Common Flood Risk Planning Conditions Explained
A practical guide to the most common flood risk and drainage planning conditions — what each requires, when they apply, and how to discharge them efficiently.
Securing planning permission is only the beginning. For developments in areas of flood risk — and for most major developments regardless of flood zone — the planning permission will be subject to conditions requiring further details of flood risk mitigation, drainage design, and water management to be submitted and approved before work can begin or before the development is occupied.
These conditions are a normal part of the planning process, but they catch many developers off guard. Misunderstanding what a condition requires, or failing to discharge it before the relevant trigger point, can halt construction, delay occupation, and in the worst cases lead to enforcement action.
This guide catalogues the most common flood risk and drainage planning conditions, explains what each requires for discharge, and sets out practical advice for managing conditions efficiently.
The Eight Most Common Flood Risk and Drainage Conditions
1. Finished Floor Level (FFL) Condition
What it requires: Confirmation that all finished floor levels will be set at a specified height above the design flood level — typically 300mm above the 1% AEP flood level including climate change allowances for commercial development, or 600mm above for residential development.
Trigger: Pre-commencement. Floor levels are fundamental to structural design and cannot be retrospectively altered.
Discharge evidence: A technical note cross-referencing the approved flood risk assessment, confirming the design flood level (with climate change allowance), the required freeboard, and the resulting minimum FFL. Include a drawing showing the proposed FFLs on a site plan and cross-sections.
2. Compensatory Flood Storage Condition
What it requires: Where development displaces floodplain storage, compensatory storage must be provided on a volume-for-volume and level-for-level basis. Volume-for-volume means the same volume of storage removed must be created elsewhere on site. Level-for-level means the compensation must be at the same elevation as the storage lost — not simply a hole in the ground at a different level.
Trigger: Pre-commencement. Compensatory storage areas must be excavated before the development that displaces floodplain storage is constructed.
Discharge evidence: Engineering drawings showing existing and proposed ground levels within the floodplain, cut-and-fill calculations demonstrating volume-for-volume and level-for-level compensation, and a phasing plan. The Environment Agency is typically consulted on discharge.
3. Surface Water Drainage Scheme Condition
What it requires: A comprehensive drainage strategy developing the outline drainage principles approved at planning stage into a detailed, constructable design. This must include pipe network calculations, attenuation storage sizing for the 1 in 100 year event plus climate change, SuDS details, pollution control measures, and confirmation of discharge rates and destinations.
Trigger: Pre-commencement. Drainage infrastructure is typically one of the first elements installed on site.
Discharge evidence: Detailed drainage layout drawings, pipe schedules, hydraulic calculations, SuDS component details (permeable paving specifications, swale cross-sections, attenuation tank details), exceedance flow routes, and a maintenance plan. The Lead Local Flood Authority (LLFA) is the statutory consultee for surface water drainage on major developments.
4. Flood Warning and Evacuation Plan (FWEP) Condition
What it requires: A site-specific plan setting out how occupants will be warned of flooding, what actions they should take, and how safe evacuation will be achieved. The plan must include registration with the EA Flood Warning Service, identification of safe access and egress routes, designation of safe refuge areas if evacuation is not possible, and assignment of responsibilities.
Trigger: Pre-occupation. The FWEP must be in place before the development is first occupied but does not need to be discharged before construction begins.
Discharge evidence: The FWEP document addressing flood warning lead times, trigger levels, evacuation routes (assessed for flood depth and hazard), refuge areas, roles and responsibilities, and maintenance arrangements. Note that the Environment Agency does not approve FWEPs — this is the LPA’s responsibility.
5. No Development in Flood Zone Condition
What it requires: Restricts the location of buildings to areas outside Flood Zone 3. Common on larger sites straddling flood zone boundaries, where permission is granted on the basis that built development is confined to lower-risk areas while Flood Zone 3 areas are used for open space, landscaping, or flood storage.
Trigger: Ongoing. This restrictive condition applies throughout the life of the development and does not require formal discharge.
Discharge evidence: While no formal discharge is required, maintaining a clear audit trail is prudent — annotated site plans showing building footprints relative to the Flood Zone 3 boundary. Any ambiguity should be resolved with reference to the approved FRA and hydraulic modelling.
6. SuDS Maintenance Condition
What it requires: A detailed maintenance schedule for all SuDS components, together with confirmation of the body responsible for ongoing maintenance. For residential developments, this is typically a management company; for commercial developments, the site owner. The plan must cover routine maintenance (clearing inlets, mowing swales), reactive maintenance (repairing damage), and long-term renewal (replacing filter media, re-laying permeable paving).
Trigger: Pre-occupation. SuDS must be installed and maintenance arrangements confirmed before occupation.
Discharge evidence: A maintenance manual for each SuDS component, a maintenance schedule with frequencies, identification of the responsible management body with confirmation of their acceptance, and details of funding arrangements. The LLFA will often want to see this evidence.
7. Foul Drainage Condition
What it requires: Confirmation of how foul water will be managed. For developments connecting to the public sewer, this means confirmation of the connection point, sewer capacity assessment, and details of any on-site pumping stations. For off-mains developments, this means details of a package treatment plant or septic tank, including EA permit requirements.
Trigger: Pre-commencement. Foul drainage infrastructure is installed early and must be coordinated with surface water drainage.
Discharge evidence: Foul drainage layout drawings, confirmation of sewer connection (with water company agreement) or private treatment details (with EA permit or General Binding Rules compliance), and capacity calculations.
8. Flood Resilience Measures Condition
What it requires: Details of how the building fabric below the design flood level will resist water ingress and facilitate rapid recovery after flooding. Typical measures include water-resistant wall finishes (closed-cell insulation, cement render rather than gypsum plaster), raised electrical sockets, non-return valves on drainage connections, and flood-resistant doors and airbrick covers.
Trigger: Pre-commencement. These measures affect material specifications and construction methods, so must be incorporated from the outset.
Discharge evidence: A flood resilience specification listing measures to be incorporated, keyed to floor plans showing which areas are below the design flood level. Reference to CIRIA C790 and the ODPM/Defra flood resilience guidance strengthens the submission.
Pre-Commencement, Pre-Occupation, and Ongoing Conditions
Understanding the trigger point for each condition is critical to programme management.
Pre-commencement conditions must be discharged before any construction work begins on site. Starting work without discharging a pre-commencement condition is a breach of the planning permission and can result in enforcement action.
Pre-occupation conditions must be discharged before the development is first occupied. Construction can proceed while the submissions are prepared, but the development cannot be used until they are approved.
Ongoing conditions impose restrictions that apply throughout the life of the development. They do not require formal discharge but must be complied with at all times.
The Tests for Lawful Planning Conditions
Planning conditions are not imposed arbitrarily. Paragraph 56 of the NPPF (2023 revision) sets out six tests that all planning conditions must meet. A condition must be:
- Necessary: the condition must be needed to make the development acceptable in planning terms
- Relevant to planning: the condition must relate to a legitimate planning consideration
- Relevant to the development: the condition must relate to the specific development being permitted
- Enforceable: the LPA must be able to enforce compliance with the condition
- Precise: the condition must be clear and unambiguous about what is required
- Reasonable: the condition must not be unduly onerous or place unreasonable burdens on the applicant
These tests apply to all planning conditions, including flood risk and drainage conditions. If a condition fails any of these tests, it is unlawful and can be challenged.
Challenging Unreasonable Conditions
If you believe a flood risk or drainage condition is unreasonable, there are several routes for challenge.
Negotiation at decision stage: The best time to address problematic conditions is before the decision notice is issued. If the LPA circulates draft conditions, review them carefully and raise concerns before the decision is made.
Section 73 application: A section 73 application (TCPA 1990) allows you to apply to vary or remove a condition on an existing planning permission. This is a well-established route for addressing conditions that are impractical or disproportionate.
Appeal: If the LPA refuses to vary or remove a condition, you can appeal to the Planning Inspectorate under section 78 of the TCPA 1990. The inspector will assess whether the condition meets the six tests.
Common Mistakes When Drafting and Discharging Conditions
Drafting Mistakes (by LPAs)
- Vague wording: Conditions that require “details of drainage” without specifying what those details must include are difficult to discharge because neither the applicant nor the discharging officer knows what constitutes a satisfactory submission
- Inappropriate triggers: Imposing a pre-commencement trigger on a condition that could reasonably be pre-occupation (such as a FWEP) unnecessarily delays the start of construction
- Duplicating EA requirements: Conditions that attempt to replicate Environment Agency permitting requirements (such as flood defence consent, now Environmental Permits) create confusion about which regime applies
Discharge Mistakes (by Applicants)
- Submitting too little: A one-page letter confirming finished floor levels, without drawings or cross-references to the approved FRA, is unlikely to satisfy the discharging officer. Provide comprehensive evidence that directly addresses every element of the condition
- Missing the trigger point: Starting construction before pre-commencement conditions are discharged is a breach of the planning permission. Monitor the conditions schedule carefully and ensure discharge applications are submitted (and approved) well before the trigger point
- Ignoring consultee requirements: The LPA will consult the EA and/or LLFA on discharge of drainage conditions. If those consultees have previously raised specific concerns, address them proactively in the discharge submission rather than waiting for another round of objections
Practical Tips
- Prepare a conditions tracker at the point of decision, listing every condition, its trigger point, the consultees, and the evidence required for discharge
- Submit discharge applications early — LPAs have eight weeks to determine discharge applications, and consultee responses can take four to six weeks within that period
- Engage with the EA and LLFA before submitting the discharge application. An informal pre-submission discussion can identify potential issues and significantly reduce the risk of refusal
- Cross-reference the approved FRA and drainage strategy in every discharge submission. The discharging officer needs to see that the detailed design is consistent with the principles approved at planning stage
How Aegaea Can Help
Aegaea discharges all flood risk and drainage condition types, from finished floor level confirmations to detailed surface water drainage designs and flood resilience specifications. We prepare discharge submissions that are comprehensive, technically robust, and designed to secure approval first time — avoiding the delays and costs of re-submission.
If you have planning conditions to discharge, or if you are preparing a planning application and want to ensure that conditions are workable from the outset, contact us to discuss your project.