How to Respond to Planning Officer Comments on Flood Risk and Drainage

Midway through the determination of a planning application, you receive a notification from the LPA portal: comments have been posted on your application. You find a series of concerns about flood risk and drainage from the case officer, the Environment Agency, and the Lead Local Flood Authority. The application is not refused — not yet — but the clock is ticking and the issues need to be addressed.

This scenario plays out on hundreds of applications every month across England and Wales. A well-structured, technically rigorous response resolves concerns and keeps the application moving toward approval. A vague or incomplete response invites further queries, delays determination, and risks refusal.

Understanding Who Is Commenting and Why

Comments on flood risk and drainage do not come from a single source. They originate from multiple consultees, each with a different remit. Understanding who is raising the issue helps you frame the right response.

The case officer assesses the application against local and national policy. Their flood risk comments typically relate to NPPF compliance (particularly Chapter 14 and the associated Planning Practice Guidance), the local plan, and supplementary planning documents. They may raise concerns about the Sequential Test, Exception Test, or overall policy compliance.

The Environment Agency is a statutory consultee on applications in Flood Zones 2 and 3. Their comments focus on fluvial and tidal flood risk, climate change allowances, safe access and egress, finished floor levels, compensatory storage, and the adequacy of the flood risk assessment. An EA objection carries substantial weight — LPAs are expected to refuse where the EA maintains an objection unless there are very strong reasons otherwise.

The Lead Local Flood Authority is a statutory consultee on major developments for surface water drainage. Their comments focus on the drainage strategy, including discharge rates, attenuation, SuDS hierarchy, infiltration testing, exceedance routing, and maintenance arrangements.

The highways authority may raise drainage concerns where the development affects highway drainage or proposes connections to the highway network.

Internal Drainage Boards, where they exist, are consulted on applications affecting watercourses within their district. Their comments typically relate to discharge consents and watercourse setbacks.

Common Concerns

While every application is different, certain concerns arise repeatedly.

Inadequate Sequential Test Evidence

The case officer has concluded the Sequential Test has not been adequately demonstrated — the search area was too narrow, alternatives were dismissed without justification, or the document was missing entirely. Since the September 2025 PPG update, the Sequential Test must consider all sources of flooding, not just fluvial and tidal risk.

Missing or Insufficient Climate Change Allowances

The EA commonly raises this. The FRA may have applied outdated allowances, used the central estimate where the upper end was required, or failed to include sensitivity testing. The EA’s allowances are updated periodically, and using the wrong vintage is a frequent error.

Unresolved EA Standing Advice Issues

For sites in Flood Zone 2 where the EA relies on standing advice, the case officer must apply that advice themselves. They may identify issues the applicant has not addressed — finished floor levels not demonstrated above the 1 in 100 year plus climate change level, or flood resilience measures not specified in detail.

No SuDS Maintenance Plan

The LLFA requires evidence that SuDS features will be maintained for the development’s lifetime. A strategy that proposes SuDS without a maintenance plan, responsible body, or funding mechanism will attract an objection. This is a requirement under the Flood and Water Management Act 2010 and is increasingly rigorously enforced.

Insufficient Exceedance Routing

What happens when a storm exceeds the drainage system’s design capacity? The LLFA expects the strategy to demonstrate that exceedance flows route safely away from buildings toward areas of low consequence. Many strategies focus on the design storm and ignore exceedance — a common ground for objection.

Missing Infiltration Testing

If infiltration has been dismissed without site-specific testing, the LLFA will raise this. BRE365 soakaway testing is expected where ground conditions are potentially suitable, and dismissing infiltration based on desk study alone is not accepted by most LLFAs.

How to Structure a Technical Response Memo

The most effective format is a structured memo addressing each concern point by point.

Format and Structure

1. Introduction: Identify the application, the consultee comments being addressed, and their date.
2. Summary table: List each concern, its source, and a brief response summary. This gives the reader an immediate overview.
3. Detailed responses: Address each concern with a numbered section mirroring the consultee’s structure. Quote or paraphrase the concern, then provide the response.
4. Supporting evidence: Append or reference additional technical evidence — calculations, drawings, modelling outputs, test results.

Key Principles

Address every point. Do not cherry-pick easy concerns and ignore difficult ones. Unanswered concerns will be treated as unresolved and may form the basis of a refusal reason.

Reference specific policy. Cite the specific NPPF paragraph, PPG section, or local plan policy. For example: “The FRA demonstrates compliance with paragraph 165 of the NPPF by providing a site-specific assessment that considers all sources of flooding and proposes mitigation to ensure the development is safe for its lifetime.” This demonstrates to the case officer that you understand the policy framework.

Provide evidence, not assertions. Statements like “the site is not at risk of flooding” without supporting data will not satisfy technical consultees. Provide the calculations, modelling outputs, or test results that support your position.

Be proportionate. If the LLFA has asked for confirmation of the discharge rate, a single paragraph with the figure and calculation reference suffices. Reserve detailed analysis for substantive issues.

Acknowledge where changes are needed. If a concern is valid and requires revision, say so clearly. Attempting to argue that a legitimate concern is unfounded undermines credibility on the points where your position is genuinely strong.

Response Memo vs Revised Documents

Getting this judgment right avoids wasted time in both directions.

A Response Memo Is Sufficient When:

• The concern is based on a misunderstanding (the consultee missed the climate change assessment in an appendix).
• The information is already in submitted documents but needs drawing out more clearly.
• A brief additional calculation, clarification, or policy reference addresses the point.
• The issue can be resolved by a planning condition (a detailed SuDS maintenance plan to be approved pre-construction).

Revised Documents Are Needed When:

• The FRA used incorrect climate change allowances or outdated data and the conclusions may change with correct inputs.
• The drainage strategy needs redesigning for a lower discharge rate, different SuDS features, or revised exceedance routing.
• The Sequential Test needs substantial expansion to address a wider search area or additional alternatives.
• The site layout needs changing to address flood risk (repositioning buildings, providing compensatory storage).

Where revised documents are needed, submit them as formal amendments to the application. This keeps determination on track and avoids the need for a fresh application.

Timeline Expectations for Reconsultation

Once the response is submitted, the LPA reconsults the relevant statutory bodies.

• EA reconsultation: Statutory 21-day period, though in practice allow 3 to 5 weeks, particularly for complex sites or updated modelling.
• LLFA reconsultation: Varies by authority — some respond within 2 weeks, others take 6 weeks or more.
• Case officer review: Once consultee responses arrive, allow 2 to 4 weeks for the officer to update their assessment.

In total, a round of reconsultation typically adds 6 to 10 weeks to the determination period. Factor this into your programme.

”Further Information Requested” vs “Reason for Refusal”

Understanding this distinction is critical.

Further information requested means the consultee is open to approval but needs additional evidence. This is a positive signal — the door is open. Respond promptly and thoroughly.

A reason for refusal means the consultee has concluded the application cannot be supported in its current form. If the EA issues a final objection, the case officer will typically include this as a recommended refusal reason. At this point, you must either withdraw and resubmit with a revised scheme or proceed to determination and potentially appeal.

The distinction is not always explicit. Phrases like “we are unable to support this application” or “in the absence of the following information, we would recommend refusal” are clear signals heading toward formal objection. Treat them with urgency.

Engaging Directly with Consultees

One of the most effective but underused strategies is engaging directly with the EA and LLFA outside the formal process.

Before submitting the response: Contact the consultee case officer directly to discuss concerns. This clarifies exactly what they need, avoids wasted effort, and sometimes allows informal agreement on a solution before committing it to writing.

After submitting the response: Follow up to confirm receipt and ask whether the response addresses concerns. Early warning of remaining issues lets you provide supplementary information before the reconsultation period expires.

This is particularly valuable with the EA, whose formal responses can be formulaic and may not precisely identify the specific concern. A brief phone call can save weeks of back-and-forth.

For an example of how effective consultee engagement resolved complex issues during determination, see our Capital Gate, Ilford case study.

Practical Tips

• Respond quickly. The statutory period continues to run. Delays eat into reconsultation time and risk refusal for non-determination.
• Copy the case officer on consultee correspondence. They need to know discussions are taking place.
• Use tracked changes for revised documents. Provide tracked and clean versions — this speeds consultee review significantly.
• Keep a log. Record all comments, responses, and correspondence. This is invaluable if the application proceeds to appeal, where you will need to demonstrate constructive engagement.

For a comprehensive overview of flood risk assessment requirements, see our guide to flood risk assessments.

How Aegaea Can Help

Responding to officer and consultee comments requires technical expertise, policy knowledge, and pragmatic judgment. Getting it right first time avoids costly delays and keeps your application on track.

At Aegaea, we write technical response memos, prepare revised flood risk assessments and drainage strategies, and engage directly with the EA, LLFA, and case officers on behalf of our clients. Whether you need a targeted response to a specific concern or a comprehensive revision of submitted documents, we provide the evidence that resolves comments and secures positive consultee responses.

If you have received comments on your application and need help responding, get in touch. We will review the comments, advise on the most effective response strategy, and prepare the technical evidence needed to keep your application moving toward approval.