Flood Risk & Drainage Requirements for Somerset Council

Somerset Council still tests flood risk against the Local Plan of whichever former district a site sits in: Mendip (2014), Sedgemoor (2019), South Somerset (2015), Taunton Deane (2012) or West Somerset (2016). As Lead Local Flood Authority, the same council then reads the drainage strategy against Somerset's own SuDS standards, which hold runoff to the greenfield rate for every design storm and rule out pumped systems. An FRA that quotes another district's policy, or a drainage strategy sized to national figures, does not answer the tests the council and its LLFA apply.

For each of the five legacy plans, this page sets out the policy an application is tested against, quotes its adopted wording and says what our flood risk assessment or drainage strategy contains to meet it. It then covers what a drainage strategy in Somerset has to show under the local SuDS standards, the April 2025 validation checklist, the SFRAs, and the new Somerset Local Plan, which is not expected to be adopted until March 2029. To talk a Somerset site through, call one of our experienced flood risk consultants on 01293 214444 or email enquiries@unda.co.uk.

Somerset Council, the Environment Agency and the drainage boards: who decides what?

Somerset Council has been a unitary authority since 1 April 2023, so one organisation is both the local planning authority and the Lead Local Flood Authority. The two roles sit with different teams. Planning officers weigh the flood risk case against the plan for the former district the site is in, and the LLFA's drainage officers respond as statutory consultee on surface water for major development. Inside Exmoor National Park, the National Park Authority decides planning applications, but Somerset Council is still the LLFA for the Somerset part of the park. Our explainers on what a local planning authority does and on the Lead Local Flood Authority set out how the two duties differ.

North Somerset Council and Bath and North East Somerset Council are separate unitary councils with their own plans and drainage teams. Their pages often rank for Somerset searches, but none of their requirements apply to a site in the Somerset Council area.

Somerset Council's Local Plan flood and drainage policies, district by district

Until the new Somerset Local Plan is adopted, the policy that governs flood risk on a Somerset application depends on the former district: a scheme in Frome answers to Mendip's plan, one in Bridgwater to Sedgemoor's, one in Yeovil to South Somerset's, one in Taunton to the Taunton Deane Core Strategy and one in Minehead to the West Somerset plan. The council lists each plan on its adopted Local Plans page. The table gives the flood and water policies in each, with the adopted date.

Requirements checked November 2026.

Mendip Policy DP23 (Managing Flood Risk): what it requires

Mendip Policy DP23 asks every development in the former Mendip district (Frome, Shepton Mallet, Wells, Glastonbury, Street) to follow a sequential approach, to be resilient where it is at risk, and to manage its own surface water. The adopted wording in the Mendip Local Plan Part I, adopted on 15 December 2014, is that *"All development will also be expected to incorporate appropriate water management measures to reduce surface water run-off and ensure that it does not increase flood risks elsewhere. This should include the use of sustainable urban drainage systems (SUDS)."*

The supporting text notes that significant flooding in Mendip is mainly caused by rivers overtopping their banks, with less severe flooding from surface water run-off and blocked drains and culverts. On the Levels and Moors, it adds, new development is strongly resisted. DP23 replaced Policy EN17 (Surface Water Run-off) of the 2002 Mendip Local Plan in December 2014. Officers expect the FRA to show that all sources have been looked at, using the Mendip SFRA (2020) and the Environment Agency's mapping. Our assessment works through the sources one at a time, and the surface water drainage strategy that goes with it shows runoff reduced below the existing figure where the site allows, since DP23 asks for a reduction.

Mendip Policy DP8 (Environmental Protection): the water quality test

Mendip Policy DP8 requires development to show it does not cause *"unacceptable adverse environmental impacts on: ... the quality of water resources, whether surface river or groundwater"*, which is why a Mendip drainage scheme is judged on treatment as well as attenuation. Groundwater source protection zones are common on the limestone of the Mendip Hills. We set out a treatment train in the drainage strategy, sized to the pollution hazard of the land use, and flag any source protection zone that affects whether infiltration is acceptable.

Sedgemoor Policy D1 (Flood Risk and Surface Water Management): the sequential test and betterment

Sedgemoor Policy D1 governs flood risk in the former Sedgemoor district (Bridgwater, Burnham-on-Sea, Highbridge, Cheddar) and it settles the sequential test for many sites before any search of alternatives begins. The Sedgemoor Local Plan 2011-2032, adopted on 20 February 2019, says *"the Sequential Test will be considered to be passed for proposals located within identified settlement boundaries"*, and that outside them the area of search is the whole former district unless the development has a specific locational need.

On drainage, D1 says *"Proposals should seek to reduce flood risk overall through creation of multi-functional green infrastructure and sustainable drainage systems. Betterment will be sought particularly where there are known flooding issues."* It expects SuDS on all major development, including sites in Flood Zone 1, and requires watercourses to stay accessible for maintenance. That is an aim for betterment, not a fixed reduction: some summaries describe D1 as requiring an overall reduction in flood risk at every site, which overstates the adopted text. Even inside a settlement boundary the FRA still has to show the scheme is safe for its lifetime, including residual risk behind the Parrett defences and safe access and egress, and that is where our Sedgemoor assessments put most of their effort.

South Somerset Policy EQ1 (Addressing Climate Change in South Somerset): a district-wide area of search

South Somerset Policy EQ1 is a climate change policy, and it is also where the flood risk test sits for Yeovil, Chard, Crewkerne, Ilminster and Wincanton. The South Somerset Local Plan 2006-2028, adopted in March 2015, says *"The area of search to which the Sequential Test will apply will be South Somerset wide, unless adequately justified otherwise in relation to the circumstances of the proposal"*, and that development should *"reduce and manage the impact of flood risk by incorporating Sustainable Drainage Systems"*.

A district-wide default is a large area of search for a small scheme. NPPF policy F5 says the area should not be greater than the anticipated catchment of the development, and the Planning Practice Guidance says a non-major housing scheme's area of search would not usually extend beyond its town, or its village and immediate neighbouring settlements. The report therefore sets out the area used and the reasons for it, tied to the proposal (a farm or business extension, or a use that serves a defined catchment). The plan's supporting text notes that surface water is an issue at many of the main settlements, Yeovil in particular. Our sequential test reports set out the area of search and the reasons for it, so the officer can apply EQ1 without having to rebuild the evidence.

Taunton Deane Policy CP8 (Environment): where the Taunton flood test sits

Taunton Deane Policy CP8 contains the flood risk and runoff test for Taunton, Wellington and the rest of the former Taunton Deane borough, even though its title is Environment. The Taunton Deane Core Strategy 2011-2028, adopted on 11 September 2012, says *"Development sites will need to ensure that flood risk is not exacerbated from increased surface water flows by ensuring that existing greenfield rates and volumes are not increased off-site through the adoption of multi-functional SUDS."*

CP8 also directs development away from land at fluvial or other flood risk using the Level 2 SFRA, and expects sites to contribute to a strategic flood attenuation scheme for the Taunton urban area. Holding the peak rate down does not satisfy CP8 if the total volume leaving the site still rises, so a scheme that adds roofs and roads to a field needs storage or infiltration for the extra volume as well as a flow control. Our drainage strategies for Taunton Deane sites report both, and test the rate against the 2 litres per second per hectare limit that the Somerset standards set for the River Tone catchment.

Taunton Deane Policy CP1 (Climate Change): the cross-reference to CP8

Taunton Deane Policy CP1 asks every proposal to show how climate change has been addressed, and its clause (f) brings flood risk in by reference: *"The adoption of the sequential approach and exceptions test to flood risk in accordance with Policy CP8 (Environment) and incorporation of measures in design and construction to reduce the effects of flooding."* CP1 is often quoted as the Taunton flood policy, but the operative text is in CP8, and an FRA that cites only CP1 leaves the runoff test unanswered. A report from us cites both policies and states the climate change allowances used. The old Taunton Deane Local Plan Policy EN29 (Flooding due to development) expired by Secretary of State direction in November 2007, and Policy EN28 (Development and flood risk) was replaced by CP8 when the Core Strategy was adopted in September 2012.

West Somerset Policy CC2 (Flood Risk Management): Minehead, Watchet and Williton

West Somerset Policy CC2 applies the sequential and exception tests to the former West Somerset district outside Exmoor National Park, and asks development to help with existing flooding where it can. The West Somerset Local Plan to 2032, adopted on 23 November 2016, says *"Development must be designed to mitigate any adverse flooding impact which would arise from its implementation, and where possible should contribute towards the resolution of existing flooding issues."* Along the coast the FRA has to deal with tidal and wave overtopping risk as well as the rivers and surface water, and we cover each source in turn.

The new Somerset Local Plan: what changes, and when

Somerset Council is preparing a single Somerset Local Plan to 2045 under the new plan-making system. Its timetable (page updated 1 September 2026) shows the scoping consultation ran from 19 June to 9 August 2026 and Gateway 1 was passed on 30 October 2026. Consultation on proposed content is due from 10 September 2027, the proposed plan from 10 March 2028, submission on 8 September 2028 and adoption on 16 March 2029. No draft flood or drainage policy has been published yet, so DP23, D1, EQ1, CP8, CP1 and CC2 remain the tests for every application decided before then.

What a drainage strategy in Somerset must show: the local SuDS standards

A drainage strategy in Somerset is read against the Somerset Local SuDS Design Standards, published by the council as LLFA, with funding from the Somerset Rivers Authority (standards document dated April 2023). They strengthen the national non-statutory technical standards and the West of England Sustainable Drainage Developer Guide, which the council's sustainable drainage page still names. Where Somerset sets a number, the Somerset number applies, and several are stricter than the national ones.

The LLFA encourages a surface water drainage strategy with a statement showing how each of the six areas in the standards has been met, using its minor or major applications sustainable drainage checklist. Our surface water drainage strategy work starts from the SuDS hierarchy, sets out the discharge route, and answers the checklist standard by standard. Where infiltration is in question, our free geology and ground conditions map and BRE 365 infiltration rate calculator give an early view before trial pits are dug, and the drainage calculators cover the greenfield and storage figures.

On the Levels and Moors, the Axe Brue and Parrett Internal Drainage Boards add a separate consent. Through the Somerset Drainage Boards Consortium, they consent works that obstruct or alter flow, new outfalls and culverts, works that introduce flow into a board watercourse, and buildings, fences or tracks within 9 metres of one, with a 60-day consultation once an application is complete. Planning permission does not cover it, so the outfall is agreed with the board early. Behind the local figures sit the 2025 National Standards for sustainable drainage, which NPPF policy F8 now points applicants to.

Flood risk assessment, sequential test or drainage strategy: what triggers each in Somerset

A flood risk assessment, a sequential or exception test and a drainage strategy are three separate reports: the first asks whether the site is safe, the second whether the development should be there at all, and the third where the surface water goes. The triggers below come from the Somerset Council Local Validation Checklist, the five district policies and the LLFA's standards. You can screen a site's flood zone on our free flood risk map, and our guide to when you need a flood risk assessment covers the national triggers.

Minor applications are not given a fixed drainage requirement in the checklist: a foul and surface water drainage assessment is asked for site by site. An application that arrives without a required item may not be validated, which is the delay our note on why applications are invalidated for flood risk and drainage describes. Where a drainage strategy is thin, the LLFA usually objects rather than leaving it to a condition, as covered in our piece on an LLFA objection to a planning application.

Somerset's SFRAs and the validation checklist

Somerset Council has a county-wide Level 1 SFRA (JBA Consulting, final report February 2026), listed on the Somerset Local Plan evidence base page (updated 29 September 2026), with a Level 2 SFRA still to come. The new Level 1 SFRA states that it replaces the SFRAs produced by the former district councils and will be used in decision making. The district policies still name their own SFRAs, which remain listed on the council's Local Plan evidence base and monitoring page: the Mendip SFRA (2020); the Sedgemoor Level 1 (October 2015) and Level 2 (January 2009, with a 2019 addendum); the joint South Somerset and Somerset West and Taunton Level 1 (July 2019); and the West Somerset Level 2 (October 2010).

That evidence page still says a county Level 1 is aimed for the end of 2025, which the newer evidence base page has overtaken. A site-specific assessment uses the SFRA for the strategic picture (climate change extents, surface water and groundwater mapping, functional floodplain) and then tests the risk at the site itself. Our explainer on Strategic Flood Risk Assessments covers how they feed the sequential test.

The Somerset Council Local Validation Checklist, published on 1 April 2025, sets the validation requirements across the whole council area. It was signed on 18 March 2025 after consultation, and it runs until 31 March 2027 unless reviewed sooner. Several superseded district checklists still rank in search, so check that the agent is working from the 2025 version. The current checklist asks for an FRA in Flood Zones 2 and 3, within 8 metres of a main river and on sites of 1 hectare or more in Flood Zone 1. It refers applicants to the national and local flood risk standing advice, and offers a householder flood risk form.

National policy in Somerset: NPPF Chapter 18

Somerset's district policies sit under the August 2026 National Planning Policy Framework, published on 17 August 2026, whose Chapter 18 covers managing flood risk and coastal change in policies F1 to F9. Policy F4 sets when a site-specific flood risk assessment is needed, F5 and F6 the sequential and exception tests, and F8 the 2025 National Standards for sustainable drainage. Where a 2012 to 2019 district policy and the 2026 Framework differ, the officer weighs the Framework as a material consideration. Our NPPF guidance and our summary of the August 2026 NPPF flood risk changes explain what moved.

The Planning Practice Guidance on flood risk and coastal change, last updated on 17 September 2025, revised how the sequential test area of search and reasonably available sites are identified, as our note on the September 2025 PPG update explains. The test applies to risk from any source, so under NPPF policy F5 surface water risk alone can bring a Flood Zone 1 site into it. The Environment Agency climate change allowances set the peak rainfall and river flow uplifts, with housing assessed over at least 100 years; our guide to climate change allowances for planning works through them.

Flood risk across Somerset, in brief

Flood risk in Somerset changes from one district to the next. The Levels and Moors are a low basin drained by the Parrett, Tone, Brue, Axe and Yeo, where water is moved by gravity and pumps and can stand for weeks; the 2013 to 2014 Somerset Levels floods showed how long. On 27 January 2026 Somerset Council and its Local Resilience Forum partners declared a major incident on the Levels and Moors after Storm Chandra. The full physical picture is on our guide to flood risk assessment in Somerset.

In Bridgwater the tidal River Parrett is the main risk, and the Bridgwater Tidal Barrier, delivered by the Environment Agency and Somerset Council, is designed to protect about 11,300 homes and 1,500 businesses from tidal flooding once complete (Somerset Council's scheme page). Taunton combines river risk from the River Tone with surface water, the reason for the catchment's 2 litres per second per hectare limit. For Yeovil, the South Somerset plan cites the River Parrett catchment flood management plan's warning that higher-intensity summer storms overwhelming local sewers and smaller streams may become the town's main problem. The live river levels map shows the gauges on these rivers.

Our flood risk and drainage reports for Somerset Council applications

We prepare flood risk assessments and drainage strategies for applications to Somerset Council, and have taken outline applications through to no objection from the Environment Agency by limiting discharge to a main river to the greenfield runoff rate. The LLFA's drainage officers look closely at how runoff from access roads is held on site up to the exceedance event, and how attenuation under a carriageway affects road adoption, so that is the level our reports are written to. Each report below is a separate piece of work, and every one is overseen by a chartered consultant.

• Flood risk assessments. Every Somerset application in Flood Zone 2 or 3, or on a site of a hectare or more, needs a site-specific flood risk assessment under the validation checklist.
• Planning applications. Our flood risk assessment for planning answers the district policy that applies, whether DP23, D1, EQ1, CP8 or CC2, as well as NPPF Chapter 18.
• Buying a property. Where a search flags Levels, tidal or surface water risk on a Somerset home, a flood risk survey for property purchase looks at the building itself.
• Sites outside settlement boundaries. Sedgemoor D1 and South Somerset EQ1 each set a district-wide area of search, which our sequential and exception test reports define and justify.
• Major schemes. A Surface Water Drainage Assessment is a validation requirement for major applications, and our drainage strategy work covers both the foul and surface water routes.
• Greenfield-rate sites. The Somerset standards cap three design storms at greenfield and 2 litres per second per hectare in the Tone catchment, which a surface water drainage strategy has to evidence.
• Conditions after approval. Where the LLFA's comments become a pre-commencement condition, we prepare what is needed for discharge of drainage conditions.
• Ordinary watercourses on the Levels. Where the national maps leave an ordinary watercourse or rhyne unmodelled, flood modelling sets the design levels the FRA relies on.
• High groundwater. Standard L9 asks for winter groundwater monitoring before infiltration is accepted, which our groundwater flood risk assessment covers.
• Homes that have flooded. Properties flooded in recent winters can face higher premiums, and a flood risk assessment for insurance gives underwriters evidence for the building.

All of our Somerset work is quoted as a fixed fee, and our guide to flood risk assessment cost explains how the scope is set. Other councils' requirements are on our local authorities page.

Frequently asked questions about Somerset Council flood risk and drainage

Unda Consulting Limited prepares flood risk assessments, sequential and exception tests and drainage strategies for planning applications across England. To discuss a Somerset Council application, call 01293 214444 or email enquiries@unda.co.uk.