Flood Risk & Drainage Requirements for South Holland District Council

South Holland District Council applies Policy 4 of the South East Lincolnshire Local Plan 2011-2036, adopted on 8 March 2019, to any site in Flood Zone 2 or 3 or shown at risk in a breach of the defences, with Lincolnshire County Council advising on drainage as Lead Local Flood Authority. The rule that most often catches applicants: a site the plan did not allocate must pass a sequential test whose search can reach every settlement in the district, narrowed to the scheme's catchment under national policy, and its 2019 local list asks every major scheme for a whole-site surface water drainage strategy at validation.

Here we set out what South Holland District Council, Lincolnshire County Council, the Environment Agency and the drainage boards each require on flood risk and drainage, and how our reports answer each requirement. The page goes policy by policy through the Local Plan, then the South East Lincolnshire SFRA and its 2016 South Holland update, the local list, the county's drainage standards and the boards' consents. To discuss a site in the district, call 01293 214444 or email enquiries@unda.co.uk.

Allocated or windfall: how South Holland runs the sequential test

Policy 4 treats allocated and unallocated land differently, and the gap matters most on windfall sites. The plan's authors ran the sequential test inside each settlement when they chose the allocations, because so much of the district is in Flood Zone 3 that a district-wide search would have pushed housing to isolated land away from the towns. Paragraph 3.5.4 of the Local Plan therefore treats allocated sites as having passed. Paragraph 3.5.5 then says that "future speculative and windfall proposals will be required to use a Borough or District wide search area". Policy 4(1) sets that search "within the defined settlement boundaries, unless local circumstances relating to the catchment area for the development justify a reduced search area".

The council's planning policy page tells applicants to run the test on the SFRA's 2115 mapping, the 1% river and 0.5% tidal scenario, for both hazard and depth, and points to pages 12 and 13 of the SFRA for the method. Since August 2026, NPPF policy F5 caps every sequential test: the search area "should not be greater than the anticipated catchment of the development", judged by its likely occupiers or users. Read together, the district-wide area is the most a South Holland search can cover, and it narrows wherever the scheme's catchment is smaller. Our sequential and exception test reports set the search area, list the reasonably available sites within it and compare their hazard and depth bands with the application site.

District council, county, Environment Agency and the fen boards: who decides what in South Holland

Five internal drainage boards serve the district, according to the council's own summary: South Holland, Welland and Deepings, Black Sluice, North Level District and King's Lynn, so which one consents depends on where the site drains. The Welland and Deepings board covers 32,400 hectares from Peterborough and Stamford up to Fosdyke and Kirton, including the Spalding area. The South Holland board, run by the Water Management Alliance, manages about 702 km of watercourse and 17 pumping stations across roughly 38,468 hectares. Outside the boards' districts, Lincolnshire County Council regulates ordinary watercourses itself, and its flood risk management page says the boards act as its agents there. For the bigger picture, see our explainers on why internal drainage boards matter for planning, the Lead Local Flood Authority and who is responsible for managing flood risk in England.

The Local Plan, the SFRA and the county's standards are shared with Boston Borough Council, and the county's drainage regime with East Lindsey District Council. Our council guides hub lists every authority we cover.

Policy 4 and six more South East Lincolnshire policies that apply in South Holland

The shared Local Plan replaced the South Holland Local Plan (2006) on 8 March 2019, deleting all of its saved policies. Its Appendix 2 lists Policy SG11 (Sustainable Urban Drainage Systems) among those replaced by Policy 3, and Policy SG12 (Sewerage and Development) among those replaced by Policy 2. The flood and drainage policies now in force:

Requirements checked November 2026.

How South Holland applies Policy 4 (Approach to Flood Risk)

Policy 4 lets development go ahead on land at risk of flooding only if it passes the sequential test, passes the exception test where national policy calls for one, and comes with a site-specific flood risk assessment. Land at risk means Flood Zones 2 and 3, or land "at risk during a breach or overtopping scenario as shown on the flood hazard and depths maps in the Strategic Flood Risk Assessment" (Local Plan, March 2019). The assessment has to cover every source and the effect of climate change, propose resistance and resilience measures "maximising the use of passive resistance measures", and incorporate SuDS unless that is not technically feasible. It must also show that "adequate foul water treatment and disposal already exists or can be provided in time to serve the development".

The sequential test is waived for allocated sites, minor development and changes of use, except a change of use to a caravan, camping or chalet site or to a mobile or park home site. Several clauses matter on the fen. Every flood zone, and any Flood Zone 1 site over a hectare, must show its surface water will not raise flood risk for third parties. Self-contained ground floor flats created by a change of use in the danger for some, most or all bands are not supported. Caravans and park homes for permanent living are not permitted in areas at risk, and holiday caravan, chalet, log cabin, camping and touring sites at tidal risk may not open "between 1st November in any one year and the 14th March in the succeeding year".

Officers and the Environment Agency look first at the sequential case on a windfall site, then at the breach depth at the building, the floor level and the escape route. Our flood risk assessments read the 2115 depth and hazard maps for the plot, set floor levels and resilience to the SFRA's standing advice, and attach a warning and evacuation plan where the depth or the use calls for one.

Policy 15 (Vernatts Sustainable Urban Extension): drainage for the Spalding extension

Policy 15 allocates the Vernatts extension on land north of the Vernatt's Drain on Spalding's edge. Its clauses x and xi require it to "incorporate a foul drainage strategy for the Sustainable Urban Extension as a whole, and for each phase" and "a comprehensive Sustainable Drainage System to manage surface water drainage and safeguard against any increased flood risk". A phase that arrives without showing how it fits the site-wide drainage invites an objection. Our phase strategies take the site-wide outfall and storage as their starting point and show each parcel's share of it.

Policy 16 (Holbeach West Sustainable Urban Extension): a flood management scheme first

Policy 16 asks the Holbeach West extension for "a flood management scheme for fluvial and surface water run off" and a foul drainage strategy for the extension as a whole and for each phase. The allocation is treated as sequentially tested, but the plan still expects site-specific assessment to show the development is safe if defence infrastructure fails. For a Holbeach West phase we prepare the flood risk assessment and drainage strategy against the agreed site-wide flood management scheme, so the phase cannot be read as undermining it.

Policy 31 (Climate Change and Renewable and Low Carbon Energy) and SuDS on major schemes

Clause A2 of Policy 31 asks every proposal to adopt "the sequential approach and Exception Test to flood-risk" and to incorporate flood mitigation, "including SuDS schemes for all 'Major' applications". The plan's supporting text on flood risk repeats that major developments are expected to include SuDS "as standard". The district's local list asks for that drainage strategy at validation, which is why our surface water drainage strategies for major schemes follow the county's level 2 or level 3 format from the start.

Policy 3 (Design of New Development): floor levels and resilience

Where relevant to the proposal, Policy 3 asks applicants to show how they will secure "the mitigation of flood risk through flood-resistant and flood-resilient design and sustainable drainage systems (SuDS)". On a site with a modelled breach depth, that is where the SFRA's standing advice meets the drawings. Our assessments give the architect the finished floor level, the resilient construction and the level for services, rather than a general recommendation.

Policy 2 (Development Management): small schemes still need a drainage answer

Policy 2 names "sustainable drainage and flood risk" as one of the matters every application must satisfy. On a single dwelling or an agricultural building in the fens, the question is usually whether runoff can go to a dyke and whether the board will allow it. We set that out in a short drainage statement, so the council's officers have an answer without asking for more.

Policy 30 (Pollution): runoff into the Wash's drains

Policy 30 resists development that would cause unacceptable harm to "surface and groundwater quality", once mitigation is counted. Runoff from yards, roads and parking in South Holland reaches pumped drains that discharge to the Welland, the Nene and the Wash, so the treatment train is part of the drainage case. Our strategies show the treatment each surface receives before it leaves the site.

The new Boston and South Holland Joint Local Plan

The councils have started a replacement plan, but no draft exists yet. On 27 May 2026 the Joint Strategic Planning Committee endorsed work on a new Joint Local Plan for Boston and South Holland, running to 2044 under the 2026 plan-making system, with a notice of intention to commence due by December 2026. The project initiation document plans consultation on a vision and strategy in July to September 2027, submission in 2029 and adoption in October 2029, and lists a new SFRA among its evidence. East Lindsey is preparing its own plan. Until the new plan advances, Policy 4 and the 2017 SFRA decide South Holland cases.

Lincolnshire's local government reorganisation, which in July 2026 would have placed South Holland in a new Lincolnshire unitary council, was paused for review on 7 September 2026. Our note on reorganisation and flood risk planning covers what tends to transfer.

What South Holland's 2019 local list asks for on flood risk and drainage

Unlike Boston, South Holland still applies a formal local validation list. Its Local List for All Applications (2019), published on the council's validation page with a separate householder list, sets out four flood and drainage items:

• Flood risk assessment. Required in Flood Zone 2 or 3, "including minor development and change of use", and on sites of a hectare or more in Flood Zone 1. Smaller sites need one where other sources such as surface water drains or reservoirs could affect them, or where the Environment Agency has flagged critical drainage problems.
• SuDS and safe access. The assessment should examine SuDS for the surface water strategy and address safe access in areas at risk, and the site-specific drainage requirements "should be agreed with Lincolnshire County Council Highways at pre-application stage".
• Surface water drainage strategy. "Required for all major developments", using the national definition of major development (10 or more homes, 1,000 m2 of new floorspace or a 1 ha site, or 0.5 ha for housing where numbers are unknown): a level 2 outline whole-site strategy with a level 2 ground investigation for outline applications, and a level 3 detailed whole-site strategy with a level 3 geotechnical report for full and reserved matters applications, both to the county's design approach.
• Foul drainage. A foul drainage assessment where trade waste or sewage is involved; the FDA1 form, with the reasons, where a site cannot connect to the public sewer.

The list predates the August 2026 NPPF and cites the older guidance, but its requirements still apply at registration. A major application without its whole-site drainage strategy can be held at validation for that gap alone. Our note on applications invalidated on flood and drainage grounds covers the other usual gaps.

Washes, sea banks and fen villages: which South Holland schemes need which report

Chapter 18 of the NPPF sets the national triggers, Policy 4 adds the SFRA breach maps, and the local list decides what must arrive with the form. A postcode's national flood zone shows on our flood risk map.

The SFRA, the 2016 South Holland modelling and the functional floodplain

The district relies on the joint South East Lincolnshire SFRA, version 6, dated December 2017. It records that about 74% of South Holland lies in the floodplain, 68% in Flood Zone 3 and 6% in Flood Zone 2, putting 29,922 homes and 1,296 commercial properties at risk. The council publishes the SFRA's hazard mapping and depth mapping for the district, and the SFRA's standing advice matrix (Appendix C, draft version 4) sets floor levels from the 2115 depth, with single storey schemes tested against the 0.1% event.

The 2017 SFRA identifies functional floodplain, Flood Zone 3b, in South Holland as the designated flood storage of the Crowland and Cowbit Washes and the Surfleet Reservoir. It used the older threshold of a 5% (1 in 20) annual chance or land designed to flood; Annex F of the NPPF now normally draws Zone 3b at a 3.3% (1 in 30) or greater annual probability, so our assessments check whether land outside the mapped storage areas meets the current definition. A further 2016 update of the South Holland SFRA, a modelling note by Royal HaskoningDHV dated 28 February 2017, added breach and overtopping modelling at Surfleet and breaching between Crowland and Cowbit. Both studies predate the 2022 Environment Agency climate change allowances, so our assessments test their levels against the current allowances. Our guide to strategic flood risk assessments explains how the council uses them.

Lincolnshire County Council's drainage rules and the South Holland drainage board

For surface water, Lincolnshire County Council works from its 2021 design approach for development roads and sustainable drainage, the document the local list cites for the level 2 and level 3 strategies. It also publishes a SuDS design and evaluation guide written in 2018 with other authorities. No county statement adopting the June 2025 National Standards for Sustainable Drainage was found, although NPPF policy F8 asks for SuDS designed to them. The county's 2021 rules:

• Peak rate, greenfield. The 1 in 1 and 1 in 100 year peaks must never exceed the greenfield peak for the same event (standard S2).
• Peak rate, previously developed. As near greenfield as reasonably practicable and never above the pre-development rate (S3).
• Allowances. Rainfall intensity raised by 40%, or by 25% where sensitivity testing at 40% shows no unacceptable risk, with 10% added for urban creep (county design approach, 2021).
• Performance. No flooding of the site in a 1 in 30 year storm (S7) and none in buildings in a 1 in 100 year storm (S8); storage empties within 48 hours.
• Soakaways. Pit tests repeated three times, worst result used, no borehole tests; the base of the SuDS at least 1 metre above the highest recorded groundwater.
• Receiving water. No surface water to a foul sewer; the county records typical board pump discharge of 1.4 l/s/ha in the fens.

Few South Holland sites can soak away. The silt and peat soils sit over a high water table, so most sites drain by gravity to a dyke and then by pump to the river. So in practice the board sets the discharge rate. Whichever board covers the site, whether the South Holland drainage board, Welland and Deepings, Black Sluice, North Level District or King's Lynn, consents discharges under its byelaws, separately from planning, and can refuse after permission. Our drainage strategies confirm the outfall and the board's likely rate early, size storage to the county's allowances, and use the ground conditions and soakaway map, the BRE 365 calculator and our drainage calculators for early checks. The SuDS hierarchy and our note on overcoming an LLFA objection explain the reasoning the county applies.

National policy that sits behind South Holland's requirements

South Holland reads Policy 4 with Chapter 18 of the National Planning Policy Framework, published on 17 August 2026. F4 decides when a site-specific assessment is needed, including sites shown at risk from any source in an SFRA. F5 governs the sequential test, its exemptions and its catchment-based search area, and F6 the exception test in Flood Zones 2, 3a and 3b. F7 requires development to be safe for its lifetime, with residual risk managed and safe access and escape. F8 asks for SuDS designed to the National Standards and for the Lead Local Flood Authority's advice on major schemes. The government revised its flood risk and coastal change guidance, the Planning Practice Guidance that explains these tests, on 17 September 2025.

Our articles on the August 2026 NPPF changes for flood risk and drainage, the September 2025 guidance update and climate change allowances set out the national position in detail.

The Welland, the tidal Nene and the pumped fen: South Holland's flood risk in brief

The Welland runs through Spalding between raised banks and becomes tidal at Fulney Lock below the town; the Coronation Channel, built after the 1947 floods, carries its flood water around the centre. The Glen joins it at Surfleet. Our area page on flood risk assessment in Spalding covers the town, and our Lincolnshire page the county. In the east, the tidal River Nene reaches the Wash at Sutton Bridge.

Short, intense rain is the other hazard on land this flat. On 16 and 17 August 2022 the Welland and Deepings board's Surfleet gauge recorded 136 mm, its highest daily total, with 110 mm falling in four hours overnight. Behind the banks, residual risk from a breach or a pump failure stays with every site, and the long-term pressure on the fen system is the subject of our piece on Fens 2100+. River levels are on our live river levels map.

Our reports for South Holland District Council applications

Each report below answers a policy, a local list item or a county standard. A flood risk assessment shows the site is safe, a sequential or exception test shows why the scheme belongs on this site, and a drainage strategy shows where the rain goes and at what rate; South Holland often needs all three.

• Every source. Policy 4 wants the risk from all sources with climate change, from the sea banks to the dykes: our flood risk assessment service covers them.
• At registration. The 2019 local list asks for an assessment in Flood Zones 2 and 3 even on minor schemes and changes of use: a flood risk assessment for planning meets it.
• Homes behind the banks. Searches on fen properties often return high flood risk: a flood risk survey for property purchase looks at the building and its floor levels.
• District-wide search. Windfall sites face the Policy 4 search, district-wide at most and capped at the scheme's catchment: our sequential and exception test reports set and justify it.
• Surface water and foul. Policy 4 asks for SuDS and adequate foul disposal, and Policies 15 and 16 for site-wide strategies: a drainage strategy covers both.
• Level 2 or level 3. The local list wants a whole-site strategy on every major application: a surface water drainage strategy in the county's format.
• Conditions. Permissions in the district often condition final drainage details and board consent: we prepare the discharge of drainage conditions package.
• Evacuation. Policy 4 criterion d asks for warning and evacuation procedures where necessary, and tidal holiday sites must close each winter: a flood warning and evacuation plan covers both.
• Local modelling. Where a site falls between the SFRA's breach points or by an unmodelled drain, flood modelling gives the levels the assessment needs.
• Groundwater. The county wants the SuDS base 1 metre above the highest recorded groundwater, a hard test on silt fen: our groundwater assessments establish the level.
• Off-mains sites. The local list asks for the FDA1 form where no sewer is available, common in the fen hamlets: a foul drainage strategy supports it.
• Food and logistics land. Packhouses and distribution sites on the floodplain around Spalding and Holbeach carry the same breach risk as housing: a due diligence flood risk assessment informs a purchase or loan.
• Recorded flooding. About 59 properties in the district flooded in June and July 2007, according to the county's 2011 preliminary flood risk assessment: a flood risk assessment for insurance gives brokers evidence for the property.
• National policy. South Holland decisions apply NPPF Chapter 18 alongside Policy 4: our NPPF guidance and advice explains it for a site.

South Holland flood risk and drainage: applicants' questions

Whether the site is in Spalding, Holbeach, Long Sutton, Crowland or a fen village, call 01293 214444 or email enquiries@unda.co.uk. The chartered consultants at Unda Consulting Limited write the flood risk assessment, the sequential test and the drainage strategy as linked reports. Reports for applications to South Holland District Council come from Unda Consulting Limited, a CIWEM Business Partner.