LLFA Objected to Your Drainage Strategy? Here's What to Do

A Lead Local Flood Authority objection to your drainage strategy is a common but frustrating obstacle in the planning process. Since April 2015, LLFAs have been statutory consultees on major planning applications for surface water drainage in England, and their objections carry significant weight with local planning authorities. An unresolved LLFA objection will, in most cases, prevent the LPA from granting planning permission.

The good news is that LLFA objections are almost always resolvable. They typically stem from missing information, insufficient evidence, or technical deficiencies in the drainage strategy — all of which can be addressed with the right approach. This guide explains why LLFAs object, what they expect to see, and how to get the objection withdrawn.

Why LLFAs Object: The Common Reasons

Understanding why the LLFA has objected is the essential first step. While every objection is different, most fall into a handful of recurring categories.

Insufficient Evidence of the SuDS Hierarchy

The most common reason for LLFA objection is a failure to demonstrate that the drainage strategy follows the SuDS hierarchy. The hierarchy, established in the National Planning Policy Framework and Planning Practice Guidance, requires surface water to be managed using sustainable drainage systems in the following order of preference:

1. Infiltration to ground (soakaways, permeable paving, infiltration basins)
2. Discharge to a surface water body (river, stream, ditch, pond)
3. Discharge to a surface water sewer
4. Discharge to a combined sewer (last resort only)

LLFAs expect the applicant to demonstrate that each option higher in the hierarchy has been investigated and, if dismissed, that clear evidence supports the dismissal. A drainage strategy that proposes connection to a sewer without demonstrating why infiltration is not feasible will almost certainly be objected to.

The key evidence for dismissing infiltration is BRE 365 soakage testing carried out at the site. Desktop assessments, geological maps, or assumptions based on nearby sites are not sufficient. If infiltration testing has not been carried out, the LLFA will require it before withdrawing their objection.

No Maintenance and Management Plan

LLFAs increasingly require a maintenance and management plan as part of the drainage strategy submission, not just as a condition discharge matter. The plan must identify:

• All SuDS features and their maintenance requirements
• The party responsible for long-term maintenance (management company, adopting body, or landowner)
• Maintenance tasks, frequencies, and estimated costs
• Inspection and monitoring arrangements
• Arrangements for funding the maintenance in perpetuity

A drainage strategy that relies on SuDS features but provides no credible plan for maintaining them over the lifetime of the development will be objected to. LLFAs have seen too many SuDS schemes fail because maintenance was not properly secured.

Inadequate Climate Change Allowances

Surface water drainage designs must account for climate change over the lifetime of the development. The Environment Agency’s climate change allowances for peak rainfall intensity are the standard reference, and they are regularly updated. As of 2026, the allowances for most of England require a significant uplift to peak rainfall — typically between 20% and 45% depending on the location, the epoch, and whether the central or upper end estimate is applied.

LLFAs will object if:

• Climate change allowances have not been applied at all
• Outdated allowances have been used (a common issue when drainage strategies are prepared months or years before submission)
• The allowance applied is too low for the vulnerability classification of the development (residential development generally requires the upper end allowance)
• The drainage calculations do not demonstrate no flooding for the 1 in 100 year plus climate change event

No Exceedance Routing

Every drainage system has a capacity limit. The LLFA needs to see evidence of what happens when storms exceed the design capacity — where does the water go? A drainage strategy that does not address exceedance events will be objected to.

The exceedance strategy should demonstrate that overland flow paths direct surface water away from buildings and towards areas of low consequence (open space, roads, car parks) rather than into properties or critical infrastructure. This typically requires a site plan showing exceedance flow routes, with levels demonstrating that water flows in the intended direction.

Missing Infiltration Testing

This overlaps with the SuDS hierarchy issue but deserves emphasis because it is the single most common deficiency we encounter. If the drainage strategy proposes infiltration, the LLFA will require BRE 365 testing to confirm that the ground conditions support it. If the strategy dismisses infiltration, the LLFA will require BRE 365 testing to confirm that it is not feasible.

Either way, BRE 365 testing is effectively mandatory for any site where infiltration might be viable. The testing must be carried out at the proposed locations and depths of the SuDS features, in accordance with BRE Digest 365 methodology. Winter testing is preferred because it captures worst-case groundwater conditions.

The LLFA Pre-Application Service

Many LLFAs offer a pre-application advice service for drainage strategies. This is one of the most valuable and underused services available to developers and their consultants.

The pre-application service allows you to submit a draft drainage strategy to the LLFA for informal review before the planning application is submitted. The LLFA will provide written comments identifying any issues or deficiencies, giving you the opportunity to address them before they become formal objections.

The benefits are significant:

• Avoid formal objections. Addressing the LLFA’s concerns before submission dramatically reduces the risk of objection.
• Understand local requirements. Each LLFA has its own preferences and requirements beyond the national guidance. Pre-application advice reveals these early.
• Agree design parameters. Discharge rates, climate change allowances, acceptable SuDS features, and maintenance arrangements can all be agreed in principle before detailed design.
• Save time. Resolving issues pre-application is faster than resolving them through formal objection and resubmission cycles.

Pre-application fees vary between LLFAs, typically ranging from a few hundred to around a thousand pounds for major developments. Given the time and cost of resolving formal objections, this is almost always money well spent.

What a Revised Drainage Strategy Needs to Include

If the LLFA has objected and you need to prepare a revised drainage strategy, the submission should comprehensively address every point raised in the objection. A typical revised strategy for a major development includes:

Technical Reports and Calculations

• Updated drainage strategy report addressing each LLFA concern point by point
• BRE 365 infiltration test results (if not previously provided or if additional testing was requested)
• MicroDrainage or InfoDrainage calculations demonstrating no flooding for all events up to the 1 in 100 year plus climate change storm, across the full range of storm durations
• Half-drain time calculations for infiltration features (must be less than 24 hours in most LLFA jurisdictions)
• Water quality assessment using the Simple Index Approach from the CIRIA SuDS Manual (C753) where required

Drawings and Plans

• Drainage layout plan showing all pipes, manholes, SuDS features, flow control devices, and connections
• Exceedance flow route plan with spot levels demonstrating flow direction
• SuDS feature details — cross-sections and construction details for each type of SuDS feature proposed
• Contributing area plan showing how the site is divided into drainage catchments

Supporting Documents

• Maintenance and management plan with responsible party, tasks, frequencies, and funding mechanism
• Greenfield runoff rate calculations (using the IH124, FEH, or HR Wallingford methods as required by the LLFA)
• Correspondence with the water company if sewer connection is proposed (confirmation of point of connection, permitted discharge rate, and capacity)

LLFA vs Water Company: Understanding the Roles

A common source of confusion is the distinction between the LLFA’s role and the water company’s role. They are separate consultees with different responsibilities:

The LLFA is responsible for surface water flood risk management. It reviews the drainage strategy to ensure that surface water is managed sustainably and does not increase flood risk. The LLFA’s concerns relate to SuDS design, attenuation, discharge rates, exceedance, and maintenance.

The water company (Thames Water, United Utilities, Severn Trent, etc.) is responsible for the public sewer network. It reviews proposals for connection to its sewers and assesses whether the network has capacity to accept the proposed discharge. The water company’s concerns relate to sewer capacity, connection points, flow rates, and adoption arrangements.

Satisfying the LLFA does not necessarily satisfy the water company, and vice versa. A drainage strategy that the LLFA considers acceptable because it includes adequate SuDS and attenuation may still be objected to by the water company because the downstream sewer network lacks capacity. Both consultees must be satisfied before the LPA will approve the drainage strategy.

LLFA Response Timescales

The statutory consultation period for LLFA responses is 21 days. However, in practice, many LLFAs take significantly longer — 4 to 6 weeks is common, and some LLFAs with heavy caseloads can take 8 weeks or more.

When revised evidence is submitted following an objection, the LPA reconsults the LLFA, triggering a fresh consultation period. Allow at least 4 to 6 weeks for the LLFA to review a revised drainage strategy, and longer if the revision involves significant changes or new modelling.

If the LLFA does not respond within the statutory period, the LPA can technically proceed to determine the application without the LLFA’s input. In practice, most LPAs are reluctant to do so on drainage matters, preferring to wait for the LLFA’s response rather than risk approving an inadequate drainage scheme.

Schedule 3 and the SAB Regime

The Flood and Water Management Act 2010 (FWMA 2010) introduced Schedule 3, which establishes a SuDS Approving Body (SAB) regime separate from the planning system. Under Schedule 3, surface water drainage for new developments must be approved by the SAB (typically the county or unitary council) before construction can begin, and the drainage must meet national standards for sustainable drainage.

Wales: Schedule 3 in Force

Schedule 3 has been in force in Wales since 7 January 2019. All new developments in Wales with drainage implications require SAB approval in addition to planning permission. The SAB approval process is separate from the planning application — it is a standalone consent with its own application form, fee, and determination timeline. The SAB assesses the drainage design against the Welsh national standards for SuDS, which are generally more demanding than the English planning guidance.

For developments in Wales, the LLFA’s role in the planning process is supplemented (and in some respects superseded) by the SAB. The drainage strategy must satisfy both the planning system and the SAB regime.

England: Schedule 3 Commencement Expected

The UK Government has confirmed its intention to commence Schedule 3 in England. The commencement date and the detail of how the English SAB regime will operate are still being finalised, but the direction of travel is clear: surface water drainage for new developments will need to meet mandatory national standards enforced by a SAB, in addition to the existing planning requirements.

Developers and consultants working on projects with long lead times should be aware that the regulatory landscape for surface water drainage in England is likely to change significantly within the next few years. Designing drainage strategies that already meet or exceed the expected national standards is prudent forward planning.

For more detail on SuDS design principles, see our guide to SuDS design.

When to Redesign vs When to Provide Additional Evidence

Not every LLFA objection requires a complete redesign of the drainage strategy. In many cases, the objection can be resolved by providing additional evidence to support the existing design.

Provide Additional Evidence When:

• The design is sound but the supporting documentation is incomplete (e.g., missing infiltration test results, absent maintenance plan, no exceedance routing plan)
• The LLFA has requested specific additional calculations or assessments that do not affect the fundamental design
• Climate change allowances need updating but the design has sufficient capacity to accommodate the increase
• The LLFA wants confirmation of greenfield runoff rates or discharge rate agreements

Redesign When:

• The fundamental drainage approach is not viable (e.g., infiltration was assumed but testing shows it is not feasible)
• The drainage system floods during the design storm and cannot be upsized within the available space
• The LLFA requires above-ground SuDS features that were not included in the original design
• The water company has confirmed that the proposed sewer connection cannot be accommodated
• The site layout has changed and the drainage network no longer serves the development effectively

A pragmatic assessment of whether the existing design can be saved with additional evidence, or whether a fresh approach is needed, saves time and money. When in doubt, discuss the options with the LLFA before committing to a course of action.

For a comprehensive overview of what a drainage strategy should contain, see our drainage strategy guide.

How Aegaea Can Help

Aegaea’s surface water drainage team specialises in resolving LLFA objections. We review the LLFA’s concerns, assess whether the existing design can be supported with additional evidence or requires redesign, and prepare the technical submissions needed to get the objection withdrawn.

We have resolved LLFA objections across England and Wales, including a housing development in Bristol where the LLFA rejected the original drainage strategy outright. We redesigned the scheme with an above-ground SuDS management train, provided comprehensive BRE 365 evidence, and secured LLFA approval within a single consultation round.

If your LLFA has objected to your drainage strategy, contact us for a no-obligation review of the objection and a clear plan for resolving it.