Flood Risk Assessment in Peterborough

A flood risk assessment in Peterborough usually starts with the River Nene, which runs through the city centre past Woodston and the Embankment and whose floods depend on the Dog-in-a-Doublet sluice and the Whittlesey Washes downstream. North of the centre the Peterborough Brooks carry their own warnings, and on the Oxford Clay that underlies most of the city a heavy storm can flood streets well away from any river. We prepare flood risk assessments in Peterborough for planning applications, house purchases, mortgages and insurance, and write sequential and exception tests and surface water drainage strategies alongside them.

Peterborough, Cambridgeshire, is taken here as the ONS built-up area: the city centre and Fengate, Woodston and Fletton south of the river, Stanground, the Orton townships and Hampton to the south, Bretton and Westwood to the west, and Werrington, Paston, Gunthorpe and Dogsthorpe to the north, across the PE1, PE2, PE3 and PE4 postcode districts, with Hampton's newer streets under PE7. The city sits in the ceremonial county covered by our Cambridgeshire page, but Peterborough City Council is a unitary authority, so it is both the planning authority and the lead local flood authority here, and Cambridgeshire County Council has no say on a city site's drainage.

At Easter 1998 the Nene flooded 18 homes in Peterborough, but the larger toll came two days later: on Easter Sunday 100 homes flooded from the Thorpe Meadows watercourse, a small main river that could not empty into a Nene running at its peak.

To talk through a Peterborough site with one of our flood risk consultants, call 01293 214444 or email enquiries@unda.co.uk. Reports for sites in Peterborough come from Unda Consulting Limited, a CIWEM Business Partner.

The Nene, the Peterborough Brooks and the city's smaller main rivers

Peterborough straddles two catchments. The southern half drains to the Nene; the northern suburbs drain through the Peterborough Brooks to the Welland. The council's flood strategy lists 17 main rivers within its area, several of them short urban streams that the Environment Agency took over in 2004 and 2005 because of the damage they had done. Five groups matter most for sites inside the city.

The Nene itself has a page of its own on our site covering its course from Northamptonshire to the Wash, the River Nene and its flood history. For a site in the city the relevant Environment Agency warning areas are Areas near the River Nene in Peterborough, which names Woodston and Thorpe Meadows, the wider area at risk from the Nene and the Peterborough Brooks area for the northern estates. Our live river levels map shows the gauges on both rivers and any warning in force.

What the Orton Sluice gauge says about the Nene in the city

The Environment Agency's River Nene level at Orton Sluice is the gauge most Peterborough riverside sites are judged against. It has recorded since 2002, and its readings give a working scale for the river through the city:

1. 0.91 m to 2.26 m. The normal range at Orton Sluice.
2. Above 2.26 m. Low-lying land beside the river may flood.
3. 3.08 m on 27 November 2012. The highest level the station has recorded.

The gauge is a guide to how the river behaves, and a planning assessment goes further. The flood zones on the Flood Map for Planning come from modelled floods with a 1% and 0.1% annual chance, and the defended Nene corridor is mapped as if the embankments were not there, so a riverside site in Woodston or by the Embankment is assessed against modelled levels with climate change added, not against the 2012 peak.

Screen an address from Werrington to Hampton

Enter a postcode in the interactive map below to check a Peterborough address against Environment Agency data for rivers, surface water and reservoirs, or open our full flood risk map for anywhere in England. The coral line is the ONS built-up area, so the Ortons, Hampton, Werrington and the city centre fall inside it, while Eye, Thorney and the newest streets at Great Haddon and Hampton Leys sit outside it, though the same council and the same flood evidence cover them. Yaxley, south of Hampton, lies in Huntingdonshire.

Dog-in-a-Doublet, the Whittlesey Washes and the risk behind the banks

The Nene stops being tidal about 8 km east of the city centre, at the Dog-in-a-Doublet sluice. When a high tide closes the sluice gates while the river is in flood, the Nene cannot drain to the Wash, and the water is turned into the Whittlesey Washes instead. That arrangement is what keeps a big Nene flood out of the city, and it is also why a site behind the banks still has a residual risk to assess.

• The sluice. Dog-in-a-Doublet is the Nene's tidal limit. Downstream the river runs between tidal embankments with a 0.67% standard of protection; upstream it is a fluvial river through Peterborough.
• The washes. The Whittlesey Washes, also called the Nene Washes, cover about 1,450 hectares, run for about 20 km and are up to 1.4 km wide. Floodwater enters through Stanground Sluice and is let back into the Nene at Ring's End once the tide and the river fall. They are designed to a 0.5% annual chance, and are also a Special Protection Area and Ramsar wetland.
• The South Barrier Bank. This 18 km reservoir bank runs from Stanground to Ring's End. The Environment Agency spent £26 million strengthening it from 2013, protecting homes, roads, railways and more than 8,000 hectares of farmland. The council puts its standard of protection at 0.1%.
• The roads that close. North Bank Road beside the washes, maintained by the city council, and the B1040 from Thorney to Whittlesey each have a flood warning area of their own and are shut when the washes fill.

The council's strategy describes the worst case for Peterborough as heavy local rain, several days of high Nene flows and a North Sea surge that keeps the sluice shut, close to what happened in 1998. Once the washes are full, the river can start to overtop in places through the city. That is the scenario a residual flood risk assessment tests for a defended site, with floor levels and an escape route set accordingly. Below the sluice the Nene is tidal all the way to Wisbech, where the risk comes from the sea as much as the river.

Peterborough floods on record since 1947

Peterborough's flood history has two strands: the Nene in long wet spells, and short summer storms that overwhelm drains and brooks in the estates. The dates below come from the council's strategy, the Environment Agency's gauge record and the local press.

1. March 1947. Snow thawed on frozen ground in the 1947 floods. On 19 March the Nene at Town Bridge was reported 2.4 m above its average level, and two days later a breach at Cowbit Washes flooded the north of the Peterborough area as far as land north of Thorney and Eye Green.
2. July 1986. An intense summer storm flooded from the Werrington Brook, Brook Drain and their tributaries.
3. 1997. Heavy rain caused flooding from the Marholm Brook.
4. Easter 1998. A stationary band of rain from 8 to 10 April pushed the Nene to about 200 cubic metres a second at Wansford. Eighteen homes flooded from the Nene, then 100 from the Thorpe Meadows watercourse on Easter Sunday, and families in Riverside Gardens and Thorpe Meadows were evacuated as Thorpe Road went under.
5. August 2011. An intense summer storm caused flooding across the city.
6. 27 November 2012. The Nene at Orton Sluice reached 3.08 m, the highest level on the gauge's record.
7. December 2020. Prolonged rain on saturated ground. After Storm Bella the Nene broke its bank upstream of Orton Mere lock and North Bank Road stayed closed under a flood warning.
8. 9 July 2021. Up to 92 mm of rain fell in four hours. Homes flooded in a band from West Town across to Eye as drains filled and local watercourses overtopped.
9. November 2024. During Storm Bert the Environment Agency warned for Town Bridge and Hartley Avenue, the riverside paths by the Key Theatre and Rivergate were cut off, and the Lakeside area at Ferry Meadows was closed.

The Environment Agency's 2017 preliminary assessment found no surface water Flood Risk Area of national significance in Peterborough, yet three of the city-wide floods in that list were summer downpours rather than river floods. A planning assessment in the northern estates therefore looks hard at overland flow routes and the brooks, while one near the river starts from the Nene's modelled levels.

Oxford Clay, western limestone and combined sewers under the city

What happens to rain on a Peterborough site depends on the ground beneath it and the sewer it would drain to. The British Geological Survey maps most of the city on Kellaways and Oxford Clay mudstones, the same clay that fed Fletton's brickworks, with limestone of the Great Oolite Group coming in to the west around Bretton. The table below draws on the council's flood strategy and drainage guidance.

The council's Flood and Water Management SPD puts infiltration first and a sewer last, holds greenfield sites to the greenfield runoff rate, refuses new connections to combined or foul sewers, and asks for storage sized to the 1% annual chance storm with a 40% allowance for heavier rainfall unless the council agrees otherwise. It also allows urban creep of up to 10% on denser housing. A BRE 365 infiltration test settles whether a soakaway is viable, and our ground conditions and soakaway map gives an early read on a site before any trial pit is dug.

Which flood policies apply to a planning application in Peterborough?

Peterborough City Council decides the application and, as lead local flood authority, reviews the drainage itself. The Environment Agency comments on sites by the Nene and the other main rivers, and in the fens a drainage board may need to consent works near its drains. An applicant has five documents to answer.

The national rules for a Peterborough application are in chapter 18 of the August 2026 NPPF: policy F4 sets when an assessment is needed, F5 and F6 carry the sequential and exception tests, and F8 expects development to follow the 2025 National Standards for sustainable drainage. The council's critical drainage area map is being redrawn and is not published at present, so a Flood Zone 1 site's surface water exposure is best checked through the assessment itself. Works in or beside a watercourse need consent that a planning permission does not give, and in the fens that consent comes from an internal drainage board. The council also says it will not normally permit culverting.

Showground, Middleholme and Red Brick Farm: where the new plan flags flood risk

The Proposed Submission Local Plan provides for 20,825 homes and about 196 hectares of employment land between 2024 and 2043. Most growth continues at the urban extensions of Hampton, Paston Reserve and Great Haddon, with Norwood and the East of England Showground proposed as new ones. Several site policies name flood risk directly:

• East of England Showground (LP54). About 2,070 homes near Alwalton, with a site-specific flood risk assessment required to deal with flood risk and safety, "particularly to the south of the site", and its effects on and off site.
• Middleholme (LP52). A city-centre housing site where the council wants homes placed on the land at lowest probability of flooding and mitigation that favours nature-based measures, set out before any permission is granted.
• Red Brick Farm, Fengate (LP61). A 63-hectare employment site off Edgerley Drain Road, part of it in Flood Zone 3, where only about 30 hectares are expected to be developable once flood mitigation is allowed for.
• Land north-east of Stanground (LP61.5). A new 115.5-hectare strategic employment allocation on the fen edge, to be planned through a masterplan.
• The Embankment and the Nene Valley (LP40 and LP39). The Embankment north of the river stays largely open, and the Nene Valley policy refuses development that would increase flood risk or weaken the flood defences.

Hampton, built on brickworks land that closed in the 1980s, drains through several large lakes that its master developer manages. A site the plan does not allocate gets no such network: it has to find its own outfall and storage, and pass the sequential test if any part lies in Flood Zone 2 or 3.

From a Woodston extension to a Fengate warehouse: when a flood risk assessment in Peterborough is needed

Whether a Peterborough proposal needs an assessment turns on its flood zone, its size and what it is for. Policy LP30 and the SPD use the same tests as national policy, with the council adding sites in Flood Zone 1 that have critical drainage problems:

Where a sequential test is required, the area of search and the sites counted as reasonably available decide the outcome, so settle both before the layout is fixed; our page on testing alternative sites covers how that works. A Flood Zone 1 site at risk only from surface water can be spared the test under policy F5 if its assessment shows the scheme will be safe without raising risk elsewhere, as our note on the surface water exemption explains.

Reports we write for riverside, clay and fen-edge sites in Peterborough

A house buyer by the Embankment, a householder in Werrington and the promoter of an employment site at Fengate each need a different report. Our consultants are chartered, and a senior consultant checks and signs off every one.

• Applications by the Nene and the brooks. Homes and commercial schemes in the Nene corridor, by the Thorpe Meadows watercourse or along the Peterborough Brooks need a flood risk assessment for planning that answers Policy LP32 now and LP30 once adopted.
• River, rain and drains on one site. A flood risk assessment for a Peterborough site weighs the Nene and its washes, the brooks, storms on the clay and the city-centre sewers together.
• Before exchange near the river. Searches flag the Woodston and Thorpe Meadows streets, and a flood risk survey for property purchase looks at the actual house and its floor level.
• Homes in Flood Zones 2 and 3. New housing in the Nene or brook flood zones, and allocations with land in Flood Zone 3, need the sequential and exception test before an application can be approved.
• Drainage evidence for the LLFA. The city council reviews drainage itself as lead local flood authority, so most Peterborough applications need drainage strategy work sized to the SPD's rules.
• Storage on the clay. A surface water drainage strategy tests the ground, and on the Oxford Clay usually settles on attenuation and a greenfield-rate discharge to a watercourse or a board drain.
• Clearing the condition. Where a Peterborough permission has a drainage condition attached, discharge of drainage conditions supplies the calculations, details and maintenance plan the council asks for.
• Levels by the Nene and its tributaries. Where national mapping is too coarse for a site by the Nene, the Thorpe Meadows watercourse or Stanground Lode, flood modelling sets the design flood level.
• A route out when the river rises. Five Environment Agency warning areas cover the Nene, the brooks and the washes roads, and a flood warning and evacuation plan ties a riverside scheme to them.
• Homes with a flood record. After 100 homes flooded from the Thorpe Meadows watercourse in 1998 and the July 2021 storm from West Town to Eye, a flood risk assessment for insurance gives an insurer evidence for one address.
• Limestone and floodplain gravels. The council notes aquifers and springs in the limestone west of the city and groundwater rising through the Nene gravels, which a groundwater flood risk assessment examines for basements and soakaways.
• Combined sewers in the centre. Policy LP30 bars new combined sewers and limits connections to existing ones, so a city-centre or station quarter scheme often needs a foul drainage strategy as well.
• Premises on the eastern fen edge. Fengate has flooded from the Racecourse Drain, and a business continuity flood risk assessment plans how a firm there keeps running through a flood.
• New employment land. Red Brick Farm and the 115.5-hectare allocation north-east of Stanground will bring commercial buildings, and a BREEAM flood risk assessment covers the Pol 03 credits.
• Land before an offer. With half of Red Brick Farm set aside for flood mitigation and flood safety written into the Showground policy, a flood risk feasibility study shows early how much of a site can be built on.

Peterborough flood contacts, from the council drainage team to the fen boards

If floodwater puts anyone in Peterborough in danger, ring 999; for a power cut, ring 105. Otherwise each organisation below looks after one part of the city's flood risk:

Upstream, the Nene runs through Northamptonshire; the Welland and the Deepings lie across the boundary in Lincolnshire. Other places are in our full list of areas.

Questions about Peterborough sites, flooding and planning

For a riverside plot in Woodston, a house in the Ortons or employment land at Fengate, ring 01293 214444 or email enquiries@unda.co.uk and one of the consultants at Unda Consulting Limited will talk the site through with you.