Planning Appeals 2026: Why Flood Risk and Drainage Must Be Right First Time

From 1 April 2026, the way planning appeals work in England changed, and the change lands hardest on anyone relying on flood risk or drainage evidence. Most appeals now run through a streamlined written procedure, and the Planning Inspectorate will generally only consider what was already in front of the council when it refused the application. In plain terms, the appeal is no longer the place to fix a weak submission. What you put in on day one is, in practice, what the appeal is judged on.

For flood risk and drainage, the 2026 rules remove a second chance that applications have quietly relied on for years.

Emma Jeffery, Senior Consultant at Unda, calls it a structural change rather than a procedural tidy-up. The reform is set out in the Town and Country Planning (Appeals) (Written Representations Procedure) (England) (Amendment and Saving Provision) Regulations 2026 (SI 2026/122) and explained in the Planning Inspectorate’s procedural guide, published in February 2026. For flood risk and drainage work, it is the biggest change in years to how, and when, risk has to be resolved in a planning application.

What changed in the planning appeals process on 1 April 2026?

The core change is simple to state: the standard route for most refused applications is now a faster, document-only written procedure, and new evidence is largely shut out. The reforms apply to Section 78 appeals against decisions on applications dated on or after 1 April 2026, so they phase in as those applications work through the system rather than switching everything over on one day.

• Written representations by default. Most appeals now begin under the streamlined written procedure. The Inspectorate can still escalate a case to a hearing or inquiry, but that is the exception, not the starting point.
• The evidence base is fixed at application stage. Inspectors primarily consider the material that was before the Local Planning Authority when it decided. New technical reports submitted for the appeal are generally not accepted.
• Little room for scheme changes. Amended drawings, revised layouts or reworked mitigation fall outside the standard written procedure. The route for a changed scheme is a fresh application.
• Faster decisions, higher stakes. The process is quicker, but the trade-off is that an under-evidenced application has far less chance of being rescued once it is refused.

The Inspectorate decides which procedure each appeal follows, as soon as practicable after a valid appeal is received, and keeps that choice under review. Parties can ask a senior officer to review the procedure if it differs from what they wanted, but the direction of travel is clear: the evidence you submit with the application is the evidence your appeal stands on.

What can the Planning Inspectorate now consider at appeal?

Under the written procedure, the Inspector looks at a closed set of documents: the original application and its supporting evidence, the officer report and committee minutes, the decision notice and its reasons, the appeal form, and the council’s questionnaire. An appellant cannot simply add a stronger flood risk assessment or a revised drainage strategy at appeal to cure the reason for refusal. The graphic below shows what is automatically in front of the Inspector, and what you can no longer bolt on afterwards.

This is why the reform reads so differently for technical disciplines than it does for, say, a design or amenity argument that can be made in writing from the existing drawings. A flood risk or drainage objection is usually answered with a document — and that document now has to exist, and be right, before the council decides.

What counts as a “material change in circumstance”?

There are narrow exceptions. If something material has genuinely changed since the council’s decision, the Inspectorate may accept new evidence — but the categories are tightly drawn and rarely rescue an evidence gap that existed all along. They are about the world moving on, not about an applicant catching up.

Note what is missing from that list: “we have now commissioned the modelling we should have done first time.” Finishing the technical work after refusal is not a material change in circumstance. As Emma puts it, the practical test is unforgiving.

Why do flood risk and drainage decide so many of these appeals?

Because they are, disproportionately, where applications are found wanting. They are also the kind of objection that used to be settled with a better report at appeal, which is exactly what the new rules prevent. Flood risk and surface water drainage are technical, evidence-led judgements. When an application is thin on either, the refusal reason points at a missing or inadequate document, and under the new rules that document can no longer be produced late.

Flood risk and drainage are often the areas where applications fall short — and now the areas where falling short is hardest to recover.

The building blocks matter more than ever at submission. A site in Flood Zone 2 or 3, or one flagged on the Flood Map for Planning, needs a complete, policy-compliant flood risk assessment for planning in the application itself. The direction of national policy reinforces this: both the September 2025 PPG update and the revised NPPF push flood risk further up the order of decision-making, not down it. And an Environment Agency objection on flood risk is now materially harder to overturn, because the usual way of answering one (new modelling or a revised assessment at appeal) is the very thing the written procedure keeps out.

Can sequential and exception tests still be reworked at appeal?

Not in the way they sometimes were. The sequential and exception tests are central to decisions in flood risk areas, and they turn on evidence assembled before determination: the alternative sites considered, the search area, and the flood risk information behind them. If that case is not properly made at application stage, the appeal offers little room to build it retrospectively.

Appeal decisions still turn on the planning balance, and a failed sequential test is not always fatal — recent cases such as the Yatton appeal show inspectors weighing flood risk against wider benefits. But the safest position by far is a test that was evidenced correctly the first time. A robust, properly reasoned sequential and exception test submitted with the application is now doing double duty: winning the decision, and protecting the appeal if it comes.

What do drainage strategies need to show at submission?

A surface water drainage strategy now has to satisfy the Lead Local Flood Authority and the planning officer at the point it goes in, not after a refusal. Lead Local Flood Authorities are statutory consultees on surface water drainage for major development, and the way LPAs assess flood risk and SuDS leaves little tolerance for a strategy that is light on design justification.

• Policy compliance. The strategy should demonstrate the SuDS hierarchy has been followed and discharge rates are justified against the right standards.
• Site-specific evidence. Ground conditions, infiltration testing where relevant, and levels need to support the design rather than sit as assumptions.
• Enough detail to condition. Officers need a strategy they can reasonably attach a condition to — not a placeholder that leaves the principle of drainage unresolved.

Where a strategy is missing or too thin to validate, the application can stall before it is even determined. Our guide to the flood risk and drainage documents that get applications invalidated covers that failure mode in detail.

Refused on flood risk or drainage — do you appeal or resubmit?

This is now the decision that matters most after a refusal. If the reason for refusal is a genuine evidence gap in the flood risk assessment or drainage strategy, the appeal will not let you fill it, so a fresh application is usually the faster and safer route. The exception is where something material has genuinely changed since the decision. The flow below sets out the logic.

Resubmitting is not a defeat. A fresh application with the flood risk and drainage work done to standard is often quicker to a positive outcome than an appeal that is procedurally barred from considering the very evidence that would win it.

What does an “appeal-ready” application look like?

Appeal-ready simply means the application is built to stand on its own, so that if it is refused the appeal has real prospects on the papers that are already in the file. For flood risk and drainage, that comes down to a short, practical sequence.

1. Screen the site early. Establish flood zone, surface water risk and any critical drainage constraints before the layout is fixed, so risk shapes the scheme rather than fighting it.
2. Commission the flood risk assessment up front. A complete, policy-compliant FRA at submission — not a screening note to be upgraded later.
3. Evidence the sequential and exception tests properly. Document the alternative sites, search area and reasoning so the case is on the file from the start.
4. Submit a drainage strategy the LLFA can accept. SuDS hierarchy followed, discharge rates justified, ground conditions tested where needed.
5. Engage the consultees before you submit. Resolve likely Environment Agency and LLFA concerns while you can still change the evidence, not after refusal.

Get in touch with Unda if you want flood risk and drainage evidence that is built to survive first contact with the council, whether that is a flood risk assessment for planning, a sequential and exception test, or a surface water drainage strategy. Under the 2026 rules, that early investment is what protects the whole application.

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