable drainage strategy service, with the detailed scheme needed to discharge a drainage condition.
• Sequential and exception tests. Locational justification where policy requires it, through our sequential and exception test reports.
• BREEAM and groundwater. A BREEAM flood risk assessment for the Pol 03 credit, and a groundwater flood risk assessment where a high Fenland water table is in play.
• Flood modelling. Hydraulic flood modelling to derive accurate flood levels and extents where national mapping is not enough, a common situation for sites right beside a Main River. Everything is framed by the NPPF and its planning practice guidance.

Live levels and who to contact in a flood

• Live river levels. Check the river’s gauges on the Environment Agency service — Nene at Orton Sluice and Nene at Wansford — or use our own live river levels map.
• Screen a location. Try our free flood risk map, and for drainage the drainage calculators and BRE 365 infiltration calculator.
• Flood warnings. Sign up for Environment Agency flood warnings and call Floodline on 0345 988 1188.
• In a flood emergency. Call 999 if life is in danger, and 105 for power cuts.

River Nene flood risk: your questions answered