Flood risk assessments, local authority by local authority

Unda provides flood risk assessments and drainage strategies for sites across England and Wales, and a great deal of what a planning application needs is set locally — by the authority that will determine it. For the councils we work in most we have published a dedicated guide — how that authority approaches flood risk and drainage, the Local Plan policies and SFRA behind it, the validation requirements, and what all of that means for a planning application in its area.

Whether your site falls under a London borough, a district or county council in the South East, or an authority further afield, understanding what your specific planning authority expects is where a credible application begins. Explore a published local authority guide below, or start a quote and one of our experienced flood risk consultants will talk through your site.

Flood risk requirements are local to the authority: two neighbouring councils can ask for very different things on the same catchment — a different SFRA, a different validation list and a different local drainage standard.

Find your local authority

Search a postcode, town or city to drop a pin on the map and open the local authority guide nearest to your site.

Browse local authority guides by region

Prefer to browse? The authorities below are grouped by region, and by the county each one sits within. Select a council for its full flood risk and planning guide, or a county to open our local area guides.

National flood risk policy guidance

Local requirements sit on top of national policy. Whichever authority determines your site, the starting point is the framework it applies — the NPPF in England, or TAN15 in Wales. Our plain-English guides explain what each requires and when it applies:

• NPPF flood risk guidance (England). When the August 2026 NPPF requires a flood risk assessment, Sequential Test or drainage strategy, and how local authorities apply it.
• TAN15 flood risk guidance (Wales). How TAN15 and the 2025 rules work — the Flood Map for Planning, Defended Zones, and when a Welsh site needs a Flood Consequence Assessment.

Flood risk assessments for every situation

• Flood risk assessment for planning. The site-specific report that satisfies the NPPF in England, or TAN15 in Wales, and shows your development is safe for its lifetime without increasing risk elsewhere.
• Flood consequence assessment (Wales). The TAN15 assessment for Welsh sites, demonstrating the consequences of flooding can be safely managed over the development’s lifetime.
• Flood risk survey for property purchase. An independent, property-specific survey for buyers and their advisers, going beyond the conveyancing search to assess the actual building.
• Flood risk assessment for insurance. Property-level evidence for brokers and underwriters where cover has been restricted, declined or priced on flood risk.
• Flood risk assessment for BREEAM. The assessment structured around BREEAM Pol 03 so a scheme keeps its flood and surface-water credits.
• Sequential and exception tests. The locational justification that a higher-risk site is the most appropriate available, prepared alongside the assessment.
• Groundwater flood risk. A defensible design groundwater level, tested against floor levels, basements and drainage.
• Flood modelling. 1D and 2D hydraulic modelling for sites where national mapping doesn’t reflect how water actually behaves on the ground.
• Surface-water drainage strategy (SuDS). A scheme that manages runoff to the local SuDS standard, following the four pillars of SuDS and the drainage hierarchy.
• Discharge of drainage conditions. The detailed design that discharges a pre-commencement or pre-occupation drainage condition on a permission.