Flood Risk & Drainage Requirements for East Hertfordshire District Council

East Hertfordshire District Council still decides flood and drainage cases under Policies WAT1 and WAT5 of the East Herts District Plan, adopted on 23 October 2018, with Hertfordshire County Council advising on surface water as Lead Local Flood Authority. The requirement that most often surprises applicants sits in the validation checklist: every major application needs a flood risk assessment, even on a site wholly in Flood Zone 1.

Below are the six water policies of the District Plan, what each asks for and what our reports do about it; the new 2026 Strategic Flood Risk Assessment; the triggers East Herts Council uses at validation; and the county's drainage standards, which now follow the 2025 National Standards. To talk an East Herts site through, call 01293 214444 or email enquiries@unda.co.uk. Reports for applications to East Hertfordshire District Council come from Unda Consulting Limited, a CIWEM Business Partner.

District, county and Environment Agency: who decides what in East Herts?

Hertfordshire County Council only advises; its own surface water drainage page says the final decision on a drainage scheme rests with the planning authority. In practice an unresolved county objection can still decide an application. In an appeal decided on 23 October 2026 for land off Chapel Lane, Little Hadham, East Herts had refused permission on drainage alone, relying on the county's advice, and the Inspector allowed the appeal after weighing the scheme against WAT1, WAT3 and WAT5 and noting that it met some, but not all, of the National Standards. Our explainers on what a Lead Local Flood Authority does and how an LLFA objection is resolved cover the two roles in more depth.

Policy WAT1 to WAT6: the East Herts District Plan water policies

Six policies in Chapter 23 of the District Plan carry water, and two of them, WAT1 and WAT5, decide most flood and drainage cases. On its adoption on 23 October 2018 the District Plan replaced all the saved policies of the Local Plan Second Review 2007, including its water policies ENV18 (Water Environment), ENV19 (Development in Areas Liable to Flood), ENV20 (Groundwater Protection) and ENV21 (Surface Water Drainage); WAT4 and WAT6 have no 2007 equivalent. The climate change policies CC1 and CC2 deal with overheating and carbon; the plan places flood risk and drainage in Chapter 23.

Requirements checked November 2026.

How East Herts applies Policy WAT1 (Flood Risk Management)

Policy WAT1 asks every scheme to show it adds no flood risk of any kind, anywhere. Clause II reads: "Development proposals should neither increase the likelihood or intensity of any form of flooding, nor increase the risk to people, property, crops or livestock from such events, both on site and to neighbouring land or further downstream" (District Plan, Chapter 23).

The policy goes further than a flood zone check. Clause I protects the functional floodplain and asks for developed floodplain to return to greenfield where possible; clause III asks for climate change and buffers to watercourses; clause IV applies the sequential test and, for schemes that must pass the exception test, asks them to show they stay safe and operational, follow a strategy of safe evacuation or safely staying in the building, keep key services running and recover quickly.

The supporting text adds that the Environment Agency's latest mapping should be a material consideration, so officers read the current Flood Map for Planning alongside the SFRA. Our assessments map every source the policy names, set floor levels against the 1% AEP flood with climate change, show any floodplain storage lost and replaced, and include an evacuation or refuge plan where clause IV applies. Our guide to the sequential and exception tests explains the national tests WAT1 draws on.

Policy WAT5 (Sustainable Drainage): the district's SuDS rule

Policy WAT5 sets the drainage bar for every scheme, minor ones included. Its first two clauses read: "Development must utilise the most sustainable forms of drainage systems in accordance with the SUDS hierarchy, unless there are practical engineering reasons for not doing so" and "Development should aim to achieve Greenfield run-off rates and ensure that surface water run-off is managed as close to its source as possible" (District Plan, Chapter 23).

The hierarchy WAT5 refers to is Table 23.1 of the plan, which runs from living roofs, ponds and basins, swales and infiltration at the top to tanked storage at the bottom. Clause III asks applicants to "detail how it will be maintained in the long term", and clause IV asks for spare capacity for infrequent severe weather. On a major scheme the county tests the numbers; on a minor one the district reads WAT5 itself, so a lone crate soakaway with no hierarchy reasoning is a weak submission either way. Our drainage strategies work down the hierarchy in order, give the reason each higher option was or was not used, and set out who maintains each feature.

Policy WAT3 (Water Quality and the Water Environment): the 8 metre strip

Policy WAT3 keeps building back from the district's rivers. Clause II asks that "an undeveloped buffer strip at least 8 metres wide should be maintained alongside all main rivers", with a buffer on ordinary watercourses too and a management scheme for each, and clause III resists new culverting (District Plan, Chapter 23). The 2026 SFRA recommends that built development within 8 m of the bank top of a main river, culvert or defence is discouraged. Our layouts and assessments measure that strip from the bank top, or from the landward toe of a defence, before anything else is fixed.

Policy WAT2 (Source Protection Zones) and Policy WAT4 (Efficient Use of Water Resources)

Much of East Herts sits over chalk that supplies drinking water. WAT2 asks for an impact assessment where certain uses sit in a Source Protection Zone, and the list includes "discharge of foul sewage to ground" and "cess pools", so a rural scheme on a package treatment plant or a filling station needs groundwater evidence. WAT4 sets the 110 litres per head per day target for new homes (District Plan, Chapter 23). Where infiltration is proposed in a protection zone, our strategies check the zone first and say whether deep soakaways are suitable at all.

Policy WAT6 (Wastewater Infrastructure): foul capacity before occupation

Policy WAT6 states that "Development proposals must ensure that adequate wastewater infrastructure capacity is available in advance of the occupation of development" (District Plan, Chapter 23). The supporting text says the council may ask for appraisals of network capacity and that the requirement is unlikely to apply to minor and householder schemes. For larger schemes our foul drainage work sets out the flows and Thames Water's capacity position, so the point is settled before a condition is needed.

The new East Herts Local Plan and what it means for WAT1 to WAT6

No replacement flood policy exists yet. East Herts Council began its new Local Plan under the reformed system on 15 October 2026, when its Gateway 1 self-assessment was published, after a scoping consultation that ran from 11 June to 10 July 2026. Its timetable, dated 15 October 2026, puts consultation on plan content and evidence from 10 February to 24 March 2027, the proposed plan from 21 February to 17 April 2028, submission on 2 October 2028 and adoption on 2 April 2029, all marked as indicative.

Until then the District Plan 2018 water policies stand, read alongside the August 2026 NPPF. Reorganisation adds uncertainty: on 29 October 2026 the government withdrew its decision to create four unitary councils in Hertfordshire, so no successor council is yet confirmed, and the council's own timetable says reorganisation may affect the programme. Our explainer on reorganisation and flood risk planning sets out what usually carries across to a new council.

What the 2026 East Herts SFRA changes for a site

East Herts now has a new Level 1 Strategic Flood Risk Assessment, prepared by JBA Consulting and issued as revision P03 on 8 September 2026. The council's new Local Plan evidence page lists it as endorsed in October 2026, with appendices on the sequential test, the functional floodplain and groundwater emergence. It replaces the 2016 Level 1 and 2 study for plan-making, so a report that still cites only the 2016 maps is out of date.

• Flood Zone 3b. The SFRA draws its own functional floodplain (Appendix D) and asks developers to consult the council on how it was derived; its recommendations rule out development there.
• Climate change mapping. It uses the Environment Agency's surface water climate change extents published on 28 May 2026, and its recommendations ask for no residential development in Flood Zone 3a or the modelled 1% AEP plus climate change extent.
• Small watercourses. Flood zones do not cover catchments under 3 km², so a Flood Zone 1 site beside a ditch or brook may still be at river risk; the SFRA says so in terms.
• Surface water. High risk is concentrated in Bishop's Stortford, Hertford, Ware and Buntingford, with Sawbridgeworth less affected.
• No critical drainage areas. There are no Environment Agency critical drainage areas and no locally designated ones in the district.
• Emergency plans. Every new development in a flood risk area should come with an emergency plan proportionate to the risk.

For an East Herts sequential test, Appendix B of the 2026 study sets out the district's sequential test guidance. If the term is new to you, start with what a strategic flood risk assessment is.

Validation triggers in East Herts: FRA, sequential test or drainage strategy?

East Herts validates against the Joint Validation Checklist it shares with Hertfordshire County Council, Version 3, dated 5 December 2024 and linked from the council's Make a Planning Application page. Item L12 sets the flood risk assessment triggers and item L32 the drainage strategy. The checklist still quotes older NPPF paragraph numbers, but its triggers are what the validation officer applies.

An applicant who relies on the national triggers alone will send a major Flood Zone 1 scheme in without the assessment the checklist requires. The Sustainability SPD, adopted on 2 March 2021, says that "All major development (10 dwellings and over 1000sqm of non-residential floorspace) must submit a Flood Risk Assessment, which includes details of SUDs", and checklist item L32 asks for infiltration testing on all sites, plus written agreement from the sewerage company where a sewer is the only outfall. The commonest gaps that stop the clock are listed in our article on applications invalidated for missing flood or drainage documents.

Hertfordshire County Council's drainage standards in East Herts

Hertfordshire County Council now tests drainage against the national standards rather than its own older policies. Its surface water drainage page says the SuDS policies in its 2019 flood strategy are "largely superseded by the National Standards for SuDS 2025" and that "Planning applications must now comply" with Defra's National Standards for Sustainable Drainage Systems, published on 19 June 2025. The county's earlier summary guidance for developers no longer appears on that page.

For a major application the county expects the Surface Water Drainage Statement proforma completed in full, and its LLFA validation list adds a topographic survey, ground investigation with seasonally high groundwater levels, FEH 13 rainfall, critical storm results for the 3.33% and 1% AEP events with climate change, and evidence that 1% AEP plus climate change flooding stays inside the site. The proforma dates from 2023, before the national standards, and its second storage option discharges at 2 l/s/ha, stricter than the National Standards, which never set the allowable 50% AEP rate below 3 l/s/ha, so our strategies state which figure they size to and why.

The county's climate change note on the same page dates from November 2017 and quotes the older 2016 allowances; the current figures are the Environment Agency's peak rainfall allowances, which the 2026 SFRA reproduces for the Upper Lee and London catchments. Our ground conditions and soakaway map, the BRE 365 infiltration rate calculator and the drainage calculators give a first read on a site before BRE 365 testing, and our pages on the 2025 National Standards for sustainable drainage and the SuDS proforma explain both documents. The county also runs a paid Surface Water Drainage Advisory Service before submission, and warns of a four to six week lead-in for meetings.

National policy behind the East Herts requirements

East Herts applies its District Plan alongside Chapter 18 of the August 2026 NPPF. F4 says when a site-specific flood risk assessment is needed, F5 and F6 set the sequential and exception tests, F7 requires development to be safe for its lifetime, and F8 asks for SuDS designed to the National Standards, taking account of the Lead Local Flood Authority's advice on major schemes. The government's flood risk and coastal change guidance, last updated in September 2025, sets out the method.

Locally the bar is higher in two places: the validation checklist and the Sustainability SPD require a flood risk assessment with every major application whatever its flood zone, and WAT3 keeps an 8 metre buffer to main rivers. Our guide to the NPPF on flood risk sets out the national tests in full, and our NPPF guidance service applies them to a specific site.

Rivers, surface water and groundwater across East Herts

Most river flood risk in the district comes from the River Lea, which runs through Hertford, Ware, Great Amwell and Stanstead St Margarets. Its tributaries the Mimram, Beane, Rib and Ash mostly keep flood water in channel, while the Stort, which forms the eastern boundary, puts parts of Bishop's Stortford and Sawbridgeworth at risk; the Canal & River Trust records twelve overtopping incidents on the Stort Navigation in the district (2026 SFRA).

Thames Water's 2025 records put the most sewer flooding incidents in Sawbridgeworth ward and Hertford Castle ward, with none in 20 of the 32 wards. The SFRA's groundwater emergence map shows water at or near the surface in parts of the Lea valley and around Buntingford, and four reservoirs in the district carry a residual breach risk that a site assessment has to consider.

Town by town, our area pages cover flood risk in Hertford and Ware, with the Hertfordshire overview for the county. Check a site's flood zone on our flood risk map and follow the Lea, Stort and Beane on the live river levels map. Requirements for the other councils on our list sit on the local authorities hub.

Reports for an application to East Herts Council

We have prepared reports for applications to East Herts Council. The list ties each of our services to the District Plan policy, checklist item or county standard that calls for it. Three of them are often confused: the flood risk assessment asks whether the site is safe, the sequential or exception test whether the scheme belongs there at all, and the drainage strategy what happens to the rain that falls on it.

• All sources. WAT1 covers "any form of flooding", from the Lea to sewers and groundwater: our flood risk assessment service covers each.
• Majors and flood zones. The checklist wants an assessment with every major scheme and in Flood Zones 2 and 3: a flood risk assessment for planning.
• Buying near the Lea or Stort. Searches flag homes in the Hertford, Ware and Stort valley floodplain: a flood risk survey for property purchase answers the lender before exchange.
• Location justified. WAT1 clause IV applies the sequential test, and the exception test where national policy requires it: the sequential and exception test.
• Every scheme. WAT5 asks even minor schemes to follow the SuDS hierarchy and aim for greenfield rates: a drainage strategy.
• Major applications. Hertfordshire's proforma and the 2025 National Standards set the rates and storage: a surface water drainage strategy.
• After permission. Drainage conditions ask for the final scheme and its maintenance: discharge of drainage conditions.
• Foul capacity. WAT6 needs wastewater capacity before occupation, and WAT2 covers foul discharge to ground: a foul drainage strategy.
• Chalk and gravels. The SFRA maps groundwater emergence in the Lea valley and around Buntingford: a groundwater assessment.
• Ditches and brooks. Flood zones leave out catchments under 3 km²: flood modelling where national mapping stops.
• Safe refuge. WAT1 asks exception-test schemes for an evacuation or refuge strategy: a flood warning and evacuation plan.
• National tests. F4 to F8 of the August 2026 NPPF apply on top of WAT1 and WAT5: NPPF guidance and advice.

East Herts flood and drainage: applicants' questions